CIS Debian Linux 13 Benchmark v1.0.0 - 12-16-2025 Internal Only - General Terms of Use Please see the below link for our current terms of use: https://www.cisecurity.org/cis-securesuite/cis-securesuite-membership-terms-of-use/ For information on referencing and/or citing CIS Benchmarks in 3rd party documentation (including using portions of Benchmark Recommendations) please contact CIS Legal (legalnotices@cisecurity.org) and request guidance on copyright usage. NOTE: It is NEVER acceptable to host a CIS Benchmark in ANY format (PDF, etc.) on a 3rd party (non-CIS owned) site. Page 1 Internal Only - General Table of Contents Terms of Use ................................................................................................................. 1 Table of Contents .......................................................................................................... 2 Overview ...................................................................................................................... 12 Important Usage Information ...............................................................................................12 Key Stakeholders ................................................................................................................................. 12 Apply the Correct Version of a Benchmark ...................................................................................... 13 Exceptions ............................................................................................................................................ 13 Remediation ......................................................................................................................................... 14 Summary ............................................................................................................................................... 14 Target Technology Details ...................................................................................................15 Intended Audience................................................................................................................15 Consensus Guidance ...........................................................................................................16 Typographical Conventions .................................................................................................17 Recommendation Definitions ..................................................................................... 18 Title ........................................................................................................................................18 Assessment Status...............................................................................................................18 Automated ............................................................................................................................................ 18 Manual ................................................................................................................................................... 18 Profile ....................................................................................................................................18 Description ............................................................................................................................18 Rationale Statement .............................................................................................................18 Impact Statement ..................................................................................................................19 Audit Procedure ....................................................................................................................19 Remediation Procedure........................................................................................................19 Default Value .........................................................................................................................19 References ............................................................................................................................19 CIS Critical Security Controls® (CIS Controls®) ..................................................................19 Additional Information..........................................................................................................19 Profile Definitions .................................................................................................................20 Acknowledgements ..............................................................................................................21 Recommendations ...................................................................................................... 22 1 Initial Setup ........................................................................................................................22 1.1 Filesystem ...................................................................................................................................... 22 1.1.1 Configure Filesystem Kernel Modules ................................................................................... 23 1.1.1.1 Ensure cramfs kernel module is not available (Automated) ......................................... 24 1.1.1.2 Ensure freevxfs kernel module is not available (Automated) ....................................... 27 Page 2 Internal Only - General 1.1.1.3 Ensure hfs kernel module is not available (Automated) ............................................... 30 1.1.1.4 Ensure hfsplus kernel module is not available (Automated) ........................................ 33 1.1.1.5 Ensure jffs2 kernel module is not available (Automated) ............................................. 36 1.1.1.6 Ensure overlay kernel module is not available (Automated) ........................................ 39 1.1.1.7 Ensure squashfs kernel module is not available (Automated) ..................................... 42 1.1.1.8 Ensure udf kernel module is not available (Automated) ............................................... 45 1.1.1.9 Ensure firewire-core kernel module is not available (Automated) ................................ 48 1.1.1.10 Ensure usb-storage kernel module is not available (Automated) ............................... 51 1.1.1.11 Ensure unused filesystems kernel modules are not available (Manual) .................... 55 1.1.2 Configure Filesystem Partitions ............................................................................................. 62 1.1.2.1 Configure /tmp .................................................................................................................... 63 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated) ......................................... 64 1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated) ............................................ 67 1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated) ........................................... 69 1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated) .......................................... 71 1.1.2.2 Configure /dev/shm ............................................................................................................ 73 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition (Automated) ................................. 74 1.1.2.2.2 Ensure nodev option set on /dev/shm partition (Automated) .................................... 76 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition (Automated) .................................... 78 1.1.2.2.4 Ensure noexec option set on /dev/shm partition (Automated) ................................... 80 1.1.2.3 Configure /home ................................................................................................................. 82 1.1.2.3.1 Ensure separate partition exists for /home (Automated) ........................................... 83 1.1.2.3.2 Ensure nodev option set on /home partition (Automated) ......................................... 85 1.1.2.3.3 Ensure nosuid option set on /home partition (Automated) ........................................ 87 1.1.2.4 Configure /var ..................................................................................................................... 89 1.1.2.4.1 Ensure separate partition exists for /var (Automated) ............................................... 90 1.1.2.4.2 Ensure nodev option set on /var partition (Automated) ............................................. 92 1.1.2.4.3 Ensure nosuid option set on /var partition (Automated) ............................................ 94 1.1.2.5 Configure /var/tmp .............................................................................................................. 96 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated) ........................................ 97 1.1.2.5.2 Ensure nodev option set on /var/tmp partition (Automated) ...................................... 99 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition (Automated) ................................... 101 1.1.2.5.4 Ensure noexec option set on /var/tmp partition (Automated) .................................. 103 1.1.2.6 Configure /var/log ............................................................................................................. 105 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated) ....................................... 106 1.1.2.6.2 Ensure nodev option set on /var/log partition (Automated) ..................................... 108 1.1.2.6.3 Ensure nosuid option set on /var/log partition (Automated) .................................... 110 1.1.2.6.4 Ensure noexec option set on /var/log partition (Automated) ................................... 112 1.1.2.7 Configure /var/log/audit ................................................................................................... 114 1.1.2.7.1 Ensure separate partition exists for /var/log/audit (Automated) .............................. 115 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition (Automated) ............................ 117 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition (Automated) ............................ 119 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition (Automated)........................... 121 1.2 Package Management ................................................................................................................. 123 1.2.1 Configure Package Repositories .......................................................................................... 124 1.2.1.1 Ensure the source.list and .source files use the Signed-By option (Manual) ............. 125 1.2.1.2 Ensure weak dependencies are configured (Automated) .......................................... 128 1.2.1.3 Ensure access to gpg key files are configured (Automated) ...................................... 129 1.2.1.4 Ensure access to /etc/apt/trusted.gpg.d directory is configured (Automated) ............ 131 1.2.1.5 Ensure access to /etc/apt/auth.conf.d directory is configured (Automated) ............... 132 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/ directory is configured (Automated) ................................................................................................................................................ 133 1.2.1.7 Ensure access to /usr/share/keyrings directory is configured (Automated) ............... 135 1.2.1.8 Ensure access to /etc/apt/sources.list.d directory is configured (Automated) ............ 136 1.2.1.9 Ensure access to files in /etc/apt/sources.list.d are configured (Automated) ............. 137 1.2.2 Configure Package Updates ................................................................................................. 138 Page 3 Internal Only - General 1.2.2.1 Ensure updates, patches, and additional security software are installed (Manual) ... 139 1.3 Mandatory Access Control ......................................................................................................... 142 1.3.1 Configure AppArmor.............................................................................................................. 143 1.3.1.1 Ensure apparmor packages are installed (Automated) .............................................. 144 1.3.1.2 Ensure AppArmor is enabled (Automated) ................................................................. 146 1.3.1.3 Ensure all AppArmor Profiles are enforcing (Automated) .......................................... 148 1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is enabled (Automated) ........... 150 1.4 Configure Bootloader .................................................................................................................. 153 1.4.1 Ensure bootloader password is set (Automated) ........................................................... 154 1.4.2 Ensure access to bootloader config is configured (Automated) .................................... 157 1.5 Configure Additional Process Hardening ................................................................................. 159 1.5.1 Ensure fs.protected_hardlinks is configured (Automated) ............................................. 161 1.5.2 Ensure fs.protected_symlinks is configured (Automated) ............................................. 165 1.5.3 Ensure kernel.yama.ptrace_scope is configured (Automated) ...................................... 169 1.5.4 Ensure fs.suid_dumpable is configured (Automated) .................................................... 173 1.5.5 Ensure kernel.dmesg_restrict is configured (Automated).............................................. 177 1.5.6 Ensure prelink is not installed (Automated) ................................................................... 181 1.5.7 Ensure Automatic Error Reporting is configured (Automated) ...................................... 182 1.5.8 Ensure kernel.kptr_restrict is configured (Automated) .................................................. 184 1.5.9 Ensure kernel.randomize_va_space is configured (Automated) ................................... 188 1.5.10 Ensure kernel.yama.ptrace_scope is configured (Automated) .................................... 192 1.5.11 Ensure core file size is configured (Automated) .......................................................... 197 1.5.12 Ensure systemd-coredump ProcessSizeMax is configured (Automated) ................... 199 1.5.13 Ensure systemd-coredump Storage is configured (Automated) .................................. 203 1.6 Configure Command Line Warning Banners ............................................................................ 207 1.6.1 Ensure /etc/motd is configured (Automated) ................................................................. 208 1.6.2 Ensure /etc/issue is configured (Automated) ................................................................. 212 1.6.3 Ensure /etc/issue.net is configured (Automated) ........................................................... 214 1.6.4 Ensure access to /etc/motd is configured (Automated) ................................................. 216 1.6.5 Ensure access to /etc/issue is configured (Automated)................................................. 218 1.6.6 Ensure access to /etc/issue.net is configured (Automated) .......................................... 220 1.7 Configure GNOME Display Manager .......................................................................................... 222 1.7.1 Ensure GDM is removed (Automated) .......................................................................... 223 1.7.2 Ensure GDM login banner is configured (Automated) ................................................... 225 1.7.3 Ensure GDM disable-user-list option is enabled (Automated) ...................................... 228 1.7.4 Ensure GDM screen locks when the user is idle (Automated) ...................................... 231 1.7.5 Ensure GDM screen locks cannot be overridden (Automated) ..................................... 234 1.7.6 Ensure GDM automatic mounting of removable media is disabled (Automated) .......... 237 1.7.7 Ensure GDM disabling automatic mounting of removable media is not overridden (Automated) ............................................................................................................................ 240 1.7.8 Ensure GDM autorun-never is enabled (Automated) .................................................... 243 1.7.9 Ensure GDM autorun-never is not overridden (Automated) .......................................... 246 1.7.10 Ensure XDMCP is not enabled (Automated) ............................................................... 249 1.7.11 Ensure Xwayland is configured (Automated) .............................................................. 252 2 Services............................................................................................................................253 2.1 Configure Server Services .......................................................................................................... 254 2.1.1 Ensure autofs services are not in use (Automated) ....................................................... 255 2.1.2 Ensure avahi daemon services are not in use (Automated) .......................................... 258 2.1.3 Ensure dhcp server services are not in use (Automated).............................................. 261 2.1.4 Ensure dns server services are not in use (Automated)................................................ 263 2.1.5 Ensure dnsmasq services are not in use (Automated) .................................................. 265 2.1.6 Ensure ftp server services are not in use (Automated) ................................................. 267 2.1.7 Ensure ldap server services are not in use (Automated)............................................... 269 2.1.8 Ensure message access server services are not in use (Automated) .......................... 271 2.1.9 Ensure network file system services are not in use (Automated) .................................. 274 Page 4 Internal Only - General 2.1.10 Ensure nis server services are not in use (Automated) ............................................... 276 2.1.11 Ensure print server services are not in use (Automated) ............................................ 278 2.1.12 Ensure rpcbind services are not in use (Automated)................................................... 280 2.1.13 Ensure rsync services are not in use (Automated) ...................................................... 283 2.1.14 Ensure samba file server services are not in use (Automated) ................................... 285 2.1.15 Ensure snmp services are not in use (Automated) ...................................................... 287 2.1.16 Ensure telnet-server services are not in use (Automated) .......................................... 290 2.1.17 Ensure tftp server services are not in use (Automated) .............................................. 292 2.1.18 Ensure web proxy server services are not in use (Automated) ................................... 294 2.1.19 Ensure web server services are not in use (Automated) ............................................. 296 2.1.20 Ensure xinetd services are not in use (Automated) ..................................................... 299 2.1.21 Ensure X window server services are not in use (Automated) .................................... 302 2.1.22 Ensure mail transfer agents are configured for local-only mode (Automated) ............ 304 2.1.23 Ensure only approved services are listening on a network interface (Manual) ........... 307 2.2 Configure Client Services ........................................................................................................... 309 2.2.1 Ensure nis client is not installed (Automated) ................................................................ 310 2.2.2 Ensure rsh client is not installed (Automated) ............................................................... 312 2.2.3 Ensure talk client is not installed (Automated) ............................................................... 314 2.2.4 Ensure telnet client is not installed (Automated) ........................................................... 316 2.2.5 Ensure ldap client is not installed (Automated) ............................................................. 318 2.2.6 Ensure ftp client is not installed (Automated) ................................................................ 320 2.3 Configure Time Synchronization ............................................................................................... 322 2.3.1 Ensure time synchronization is in use................................................................................. 323 2.3.1.1 Ensure a single time synchronization daemon is in use (Automated) ........................ 324 2.3.2 Configure systemd-timesyncd.............................................................................................. 328 2.3.2.1 Ensure systemd-timesyncd configured with authorized timeserver (Automated) ...... 330 2.3.2.2 Ensure systemd-timesyncd is enabled and running (Automated) .............................. 334 2.3.3 Configure chrony ................................................................................................................... 336 2.3.3.1 Ensure chrony is configured with authorized timeserver (Automated) ....................... 337 2.3.3.2 Ensure chrony is running as user _chrony (Automated) ............................................ 341 2.3.3.3 Ensure chrony is enabled and running (Automated) .................................................. 343 2.4 Job Schedulers ............................................................................................................................ 345 2.4.1 Configure cron ........................................................................................................................ 346 2.4.1.1 Ensure cron daemon is enabled and active (Automated) .......................................... 347 2.4.1.2 Ensure access to /etc/crontab is configured (Automated) .......................................... 348 2.4.1.3 Ensure access to /etc/cron.hourly is configured (Automated) .................................... 350 2.4.1.4 Ensure access to /etc/cron.daily is configured (Automated) ...................................... 352 2.4.1.5 Ensure access to /etc/cron.weekly is configured (Automated) ................................... 354 2.4.1.6 Ensure access to /etc/cron.monthly is configured (Automated) ................................. 356 2.4.1.7 Ensure access to /etc/cron.yearly is configured (Automated) .................................... 358 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated) ............................................ 359 2.4.1.9 Ensure access to crontab is configured (Automated) ................................................. 361 2.4.2 Configure at ............................................................................................................................ 365 2.4.2.1 Ensure access to at is configured (Automated) .......................................................... 366 3 Network ............................................................................................................................369 3.1 Configure Network Devices ........................................................................................................ 370 3.1.1 Ensure IPv6 status is identified (Manual) ...................................................................... 371 3.1.2 Ensure wireless interfaces are not available (Automated) ............................................ 374 3.1.3 Ensure bluetooth services are not in use (Automated).................................................. 377 3.2 Configure Network Kernel Modules ........................................................................................... 380 3.2.1 Ensure atm kernel module is not available (Automated) ............................................... 381 3.2.2 Ensure can kernel module is not available (Automated) ............................................... 384 3.2.3 Ensure dccp kernel module is not available (Automated) ............................................. 387 3.2.4 Ensure rds kernel module is not available (Automated) ................................................ 390 3.2.5 Ensure sctp kernel module is not available (Automated) .............................................. 393 Page 5 Internal Only - General 3.2.6 Ensure tipc kernel module is not available (Automated) ............................................... 396 3.3 Configure Network Kernel Parameters ...................................................................................... 399 3.3.1 Configure IPv4 parameters ................................................................................................... 401 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated) .............................................. 402 3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured (Automated) .................................. 406 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured (Automated) ........................... 411 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured (Automated) ........................... 415 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured (Automated) .................... 419 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is configured (Automated) ... 423 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is configured (Automated) .............. 427 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured (Automated) ........................ 431 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is configured (Automated) ................. 435 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured (Automated) ...................... 439 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is configured (Automated) ............... 443 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured (Automated) ..................................... 447 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured (Automated) .............................. 451 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is configured (Automated) ............... 455 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is configured (Automated) ........ 459 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured (Automated) ............................ 463 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured (Automated) ..................... 467 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured (Automated) ..................................... 471 3.3.2 Configure IPv6 parameters ................................................................................................... 475 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured (Automated) .................................. 476 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured (Automated) ........................... 480 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured (Automated) ........................ 484 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is configured (Automated) ................. 488 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is configured (Automated) ................. 492 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is configured (Automated) .......... 496 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured (Automated) ................................... 500 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured (Automated) ............................ 504 4 Host Based Firewall .........................................................................................................508 4.1 Configure Uncomplicated Firewall ............................................................................................. 509 4.1.1 Ensure ufw is installed (Automated) .............................................................................. 510 4.1.2 Ensure ufw service is configured (Automated) .............................................................. 512 4.1.3 Ensure ufw incoming default is configured (Automated) ............................................... 515 4.1.4 Ensure ufw outgoing default is configured (Automated) ................................................ 517 4.1.5 Ensure ufw routed default is configured (Automated) ................................................... 519 5 Access Control ................................................................................................................521 5.1 Configure SSH Server ................................................................................................................. 522 5.1.1 Ensure access to /etc/ssh/sshd_config is configured (Automated) ............................... 524 5.1.2 Ensure access to SSH private host key files is configured (Automated)....................... 526 5.1.3 Ensure access to SSH public host key files is configured (Automated) ........................ 529 5.1.4 Ensure sshd access is configured (Automated) ............................................................ 531 5.1.5 Ensure sshd Banner is configured (Automated) ............................................................ 534 5.1.6 Ensure sshd Ciphers are configured (Automated) ........................................................ 536 5.1.7 Ensure sshd ClientAliveInterval and ClientAliveCountMax are configured (Automated) ................................................................................................................................................ 539 5.1.8 Ensure sshd DisableForwarding is enabled (Automated) ............................................. 542 5.1.9 Ensure sshd GSSAPIAuthentication is disabled (Automated) ...................................... 544 5.1.10 Ensure sshd HostbasedAuthentication is disabled (Automated) ................................. 546 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated) .................................................... 548 5.1.12 Ensure sshd KexAlgorithms is configured (Automated) .............................................. 550 5.1.13 Ensure sshd post-quantum cryptography key exchange algorithms are configured (Automated) ............................................................................................................................ 552 5.1.14 Ensure sshd LoginGraceTime is configured (Automated) ........................................... 555 Page 6 Internal Only - General 5.1.15 Ensure sshd LogLevel is configured (Automated) ....................................................... 557 5.1.16 Ensure sshd MACs are configured (Automated) ......................................................... 559 5.1.17 Ensure sshd MaxAuthTries is configured (Automated) ............................................... 562 5.1.18 Ensure sshd MaxSessions is configured (Automated) ................................................ 564 5.1.19 Ensure sshd MaxStartups is configured (Automated) ................................................. 566 5.1.20 Ensure sshd PermitEmptyPasswords is disabled (Automated) .................................. 567 5.1.21 Ensure sshd PermitRootLogin is disabled (Automated) .............................................. 569 5.1.22 Ensure sshd PermitUserEnvironment is disabled (Automated) .................................. 571 5.1.23 Ensure sshd UsePAM is enabled (Automated) ........................................................... 573 5.2 Configure privilege escalation ................................................................................................... 575 5.2.1 Ensure sudo is installed (Automated) ............................................................................ 576 5.2.2 Ensure sudo commands use pty (Automated) .............................................................. 578 5.2.3 Ensure sudo log file exists (Automated) ........................................................................ 580 5.2.4 Ensure users must provide password for escalation (Automated) ................................ 582 5.2.5 Ensure re-authentication for privilege escalation is not disabled globally (Automated) 584 5.2.6 Ensure sudo timestamp_timeout is configured (Automated) ......................................... 586 5.2.7 Ensure access to the su command is restricted (Automated) ....................................... 588 5.3 Pluggable Authentication Modules ............................................................................................ 590 5.3.1 Configure PAM software packages ...................................................................................... 591 5.3.1.1 Ensure latest version of pam is installed (Automated) ............................................... 592 5.3.1.2 Ensure latest version of libpam-modules is installed (Automated) ............................. 593 5.3.1.3 Ensure latest version of libpam-pwquality is installed (Automated) ........................... 594 5.3.2 Configure pam-auth-update profiles .................................................................................... 596 5.3.2.1 Ensure pam_unix module is enabled (Automated)..................................................... 597 5.3.2.2 Ensure pam_faillock module is enabled (Automated) ................................................ 599 5.3.2.3 Ensure pam_pwquality module is enabled (Automated) ............................................ 602 5.3.2.4 Ensure pam_pwhistory module is enabled (Automated) ............................................ 605 5.3.3 Configure PAM Arguments ................................................................................................... 608 5.3.3.1 Configure pam_faillock module ...................................................................................... 609 5.3.3.1.1 Ensure password failed attempts lockout is configured (Automated)...................... 610 5.3.3.1.2 Ensure password unlock time is configured (Automated) ....................................... 612 5.3.3.1.3 Ensure password failed attempts lockout includes root account (Automated) ........ 614 5.3.3.2 Configure pam_pwquality module .................................................................................. 617 5.3.3.2.1 Ensure password number of changed characters is configured (Automated) ........ 619 5.3.3.2.2 Ensure password length is configured (Automated) ................................................ 622 5.3.3.2.3 Ensure password complexity is configured (Manual) .............................................. 625 5.3.3.2.4 Ensure password same consecutive characters is configured (Automated) ........... 629 5.3.3.2.5 Ensure password maximum sequential characters is configured (Automated) ...... 632 5.3.3.2.6 Ensure password dictionary check is enabled (Automated) .................................... 635 5.3.3.2.7 Ensure password quality checking is enforced (Automated) ................................... 637 5.3.3.2.8 Ensure password quality is enforced for the root user (Automated) ....................... 639 5.3.3.3 Configure pam_pwhistory module ................................................................................. 641 5.3.3.3.1 Ensure password history remember is configured (Automated) ............................. 642 5.3.3.3.2 Ensure password history is enforced for the root user (Automated) ....................... 645 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok (Automated) .................................... 647 5.3.3.4 Configure pam_unix module ........................................................................................... 649 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated) .......................................... 650 5.3.3.4.2 Ensure pam_unix does not include remember (Automated) ................................... 652 5.3.3.4.3 Ensure pam_unix includes a strong password hashing algorithm (Automated) ..... 654 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated) ............................................. 658 5.4 User Accounts and Environment ............................................................................................... 661 5.4.1 Configure shadow password suite parameters .................................................................. 662 5.4.1.1 Ensure password expiration is configured (Automated) ............................................. 663 5.4.1.2 Ensure minimum password days is configured (Manual) ........................................... 666 5.4.1.3 Ensure password expiration warning days is configured (Automated) ....................... 669 5.4.1.4 Ensure strong password hashing algorithm is configured (Automated) ..................... 671 Page 7 Internal Only - General 5.4.1.5 Ensure inactive password lock is configured (Automated) ......................................... 673 5.4.1.6 Ensure all users last password change date is in the past (Automated) .................... 675 5.4.2 Configure root and system accounts and environment .................................................... 676 5.4.2.1 Ensure root is the only UID 0 account (Automated) ................................................... 677 5.4.2.2 Ensure root is the only GID 0 account (Automated) ................................................... 678 5.4.2.3 Ensure group root is the only GID 0 group (Automated) ............................................ 680 5.4.2.4 Ensure root account access is controlled (Automated) .............................................. 681 5.4.2.5 Ensure root path integrity (Automated) ....................................................................... 683 5.4.2.6 Ensure root user umask is configured (Automated) ................................................... 686 5.4.2.7 Ensure system accounts do not have a valid login shell (Automated) ....................... 688 5.4.2.8 Ensure accounts without a valid login shell are locked (Automated) ......................... 690 5.4.3 Configure user default environment .................................................................................... 692 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated) ............................................... 693 5.4.3.2 Ensure default user shell timeout is configured (Automated) ..................................... 694 5.4.3.3 Ensure default user umask is configured (Automated) .............................................. 698 6 Logging and Auditing ......................................................................................................703 6.1 System Logging ........................................................................................................................... 704 6.1.1 Configure journald ................................................................................................................. 705 6.1.1.1 Configure systemd-journald service .............................................................................. 706 6.1.1.1.1 Ensure journald service is active (Automated) ........................................................ 707 6.1.1.1.2 Ensure journald log file access is configured (Manual) ........................................... 709 6.1.1.1.3 Ensure journald log file rotation is configured (Manual) .......................................... 712 6.1.1.1.4 Ensure journald ForwardToSyslog is disabled (Automated) ................................... 714 6.1.1.1.5 Ensure journald Storage is configured (Automated)................................................ 718 6.1.1.1.6 Ensure journald Compress is configured (Automated) ............................................ 721 6.1.1.2 Configure systemd-journal-remote................................................................................. 725 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated) ........................................ 726 6.1.1.2.2 Ensure systemd-journal-upload authentication is configured (Manual)................... 728 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active (Automated) ....................... 730 6.1.1.2.4 Ensure systemd-journal-remote service is not in use (Automated) ......................... 732 6.1.2 Configure rsyslog................................................................................................................... 734 6.1.2.1 Ensure rsyslog is installed (Automated) ..................................................................... 735 6.1.2.2 Ensure rsyslog service is enabled and active (Automated) ........................................ 737 6.1.2.3 Ensure journald is configured to send logs to rsyslog (Automated) ........................... 739 6.1.2.4 Ensure rsyslog log file creation mode is configured (Automated) .............................. 743 6.1.2.5 Ensure rsyslog logging is configured (Manual) ........................................................... 745 6.1.2.6 Ensure rsyslog is configured to send logs to a remote log host (Manual) .................. 747 6.1.2.7 Ensure rsyslog is not configured to receive logs from a remote client (Automated) .. 749 6.1.2.8 Ensure logrotate is configured (Manual) ..................................................................... 751 6.1.2.9 Ensure rsyslog-gnutls is installed (Automated) .......................................................... 753 6.1.2.10 Ensure rsyslog forwarding uses gtls (Automated) .................................................... 755 6.1.2.11 Ensure rsyslog CA certificates are configured (Manual) .......................................... 757 6.1.3 Configure Logfiles.................................................................................................................. 759 6.1.3.1 Ensure access to all logfiles has been configured (Automated) ................................. 760 6.2 System Auditing ........................................................................................................................... 765 6.2.1 Configure auditd Service ....................................................................................................... 767 6.2.1.1 Ensure auditd packages are installed (Automated) .................................................... 768 6.2.1.2 Ensure auditd service is enabled and active (Automated) ......................................... 769 6.2.1.3 Ensure auditing for processes that start prior to auditd is enabled (Automated) ....... 771 6.2.1.4 Ensure audit_backlog_limit is configured (Automated) .............................................. 773 6.2.2 Configure Data Retention ...................................................................................................... 775 6.2.2.1 Ensure audit log storage size is configured (Automated) ........................................... 776 6.2.2.2 Ensure audit logs are not automatically deleted (Automated) .................................... 778 6.2.2.3 Ensure system is disabled when audit logs are full (Automated) ............................... 779 6.2.2.4 Ensure system warns when audit logs are low on space (Automated) ...................... 782 Page 8 Internal Only - General 6.2.3 Configure auditd Rules .......................................................................................................... 785 6.2.3.1 Ensure modification of the /etc/sudoers file is collected (Automated) ........................ 787 6.2.3.2 Ensure actions as another user are always logged (Automated) ............................... 790 6.2.3.3 Ensure events that modify the sudo log file are collected (Automated) ..................... 793 6.2.3.4 Ensure events that modify date and time information are collected (Automated) ...... 796 6.2.3.5 Ensure events that modify sethostname and setdomainname are collected (Automated) ............................................................................................................................ 800 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net are collected (Automated) .. 803 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname are collected (Automated) 806 6.2.3.8 Ensure events that modify the system's network environment are collected (Automated) ............................................................................................................................ 809 6.2.3.9 Ensure events that modify /etc/NetworkManager directory are collected (Automated) ................................................................................................................................................ 813 6.2.3.10 Ensure use of privileged commands are collected (Automated) .............................. 816 6.2.3.11 Ensure unsuccessful file access attempts are collected (Automated) ..................... 820 6.2.3.12 Ensure events that modify /etc/group information are collected (Automated) .......... 824 6.2.3.13 Ensure events that modify /etc/passwd information are collected (Automated) ....... 827 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow are collected (Automated) ................................................................................................................................................ 830 6.2.3.15 Ensure events that modify /etc/security/opasswd are collected (Automated) .......... 833 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are collected (Automated) .......... 836 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/ information are collected (Automated) ............................................................................................................................ 839 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2 are collected (Automated) ............................................ 842 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are collected (Automated) ................................................... 846 6.2.3.20 Ensure discretionary access control permission modification events setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr collected (Automated) ...... 850 6.2.3.21 Ensure successful file system mounts are collected (Automated) ........................... 854 6.2.3.22 Ensure session initiation information is collected (Automated) ................................ 857 6.2.3.23 Ensure login and logout events are collected (Automated) ...................................... 861 6.2.3.24 Ensure unlink file deletion events by users are collected (Automated) .................... 865 6.2.3.25 Ensure rename file deletion events by users are collected (Automated) ................. 869 6.2.3.26 Ensure events that modify the system's Mandatory Access Controls are collected (Automated) ............................................................................................................................ 873 6.2.3.27 Ensure successful and unsuccessful attempts to use the chcon command are collected (Automated) ............................................................................................................. 876 6.2.3.28 Ensure successful and unsuccessful attempts to use the setfacl command are collected (Automated) ............................................................................................................. 879 6.2.3.29 Ensure successful and unsuccessful attempts to use the chacl command are collected (Automated) ............................................................................................................. 882 6.2.3.30 Ensure successful and unsuccessful attempts to use the usermod command are collected (Automated) ............................................................................................................. 885 6.2.3.31 Ensure kernel module loading unloading and modification is collected (Automated) ................................................................................................................................................ 888 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading unloading and modification is collected (Automated) ............................................................................................................. 892 6.2.3.33 Ensure kernel "delete_module" loading unloading and modification is collected (Automated) ............................................................................................................................ 896 6.2.3.34 Ensure kernel query_module loading unloading and modification is collected (Automated) ............................................................................................................................ 900 6.2.3.35 Ensure the audit configuration is loaded regardless of errors (Automated) ............. 904 6.2.3.36 Ensure the audit configuration is immutable (Automated) ........................................ 906 6.2.3.37 Ensure the running and on disk configuration is the same (Manual) ....................... 908 6.2.4 Configure auditd File Access ................................................................................................ 910 Page 9 Internal Only - General 6.2.4.1 Ensure audit log files mode is configured (Automated) .............................................. 911 6.2.4.2 Ensure audit log files owner is configured (Automated) ............................................. 913 6.2.4.3 Ensure audit log files group owner is configured (Automated) ................................... 915 6.2.4.4 Ensure the audit log file directory mode is configured (Automated) ........................... 917 6.2.4.5 Ensure audit configuration files mode is configured (Automated) .............................. 919 6.2.4.6 Ensure audit configuration files owner is configured (Automated) ............................. 921 6.2.4.7 Ensure audit configuration files group owner is configured (Automated) ................... 923 6.2.4.8 Ensure audit tools mode is configured (Automated)................................................... 925 6.2.4.9 Ensure audit tools owner is configured (Automated) .................................................. 927 6.2.4.10 Ensure audit tools group owner is configured (Automated) ..................................... 928 6.3 Configure Integrity Checking ..................................................................................................... 929 6.3.1 Ensure AIDE is installed (Automated) ........................................................................... 930 6.3.2 Ensure filesystem integrity is regularly checked (Automated) ....................................... 932 6.3.3 Ensure cryptographic mechanisms are used to protect the integrity of audit tools (Automated) ............................................................................................................................ 934 7 System Maintenance .......................................................................................................938 7.1 Configure system file and directory access ............................................................................. 939 7.1.1 Ensure access to /etc/passwd is configured (Automated) ............................................. 940 7.1.2 Ensure access to /etc/passwd- is configured (Automated) ........................................... 942 7.1.3 Ensure access to /etc/group is configured (Automated) ................................................ 944 7.1.4 Ensure access to /etc/group- is configured (Automated)............................................... 946 7.1.5 Ensure access to /etc/shadow is configured (Automated) ............................................ 948 7.1.6 Ensure access to /etc/shadow- is configured (Automated) ........................................... 950 7.1.7 Ensure access to /etc/gshadow is configured (Automated) .......................................... 952 7.1.8 Ensure access to /etc/gshadow- is configured (Automated) ......................................... 954 7.1.9 Ensure access to /etc/shells is configured (Automated) ................................................ 956 7.1.10 Ensure access to /etc/security/opasswd is configured (Automated) ........................... 958 7.1.11 Ensure world writable files and directories are secured (Automated) ......................... 960 7.1.12 Ensure no files or directories without an owner and a group exist (Automated) ......... 964 7.1.13 Ensure SUID and SGID files are reviewed (Manual) ................................................... 967 7.2 Local User and Group Settings .................................................................................................. 970 7.2.1 Ensure accounts in /etc/passwd use shadowed passwords (Automated) .................... 971 7.2.2 Ensure /etc/shadow password fields are not empty (Automated) ................................. 973 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group (Automated) ................................. 975 7.2.4 Ensure shadow group is empty (Automated) ................................................................ 977 7.2.5 Ensure no duplicate UIDs exist (Automated) ................................................................. 979 7.2.6 Ensure no duplicate GIDs exist (Automated) ................................................................ 981 7.2.7 Ensure no duplicate user names exist (Automated) ...................................................... 983 7.2.8 Ensure no duplicate group names exist (Automated).................................................... 984 7.2.9 Ensure local interactive user home directories are configured (Automated) ................. 985 7.2.10 Ensure local interactive user dot files access is configured (Automated) ................... 989 Appendix: Summary Table ....................................................................................... 995 Appendix: CIS Controls v7 IG 1 Mapped Recommendations .............................. 1010 Appendix: CIS Controls v7 IG 2 Mapped Recommendations .............................. 1015 Appendix: CIS Controls v7 IG 3 Mapped Recommendations .............................. 1025 Appendix: CIS Controls v7 Unmapped Recommendations ................................. 1035 Appendix: CIS Controls v8 IG 1 Mapped Recommendations .............................. 1036 Appendix: CIS Controls v8 IG 2 Mapped Recommendations .............................. 1041 Appendix: CIS Controls v8 IG 3 Mapped Recommendations .............................. 1051 Page 10 Internal Only - General Appendix: CIS Controls v8 Unmapped Recommendations ................................. 1061 Appendix: Change History ..................................................................................... 1062 Page 11 Internal Only - General Overview All CIS Benchmarks™ (Benchmarks) focus on technical configuration settings used to maintain and/or increase the security of the addressed technology, and they should be used in conjunction with other essential cyber hygiene tasks like: • Monitoring the base operating system and applications for vulnerabilities and quickly updating with the latest security patches. • End-point protection (Antivirus software, Endpoint Detection and Response (EDR), etc.). • Logging and monitoring user and system activity. In the end, the Benchmarks are designed to be a key component of a comprehensive cybersecurity program. Important Usage Information All Benchmarks are available free for non-commercial use from the CIS Website. They can be used to manually assess and remediate systems and applications. In lieu of manual assessment and remediation, there are several tools available to assist with assessment: • CIS Configuration Assessment Tool (CIS-CAT® Pro Assessor) • CIS Benchmarks™ Certified 3rd Party Tooling These tools make the hardening process much more scalable for large numbers of systems and applications. NOTE: Some tooling focuses only on the Benchmark Recommendations that can be fully automated (skipping ones marked Manual). It is important that ALL Recommendations (Automated and Manual) be addressed since all are important for properly securing systems and are typically in scope for audits. Key Stakeholders Cybersecurity is a collaborative effort, and cross functional cooperation is imperative within an organization to discuss, test, and deploy Benchmarks in an effective and efficient way. The Benchmarks are developed to be best practice configuration guidelines applicable to a wide range of use cases. In some organizations, exceptions to specific Recommendations will be needed, and this team should work to prioritize the problematic Recommendations based on several factors like risk, time, cost, and labor. These exceptions should be properly categorized and documented for auditing purposes. Page 12 Internal Only - General Apply the Correct Version of a Benchmark Benchmarks are developed and tested for a specific set of products and versions and applying an incorrect Benchmark to a system can cause the resulting pass/fail score to be incorrect. This is due to the assessment of settings that do not apply to the target systems. To assure the correct Benchmark is being assessed: • Deploy the Benchmark applicable to the way settings are managed in the environment: An example of this is the Microsoft Windows family of Benchmarks, which have separate Benchmarks for Group Policy, Intune, and Stand-alone systems based upon how system management is deployed. Applying the wrong Benchmark in this case will give invalid results. • Use the most recent version of a Benchmark: This is true for all Benchmarks, but especially true for cloud technologies. Cloud technologies change frequently and using an older version of a Benchmark may have invalid methods for auditing and remediation. Exceptions The guidance items in the Benchmarks are called recommendations and not requirements, and exceptions to some of them are expected and acceptable. The Benchmarks strive to be a secure baseline, or starting point, for a specific technology, with known issues identified during Benchmark development are documented in the Impact section of each Recommendation. In addition, organizational, system specific requirements, or local site policy may require changes as well, or an exception to a Recommendation or group of Recommendations (e.g. A Benchmark could Recommend that a Web server not be installed on the system, but if a system's primary purpose is to function as a Webserver, there should be a documented exception to this Recommendation for that specific server). In the end, exceptions to some Benchmark Recommendations are common and acceptable, and should be handled as follows: • The reasons for the exception should be reviewed cross-functionally and be well documented for audit purposes. • A plan should be developed for mitigating, or eliminating, the exception in the future, if applicable. • If the organization decides to accept the risk of this exception (not work toward mitigation or elimination), this should be documented for audit purposes. It is the responsibility of the organization to determine their overall security policy, and which settings are applicable to their unique needs based on the overall risk profile for the organization. Page 13 Internal Only - General Remediation CIS has developed Build Kits for many technologies to assist in the automation of hardening systems. Build Kits are designed to correspond to Benchmark's “Remediation” section, which provides the manual remediation steps necessary to make that Recommendation compliant to the Benchmark. When remediating systems (changing configuration settings on deployed systems as per the Benchmark's Recommendations), please approach this with caution and test thoroughly. The following is a reasonable remediation approach to follow: • CIS Build Kits, or internally developed remediation methods should never be applied to production systems without proper testing. • Proper testing consists of the following: o Understand the configuration (including installed applications) of the targeted systems. Various parts of the organization may need different configurations (e.g., software developers vs standard office workers). o Read the Impact section of the given Recommendation to help determine if there might be an issue with the targeted systems. o Test the configuration changes with representative lab system(s). If issues arise during testing, they can be resolved prior to deploying to any production systems. o When testing is complete, initially deploy to a small sub-set of production systems and monitor closely for issues. If there are issues, they can be resolved prior to deploying more broadly. o When the initial deployment above is completes successfully, iteratively deploy to additional systems and monitor closely for issues. Repeat this process until the full deployment is complete. Summary Using the Benchmarks Certified tools, working as a team with key stakeholders, being selective with exceptions, and being careful with remediation deployment, it is possible to harden large numbers of deployed systems in a cost effective, efficient, and safe manner. NOTE: As previously stated, the PDF versions of the CIS Benchmarks™ are available for free, non-commercial use on the CIS Website. All other formats of the CIS Benchmarks™ (MS Word, Excel, and Build Kits) are available for CIS SecureSuite® members. CIS-CAT® Pro is also available to CIS SecureSuite® members. Page 14 Internal Only - General Target Technology Details This document provides prescriptive guidance for establishing a secure configuration posture for Debian 13 derived Linux distribution systems running on x86_64 platforms. This guide was developed and tested against Distribution 13.3 The guidance within broadly assumes that operations are being performed as the root user, and executed under the default Bash version for the applicable distribution. Operations performed using sudo instead of the root user, or executed under another shell, may produce unexpected results, or fail to make the intended changes to the system. Non-root users may not be able to access certain areas of the system, especially after remediation has been performed. It is advisable to verify root users path integrity and the integrity of any programs being run prior to execution of commands and scripts included in this benchmark. The default prompt for the root user is #, and as such all sample commands will have # as an additional indication that it is to be executed as root. To obtain the latest version of this guide, please visit https://workbench.cisecurity.org. If you have questions, comments, or have identified ways to improve this guide, please write us at feedback@cisecurity.org. Intended Audience This benchmark is intended for system and application administrators, security specialists, auditors, help desk, and platform deployment personnel who plan to develop, deploy, assess, or secure solutions that incorporate Debian 13 Linux distributions on x86_64 platforms. Page 15 Internal Only - General Consensus Guidance This CIS Benchmark™ was created using a consensus review process comprised of a global community of subject matter experts. The process combines real world experience with data-based information to create technology specific guidance to assist users to secure their environments. Consensus participants provide perspective from a diverse set of backgrounds including consulting, software development, audit and compliance, security research, operations, government, and legal. Each CIS Benchmark undergoes two phases of consensus review. The first phase occurs during initial Benchmark development. During this phase, subject matter experts convene to discuss, create, and test working drafts of the Benchmark. This discussion occurs until consensus has been reached on Benchmark recommendations. The second phase begins after the Benchmark has been published. During this phase, all feedback provided by the Internet community is reviewed by the consensus team for incorporation in the Benchmark. If you are interested in participating in the consensus process, please visit https://workbench.cisecurity.org/. Page 16 Internal Only - General Typographical Conventions The following typographical conventions are used throughout this guide: Convention Meaning Used for blocks of code, command, and Stylized Monospace font script examples. Text should be interpreted exactly as presented. Used for inline code, commands, UI/Menu Monospace font selections or examples. Text should be interpreted exactly as presented. Text set in angle brackets denote a variable requiring substitution for a real value. Used to reference other relevant settings, CIS Benchmarks and/or Benchmark Italic font Communities. Also, used to denote the title of a book, article, or other publication. Additional information or caveats things like Notes, Warnings, or Cautions (usually just Bold font the word itself and the rest of the text normal). Page 17 Internal Only - General Recommendation Definitions The following defines the various components included in a CIS recommendation as applicable. If any of the components are not applicable it will be noted, or the component will not be included in the recommendation. Title Concise description for the recommendation's intended configuration. Assessment Status An assessment status is included for every recommendation. The assessment status indicates whether the given recommendation can be automated or requires manual steps to implement. Both statuses are equally important and are determined and supported as defined below: Automated Represents recommendations for which assessment of a technical control can be fully automated and validated to a pass/fail state. Recommendations will include the necessary information to implement automation. Manual Represents recommendations for which assessment of a technical control cannot be fully automated and requires all or some manual steps to validate that the configured state is set as expected. The expected state can vary depending on the environment. Profile A collection of recommendations for securing a technology or a supporting platform. Most benchmarks include at least a Level 1 and Level 2 Profile. Level 2 extends Level 1 recommendations and is not a standalone profile. The Profile Definitions section in the benchmark provides the definitions as they pertain to the recommendations included for the technology. Description Detailed information pertaining to the setting with which the recommendation is concerned. In some cases, the description will include the recommended value. Rationale Statement Detailed reasoning for the recommendation to provide the user a clear and concise understanding on the importance of the recommendation. Page 18 Internal Only - General Impact Statement Any security, functionality, or operational consequences that can result from following the recommendation. Audit Procedure Systematic instructions for determining if the target system complies with the recommendation. Remediation Procedure Systematic instructions for applying recommendations to the target system to bring it into compliance according to the recommendation. Default Value Default value for the given setting in this recommendation, if known. If not known, either not configured or not defined will be applied. References Additional documentation relative to the recommendation. CIS Critical Security Controls® (CIS Controls®) The mapping between a recommendation and the CIS Controls is organized by CIS Controls version, Safeguard, and Implementation Group (IG). The Benchmark in its entirety addresses the CIS Controls safeguards of (v7) “5.1 - Establish Secure Configurations” and (v8) '4.1 - Establish and Maintain a Secure Configuration Process” so individual recommendations will not be mapped to these safeguards. Additional Information Supplementary information that does not correspond to any other field but may be useful to the user. Page 19 Internal Only - General Profile Definitions The following configuration profiles are defined by this Benchmark: • Level 1 - Server Items in this profile intend to: o be practical and prudent; o provide a clear security benefit; and o not inhibit the utility of the technology beyond acceptable means. This profile is intended for servers. • Level 2 - Server This profile extends the "Level 1 - Server" profile. Items in this profile exhibit one or more of the following characteristics: o are intended for environments or use cases where security is paramount. o acts as defense in depth measure. o may negatively inhibit the utility or performance of the technology. This profile is intended for servers. • Level 1 - Workstation Items in this profile intend to: o be practical and prudent; o provide a clear security benefit; and o not inhibit the utility of the technology beyond acceptable means. This profile is intended for workstations. • Level 2 - Workstation This profile extends the "Level 1 - Workstation" profile. Items in this profile exhibit one or more of the following characteristics: o are intended for environments or use cases where security is paramount. o acts as defense in depth measure. o may negatively inhibit the utility or performance of the technology. This profile is intended for workstations. Page 20 Internal Only - General Acknowledgements This Benchmark exemplifies the great things a community of users, vendors, and subject matter experts can accomplish through consensus collaboration. The CIS community thanks the entire consensus team with special recognition to the following individuals who contributed greatly to the creation of this guide: This benchmark is based upon previous Linux benchmarks published and would not be possible without the contributions provided over the history of all of these benchmarks. The CIS community thanks everyone who has contributed to the Linux benchmarks. Contributor Ron Colvin Dave Billing Dominic Pace Koen Laevens Mark Birch Thomas Sjögren James Trigg Matthew Burket Marcus Burghardt Graham Eames Robert McSulla Chad Streck Ryan Jaynes Cory Sherman Simon John Steve Cobrin Justin Brown Mike Cross Kleber Leal Laurent Mesure Andrew Box Nathaniel Hooker Editor Jonathan Lewis Christopherson Eric Pinnell Gokhan Lus Randie Bejar Trevor Wood Page 21 Internal Only - General Recommendations 1 Initial Setup Items in this section are advised for all systems but may be difficult or require extensive preparation after the initial setup of the system. 1.1 Filesystem The file system is generally a built-in layer used to handle the data management of the storage. Page 22 Internal Only - General 1.1.1 Configure Filesystem Kernel Modules Several uncommon filesystem types are supported under Linux. Removing support for unneeded filesystem types reduces the local attack surface of the system. If a filesystem type is not needed it should be disabled. Native Linux file systems are designed to ensure that built-in security controls function as expected. Non-native filesystems can lead to unexpected consequences to both the security and functionality of the system and should be used with caution. Many filesystems are created for niche use cases and are not maintained and supported as the operating systems are updated and patched. Users of non-native filesystems should ensure that there is attention and ongoing support for them, especially in light of frequent operating system changes. Standard network connectivity and Internet access to cloud storage may make the use of non-standard filesystem formats to directly attach heterogeneous devices much less attractive. Note: This should not be considered a comprehensive list of filesystems. You may wish to consider additions to those listed here for your environment. For the current available file system modules on the system see ls /usr/lib/modules/**/kernel/fs | sort -u. Start up scripts Kernel modules loaded directly via insmod will ignore what is configured in the relevant /etc/modprobe.d/*.conf files. If modules are still being loaded after a reboot whilst having the correctly configured blacklist and install command, check for insmod entries in start up scripts such as .bashrc. Return values Using /bin/false as the command in disabling a particular module serves two purposes; to convey the meaning of the entry to the user and cause a non-zero return value. The latter can be tested for in scripts. Please note that insmod will ignore what is configured in the relevant configuration files. The preferred way to load modules is with modprobe. Page 23 Internal Only - General 1.1.1.1 Ensure cramfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the cramfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the cramfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="cramfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the cramfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the cramfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the cramfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the cramfs kernel module is not loaded: # lsmod | grep 'cramfs' Nothing should be returned. Page 24 Internal Only - General Run the following command to verify the cramfs kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+cramfs\b' Verify the output includes: blacklist cramfs -AND EITHER- install cramfs /bin/false -OR- install cramfs /bin/true Example output: blacklist cramfs install cramfs /bin/false Remediation: Unload and disable the cramfs kernel module. 1. Run the following commands to unload the cramfs kernel module: # modprobe -r cramfs 2>/dev/null # rmmod cramfs 2>/dev/null 2. Perform the following to disable the cramfs kernel module: Create a file ending in .conf with install cramfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install cramfs /bin/false" >> /etc/modprobe.d/60- cramfs.conf Create a file ending in .conf with blacklist cramfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist cramfs" >> /etc/modprobe.d/60-cramfs.conf Page 25 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53: CM-7 a 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040025 | RULE ID: SV-230498r1069314 | CAT III 5. STIG ID: OL08-00-040025 | RULE ID: SV-248833r958478 | CAT III 6. STIG ID: RHEL-09-231195 | RULE ID: SV-257880r1044951 | CAT III 7. STIG ID: ALMA-09-029940 | RULE ID: SV-269344r1050226 | CAT II 8. STIG ID: OL09-00-000045 | RULE ID: SV-271448r1091056 | CAT III CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 26 Internal Only - General 1.1.1.2 Ensure freevxfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The freevxfs filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the freevxfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the freevxfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="freevxfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the freevxfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the freevxfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the freevxfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the freevxfs kernel module is not loaded: Page 27 Internal Only - General # lsmod | grep 'freevxfs' Nothing should be returned. Run the following command to verify the freevxfs kernel module is not loadable: modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+freevxfs\b' Verify the output includes: blacklist freevxfs -AND- install freevxfs /bin/false -OR- install freevxfs /bin/true Example output: blacklist freevxfs install freevxfs /bin/false Remediation: Unload and disable the freevxfs kernel module. 1. Run the following commands to unload the freevxfs kernel module: # modprobe -r freevxfs 2>/dev/null # rmmod freevxfs 2>/dev/null 2. Perform the following to disable the freevxfs kernel module: Create a file ending in .conf with install freevxfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install freevxfs /bin/false" >> /etc/modprobe.d/60- freevxfs.conf Create a file ending in .conf with blacklist freevxfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist freevxfs" >> /etc/modprobe.d/60-freevxfs.conf Page 28 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 29 Internal Only - General 1.1.1.3 Ensure hfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The hfs filesystem type is a hierarchical filesystem that allows you to mount Mac OS filesystems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the hfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the hfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="hfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the hfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the hfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the hfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the hfs kernel module is not loaded: # lsmod | grep 'hfs' Nothing should be returned. Run the following command to verify the hfs kernel module is not loadable: Page 30 Internal Only - General # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+hfs\b' Verify the output includes: blacklist hfs -AND- install hfs /bin/false -OR- install hfs /bin/true Example output: blacklist hfs install hfs /bin/false Remediation: Unload and disable the hfs kernel module. 1. Run the following commands to unload the hfs kernel module: modprobe -r hfs 2>/dev/null rmmod hfs 2>/dev/null 2. Perform the following to disable the hfs kernel module: Create a file ending in .conf with install hfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install hfs /bin/false" >> /etc/modprobe.d/60-hfs.conf Create a file ending in .conf with blacklist hfs in the /etc/modprobe.d/ directory. Example: printf '%s\n' "" "blacklist hfs" >> /etc/modprobe.d/60-hfs.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 31 Internal Only - General Page 32 Internal Only - General 1.1.1.4 Ensure hfsplus kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The hfsplus filesystem type is a hierarchical filesystem designed to replace hfs that allows you to mount Mac OS filesystems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the hfsplus kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the hfsplus kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="hfsplus" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the hfsplus kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the hfsplus filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the hfsplus kernel module is not loaded and not loadable by performing the following: Run the following command to verify the hfsplus kernel module is not loaded: # lsmod | grep 'hfsplus' Nothing should be returned. Run the following command to verify the hfsplus kernel module is not loadable: Page 33 Internal Only - General # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+hfsplus\b' Verify the output includes: blacklist hfsplus -AND- install hfsplus /bin/false -OR- install hfsplus /bin/true Example output: blacklist hfsplus install hfsplus /bin/false Remediation: Unload and disable the hfsplus kernel module. 1. Run the following commands to unload the hfsplus kernel module: # modprobe -r hfsplus 2>/dev/null # rmmod hfsplus 2>/dev/null 2. Perform the following to disable the hfsplus kernel module: Create a file ending in .conf with install hfsplus /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install hfsplus /bin/false" >> /etc/modprobe.d/60- hfsplus.conf Create a file ending in .conf with blacklist hfsplus in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist hfsplus" >> /etc/modprobe.d/60-hfsplus.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Page 34 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 35 Internal Only - General 1.1.1.5 Ensure jffs2 kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The jffs2 (journaling flash filesystem 2) filesystem type is a log-structured filesystem used in flash memory devices. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the jffs2 kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the jffs2 kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="jffs2" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the jffs2 kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the jffs2 filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the jffs2 kernel module is not loaded and not loadable by performing the following: Run the following command to verify the jffs2 kernel module is not loaded: lsmod | grep 'jffs2' Nothing should be returned. Run the following command to verify the jffs2 kernel module is not loadable: Page 36 Internal Only - General modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+jffs2\b' Verify the output includes: blacklist jffs2 -AND- install jffs2 /bin/false -OR- install jffs2 /bin/true Example output: blacklist jffs2 install jffs2 /bin/false Remediation: Unload and disable the jffs2 kernel module. 1. Run the following commands to unload the jffs2 kernel module: # modprobe -r jffs2 2>/dev/null # rmmod jffs2 2>/dev/null 2. Perform the following to disable the jffs2 kernel module: Create a file ending in .conf with install jffs2 /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install jffs2 /bin/false" >> /etc/modprobe.d/60- jffs2.conf Create a file ending in .conf with blacklist jffs2 in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist jffs2" >> /etc/modprobe.d/60-jffs2.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Page 37 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 38 Internal Only - General 1.1.1.6 Ensure overlay kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The Linux overlay kernel module, commonly referred to as Overlayfs, is a union mount filesystem. It allows the user to overlay one file system on top of another, and creates a single, unified view. Rationale: The overlay kernel module has known CVE's: CVE-2023-32629, CVE-2023-2640, and CVE-2023-0386. Disabling the overlay kernel module reduces the local attack surface by removing support for unnecessary filesystem types and mitigates potential risks associated with unauthorized execution of setuid files, enhancing the overall system security. Impact: WARNING: If Container applications such as Docker, Kubernetes, Podman, Linux Containers (LXC), etc. are in use proceed with caution and consider the impact on containerized workloads, as disabling the overlay may severely disrupt containerization. Audit: Verify the overlay kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the overlay kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="overlayfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the overlay kernel module is not available on the system and no further audit steps are required. Page 39 Internal Only - General Note: Some systems may include the overlay kernel module as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the overlay kernel module is not loaded and not loadable by performing the following: Run the following command to verify the overlay kernel module is not loaded: # lsmod | grep 'overlay' Nothing should be returned Run the following command to verify the overlay kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+overlay\b' Verify the output includes: blacklist overlay -AND- install overlay /bin/false -OR- install overlay /bin/true Example output: blacklist overlay install overlay /bin/false Page 40 Internal Only - General Remediation: Unload and disable the overlay kernel module. 1. Run the following commands to unload the overlay kernel module: # modprobe -r overlay 2>/dev/null # rmmod overlay 2>/dev/null 2. Perform the following to disable the overlay kernel module: Create a file ending in .conf with install overlay /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install overlay /bin/false" >> /etc/modprobe.d/60- overlay.conf Create a file ending in .conf with blacklist overlay in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist overlay" >> /etc/modprobe.d/60-overlay.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. https://docs.kernel.org/filesystems/overlayfs.html 5. https://wiki.archlinux.org/title/Overlay_filesystem 6. https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=overlayfs CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 41 Internal Only - General 1.1.1.7 Ensure squashfs kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A squashfs image can be used without having to first decompress the image. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Impact: As Snap packages utilize squashfs as a compressed filesystem, disabling squashfs will cause Snap packages to fail. Snap application packages of software are self-contained and work across a range of Linux distributions. This is unlike traditional Linux package management approaches, like APT or RPM, which require specifically adapted packages per Linux distribution on an application update and delay therefore application deployment from developers to their software's end-user. Snaps themselves have no dependency on any external store ("App store"), can be obtained from any source and can be therefore used for upstream software deployment. Audit: Verify the squashfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the squashfs kernel module is available on the system: Page 42 Internal Only - General #!/usr/bin/env bash { l_mod_name="squashfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the squashfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the squashfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the squashfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the squashfs kernel module is not loaded: # lsmod | grep 'squashfs' Nothing should be returned. Run the following command to verify the squashfs kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+squashfs\b' Verify the output includes: blacklist squashfs -AND- install squashfs /bin/false -OR- install squashfs /bin/true Example output: blacklist squashfs install squashfs /bin/false Page 43 Internal Only - General Remediation: Unload and disable the squashfs kernel module. 1. Run the following commands to unload the squashfs kernel module: # modprobe -r squashfs 2>/dev/null # rmmod squashfs 2>/dev/null 2. Perform the following to disable the squashfs kernel module: Create a file ending in .conf with install squashfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install squashfs /bin/false" >> /etc/modprobe.d/60- squashfs.conf Create a file ending in .conf with blacklist squashfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist squashfs" >> /etc/modprobe.d/60-squashfs.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: ALMA-09-030160 | RULE ID: SV-269346r1050228 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 44 Internal Only - General 1.1.1.8 Ensure udf kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The udf filesystem type is the universal disk format used to implement ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is necessary to support writing DVDs and newer optical disc formats. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Impact: Microsoft Azure requires the usage of udf. udf should not be disabled on systems run on Microsoft Azure. Audit: Verify the udf kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the udf kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="udf" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the udf kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the udf filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 45 Internal Only - General 2. Verify the udf kernel module is not loaded and not loadable by performing the following: Run the following command to verify the udf kernel module is not loaded: # lsmod | grep 'udf' Nothing should be returned Run the following command to verify the udf kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+udf\b' Verify the output includes: blacklist udf -AND- install udf /bin/false -OR- install udf /bin/true Example output: blacklist udf install udf /bin/false Remediation: Unload and disable the udf kernel module. 1. Run the following commands to unload the udf kernel module: # modprobe -r udf 2>/dev/null # rmmod udf 2>/dev/null 2. Perform the following to disable the udf kernel module: Create a file ending in .conf with install udf /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install udf /bin/false" >> /etc/modprobe.d/60-udf.conf Create a file ending in .conf with blacklist udf in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist udf" >> /etc/modprobe.d/60-udf.conf Page 46 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: ALMA-09-030380 | RULE ID: SV-269348r1050230 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 47 Internal Only - General 1.1.1.9 Ensure firewire-core kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: The IEEE 1394 (FireWire) is a serial bus standard for high-speed real-time communication. Rationale: Disabling FireWire protects the system against exploitation of any flaws in its implementation. Audit: Verify the firewire-core kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the firewire-core kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="firewire" l_mod_type="drivers" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the firewire-core kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the firewire-core filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the firewire-core kernel module is not loaded and not loadable by performing the following: Run the following command to verify the firewire-core kernel module is not loaded: Page 48 Internal Only - General # lsmod | grep -P -- 'firewire(_|-)core' Nothing should be returned Run the following command to verify the firewire-core kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+firewire(_|- )core\b' Verify the output includes: blacklist firewire_core -AND- install firewire_core /bin/false -OR- install firewire_core /bin/true Example output: blacklist firewire_core install firewire_core /bin/false Remediation: Unload and disable the firewire-core kernel module. 1. Run the following commands to unload the firewire-core kernel module: # modprobe -r firewire-core 2>/dev/null # rmmod firewire-core 2>/dev/null 2. Perform the following to disable the firewire-core kernel module: Create a file ending in .conf with install firewire-core /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install firewire-core /bin/false" >> /etc/modprobe.d/60- firewire-core.conf Create a file ending in .conf with blacklist firewire-core in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist firewire-core" >> /etc/modprobe.d/60-firewire- core.conf Page 49 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040026 | RULE ID: SV-230499r1069315 | CAT III 5. STIG ID: OL08-00-040026 | RULE ID: SV-248834r958478 | CAT III 6. STIG ID: RHEL-09-213055 | RULE ID: SV-257806r1044859 | CAT II 7. STIG ID: OL09-00-000042 | RULE ID: SV-271445r1091047 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 50 Internal Only - General 1.1.1.10 Ensure usb-storage kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: USB storage provides a means to transfer and store files ensuring persistence and availability of the files independent of network connection status. Its popularity and utility has led to USB-based malware being a simple and common means for network infiltration and a first step to establishing a persistent threat within a networked environment. Rationale: Restricting USB access on the system will decrease the physical attack surface for a device and diminish the possible vectors to introduce malware. Satisfies: SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163 Impact: Disabling the usb-storage module will disable any usage of USB storage devices. If requirements and local site policy allow the use of such devices, other solutions should be configured accordingly instead. One example of a commonly used solution is USBGuard. Audit: Verify the usb-storage kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the usb-storage kernel module is available on the system: Page 51 Internal Only - General #!/usr/bin/env bash { l_mod_name="usb-storage" l_mod_type="drivers" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the usb-storage kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the usb-storage filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the usb-storage kernel module is not loaded and not loadable by performing the following: Run the following command to verify the usb-storage kernel module is not loaded: # lsmod | grep -P -- 'usb(_|-)storage' Nothing should be returned Run the following command to verify the usb-storage kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+usb_storage\b' Verify the output includes: blacklist usb_storage -AND- install usb_storage /bin/false -OR- install usb_storage /bin/true Example output: blacklist usb_storage install usb_storage /bin/false Page 52 Internal Only - General Remediation: Unload and disable the usb-storage kernel module. 1. Run the following commands to unload the usb-storage kernel module: # modprobe -r usb-storage 2>/dev/null # rmmod usb-storage 2>/dev/null 2. Perform the following to disable the usb-storage kernel module: Create a file ending in .conf with install usb_storage /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install usb_storage /bin/false" >> /etc/modprobe.d/60- usb-storage.conf Create a file ending in .conf with blacklist usb_storage in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist usb_storage" >> /etc/modprobe.d/60-usb- storage.conf References: 1. CCI-000778 | CCI-001958 | CCI-003959 2. NIST SP 800-53 :: IA-3 | NIST SP 800-53 :: CM-7 (9) (b) 3. NIST SP 800-53A :: IA-3.1 (ii) 4. STIG ID: RHEL-08-040080 | RULE ID: SV-230503r1069316 | CAT II 5. STIG ID: OL08-00-040080 | RULE ID: SV-248837r986386 | CAT II 6. STIG ID: RHEL-09-291010 | RULE ID: SV-258034r1051267 | CAT II 7. STIG ID: ALMA-09-031370 | RULE ID: SV-269357r1050240 | CAT II 8. STIG ID: OL09-00-000047 | RULE ID: SV-271450r1092466 | CAT II 9. STIG ID: OL09-00-002332 | RULE ID: SV-271702r1091818 | CAT II 10. STIG ID: UBTU-22-291010 | RULE ID: SV-260540r986276 | CAT II 11. STIG ID: UBTU-24-300039 | RULE ID: SV-270718r1067128 | CAT II 12. STIG ID: SLES-15-010480 | RULE ID: SV-234856r958820 | CAT II Additional Information: An alternative solution to disabling the usb-storage module may be found in USBGuard. Use of USBGuard and construction of USB device policies should be done in alignment with site policy. Page 53 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 10.3 Disable Autorun and Autoplay for Removable Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. 13.7 Manage USB Devices v7 If USB storage devices are required, enterprise software should be used that can configure systems to allow the use of specific devices. An inventory of such ● ● devices should be maintained. Page 54 Internal Only - General 1.1.1.11 Ensure unused filesystems kernel modules are not available (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Filesystem kernel modules are pieces of code that can be dynamically loaded into the Linux kernel to extend its filesystem capabilities, or so-called base kernel, of an operating system. Filesystem kernel modules are typically used to add support for new hardware (as device drivers), or for adding system calls. Rationale: While loadable filesystem kernel modules are a convenient method of modifying the running kernel, this can be abused by attackers on a compromised system to prevent detection of their processes or files, allowing them to maintain control over the system. Many rootkits make use of loadable filesystem kernel modules in this way. Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. The following filesystem kernel modules have known CVE's and should be made unavailable if no dependencies exist: • ceph - CVE-2022-0670 • cifs - CVE-2022-29869 • exfat CVE-2022-29973 • ext CVE-2022-1184 • fat CVE-2022-22043 • fscache CVE-2022-3630 • fuse CVE-2023-0386 • gfs2 CVE-2023-3212 • nfs_common CVE-2023-6660 • nfsd CVE-2022-43945 • smbfs_common CVE-2022-2585 Impact: This list may be quite extensive and covering all edges cases is difficult. Therefore, it's crucial to carefully consider the implications and dependencies before making any changes to the filesystem kernel module configurations. Audit: Verify filesystem kernel modules that are not in use on the system are disabled. Review currently loaded kernel modules to ensure they are needed and conform to local site policy. Page 55 Internal Only - General Note: The "Audit script" included at the bottom of the "Audit Procedure" will perform the steps included below. 1. Run the following command to generate a list of filesystem types currently mounted on the system. # findmnt -Dkerno fstype | sort -u Review the output. These filesystem types should either be excluded from the audit or if no longer needed, unmounted and disabled. Example output: devtmpfs ext4 tmpfs vfat 2. Run the following script to generate a list of all file system kernel modules currently installed on the system: #!/usr/bin/env bash { l_search="$(readlink -e /usr/lib/modules/ || readlink -e /lib/modules/)" a_module=() while IFS= read -r -d $'\0' l_module_dir; do if [ ! "$(basename "$l_module_dir")" = "nls" ]; then while IFS= read -r -d $'\0' l_module_file; do l_mname="$(basename "$l_module_file" | cut -d'.' -f1)" if [ -f "$l_module_file" ] && ! grep -Psiq -- '\b'"$l_mname"'\b' \ <<< "${a_module[*]}"; then a_module+=("$l_mname") fi done < <(find -L "$l_module_dir" -mindepth 1 -maxdepth 1 -type f - print0) fi done < <(find "$l_search"/**/kernel/fs/ -mindepth 1 -maxdepth 1 -type d ! -empty -print0) printf '%s\n' "" "${a_module[@]}" } The output is a list of the kernel modules included in the /usr/lib/modules/{KERNEL_VERSION}/kernel/fs/ or /lib/modules/{KERNEL_VERSION}/kernel/fs/ directories. This list has been sorted to be unique values, ignore items in the nls directory, and added to an array called a_module. 3. Run the following command to generate a list of modules currently loaded into the kernel: Page 56 Internal Only - General # lsmod 4. compare the output from the list generated in step 2 to the list of loaded modules generated by the lsmod command in step 3. Any module appearing in both lists is currently loaded into the kernel. Review these to verify they are needed and approved by local site policy 5. Run the following command to generate a list of modules that are set to be Deny Listed: blacklist {MODULE_NAME}, and/or set be be not loadable: install {MODULE_NAME} /bin/false or install {MODULE_NAME} /bin/true: # modprobe --showconfig | grep -Pi -- '^\h*(blacklist|install)\h+' Page 57 Internal Only - General 6. Verify all modules in the output from the list generated in step 2 are both Deny Listed: blacklist {MODULE_NAME} and set to be not loadable: install {MODULE_NAME} /bin/false or install {MODULE_NAME} /bin/true. Audit Script: #!/usr/bin/env bash { a_check=() a_output=() a_module=() a_output2=() a_output3=() l_search="$(readlink -e /usr/lib/modules/ || readlink -e /lib/modules/)" IFS=$'\n' read -r -d '' -a a_mounted < <(findmnt -Dkerno fstype \ | sort -u && printf '\0' ) IFS=$'\n' read -r -d '' -a a_lsmod < <(lsmod | awk '{print $1}' && printf '\0' ) IFS=$'\n' read -r -d '' -a a_showconfig < <(modprobe --showconfig | \ grep -Pi -- '^\h*(blacklist|install)\h+' && printf '\0') while IFS= read -r -d $'\0' l_module_dir; do if [ ! "$(basename "$l_module_dir")" = "nls" ]; then while IFS= read -r -d $'\0' l_module_file; do l_mname="$(basename "$l_module_file" | cut -d'.' -f1)" if [ -f "$l_module_file" ] && ! grep -Psiq -- '\b'"$l_mname"'\b' <<< "${a_module[*]}"; then a_module+=("$l_mname") fi done < <(find -L "$l_module_dir" -mindepth 1 -maxdepth 1 -type f -print0) fi done < <(find "$l_search"/**/kernel/fs/ -mindepth 1 -maxdepth 1 -type d ! -empty - print0) for l_module in "${a_module[@]}"; do if grep -Psoiq -- '\b'"$l_module"'\b' <<< "${a_mounted[*]}"; then a_output+=(" - \"$l_module\"") elif grep -Psoiq -- '\b'"$l_module"'\b' <<< "${a_lsmod[*]}"; then a_output2+=(" - \"$l_module\"") elif ! grep -Psioq -- '\binstall\h+'"${l_module//-/_}"'\h+\H+\b' <<< "${a_showconfig[*]}" || \ ! grep -Psioq -- '\bblacklist\h+'"${l_module//-/_}"'\b' <<< "${a_showconfig[*]}"; then a_output3+=(" - \"$l_module\"") fi done [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output[@]}\" kernel modules currently mounted:" "${a_output[@]}" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output2[@]}\" kernel modules currently loaded:" "${a_output2[@]}" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output3[@]}\" Kernel modules currently loadable:" "${a_output3[@]}" } WARNING: disabling or denylisting filesystem modules that are in use on the system may be FATAL. It is extremely important to thoroughly review this list. Page 58 Internal Only - General Remediation: - IF - the module is available in the running kernel: • Unload the filesystem kernel module from the kernel • Create a file ending in .conf with install filesystem kernel modules /bin/false in the /etc/modprobe.d/ directory • Create a file ending in .conf with deny list filesystem kernel modules in the /etc/modprobe.d/ directory WARNING: unloading, disabling or denylisting filesystem modules that are in use on the system may be FATAL. It is extremely important to thoroughly review the filesystems returned by the audit before following the remediation procedure. Example of unloading the gfs2kernel module: modprobe -r gfs2 2>/dev/null rmmod gfs2 2>/dev/null Example of fully disabling the gfs2 kernel module: printf '%s\n' "" "blacklist gfs2" "install gfs2 /bin/false" >> /etc/modprobe.d/gfs2.conf Note: • Disable a kernel module by modifying the command above for each unused filesystem kernel module • The example gfs2 must be updated with the appropriate module name for the command or example script bellow to run correctly. Below is an example script that can be modified to use on various filesystem kernel modules manual remediation process: Example Script Page 59 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=(); l_dl="" # Initialize arrays and clear variables l_mod_name="gfs2" # set module name l_mod_type="fs" # set module type l_mod_path="$(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)" f_module_fix() { l_dl="y" # Set to ignore duplicate checks a_showconfig=() # Create array with modprobe output while IFS= read -r l_showconfig; do a_showconfig+=("$l_showconfig") done < <(modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+'"${l_mod_name//-/_}"'\b') if lsmod | grep "$l_mod_name" &> /dev/null; then # Check if the module is currently loaded a_output2+=(" - unloading kernel module: \"$l_mod_name\"") modprobe -r "$l_mod_name" 2>/dev/null; rmmod "$l_mod_name" 2>/dev/null fi if ! grep -Pq -- '\binstall\h+'"${l_mod_name//- /_}"'\h+(\/usr)?\/bin\/(true|false)\b' <<< "${a_showconfig[*]}"; then a_output2+=(" - setting kernel module: \"$l_mod_name\" to \"$(readlink -f /bin/false)\"") printf '%s\n' "install $l_mod_name $(readlink -f /bin/false)" >> /etc/modprobe.d/"$l_mod_name".conf fi if ! grep -Pq -- '\bblacklist\h+'"${l_mod_name//-/_}"'\b' <<< "${a_showconfig[*]}"; then a_output2+=(" - denylisting kernel module: \"$l_mod_name\"") printf '%s\n' "blacklist $l_mod_name" >> /etc/modprobe.d/"$l_mod_name".conf fi } for l_mod_base_directory in $l_mod_path; do # Check if the module exists on the system if [ -d "$l_mod_base_directory/${l_mod_name/-/\/}" ] && [ -n "$(ls -A "$l_mod_base_directory/${l_mod_name/-/\/}")" ]; then a_output3+=(" - \"$l_mod_base_directory\"") [[ "$l_mod_name" =~ overlay ]] && l_mod_name="${l_mod_name::-2}" [ "$l_dl" != "y" ] && f_module_fix else echo -e " - kernel module: \"$l_mod_name\" doesn't exist in \"$l_mod_base_directory\"" fi done [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " -- INFO --" " - module: \"$l_mod_name\" exists in:" "${a_output3[@]}" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" || printf '%s\n' "" " - No changes needed" printf '%s\n' "" " - remediation of kernel module: \"$l_mod_name\" complete" "" } Page 60 Internal Only - General References: 1. https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=filesystem CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 61 Internal Only - General 1.1.2 Configure Filesystem Partitions Directories that are used for system-wide functions can be further protected by placing them on separate partitions. This provides protection for resource exhaustion and enables the use of mounting options that are applicable to the directory's intended use. Users' data can be stored on separate partitions and have stricter mount options. A user partition is a filesystem that has been established for use by the users and does not contain software for system operations. The recommendations in this section are easier to perform during initial system installation. If the system is already installed, it is recommended that a full backup be performed before repartitioning the system. Note: -IF- you are repartitioning a system that has already been installed (This may require the system to be in single-user mode): • Mount the new partition to a temporary mountpoint e.g. mount /dev/sda2 /mnt • Copy data from the original partition to the new partition. e.g. cp -a /var/tmp/* /mnt • Verify that all data is present on the new partition. e.g. ls -la /mnt • Unmount the new partition. e.g. umount /mnt • Remove the data from the original directory that was in the old partition. e.g. rm -Rf /var/tmp/* Otherwise it will still consume space in the old partition that will be masked when the new filesystem is mounted. • Mount the new partition to the desired mountpoint. e.g. mount /dev/sda2 /var/tmp • Update /etc/fstab with the new mountpoint. e.g. /dev/sda2 /var/tmp xfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Page 62 Internal Only - General 1.1.2.1 Configure /tmp The /tmp directory is a world-writable directory used to store data used by the system and user applications for a short period of time. This data should have no expectation of surviving a reboot, as this directory is intended to be emptied after each reboot. Page 63 Internal Only - General 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /tmp directory is a world-writable directory used for temporary storage by all users and some applications. Note: If an entry for /tmp exists in /etc/fstab it will take precedence over entries in a systemd unit file. There is an exception to this when a system is diskless and connected to iSCSI, entries in /etc/fstab may not take precedence over a systemd unit file. Rationale: Making /tmp its own file system allows an administrator to set additional mount options such as the noexec option on the mount, making /tmp useless for an attacker to install executable code. It would also prevent an attacker from establishing a hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link would be broken, and the attacker would have his own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. This can be accomplished by either mounting tmpfs to /tmp, or creating a separate partition for /tmp. Impact: By design files saved to /tmp should have no expectation of surviving a reboot of the system. tmpfs is ram based and all files stored to tmpfs will be lost when the system is rebooted. If files need to be persistent through a reboot, they should be saved to /var/tmp not /tmp. Since the /tmp directory is intended to be world-writable, there is a risk of resource exhaustion if it is not bound to tmpfs or a separate partition. Running out of /tmp space is a problem regardless of what kind of filesystem lies under it, but in a configuration where /tmp is not a separate file system it will essentially have the whole disk available, as the default installation only creates a single / partition. On the other hand, a RAM-based /tmp (as with tmpfs) will almost certainly be much smaller, which can lead to applications filling up the filesystem much more easily. Another alternative is to create a dedicated partition for /tmp from a separate volume or disk. One of the downsides of a disk-based dedicated partition is that it will be slower than tmpfs which is RAM-based. Page 64 Internal Only - General Audit: Run the following command and verify the output shows that /tmp is mounted. Particular requirements pertaining to mount options are covered in ensuing sections. # findmnt -kn /tmp Example output: /tmp tmpfs tmpfs rw,nosuid,nodev,noexec Ensure that systemd will mount the /tmp partition at boot time. # systemctl is-enabled tmp.mount Example output: generated Verify output is not masked or disabled. Note: By default, systemd will output generated if there is an entry in /etc/fstab for /tmp. This just means systemd will use the entry in /etc/fstab instead of its default unit file configuration for /tmp. Remediation: First ensure that systemd is correctly configured to ensure that /tmp will be mounted at boot time. # systemctl unmask tmp.mount For specific configuration requirements of the /tmp mount for your environment, modify /etc/fstab. Example of using tmpfs with specific mount options: tmpfs /tmp tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 0 Note: the size=2G is an example of setting a specific size for tmpfs. Example of using a volume or disk with specific mount options. The source location of the volume or disk will vary depending on your environment: /tmp defaults,nodev,nosuid,noexec 0 0 References: 1. https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems/ 2. https://www.freedesktop.org/software/systemd/man/systemd-fstab-generator.html 3. https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt 4. CCI-000366 5. NIST SP 800-53 :: CM-6 b 6. NIST SP 800-53A :: CM-6.1 (iv) 7. STIG ID: RHEL-08-010543 | RULE ID: SV-230295r1017106 | CAT II 8. STIG ID: RHEL-09-231015 | RULE ID: SV-257844r1044918 | CAT II 9. STIG ID: ALMA-09-025540 | RULE ID: SV-269305r1050187 | CAT II Additional Information: /tmp can be configured to use tmpfs. Page 65 Internal Only - General tmpfs puts everything into the kernel internal caches and grows and shrinks to accommodate the files it contains and is able to swap unneeded pages out to swap space. It has maximum size limits which can be adjusted on the fly via mount -o remount. Since tmpfs lives completely in the page cache and on swap, all tmpfs pages will be shown as "Shmem" in /proc/meminfo and "Shared" in free. Notice that these counters also include shared memory. The most reliable way to get the count is using df and du. tmpfs has three mount options for sizing: • size: The limit of allocated bytes for this tmpfs instance. The default is half of your physical RAM without swap. If you oversize your tmpfs instances the machine will deadlock since the OOM handler will not be able to free that memory. • nr_blocks: The same as size, but in blocks of PAGE_SIZE. • nr_inodes: The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, whichever is the lower. These parameters accept a suffix k, m or g and can be changed on remount. The size parameter also accepts a suffix % to limit this tmpfs instance to that percentage of your physical RAM. The default, when neither size nor nr_blocks is specified, is size=50%. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 66 Internal Only - General 1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /tmp filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /tmp. Audit: - IF - a separate partition exists for /tmp, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /tmp | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040123 | RULE ID: SV-230511r958804 | CAT II 4. STIG ID: RHEL-09-231125 | RULE ID: SV-257866r958804 | CAT II 5. STIG ID: ALMA-09-026860 | RULE ID: SV-269317r1050199 | CAT II Additional Information: See the fstab(5) manual page for more information. Page 67 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 68 Internal Only - General 1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /tmp. Audit: - IF - a separate partition exists for /tmp, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /tmp | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040124 | RULE ID: SV-230512r958804 | CAT II 4. STIG ID: RHEL-09-231135 | RULE ID: SV-257868r958804 | CAT II 5. STIG ID: ALMA-09-027080 | RULE ID: SV-269319r1050201 | CAT II Additional Information: See the fstab(5) manual page for more information. Page 69 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 70 Internal Only - General 1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot run executable binaries from /tmp. Impact: Setting the noexec option on /tmp may prevent installation and/or updating of some 3rd party software. Audit: - IF - a separate partition exists for /tmp, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /tmp | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp Page 71 Internal Only - General References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040125 | RULE ID: SV-230513r958804 | CAT II 4. STIG ID: RHEL-09-231130 | RULE ID: SV-257867r958804 | CAT II 5. STIG ID: ALMA-09-026970 | RULE ID: SV-269318r1050200 | CAT II Additional Information: See the fstab(5) manual page for more information. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 72 Internal Only - General 1.1.2.2 Configure /dev/shm The /dev/shm directory is a world-writable directory that can function as shared memory that facilitates inter process communication (IPC) Page 73 Internal Only - General 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /dev/shm directory is a world-writable directory that can function as shared memory that facilitates inter process communication (IPC). Rationale: Making /dev/shm its own file system allows an administrator to set additional mount options such as the noexec option on the mount, making /dev/shm useless for an attacker to install executable code. It would also prevent an attacker from establishing a hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link would be broken and the attacker would have his own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. This can be accomplished by mounting tmpfs to /dev/shm. Impact: Since the /dev/shm directory is intended to be world-writable, there is a risk of resource exhaustion if it is not bound to a separate partition. /dev/shm utilizing tmpfs can be resized using the size={size} parameter in the relevant entry in /etc/fstab. Audit: - IF - /dev/shm is to be used on the system, run the following command and verify the output shows that /dev/shm is mounted. Particular requirements pertaining to mount options are covered in ensuing sections. # findmnt -kn /dev/shm Example output: /dev/shm tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,seclabel Page 74 Internal Only - General Remediation: For specific configuration requirements of the /dev/shm mount for your environment, modify /etc/fstab. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 0 References: 1. https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems/ 2. https://www.freedesktop.org/software/systemd/man/systemd-fstab-generator.html 3. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 75 Internal Only - General 1.1.2.2.2 Ensure nodev option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /dev/shm filesystem is not intended to support devices, set this option to ensure that users cannot attempt to create special devices in /dev/shm partitions. Audit: - IF - a separate partition exists for /dev/shm, verify that the nodev option is set. # findmnt -kn /dev/shm | grep -v 'nodev' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /dev/shm partition. See the fstab(5) manual page for more information. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040120 | RULE ID: SV-230508r958804 | CAT II 4. STIG ID: RHEL-09-231110 | RULE ID: SV-257863r958804 | CAT II 5. STIG ID: ALMA-09-026530 | RULE ID: SV-269314r1050196 | CAT II Additional Information: Some distributions mount /dev/shm through other means and require /dev/shm to be added to /etc/fstab even though it is already being mounted on boot. Others may Page 76 Internal Only - General configure /dev/shm in other locations and may override /etc/fstab configuration. Consult the documentation appropriate for your distribution. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 77 Internal Only - General 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Setting this option on a file system prevents users from introducing privileged programs onto the system and allowing non-root users to execute them. Audit: - IF - a separate partition exists for /dev/shm, verify that the nosuid option is set. # findmnt -kn /dev/shm | grep -v 'nosuid' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /dev/shm partition. See the fstab(5) manual page for more information. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040121 | RULE ID: SV-230509r958804 | CAT II 4. STIG ID: RHEL-09-231120 | RULE ID: SV-257865r1044946 | CAT II 5. STIG ID: ALMA-09-026750 | RULE ID: SV-269316r1050198 | CAT II Additional Information: Some distributions mount /dev/shm through other means and require /dev/shm to be added to /etc/fstab even though it is already being mounted on boot. Others may Page 78 Internal Only - General configure /dev/shm in other locations and may override /etc/fstab configuration. Consult the documentation appropriate for your distribution. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 79 Internal Only - General 1.1.2.2.4 Ensure noexec option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Setting this option on a file system prevents users from executing programs from shared memory. This deters users from introducing potentially malicious software on the system. Audit: - IF - a separate partition exists for /dev/shm, verify that the noexec option is set. # findmnt -kn /dev/shm | grep -v 'noexec' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /dev/shm partition. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040122 | RULE ID: SV-230510r958804 | CAT II 4. STIG ID: RHEL-09-231115 | RULE ID: SV-257864r958804 | CAT II 5. STIG ID: ALMA-09-026640 | RULE ID: SV-269315r1050197 | CAT II Page 80 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 81 Internal Only - General 1.1.2.3 Configure /home Please note that home directories can be mounted anywhere and are not necessarily restricted to /home, nor restricted to a single location, nor is the name restricted in any way. Finding user home directories can be done by looking in /etc/passwd, looking over the mounted file systems with mount or querying the relevant database with getent. The following script can be run to find user's home directories: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed - rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3>='"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 != 65534) && $(NF) ~ pat) {print $1 " - " $6}' /etc/passwd } Page 82 Internal Only - General 1.1.2.3.1 Ensure separate partition exists for /home (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /home directory is used to support disk storage needs of local users. Rationale: The default installation only creates a single / partition. Since the /home directory contains user generated data, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. In addition, other operations on the system could fill up the disk unrelated to /home and impact all local users. Configuring /home as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. In the case of /home options such as usrquota/grpquota may be considered to limit the impact that users can have on each other with regards to disk resource exhaustion. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /home contains user data, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /home is mounted: # findmnt -kn /home /home /dev/sdb ext4 rw,nosuid,nodev,relatime,seclabel Page 83 Internal Only - General Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /home. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 Additional Information: When modifying /home it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 84 Internal Only - General 1.1.2.3.2 Ensure nodev option set on /home partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /home filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /home. Audit: - IF - a separate partition exists for /home, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /home | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /home. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /home partition. Example: /home defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /home with the configured options: # mount -o remount /home References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists v7 Protect all information stored on systems with file system, network share, ● ● ● claims, application, or database specific access control lists. These controls will Page 85 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Page 86 Internal Only - General 1.1.2.3.3 Ensure nosuid option set on /home partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /home filesystem is only intended for user file storage, set this option to ensure that users cannot create setuid files in /home. Audit: - IF - a separate partition exists for /home, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /home | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /home. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /home partition. Example: /home defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /home with the configured options: # mount -o remount /home References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists v7 Protect all information stored on systems with file system, network share, ● ● ● claims, application, or database specific access control lists. These controls will Page 87 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Page 88 Internal Only - General 1.1.2.4 Configure /var The /var directory is used by daemons and other system services to temporarily store dynamic data. Some directories created by these processes may be world-writable. Page 89 Internal Only - General 1.1.2.4.1 Ensure separate partition exists for /var (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var directory is used by daemons and other system services to temporarily store dynamic data. Some directories created by these processes may be world-writable. Rationale: The reasoning for mounting /var on a separate partition is as follows. The default installation only creates a single / partition. Since the /var directory may contain world writable files and directories, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system. In addition, other operations on the system could fill up the disk unrelated to /var and cause unintended behavior across the system as the disk is full. See man auditd.conf for details. Configuring /var as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. An example of exploiting /var may be an attacker establishing a hard-link to a system setuid program and waiting for it to be updated. Once the program is updated, the hard-link can be broken and the attacker would have their own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var is mounted. Example: # findmnt -kn /var /var /dev/sdb ext4 rw,nosuid,nodev,relatime,seclabel Page 90 Internal Only - General Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 3. RHEL 8 STIG Vul ID: V-244529 4. RHEL 8 STIG Rule ID: SV-244529r902737 Additional Information: When modifying /var it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 91 Internal Only - General 1.1.2.4.2 Ensure nodev option set on /var partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var. Audit: - IF - a separate partition exists for /var, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var partition. Example: /var defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /var with the configured options: # mount -o remount /var References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists v7 Protect all information stored on systems with file system, network share, ● ● ● claims, application, or database specific access control lists. These controls will Page 92 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Page 93 Internal Only - General 1.1.2.4.3 Ensure nosuid option set on /var partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var filesystem is only intended for variable files such as logs, set this option to ensure that users cannot create setuid files in /var. Audit: - IF - a separate partition exists for /var, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var partition. Example: /var defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /var with the configured options: # mount -o remount /var References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists v7 Protect all information stored on systems with file system, network share, ● ● ● claims, application, or database specific access control lists. These controls will Page 94 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Page 95 Internal Only - General 1.1.2.5 Configure /var/tmp The /var/tmp directory is a world-writable directory used for temporary storage by all users and some applications. Temporary files residing in /var/tmp are to be preserved between reboots. Page 96 Internal Only - General 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var/tmp directory is a world-writable directory used for temporary storage by all users and some applications. Temporary files residing in /var/tmp are to be preserved between reboots. Rationale: The default installation only creates a single / partition. Since the /var/tmp directory is world-writable, there is a risk of resource exhaustion. In addition, other operations on the system could fill up the disk unrelated to /var/tmp and cause potential disruption to daemons as the disk is full. Configuring /var/tmp as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/tmp is mounted. Example: # findmnt -kn /var/tmp /var/tmp /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/tmp. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ Page 97 Internal Only - General 2. NIST SP 800-53 Rev. 5: CM-7 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-244529 5. RHEL 8 STIG Rule ID: SV-244529r902737 Additional Information: When modifying /var/tmp it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 98 Internal Only - General 1.1.2.5.2 Ensure nodev option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/tmp filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/tmp | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230520 5. RHEL 8 STIG Rule ID: SV-230520r854061 Page 99 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 100 Internal Only - General 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/tmp | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230521 5. RHEL 8 STIG STIG ID: RHEL-08-040133 Page 101 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 102 Internal Only - General 1.1.2.5.4 Ensure noexec option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot run executable binaries from /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/tmp | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230522 5. RHEL 8 STIG Rule ID: SV-230522r854063 Page 103 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 104 Internal Only - General 1.1.2.6 Configure /var/log The /var/log directory is used by system services to store log data. Page 105 Internal Only - General 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var/log directory is used by system services to store log data. Rationale: The default installation only creates a single / partition. Since the /var/log directory contains log files which can grow quite large, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. Configuring /var/log as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attackers ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /var/log contains log files, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing, or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/log is mounted: # findmnt -kn /var/log /var/log /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/log . For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. Page 106 Internal Only - General References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5:: CM-6 b CM-7 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-230293 5. RHEL 8 STIG Rule ID: SV-230293r902720 Additional Information: When modifying /var/log it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multiuser mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 107 Internal Only - General 1.1.2.6.2 Ensure nodev option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/log filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/log | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230514 5. RHEL 8 STIG Rule ID: SV-230514r854055 Page 108 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 109 Internal Only - General 1.1.2.6.3 Ensure nosuid option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/log filesystem is only intended for log files, set this option to ensure that users cannot create setuid files in /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/log | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230515 5. RHEL 8 STIG Rule ID: SV-230515r854056 Page 110 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 111 Internal Only - General 1.1.2.6.4 Ensure noexec option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/log filesystem is only intended for log files, set this option to ensure that users cannot run executable binaries from /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/log | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230516 5. RHEL 8 STIG Rule ID: SV-230516r854057 Page 112 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 113 Internal Only - General 1.1.2.7 Configure /var/log/audit The auditing daemon, auditd, stores log data in the /var/log/audit directory. Page 114 Internal Only - General 1.1.2.7.1 Ensure separate partition exists for /var/log/audit (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditing daemon, auditd, stores log data in the /var/log/audit directory. Rationale: The default installation only creates a single / partition. Since the /var/log/audit directory contains the audit.log file which can grow quite large, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. In addition, other operations on the system could fill up the disk unrelated to /var/log/audit and cause auditd to trigger its space_left_action as the disk is full. See man auditd.conf for details. Configuring /var/log/audit as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /var/log/audit contains audit logs, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/log/audit is mounted: # findmnt -kn /var/log/audit /var/log/audit /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Page 115 Internal Only - General Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/log/audit. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-230294 5. RHEL 8 STIG Rule ID: SV-230294r627750 Additional Information: When modifying /var/log/audit it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 116 Internal Only - General 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/log/audit filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/log/audit | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Revision 5 :: CM-7 (2) 3. STIG ID: RHEL-08-040129 | RULE ID: SV-230517r958804 | CAT II 4. STIG ID: RHEL-09-231175 | RULE ID: SV-257876r958804 | CAT II 5. STIG ID: ALMA-09-027190 | RULE ID: SV-269320r1050202 | CAT II Page 117 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 118 Internal Only - General 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/log/audit filesystem is only intended for variable files such as logs, set this option to ensure that users cannot create setuid files in /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/log/audit | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. STIG ID: RHEL-08-040130 | RULE ID: SV-230518r958804 | CAT II 5. STIG ID: RHEL-09-231170 | RULE ID: SV-257875r958804 | CAT II Page 119 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 120 Internal Only - General 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/log/audit filesystem is only intended for audit logs, set this option to ensure that users cannot run executable binaries from /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/log/audit | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. STIG ID: RHEL-08-040131 | RULE ID: SV-230519r958804 | CAT II 5. STIG ID: RHEL-09-231165 | RULE ID: SV-257874r958804 | CAT II Page 121 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 122 Internal Only - General 1.2 Package Management Patch management procedures may vary widely between enterprises. Large enterprises may choose to install a local updates server that can be used in place of their distributions servers, whereas a single deployment of a system may prefer to get updates directly. Updates can be performed automatically or manually, depending on the site's policy for patch management. Organizations may prefer to test patches against their environment on a non-production system before rolling out to production. Outdated software is vulnerable to cyber criminals and hackers. Software updates help reduce the risk to your organization. The release of software update notes often reveals the patched exploitable entry points to the public. Public knowledge of these exploits can make your organization more vulnerable to malicious actors attempting to gain entry to your system's data. Software updates often offer new and improved features and speed enhancements. For the purpose of this benchmark, the requirement is to ensure that a patch management process is defined and maintained, the specifics of which are left to the organization. Page 123 Internal Only - General 1.2.1 Configure Package Repositories Patch management procedures may vary widely between enterprises. Large enterprises may choose to install a local updates server that can be used in place of their distributions servers, whereas a single deployment of a system may prefer to get updates directly. Updates can be performed automatically or manually, depending on the site's policy for patch management. Organizations may prefer to test patches against their environment on a non-production system before rolling out to production. Outdated software is vulnerable to cyber criminals and hackers. Software updates help reduce the risk to your organization. The release of software update notes often reveals the patched exploitable entry points to the public. Public knowledge of these exploits can leave your organization more vulnerable to malicious actors attempting to gain access to your system's data. Note: Creation of an appropriate patch management policy is left to the organization. Page 124 Internal Only - General 1.2.1.1 Ensure the source.list and .source files use the Signed-By option (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sources.list - List of configured APT data sources The source list /etc/apt/sources.list and the files contained in /etc/apt/sources.list.d/ are designed to support any number of active sources and a variety of source media. Signed-By (signed-by) is an option to require a repository to pass apt-secure(8) verification with a certain set of keys rather than all trusted keys apt has configured. It is specified as a list of absolute paths to keyring files (have to be accessible and readable for the _apt system user, so ensure everyone has read-permissions on the file) and fingerprints of keys to select from these keyrings. The recommended locations for keyrings are /usr/share/keyrings for keyrings managed by packages, and /etc/apt/keyrings for keyrings managed by the system operator. If no keyring files are specified, the default is the trusted.gpg keyring and all keyrings in the trusted.gpg.d/ directory. If no fingerprint is specified all keys in the keyrings are selected. A fingerprint will accept also all signatures by a subkey of this key, if this isn't desired an exclamation mark (!) can be appended to the fingerprint to disable this behaviour. The option defaults to the value of the option with the same name if set in the previously acquired Release file of this repository (only fingerprints can be specified there through). Otherwise, all keys in the trusted keyrings are considered valid signers for this repository. The option may also be set directly to an embedded GPG public key block. Rationale: Verifying that updates originate from a trusted and authenticated source helps mitigate the risk of spoofing attacks, which could otherwise lead to the inadvertent installation of malicious or compromised software. Impact: apt-key list is deprecated. Manage keyring files in trusted.gpg.d instead (see apt- key(8)). With the deprecation of apt-key it is recommended to use the Signed-By option in sources.list to require a repository to pass apt-secure(8) verification with a certain set of keys rather than all trusted keys apt has configured. It is important to list sources in order of preference, with the most preferred source listed first. Typically, this will result in sorting by speed from fastest to slowest (CD-ROM followed by hosts on a local network, followed by distant Internet hosts, for example). Page 125 Internal Only - General Audit: Run the following command and verify that the file /etc/apt/sources.list and files ending .list and .sources in the /etc/apt/sources.list.d/ directory use the Signed-By option: # grep -PRLs -- '^([^#\n\r]+)?\bSigned-By\b' /etc/apt/sources.list /etc/apt/sources.list.d/*.{list,sources} Nothing should be returned. Remediation: Update the file sources.list and any .sources files found in the /etc/apt/sources.list.d/ directory in accordance with site policy. Note: • The suggested filename for new systems is /etc/apt/sources.list.d/vendor.sources, where vendor is the result of dpkg-vendor --query Vendor | tr A-Z a-z, in deb822-style format. For example, Ubuntu uses /etc/apt/sources.list.d/ubuntu.sources. • It is important to list sources in order of preference, with the most preferred source listed first. Typically, this will result in sorting by speed from fastest to slowest (CD-ROM followed by hosts on a local network, followed by distant Internet hosts, for example). References: 1. NIST SP 800-53 Rev. 5: SI-2 2. https://manpages.debian.org/trixie/apt/sources.list.5.en.html 3. https://manpages.debian.org/trixie/gpg/gpg.1.en.html Page 126 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 7.3 Perform Automated Operating System Patch v8 Management ● ● ● Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 7.4 Perform Automated Application Patch Management v8 Perform application updates on enterprise assets through automated patch ● ● ● management on a monthly, or more frequent, basis. 3.4 Deploy Automated Operating System Patch Management Tools v7 Deploy automated software update tools in order to ensure that the operating ● ● ● systems are running the most recent security updates provided by the software vendor. 3.5 Deploy Automated Software Patch Management Tools v7 Deploy automated software update tools in order to ensure that third-party ● ● ● software on all systems is running the most recent security updates provided by the software vendor. Page 127 Internal Only - General 1.2.1.2 Ensure weak dependencies are configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The Debian packaging specification allows for 3 levels of dependencies to be declared: hard dependencies (Requires) for packages which must be installed for a minimal installation of the application to function weak dependencies (Recommends) for packages which provide additional features, but which are not required for a minimal installation to function hints (Suggests) for packages which offer add-ons which might be useful. Rationale: Unless a system specifically requires the additional capabilities provides by the weak dependencies, it is recommended that the packages are not installed to reduce the potential attack surface. Audit: Run the following command and verify that the APT options for weak dependencies are disabled: # /usr/bin/apt-config dump | /usr/bin/grep "APT::Install-" Verify the output matches the following APT::Install-Recommends "0"; APT::Install-Suggests "0"; Note: If no output is returned, this should be considered a failure as the default behavior is to install packages marked as recommended. Remediation: Create a file under /etc/apt/apt.conf.d/ to disable the installation of weak dependencies: # printf '%s\n%s\n' "" 'APT::Install-Recommends "0";' 'APT::Install-Suggests "0";' > /etc/apt/apt.conf.d/60-no-weak-dependencies Note: All configuration files under /etc/apt/apt.conf.d/ are sorted in lexicographic order and where conflicting settings exist the last one will take precedence. Default Value: APT::Install-Recommends "1"; APT::Install-Suggests "0"; Page 128 Internal Only - General 1.2.1.3 Ensure access to gpg key files are configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: GPG key files are cryptographic keys used by APT to verify the authenticity and integrity of software packages. Each key ensures that packages come from a trusted source and have not been tampered with. These keys are typically stored in keyring directories /etc/apt/trusted.gpg.d or /usr/share/keyrings and referenced in repository configuration files using the signed-by option for secure package verification. Rationale: Impact: The apt-key command is deprecated, and you should manage keyring files individually in the trusted.gpg.d directory instead. This change is due to security concerns with the way apt-key works, as it adds keys to the /etc/apt/trusted.gpg file, which can lead to potential security issues. Audit: 1. Run the following script to verify all .gpg key files in /usr/share/keyrings/ and /etc/apt/trusted.gpg.d are mode 0644 or more restrictive, are owned by the user root, and group owned by the group root: #! /usr/bin/env bash { while IFS= read -r -d $'\0' l_file; do stat -Lc 'File: %n Mode: (%#a) User: (%U) Group: (%G)' "$l_file" done < <(find -L /usr/share/keyrings/ /etc/apt/trusted.gpg.d/ \ -mount -xdev -type f \( ! -user root -o ! -group root -o -perm /133 \) \ -name '*gpg' -print0) } Nothing should be returned. 2. Run the following script to verify key files ending in .list or .sources, that include the signed-by option, are mode 0644 or more restrictive, are owned by the user root, and group owned by the group root: Page 129 Internal Only - General #!/usr/bin/env bash { while IFS= read -r -d $'\0' l_file; do grep -Psq -- '^([^#\n\r]+)?\bSigned-By\b' "$l_file" && \ stat -Lc 'File: %n Mode: (%#a) User: (%U) Group: (%G)' "$l_file" done < <(find -L /etc/apt/sources.list.d/ -mount -xdev -type f \ \( ! -user root -o ! -group root -o -perm /133 \) \ \( -name '*.list' -o -name '*.sources' \) -print0) } Nothing should be returned. Remediation: Run the following commands to update the access to any file(s) returned in the audit steps above: # chown root:root "/absolute/path/to/file" # chmod u-x,go-wx "/absolute/path/to/file" Example # chown root:root /usr/share/keyrings/debian-archive-trixie-security- automatic.gpg # chmod u-x,go-wx /usr/share/keyrings/debian-archive-trixie-security- automatic.gpg Note: APT first checks keys specified with the signed-by option in a repository's .sources or .list files. If no key is specified there, it falls back to administrator- managed keyrings in /etc/apt/trusted.gpg.d, then system-wide keyrings in /usr/share/keyrings. Default Value: Access: (644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. https://ftp-master.debian.org/keys.html 2. https://wiki.debian.org/SecureApt#All_about_secure_apt 3. https://manpages.debian.org/stretch/apt/apt-secure.8.en.html Page 130 Internal Only - General 1.2.1.4 Ensure access to /etc/apt/trusted.gpg.d directory is configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: The /etc/apt/trusted.gpg.d directory stores individual GPG key files that APT uses to verify the authenticity of packages and repositories. Rationale: Impact: A non-privileged user with write access to /etc/apt/trusted.gpg.d can compromise the chain of trust by adding new public keys to APT trusted keys configuration. Audit: Run the following command and verify /etc/apt/trusted.gpg.d Uid and Gid are both 0/root and access is set to 0755 or more secure # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/apt/trusted.gpg.d Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set /etc/apt/trusted.gpg.d Uid and Gid to 0/root and access to 0755 or more restrictive: # chown root:root /etc/apt/trusted.gpg.d # chmod u=rwx,g=rx,o=rx /etc/apt/trusted.gpg.d Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Page 131 Internal Only - General 1.2.1.5 Ensure access to /etc/apt/auth.conf.d directory is configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: /etc/apt/auth.conf.d contains .conf files with credentials to access APT private repositories. Rationale: The /etc/apt/auth.conf.d directory contains APT .conf files which should have restricted access because they control how the package manager runs as root and may contain sensitive information. If writable or readable by non-root users, they could be altered to run malicious commands or expose credentials. Audit: Run the following command and verify /etc/apt/auth.conf.d Uid and Gid are both 0/root and access is 0755 or more restrictive: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/apt/auth.conf.d Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set permissions on /etc/apt/auth.conf.d/ Uid and Gid are both 0/root and access is 0755 or more restrictive: # chown root:root /etc/apt/auth.conf.d # chmod u=rwx,g=rx,o=rx /etc/apt/auth.conf.d Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. https://manpages.debian.org/trixie/apt/apt_auth.conf.5.en.html Page 132 Internal Only - General 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/ directory is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Files in the /etc/apt/auth.conf.d directory contains .conf files with configured credentials for private APT repositories or proxy. Rationale: Access to the .conf files in the /etc/apt/auth.conf.d directory should be restricted to prevent secrets leakage of Login information needed to connect to a proxy or to download data from a repository. Audit: Run the following command and verify all .conf files in the /etc/apt/auth.conf.d/ directory Uid and Gid are both 0/root and mode 0640 or more restrictive: Run the following command: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/apt/auth.conf.d/* 2>/dev/null No output should be returned. Remediation: Run the following commands to set all .conf files in the /etc/apt/auth.conf.d/ directory Uid and Gid both to0/root and mode 0640: # chown root:root /etc/apt/auth.conf.d/* # chmod u-x,g-wx,o-rwx /etc/apt/auth.conf.d/* Default Value: The /etc/apt/auth.conf.d/ directory is empty References: 1. https://manpages.debian.org/testing/apt/apt_auth.conf.5.en.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.3 Configure Data Access Control Lists ● ● ● Configure data access control lists based on a user’s need to know. Apply data Page 133 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version access control lists, also known as access permissions, to local and remote file systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 134 Internal Only - General 1.2.1.7 Ensure access to /usr/share/keyrings directory is configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: The /usr/share/keyrings directory contains trusted gpg keyring files used by APT to verify package signatures from repositories. It provides a centralized, read-only location for system-wide keys that ensures package integrity and authenticity. Rationale: A non-root user should not be able to add or remove keys from this directory. Misconfiguring could allow a non-root user to add repositories containing malicious packages. Audit: Run the following command and verify /usr/share/keyrings Uid and Gid are both 0/root and access is 0755 or more restrictive: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /usr/share/keyrings Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set permissions on /usr/share/keyrings Uid and Gid both 0/root and access is 0755 or more restrictive: # chown root:root /usr/share/keyrings # chmod u=rwx,g=rx,o=rx /usr/share/keyrings Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Page 135 Internal Only - General 1.2.1.8 Ensure access to /etc/apt/sources.list.d directory is configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: The /etc/apt/sources.list.d directory provides a way to add sources.list entries in separate files. Rationale: /etc/apt/sources.list.d directory contains files with repositories to be used by APT. A non-root user should not be able to add or remove files from this directory. Misconfiguring could allow a non-root user to add repositories containing malicious packages. Audit: Run the following command and verify /etc/apt/sources.list.d Uid and Gid are both 0/root and access is set to 0755 or more restrictive: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/apt/sources.list.d Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following command to set permissions to /etc/apt/sources.list.d Uid and Gid to 0/root and access to 0755 or more restrictive: # chown root:root /etc/apt/sources.list.d # chmod u=rwx,g=rx,o=rx /etc/apt/sources.list.d Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. https://manpages.debian.org/stretch/apt/sources.list.5.en.html Page 136 Internal Only - General 1.2.1.9 Ensure access to files in /etc/apt/sources.list.d are configured (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Server Description: Files in the /etc/apt/sources.list.d directory provides a way to add sources.list entries in separate files. Rationale: Files in the /etc/apt/sources.list.d directory contain information about repositories to be used by APT. A non-root user should not be able to add or remove files from this directory. Misconfiguring could allow a non-root user to add repositories containing malicious packages. Audit: Run the following command and verify all files in the /etc/apt/sources.list.d directory Uid and Gid are both 0/root and access is set to 0644 or more restrictive: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/apt/sources.list.d/* Access: (644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following command to set permissions to /etc/apt/sources.list.d directory Uid and Gid to 0/root and access to 0644 or more restrictive: # chown root:root /etc/apt/sources.list.d/* # chmod u-x,go-wx /etc/apt/sources.list.d/* Default Value: No files under /etc/apt/sources.list.d References: 1. https://manpages.debian.org/stretch/apt/sources.list.5.en.html Page 137 Internal Only - General 1.2.2 Configure Package Updates Page 138 Internal Only - General 1.2.2.1 Ensure updates, patches, and additional security software are installed (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Periodically patches are released for included software either due to security flaws or to include additional functionality. Rationale: Newer patches may contain security enhancements that would not be available through the latest full update. As a result, it is recommended that the latest software patches be used to take advantage of the latest functionality. As with any software installation, organizations need to determine if a given update meets their requirements and verify the compatibility and supportability of any additional software against the update revision that is selected. Audit: Verify there are no updates or patches to install: # apt update # apt -s upgrade Check to make sure no system reboot is required: # if [ -f /var/run/reboot-required ]; then cat /var/run/reboot-required fi Page 139 Internal Only - General Remediation: Run the following commands to update all packages following local site policy guidance on applying updates and patches: Run the following command to update the system with the available patches and updates: # apt update Run one of the following commands to apply the updates and patches: # apt upgrade - OR - # apt dist-upgrade Note: When running the command apt dist-upgrade that apt has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist-upgrade command may remove some packages. Once the update process is complete, verify if a reboot is required to load changes: # if [ -f /var/run/reboot-required ]; then cat /var/run/reboot-required fi References: 1. NIST SP 800-53 Rev. 5: SI-2 Additional Information: Site policy may mandate a testing period before installation onto production systems for available updates. • upgrade - is used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list. Packages currently installed with new versions available are retrieved and upgraded; under no circumstances are currently installed packages removed, or packages not already installed retrieved and installed. New versions of currently installed packages that cannot be upgraded without changing the install status of another package will be left at their current version. An update must be performed first so that apt knows that new versions of packages are available. • dist-upgrade - in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist- upgrade command may remove some packages. The /etc/apt/sources.list file contains a list of locations from which to retrieve desired package files. See also apt_preferences(5) for a mechanism for overriding the general settings for individual packages. Page 140 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 7.3 Perform Automated Operating System Patch v8 Management ● ● ● Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 7.4 Perform Automated Application Patch Management v8 Perform application updates on enterprise assets through automated patch ● ● ● management on a monthly, or more frequent, basis. 3.4 Deploy Automated Operating System Patch Management Tools v7 Deploy automated software update tools in order to ensure that the operating ● ● ● systems are running the most recent security updates provided by the software vendor. 3.5 Deploy Automated Software Patch Management Tools v7 Deploy automated software update tools in order to ensure that third-party ● ● ● software on all systems is running the most recent security updates provided by the software vendor. Page 141 Internal Only - General 1.3 Mandatory Access Control Mandatory Access Control (MAC) provides an additional layer of access restrictions to processes on top of the base Discretionary Access Controls. By restricting how processes can access files and resources on a system the potential impact from vulnerabilities in the processes can be reduced. Impact: Mandatory Access Control limits the capabilities of applications and daemons on a system, while this can prevent unauthorized access the configuration of MAC can be complex and difficult to implement correctly preventing legitimate access from occurring. Page 142 Internal Only - General 1.3.1 Configure AppArmor AppArmor provides a Mandatory Access Control (MAC) system that greatly augments the default Discretionary Access Control (DAC) model. Under AppArmor MAC rules are applied by file paths instead of by security contexts as in other MAC systems. As such it does not require support in the filesystem and can be applied to network mounted filesystems for example. AppArmor security policies define what system resources applications can access and what privileges they can do so with. This automatically limits the damage that the software can do to files accessible by the calling user. The user does not need to take any action to gain this benefit. For an action to occur, both the traditional DAC permissions must be satisfied as well as the AppArmor MAC rules. The action will not be allowed if either one of these models does not permit the action. In this way, AppArmor rules can only make a system's permissions more restrictive and secure. References: 1. AppArmor Documentation: http://wiki.apparmor.net/index.php/Documentation 2. Ubuntu AppArmor Documentation: https://help.ubuntu.com/community/AppArmor 3. SUSE AppArmor Documentation: https://www.suse.com/documentation/apparmor/ Page 143 Internal Only - General 1.3.1.1 Ensure apparmor packages are installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AppArmor provides Mandatory Access Controls. Rationale: Without a Mandatory Access Control system installed only the default Discretionary Access Control system will be available. Audit: Run the following command to verify that apparmor is installed: # dpkg-query -s apparmor &>/dev/null && echo "apparmor is installed" apparmor is installed Run the following command to verify that apparmor-utils is installed: # dpkg-query -s apparmor-utils &>/dev/null && echo "apparmor-utils is installed" apparmor-utils is installed Remediation: Run the following command to install apparmor and apparmor-utils: # apt install apparmor apparmor-utils References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 144 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 145 Internal Only - General 1.3.1.2 Ensure AppArmor is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AppArmor is a kernel enhancement to confine programs to a limited set of resources. AppArmor is enabled by default. Note: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Rationale: AppArmor is a security mechanism and disabling it is not recommended. Audit: Run the following command to verify that AppArmor has not been disabled: # grep "^\s*linux" /boot/grub/grub.cfg | grep "apparmor=0" Nothing should be returned. Remediation: Edit /etc/default/grub of file in /etc/default/grub.d and remove the apparmor=0 parameters to the GRUB_CMDLINE_LINUX= line Run the following commands to update the grub2 configuration and reboot the system: # update-grub # reboot References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 146 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 147 Internal Only - General 1.3.1.3 Ensure all AppArmor Profiles are enforcing (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: AppArmor profiles define what resources applications are able to access. Rationale: Security configuration requirements vary from site to site. Some sites may mandate a policy that is stricter than the default policy, which is perfectly acceptable. This item is intended to ensure that any policies that exist on the system are activated. Impact: Setting AppArmor profiles to enforce mode removes the unconfined status, which can disrupt application operation. If these applications are required, the profile tuning may need to be tuned to allow necessary functionality. Audit: Run the following commands and verify that profiles are loaded and are not in complain mode: # apparmor_status | grep profiles Review output and ensure that profiles are loaded, and in enforce mode: 34 profiles are loaded. 34 profiles are in enforce mode. 0 profiles are in complain mode. 2 processes have profiles defined. Run the following command and verify that no processes are unconfined: apparmor_status | grep processes Review the output and ensure no processes are unconfined: 2 processes have profiles defined. 2 processes are in enforce mode. 0 processes are in complain mode. 0 processes are unconfined but have a profile defined. Page 148 Internal Only - General Remediation: Run the following command to set all profiles to enforce mode: # aa-enforce /etc/apparmor.d/* Note: Any unconfined processes may need to have a profile created or activated for them and then be restarted References: 1. NIST SP 800-53 Rev. 5: AC-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 149 Internal Only - General 1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: By making sure the kernel.apparmor_restrict_unprivileged_unconfined sysctl setting is enabled, a process that is unprivileged and unconfined cannot leverage aa- exec to change to a more favourable profile Rationale: Unprivileged user namespaces are a feature in the Linux kernel that was introduced in order to provide additional sandboxing functionality for programs such as container runtimes; it enables unprivileged users to gain administrator (root) permissions within a confined environment, without giving them elevated permissions on the host system. However, unconfined profiles that allow the use of user namespaces provide a trivial bypass of the unprivileged user namespace restriction from unconfined processes. All the unconfined application or user has to do is enter the unconfined profile. The unconfined user or application can execute the application associated with the unconfined profile. If the application provides the ability to run arbitrary code or shell access, that is all that needs to be done to bypass the restriction Audit: 1. Run the following script to verify kernel.apparmor_restrict_unprivileged_unconfined is set to 0 in the running configuration: # sysctl kernel.apparmor_restrict_unprivileged_unconfined Verify output is: kernel.apparmor_restrict_unprivileged_unconfined = 1 2. Run the following script to verify kernel.apparmor_restrict_unprivileged_unconfined is set to 1in a sysctl conf file being used by systemd sysctl: Page 150 Internal Only - General #!/usr/bin/env bash { l_parameter_name="kernel.apparmor_restrict_unprivileged_unconfined" l_grep="${l_parameter_name//./\\.}" a_output=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufwscf="$([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_ufwscf" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - UFW set: \"$l_parameter_name\" to: \"$l_option_value\" in: \"$l_file\"") while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - \"$l_parameter_name\" is set to: \"$l_option_value\" in: \"$l_file\"") done < <("$l_systemdsysctl" --cat-config | tac | grep -Psoi '^\h*#\h*\/[^#\n\r\h]+\.conf\b') [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example Output "kernel.apparmor_restrict_unprivileged_unconfined" is set to: "1" in: "/etc/sysctl.d/60-kernel_sysctl.conf" Note: • If the UFW set value is displayed, and is the correct value, this is considered a passing state. If this value is incorrect, it must be updated in the file shown in the audit script output. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl do to system configuration changes. Remediation: 1. Set the kernel.apparmor_restrict_unprivileged_unconfined = kernel parameter to 1 in /etc/sysctl.conf or a file in /etc/sysctl.d/ ending in .conf: Page 151 Internal Only - General Example: # printf "\n%s\n" "kernel.apparmor_restrict_unprivileged_unconfined = 1" >> /etc/sysctl.d/60-kernel_sysctl.conf 2. Run the following command to set the active kernel parameter: # sysctl -w kernel.apparmor_restrict_unprivileged_unconfined=1 3. Run the following command to load all system configuration filles: # sysctl --system Note: If these settings appear in a canonically later file, or later in the same file, these settings will be overwritten References: 1. https://discourse.ubuntu.com/t/understanding-apparmor-user-namespace- restriction/58007 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.5 Enable Anti-Exploitation Features Enable anti-exploitation features on enterprise assets and software, where v8 possible, such as Microsoft® Data Execution Prevention (DEP), Windows® ● ● Defender Exploit Guard (WDEG), or Apple® System Integrity Protection (SIP) and Gatekeeper™. 8.3 Enable Operating System Anti-Exploitation Features/ Deploy Anti-Exploit Technologies v7 Enable anti-exploitation features such as Data Execution Prevention (DEP) or Address Space Layout Randomization (ASLR) that are available in an operating ● ● system or deploy appropriate toolkits that can be configured to apply protection to a broader set of applications and executables. Page 152 Internal Only - General 1.4 Configure Bootloader The recommendations in this section focus on securing the bootloader and settings involved in the boot process directly. Page 153 Internal Only - General 1.4.1 Ensure bootloader password is set (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Setting the boot loader password will require that anyone rebooting the system must enter a password before being able to set command line boot parameters Rationale: Requiring a boot password upon execution of the boot loader will prevent an unauthorized user from entering boot parameters or changing the boot partition. This prevents users from weakening security (e.g. turning off AppArmor at boot time). Impact: If password protection is enabled, only the designated superuser can edit a GRUB 2 menu item by pressing "e" or access the GRUB 2 command line by pressing "c" If GRUB 2 is set up to boot automatically to a password-protected menu entry the user has no option to back out of the password prompt to select another menu entry. Holding the SHIFT key will not display the menu in this case. The user must enter the correct username and password. If unable to do so, the configuration files will have to be edited via a LiveCD or other means to fix the problem You can add --unrestricted to the menu entries to allow the system to boot without entering a password. A password will still be required to edit menu items. More Information: https://help.ubuntu.com/community/Grub2/Passwords Audit: Run the following commands and verify output matches: # grep "^set superusers" /boot/grub/grub.cfg set superusers="" # awk -F. '/^\s*password/ {print $1"."$2"."$3}' /boot/grub/grub.cfg password_pbkdf2 grub.pbkdf2.sha512 Page 154 Internal Only - General Remediation: Create an encrypted password with grub-mkpasswd-pbkdf2: # grub-mkpasswd-pbkdf2 --iteration-count=600000 --salt=64 Enter password: Reenter password: PBKDF2 hash of your password is Add the following into a custom /etc/grub.d configuration file: set superusers="" password_pbkdf2 The superuser/user information and password should not be contained in the /etc/grub.d/00_header file as this file could be overwritten in a package update. If there is a requirement to be able to boot/reboot without entering the password, edit /etc/grub.d/10_linux and add --unrestricted to the line CLASS= Example: CLASS="--class gnu-linux --class gnu --class os --unrestricted" Run the following command to update the grub2 configuration: # update-grub Default Value: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Replace /boot/grub/grub.cfg with the appropriate grub configuration file for your environment. References: 1. NIST SP 800-53 Rev. 5: AC-3 2. NIST SP 800-53A :: AC-3.1 Additional Information: Changes to /etc/grub.d/10_linux may be overwritten during updates to the grub- common package. You should review any changes to this file before rebooting otherwise the system may unexpectedly prompt for a password on the next boot. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists v7 Protect all information stored on systems with file system, network share, claims, application, or database specific access control lists. These controls will ● ● ● enforce the principle that only authorized individuals should have access to the Page 155 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version information based on their need to access the information as a part of their responsibilities. Page 156 Internal Only - General 1.4.2 Ensure access to bootloader config is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The grub configuration file contains information on boot settings and passwords for unlocking boot options. Rationale: Setting the permissions to read and write for root only prevents non-root users from seeing the boot parameters or changing them. Non-root users who read the boot parameters may be able to identify weaknesses in security upon boot and be able to exploit them. Audit: Run the following command and verify Uid and Gid are both 0/root and Access is 0600 or more restrictive. # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /boot/grub/grub.cfg Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set permissions on your grub configuration: # chown root:root /boot/grub/grub.cfg # chmod u-x,go-rwx /boot/grub/grub.cfg Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 157 Internal Only - General Additional Information: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Replace /boot/grub/grub.cfg with the appropriate grub configuration file for your environment CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 158 Internal Only - General 1.5 Configure Additional Process Hardening This section includes Recommendations covering kernel parameters. • sysctl settings are defined through files in /usr/local/lib, /usr/lib/, /lib/, /run/, and /etc/ • Files are typically placed in the sysctl.d directory within the parent directory • The paths where sysctl preload files usually exist o /run/sysctl.d/*.conf o /etc/sysctl.d/*.conf o /usr/local/lib/sysctl.d/*.conf o /usr/lib/sysctl.d/*.conf o /lib/sysctl.d/*.conf o /etc/sysctl.conf • Files must have the ".conf" extension • Vendors settings usually live in /usr/lib/ or /usr/local/lib/ • To override a whole file, create a new file with the same name in /etc/sysctl.d/ and put new settings there. • To override only specific settings, add a file with a lexically later name in /etc/sysctl.d/ and put new settings there. • The command /usr/lib/systemd/systemd-sysctl --cat-config produces output containing The system's loaded kernel parameters and the files they're configured in: o Entries listed latter in the file take precedence over the same settings listed earlier in the file o Files containing kernel parameters that are over-ridden by other files with the same name will not be listed o On systems running UncomplicatedFirewall, the kernel parameters may be set or over-written. This will not be visible in the output of the command • On systems with Uncomplicated Firewall, additional settings may be configured in /etc/ufw/sysctl.conf • The settings in /etc/ufw/sysctl.conf will override settings other settings and will not be visible in the output of the /usr/lib/systemd/systemd-sysctl -- cat-config command • This behavior can be changed by updating the IPT_SYSCTL parameter in /etc/default/ufw • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf Page 159 Internal Only - General o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 160 Internal Only - General 1.5.1 Ensure fs.protected_hardlinks is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: fs.protected_hardlinks Controls the creation of hard links to files. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: Disallowing hardlinks mitigates vulnerabilities based on unsecure file systems accessed by privileged programs. This reduces the risk of an exploitation vector exploiting unsafe use of open or creat. Impact: Users will not be able to create soft or hard links to files they do not own. Audit: Verify fs.protected_hardlinks is set to 1. 1. Run the following command to verify fs.protected_hardlinks is set to 1 in the running configuration: # sysctl fs.protected_hardlinks Verify output is: fs.protected_hardlinks = 1 2. Run the following script to verify fs.protected_hardlinks = 1 is set in a file being used by systemd-sysctl to configure fs.protected_hardlinks: Page 161 Internal Only - General #!/usr/bin/env bash { l_parameter_name="fs.protected_hardlinks" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes fs.protected_hardlinks = 1. Example output: - "fs.protected_hardlinks = 1" is set in: "/etc/sysctl.d/60-fs_sysctl.conf" Verify output includes fs.protected_hardlinks = 1. Note: If multiple lines with fs.protected_hardlinks = are returned: • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 162 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all fs.protected_hardlinks lines that are not fs.protected_hardlinks=1. Example script: #!/usr/bin/env bash { l_option="fs.protected_hardlinks" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: fs.protected_hardlinks = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "fs.protected_hardlinks = 1" >> /etc/sysctl.d/60- fs_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: fs.protected_hardlinks = 0 Page 163 Internal Only - General References: 1. CCI-002165 | CCI-002235 2. NIST SP 800-53 :: AC-3 (4) | NIST SP 800-53 :: AC-6 (10) 3. STIG ID: RHEL-08-010374 | RULE ID: SV-230268r1017086 | CAT II 4. STIG ID: OL08-00-010374 | RULE ID: SV-248578r958702 | CAT II 5. STIG ID: RHEL-09-213030 | RULE ID: SV-257801r958702 | CAT II 6. STIG ID: ALMA-09-007060 | RULE ID: SV-269144r1050026 | CAT II 7. STIG ID: OL09-00-002401 | RULE ID: SV-271740r1091932 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 164 Internal Only - General 1.5.2 Ensure fs.protected_symlinks is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: fs.protected_symlinks Controls how the kernel handles symbolic links. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: Disallowing symlinks mitigates vulnerabilities based on unsecure file systems accessed by privileged programs. This reduces the risk of an exploitation vector exploiting unsafe use of open or creat. Impact: By enabling the fs.protected_symlinks kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the user identifier (UID) of the link and follower match, or when the directory owner matches the symlink's owner. Audit: Verify fs.protected_symlinks is set to 1. 1. Run the following command to verify fs.protected_symlinks is set to 1 in the running configuration: # sysctl fs.protected_symlinks Verify output is: fs.protected_symlinks = 1 2. Run the following script to verify fs.protected_symlinks = 1 is set in a file being used by systemd-sysctl to configure fs.protected_symlinks: Page 165 Internal Only - General #!/usr/bin/env bash { l_parameter_name="fs.protected_symlinks" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes fs.protected_symlinks = 1. Example output: - "fs.protected_symlinks = 1" is set in: "/etc/sysctl.d/60-fs_sysctl.conf" Note: If multiple lines with fs.protected_symlinks = are returned: • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all fs.protected_symlinks lines that are not fs.protected_symlinks=1. Example script: Page 166 Internal Only - General #!/usr/bin/env bash { l_option="fs.protected_symlinks" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: fs.protected_symlinks = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "fs.protected_symlinks = 1" >> /etc/sysctl.d/60- fs_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: fs.protected_symlinks = 0 References: 1. CCI-002165 | CCI-002235 2. NIST SP 800-53 :: AC-3 (4) | NIST SP 800-53 :: AC-6 (10) 3. STIG ID: RHEL-08-010374 | RULE ID: SV-230268r1017086 | CAT II 4. STIG ID: OL08-00-010373 | RULE ID: SV-248577r958702 | CAT II Page 167 Internal Only - General 5. STIG ID: RHEL-09-213030 | RULE ID: SV-257801r958702 | CAT II 6. STIG ID: ALMA-09-007060 | RULE ID: SV-269144r1050026 | CAT II 7. STIG ID: OL09-00-002402 | RULE ID: SV-271741r1091935 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 168 Internal Only - General 1.5.3 Ensure kernel.yama.ptrace_scope is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The ptrace() system call provides a means by which one process (the "tracer") may observe and control the execution of another process (the "tracee"), and examine and change the tracee's memory and registers. The sysctl settings (writable only with CAP_SYS_PTRACE) are: • 0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other process running under the same uid, as long as it is dumpable (i.e. did not transition uids, start privileged, or have called prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is unchanged. • 1 - restricted ptrace: a process must have a predefined relationship with the inferior it wants to call PTRACE_ATTACH on. By default, this relationship is that of only its descendants when the above classic criteria is also met. To change the relationship, an inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare an allowed debugger PID to call PTRACE_ATTACH on the inferior. Using PTRACE_TRACEME is unchanged. • 2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace with PTRACE_ATTACH, or through children calling PTRACE_TRACEME. • 3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via PTRACE_TRACEME. Once set, this sysctl value cannot be changed. Rationale: If one application is compromised, it would be possible for an attacker to attach to other running processes (e.g. Bash, Firefox, SSH sessions, GPG agent, etc) to extract additional credentials and continue to expand the scope of their attack. Enabling restricted mode will limit the ability of a compromised process to PTRACE_ATTACH on other processes running under the same user. With restricted mode, ptrace will continue to work with root user. Page 169 Internal Only - General Audit: Verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3. 1. Run the following command to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in the running configuration: # sysctl kernel.yama.ptrace_scope Example output: kernel.yama.ptrace_scope = 1 2. Run the following script to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in a sysctl conf file being used by systemd-sysctl: #!/usr/bin/env bash { l_parameter_name="kernel.yama.ptrace_scope" l_grep="${l_parameter_name//./\\.}" a_output=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufwscf="$([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_ufwscf" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - UFW set: \"$l_parameter_name\" to: \"$l_option_value\" in: \"$l_file\"") while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(grep -Pois '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - \"$l_parameter_name\" is set to: \"$l_option_value\" in: \"$l_file\"") done < <("$l_systemdsysctl" --cat-config | tac | grep -Pios '^\h*#\h*\/[^#\n\r\h]+\.conf\b') [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "kernel.yama.ptrace_scope" is set to: "1" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Page 170 Internal Only - General Note: • If the UFW set value is displayed, and is the correct value, this is considered a passing state. If this value is incorrect, it must be updated in the file shown in the audit script output. • If multiple lines are returned: o The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd- sysctl do to system configuration changes. Remediation: 1. Review all files ending in .conf in the /etc/sysctl.d directory and comment out or remove all kernel.yama.ptrace_scope lines that are not kernel.yama.ptrace_scope=1, kernel.yama.ptrace_scope=2, or kernel.yama.ptrace_scope=3. Example script: #!/usr/bin/env bash { l_option="kernel.yama.ptrace_scope" l_grep="${l_option//./\\.}" l_value="(1|2|3)" while IFS= read -r -d $'\0' l_file; do grep -Pois '\h*'"$l_option"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*kernel.yama.ptrace_scope\s*=/s/^/# /' "$l_file" done < <(find /etc/sysctl.d/ -type f -name '*.conf' -print0) } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: kernel.yama.ptrace_scope = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.yama.ptrace_scope = 1" >> /etc/sysctl.d/60- kernel_sysctl.conf Page 171 Internal Only - General Note: The example uses kernel.yama.ptrace_scope = 1 but value may be set to 1, 2, or 3 3. Run the following command to load all system configuration files: # sysctl --system Default Value: kernel.yama.ptrace_scope = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040282 | RULE ID: SV-230546r1017308 | CAT II 5. STIG ID: RHEL-09-213080 | RULE ID: SV-257811r1044872 | CAT II 6. STIG ID: ALMA-09-040940 | RULE ID: SV-269424r1050307 | CAT II Additional Information: Ptrace is very rarely used by regular applications and is mostly used by debuggers such as gdb and strace. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 172 Internal Only - General 1.5.4 Ensure fs.suid_dumpable is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: fs.suid_dumpable governs whether a privileged process (with the setuid bit) can generate a core dump, regardless of other configurations. fs.suid_dumpable values: • 0 (default) - Any process that has changed privilege levels (like SUID programs) or is execute-only will not dump core. • 1 (debug) - All processes dump core if possible. The core dump is owned by the current user and security is not applied. This is primarily intended for system debugging. • 2 (suidsafe) - Any binary that normally wouldn't be dumped is dumped, but only if the core_pattern is set to a pipe handler or a fully qualified path. This mode is suitable for administrators debugging in a production environment. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: core dumps may contain sensitive in-memory data like password hashes or keys. An attacker could potentially exploit this to gain access to such data. Impact: Any process that has changed privilege levels (like SUID programs) or is execute-only will not dump core. Audit: Verify fs.suid_dumpable is set to 0. 1. Run the following command to verify fs.suid_dumpable is set to 0 in the running configuration: # sysctl fs.suid_dumpable Verify output is: fs.suid_dumpable = 0 Page 173 Internal Only - General 2. Run the following script to verify fs.suid_dumpable = 0 is set in a file being used by systemd-sysctl to configure fs.suid_dumpable: #!/usr/bin/env bash { l_parameter_name="fs.suid_dumpable" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes fs.suid_dumpable = 0. Example output: - "fs.suid_dumpable = 0" is set in: "/etc/sysctl.d/60-fs_sysctl.conf" Note: If multiple lines with fs.suid_dumpable = are returned: • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all fs.suid_dumpable lines that are not fs.suid_dumpable=0. Page 174 Internal Only - General Example script: #!/usr/bin/env bash { l_option="fs.suid_dumpable" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: fs.suid_dumpable = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "fs.suid_dumpable = 0" >> /etc/sysctl.d/60-fs_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: fs.suid_dumpable = 0 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 175 Internal Only - General Controls Version Control IG 1 IG 2 IG 3 v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 176 Internal Only - General 1.5.5 Ensure kernel.dmesg_restrict is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: kernel.dmesg_restrict can be used to configure the Linux kernel and prevent unprivileged users access to information from the kernel's log buffer. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: Restricting access to the kernel message buffer limits access to only root. This prevents attackers from gaining additional system information as a non-privileged user. Impact: Changing dmesg_restrict to one 1, will restrict access to those users that have the CAP_SYSLOG capability. Audit: Verify kernel.dmesg_restrict is set to 1. 1. Run the following command to verify kernel.dmesg_restrict is set to 1 in the running configuration: # sysctl kernel.dmesg_restrict Verify output is: kernel.dmesg_restrict = 1 2. Run the following script to verify kernel.dmesg_restrict = 1 is set in a file being used by systemd-sysctl to configure kernel.dmesg_restrict: Page 177 Internal Only - General #!/usr/bin/env bash { l_parameter_name="kernel.dmesg_restrict" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes kernel.dmesg_restrict = 1. Example output: - "kernel.dmesg_restrict" is set to: "1" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Note: If multiple lines with kernel.dmesg_restrict = are returned: • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 178 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all kernel.dmesg_restrict lines that are not kernel.dmesg_restrict=1. Example script: #!/usr/bin/env bash { l_option="kernel.dmesg_restrict" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: kernel.dmesg_restrict = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.dmesg_restrict = 1" >> /etc/sysctl.d/60- kernel_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all system configuration files: # sysctl --system Default Value: kernel.dmesg_restrict = 0 Page 179 Internal Only - General References: 1. CCI-001082 | CCI-001090 2. NIST SP 800-53 :: SC-2 | NIST SP 800-53 :: SC-4 3. NIST SP 800-53A :: SC-2.1 | NIST SP 800-53A :: SC-4.1 4. STIG ID: RHEL-08-010375 | RULE ID: SV-230269r1017087 | CAT III 5. STIG ID: OL08-00-010375 | RULE ID: SV-248579r958524 | CAT III 6. STIG ID: RHEL-09-213010 | RULE ID: SV-257797r958514 | CAT II 7. STIG ID: ALMA-09-041050 | RULE ID: SV-269425r1050308 | CAT II 8. STIG ID: OL09-00-002406 | RULE ID: SV-271745r1091947 | CAT II 9. STIG ID: UBTU-22-213010 | RULE ID: SV-260472r958524 | CAT III 10. STIG ID: UBTU-24-600140 | RULE ID: SV-270749r1067179 | CAT III 11. STIG ID: SLES-15-010375 | RULE ID: SV-255921r958524 | CAT III CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 180 Internal Only - General 1.5.6 Ensure prelink is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: prelink is a program that modifies ELF shared libraries and ELF dynamically linked binaries in such a way that the time needed for the dynamic linker to perform relocations at startup significantly decreases. Rationale: The prelinking feature can interfere with the operation of AIDE, because it changes binaries. Prelinking can also increase the vulnerability of the system if a malicious user is able to compromise a common library such as libc. Audit: Verify prelink is not installed: # dpkg-query -s prelink &>/dev/null && echo "prelink is installed" Nothing should be returned. Remediation: Run the following command to restore binaries to normal: # prelink -ua Uninstall prelink using the appropriate package manager or manual installation: # apt purge prelink References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 181 Internal Only - General 1.5.7 Ensure Automatic Error Reporting is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Apport Error Reporting Service automatically generates crash reports for debugging Rationale: Apport collects potentially sensitive data, such as core dumps, stack traces, and log files. They can contain passwords, credit card numbers, serial numbers, and other private material. Audit: Run the following command to verify that the Apport Error Reporting Service is not enabled: # dpkg-query -s apport &> /dev/null && grep -Psi -- '^\h*enabled\h*=\h*[^0]\b' /etc/default/apport Nothing should be returned Run the following command to verify that the apport service is not active: # systemctl is-active apport.service | grep '^active' Nothing should be returned Remediation: Edit /etc/default/apport and add or edit the enabled parameter to equal 0: enabled=0 Run the following commands to stop and mask the apport service # systemctl stop apport.service # systemctl mask apport.service - OR - Run the following command to remove the apport package: # apt purge apport Default Value: enabled=1 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on v8 Enterprise Assets and Software ● ● Page 182 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Uninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 183 Internal Only - General 1.5.8 Ensure kernel.kptr_restrict is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: kernel.kptr_restrict sets whether restrictions are placed on exposing kernel addresses via /proc and other interfaces. • kptr_restrict = 0 - The address is hashed before printing. (equivalent to %p.) • kptr_restrict = 1 - kernel pointers printed using the %pK format specifier will be replaced with 0's. • kptr_restrict = 2 - kernel pointers printed using %pK will be replaced with 0's regardless of privileges. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: Masking the kernel symbols in /proc/kallsyms reduces the ability of an attacker using them to learn more about what to attack on your system. Audit: Verify kernel.kptr_restrict is set to a value of: 1 or 2. 1. Run the following command to verify kernel.kptr_restrict is set to a value of: 1 or 2 in the running configuration: # sysctl kernel.kptr_restrict Example output: kernel.kptr_restrict = 2 2. Run the following script to verify kernel.kptr_restrict is set to a value of: 1 or 2 in a sysctl conf file being used by systemd-sysctl: Page 184 Internal Only - General #!/usr/bin/env bash { l_parameter_name="kernel.kptr_restrict" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes one of the following: • fs.protected_hardlinks = 1 • fs.protected_hardlinks = 2 Example output: - "kernel.kptr_restrict" is set to: "1" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Note: If multiple lines with kernel.kptr_restrict = are returned: • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 185 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all kernel.kptr_restrict lines that are not kernel.kptr_restrict=1 or kernel.kptr_restrict=2. Example script: #!/usr/bin/env bash { l_option="kernel.kptr_restrict" l_value="(1|2)" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pios '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Pios '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[3-9]|[1-9][0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: kernel.kptr_restrict = {N} Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.kptr_restrict = 2" >> /etc/sysctl.d/60- kernel_sysctl.conf Note: The example uses kernel.kptr_restrict = 2 but value may be set to 1 or 2 3. Run the following command to load all system configuration files: # sysctl --system Default Value: kernel.kptr_restrict = 1 Page 186 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040283 | RULE ID: SV-230547r1017309 | CAT II 5. STIG ID: OL08-00-040283 | RULE ID: SV-248891r991589 | CAT II 6. STIG ID: RHEL-09-213025 | RULE ID: SV-257800r1044851 | CAT II 7. STIG ID: ALMA-09-040830 | RULE ID: SV-269423r1050306 | CAT II 8. STIG ID: OL09-00-002408 | RULE ID: SV-271747r1091953 | CAT II 9. STIG ID: SLES-15-010540 | RULE ID: SV-234861r958928 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 187 Internal Only - General 1.5.9 Ensure kernel.randomize_va_space is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Address space layout randomization (ASLR) is an exploit mitigation technique which randomly arranges the address space of key data areas of a process. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: Randomly placing virtual memory regions will make it difficult to write memory page exploits as the memory placement will be consistently shifting. Audit: Verify kernel.randomize_va_space is set to 2. 1. Run the following command to verify kernel.randomize_va_space is set to 2 in the running configuration: # sysctl kernel.randomize_va_space Verify output is: kernel.randomize_va_space = 2 2. Run the following script to verify kernel.randomize_va_space = 2 is set in a file being used by systemd sysctl to configure kernel.randomize_va_space: Page 188 Internal Only - General #!/usr/bin/env bash { l_parameter_name="kernel.randomize_va_space" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes kernel.randomize_va_space = 2. Example output: - "kernel.randomize_va_space" is set to: "2" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Note: If multiple lines with kernel.randomize_va_space = are returned: • The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 189 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all kernel.randomize_va_space lines that are not kernel.randomize_va_space=2. Example script: #!/usr/bin/env bash { l_option="kernel.randomize_va_space" l_value="2" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*([01]|[3-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: kernel.randomize_va_space = 2 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.randomize_va_space = 2" >> /etc/sysctl.d/60- kernel_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all system configuration filles: # sysctl --system Default Value: kernel.randomize_va_space = 2 Page 190 Internal Only - General References: 1. CCI-002824 2. NIST SP 800-53 :: SI-16 3. STIG ID: RHEL-08-010430 | RULE ID: SV-230280r1017093 | CAT II 4. STIG ID: OL08-00-010430 | RULE ID: SV-248594r958928 | CAT II 5. STIG ID: RHEL-09-213070 | RULE ID: SV-257809r1044866 | CAT II 6. STIG ID: ALMA-09-044900 | RULE ID: SV-269452r1050335 | CAT II 7. STIG ID: OL09-00-002423 | RULE ID: SV-271761r1091995 | CAT II 8. STIG ID: UBTU-22-213020 | RULE ID: SV-260474r958928 | CAT II 9. STIG ID: UBTU-24-700310 | RULE ID: SV-270772r1066805 | CAT II 10. STIG ID: SLES-15-010550 | RULE ID: SV-234862r958928 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.5 Enable Anti-Exploitation Features Enable anti-exploitation features on enterprise assets and software, where v8 possible, such as Microsoft® Data Execution Prevention (DEP), Windows® ● ● Defender Exploit Guard (WDEG), or Apple® System Integrity Protection (SIP) and Gatekeeper™. 8.3 Enable Operating System Anti-Exploitation Features/ Deploy Anti-Exploit Technologies v7 Enable anti-exploitation features such as Data Execution Prevention (DEP) or Address Space Layout Randomization (ASLR) that are available in an operating ● ● system or deploy appropriate toolkits that can be configured to apply protection to a broader set of applications and executables. Page 191 Internal Only - General 1.5.10 Ensure kernel.yama.ptrace_scope is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The ptrace() system call provides a means by which one process (the "tracer") may observe and control the execution of another process (the "tracee"), and examine and change the tracee's memory and registers. The sysctl settings (writable only with CAP_SYS_PTRACE) are: • 0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other process running under the same uid, as long as it is dumpable (i.e. did not transition uids, start privileged, or have called prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is unchanged. • 1 - restricted ptrace: a process must have a predefined relationship with the inferior it wants to call PTRACE_ATTACH on. By default, this relationship is that of only its descendants when the above classic criteria is also met. To change the relationship, an inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare an allowed debugger PID to call PTRACE_ATTACH on the inferior. Using PTRACE_TRACEME is unchanged. • 2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace with PTRACE_ATTACH, or through children calling PTRACE_TRACEME. • 3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via PTRACE_TRACEME. Once set, this sysctl value cannot be changed. More information about the kernel parameter configuration files, their location, and load preference is available in the section overview. Rationale: If one application is compromised, it would be possible for an attacker to attach to other running processes (e.g. Bash, Firefox, SSH sessions, GPG agent, etc) to extract additional credentials and continue to expand the scope of their attack. Enabling restricted mode will limit the ability of a compromised process to PTRACE_ATTACH on other processes running under the same user. With restricted mode, ptrace will continue to work with root user. Page 192 Internal Only - General Impact: Based on value chosen. • 1 A process must have a predefined relationship with the inferior it wants to call PTRACE_ATTACH on. By default, this relationship is that of only its descendants when the above classic criteria is also met. To change the relationship, an inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare an allowed debugger PID to call PTRACE_ATTACH on the inferior. Using PTRACE_TRACEME is unchanged. • 2 Only processes with CAP_SYS_PTRACE may use ptrace with PTRACE_ATTACH, or through children calling PTRACE_TRACEME. • 3 No processes may use ptrace with PTRACE_ATTACH nor via PTRACE_TRACEME. Once set, this sysctl value cannot be changed. Audit: Verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3. 1. Run the following command to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in the running configuration: # sysctl kernel.yama.ptrace_scope Example output: kernel.yama.ptrace_scope = 1 2. Run the following script to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in a sysctl conf file being used by systemd sysctl: Page 193 Internal Only - General #!/usr/bin/env bash { l_parameter_name="kernel.yama.ptrace_scope" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes one of: • kernel.yama.ptrace_scope = 1 • kernel.yama.ptrace_scope = 2 • kernel.yama.ptrace_scope = 3 Example output: - "kernel.yama.ptrace_scope" is set to: "1" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Note: If multiple lines with kernel.yama.ptrace_scope = are returned: • The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 194 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all kernel.yama.ptrace_scope lines that are not kernel.yama.ptrace_scope=1, kernel.yama.ptrace_scope=2, or kernel.yama.ptrace_scope=3. Example script: #!/usr/bin/env bash { l_option="kernel.yama.ptrace_scope" l_value="(1|2|3)" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|4-9|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .conf and edit or add the following line: kernel.yama.ptrace_scope = {N} Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.yama.ptrace_scope = 1" >> /etc/sysctl.d/60- kernel_sysctl.conf Note: The example uses kernel.yama.ptrace_scope = 1 but value may be set to 1, 2, or 3 3. Run the following command to load all system configuration filles: # sysctl --system Default Value: kernel.yama.ptrace_scope = 0 Page 195 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040282 | RULE ID: SV-230546r1017308 | CAT II 5. STIG ID: OL08-00-040282 | RULE ID: SV-248890r991589 | CAT II 6. STIG ID: RHEL-09-213080 | RULE ID: SV-257811r1044872 | CAT II 7. STIG ID: ALMA-09-040940 | RULE ID: SV-269424r1050307 | CAT II 8. STIG ID: OL09-00-002410 | RULE ID: SV-271749r1091959 | CAT II Additional Information: Ptrace is very rarely used by regular applications and is mostly used by debuggers such as gdb and strace. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 196 Internal Only - General 1.5.11 Ensure core file size is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: core - limits the core file size hard - for enforcing hard resource limits. These limits are set by the superuser and enforced by the Kernel. The user cannot raise their requirement of system resources above such values. Rationale: Setting a hard limit on core dumps prevents users from overriding the soft variable. A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems. Audit: Run the following command to verify a hard limit for core is set to 0 for all users *: # grep -Psi -- '^\h*\*\h+hard\h+core\b' /etc/security/limits.conf /etc/security/limits.d/* Example output: /etc/security/limits.d/60-limits.conf:* hard core 0 Verify no line are returned with a value greater than 0. Note: By default limits are taken from the /etc/security/limits.conf config file. Then individual *.conf files from the /etc/security/limits.d/ directory are read. The files are parsed one after another in the order of "C" locale. The effect of the individual files is the same as if all the files were concatenated together in the order of parsing. If a config file is explicitly specified with a module option then the files in the above directory are not parsed. Page 197 Internal Only - General Remediation: 1. Run the following command to comment out any entries that include a hard value for core greater than 0 in /etc/security/limits.conf and any file(s) in the /etc/security/limits.d/ directory. Example: # sed -ri '/^\s*[^#\n\r]+\s+hard\s+core\s+([1-9][0-9]*)/s/^/# /' /etc/security/limits.conf /etc/security/limits.d/* 2. Create or edit a file in /etc/security/limits.d/ and add the following line: * hard core 0 Example: # printf '%s\n' "" "* hard core 0" >> /etc/security/limits.d/60-limits.conf Default Value: None References: 1. limits.conf(5) 2. CCI-000366 3. NIST SP 800-53 :: CM-6 b 4. NIST SP 800-53A :: CM-6.1 (iv) 5. STIG ID: RHEL-08-010673 | RULE ID: SV-230313r1069304 | CAT II 6. STIG ID: RHEL-09-213095 | RULE ID: SV-257814r991589 | CAT II 7. STIG ID: ALMA-09-044900 | RULE ID: SV-269452r1050335 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 198 Internal Only - General 1.5.12 Ensure systemd-coredump ProcessSizeMax is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A core dump is the memory of an executable program. It is generally used to determine why a program aborted. It can also be used to glean confidential information from a core file. Rationale: A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems, increasing the risk to the system. Impact: Setting ProcessSizeMax=0 effectively disables processing of core dumps by systemd- coredump. Audit: Run the following script to verify systemd-coredump ProcessSizeMax is set to 0: Page 199 Internal Only - General #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/coredump.conf" l_block="Coredump" l_option="ProcessSizeMax" l_option_value="" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "ProcessSizeMax" is set to: "0" in: "/etc/systemd/coredump.conf.d/60- coredump.conf" Note: • - IF - the systemd-coredump package is not installed this is considered a passing state and remediation is not necessary. • If multiple lines are returned: • The first line includes the value being used by systemd-coredump. If this is a correct value, this is considered a passing state. • Files that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd-coredump due to system configuration changes • If the default value is displayed, and is the correct value, this is considered a passing state. However, it is recommended to follow the Remediation procedure to mitigate the potential of a system update changing the default value to an incorrect value. Page 200 Internal Only - General Remediation: 1. Review all files ending in .conf in the /etc/systemd/coredump.conf.d/ directory and comment out or remove all ProcessSizeMax= lines in the [Coredump] block that are not ProcessSizeMax=0. Example script: #!/usr/bin/env bash { l_block="Coredump" l_option="ProcessSizeMax" l_value="0" while IFS= read -r -d $'\0' l_file; do awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" 2>/dev/null | \ grep -Poi '\h*'"$l_option"'\h*=\h*\H+\b' | \ grep -Pivq '^\h*'"$l_option"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*[Pp]rocess[Ss]ize[Mm]ax\s*=/s/^/# /' "$l_file" done < <(find /etc/systemd/coredump.conf.d/ -type f -name '*.conf' - print0) } 2. Create or edit a file in the /etc/systemd/coredump.conf.d directory ending in .conf and edit or add the following line to the [Coredump] section: ProcessSizeMax=0 Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/coredump.conf.d/ ] && mkdir -p /etc/systemd/coredump.conf.d/ l_file="/etc/systemd/coredump.conf.d/60-coredump.conf" if grep -Psq -- '^\h*\[Coredump\]' "$l_file"; then sed -ri '/^\s*\[Coredump\]/a ProcessSizeMax=0' "$l_file" else printf '%s\n' "" "[Coredump]" "ProcessSizeMax=0" >> "$l_file" fi } 3. Run the following command to load the updated configuration: # systemctl reload-or-restart systemd-coredump.socket Page 201 Internal Only - General Default Value: ProcessSizeMax=2G References: 1. COREDUMP.CONF(5) 2. CCI-000366 3. NIST SP 800-53 :: CM-6 b 4. NIST SP 800-53A :: CM-6.1 (iv) 5. STIG ID: RHEL-08-010675 | RULE ID: SV-230315r1017126 | CAT II 6. STIG ID: OL08-00-010675 | RULE ID: SV-248633r991589 | CAT II 7. STIG ID: RHEL-09-213085 | RULE ID: SV-257812r1051005 | CAT II 8. STIG ID: ALMA-09-011570 | RULE ID: SV-269181r1050063 | CAT II 9. STIG ID: OL09-00-002381 | RULE ID: SV-271729r1091899 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 202 Internal Only - General 1.5.13 Ensure systemd-coredump Storage is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A core dump is the memory of an executable program. It is generally used to determine why a program aborted. It can also be used to glean confidential information from a core file. Rationale: A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems. Impact: The core dumps may be logged, but not stored permanently. Audit: Run the following script to verify systemd-coredump Storage is set to none: Page 203 Internal Only - General #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/coredump.conf" l_block="Coredump" l_option="Storage" l_option_value="" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "Storage" is set to: "none" in: "/etc/systemd/coredump.conf.d/60- coredump.conf" Note: • - IF - the systemd-coredump package is not installed this is considered a passing state and remediation is not necessary. • If multiple lines are returned: • The first line includes the value being used by systemd-coredump. If this is a correct value, this is considered a passing state. • Files that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd-coredump due to system configuration changes • If the default value is displayed, and is the correct value, this is considered a passing state. However, it is recommended to follow the Remediation procedure to mitigate the potential of a system update changing the default value to an incorrect value. Page 204 Internal Only - General Remediation: 1. Review all files ending in .conf in the /etc/systemd/coredump.conf.d/ directory and comment out or remove all Storage= lines in the [Coredump] block that are not Storage=none. Example script: #!/usr/bin/env bash { l_block="Coredump" l_option="Storage" l_value="none" while IFS= read -r -d $'\0' l_file; do awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" 2>/dev/null | \ grep -Poi '\h*'"$l_option"'\h*=\h*\H+\b' | \ grep -Pivq '^\h*'"$l_option"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*[Ss]torage\s*=/s/^/# /' "$l_file" done < <(find /etc/systemd/coredump.conf.d/ -type f -name '*.conf' - print0) } 2. Create or edit a file in the /etc/systemd/coredump.conf.d directory ending in .conf and edit or add the following line to the [Coredump] section: Storage=none Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/coredump.conf.d/ ] && mkdir -p \ /etc/systemd/coredump.conf.d/ l_file="/etc/systemd/coredump.conf.d/60-coredump.conf" if grep -Psq -- '^\h*\[Coredump\]' "$l_file"; then sed -ri '/^\s*\[Coredump\]/a Storage=none' "$l_file" else printf '%s\n' "" "[Coredump]" "Storage=none" >> "$l_file" fi } 3. Run the following command to load the updated configuration: # systemctl reload-or-restart systemd-coredump.socket Page 205 Internal Only - General Default Value: Storage=external References: 1. COREDUMP.CONF(5) 2. CCI-000366 3. NIST SP 800-53 :: CM-6 b 4. NIST SP 800-53A :: CM-6.1 (iv) 5. STIG ID: RHEL-08-010674 | RULE ID: SV-230314r1017125 | CAT II 6. STIG ID: OL08-00-010674 | RULE ID: SV-248632r991589 | CAT II 7. STIG ID: RHEL-09-213090 | RULE ID: SV-257813r991589 | CAT II 8. STIG ID: ALMA-09-011460 | RULE ID: SV-269180r1050062 | CAT II 9. STIG ID: OL09-00-002382 | RULE ID: SV-271730r1091902 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 206 Internal Only - General 1.6 Configure Command Line Warning Banners Presenting a warning message prior to the normal user login may assist in the prosecution of trespassers on the computer system. Changing some of these login banners also has the side effect of hiding OS version information and other detailed system information from attackers attempting to target specific exploits at a system. Guidelines published by the US Department of Defense require that warning messages include at least the name of the organization that owns the system, the fact that the system is subject to monitoring and that such monitoring is in compliance with local statutes, and that use of the system implies consent to such monitoring. It is important that the organization's legal counsel review the content of all messages before any system modifications are made, as these warning messages are inherently site-specific. More information (including citations of relevant case law) can be found at http://www.justice.gov/criminal/cybercrime/ The /etc/motd, /etc/issue, and /etc/issue.net files govern warning banners for standard command line logins for both local and remote users. Note: The text provided in the remediation actions for these items is intended as an example only. Please edit to include the specific text for your organization as approved by your legal department. Page 207 Internal Only - General 1.6.1 Ensure /etc/motd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Page 208 Internal Only - General Audit: Run the following script to verify MOTD files do not contain system information: #!/usr/bin/env bash { l_output="" l_output2="" a_files=() for l_file in /etc/motd{,.d/*}; do if grep -Psqi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep ^ID= /etc/os-release | cut -d= -f2 | sed -e 's/"//g')\b)" "$l_file"; then l_output2="$l_output2\n - File: \"$l_file\" includes system information" else a_files+=("$l_file") fi done if [ "${#a_files[@]}" -gt 0 ]; then echo -e "\n- ** Please review the following files and verify their contents follow local site policy **\n" printf '%s\n' "${a_files[@]}" elif [ -z "$l_output2" ]; then echo -e "- ** No MOTD files with any size were found. Please verify this conforms to local site policy ** -" fi if [ -z "$l_output2" ]; then l_output=" - No MOTD files include system information" echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n" fi } Review any files returned and verify that they follow local site policy Page 209 Internal Only - General Remediation: Edit the file found in /etc/motd.d/* with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform - OR - - IF - the motd is not used, this file can be removed. Run the following command to remove the motd file: # rm /etc/motd Run the following script and review and/or update all returned files' contents to: • Remove all system information (\v, \r; \m, \s) • Remove any refence to the operating system • Ensure contents follow local site policy #!/usr/bin/env bash { a_files=() for l_file in /etc/motd{,.d/*}; do if grep -Psqi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep ^ID= /etc/os-release | cut -d= -f2 | sed -e 's/"//g')\b)" "$l_file"; then echo -e "\n - File: \"$l_file\" includes system information. Edit this file to remove these entries" else a_files+=("$l_file") fi done if [ "${#a_files[@]}" -gt 0 ]; then echo -e "\n- ** Please review the following files and verify their contents follow local site policy **\n" printf '%s\n' "${a_files[@]}" fi } References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 Page 210 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 211 Internal Only - General 1.6.2 Ensure /etc/issue is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue file are displayed to users prior to login for local terminals. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version - or the operating system's name Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Audit: Run the following command and verify that the contents match site policy: # cat /etc/issue Run the following command and verify no results are returned: # grep -Psi "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut -d= - f2 | sed -e 's/"//g')\b)" /etc/issue Remediation: Edit the /etc/issue file with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # echo "Authorized users only. All activity may be monitored and reported." > /etc/issue References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 Page 212 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 213 Internal Only - General 1.6.3 Ensure /etc/issue.net is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue.net file are displayed to users prior to login for remote connections from configured services. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Audit: Run the following command and verify that the contents match site policy: # cat /etc/issue.net Run the following command and verify no results are returned: # grep -Psi "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut -d= - f2 | sed -e 's/"//g')\b)" /etc/issue.net Remediation: Edit the /etc/issue.net file with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # echo "Authorized users only. All activity may be monitored and reported." > /etc/issue.net References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 Page 214 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 215 Internal Only - General 1.6.4 Ensure access to /etc/motd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Rationale: - IF - the /etc/motd file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify that if /etc/motd exists, Access is 644 or more restrictive, Uid and Gid are both 0/root: # [ -e /etc/motd ] && stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/motd Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) -- OR -- Nothing is returned Remediation: Run the following commands to set mode, owner, and group on /etc/motd: # chown root:root $(readlink -e /etc/motd) # chmod u-x,go-wx $(readlink -e /etc/motd) - OR - Run the following command to remove the /etc/motd file: # rm /etc/motd References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. v7 14.6 Protect Information through Access Control Lists ● ● ● Protect all information stored on systems with file system, network share, Page 216 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities. Page 217 Internal Only - General 1.6.5 Ensure access to /etc/issue is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue file are displayed to users prior to login for local terminals. Rationale: - IF - the /etc/issue file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify Access is 644 or more restrictive and Uid and Gid are both 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/issue Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) Remediation: Run the following commands to set mode, owner, and group on /etc/issue: # chown root:root $(readlink -e /etc/issue) # chmod u-x,go-wx $(readlink -e /etc/issue) Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 218 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 219 Internal Only - General 1.6.6 Ensure access to /etc/issue.net is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue.net file are displayed to users prior to login for remote connections from configured services. Rationale: - IF - the /etc/issue.net file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify Access is 644 or more restrictive and Uid and Gid are both 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/issue.net Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set mode, owner, and group on /etc/issue.net: # chown root:root $(readlink -e /etc/issue.net) # chmod u-x,go-wx $(readlink -e /etc/issue.net) Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 220 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 221 Internal Only - General 1.7 Configure GNOME Display Manager The GNOME Display Manager (GDM) is a program that manages graphical display servers and handles graphical user logins. This subsection requires user profiles to already exist on the system. A profile is a list of configuration databases. Sample profile: user-db:user system-db:local system-db:site Configuring a single user and multiple system databases allows for layering of preferences. Settings from the user database file take precedence over the settings in the local database file, and the local database file in turn takes precedence over the site database file. Note: • - IF - GDM is not installed on the system, this section can be skipped • The Remediation Procedure commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. Page 222 Internal Only - General 1.7.1 Ensure GDM is removed (Automated) Profile Applicability: • Level 2 - Server Description: The GNOME Display Manager (GDM) is a program that manages graphical display servers and handles graphical user logins. Rationale: If a Graphical User Interface (GUI) is not required, it should be removed to reduce the attack surface of the system. Impact: Removing the GNOME Display manager will remove the Graphical User Interface (GUI) from the system. Audit: Run the following command and verify gdm3 is not installed: # dpkg-query -s gdm3 &>/dev/null && echo "gdm3 is installed" Nothing should be returned Remediation: Run the following commands to uninstall gdm3 and remove unused dependencies: # apt purge gdm3 # apt autoremove gdm3 References: 1. NIST SP 800-53 Rev. 5: CM-11 Page 223 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 224 Internal Only - General 1.7.2 Ensure GDM login banner is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GDM is the GNOME Display Manager which handles graphical login for GNOME based systems. Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Audit: Run the following commands to verify that the text banner on the login screen is enabled and set: # gsettings get org.gnome.login-screen banner-message-enable true # gsettings get org.gnome.login-screen banner-message-text 'Authorized uses only. All activity may be monitored and reported' Page 225 Internal Only - General Remediation: - IF - A user profile is already created run the following commands to set and enable the text banner message on the login screen: # gsettings set org.gnome.login-screen banner-message-text 'Authorized uses only. All activity may be monitored and reported' # gsettings set org.gnome.login-screen banner-message-enable true Note: • banner-message-text may be set in accordance with local site policy • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. • If the dconf database is not updating correctly due to umask requirements contain in the benchmark, then use (umask 0022 && gsetting set) commands from above to temporarily set umask ensuring that any files or directories created by gsettings will have the required permissions. - OR/IF - A user profile does not exist: 1. Create or edit the gdm profile in the /etc/dconf/profile/gdm with the following lines: user-db:user system-db:gdm file-db:/usr/share/gdm/greeter-dconf-defaults Note: gdm is the name of a dconf database. 2. Create a gdm keyfile for machine-wide settings in /etc/dconf/db/gdm.d/01- banner-message: [org/gnome/login-screen] banner-message-enable=true banner-message-text='Type the banner message here.' 3. Update the system databases # dconf update Note: • Users must log out and back in again before the system-wide settings take effect. • There is no character limit for the banner message. gnome-shell autodetects longer stretches of text and enters two column mode. • The banner message cannot be read from an external file Page 226 Internal Only - General Default Value: disabled References: 1. https://help.gnome.org/admin/system-admin-guide/stable/login-banner.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Additional Information: Additional options and sections may appear in the /etc/dconf/db/gdm.d/01-banner- message file. If a different GUI login service is in use, consult your documentation and apply an equivalent banner. Page 227 Internal Only - General 1.7.3 Ensure GDM disable-user-list option is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GDM is the GNOME Display Manager which handles graphical login for GNOME based systems. The disable-user-list option controls if a list of users is displayed on the login screen Rationale: Displaying the user list eliminates half of the Userid/Password equation that an unauthorized person would need to log on. Audit: Run the following command and to verify that the disable-user-list option is enabled: # gsettings get org.gnome.login-screen disable-user-list true Page 228 Internal Only - General Remediation: - IF - A user profile exists run the following command to enable the disable-user- list: # gsettings set org.gnome.login-screen disable-user-list true Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. • If the dconf database is not updating correctly due to umask requirements contain in the benchmark, then use (umask 0022 && gsetting set) commands from above to temporarily set umask ensuring that any files or directories created by gsettings will have the required permissions. - OR/IF - A user profile does not exist: 1. Create or edit the gdm profile in /etc/dconf/profile/gdm with the following lines: user-db:user system-db:gdm file-db:/usr/share/gdm/greeter-dconf-defaults Note: gdm is the name of a dconf database. 2. Create a gdm keyfile for machine-wide settings in /etc/dconf/db/gdm.d/00- login-screen: [org/gnome/login-screen] # Do not show the user list disable-user-list=true 3. Update the system databases: # dconf update Note: When the user profile is created or changed, the user will need to log out and log in again before the changes will be applied. Default Value: false References: 1. https://help.gnome.org/admin/system-admin-guide/stable/login-userlist- disable.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 229 Internal Only - General Additional Information: If a different GUI login service is in use and required on the system, consult your documentation to disable displaying the user list Page 230 Internal Only - General 1.7.4 Ensure GDM screen locks when the user is idle (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GNOME Desktop Manager can make the screen lock automatically whenever the user is idle for some amount of time. Rationale: Setting a lock-out value reduces the window of opportunity for unauthorized user access to another user's session that has been left unattended. Audit: Run the following commands to verify that the screen locks when the user is idle: # gsettings get org.gnome.desktop.screensaver lock-delay uint32 5 # gsettings get org.gnome.desktop.session idle-delay uint32 900 Notes: • lock-delay=uint32 {n} - should be 5 seconds or less and follow local site policy • idle-delay=uint32 {n} - Should be 900 seconds (15 minutes) or less, not 0 (disabled) and follow local site policy Page 231 Internal Only - General Remediation: - IF - A user profile is already created run the following commands to enable screen locks when the user is idle: # gsettings set org.gnome.desktop.screensaver lock-delay 5 # gsettings set org.gnome.desktop.session idle-delay 900 Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. • If the dconf database is not updating correctly due to umask requirements contain in the benchmark, then use (umask 0022 && gsetting set) commands from above to temporarily set umask ensuring that any files or directories created by gsettings will have the required permissions. - OR/IF- A user profile does not exist: 1. Create or edit the user profile in the /etc/dconf/profile/ and verify it includes the following: user-db:user system-db:{NAME_OF_DCONF_DATABASE} Note: local is the name of a dconf database used in the examples. 2. Create the directory /etc/dconf/db/local.d/ if it doesn't already exist: 3. Create the key file /etc/dconf/db/local.d/00-screensaver to provide information for the local database: Example key file: # Specify the dconf path [org/gnome/desktop/session] # Number of seconds of inactivity before the screen goes blank # Set to 0 seconds if you want to deactivate the screensaver. idle-delay=uint32 180 # Specify the dconf path [org/gnome/desktop/screensaver] # Number of seconds after the screen is blank before locking the screen lock-delay=uint32 0 Note: You must include the uint32 along with the integer key values as shown. 4. Run the following command to update the system databases: # dconf update 5. Users must log out and back in again before the system-wide settings take effect. Page 232 Internal Only - General References: 1. https://help.gnome.org/admin/system-admin-guide/stable/desktop- lockscreen.html.en 2. NIST SP 800-53 Revision 5 :: AC-11 a 3. NIST SP 800-53A :: AC-11.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 233 Internal Only - General 1.7.5 Ensure GDM screen locks cannot be overridden (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GNOME Desktop Manager can lock down specific settings by using the lockdown mode in dconf to prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory at /etc/dconf/db/local.d/locks/. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: Setting a lock-out value reduces the window of opportunity for unauthorized user access to another user's session that has been left unattended. Without locking down the system settings, user settings take precedence over the system settings. Page 234 Internal Only - General Audit: Run the following script to verify that the screen lock cannot be overridden: #!/usr/bin/env bash { a_output=() a_output2=() f_check_setting() { grep -Psrilq -- "^\h*$2\b" /etc/dconf/db/local.d/locks/* && \ echo "- \"$3\" is locked" || echo "- \"$3\" is not locked or not set" } declare -A settings=( ["idle-delay"]="/org/gnome/desktop/session/idle-delay" ["lock-delay"]="/org/gnome/desktop/screensaver/lock-delay" ) for setting in "${!settings[@]}"; do result=$(f_check_setting "$setting" "${settings[$setting]}" "$setting") if [[ $result == *"is not locked"* || $result == *"not set to false"* ]]; then a_output2+=("$result") else a_output+=("$result") fi done printf '%s\n' "" "- Audit Result:" if [ "${#a_output2[@]}" -gt 0 ]; then printf '%s\n' " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" else printf '%s\n' " ** PASS **" "${a_output[@]}" fi } Page 235 Internal Only - General Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-screensaver with the following content: # Lock desktop screensaver settings /org/gnome/desktop/session/idle-delay /org/gnome/desktop/screensaver/lock-delay 2. Update the system databases: # dconf update Note: • A user profile must exist in order to apply locks. • Users must log out and back in again before the system-wide settings take effect. References: 1. https://help.gnome.org/admin/system-admin-guide/stable/desktop- lockscreen.html.en 2. https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en 3. NIST SP 800-53 Rev. 5: CM-11 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 236 Internal Only - General 1.7.6 Ensure GDM automatic mounting of removable media is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: By default GNOME automatically mounts removable media when inserted as a convenience to the user. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users. If your organization allows the use of portable storage or media on workstations and physical access controls to workstations is considered adequate there is little value add in turning off automounting. Audit: Run the following commands to verify automatic mounting is disabled: # gsettings get org.gnome.desktop.media-handling automount false # gsettings get org.gnome.desktop.media-handling automount-open false Page 237 Internal Only - General Remediation: - IF - A user profile exists run the following commands to ensure automatic mounting is disabled: # gsettings set org.gnome.desktop.media-handling automount false # gsettings set org.gnome.desktop.media-handling automount-open false Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. • If the dconf database is not updating correctly due to umask requirements contain in the benchmark, then use (umask 0022 && gsetting set) commands from above to temporarily set umask ensuring that any files or directories created by gsettings will have the required permissions. - OR/IF - A user profile does not exist: 1. Create a file /etc/dconf/db/local.d/00-media-automount with following content: [org/gnome/desktop/media-handling] automount=false automount-open=false 2. After creating the file, apply the changes using below command : # dconf update Note: Users must log out and back in again before the system-wide settings take effect. References: 1. https://access.redhat.com/solutions/20107 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 238 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 239 Internal Only - General 1.7.7 Ensure GDM disabling automatic mounting of removable media is not overridden (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: By default GNOME automatically mounts removable media when inserted as a convenience to the user. By using the lockdown mode in dconf, you can prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users Page 240 Internal Only - General Audit: Run the following script to verify automatic mounting of removable media is not overridden and correctly configured in a configuration file: • automount=false • automount-open=false #!/usr/bin/env bash { a_output=() a_output2=() check_setting() { grep -Psrilq "^\h*$1\h*=\h*false\b" /etc/dconf/db/local.d/locks/* 2> /dev/null && \ echo "- \"$3\" is locked and set to false" || echo "- \"$3\" is not locked or not set to false" } declare -A settings=( ["automount"]="org/gnome/desktop/media-handling" ["automount-open"]="org/gnome/desktop/media-handling" ) for setting in "${!settings[@]}"; do result=$(check_setting "$setting" "${settings[$setting]}" "$setting") if [[ $result == *"is not locked"* || $result == *"not set to false"* ]]; then a_output2+=("$result") else a_output+=("$result") fi done printf '%s\n' "" "- Audit Result:" if [ "${#a_output2[@]}" -gt 0 ]; then printf '%s\n' " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" else printf '%s\n' " ** PASS **" "${a_output[@]}" fi } Page 241 Internal Only - General Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-media-automount with the following content: [org/gnome/desktop/media-handling] automount=false automount-open=false 2. Update the systems databases: # dconf update Note: • A user profile must exist in order to apply locks. • Users must log out and back in again before the system-wide settings take effect. References: 1. https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 3. https://manpages.ubuntu.com/manpages/trusty/man1/gsettings.1.html 4. https://access.redhat.com/solutions/20107 Page 242 Internal Only - General 1.7.8 Ensure GDM autorun-never is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The autorun-never setting allows the GNOME Desktop Display Manager to disable autorun through GDM. Rationale: Malware on removable media may taking advantage of Autorun features when the media is inserted into a system and execute. Audit: Run the following command to verify that autorun-never is set to true for GDM: # gsettings get org.gnome.desktop.media-handling autorun-never true Page 243 Internal Only - General Remediation: - IF - A user profile exists run the following command to set autorun-never to true for GDM users: # gsettings set org.gnome.desktop.media-handling autorun-never true Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. • If the dconf database is not updating correctly due to umask requirements contain in the benchmark, then use (umask 0022 && gsetting set) commands from above to temporarily set umask ensuring that any files or directories created by gsettings will have the required permissions. - OR/IF - A lock does not exist: 1. create the file /etc/dconf/db/local.d/locks/00-media-autorun with the following content: [org/gnome/desktop/media-handling] autorun-never=true 2. Update the systems databases: # dconf update Note: Users must log out and back in again before the system-wide settings take effect. Default Value: false References: 1. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 244 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 245 Internal Only - General 1.7.9 Ensure GDM autorun-never is not overridden (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The autorun-never setting allows the GNOME Desktop Display Manager to disable autorun through GDM. By using the lockdown mode in dconf, you can prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: Malware on removable media may taking advantage of Autorun features when the media is inserted into a system and execute. Page 246 Internal Only - General Audit: Run the following script to verify that autorun-never=true cannot be overridden: #!/usr/bin/env bash { # Function to check and report if a specific setting is locked and set to true check_setting() { grep -Psrilq "^\h*$1\h*=\h*true\b" /etc/dconf/db/local.d/locks/* 2> /dev/null && echo "- \"$3\" is locked and set to false" || echo "- \"$3\" is not locked or not set to false" } # Array of settings to check declare -A settings=(["autorun-never"]="org/gnome/desktop/media- handling") # Check GNOME Desktop Manager configurations l_output=() l_output2=() for setting in "${!settings[@]}"; do result=$(check_setting "$setting") l_output+=("$result") if [[ $result == *"is not locked"* || $result == *"not set to true"* ]]; then l_output2+=("$result") fi done # Report results if [ ${#l_output2[@]} -ne 0 ]; then printf '%s\n' "- Audit Result:" " ** FAIL **" printf '%s\n' "- Reason(s) for audit failure:" for msg in "${l_output2[@]}"; do printf '%s\n' "$msg" done else printf '%s\n' "- Audit Result:" " ** PASS **" fi } Page 247 Internal Only - General Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-media-autorun with the following content: [org/gnome/desktop/media-handling] autorun-never=true 2. Update the systems databases: # dconf update Note: • A user profile must exist in order to apply locks. • Users must log out and back in again before the system-wide settings take effect. References: 1. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 248 Internal Only - General 1.7.10 Ensure XDMCP is not enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: X Display Manager Control Protocol (XDMCP) is designed to provide authenticated access to display management services for remote displays Rationale: XDMCP is inherently insecure. • XDMCP is not a ciphered protocol. This may allow an attacker to capture keystrokes entered by a user • XDMCP is vulnerable to man-in-the-middle attacks. This may allow an attacker to steal the credentials of legitimate users by impersonating the XDMCP server. Audit: Run the following script and verify the output: #!/usr/bin/env bash { while IFS= read -r l_file; do awk '/\[xdmcp\]/{ f = 1;next } /\[/{ f = 0 } f {if (/^\s*Enable\s*=\s*true/) print "The file: \"'"$l_file"'\" includes: \"" $0 "\" in the \"[xdmcp]\" block"}' "$l_file" done < <(grep -Psil -- '^\h*\[xdmcp\]' /etc/{gdm3,gdm}/{custom,daemon}.conf) } Nothing should be returned Page 249 Internal Only - General Remediation: Edit all files returned by the audit and remove or commend out the Enable=true line in the [xdmcp] block: Example file: # GDM configuration storage # # See /usr/share/gdm/gdm.schemas for a list of available options. [daemon] # Uncomment the line below to force the login screen to use Xorg #WaylandEnable=false # Enabling automatic login # AutomaticLoginEnable = true # AutomaticLogin = user1 # Enabling timed login # TimedLoginEnable = true # TimedLogin = user1 # TimedLoginDelay = 10 [security] [xdmcp] # Enable=true <- **This line should be removed or commented out** [chooser] [debug] # Uncomment the line below to turn on debugging # More verbose logs # Additionally lets the X server dump core if it crashes #Enable=true Default Value: false References: 1. NIST SP 800-53 Rev. 5: SI-4 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. Page 250 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 251 Internal Only - General 1.7.11 Ensure Xwayland is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Xwayland is a compatibility layer that allows legacy X11 applications to run within a Wayland environment. It's effectively an X server that runs as a Wayland client, enabling existing X11 software to be displayed on a Wayland compositor. Rationale: Wayland's security benefits from not relying on X11's network listener. Without X11, there's no network listener, making it harder for malicious actors to exploit vulnerabilities in X11. However, enabling Xwayland (running X11 applications on Wayland) introduces X11's security concerns. All X vulnerabilities apply to Xwayland, including keylogging, but they only affect X windows and interactions with them. Malware can potentially exploit Xwayland vulnerabilities to keylog or intercept other input events Impact: Many applications haven't been ported to Wayland yet, and Xwayland makes it possible to run these applications without requiring a full switch back to X11. Disabling Xwayland functionality may cause these applications to fail. Audit: Run the following command to verify Xwayland is not enabled: # sed -n '/\[daemon\]/,/\[/p' /etc/gdm/custom.conf | grep -Psi '^\h*waylandenable\b' Verify output includes: WaylandEnable=false Page 252 Internal Only - General Remediation: Edit the file /etc/gdm/custom.conf and uncomment or add the following line in the [daemon] block: WaylandEnable=false Example: # GDM configuration storage [daemon] WaylandEnable=false [security] [xdmcp] [chooser] [debug] # Uncomment the line below to turn on debugging #Enable=true Default Value: Enabled CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. 2 Services While applying system updates and patches helps correct known vulnerabilities, one of the best ways to protect the system against as yet unreported vulnerabilities is to disable all services that are not required for normal system operation. This prevents the exploitation of vulnerabilities discovered at a later date. If a service is not enabled, it cannot be exploited. The actions in this section of the document provide guidance on some services which can be safely disabled and under which circumstances, greatly reducing the number of possible threats to the resulting system. Additionally, some services which should remain enabled but with secure configuration are covered as well as insecure service clients. Page 253 Internal Only - General 2.1 Configure Server Services This section describes services that are installed on systems that specifically need to run these services. If any of these services are not required, it is recommended that the package be removed. - IF - the package is required for a dependency: • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy • Stop and mask the service and/or socket to reduce the potential attack surface The following commands can be used to stop and mask the service and socket: # systemctl stop .socket .service # systemctl mask .socket .service Note: This should not be considered a comprehensive list of services not required for normal system operation. You may wish to consider additions to those listed here for your environment Page 254 Internal Only - General 2.1.1 Ensure autofs services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: autofs allows automatic mounting of devices, typically including CD/DVDs and USB drives. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in the filesystem even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users. If your organization allows the use of portable storage or media on workstations and physical access controls to workstations is considered adequate there is little value add in turning off automounting. There may be packages that are dependent on the autofs package. If the autofs package is removed, these dependent packages will be removed as well. Before removing the autofs package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the autofs.service leaving the autofs package installed. Page 255 Internal Only - General Audit: As a preference autofs should not be installed unless other packages depend on it. Run the following command to verify autofs is not installed: # dpkg-query -s autofs &>/dev/null && echo "autofs is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify autofs.service is not enabled: # systemctl is-enabled autofs.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the autofs.service is not active: # systemctl is-active autofs.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop autofs.service and remove the autofs package: # systemctl stop autofs.service # apt purge autofs - OR - - IF - the autofs package is required as a dependency: Run the following commands to stop and mask autofs.service: # systemctl stop autofs.service # systemctl mask autofs.service References: 1. NIST SP 800-53 Rev. 5: SI-3, MP-7 2. RHEL 8 STIG Vul ID: V-230502 3. RHEL 8 STIG Rule ID: SV-230502r627750 Additional Information: This control should align with the tolerance of the use of portable drives and optical media in the organization. On a server, requiring an admin to manually mount media can be part of defense-in-depth to reduce the risk of unapproved software or information being introduced or proprietary software or information being exfiltrated. If admins commonly use flash drives and Server access has sufficient physical controls, requiring manual mounting may not increase security. Page 256 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 257 Internal Only - General 2.1.2 Ensure avahi daemon services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: Avahi is a free zeroconf implementation, including a system for multicast DNS/DNS-SD service discovery. Avahi allows programs to publish and discover services and hosts running on a local network with no specific configuration. For example, a user can plug a computer into a network and Avahi automatically finds printers to print to, files to look at and people to talk to, as well as network services running on the machine. Rationale: Automatic discovery of network services is not normally required for system functionality. It is recommended to remove this package to reduce the potential attack surface. Impact: There may be packages that are dependent on the avahi package. If the avahi package is removed, these dependent packages will be removed as well. Before removing the avahi package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the avahi-daemon.socket and avahi-daemon.service leaving the avahi package installed. Page 258 Internal Only - General Audit: Run the following command to verify avahi-daemon is not installed: # dpkg-query -s avahi-daemon &>/dev/null && echo "avahi-daemon is installed" Nothing should be returned. - OR - - IF - the avahi package is required as a dependency: Run the following command to verify avahi-daemon.socket and avahi- daemon.service are not enabled: # systemctl is-enabled avahi-daemon.socket avahi-daemon.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify avahi-daemon.socket and avahi- daemon.service are not active: # systemctl is-active avahi-daemon.socket avahi-daemon.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop avahi-daemon.socket and avahi- daemon.service, and remove the avahi-daemon package: # systemctl stop avahi-daemon.socket avahi-daemon.service # apt purge avahi-daemon - OR - - IF - the avahi-daemon package is required as a dependency: Run the following commands to stop and mask the avahi-daemon.socket and avahi- daemon.service: # systemctl stop avahi-daemon.socket avahi-daemon.service # systemctl mask avahi-daemon.socket avahi-daemon.service References: 1. NIST SP 800-53 Rev. 5: SI-4 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. Page 259 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 260 Internal Only - General 2.1.3 Ensure dhcp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Dynamic Host Configuration Protocol (DHCP) is a service that allows machines to be dynamically assigned IP addresses. There are two versions of the DHCP protocol DHCPv4 and DHCPv6. At startup the server may be started for one or the other via the -4 or -6 arguments. Rationale: Unless a system is specifically set up to act as a DHCP server, it is recommended that the kea package be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the kea package. If the kea package is removed, these dependent packages will be removed as well. Before removing the kea package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the kea-dhcp-ddns- server.service kea-dhcp4-server.service and kea-dhcp6-server.service leaving the kea package installed. Audit: Run the following command to verify kea is not installed: # dpkg-query -l | awk '{print $2}' | grep -Pio -- 'kea' &>/dev/null && echo "kea is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify kea-dhcp-ddns-server.service kea-dhcp4- server.service kea-dhcp6-server.service UnitFileState is not enabled and ActiveState is not active: # systemctl show kea-dhcp-ddns-server.service kea-dhcp4-server.service kea- dhcp6-server.service -p UnitFileState,ActiveState | grep -Pi '=(enabled|active)' Nothing should be returned. Page 261 Internal Only - General Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop kea-dhcp-ddns-server.service kea-dhcp4- server.service kea-dhcp6-server.service and remove kea package: # systemctl stop kea-dhcp-ddns-server.service kea-dhcp4-server.service kea- dhcp6-server.service # apt remove kea - OR - - IF - the kea package is required as a dependency: Run the following commands to stop and mask dhcpd.service and dhcpd6.service: # systemctl stop kea-dhcp-ddns-server.service kea-dhcp4-server.service kea- dhcp6-server.service # systemctl stop kea-dhcp-ddns-server.service kea-dhcp4-server.service kea- dhcp6-server.service References: 1. dhcpd(8) 2. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 262 Internal Only - General 2.1.4 Ensure dns server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Domain Name System (DNS) is a hierarchical naming system that maps names to IP addresses for computers, services and other resources connected to a network. Note: bind9 is the package and bind.service is the alias for named.service. Rationale: Unless a system is specifically designated to act as a DNS server, it is recommended that the package be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the bind9 package. If the bind9 package is removed, these dependent packages will be removed as well. Before removing the bind9 package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask named.service leaving the bind9 package installed. Audit: Run the following command to verify bind9 is not installed: # dpkg-query -s bind9 &>/dev/null && echo "bind9 is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify named.service is not enabled: # systemctl is-enabled named.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the named.service is not active: # systemctl is-active named.service 2>/dev/null | grep '^active' Nothing should be returned Page 263 Internal Only - General Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop named.service and remove the bind9 package: # systemctl stop named.service # apt purge bind9 - OR - - IF - the bind9 package is required as a dependency: Run the following commands to stop and mask bind9.service: # systemctl stop named.service # systemctl mask named.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 264 Internal Only - General 2.1.5 Ensure dnsmasq services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: dnsmasq is a lightweight tool that provides DNS caching, DNS forwarding and DHCP (Dynamic Host Configuration Protocol) services. Rationale: Unless a system is specifically designated to act as a DNS caching, DNS forwarding and/or DHCP server, it is recommended that the package be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the dnsmasq package. If the dnsmasq package is removed, these dependent packages will be removed as well. Before removing the dnsmasq package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the dnsmasq.service leaving the dnsmasq package installed. Audit: Run one of the following commands to verify dnsmasq is not installed: # dpkg-query -s dnsmasq &>/dev/null && echo "dnsmasq is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify dnsmasq.service is not enabled: # systemctl is-enabled dnsmasq.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the dnsmasq.service is not active: # systemctl is-active dnsmasq.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop dnsmasq.service and remove dnsmasq package: Page 265 Internal Only - General # systemctl stop dnsmasq.service # apt purge dnsmasq - OR - - IF - the dnsmasq package is required as a dependency: Run the following commands to stop and mask the dnsmasq.service: # systemctl stop dnsmasq.service # systemctl mask dnsmasq.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 266 Internal Only - General 2.1.6 Ensure ftp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The File Transfer Protocol (FTP) provides networked computers with the ability to transfer files. vsftpd is the Very Secure File Transfer Protocol Daemon. Rationale: FTP does not protect the confidentiality of data or authentication credentials. It is recommended SFTP be used if file transfer is required. Unless there is a need to run the system as a FTP server (for example, to allow anonymous downloads), it is recommended that the package be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the vsftpd package. If the vsftpd package is removed, these dependent packages will be removed as well. Before removing the vsftpd package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the vsftpd.service leaving the vsftpd package installed. Audit: Run the following command to verify the vsftpd package is not installed: # dpkg-query -s vsftpd &>/dev/null && echo "vsftpd is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify vsftpd service is not enabled: # systemctl is-enabled vsftpd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the vsftpd service is not active: # systemctl is-active vsftpd.service 2>/dev/null | grep '^active' Nothing should be returned. Page 267 Internal Only - General Note: • Other ftp server packages may exist. They should also be audited, if not required and authorized by local site policy • If the package is required for a dependency: o Ensure the dependent package is approved by local site policy o Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop vsftpd.service and remove the vsftpd package: # systemctl stop vsftpd.service # apt purge vsftpd - OR - - IF - the vsftpd package is required as a dependency: Run the following commands to stop and mask the vsftpd.service: # systemctl stop vsftpd.service # systemctl mask vsftpd.service Note: Other ftp server packages may exist. If not required and authorized by local site policy, they should also be removed. If the package is required for a dependency, the service should be stopped and masked. References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Additional FTP servers also exist and should be audited. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 268 Internal Only - General 2.1.7 Ensure ldap server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP server, it is recommended that the software be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the slapd package. If the slapd package is removed, these dependent packages will be removed as well. Before removing the slapd package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the slapd.service leaving the slapd package installed. Audit: Run the following command to verify slapd is not installed: # dpkg-query -s slapd &>/dev/null && echo "slapd is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify slapd.service is not enabled: # systemctl is-enabled slapd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify slapd.service is not active: # systemctl is-active slapd.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop slapd.service and remove the slapd package: Page 269 Internal Only - General # systemctl stop slapd.service # apt purge slapd - OR - - IF - the slapd package is required as a dependency: Run the following commands to stop and mask slapd.service: # systemctl stop slapd.service # systemctl mask slapd.service References: 1. For more detailed documentation on OpenLDAP, go to the project homepage at http://www.openldap.org. 2. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 270 Internal Only - General 2.1.8 Ensure message access server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: dovecot-imapd and dovecot-pop3d are an open source IMAP and POP3 server for Linux based systems. Rationale: Unless POP3 and/or IMAP servers are to be provided by this system, it is recommended that the package be removed to reduce the potential attack surface. Note: Several IMAP/POP3 servers exist and can use other service names. These should also be audited and the packages removed if not required. Impact: There may be packages that are dependent on dovecot-imapd and/or dovecot-pop3d packages. If dovecot-imapd and dovecot-pop3d packages are removed, these dependent packages will be removed as well. Before removing dovecot-imapd and/or dovecot-pop3d packages, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask dovecot.socket and dovecot.service leaving dovecot-imapd and/or dovecot-pop3d packages installed. Page 271 Internal Only - General Audit: Run the following command to verify dovecot-imapd and dovecot-pop3d are not installed: # dpkg-query -s dovecot-imapd &>/dev/null && echo "dovecot-imapd is installed" Nothing should be returned. # dpkg-query -s dovecot-pop3d &>/dev/null && echo "dovecot-pop3d is installed" Nothing should be returned. - OR - - IF - a package is installed and is required for dependencies: Run the following commands to verify dovecot.socket and dovecot.service are not enabled: # systemctl is-enabled dovecot.socket dovecot.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify dovecot.socket and dovecot.service are not active: # systemctl is-active dovecot.socket dovecot.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 272 Internal Only - General Remediation: Run one of the following commands to remove dovecot-imapd and dovecot-pop3d: Run the following commands to stop dovecot.socket and dovecot.service, and remove the dovecot-imapd and dovecot-pop3d packages: # systemctl stop dovecot.socket dovecot.service # apt purge dovecot-imapd dovecot-pop3d - OR - - IF - a package is installed and is required for dependencies: Run the following commands to stop and mask dovecot.socket and dovecot.service: # systemctl stop dovecot.socket dovecot.service # systemctl mask dovecot.socket dovecot.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Several IMAP/POP3 servers exist and can use other service names. courier-imap and cyrus-imap are example services that provide a mail server. These and other services should also be audited. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 273 Internal Only - General 2.1.9 Ensure network file system services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network File System (NFS) is one of the first and most widely distributed file systems in the UNIX environment. It provides the ability for systems to mount file systems of other servers through the network. Rationale: If the system does not export NFS shares, it is recommended that the nfs-kernel- server package be removed to reduce the remote attack surface. Impact: There may be packages that are dependent on the nfs-kernel-server package. If the nfs-kernel-server package is removed, these dependent packages will be removed as well. Before removing the nfs-kernel-server package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the nfs-server.service leaving the nfs-kernel-server package installed. Audit: Run the following command to verify nfs-kernel-server is not installed: # dpkg-query -s nfs-kernel-server &>/dev/null && echo "nfs-kernel-server is installed" Nothing should be returned. - OR - - IF - package is required for dependencies: Run the following command to verify that the nfs-server.service is not enabled: # systemctl is-enabled nfs-server.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the nfs-server.service is not active: # systemctl is-active nfs-server.service 2>/dev/null | grep '^active' Nothing should be returned. Page 274 Internal Only - General Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following command to stop nfs-server.service and remove nfs-kernel- server package: # systemctl stop nfs-server.service # apt purge nfs-kernel-server - OR - - IF - the nfs-kernel-server package is required as a dependency: Run the following commands to stop and mask the nfs-server.service: # systemctl stop nfs-server.service # systemctl mask nfs-server.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 275 Internal Only - General 2.1.10 Ensure nis server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network Information Service (NIS) (formally known as Yellow Pages) is a client- server directory service protocol for distributing system configuration files. The NIS server is a collection of programs that allow for the distribution of configuration files. The NIS client (ypbind) was used to bind a machine to an NIS server and receive the distributed configuration files. Rationale: ypserv.service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that ypserv.service be removed and other, more secure services be used Impact: There may be packages that are dependent on the ypserv package. If the ypserv package is removed, these dependent packages will be removed as well. Before removing the ypserv package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the ypserv.service leaving the ypserv package installed. Audit: Run the following command to verify ypserv is not installed: # dpkg-query -s ypserv &>/dev/null && echo "ypserv is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify ypserv.service is not enabled: # systemctl is-enabled ypserv.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify ypserv.service is not active: # systemctl is-active ypserv.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy Page 276 Internal Only - General • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop ypserv.service and remove ypserv package: # systemctl stop ypserv.service # apt purge ypserv - OR - - IF - the ypserv package is required as a dependency: Run the following commands to stop and mask ypserv.service: # systemctl stop ypserv.service # systemctl mask ypserv.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 277 Internal Only - General 2.1.11 Ensure print server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: The Common Unix Print System (CUPS) provides the ability to print to both local and network printers. A system running CUPS can also accept print jobs from remote systems and print them to local printers. It also provides a web based remote administration capability. Rationale: If the system does not need to print jobs or accept print jobs from other systems, it is recommended that CUPS be removed to reduce the potential attack surface. Impact: Removing the cups package, or disabling cups.socket and/or cups.service will prevent printing from the system, a common task for workstation systems. There may be packages that are dependent on the cups package. If the cups package is removed, these dependent packages will be removed as well. Before removing the cups package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask cups.socket and cups.service leaving the cups package installed. Audit: Run the following command to verify cups is not Installed: # dpkg-query -s cups &>/dev/null && echo "cups is installed" Nothing should be returned. - OR - - IF - the cups package is required as a dependency: Run the following command to verify the cups.socket and cups.service are not enabled: # systemctl is-enabled cups.socket cups.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the cups.socket and cups.service are not active: # systemctl is-active cups.socket cups.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy Page 278 Internal Only - General • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop cups.socket and cups.service, and remove the cups package: # systemctl stop cups.socket cups.service # apt purge cups - OR - - IF - the cups package is required as a dependency: Run the following commands to stop and mask the cups.socket and cups.service: # systemctl stop cups.socket cups.service # systemctl mask cups.socket cups.service References: 1. http://www.cups.org 2. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 279 Internal Only - General 2.1.12 Ensure rpcbind services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they expect to serve. The client system then contacts rpcbind on the server with a particular RPC program number. The rpcbind.service redirects the client to the proper port number so it can communicate with the requested service. Portmapper is an RPC service, which always listens on tcp and udp 111, and is used to map other RPC services (such as nfs, nlockmgr, quotad, mountd, etc.) to their corresponding port number on the server. When a remote host makes an RPC call to that server, it first consults with portmap to determine where the RPC server is listening. Rationale: A small request (~82 bytes via UDP) sent to the Portmapper generates a large response (7x to 28x amplification), which makes it a suitable tool for DDoS attacks. If rpcbind is not required, it is recommended to remove rpcbind package to reduce the potential attack surface. Impact: Many of the libvirt packages used by Enterprise Linux virtualization, and the nfs-utils package used for The Network File System (NFS), are dependent on the rpcbind package. If the rpcbind package is removed, these dependent packages will be removed as well. Before removing the rpcbind package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the rpcbind.socket and rpcbind.service leaving the rpcbind package installed. Page 280 Internal Only - General Audit: Run the following command to verify rpcbind package is not installed: # dpkg-query -s rpcbind &>/dev/null && echo "rpcbind is installed" Nothing should be returned. - OR - - IF - the rpcbind package is required as a dependency: Run the following command to verify rpcbind.socket and rpcbind.service are not enabled: # systemctl is-enabled rpcbind.socket rpcbind.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify rpcbind.socket and rpcbind.service are not active: # systemctl is-active rpcbind.socket rpcbind.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop rpcbind.socket and rpcbind.service, and remove the rpcbind package: # systemctl stop rpcbind.socket rpcbind.service # apt purge rpcbind - OR - - IF - the rpcbind package is required as a dependency: Run the following commands to stop and mask the rpcbind.socket and rpcbind.service: # systemctl stop rpcbind.socket rpcbind.service # systemctl mask rpcbind.socket rpcbind.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. Page 281 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 282 Internal Only - General 2.1.13 Ensure rsync services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsync service can be used to synchronize files between systems over network links. Rationale: rsync.service presents a security risk as the rsync protocol is unencrypted. The rsync package should be removed to reduce the attack area of the system. Impact: There may be packages that are dependent on the rsync package. If the rsync package is removed, these dependent packages will be removed as well. Before removing the rsync package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask rsync.service leaving the rsync package installed. Audit: Run the following command to verify rsync is not installed: # dpkg-query -s rsync &>/dev/null && echo "rsync is installed" Nothing should be returned. - OR - - IF - the rsync package is required as a dependency: Run the following command to verify rsync.service is not enabled: # systemctl is-enabled rsync.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify rsync.service is not active: # systemctl is-active rsync.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop rsync.service, and remove the rsync package: Page 283 Internal Only - General # systemctl stop rsync.service # apt purge rsync - OR - - IF - the rsync package is required as a dependency: Run the following commands to stop and mask rsync.service: # systemctl stop rsync.service # systemctl mask rsync.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 284 Internal Only - General 2.1.14 Ensure samba file server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Samba daemon allows system administrators to configure their Linux systems to share file systems and directories with Windows desktops. Samba will advertise the file systems and directories via the Server Message Block (SMB) protocol. Windows desktop users will be able to mount these directories and file systems as letter drives on their systems. Rationale: If there is no need to mount directories and file systems to Windows systems, then this service should be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the samba package. If the samba package is removed, these dependent packages will be removed as well. Before removing the samba package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the smbd.service leaving the samba package installed. Audit: Run the following command to verify samba is not installed: # dpkg-query -s samba &>/dev/null && echo "samba is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify smbd.service is not enabled: # systemctl is-enabled smbd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the smbd.service is not active: # systemctl is-active smbd.service 2>/dev/null | grep '^active' Nothing should be returned. Remediation: Run the following commands to stop smbd.service and remove samba package: Page 285 Internal Only - General # systemctl stop smbd.service # apt purge samba - OR - - IF - the samba package is required as a dependency: Run the following commands to stop and mask the smbd.service: # systemctl stop smbd.service # systemctl mask smbd.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 286 Internal Only - General 2.1.15 Ensure snmp services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Simple Network Management Protocol (SNMP) is a widely used protocol for monitoring the health and welfare of network equipment, computer equipment and devices like UPSs. Net-SNMP is a suite of applications used to implement SNMPv1 (RFC 1157), SNMPv2 (RFCs 1901-1908), and SNMPv3 (RFCs 3411-3418) using both IPv4 and IPv6. Support for SNMPv2 classic (a.k.a. "SNMPv2 historic" - RFCs 1441-1452) was dropped with the 4.0 release of the UCD-snmp package. The Simple Network Management Protocol (SNMP) server is used to listen for SNMP commands from an SNMP management system, execute the commands or collect the information and then send results back to the requesting system. Rationale: The SNMP server can communicate using SNMPv1, which transmits data in the clear and does not require authentication to execute commands. SNMPv3 replaces the simple/clear text password sharing used in SNMPv2 with more securely encoded parameters. If the the SNMP service is not required, the snmpd package should be removed to reduce the attack surface of the system. Note: If SNMP is required: • The server should be configured for SNMP v3 only. User Authentication and Message Encryption should be configured. • If SNMP v2 is absolutely necessary, modify the community strings' values. Impact: There may be packages that are dependent on the snmpd package. If the snmpd package is removed, these packages will be removed as well. Before removing the snmpd package, review any dependent packages to determine if they are required on the system. If a dependent package is required, stop and mask the snmpd.service leaving the snmpd package installed. Page 287 Internal Only - General Audit: Run the following command to verify snmpd is not installed: # dpkg-query -s snmpd &>/dev/null && echo "snmpd is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify the snmpd.service is not enabled: # systemctl is-enabled snmpd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the snmpd.service is not active: # systemctl is-active snmpd.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop snmpd.service and remove the snmpd package: # systemctl stop snmpd.service # apt purge snmpd - OR - If the package is required for dependencies: Run the following commands to stop and mask the snmpd.service: # systemctl stop snmpd.service # systemctl mask snmpd.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 288 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 289 Internal Only - General 2.1.16 Ensure telnet-server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The telnetd package contains the telnet daemon, which accepts connections from users from other systems via the telnet protocol. Rationale: The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow a user with access to sniff network traffic the ability to steal credentials. The ssh package provides an encrypted session and stronger security. Impact: There may be packages that are dependent on the telnetd package. If the telnetd package is removed, these dependent packages will be removed as well. Before removing the telnetd package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask inetutils-inetd.service leaving the telnetd package installed. Audit: Run the following command to verify telnetd is not installed: # dpkg-query -l | awk '{print $2}' | grep -Pio -- '^telnetd|^telnetd-ssl' &>/dev/null && echo "telnetd is installed" Nothing should be returned. - OR - - IF - the telnetd package is required as a dependency: Run the following command to verify inetutils-inetd.service is not enabled: # systemctl is-enabled inetutils-inetd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify inetutils-inetd.service is not active: # systemctl is-active inetutils-inetd.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 290 Internal Only - General Remediation: Run the following commands to stop inetutils-inetd.service, and remove the telnetd package: # systemctl stop inetutils-inetd.service # apt purge telnetd - OR - - IF - the telnetd package is required as a dependency: Run the following commands to stop and mask inetutils-inetd.service: # systemctl stop inetutils-inetd.service # systemctl mask inetutils-inetd.service CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 2.6 Address unapproved software v7 Ensure that unauthorized software is either removed or the inventory is ● ● ● updated in a timely manner 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 291 Internal Only - General 2.1.17 Ensure tftp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Trivial File Transfer Protocol (TFTP) is a simple protocol for exchanging files between two TCP/IP machines. TFTP servers allow connections from a TFTP Client for sending and receiving files. Rationale: Unless there is a need to run the system as a TFTP server, it is recommended that the package be removed to reduce the potential attack surface. TFTP does not have built-in encryption, access control or authentication. This makes it very easy for an attacker to exploit TFTP to gain access to files Impact: TFTP is often used to provide files for network booting such as for PXE based installation of servers. There may be packages that are dependent on the tftpd-hpa package. If the tftpd- hpa package is removed, these dependent packages will be removed as well. Before removing the tftpd-hpa package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask tftpd-hpa.service leaving the tftpd-hpa package installed. Audit: Run the following command to verify tftpd-hpa is not installed: # dpkg-query -s tftpd-hpa &>/dev/null && echo "tftpd-hpa is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify tftpd-hpa.service is not enabled: # systemctl is-enabled tftpd-hpa.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the tftpd-hpa.service is not active: # systemctl is-active tftpd-hpa.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 292 Internal Only - General Remediation: Run the following commands to stop tftpd-hpa.service, and remove the tftpd-hpa package: # systemctl stop tftpd-hpa.service # apt purge tftpd-hpa - OR - - IF - the tftpd-hpa package is required as a dependency: Run the following commands to stop and mask tftpd-hpa.service: # systemctl stop tftpd-hpa.service # systemctl mask tftpd-hpa.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 293 Internal Only - General 2.1.18 Ensure web proxy server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Squid is a standard proxy server used in many distributions and environments. Rationale: Unless a system is specifically set up to act as a proxy server, it is recommended that the squid package be removed to reduce the potential attack surface. Note: Several HTTP proxy servers exist. These should be checked and removed unless required. Impact: There may be packages that are dependent on the squid package. If the squid package is removed, these dependent packages will be removed as well. Before removing the squid package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the squid.service leaving the squid package installed. Audit: Run the following command to verify squid is not installed: # dpkg-query -s squid &>/dev/null && echo "squid is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify squid.service is not enabled: # systemctl is-enabled squid.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the squid.service is not active: # systemctl is-active squid.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop squid.service and remove the squid package: Page 294 Internal Only - General # systemctl stop squid.service # apt purge squid - OR - If the squid package is required as a dependency: Run the following commands to stop and mask the squid.service: # systemctl stop squid.service # systemctl mask squid.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Several HTTP proxy servers exist. These and other services should be checked CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 295 Internal Only - General 2.1.19 Ensure web server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Web servers provide the ability to host web site content. Rationale: Unless there is a local site approved requirement to run a web server service on the system, web server packages should be removed to reduce the potential attack surface. Impact: Removal of a web server's package, or changing the state of its service and/or socket, will prevent the server from hosting web services. - IF - a web server package is required for a dependency, any related service or socket should be stopped and masked. Note: If the remediation steps to mask a service are followed and that package is not installed on the system, the service and/or socket will still be masked. If the package is installed due to an approved requirement to host a web server, the associated service and/or socket would need to be unmasked before it could be enabled and/or started. Page 296 Internal Only - General Audit: Run the following command to verify apache2 is not installed: # dpkg-query -s apache2 &>/dev/null && echo "apache2 is installed" Nothing should be returned. Run the following command to verify nginx is not installed: # dpkg-query -s nginx &>/dev/null && echo "nginx is installed" Nothing should be returned. - OR - - IF - a package is installed and is required for dependencies: - IF - the apache2 package is required for dependencies: Run the following command to verify apache2.socket and apache2.service UnitFileState is not enabled and ActiveState is not active: # systemctl show apache2.socket apache2.service -p UnitFileState,ActiveState | grep -Pi '=(enabled|active)' Nothing should be returned - IF - the nginx package is required for dependencies: Run the following command to verify nginx.service UnitFileState is not enabled and ActiveState is not active: # systemctl show nginx.service -p UnitFileState,ActiveState | grep -Pi '=(enabled|active)' Nothing should be returned Note: • Other web server packages may exist. They should also be audited, if not required and authorized by local site policy • If the package is required for a dependency: o Ensure the dependent package is approved by local site policy o Ensure stopping and masking the service and/or socket meets local site policy Page 297 Internal Only - General Remediation: Run the following commands to stop apache2.socket, apache2.service and remove the apache2 package: # systemctl stop apache2.socket apache2.service # apt purge apache2 Run the following commands to stop nginx.service and remove the nginx package: # systemctl stop nginx.service # apt purge nginx - OR - - IF - a package is installed and is required for dependencies: - IF - the apache2 package is required for dependencies: Run the following commands to stop and mask apache2.socket and apache2.service: # systemctl stop apache2.socket apache2.service # systemctl mask apache2.socket apache2.service - IF - the nginx package is required for dependencies: Run the following commands to stop and mask nginx.service: # systemctl stop nginx.service # systemctl mask nginx.service Note: Other web server packages may exist. If not required and authorized by local site policy, they should also be removed. If the package is required for a dependency, the service and socket should be stopped and masked. References: 1. NIST SP 800-53 :: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 298 Internal Only - General 2.1.20 Ensure xinetd services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The eXtended InterNET Daemon (xinetd) is an open source super daemon that replaced the original inetd daemon. The xinetd daemon listens for well known services and dispatches the appropriate daemon to properly respond to service requests. Rationale: If there are no xinetd services required, it is recommended that the package be removed to reduce the attack surface are of the system. Note: If an xinetd service or services are required, ensure that any xinetd service not required is stopped and masked Impact: There may be packages that are dependent on the xinetd package. If the xinetd package is removed, these dependent packages will be removed as well. Before removing the xinetd package, review any dependent packages to determine if they are required on the system. -IF- a dependent package is required: stop and mask xinetd.service leaving the xinetd package installed. Page 299 Internal Only - General Audit: Run the following command to verify the xinetd package is not installed: # dpkg-query -s xinetd &>/dev/null && echo "xinetd is installed" Nothing should be returned. -OR- -IF- the xinetd package is required as a dependency: Run the following command to verify xinetd.service is not enabled: # systemctl is-enabled xinetd.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify xinetd.service is not active: # systemctl is-active xinetd.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop xinetd.service, and remove the xinetd package: # systemctl stop xinetd.service # apt purge xinetd -OR- -IF- the xinetd package is required as a dependency: Run the following commands to stop and mask the xinetd.service: # systemctl stop xinetd.service # systemctl mask xinetd.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 300 Internal Only - General Page 301 Internal Only - General 2.1.21 Ensure X window server services are not in use (Automated) Profile Applicability: • Level 2 - Server Description: The X Window System provides a Graphical User Interface (GUI) where users can have multiple windows in which to run programs and various add on. The X Windows system is typically used on workstations where users login, but not on servers where users typically do not login. Rationale: Unless your organization specifically requires graphical login access via X Windows, remove it to reduce the potential attack surface. Impact: If a Graphical Desktop Manager (GDM) is in use on the system, there may be a dependency on the xorg-x11-server-common package. If the GDM is required and approved by local site policy, the package should not be removed. Many Linux systems run applications which require a Java runtime. Some Linux Java packages have a dependency on specific X Windows xorg-x11-fonts. One workaround to avoid this dependency is to use the "headless" Java packages for your specific Java runtime. Audit: - IF - a Graphical Desktop Manager or X-Windows server is not required and approved by local site policy: Run the following command to Verify X Windows Server is not installed. dpkg-query -s xserver-common &>/dev/null && echo "xserver-common is installed" Nothing should be returned Remediation: - IF - a Graphical Desktop Manager or X-Windows server is not required and approved by local site policy: Run the following command to remove the X Windows Server package: # apt purge xserver-common References: 1. NIST SP 800-53 Rev. 5: CM-11 Page 302 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 2.6 Address unapproved software v7 Ensure that unauthorized software is either removed or the inventory is ● ● ● updated in a timely manner Page 303 Internal Only - General 2.1.22 Ensure mail transfer agents are configured for local-only mode (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Mail Transfer Agents (MTA), such as sendmail and Postfix, are used to listen for incoming mail and transfer the messages to the appropriate user or mail server. If the system is not intended to be a mail server, it is recommended that the MTA be configured to only process local mail. Rationale: The software for all Mail Transfer Agents is complex and most have a long history of security issues. While it is important to ensure that the system can process local mail messages, it is not necessary to have the MTA's daemon listening on a port unless the server is intended to be a mail server that receives and processes mail from other systems. Impact: This recommendation is designed around the postfix mail server. Depending on your environment you may have an alternative MTA installed such as exim4 or sendmail. If this is the case consult the documentation for your installed MTA to configure the recommended state. Audit: Run the following script to verify that the MTA is not listening on any non-loopback address ( 127.0.0.1 or ::1 ) Page 304 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=(); a_port_list=("25" "465" "587") for l_port_number in "${a_port_list[@]}"; do if ss -plntu | grep -P -- ':'"$l_port_number"'\b' | grep -Pvq -- '\h+(127\.0\.0\.1|\[?::1\]?):'"$l_port_number"'\b'; then a_output2+=(" - Port \"$l_port_number\" is listening on a non- loopback network interface") else a_output+=(" - Port \"$l_port_number\" is not listening on a non- loopback network interface") fi done if command -v postconf &> /dev/null; then l_interfaces="$(postconf -n inet_interfaces)" elif command -v exim &> /dev/null; then l_interfaces="$(exim -bP local_interfaces)" elif command -v sendmail &> /dev/null; then l_interfaces="$(grep -i "O DaemonPortOptions=" /etc/mail/sendmail.cf | grep -oP '(?<=Addr=)[^,+]+' | grep -v '^127\.0\.0\.1$')" fi if [ -n "$l_interfaces" ]; then if grep -Pqi '\ball\b' <<< "$l_interfaces"; then a_output2+=(" - MTA is bound to all network interfaces") elif ! grep -Pqi '(inet_interfaces\h*=\h*)?(0\.0\.0\.0|::1|loopback- only)' <<< "$l_interfaces"; then a_output2+=(" - MTA is bound to a network interface" " \"$l_interfaces\"") else a_output+=(" - MTA is not bound to a non loopback network interface" " \"$l_interfaces\"") fi else a_output+=(" - MTA not detected or in use") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 305 Internal Only - General Remediation: Edit /etc/postfix/main.cf and add the following line to the RECEIVING MAIL section. If the line already exists, change it to look like the line below: inet_interfaces = loopback-only Run the following command to restart postfix: # systemctl restart postfix Note: • This recommendation is designed around the postfix mail server. • Depending on your environment you may have an alternative MTA installed such as exim4 or sendmail. If this is the case consult the documentation for your installed MTA to configure the recommended state. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 306 Internal Only - General 2.1.23 Ensure only approved services are listening on a network interface (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A network port is identified by its number, the associated IP address, and the type of the communication protocol such as TCP or UDP. A listening port is a network port on which an application or process listens on, acting as a communication endpoint. Each listening port can be open or closed (filtered) using a firewall. In general terms, an open port is a network port that accepts incoming packets from remote locations. Rationale: Services listening on the system pose a potential risk as an attack vector. These services should be reviewed, and if not required, the service should be stopped, and the package containing the service should be removed. If required packages have a dependency, the service should be stopped and masked to reduce the attack surface of the system. Impact: There may be packages that are dependent on the service's package. If the service's package is removed, these dependent packages will be removed as well. Before removing the service's package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the .socket and .service leaving the service's package installed. Audit: Run the following command: # ss -plntu Review the output to ensure: • All services listed are required on the system and approved by local site policy. • Both the port and interface the service is listening on are approved by local site policy. • If a listed service is not required: o Remove the package containing the service o - IF - the service's package is required for a dependency, stop and mask the service and/or socket Page 307 Internal Only - General Remediation: Run the following commands to stop the service and remove the package containing the service: # systemctl stop .socket .service # apt purge - OR - If required packages have a dependency: Run the following commands to stop and mask the service and socket: # systemctl stop .socket .service # systemctl mask .socket .service Note: replace with the appropriate service name. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 308 Internal Only - General 2.2 Configure Client Services A number of insecure services exist. While disabling the servers prevents a local attack against these services, it is advised to remove their clients unless they are required. Note: This should not be considered a comprehensive list of insecure service clients. You may wish to consider additions to those listed here for your environment. Page 309 Internal Only - General 2.2.1 Ensure nis client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network Information Service (NIS), formerly known as Yellow Pages, is a client- server directory service protocol used to distribute system configuration files. The NIS client was used to bind a machine to an NIS server and receive the distributed configuration files. Rationale: The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that the service be removed. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify nis is not installed. Use the following command to provide the needed information: # dpkg-query -s nis &>/dev/null && echo "nis is installed" Nothing should be returned. Remediation: Uninstall nis: # apt purge nis References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 Page 310 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 2.6 Address unapproved software v7 Ensure that unauthorized software is either removed or the inventory is ● ● ● updated in a timely manner Page 311 Internal Only - General 2.2.2 Ensure rsh client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsh-client package contains the client commands for the rsh services. Rationale: These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inadvertently attempting to use these commands and therefore exposing their credentials. Note that removing the rsh- client package removes the clients for rsh , rcp and rlogin . Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify rsh-client is not installed. Use the following command to provide the needed information: # dpkg-query -s rsh-client &>/dev/null && echo "rsh-client is installed" Nothing should be returned. Remediation: Uninstall rsh: # apt purge rsh-client References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on v8 Enterprise Assets and Software ● ● Uninstall or disable unnecessary services on enterprise assets and software, Page 312 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 313 Internal Only - General 2.2.3 Ensure talk client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The talk software makes it possible for users to send and receive messages across systems through a terminal session. The talk client, which allows initialization of talk sessions, is installed by default. Rationale: The software presents a security risk as it uses unencrypted protocols for communication. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify talk is not installed. The following command may provide the needed information: # dpkg-query -s talk &>/dev/null && echo "talk is installed" Nothing should be returned. Remediation: Uninstall talk: # apt purge talk References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. Page 314 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 315 Internal Only - General 2.2.4 Ensure telnet client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The inetutils-telnet package contains the telnet client, which allows users to start connections to other systems via the telnet protocol. Rationale: The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in most Linux distributions. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify inetutils-telnet & telnet are not installed. Use the following command to provide the needed information: # dpkg-query -l | grep -E 'telnet|inetutils-telnet' &>/dev/null && echo "telnet is installed" Nothing should be returned. Remediation: Run the following commands to uninstall telnet & inetutils-telnet: # apt purge telnet # apt purge inetutils-telnet References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on v8 Enterprise Assets and Software ● ● Page 316 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Uninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 317 Internal Only - General 2.2.5 Ensure ldap client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP client, it is recommended that the software be removed to reduce the potential attack surface. Impact: Removing the LDAP client will prevent or inhibit using LDAP for authentication in your environment. Audit: Verify that ldap-utils is not installed. Use the following command to provide the needed information: # dpkg-query -s ldap-utils &>/dev/null && echo "ldap-utils is installed" Nothing should be returned. Remediation: Uninstall ldap-utils: # apt purge ldap-utils References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 318 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 319 Internal Only - General 2.2.6 Ensure ftp client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: tnftp an enhanced FTP client, is the user interface to the Internet standard File Transfer Protocol. The program allows a user to transfer files to and from a remote network site. Rationale: Unless there is a need to run the system using Internet standard File Transfer Protocol (for example, to allow anonymous downloads), it is recommended that the package be removed to reduce the potential attack surface. Audit: Run the following command to verify the tnftp and ftp packages are not installed: # dpkg-query -l | awk '{print $2}' 2>&1 | grep -Pqs -- '^(ftp|tnftp)' && echo "ftp is installed" ftp is installed Nothing should be returned. Remediation: Run the following commands to uninstall the tnftp and ftp packages: # apt purge ftp # apt purge tnftp References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 Page 320 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 321 Internal Only - General 2.3 Configure Time Synchronization It is recommended that systems be configured to synchronize their time using a service such as systemd-timesyncd, or chrony. Virtual systems may be configured to receive their time synchronization from their host system. The host system must be configured to synchronize its time from an authoritative source to be considered compliant with this section. Any "physical" clock present on a system should be synchronized from an authoritative time source. Only one time synchronization method should be in use on the system Notes: Only the section related to the time synchronization method in use on the system should be followed, all other time synchronization recommendations should be skipped Page 322 Internal Only - General 2.3.1 Ensure time synchronization is in use It is recommended that physical systems and virtual guests lacking direct access to the physical host's clock be configured to synchronize their time using a service such as systemd-timesyncd, or chrony. Page 323 Internal Only - General 2.3.1.1 Ensure a single time synchronization daemon is in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize their clocks to them. Note: • On virtual systems where host based time synchronization is available consult your virtualization software documentation and verify that host based synchronization is in use and follows local site policy. In this scenario, this section should be skipped • Only one time synchronization method should be in use on the system. Configuring multiple time synchronization methods could lead to unexpected or unreliable results Rationale: Time synchronization is important to support time sensitive security mechanisms and ensures log files have consistent time records across the enterprise, which aids in forensic investigations. Audit: On physical systems, and virtual systems where host based time synchronization is not available. One of the two time synchronization daemons should be available; chrony or systemd- timesyncd Run the following script to verify that a single time synchronization daemon is available on the system: Page 324 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" service_not_enabled_chk() { l_out2="" if systemctl is-enabled "$l_service_name" 2>/dev/null | grep -q 'enabled'; then l_out2="$l_out2\n - Daemon: \"$l_service_name\" is enabled on the system" fi if systemctl is-active "$l_service_name" 2>/dev/null | grep -q '^active'; then l_out2="$l_out2\n - Daemon: \"$l_service_name\" is active on the system" fi } l_service_name="systemd-timesyncd.service" # Check systemd-timesyncd daemon service_not_enabled_chk if [ -n "$l_out2" ]; then l_timesyncd="y" l_out_tsd="$l_out2" else l_timesyncd="n" l_out_tsd="\n - Daemon: \"$l_service_name\" is not enabled and not active on the system" fi l_service_name="chrony.service" # Check chrony service_not_enabled_chk if [ -n "$l_out2" ]; then l_chrony="y" l_out_chrony="$l_out2" else l_chrony="n" l_out_chrony="\n - Daemon: \"$l_service_name\" is not enabled and not active on the system" fi l_status="$l_timesyncd$l_chrony" case "$l_status" in yy) l_output2=" - More than one time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; nn) l_output2=" - No time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; yn|ny) l_output=" - Only one time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; *) l_output2=" - Unable to determine time sync daemon(s) status" ;; esac if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :\n$l_output2\n" fi } Page 325 Internal Only - General Note: Follow the guidance in the subsection for the time synchronization daemon available on the system and skip the other time synchronization daemon subsection. Remediation: On physical systems, and virtual systems where host based time synchronization is not available. Select one of the two time synchronization daemons; chrony (1) or systemd- timesyncd (2) and following the remediation procedure for the selected daemon. Note: enabling more than one synchronization daemon could lead to unexpected or unreliable results: 1. chrony Run the following command to install chrony: # apt install chrony Run the following commands to stop and mask the systemd-timesyncd daemon: # systemctl stop systemd-timesyncd.service # systemctl mask systemd-timesyncd.service Note: • Subsection: Configure chrony should be followed • Subsection: Configure systemd-timesyncd should be skipped 2. systemd-timesyncd Run the following command to remove the chrony package: # apt purge chrony # apt autoremove chrony Note: • Subsection: Configure systemd-timesyncd should be followed • Subsection: Configure chrony should be skipped References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. v7 6.1 Utilize Three Synchronized Time Sources ● ● Use at least three synchronized time sources from which all servers and Page 326 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version network devices retrieve time information on a regular basis so that timestamps in logs are consistent. Page 327 Internal Only - General 2.3.2 Configure systemd-timesyncd systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network. It implements an SNTP client. In contrast to NTP implementations such as chrony or the NTP reference server this only implements a client side, and does not bother with the full NTP complexity, focusing only on querying time from one remote server and synchronizing the local clock to it. The daemon runs with minimal privileges, and has been hooked up with networkd to only operate when network connectivity is available. The daemon saves the current clock to disk every time a new NTP sync has been acquired, and uses this to possibly correct the system clock early at bootup, in order to accommodate for systems that lack an RTC such as the Raspberry Pi and embedded devices, and make sure that time monotonically progresses on these systems, even if it is not always correct. To make use of this daemon a new system user and group "systemd-timesync" needs to be created on installation of systemd. The default configuration is set during compilation, so configuration is only needed when it is necessary to deviate from those defaults. Initially, the main configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. Local overrides can be created by editing this file or by creating drop-ins, as described below. Using drop-ins for local configuration is recommended over modifications to the main configuration file. In addition to the "main" configuration file, drop-in configuration snippets are read from /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. When packages need to customize the configuration, they can install drop-ins under /usr/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to be used to override package drop-ins, since the main configuration file has lower precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the files. To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file. Note: • The recommendations in this section only apply if timesyncd is in use on the system • The systemd-timesyncd service specifically implements only SNTP. o This minimalistic service will set the system clock for large offsets or slowly adjust it for smaller deltas o More complex use cases are not covered by systemd-timesyncd Page 328 Internal Only - General • If chrony is used, systemd-timesyncd should be stopped and masked, and this section skipped • One, and only one, time synchronization method should be in use on the system Page 329 Internal Only - General 2.3.2.1 Ensure systemd-timesyncd configured with authorized timeserver (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: NTP= • A space-separated list of NTP server host names or IP addresses. During runtime this list is combined with any per-interface NTP servers acquired from systemd-networkd.service(8). systemd-timesyncd will contact all configured system or per-interface servers in turn, until one responds. When the empty string is assigned, the list of NTP servers is reset, and all prior assignments will have no effect. This setting defaults to an empty list. FallbackNTP= • A space-separated list of NTP server host names or IP addresses to be used as the fallback NTP servers. Any per-interface NTP servers obtained from systemd- networkd.service(8) take precedence over this setting, as do any servers set via NTP= above. This setting is hence only relevant if no other NTP server information is known. When the empty string is assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this option is not given, a compiled-in list of NTP servers is used. Rationale: Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: Run the following command to verify the NTP and/or FallbackNTP option is set to local site approved authoritative time server(s): Page 330 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_output3=() a_out=() a_out2=() a_parlist=("NTP=[^#\n\r]+" "FallbackNTP=[^#\n\r]+") l_analyze_cmd="$(readlink -f /bin/systemd-analyze)" l_systemd_config_file="/etc/systemd/timesyncd.conf" f_config_file_parameter_chk() { l_used_parameter_setting="" while IFS= read -r l_file; do l_file="$(tr -d '# ' <<< "$l_file")" l_used_parameter_setting="$(grep -PHs -- '^\h*'"$l_parameter_name"'\b' "$l_file" | tail -n 1)" [ -n "$l_used_parameter_setting" ] && break done < <($l_analyze_cmd cat-config "$l_systemd_config_file" | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ -n "$l_used_parameter_setting" ]; then while IFS=: read -r l_file_name l_file_parameter; do while IFS="=" read -r l_file_parameter_name l_file_parameter_value; do if grep -Pq -- "$l_parameter_value" <<< "$l_file_parameter_value"; then a_out+=(" - Parameter: \"${l_file_parameter_name// /}\"" \ " correctly set to: \"${l_file_parameter_value// /}\"" \ " in the file: \"$l_file_name\"") else a_out2+=(" - Parameter: \"${l_file_parameter_name// /}\"" \ " incorrectly set to: \"${l_file_parameter_value// /}\"" \ " in the file: \"$l_file_name\"" \ " Should be set to: \"$l_value_out\"") fi done <<< "$l_file_parameter" done <<< "$l_used_parameter_setting" else a_out2+=(" - Parameter: \"$l_parameter_name\" is not set in an included file" \ " *** Note: \"$l_parameter_name\" May be set in a file that's ignored by load procedure ***") fi } while IFS="=" read -r l_parameter_name l_parameter_value; do # Assess and check parameters l_parameter_name="${l_parameter_name// /}"; l_parameter_value="${l_parameter_value// /}" l_value_out="${l_parameter_value//-/ through }"; l_value_out="${l_value_out//|/ or }" l_value_out="$(tr -d '(){}' <<< "$l_value_out")" f_config_file_parameter_chk done < <(printf '%s\n' "${a_parlist[@]}") if [ "${#a_out[@]}" -gt 0 ]; then a_output+=("${a_out[@]}"); [ "${#a_out2[@]}" -gt 0 ] && a_output3+=(" ** INFO: **" "${a_out2[@]}") else a_output2+=("${a_out2[@]}") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "${a_output3[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } Note: Please ensure the output for NTP and/or FallbackNTP is in accordance with local site policy. The timeservers in the example output are provided as an example of possible timeservers and they may not follow local site policy. Page 331 Internal Only - General Remediation: Set NTP and/or FallbackNTP parameters to local site approved authoritative time server(s) in /etc/systemd/timesyncd.conf or a file in /etc/systemd/timesyncd.conf.d/ ending in .conf in the [Time] section: Example file: [Time] NTP=time.nist.gov # Uses the generic name for NIST's time servers FallbackNTP=time-a-g.nist.gov time-b-g.nist.gov time-c-g.nist.gov # Space separated list of NIST time servers Example script to create systemd drop-in configuration file: #!/usr/bin/env bash { a_settings=("NTP=time.nist.gov" "FallbackNTP=time-a-g.nist.gov time-b- g.nist.gov time-c-g.nist.gov") [ ! -d /etc/systemd/timesyncd.conf.d/ ] && mkdir /etc/systemd/timesyncd.conf.d/ if grep -Psq -- '^\h*\[Time\]' /etc/systemd/timesyncd.conf.d/60- timesyncd.conf; then printf '%s\n' "" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf else printf '%s\n' "" "[Time]" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf fi } Note: If this setting appears in a canonically later file, or later in the same file, the setting will be overwritten Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-timesyncd Default Value: #NTP= #FallbackNTP= References: 1. https://www.freedesktop.org/software/systemd/man/timesyncd.conf.html 2. https://tf.nist.gov/tf-cgi/servers.cgi 3. NIST SP 800-53 Rev. 5: AU-7, AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. Page 332 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 333 Internal Only - General 2.3.2.2 Ensure systemd-timesyncd is enabled and running (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network Rationale: systemd-timesyncd needs to be enabled and running in order to synchronize the system to a timeserver. Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: - IF - systemd-timesyncd is in use on the system, run the following commands: Run the following command to verify that the systemd-timesyncd service is enabled: # systemctl is-enabled systemd-timesyncd.service enabled Run the following command to verify that the systemd-timesyncd service is active: # systemctl is-active systemd-timesyncd.service active Page 334 Internal Only - General Remediation: - IF - systemd-timesyncd is in use on the system, run the following commands: Run the following command to unmask systemd-timesyncd.service: # systemctl unmask systemd-timesyncd.service Run the following command to enable and start systemd-timesyncd.service: # systemctl --now enable systemd-timesyncd.service - OR - If another time synchronization service is in use on the system, run the following command to stop and mask systemd-timesyncd: # systemctl --now mask systemd-timesyncd.service References: 1. NIST SP 800-53 Rev. 5: AU-7, AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 335 Internal Only - General 2.3.3 Configure chrony chrony is a daemon which implements the Network Time Protocol (NTP) and is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. chrony can be configured to be a client and/or a server. More information on chrony can be found at: http://chrony.tuxfamily.org/. Note: • If systemd-timesyncd is being used, chrony should be removed and this section skipped • Only one time synchronization method should be in use on the system Page 336 Internal Only - General 2.3.3.1 Ensure chrony is configured with authorized timeserver (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: • server o The server directive specifies an NTP server which can be used as a time source. The client-server relationship is strictly hierarchical: a client might synchronize its system time to that of the server, but the server’s system time will never be influenced by that of a client. o This directive can be used multiple times to specify multiple servers. o The directive is immediately followed by either the name of the server, or its IP address. • pool o The syntax of this directive is similar to that for the server directive, except that it is used to specify a pool of NTP servers rather than a single NTP server. The pool name is expected to resolve to multiple addresses which might change over time. o This directive can be used multiple times to specify multiple pools. o All options valid in the server directive can be used in this directive too. Rationale: Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: - IF - chrony is in use on the system, run the following script to ensure chrony is configured with an authorized timeserver: Page 337 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_config_files=("/etc/chrony/chrony.conf") l_include='(confdir|sourcedir)' l_parameter_name='(server|pool)' l_parameter_value='.+' while IFS= read -r l_conf_loc; do l_dir="" l_ext="" if [ -d "$l_conf_loc" ]; then l_dir="$l_conf_loc" l_ext="*" elif grep -Psq '\/\*\.([^#/\n\r]+)?\h*$' <<< "$l_conf_loc" || [ -f "$(readlink -f "$l_conf_loc")" ]; then l_dir="$(dirname "$l_conf_loc")" l_ext="$(basename "$l_conf_loc")" fi if [[ -n "$l_dir" && -n "$l_ext" ]]; then while IFS= read -r -d $'\0' l_file_name; do [ -f "$(readlink -f "$l_file_name")" ] && a_config_files+=("$(readlink -f "$l_file_name")") done < <(find -L "$l_dir" -type f -name "$l_ext" -print0 2>/dev/null) fi done < <(awk '$1~/^\s*'"$l_include"'$/{print $2}' "${a_config_files[*]}" 2>/dev/null) for l_file in "${a_config_files[@]}"; do l_parameter_line="$(grep -Psi '^\h*'"$l_parameter_name"'(\h+|\h*:\h*)'"$l_parameter_value"'\b' "$l_file")" [ -n "$l_parameter_line" ] && a_output+=(" - Parameter: \"$(tr -d '()' <<< ${l_parameter_name//|/ or })\"" \ " Exists in the file: \"$l_file\" as:" "$l_parameter_line") done [ "${#a_output[@]}" -le "0" ] && a_output2+=(" - Parameter: \"$(tr -d '()' <<< ${l_parameter_name//|/ or })\"" \ " Does not exist in the chrony configuration") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" fi } Page 338 Internal Only - General Remediation: Edit /etc/chrony/chrony.conf or a file ending in .sources in /etc/chrony/sources.d/ and add or edit server or pool lines as appropriate according to local site policy: Edit the Chrony configuration and add or edit the server and/or pool lines returned by the Audit Procedure as appropriate according to local site policy <[server|pool]> <[remote-server|remote-pool]> Example script to add a drop-in configuration for the pool directive: #!/usr/bin/env bash { [ ! -d "/etc/chrony/sources.d/" ] && mkdir /etc/chrony/sources.d/ printf '%s\n' "" "#The maxsources option is unique to the pool directive" \ "pool time.nist.gov iburst maxsources 4" >> /etc/chrony/sources.d/60- sources.sources chronyc reload sources &>/dev/null } Example script to add a drop-in configuration for the server directive: #!/usr/bin/env bash { [ ! -d "/etc/chrony/sources.d/" ] && mkdir /etc/chrony/sources.d/ printf '%s\n' "" "server time-a-g.nist.gov iburst" "server 132.163.97.3 iburst" \ "server time-d-b.nist.gov iburst" >> /etc/chrony/sources.d/60- sources.sources chronyc reload sources &>/dev/null } Run the following command to reload the chronyd config: # systemctl reload-or-restart chronyd References: 1. chrony.conf(5) Manual Page 2. https://tf.nist.gov/tf-cgi/servers.cgi 3. NIST SP 800-53 Rev. 5: AU-3, AU-12 Page 339 Internal Only - General Additional Information: If pool and/or server directive(s) are set in a sources file in /etc/chrony/sources.d, the line: sourcedir /etc/chrony/sources.d must be present in /etc/chrony/chrony.conf CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 340 Internal Only - General 2.3.3.2 Ensure chrony is running as user _chrony (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The chrony package is installed with a dedicated user account _chrony. This account is granted the access required by the chronyd service Rationale: The chronyd service should run with only the required privlidges Audit: - IF - chrony is in use on the system, run the following command to verify the chronyd service is being run as the _chrony user: # ps -ef | awk '(/[c]hronyd/ && $1!="_chrony") { print $1 }' Nothing should be returned Remediation: Add or edit the user line to /etc/chrony/chrony.conf or a file ending in .conf in /etc/chrony/conf.d/: user _chrony - OR - If another time synchronization service is in use on the system, run the following command to remove chrony from the system: # apt purge chrony # apt autoremove chrony Default Value: user _chrony References: 1. NIST SP 800-53 Rev. 5: AU-8 Page 341 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 342 Internal Only - General 2.3.3.3 Ensure chrony is enabled and running (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: chrony is a daemon for synchronizing the system clock across the network Rationale: chrony needs to be enabled and running in order to synchronize the system to a timeserver. Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: - IF - chrony is in use on the system, run the following commands: Run the following command to verify that the chrony service is enabled: # systemctl is-enabled chrony.service enabled Run the following command to verify that the chrony service is active: # systemctl is-active chrony.service active Page 343 Internal Only - General Remediation: - IF - chrony is in use on the system, run the following commands: Run the following command to unmask chrony.service: # systemctl unmask chrony.service Run the following command to enable and start chrony.service: # systemctl --now enable chrony.service - OR - If another time synchronization service is in use on the system, run the following command to remove chrony: # apt purge chrony # apt autoremove chrony References: 1. NIST SP 800-53 Rev. 5: AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 344 Internal Only - General 2.4 Job Schedulers A job scheduler is used to execute jobs, commands, or shell scripts, at fixed times, dates, or intervals Page 345 Internal Only - General 2.4.1 Configure cron cron is a time based job scheduler - IF - cron is not installed on the system, this sub section can be skipped Note: Other methods such as systemd timers exist for scheduling jobs. If an alternate method is in use, it should be secured in accordance with local site policy Page 346 Internal Only - General 2.4.1.1 Ensure cron daemon is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The cron daemon is used to execute batch jobs on the system. Rationale: While there may not be user jobs that need to be run on the system, the system does have maintenance jobs that may include security monitoring that have to run, and cron is used to execute them. Audit: - IF - cron is installed on the system: Run the following command to verify cron is enabled: # systemctl list-unit-files | awk '$1~/^crond?\.service/{print $2}' enabled Run the following command to verify that cron is active: # systemctl list-units | awk '$1~/^crond?\.service/{print $3}' active Remediation: - IF - cron is installed on the system: Run the following commands to unmask, enable, and start cron: # systemctl unmask "$(systemctl list-unit-files | awk '$1~/^crond?\.service/{print $1}')" # systemctl --now enable "$(systemctl list-unit-files | awk '$1~/^crond?\.service/{print $1}')" References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 347 Internal Only - General 2.4.1.2 Ensure access to /etc/crontab is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/crontab file is used by cron to control its own jobs. The commands in this item make sure that root is the user and group owner of the file and that only the owner can access the file. Rationale: This file contains information on what system jobs are run by cron. Write access to these files could provide unprivileged users with the ability to elevate their privileges. Read access to these files could provide users with the ability to gain insight on system jobs that run on the system and could provide them a way to gain unauthorized privileged access. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other : # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/crontab Access: (600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on /etc/crontab: # chown root:root /etc/crontab # chmod og-rwx /etc/crontab Default Value: Access: (644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 348 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 349 Internal Only - General 2.4.1.3 Ensure access to /etc/cron.hourly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: This directory contains system cron jobs that need to run on an hourly basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.hourly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.hourly directory: # chown root:root /etc/cron.hourly/ # chmod og-rwx /etc/cron.hourly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 350 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 351 Internal Only - General 2.4.1.4 Ensure access to /etc/cron.daily is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.daily directory contains system cron jobs that need to run on a daily basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.daily/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.daily directory: # chown root:root /etc/cron.daily/ # chmod og-rwx /etc/cron.daily/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 352 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 353 Internal Only - General 2.4.1.5 Ensure access to /etc/cron.weekly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.weekly directory contains system cron jobs that need to run on a weekly basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.weekly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.weekly directory: # chown root:root /etc/cron.weekly/ # chmod og-rwx /etc/cron.weekly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 354 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 355 Internal Only - General 2.4.1.6 Ensure access to /etc/cron.monthly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.monthly directory contains system cron jobs that need to run on a monthly basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.monthly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.monthly directory: # chown root:root /etc/cron.monthly/ # chmod og-rwx /etc/cron.monthly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 356 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 357 Internal Only - General 2.4.1.7 Ensure access to /etc/cron.yearly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.yearly directory contains system cron jobs that need to run on an annual basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.yearly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.yearly directory: # chown root:root /etc/cron.yearly/ # chmod og-rwx /etc/cron.yearly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 358 Internal Only - General 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.d directory contains system cron jobs that need to run in a similar manner to the hourly, daily weekly and monthly jobs from /etc/crontab, but require more granular control as to when they run. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.d/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.d directory: # chown root:root /etc/cron.d/ # chmod og-rwx /etc/cron.d/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 359 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 360 Internal Only - General 2.4.1.9 Ensure access to crontab is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: crontab is the program used to install, deinstall, or list the tables used to drive the cron daemon. Each user can have their own crontab, and though files are created, they are not intended to be edited directly. If the /etc/cron.allow file exists, then you must be listed (one user per line) therein in order to be allowed to use this command. If the /etc/cron.allow file does not exist but the /etc/cron.deny file does exist, then you must not be listed in the /etc/cron.deny file in order to use this command. If neither of these files exists, then depending on site-dependent configuration parameters, only the super user will be allowed to use this command, or all users will be able to use this command. If both files exist then /etc/cron.allow takes precedence. Which means that /etc/cron.deny is not considered and your user must be listed in /etc/cron.allow in order to be able to use the crontab. Regardless of the existence of any of these files, the root administrative user is always allowed to setup a crontab. The files /etc/cron.allow and /etc/cron.deny, if they exist, must be either world- readable, or readable by group crontab. If they are not, then cron will deny access to all users until the permissions are fixed. There is one file for each user's crontab. Users are not allowed to edit the file directly to ensure that only users allowed by the system to run periodic tasks can add them, and only syntactically correct crontabs will be written. This is enforced by having the directory writable only by the crontab group and configuring crontab command with the setgid bid set for that specific group. Note: • The files /etc/cron.allow and /etc/cron.deny, if they exist, only controls administrative access to the crontab command for scheduling and modifying cron jobs • If you are using SELinux or AppArmor, these security modules may prevent crontab access. Check the audit logs for any related permission denied entries and adjust your policies if necessary. Rationale: On many systems, only the system administrator is authorized to schedule cron jobs. Using the cron.allow file to control who can run cron jobs enforces this policy. It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user ID to the system and forget to add it to the deny files. Page 361 Internal Only - General Impact: When the /etc/cron.allow file exists, a user must be listed, one user per line, in the /etc/cron.allow file in order to be allowed to use the crontab command. Audit: - IF - cron is installed on the system: Run the following command to verify /etc/cron.allow: • Exists • Is mode 0640 or more restrictive • Is owned by the user root • Is group owned by the group root - OR - the group crontab # stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/cron.allow Verify the returned value is: Access: (640/-rw-r-----) Owner: (root) Group: (root) - OR - Access: (640/-rw-r-----) Owner: (root) Group: (crontab) Run the following command to verify either cron.deny doesn't exist or is: • Mode 0640 or more restrictive • Owned by the user root • Is group owned by the group root - OR - the group crontab # [ -e "/etc/cron.deny" ] && stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/cron.deny Verify either nothing is returned - OR - returned value is one of the following: Access: (640/-rw-r-----) Owner: (root) Group: (root) - OR - Access: (640/-rw-r-----) Owner: (root) Group: (crontab) Note: On systems where cron is configured to use the group crontab, if the group crontab is not set as the owner of cron.allow, then cron will deny access to all users and you will see an error similar to: You () are not allowed to use this program (crontab) See crontab(1) for more information Page 362 Internal Only - General Remediation: - IF - cron is installed on the system: Run the following script to: • Create /etc/cron.allow if it doesn't exist • Change owner to user root • Change group owner to group root - OR - group crontab if it exists • Change mode to 640 or more restrictive #!/usr/bin/env bash { [ ! -e "/etc/cron.allow" ] && touch /etc/cron.allow chmod u-x,g-wx,o-rwx /etc/cron.allow if grep -Pq -- '^\h*crontab\:' /etc/group; then chown root:crontab /etc/cron.allow else chown root:root /etc/cron.allow fi } - IF - /etc/cron.deny exists, run the following script to: • Change owner to user root • Change group owner to group root - OR - group crontab if it exists • Change mode to 640 or more restrictive #!/usr/bin/env bash { if [ -e "/etc/cron.deny" ]; then chmod u-x,g-wx,o-rwx /etc/cron.deny if grep -Pq -- '^\h*crontab\:' /etc/group; then chown root:crontab /etc/cron.deny else chown root:root /etc/cron.deny fi fi } Page 363 Internal Only - General Note: • When the /etc/cron.allow file exists, a user must be listed, one user per line, in the /etc/cron.allow file in order to be allowed to use the crontab command. • If both /etc/cron.allow and /etc/cron.deny exist, /etc/cron.allow takes precedence. Which means that /etc/cron.deny is not considered and users must be listed in /etc/cron.allow in order to use the crontab. • If the /etc/cron.allow file does not exist but the /etc/cron.deny file does exist, then you must not be listed in the /etc/cron.deny file in order to use the crontab command. • Regardless of the existence of any of these files, the root administrative user is always allowed to setup a crontab. • On systems where cron is configured to use the group crontab, if the group crontab is not set as the owner of /etc/cron.allow, then cron will deny access to all users but root, and you will see an error similar to: You () are not allowed to use this program (crontab) See crontab(1) for more information References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 364 Internal Only - General 2.4.2 Configure at at is a command-line utility used to schedule a job for later execution Note: if at is not installed on the system, this section can be skipped Page 365 Internal Only - General 2.4.2.1 Ensure access to at is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: at allows fairly complex time specifications, extending the POSIX.2 standard. It accepts times of the form HH:MM to run a job at a specific time of day. (If that time is already past, the next day is assumed.) You may also specify midnight, noon, or teatime (4pm) and you can have a time-of-day suffixed with AM or PM for running in the morning or the evening. You can also say what day the job will be run, by giving a date in the form month-name day with an optional year, or giving a date of the form MMDD[CC]YY, MM/DD/[CC]YY, DD.MM.[CC]YY or [CC]YY-MM-DD. The specification of a date must follow the specification of the time of day. You can also give times like now + count time-units, where the time-units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the time with today and to run the job tomorrow by suffixing the time with tomorrow. The /etc/at.allow and /etc/at.deny files determine which user can submit commands for later execution via at or batch. The format of the files is a list of usernames, one on each line. Whitespace is not permitted. If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at. If /etc/at.allow does not exist, /etc/at.deny is checked, every username not mentioned in it is then allowed to use at. An empty /etc/at.deny means that every user may use at. If neither file exists, only the superuser is allowed to use at. Rationale: On many systems, only the system administrator is authorized to schedule at jobs. Using the at.allow file to control who can run at jobs enforces this policy. It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user ID to the system and forget to add it to the deny files. Page 366 Internal Only - General Audit: - IF - at is installed on the system: Run the following command to verify /etc/at.allow: • Exists • Is mode 0640 or more restrictive • Is owned by the user root • Is group owned by the group daemon or group root # stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/at.allow Access: (640/-rw-r-----) Owner: (root) Group: (daemon) -OR- Access: (640/-rw-r-----) Owner: (root) Group: (root) Verify mode is 640 or more restrictive, owner is root, and group is daemon or root Run the following command to verify at.deny doesn't exist, -OR- is: • Mode 0640 or more restrictive • Owned by the user root • Group owned by the group daemon or group root # [ -e "/etc/at.deny" ] && stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/at.deny Access: (640/-rw-r-----) Owner: (root) Group: (daemon) -OR- Access: (640/-rw-r-----) Owner: (root) Group: (root) -OR- Nothing is returned If a value is returned, verify mode is 640 or more restrictive, owner is root, and group is daemon or root Page 367 Internal Only - General Remediation: - IF - at is installed on the system: Run the following script to: • /etc/at.allow: o Create the file if it doesn't exist o Change owner or user root o If group daemon exists, change to group daemon, else change group to root o Change mode to 640 or more restrictive • - IF - /etc/at.deny exists: o Change owner or user root o If group daemon exists, change to group daemon, else change group to root o Change mode to 640 or more restrictive #!/usr/bin/env bash { grep -Pq -- '^daemon\b' /etc/group && l_group="daemon" || l_group="root" [ ! -e "/etc/at.allow" ] && touch /etc/at.allow chown root:"$l_group" /etc/at.allow chmod u-x,g-wx,o-rwx /etc/at.allow [ -e "/etc/at.deny" ] && chown root:"$l_group" /etc/at.deny [ -e "/etc/at.deny" ] && chmod u-x,g-wx,o-rwx /etc/at.deny } References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 368 Internal Only - General 3 Network This section provides guidance on for securing the network configuration of the system Page 369 Internal Only - General 3.1 Configure Network Devices To reduce the attack surface of a system, unused devices should be disabled. Note: This should not be considered a comprehensive list, you may wish to consider additions to those listed here for your environment. Page 370 Internal Only - General 3.1.1 Ensure IPv6 status is identified (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Internet Protocol Version 6 (IPv6) is the most recent version of Internet Protocol (IP). It's designed to supply IP addressing and additional security to support the predicted growth of connected devices. IPv6 is based on 128-bit addressing and can support 340 undecillion, which is 340,282,366,920,938,463,463,374,607,431,768,211,456 unique addresses. Features of IPv6 • Hierarchical addressing and routing infrastructure • Statefull and Stateless configuration • Support for quality of service (QoS) • An ideal protocol for neighboring node interaction Rationale: IETF RFC 4038 recommends that applications are built with an assumption of dual stack. It is recommended that IPv6 be enabled and configured in accordance with Benchmark recommendations. - IF - dual stack and IPv6 are not used in your environment, IPv6 may be disabled to reduce the attack surface of the system, and recommendations pertaining to IPv6 can be skipped. Note: It is recommended that IPv6 be enabled and configured unless this is against local site policy Impact: IETF RFC 4038 recommends that applications are built with an assumption of dual stack. When enabled, IPv6 will require additional configuration to reduce risk to the system. Page 371 Internal Only - General Audit: Run the following script to identify if IPv6 is enabled on the system: #!/usr/bin/env bash { l_output="" ! grep -Pqs -- '^\h*0\b' /sys/module/ipv6/parameters/disable && l_output="- IPv6 is not enabled" if sysctl net.ipv6.conf.all.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\b" && \ sysctl net.ipv6.conf.default.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\b"; then l_output="- IPv6 is not enabled" fi [ -z "$l_output" ] && l_output="- IPv6 is enabled" echo -e "\n$l_output\n" } Remediation: Enable or disable IPv6 in accordance with system requirements and local site policy Default Value: IPv6 is enabled References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Having more addresses has grown in importance with the expansion of smart devices and connectivity. IPv6 provides more than enough globally unique IP addresses for every networked device currently on the planet, helping ensure providers can keep pace with the expected proliferation of IP-based devices. Page 372 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 373 Internal Only - General 3.1.2 Ensure wireless interfaces are not available (Automated) Profile Applicability: • Level 1 - Server Description: Wireless networking is used when wired networks are unavailable. Rationale: -IF- wireless is not to be used, wireless devices can be disabled to reduce the potential attack surface. Impact: Many if not all laptop workstations and some desktop workstations will connect via wireless requiring these interfaces be enabled. Audit: Run the following script to verify no wireless interfaces are active on the system: Page 374 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" module_chk() { # Check how module will be loaded l_loadable="$(modprobe -n -v "$l_mname")" if grep -Pq -- '^\h*install \/bin\/(true|false)' <<< "$l_loadable"; then l_output="$l_output\n - module: \"$l_mname\" is not loadable: \"$l_loadable\"" else l_output2="$l_output2\n - module: \"$l_mname\" is loadable: \"$l_loadable\"" fi # Check is the module currently loaded if ! lsmod | grep "$l_mname" > /dev/null 2>&1; then l_output="$l_output\n - module: \"$l_mname\" is not loaded" else l_output2="$l_output2\n - module: \"$l_mname\" is loaded" fi # Check if the module is deny listed if modprobe --showconfig | grep -Pq -- "^\h*blacklist\h+$l_mname\b"; then l_output="$l_output\n - module: \"$l_mname\" is deny listed in: \"$(grep -Pl -- "^\h*blacklist\h+$l_mname\b" /etc/modprobe.d/*)\"" else l_output2="$l_output2\n - module: \"$l_mname\" is not deny listed" fi } if [ -n "$(find /sys/class/net/*/ -type d -name wireless)" ]; then l_dname=$(for driverdir in $(find /sys/class/net/*/ -type d -name wireless | xargs -0 dirname); do basename "$(readlink -f "$driverdir"/device/driver/module)";done | sort -u) for l_mname in $l_dname; do module_chk done fi # Report results. If no failures output in l_output2, we pass if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **" if [ -z "$l_output" ]; then echo -e "\n - System has no wireless NICs installed" else echo -e "\n$l_output\n" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n" [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n" fi } Page 375 Internal Only - General Remediation: Run the following command to disable any wireless interfaces: # find /lib/modules/`uname -r`/kernel/drivers/net/wireless -name '*.ko' - printf 'install %f /bin/false\nblacklist %f\n\n' | sed 's/\.ko//1' >> /etc/modprobe.d/blacklist-wireless.conf Note: the *.conf file in /etc/modprobe.d/ in the above command can renamed as needed. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 15.4 Disable Wireless Access on Devices if Not Required v7 Disable wireless access on devices that do not have a business purpose for ● wireless access. 15.5 Limit Wireless Access on Client Devices v7 Configure wireless access on client machines that do have an essential wireless business purpose, to allow access only to authorized wireless networks ● and to restrict access to other wireless networks. Page 376 Internal Only - General 3.1.3 Ensure bluetooth services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: Bluetooth is a short-range wireless technology standard that is used for exchanging data between devices over short distances. It employs UHF radio waves in the ISM bands, from 2.402 GHz to 2.48 GHz. It is mainly used as an alternative to wire connections. Rationale: An attacker may be able to find a way to access or corrupt your data. One example of this type of activity is bluesnarfing, which refers to attackers using a Bluetooth connection to steal information off of your Bluetooth device. Also, viruses or other malicious code can take advantage of Bluetooth technology to infect other devices. If you are infected, your data may be corrupted, compromised, stolen, or lost. Impact: Many personal electronic devices (PEDs) use Bluetooth technology. For example, you may be able to operate your computer with a wireless keyboard. Disabling Bluetooth will prevent these devices from connecting to the system. There may be packages that are dependent on the bluez package. If the bluez package is removed, these dependent packages will be removed as well. Before removing the bluez package, review any dependent packages to determine if they are required on the system. -IF- a dependent package is required: stop and mask bluetooth.service leaving the bluez package installed. Page 377 Internal Only - General Audit: Run the following command to verify the bluez package is not installed: # dpkg-query -s bluez &>/dev/null && echo "bluez is installed" Nothing should be returned. - OR - - IF - the bluez package is required as a dependency: Run the following command to verify bluetooth.service is not enabled: # systemctl is-enabled bluetooth.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify bluetooth.service is not active: # systemctl is-active bluetooth.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop bluetooth.service, and remove the bluez package: # systemctl stop bluetooth.service # apt purge bluez - OR - - IF - the bluez package is required as a dependency: Run the following commands to stop and mask bluetooth.service: # systemctl stop bluetooth.service # systemctl mask bluetooth.service Note: A reboot may be required References: 1. https://www.cisa.gov/tips/st05-015 2. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Page 378 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 379 Internal Only - General 3.2 Configure Network Kernel Modules The Linux kernel modules support several network protocols that are not commonly used. If these protocols are not needed, it is recommended that they be disabled in the kernel. Note: This should not be considered a comprehensive list of uncommon network protocols, you may wish to consider additions to those listed here for your environment. Page 380 Internal Only - General 3.2.1 Ensure atm kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Asynchronous Transfer Mode (ATM) is a protocol operating on network, data link, and physical layers, based on virtual circuits and virtual paths. Disabling ATM protects the system against exploitation of any laws in its implementation. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the atm kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the atm kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="atm" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the atm kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the atm filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the atm kernel module is not loaded and not loadable by performing the following: Run the following command to verify the atm kernel module is not loaded: # lsmod | grep 'atm' Nothing should be returned Page 381 Internal Only - General Run the following command to verify the atm kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+atm\b' Verify the output includes: blacklist atm -AND- install atm /bin/false -OR- install atm /bin/true Example output: blacklist atm install atm /bin/false Remediation: Unload and disable the atm kernel module. 1. Run the following commands to unload the atm kernel module: # modprobe -r atm 2>/dev/null # rmmod can 2>/dev/null 2. Perform the following to disable the atm kernel module: Create a file ending in .conf with install can /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install atm /bin/false" >> /etc/modprobe.d/60-atm.conf Create a file ending in .conf with blacklist atm in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist atm" >> /etc/modprobe.d/60-atm.conf Page 382 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040021 | RULE ID: SV-230494r1069310 | CAT III 5. STIG ID: OL08-00-040021 | RULE ID: SV-248829r991589 | CAT II 6. STIG ID: RHEL-09-213045 | RULE ID: SV-257804r1044853 | CAT II 7. STIG ID: ALMA-09-029610 | RULE ID: SV-269341r1050223 | CAT II 8. STIG ID: OL09-00-000040 | RULE ID: SV-271443r1092463 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 383 Internal Only - General 3.2.2 Ensure can kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Controller Area Network (CAN) is a serial communications protocol, which was initially developed for automotive and is now also used in marine, industrial, and medical applications. Disabling CAN protects the system against exploitation of any flaws in its implementation. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the can kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the can kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="can" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the can kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the can filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the can kernel module is not loaded and not loadable by performing the following: Run the following command to verify the can kernel module is not loaded: Page 384 Internal Only - General # lsmod | grep 'can' Nothing should be returned Run the following command to verify the can kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+can\b' Verify the output includes: blacklist can -AND- install can /bin/false -OR- install can /bin/true Example output: blacklist can install can /bin/false Remediation: Unload and disable the can kernel module. 1. Run the following commands to unload the can kernel module: # modprobe -r can 2>/dev/null # rmmod can 2>/dev/null 2. Perform the following to disable the can kernel module: Create a file ending in .conf with install can /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install can /bin/false" >> /etc/modprobe.d/60-can.conf Create a file ending in .conf with blacklist can in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist can" >> /etc/modprobe.d/60-can.conf Page 385 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040022 | RULE ID: SV-230495r1069311 | CAT III 5. STIG ID: OL08-00-040022 | RULE ID: SV-248830r991589 | CAT II 6. STIG ID: RHEL-09-213050 | RULE ID: SV-257805r1044856 | CAT II 7. STIG ID: ALMA-09-029830 | RULE ID: SV-269343r1050225 | CAT II 8. STIG ID: OL09-00-000041 | RULE ID: SV-271444r1091044 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 386 Internal Only - General 3.2.3 Ensure dccp kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Datagram Congestion Control Protocol (DCCP) is a transport layer protocol that supports streaming media and telephony. DCCP provides a way to gain access to congestion control, without having to do it at the application layer, but does not provide in-sequence delivery. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the dccp kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the dccp kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="dccp" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the dccp kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the dccp filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the dccp kernel module is not loaded and not loadable by performing the following: Run the following command to verify the dccp kernel module is not loaded: Page 387 Internal Only - General # lsmod | grep 'dccp' Nothing should be returned Run the following command to verify the dccp kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+dccp\b' Verify the output includes: blacklist dccp -AND- install dccp /bin/false -OR- install dccp /bin/true Example output: blacklist dccp install dccp /bin/false Remediation: Unload and disable the dccp kernel module. 1. Run the following commands to unload the dccp kernel module: # modprobe -r dccp 2>/dev/null # rmmod dccp 2>/dev/null 2. Perform the following to disable the dccp kernel module: Create a file ending in .conf with install dccp /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install dccp /bin/false" >> /etc/modprobe.d/60-dccp.conf Create a file ending in .conf with blacklist dccp in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist dccp" >> /etc/modprobe.d/60-dccp.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. Page 388 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 389 Internal Only - General 3.2.4 Ensure rds kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Reliable Datagram Sockets (RDS) protocol is a transport layer protocol designed to provide low-latency, high-bandwidth communications between cluster nodes. It was developed by the Oracle Corporation. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the rds kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the rds kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="rds" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the rds kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the rds filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the rds kernel module is not loaded and not loadable by performing the following: Run the following command to verify the rds kernel module is not loaded: # lsmod | grep 'rds' Nothing should be returned Page 390 Internal Only - General Run the following command to verify the rds kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+rds\b' Verify the output includes: blacklist rds -AND- install rds /bin/false -OR- install rds /bin/true Example output: blacklist rds install rds /bin/false Remediation: Unload and disable the rds kernel module. 1. Run the following commands to unload the rds kernel module: # modprobe -r rds 2>/dev/null # rmmod rds 2>/dev/null 2. Perform the following to disable the rds kernel module: Create a file ending in .conf with install rds /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install rds /bin/false" >> /etc/modprobe.d/60-rds.conf Create a file ending in .conf with blacklist rds in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist rds" >> /etc/modprobe.d/60-rds.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Page 391 Internal Only - General Controls Control IG 1 IG 2 IG 3 Version Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 392 Internal Only - General 3.2.5 Ensure sctp kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Stream Control Transmission Protocol (SCTP) is a transport layer protocol used to support message oriented communication, with several streams of messages in one connection. It serves a similar function as TCP and UDP, incorporating features of both. It is message-oriented like UDP, and ensures reliable in-sequence transport of messages with congestion control like TCP. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the sctp kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the sctp kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="sctp" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the sctp kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the sctp filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the sctp kernel module is not loaded and not loadable by performing the following: Run the following command to verify the sctp kernel module is not loaded: Page 393 Internal Only - General # lsmod | grep 'sctp' Nothing should be returned Run the following command to verify the sctp kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+sctp\b' Verify the output includes: blacklist sctp -AND- install sctp /bin/false -OR- install sctp /bin/true Example output: blacklist sctp install sctp /bin/false Remediation: Unload and disable the sctp kernel module. 1. Run the following commands to unload the sctp kernel module: # modprobe -r sctp 2>/dev/null # rmmod sctp 2>/dev/null 2. Perform the following to disable the sctp kernel module: Create a file ending in .conf with install sctp /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install sctp /bin/false" >> /etc/modprobe.d/60-sctp.conf Create a file ending in .conf with blacklist sctp in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist sctp" >> /etc/modprobe.d/60-sctp.conf Page 394 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040023 | RULE ID: SV-230496r1069312 | CAT III 5. STIG ID: OL08-00-040023 | RULE ID: SV-248831r991589 | CAT II 6. STIG ID: RHEL-09-213060 | RULE ID: SV-257807r1044862 | CAT II 7. STIG ID: ALMA-09-030050 | RULE ID: SV-269345r1050227 | CAT II 8. STIG ID: OL09-00-000043 | RULE ID: SV-271446r1091050 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 395 Internal Only - General 3.2.6 Ensure tipc kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communication between cluster nodes. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the tipc kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the tipc kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="tipc" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the tipc kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the tipc filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the tipc kernel module is not loaded and not loadable by performing the following: Run the following command to verify the tipc kernel module is not loaded: # lsmod | grep 'tipc' Nothing should be returned Run the following command to verify the tipc kernel module is not loadable: Page 396 Internal Only - General # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+tipc\b' Verify the output includes: blacklist tipc -AND- install tipc /bin/false -OR- install tipc /bin/true Example output: blacklist tipc install tipc /bin/false Remediation: Unload and disable the tipc kernel module. 1. Run the following commands to unload the tipc kernel module: # modprobe -r tipc 2>/dev/null # rmmod tipc 2>/dev/null 2. Perform the following to disable the tipc kernel module: Create a file ending in .conf with install tipc /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install tipc /bin/false" >> /etc/modprobe.d/60-tipc.conf Create a file ending in .conf with blacklist tipc in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist tipc" >> /etc/modprobe.d/60-tipc.conf Page 397 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040024 | RULE ID: SV-230497r1069313 | CAT III 5. STIG ID: OL08-00-040024 | RULE ID: SV-248832r958478 | CAT III 6. STIG ID: RHEL-09-213065 | RULE ID: SV-257808r1044865 | CAT II 7. STIG ID: ALMA-09-030270 | RULE ID: SV-269347r1050229 | CAT II 8. STIG ID: OL09-00-000044 | RULE ID: SV-271447r1092464 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 398 Internal Only - General 3.3 Configure Network Kernel Parameters This section contains Recommendations covering kernel parameters effecting network stack. Note: • Some of the Recommendations in this section's subsections are not applicable if the system is a router. These Recommendations include a note in their description. • sysctl settings are defined through files in /usr/local/lib, /usr/lib/, /lib/, /run/, and /etc/ • Files are typically placed in the sysctl.d directory within the parent directory • The paths where sysctl preload files usually exist o /run/sysctl.d/*.conf o /etc/sysctl.d/*.conf o /usr/local/lib/sysctl.d/*.conf o /usr/lib/sysctl.d/*.conf o /lib/sysctl.d/*.conf o /etc/sysctl.conf • Files must have the ".conf" extension • Vendors settings usually live in /usr/lib/ or /usr/local/lib/ • To override a whole file, create a new file with the same name in /etc/sysctl.d/ and put new settings there. • To override only specific settings, add a file with a lexically later name in /etc/sysctl.d/ and put new settings there. • The command /usr/lib/systemd/systemd-sysctl --cat-config produces output containing The system's loaded kernel parameters and the files they're configured in: o Entries listed latter in the file take precedence over the same settings listed earlier in the file o Files containing kernel parameters that are over-ridden by other files with the same name will not be listed o On systems running UncomplicatedFirewall, the kernel parameters may be set or over-written. This will not be visible in the output of the command • On systems with Uncomplicated Firewall, additional settings may be configured in /etc/ufw/sysctl.conf o The settings in /etc/ufw/sysctl.conf will override settings other settings and will not be visible in the output of the /usr/lib/systemd/systemd-sysctl --cat-config command o This behavior can be changed by updating the IPT_SYSCTL parameter in /etc/default/ufw • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. Page 399 Internal Only - General /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 400 Internal Only - General 3.3.1 Configure IPv4 parameters net.ipv4 kernel parameters control various aspects of the IPv4 network stack. These parameters effect functions to include routing, TCP, and security. Page 401 Internal Only - General 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The net.ipv4.ip_forward flag tells the system whether it can forward IPv4 packets or not. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.conf.all.forwarding=0 and net.ipv4.conf.default.forwarding=0 are configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Setting net.ipv4.ip_forward to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will not be able to forward IPv4 packets. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Page 402 Internal Only - General Audit: Verify net.ipv4.ip_forward is set to 0. 1. Run the following command to verify net.ipv4.ip_forward is set to 0 in the running configuration: # sysctl net.ipv4.ip_forward Verify output is: net.ipv4.ip_forward = 0 2. Run the following script to verify net.ipv4.ip_forward = 0 is set in a file being used by systemd sysctl to configure net.ipv4.ip_forward: #!/usr/bin/env bash { l_parameter_name="net.ipv4.ip_forward" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.ip_forward = 0. Example output: - "net.ipv4.ip_forward = 0" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Page 403 Internal Only - General Note: If multiple lines with net.ipv4.ip_forward = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.ip_forward lines that are not net.ipv4.ip_forward=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.ip_forward" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.ip_forward = 0 Page 404 Internal Only - General Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.ip_forward = 0" >> /etc/sysctl.d/60- ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.ip_forward = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: SLES-15-040380 | RULE ID: SV-235024r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 405 Internal Only - General 3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.all.forwarding controls forwarding of IPv4 packet on all interfaces. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.ip_forward=0 is configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Cloud Service Provider (CSP) hosted systems may require forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IPv4 forwarding. Page 406 Internal Only - General Audit: Verify net.ipv4.conf.all.forwarding is set to 0. 1. Run the following command to verify net.ipv4.conf.all.forwarding is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.forwarding Verify output is: net.ipv4.conf.all.forwarding = 0 2. Run the following script to verify net.ipv4.conf.all.forwarding = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.forwarding: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.forwarding = 0. Example output: - "net.ipv4.conf.all.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 407 Internal Only - General Note: • If multiple lines with net.ipv4.conf.all.forwarding = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. • This script looks at all files used by systemd sysctl. • More information about these files, their location, and load preference is available in the section overview. Page 408 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.forwarding lines that are not net.ipv4.conf.all.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.forwarding = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 409 Internal Only - General Default Value: net.ipv4.conf.all.forwarding = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040259 | RULE ID: SV-250317r1017358 | CAT II 5. STIG ID: OL08-00-040259 | RULE ID: SV-252662r991589 | CAT II 6. STIG ID: RHEL-09-253075 | RULE ID: SV-257970r1045011 | CAT II 7. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 8. STIG ID: OL09-00-006028 | RULE ID: SV-271872r1092328 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 410 Internal Only - General 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.default.forwarding controls forwarding of IPv4 packet on newly added network interfaces. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.ip_forward=0 is configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Cloud Service Provider (CSP) hosted systems may require forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IPv4 forwarding. Page 411 Internal Only - General Audit: Verify net.ipv4.conf.default.forwarding is set to 0. 1. Run the following command to verify net.ipv4.conf.default.forwarding is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.forwarding Verify output is: net.ipv4.conf.default.forwarding = 0 2. Run the following script to verify net.ipv4.conf.default.forwarding = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.forwarding: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.forwarding = 0. Example output: - "net.ipv4.conf.default.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 412 Internal Only - General Note: If multiple lines with net.ipv4.conf.default.forwarding = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.forwarding lines that are not net.ipv4.conf.default.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.forwarding = 0 Example: Page 413 Internal Only - General # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.forwarding = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.default.forwarding = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 414 Internal Only - General 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.all.send_redirects controls sending of all IPv4 ICMP redirected packets on all interfaces. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If this system is a router this recommendation is not applicable. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Audit: Verify net.ipv4.conf.all.send_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.send_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.send_redirects Verify output is: net.ipv4.conf.all.send_redirects = 0 2. Run the following script to verify net.ipv4.ip_forward = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.send_redirects: Page 415 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.send_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.send_redirects = 0. Example output: - "net.ipv4.conf.all.send_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.all.send_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.send_redirects lines that are not net.ipv4.conf.all.send_redirects=0. Example script: Page 416 Internal Only - General #!/usr/bin/env bash { l_option="net.ipv4.conf.all.send_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.send_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.send_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 417 Internal Only - General Default Value: net.ipv4.conf.all.send_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040220 | RULE ID: SV-230536r1017298 | CAT II 5. STIG ID: OL08-00-040220 | RULE ID: SV-248877r991589 | CAT II 6. STIG ID: RHEL-09-253065 | RULE ID: SV-257968r991589 | CAT II 7. STIG ID: ALMA-09-019930 | RULE ID: SV-269256r1050138 | CAT II 8. STIG ID: OL09-00-006032 | RULE ID: SV-271875r1092337 | CAT II 9. STIG ID: SLES-15-040370 | RULE ID: SV-235023r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 418 Internal Only - General 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.default.send_redirects controls sending of all IPv4 ICMP redirected packets on a newly added network interface. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If this system is a router this recommendation is not applicable. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Audit: Verify net.ipv4.conf.default.send_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.send_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.send_redirects Verify output is: net.ipv4.conf.default.send_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.send_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.send_redirects: Page 419 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.send_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.send_redirects = 0. Example output: - "net.ipv4.conf.default.send_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.default.send_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.send_redirects lines that are not net.ipv4.conf.default.send_redirects=0. Example script: Page 420 Internal Only - General #!/usr/bin/env bash { l_option="net.ipv4.conf.default.send_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.send_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.send_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 421 Internal Only - General Default Value: net.ipv4.conf.default.send_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040270 | RULE ID: SV-230543r1017305 | CAT II 5. STIG ID: OL08-00-040270 | RULE ID: SV-248886r991589 | CAT II 6. STIG ID: RHEL-09-253070 | RULE ID: SV-257969r991589 | CAT II 7. STIG ID: ALMA-09-019930 | RULE ID: SV-269256r1050138 | CAT II 8. STIG ID: OL09-00-006033 | RULE ID: SV-271876r1092641 | CAT II 9. STIG ID: SLES-15-040360 | RULE ID: SV-235022r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 422 Internal Only - General 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.icmp_ignore_bogus_error_responses controls if the kernel logs bogus responses (RFC-1122 non-compliant) from broadcast reframes. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Some routers (and some attackers) will send responses that violate RFC-1122 and attempt to fill up a log file system with many useless error messages. Audit: Verify net.ipv4.icmp_ignore_bogus_error_responses is set to 1. 1. Run the following command to verify net.ipv4.icmp_ignore_bogus_error_responses is set to 1 in the running configuration: # sysctl net.ipv4.icmp_ignore_bogus_error_responses Verify output is: net.ipv4.icmp_ignore_bogus_error_responses = 1 2. Run the following script to verify net.ipv4.icmp_ignore_bogus_error_responses = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.icmp_ignore_bogus_error_responses: Page 423 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.icmp_ignore_bogus_error_responses" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.icmp_ignore_bogus_error_responses = 1. Example output: - "net.ipv4.icmp_ignore_bogus_error_responses = 1" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.icmp_ignore_bogus_error_responses = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.icmp_ignore_bogus_error_responses lines that are not net.ipv4.icmp_ignore_bogus_error_responses=1. Example script: Page 424 Internal Only - General #!/usr/bin/env bash { l_option="net.ipv4.icmp_ignore_bogus_error_responses" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.icmp_ignore_bogus_error_responses = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.icmp_ignore_bogus_error_responses = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 425 Internal Only - General Default Value: net.ipv4.icmp_ignore_bogus_error_responses = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253060 | RULE ID: SV-257967r991589 | CAT II 5. STIG ID: ALMA-09-018940 | RULE ID: SV-269247r1050129 | CAT II 6. STIG ID: OL09-00-006031 | RULE ID: SV-271874r1092612 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 426 Internal Only - General 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.icmp_echo_ignore_broadcasts controls if all ICMP echo and timestamp requests to broadcast and multicast addresses are ignored. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Accepting ICMP echo and timestamp requests with broadcast or multicast destinations for your network could be used to trick your host into starting (or participating) in a Smurf attack. A Smurf attack relies on an attacker sending large amounts of ICMP broadcast messages with a spoofed source address. All hosts receiving this message and responding would send echo-reply messages back to the spoofed address, which is probably not routable. If many hosts respond to the packets, the amount of traffic on the network could be significantly multiplied. Audit: Verify net.ipv4.icmp_echo_ignore_broadcasts is set to 1. 1. Run the following command to verify net.ipv4.icmp_echo_ignore_broadcasts is set to 1 in the running configuration: # sysctl net.ipv4.icmp_echo_ignore_broadcasts Verify output is: net.ipv4.icmp_echo_ignore_broadcasts = 1 2. Run the following script to verify net.ipv4.icmp_echo_ignore_broadcasts = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.icmp_echo_ignore_broadcasts: Page 427 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.icmp_echo_ignore_broadcasts" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.icmp_echo_ignore_broadcasts = 1. Example output: - "net.ipv4.icmp_echo_ignore_broadcasts = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.icmp_echo_ignore_broadcasts = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.icmp_echo_ignore_broadcasts lines that are not net.ipv4.icmp_echo_ignore_broadcasts=1. Example script: Page 428 Internal Only - General #!/usr/bin/env bash { l_option="net.ipv4.icmp_echo_ignore_broadcasts" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.icmp_echo_ignore_broadcasts = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.icmp_echo_ignore_broadcasts = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 429 Internal Only - General Default Value: net.ipv4.icmp_echo_ignore_broadcasts = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040230 | RULE ID: SV-230537r1017299 | CAT II 5. STIG ID: OL08-00-040230 | RULE ID: SV-248878r991589 | CAT II 6. STIG ID: RHEL-09-253055 | RULE ID: SV-257966r991589 | CAT II 7. STIG ID: ALMA-09-019050 | RULE ID: SV-269248r1050130 | CAT II 8. STIG ID: OL09-00-006030 | RULE ID: SV-271873r1092331 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 430 Internal Only - General 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv4.conf.all.accept_redirects controls accepting of all IPv4 ICMP redirected packets on all interfaces. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will not accept any IPv4 ICMP redirect messages, and therefore, won't allow outsiders to update the system's routing tables. Audit: Verify net.ipv4.conf.all.accept_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.accept_redirects Verify output is: net.ipv4.conf.all.accept_redirects = 0 2. Run the following script to verify net.ipv4.conf.all.send_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.send_redirects: Page 431 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.accept_redirects = 0. Example output: - "net.ipv4.conf.all.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.all.accept_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 432 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.accept_redirects lines that are not net.ipv4.conf.all.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 433 Internal Only - General Default Value: net.ipv4.conf.all.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040279 | RULE ID: SV-244553r1017353 | CAT II 5. STIG ID: OL08-00-040279 | RULE ID: SV-248887r991589 | CAT II 6. STIG ID: RHEL-09-253015 | RULE ID: SV-257958r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006020 | RULE ID: SV-271864r1092304 | CAT II 9. STIG ID: SLES-15-040330 | RULE ID: SV-235018r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 434 Internal Only - General 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv4.conf.default.accept_redirects controls accepting of all IPv4 ICMP redirected packets on a newly added network interface. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If this system is a router this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will not accept IPv4 ICMP redirect messages on a newly added network interface. Audit: Verify net.ipv4.conf.default.accept_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.accept_redirects Verify output is: net.ipv4.conf.default.accept_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.accept_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.accept_redirects: Page 435 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.accept_redirects = 0. Example output: - "net.ipv4.conf.default.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.default.accept_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 436 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.accept_redirects lines that are not net.ipv4.conf.default.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 437 Internal Only - General Default Value: net.ipv4.conf.default.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040209 | RULE ID: SV-244550r1017350 | CAT II 5. STIG ID: OL08-00-040209 | RULE ID: SV-248875r991589 | CAT II 6. STIG ID: RHEL-09-253040 | RULE ID: SV-257963r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006025 | RULE ID: SV-271869r1092319 | CAT II 9. STIG ID: SLES-15-040340 | RULE ID: SV-235019r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 438 Internal Only - General 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: It is still possible for even known gateways to be compromised. Setting net.ipv4.conf.all.secure_redirects to 0 the system will not accept any IPv4 routing table updates by possibly compromised known gateways. Audit: Verify net.ipv4.conf.all.secure_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.secure_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.secure_redirects Verify output is: net.ipv4.conf.all.secure_redirects = 0 2. Run the following script to verify net.ipv4.conf.all.secure_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.secure_redirects: Page 439 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.secure_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.secure_redirects = 0. Example output: - "net.ipv4.conf.all.secure_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.all.secure_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 440 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.secure_redirects lines that are not net.ipv4.conf.all.secure_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.secure_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.secure_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.secure_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.all.secure_redirects = 1 Page 441 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 442 Internal Only - General 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: It is still possible for even known gateways to be compromised. Setting net.ipv4.conf.default.secure_redirects to 0 the system the system will not accept IPv4 routing table updates by possibly compromised known gateways on a newly added network interface. Audit: Verify net.ipv4.conf.default.secure_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.secure_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.secure_redirects Verify output is: net.ipv4.conf.default.secure_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.secure_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.secure_redirects: Page 443 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.secure_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.secure_redirects = 0. Example output: - "net.ipv4.conf.default.secure_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.default.secure_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 444 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.secure_redirects lines that are not net.ipv4.conf.default.secure_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.secure_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.secure_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.secure_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.default.secure_redirects = 1 Page 445 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 446 Internal Only - General 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.conf.all.rp_filter controls reverse path filtering for IPv4 traffic on all network interfaces. Reverse path filtering is a security mechanism in Linux that helps prevent IP spoofing and other network attacks. When enabled, it checks if the source IP address of an incoming packet is reachable through the same network interface it was received on. If the packet's source address is not reachable through the interface it arrived on, the packet is dropped. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If this system is a router, and uses asymmetrical routing, this recommendation is not applicable. Rationale: Setting net.ipv4.conf.all.rp_filter to 1 is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Impact: If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Page 447 Internal Only - General Audit: Verify net.ipv4.conf.all.rp_filter is set to 1. 1. Run the following command to verify net.ipv4.conf.all.rp_filter is set to 1 in the running configuration: # sysctl net.ipv4.conf.all.rp_filter Verify output is: net.ipv4.conf.all.rp_filter = 1 2. Run the following script to verify net.ipv4.conf.all.rp_filter = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.rp_filter: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.rp_filter" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.rp_filter = 1. Example output: - "net.ipv4.conf.all.rp_filter = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 448 Internal Only - General Note: If multiple lines with net.ipv4.conf.all.rp_filter = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.rp_filter lines that are not net.ipv4.conf.all.rp_filter=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.rp_filter" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.rp_filter = 1 Example: Page 449 Internal Only - General # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.rp_filter = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.all.rp_filter = 2 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040285 | RULE ID: SV-230549r1017311 | CAT II 5. STIG ID: OL08-00-040285 | RULE ID: SV-248893r991589 | CAT II 6. STIG ID: RHEL-09-253035 | RULE ID: SV-257962r991589 | CAT II 7. STIG ID: ALMA-09-019820 | RULE ID: SV-269255r1050137 | CAT II 8. STIG ID: OL09-00-006024 | RULE ID: SV-271868r1092316 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 450 Internal Only - General 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.conf.default.rp_filter controls reverse path filtering for IPv4 traffic on newly added network interfaces. Reverse path filtering is a security mechanism in Linux that helps prevent IP spoofing and other network attacks. When enabled, it checks if the source IP address of an incoming packet is reachable through the same network interface it was received on. If the packet's source address is not reachable through the interface it arrived on, the packet is dropped. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If this system is a router, and uses asymmetrical routing, this recommendation is not applicable. Rationale: Setting net.ipv4.conf.default.rp_filter to 1 is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Impact: If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Page 451 Internal Only - General Audit: Verify net.ipv4.conf.default.rp_filter is set to 1. 1. Run the following command to verify net.ipv4.conf.default.rp_filter is set to 1 in the running configuration: # sysctl net.ipv4.conf.default.rp_filter Verify output is: net.ipv4.conf.default.rp_filter = 1 2. Run the following script to verify net.ipv4.conf.default.rp_filter = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.rp_filter: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.rp_filter" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.rp_filter = 1. Example output: - "net.ipv4.conf.default.rp_filter = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.default.rp_filter = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. Page 452 Internal Only - General • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.rp_filter lines that are not net.ipv4.conf.default.rp_filter=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.rp_filter" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.rp_filter = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.rp_filter = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 453 Internal Only - General Default Value: net.ipv4.conf.default.rp_filter = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253050 | RULE ID: SV-257965r991589 | CAT II 5. STIG ID: ALMA-09-019820 | RULE ID: SV-269255r1050137 | CAT II 6. STIG ID: OL09-00-006027 | RULE ID: SV-271871r1092325 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 454 Internal Only - General 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv4.conf.all.accept_source_route controls accepting of all IPv4 packets with the SSR or LSR option set on all interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Setting net.ipv4.conf.all.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: Verify net.ipv4.conf.all.accept_source_route is set to 0. 1. Run the following command to verify net.ipv4.conf.all.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.accept_source_route Verify output is: net.ipv4.conf.all.accept_source_route = 0 2. Run the following script to verify net.ipv4.conf.all.accept_source_route = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.accept_source_route: Page 455 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.accept_source_route = 0. Example output: - "net.ipv4.conf.all.accept_source_route = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.all.accept_source_route = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 456 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.accept_source_route lines that are not net.ipv4.conf.all.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.all.accept_source_route = 0 Page 457 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040239 | RULE ID: SV-244551r1017351 | CAT II 5. STIG ID: OL08-00-040239 | RULE ID: SV-248879r991589 | CAT II 6. STIG ID: RHEL-09-253020 | RULE ID: SV-257959r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006021 | RULE ID: SV-271865r1092307 | CAT II 9. STIG ID: SLES-15-040300 | RULE ID: SV-235014r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 458 Internal Only - General 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv4.conf.default.accept_source_route controls accepting of all IPv4 packets with the SSR or LSR option set on newly added network interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Setting net.ipv4.conf.default.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: Verify net.ipv4.conf.default.accept_source_route is set to 0. 1. Run the following command to verify net.ipv4.conf.default.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.accept_source_route Verify output is: net.ipv4.conf.default.accept_source_route = 0 Page 459 Internal Only - General 2. Run the following script to verify net.ipv4.conf.default.accept_source_route = 0 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.accept_source_route = 0. Example output: - "net.ipv4.conf.default.accept_source_route = 0" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.default.accept_source_route = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 460 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.accept_source_route lines that are not net.ipv4.conf.default.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 461 Internal Only - General Default Value: net.ipv4.conf.default.accept_source_route = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040249 | RULE ID: SV-244552r1017352 | CAT II 5. STIG ID: OL08-00-040249 | RULE ID: SV-248881r991589 | CAT II 6. STIG ID: RHEL-09-253045 | RULE ID: SV-257964r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006026 | RULE ID: SV-271870r1092322 | CAT II 9. STIG ID: SLES-15-040320 | RULE ID: SV-235016r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 462 Internal Only - General 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When enabled, this feature logs packets with un-routable source addresses to the kernel log. net.ipv4.conf.all.log_martians controls if IPv4 packets with un-routable source addresses on any network interface is logged to the kernel log. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Setting net.ipv4.conf.all.log_martians to 1 enables this feature. Logging these packets allows an administrator to investigate the possibility that an attacker is sending spoofed packets to their system. Audit: Verify net.ipv4.conf.all.log_martians is set to 1. 1. Run the following command to verify net.ipv4.conf.all.log_martians is set to 1 in the running configuration: # sysctl net.ipv4.conf.all.log_martians Verify output is: net.ipv4.conf.all.log_martians = 1 2. Run the following script to verify net.ipv4.conf.all.log_martians = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.all.log_martians: Page 463 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.log_martians" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.all.log_martians = 1. Example output: - "net.ipv4.conf.all.log_martians = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.conf.all.log_martians = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 464 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.all.log_martians lines that are not net.ipv4.conf.all.log_martians=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.log_martians" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.log_martians = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.log_martians = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.all.log_martians = 0 Page 465 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253025 | RULE ID: SV-257960r991589 | CAT II 5. STIG ID: ALMA-09-019380 | RULE ID: SV-269251r1050133 | CAT II 6. STIG ID: OL09-00-006022 | RULE ID: SV-271866r1092310 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 466 Internal Only - General 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When enabled, this feature logs packets with un-routable source addresses to the kernel log. net.ipv4.conf.default.log_martians controls if IPv4 packets with un-routable source addresses on a newly added network interface is logged to the kernel log. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Setting net.ipv4.conf.default.log_martians to 1 enables this feature. Logging these packets allows an administrator to investigate the possibility that an attacker is sending spoofed packets to their system. Page 467 Internal Only - General Audit: Verify net.ipv4.conf.default.log_martians is set to 1. 1. Run the following command to verify net.ipv4.conf.default.log_martians is set to 1 in the running configuration: # sysctl net.ipv4.conf.default.log_martians Verify output is: net.ipv4.conf.default.log_martians = 1 2. Run the following script to verify net.ipv4.conf.default.log_martians = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.conf.default.log_martians: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.log_martians" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.log_martians = 1. Example output: - "net.ipv4.conf.default.log_martians = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 468 Internal Only - General Note: If multiple lines with net.ipv4.conf.default.log_martians = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.conf.default.log_martians lines that are not net.ipv4.conf.default.log_martians=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.log_martians" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.log_martians = 1 Page 469 Internal Only - General Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.log_martians = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.conf.default.log_martians = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253030 | RULE ID: SV-257961r991589 | CAT II 5. STIG ID: ALMA-09-019380 | RULE ID: SV-269251r1050133 | CAT II 6. STIG ID: OL09-00-006023 | RULE ID: SV-271867r1092313 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 470 Internal Only - General 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When tcp_syncookies is set, the kernel will handle TCP SYN packets normally until the half-open connection queue is full, at which time, the SYN cookie functionality kicks in. SYN cookies work by not using the SYN queue at all. Instead, the kernel simply replies to the SYN with a SYN/ACK, but will include a specially crafted TCP sequence number that encodes the source and destination IP address and port number and the time the packet was sent. A legitimate connection would send the ACK packet of the three way handshake with the specially crafted sequence number. This allows the system to verify that it has received a valid response to a SYN cookie and allow the connection, even though there is no corresponding SYN in the queue. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Rationale: Attackers use SYN flood attacks to perform a denial of service attacked on a system by sending many SYN packets without completing the three way handshake. This will quickly use up slots in the kernel's half-open connection queue and prevent legitimate connections from succeeding. Setting net.ipv4.tcp_syncookies to 1 enables SYN cookies, allowing the system to keep accepting valid connections, even if under a denial of service attack. Audit: Verify net.ipv4.tcp_syncookies is set to 1. 1. Run the following command to verify net.ipv4.tcp_syncookies is set to 1 in the running configuration: # sysctl net.ipv4.tcp_syncookies Verify output is: net.ipv4.tcp_syncookies = 1 2. Run the following script to verify net.ipv4.tcp_syncookies = 1 is set in a file being used by systemd-sysctl to configure net.ipv4.tcp_syncookies: Page 471 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.tcp_syncookies" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.tcp_syncookies = 1. Example output: - "net.ipv4.tcp_syncookies = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: If multiple lines with net.ipv4.tcp_syncookies = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv4.tcp_syncookies lines that are not net.ipv4.tcp_syncookies=1. Example script: Page 472 Internal Only - General #!/usr/bin/env bash { l_option="net.ipv4.tcp_syncookies" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.tcp_syncookies = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.tcp_syncookies = 1" >> /etc/sysctl.d/60- ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv4.tcp_syncookies = 1 References: 1. CCI-001095 | CCI-002385 2. NIST SP 800-53 :: SC-5 (2) | NIST SP 800-53 :: SC-5 a 3. NIST SP 800-53A :: SC-5 (2).1 4. STIG ID: RHEL-09-253010 | RULE ID: SV-257957r1045009 | CAT II Page 473 Internal Only - General 5. STIG ID: ALMA-09-042480 | RULE ID: SV-269435r1050318 | CAT II 6. STIG ID: OL09-00-006050 | RULE ID: SV-271884r1092364 | CAT II 7. STIG ID: UBTU-22-253010 | RULE ID: SV-260522r1069097 | CAT II 8. STIG ID: UBTU-24-600190 | RULE ID: SV-270753r1066748 | CAT II 9. STIG ID: SLES-15-010310 | RULE ID: SV-234829r958528 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 474 Internal Only - General 3.3.2 Configure IPv6 parameters net.ipv6 kernel parameters control various aspects of the IPv6 network stack. These parameters effect functions to include routing, TCP, and security. Note: If IPv6 has been disabled on the system, the Recommendations in this subsection are not applicable and should be skipped. The following script creates and runs a function called f_ipv6_chk that may be used to determine if IPv6 has been disabled on the system: #!/usr/bin/env bash f_ipv6_chk() { a_output=() ! grep -Pqs -- '^\h*0\b' /sys/module/ipv6/parameters/disable && \ a_output+=(" - IPv6 is disabled") if sysctl net.ipv6.conf.all.disable_ipv6 | \ grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\b" && \ sysctl net.ipv6.conf.default.disable_ipv6 | \ grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\b"; then [ "${#a_output[@]}" -le 0 ] && a_output+=(" - IPv6 is disabled") fi [ "${#a_output[@]}" -le 0 ] && a_output+=(" - IPv6 is not disabled") printf '%s\n' "" "${a_output[@]}" "" } f_ipv6_chk Page 475 Internal Only - General 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The net.ipv6.conf.all.forwarding flag tells the system whether it can forward IPv6 packets or not. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Setting net.ipv6.conf.all.forwarding to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will not be able to forward IPv6 packets. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.forwarding is set to 0. 1. Run the following command to verify net.ipv6.conf.all.forwarding is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.forwarding Verify output is: net.ipv6.conf.all.forwarding = 0 Page 476 Internal Only - General 2. Run the following script to verify net.ipv6.conf.all.forwarding = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.all.forwarding: #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.all.forwarding = 0. Example output: - "net.ipv6.conf.all.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.all.forwarding = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 477 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.all.forwarding lines that are not net.ipv6.conf.all.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.forwarding = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 478 Internal Only - General Default Value: net.ipv6.conf.all.forwarding = 0 References: 1. CI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040260 | RULE ID: SV-230540r1017302 | CAT II 5. STIG ID: OL08-00-040260 | RULE ID: SV-248883r991589 | CAT II 6. STIG ID: RHEL-09-254025 | RULE ID: SV-257974r991589 | CAT II 7. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 8. STIG ID: OL09-00-006043 | RULE ID: SV-271880r1092352 | CAT II 9. STIG ID: SLES-15-040381 | RULE ID: SV-235025r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 479 Internal Only - General 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The net.ipv6.conf.all.forwarding flag tells the system whether it can forward IPv6 on the default or newly added network interface. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.forwarding is set to 0. 1. Run the following command to verify net.ipv6.conf.default.forwarding is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.forwarding Verify output is: net.ipv6.conf.default.forwarding = 0 2. Run the following script to verify net.ipv6.conf.default.forwarding = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.default.forwarding: Page 480 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.default.forwarding = 0. Example output: - "net.ipv6.conf.default.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.default.forwarding = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 481 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.default.forwarding lines that are not net.ipv6.conf.default.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.forwarding = 0" >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.default.forwarding = 0 Page 482 Internal Only - General References: 1. CI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 5. STIG ID: SLES-15-040382 | RULE ID: SV-235026r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 483 Internal Only - General 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv6.conf.all.accept_redirects controls accepting of all IPv6 ICMP redirected packets on all interfaces. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv6.conf.all.accept_redirects to 0, the system will not accept any IPv6 ICMP redirect messages, and therefore, won't allow outsiders to update the system's routing tables. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_redirects is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_redirects Verify output is: net.ipv6.conf.all.accept_redirects = 0 2. Run the following script to verify net.ipv6.conf.all.accept_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.all.accept_redirects: Page 484 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.all.accept_redirects = 0. Example output: - "net.ipv6.conf.all.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.all.accept_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 485 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.all.accept_redirects lines that are not net.ipv6.conf.all.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Page 486 Internal Only - General Default Value: net.ipv6.conf.all.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040280 | RULE ID: SV-230544r1017306 | CAT II 5. STIG ID: OL08-00-040280 | RULE ID: SV-248888r991589 | CAT II 6. STIG ID: RHEL-09-254015 | RULE ID: SV-257972r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006041 | RULE ID: SV-271878r1092346 | CAT II 9. STIG ID: SLES-15-040341 | RULE ID: SV-235020r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 487 Internal Only - General 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv6.conf.default.accept_redirects controls accepting of all IPv6 ICMP redirected packets on a newly added network interface. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv6.conf.default.accept_redirects to 0, the system will not accept IPv6 ICMP redirect messages on a newly added network interface. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_redirects is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_redirects Verify output is: net.ipv6.conf.default.accept_redirects = 0 2. Run the following script to verify net.ipv6.conf.default.accept_redirects = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.default.accept_redirects: Page 488 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.default.accept_redirects = 0. Example output: - "net.ipv6.conf.default.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.default.accept_redirects = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 489 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.default.accept_redirects lines that are not net.ipv6.conf.default.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.default.accept_redirects = 1 Page 490 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040210 | RULE ID: SV-230535r1017297 | CAT II 5. STIG ID: OL08-00-040210 | RULE ID: SV-248876r991589 | CAT II 6. STIG ID: RHEL-09-254035 | RULE ID: SV-257976r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006045 | RULE ID: SV-271882r1092358 | CAT II 9. STIG ID: SLES-15-040350 | RULE ID: SV-235021r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 491 Internal Only - General 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv6.conf.all.accept_source_route controls accepting of all IPv6 packets with the SSR or LSR option set on all interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled this recommendation is not applicable. Rationale: Setting net.ipv6.conf.all.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Page 492 Internal Only - General Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_source_route is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_source_route Verify output is: net.ipv6.conf.all.accept_source_route = 0 2. Run the following script to verify net.ipv6.conf.all.accept_source_route = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.all.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv4.conf.default.forwarding = 0. Example output: - "net.ipv6.conf.all.accept_source_route = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Page 493 Internal Only - General Note: If multiple lines with net.ipv6.conf.all.accept_source_route = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.all.accept_source_route lines that are not net.ipv6.conf.all.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_source_route = 0 Example: Page 494 Internal Only - General # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.all.accept_source_route = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040240 | RULE ID: SV-230538r1017300 | CAT II 5. STIG ID: OL08-00-040240 | RULE ID: SV-248880r991589 | CAT II 6. STIG ID: RHEL-09-254020 | RULE ID: SV-257973r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006042 | RULE ID: SV-271879r1092349 | CAT II 9. STIG ID: SLES-15-040310 | RULE ID: SV-235015r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 495 Internal Only - General 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv6.conf.default.accept_source_route controls accepting of all IPv6 packets with the SSR or LSR option set on newly added network interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled this recommendation is not applicable. Rationale: Setting net.ipv6.conf.default.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Page 496 Internal Only - General Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_source_route is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_source_route Verify output is: net.ipv6.conf.default.accept_source_route = 0 2. Run the following script to verify net.ipv6.conf.default.accept_source_route = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.default.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.default.accept_source_route = 0. Example output: Page 497 Internal Only - General - "net.ipv6.conf.default.accept_source_route = 0" is set in: "/etc/sysctl.d/60-ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.default.accept_source_route = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.default.accept_source_route lines that are not net.ipv6.conf.default.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: Page 498 Internal Only - General net.ipv6.conf.default.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.default.accept_source_route = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040250 | RULE ID: SV-230539r1017301 | CAT II 5. STIG ID: OL08-00-040250 | RULE ID: SV-248882r991589 | CAT II 6. STIG ID: RHEL-09-254040 | RULE ID: SV-257977r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006046 | RULE ID: SV-271883r1092361 | CAT II 9. STIG ID: SLES-15-040321 | RULE ID: SV-235017r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 499 Internal Only - General 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Routers periodically multicast Router Advertisement messages to announce their availability and convey information to neighboring nodes that enable them to be automatically configured on the network. net.ipv6.conf.all.accept_ra controls accepting any IPv6 RA messages on any network device. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, this recommendation is not applicable. Rationale: It is recommended that systems do not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_ra is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_ra is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_ra Verify output is: net.ipv6.conf.all.accept_ra = 0 2. Run the following script to verify net.ipv6.conf.all.accept_ra = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.all.accept_ra: Page 500 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_ra" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.all.accept_ra = 0. Example output: - "net.ipv6.conf.all.accept_ra = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.all.accept_ra = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 501 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.all.accept_ra lines that are not net.ipv6.conf.all.accept_ra=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_ra" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_ra = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_ra = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.all.accept_ra = 1 Page 502 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040261 | RULE ID: SV-230541r1017303 | CAT II 5. STIG ID: OL08-00-040261 | RULE ID: SV-248884r991589 | CAT II 6. STIG ID: RHEL-09-254010 | RULE ID: SV-257971r991589 | CAT II 7. STIG ID: ALMA-09-018500 | RULE ID: SV-269243r1050125 | CAT II 8. STIG ID: OL09-00-006040 | RULE ID: SV-271877r1092343 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 503 Internal Only - General 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Routers periodically Multicast Router Advertisement (RA) messages to announce their availability and convey information to neighboring nodes that enable them to be automatically configured on the network. net.ipv6.conf.default.accept_ra controls accepting IPv6 RA messages on newly added network devices. More information about the kernel parameter configuration files, their location, and load preference is available in the "Configure Network Kernel Parameters" section overview. Note: If IPv6 has been disabled, this recommendation is not applicable. Rationale: It is recommended that systems do not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_ra is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_ra is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_ra Verify output is: net.ipv6.conf.default.accept_ra = 0 2. Run the following script to verify net.ipv6.conf.default.accept_ra = 0 is set in a file being used by systemd-sysctl to configure net.ipv6.conf.default.accept_ra: Page 504 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_ra" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Psio '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in: \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Verify output includes net.ipv6.conf.default.accept_ra = 0. Example output: - "net.ipv6.conf.default.accept_ra = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: If multiple lines with net.ipv6.conf.default.accept_ra = are returned. • The first line includes the value being used by systemd-sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. • Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd-sysctl due to system configuration changes. Page 505 Internal Only - General Remediation: 1. Review all files being used by systemd-sysctl and comment out or remove all net.ipv6.conf.default.accept_ra lines that are not net.ipv6.conf.default.accept_ra=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_ra" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Psio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Psio -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Psivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.accept_ra = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_ra = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration files: # sysctl --system Default Value: net.ipv6.conf.default.accept_ra = 1 Page 506 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040262 | RULE ID: SV-230542r1017304 | CAT II 5. STIG ID: OL08-00-040262 | RULE ID: SV-248885r991589 | CAT II 6. STIG ID: RHEL-09-254030 | RULE ID: SV-257975r991589 | CAT II 7. STIG ID: ALMA-09-018500 | RULE ID: SV-269243r1050125 | CAT II 8. STIG ID: OL09-00-006044 | RULE ID: SV-271881r1092355 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 507 Internal Only - General 4 Host Based Firewall A firewall is a set of rules. When a data packet moves into or out of a protected network space, its contents (in particular, information about its origin, target, and the protocol it plans to use) are tested against the firewall rules to see if it should be allowed through. To provide a Host Based Firewall, the Linux kernel includes support for NFTables. NFTables is subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames. NFTables replaces parts of Netfilter, while keeping and reusing most of it. NFTables utilizes the building blocks of the Netfilter infrastructure, such as the existing hooks into the networking stack, connection tracking system, userspace queueing component, and logging subsystem. In order to configure firewall rules for NFTables, a firewall utility needs to be installed. Guidance has been included for Uncomplicated Firewall (UFW) which provides firewall features by acting as a front-end for the Linux kernel's netfilter framework via the NFTables backend, acting as an alternative to the nft command line program. UFW supports both IPv4 and IPv6 networks. Important: This Benchmark includes guidance for configuring NFTables though the UFW front end utility. If your organization is using a different Host Based Firewall, or a different utility to configure the Host Based Firewall, we recommend verifying that your site's configuration meets the Recommendations in this section, otherwise this section may be skipped. Note: • Only one method should be used to configure a firewall on the system. Use of more than one method could produce unexpected results. • NFTables is the default packet filtering framework. Though IPTables is still supported, this support is done indirectly through UFW's ability to translate IPTables commands to NFTables. • This section is intended only to ensure the resulting firewall rules are in place. Page 508 Internal Only - General 4.1 Configure Uncomplicated Firewall In order to configure durable firewall rules a firewall utility needs to be installed. Uncomplicated Firewall (UFW) is the recommended utility and is used in guidance provided in the following recommendations. UFW is a user-friendly frontend firewall utility. It uses configurable default policies, and allows administrators to create specific rules to permit or deny connections based on applications, ports, or IP addresses. You can enable the firewall, view its status, and manage rules using simple command-line tools to secure your system. Warning: Configuration of a live systems firewall directly over a remote connection will often result in being locked out. It is advised to have a known good firewall configuration set to run on boot and to configure an entire firewall structure in a script that is then run and tested before saving to boot. Page 509 Internal Only - General 4.1.1 Ensure ufw is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Uncomplicated Firewall (ufw) is a frontend for iptables and is particularly well-suited for host-based firewalls. ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall Rationale: UFW acts as a frontend for both iptables and nftables and can use either as its backend, though the specific backend depends on the Linux distribution and system configuration. You can enable the firewall, view its status, and manage rules using simple command- line tools to secure your system. Impact: Changing firewall settings while connected over the network can result in being locked out of the system. Audit: Run the following command to verify that Uncomplicated Firewall (UFW) is installed: # dpkg-query -s ufw &>/dev/null && echo "ufw is installed" ufw is installed Remediation: Run the following command to install Uncomplicated Firewall (UFW): # apt install ufw References: 1. CCI-002314 2. NIST SP 800-53 :: AC-17 (1) 3. STIG ID: UBTU-22-251010 | Rule ID: SV-260514r958672 | CAT II 4. STIG ID: UBTU-24-100300 | Rule ID: SV-270654r1067143 | CAT II Page 510 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 511 Internal Only - General 4.1.2 Ensure ufw service is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The service, ufw.service, manages UFW. This service is responsible for applying and maintaining firewall rules, controlling which network traffic is allowed in and out of the system. Note: • When running ufw enable or starting ufw.service, ufw will flush its chains. This is required so ufw can maintain a consistent state, but it may drop existing connections, eg ssh. ufw does support adding rules before enabling the firewall. • Once ufw is 'enabled', ufw will not flush the chains when adding or removing rules (but will when modifying a rule or changing the default policy) • By default ufw will prompt when enabling the firewall while running under ssh. This can be disabled by using ufw --force enable Warning: If a rule for openSSH server does not exist, and openSSH is used to administer the host, the ability to administer and/or connect to the host may be lost. Example command to create a rule to allow ssh: # ufw allow proto tcp from any to any port 22 This rule will allow connection to the ssh server from any location. It is highly recommended that this rule be modified to restrict ssh access to only required hosts and to follow local site policy. • The rules will still be flushed, but the ssh port will be open after enabling the firewall. Please note that once ufw is 'enabled', ufw will not flush the chains when adding or removing rules (but will when modifying a rule or changing the default policy) • By default, ufw will prompt when enabling the firewall while running under ssh. This can be disabled by using ufw --force enable Rationale: The ufw service must be enabled and running in order for ufw to protect the system Impact: Changing firewall settings while connected over network can result in being locked out of the system. Page 512 Internal Only - General Audit: Run the following command to verify ufw.service is enabled: # systemctl is-enabled ufw.service enabled Run the following command to verify ufw.service is active: # systemctl is-active ufw.service active Run the following command to verify ufw is active # ufw status Status: active Remediation: Run the following command to unmask the ufw.service: # systemctl unmask ufw.service Run the following command to enable and start the ufw.service: # systemctl --now enable ufw.service active Run the following command to enable ufw: # ufw enable Default Value: Inactive References: 1. CCI-002314 2. NIST SP 800-53 :: AC-17 (1) 3. STIG ID: UBTU-20-010434 | Rule ID: SV-238355r958672 | CAT II 4. STIG ID: UBTU-22-251015 | Rule ID: SV-260515r958672 | CAT II 5. STIG ID: UBTU-24-100310 | Rule ID: SV-270655r1067145 | CAT II 6. http://manpages.ubuntu.com/manpages/precise/en/man8/ufw.8.html Page 513 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 514 Internal Only - General 4.1.3 Ensure ufw incoming default is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The default policy for incoming traffic determines if connections attempting to reach your server from external sources will be allowed without requiring specific UFW rules. Rationale: With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to allow list acceptable usage than to deny list unacceptable usage. Impact: Any port or protocol without a explicit allow before the default deny will be blocked. A deny policy silently drops packs causing an eventual time out with no response while a 'reject' policy sends an immediate and explicit "connection refused" or "destination unreachable" message in response. The following is and example of a command to create a rule to allow connection to the ssh server on the host. This rule should be considered before applying the default deny. Example: # ufw allow ssh Audit: Run the following command to verify that the default policy for incoming is deny or reject: # ufw status verbose | awk -F',' '$1~/Default/ {print $1}' Example output: Default: deny (incoming) Remediation: Run the following command to set the default for incoming to deny: # ufw default deny incoming Warning: Any port or protocol without a explicit allow before the default deny will be blocked. References: 1. NIST SP 800-53 Rev. 5: SC-7 Page 515 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 516 Internal Only - General 4.1.4 Ensure ufw outgoing default is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The default policy for outgoing traffic determines if applications and services running on your server can initiate connections to external networks without requiring specific UFW rules. Rationale: With a default deny outgoing policy the firewall will deny ALL outgoing traffic and is a highly restrictive policy that requires the addition of specific allow rules. Impact: Any port and protocol not explicitly allowed will be blocked. The following rules are an example of some outgoing allow rules that should be considered before applying this default deny. ufw allow out http ufw allow out https ufw allow out ntp # Network Time Protocol ufw allow out to any port 53 # DNS ufw allow out to any port 853 # DNS over TLS ufw logging on Audit: Run the following command and verify that the default policy for outgoing is deny or reject: # ufw status verbose | awk -F',' '$1~/Default/ {print $2}' Example output: deny (outgoing) Remediation: Run the following command to set the default for outgoing to deny: # ufw default deny outgoing Warning: Any port or protocol without a explicit allow before the default deny will be blocked. Default Value: allow (outgoing) Page 517 Internal Only - General References: 1. CCI-000382 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (iii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 518 Internal Only - General 4.1.5 Ensure ufw routed default is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The default policy for routed traffic determines if UFW forwards traffic between different network interfaces without requiring specific UFW rules. Rationale: A default disabled or deny policy ensures that UFW does not forward traffic between different network interfaces by default. This reduces the risk from unwanted or malicious routed traffic. Impact: Any port and protocol will be prevented for being routed. Audit: Run the following command and verify that the default policy for routed is disabled or deny: # ufw status verbose | awk -F',' '$1="Default"{print $3}' Example output: disabled (routed) Important: Any port and protocol will be prevented for being routed. Remediation: Run the following command to set the defalut for routed to disabled: # ufw default disabled routed Default Value: disabled References: 1. CCI-000382 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (iii) Page 519 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 520 Internal Only - General 5 Access Control Page 521 Internal Only - General 5.1 Configure SSH Server Note: The recommendations in this section only apply if SSH server is installed on the system. If remote access is not required the SSH server can be removed and this section skipped. Secure Shell (SSH) is a secure, encrypted replacement for common login services such as telnet, ftp, rlogin, rsh, and rcp. It is strongly recommended that sites abandon older clear-text login protocols and use SSH to prevent session hijacking and sniffing of sensitive data off the network. sshd_config: • First occurrence of an option takes precedence. • The default Include location is the /etc/ssh/sshd_config.d directory. • The audits of the running configuration in this section are run in the context of the root user, the local host name, and the local host's IP address. If a Match block exists that matches one of these criteria, the output of the audit will be from the match block. The respective matched criteria should be replaced with a non- matching substitution. • Defaults: o The file /etc/ssh/sshd_config includes the line: Include /etc/ssh/sshd_config.d/*.conf. This line must appear before any lines containing the Cipher argument o This directory /etc/ssh/sshd_config.d/ includes a file /etc/ssh/sshd_config.d/50-redhat.conf o The file /etc/ssh/sshd_config.d/50-redhat.conf includes the line Include /etc/crypto-policies/back-ends/opensshserver.config • Ciphers, MACs, and KexAlgorithms: o Though these options may be configured through the Ciphers, MACs, and KexAlgorithms options in the /etc/ssh/sshd_config file, it is highly recommended that they are configured through system-wide-crypto-policy. o If the recommendations in the subsection "Configure system wide crypto policy" have been followed, the audits should be in a passing state. Please review that section before following the Remediation Procedure for these Recommendations. o By default, system-wide-crypto-policy is applied to the openSSH server. If the following defaults don't exist due to modifications or upgrade from a earlier release, the system-wide-crypto-policy may not be included by the openSSH server. It is recommended that these defaults be restored, created, or the line Include /etc/crypto-policies/back- ends/opensshserver.config be added before any lines containing the Cipher, MACs, or KexAlgorithms arguments. • Include: o Include the specified configuration file(s). o Multiple pathnames may be specified and each pathname may contain glob(7) wildcards that will be expanded and processed in lexical order. Page 522 Internal Only - General oFiles without absolute paths are assumed to be in /etc/ssh/. oAn Include directive may appear inside a Match block to perform conditional inclusion. • Match: o Introduces a conditional block. If all of the criteria on the Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another Match line or the end of the file. If a keyword appears in multiple Match blocks that are satisfied, only the first instance of the keyword is applied. o The arguments to Match are one or more criteria-pattern pairs or the single token All which matches all criteria. The available criteria are User, Group, Host, LocalAddress, LocalPort, and Address. o The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNS section of ssh_config(5). o The patterns in an Address criteria may additionally contain addresses to match in CIDR address/masklen format, such as 192.0.2.0/24 or 2001:db8::/32. Note that the mask length provided must be consistent with the address - it is an error to specify a mask length that is too long for the address or one with bits set in this host portion of the address. For example, 192.0.2.0/33 and 192.0.2.0/8, respectively. o Only a subset of keywords may be used on the lines following a Match keyword. Available keywords are available in the ssh_config man page. • Once changes have been made to the sshd configuration, the sshd.service must be reloaded. Command to re-load the SSH daemon configuration: # systemctl reload-or-restart sshd.service sshd command: • -T - Extended test mode. Check the validity of the configuration file, output the effective configuration to stdout and then exit. Optionally, Match rules may be applied by specifying the connection parameters using one or more -C options. • -C - connection_spec. Specify the connection parameters to use for the -T extended test mode. If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr, user, host, laddr, lport, and rdomain and correspond to source address, user, resolved source host name, local address, local port number and routing domain respectively. Page 523 Internal Only - General 5.1.1 Ensure access to /etc/ssh/sshd_config is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: /etc/ssh/sshd_config is the main configuration file for the OpenSSH server daemon (sshd), which manages secure remote logins and other SSH services. /etc/ssh/sshd_config is the default location for drop-in configuration files used by sshd. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Configuration specifications for sshd need to be protected from unauthorized changes by non-privileged users. Audit: Run the following command to verify access to /etc/ssh/sshd_config is configured: # stat -Lc 'File: "%n" Mode: "%#a" Owner: "%U" Group: "%G"' /etc/ssh/sshd_config Verify mode is 0600 or more restrictive, owner is root, and group is root. Example output: File: "/etc/ssh/sshd_config" Mode: "0600" Owner: "root" Group: "root" Run the following script to verify files in /etc/ssh/sshd_config.d/ ending in .conf are configured: • Mode 0600 or more restrictive • Owned by the root user • Group owned by the group root. #!/usr/bin/env bash { while IFS= read -r -d $'\0' l_file; do stat -Lc 'File: "%n" Mode: "%#a" Owner: "%U" Group: "%G"' "$l_file" done < <(find /etc/ssh/sshd_config.d/ -xdev -mount -type f -name '*.conf' \ \( -perm /077 -o ! -user root -o ! -group root \) -print0 2>/dev/null) } Nothing should be returned Note: If other locations are listed in an Include statement, *.conf files in these locations should also be checked. Page 524 Internal Only - General Remediation: Run the following script to set ownership and permissions on /etc/ssh/sshd_config and files ending in .conf in the /etc/ssh/sshd_config.d directory: #!/usr/bin/env bash { chmod u-x,og-rwx /etc/ssh/sshd_config chown root:root /etc/ssh/sshd_config while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then chmod u-x,og-rwx "$l_file" chown root:root "$l_file" fi done < <(find /etc/ssh/sshd_config.d -type f -print0 2>/dev/null) } Note: If other locations are listed in an Include statement, *.conf files in these locations access should also be modified. Default Value: Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 525 Internal Only - General 5.1.2 Ensure access to SSH private host key files is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An SSH private key is one of two files used in SSH public key authentication. In this authentication method, the possession of the private key is proof of identity. Only a private key that corresponds to a public key will be able to authenticate successfully. The private keys need to be stored and handled carefully, and no copies of the private key should be distributed. Rationale: If an threat actor obtains the private SSH host key file, the host could be impersonated. Impact: If the private keys used by the openSSH server have the incorrect mode, owner, or group owner the server service may not start. Audit: Verify SSH private host key files are: • Mode 0600. • Owned by the root user. • Group owned by the group root. Run the following script to generate a list of SSH private host key files: #!/usr/bin/env bash { l_sshd_cmd="$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" l_keygen="$(readlink -e /usr/bin/ssh-keygen || readlink -e /bin/ssh- keygen)" while IFS= read -r l_file; do "$l_keygen" -lf &>/dev/null "$l_file" && \ stat -Lc 'File: "%n" Mode: "%#a" Owner: "%U" Group: "%G"' "$l_file" done < <("$l_sshd_cmd" -T | awk '$1=="hostkey" {print $2}') } Example output: File: "/etc/ssh/ssh_host_rsa_key" Mode: "0600" Owner: "root" Group: "root" File: "/etc/ssh/ssh_host_ecdsa_key" Mode: "0600" Owner: "root" Group: "root" File: "/etc/ssh/ssh_host_ed25519_key" Mode: "0600" Owner: "root" Group: "root" Verify all files in the output are: Page 526 Internal Only - General • Mode 0600. • Owner by the user root. • Group owned by the group root. Remediation: Update the access to the private keys being used by the open SSH server. • mode to 0600. • owner to the user root. • group owner to the group root. Run the following script to update the access on the private keys used by the open SSH server: #!/usr/bin/env bash { l_sshd_cmd="$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" l_keygen="$(readlink -e /usr/bin/ssh-keygen || readlink -e /bin/ssh- keygen)" while IFS= read -r l_file; do if "$l_keygen" -lf &>/dev/null "$l_file"; then chown root:root "$l_file" chmod 0600 "$l_file" done < <("$l_sshd_cmd" -T | awk '$1=="hostkey" {print $2".pub"}' 2>/dev/null) } Default Value: Mode: "0600" Owner: "root" Group: "root" References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-010490 | RULE ID: SV-230287r1017098 | CAT II 5. STIG ID: RHEL-09-255120 | RULE ID: SV-258000r1045063 | CAT II 6. STIG ID: ALMA-09-020920 | RULE ID: SV-269265r1050147 | CAT II 7. STIG ID: SLES-15-040250 | RULE ID: SV-235009r991589 | CAT II Page 527 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 528 Internal Only - General 5.1.3 Ensure access to SSH public host key files is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An SSH public key is one of two files used in SSH public key authentication. In this authentication method, a public key is a key that can be used for verifying digital signatures generated using a corresponding private key. Only a public key that corresponds to a private key will be able to authenticate successfully. Rationale: If a public host key file is modified by an unauthorized user, the SSH service may be compromised. Audit: Verify SSH public host key files are: • Mode 0644 or more restrictive. • Owned by the root user. • Group owned by the group root. Run the following script to generate a list of SSH public host key files: #!/usr/bin/env bash { l_sshd_cmd="$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" l_keygen="$(readlink -e /usr/bin/ssh-keygen || readlink -e /bin/ssh- keygen)" while IFS= read -r l_file; do "$l_keygen" -lf &>/dev/null "$l_file" && \ stat -Lc 'File: "%n" Mode: "%#a" Owner: "%U" Group: "%G"' "$l_file" done < <("$l_sshd_cmd" -T | awk '$1=="hostkey" {print $2".pub"}' 2>/dev/null) } Example output: File: "/etc/ssh/ssh_host_rsa_key.pub" Mode: "0644" Owner: "root" Group: "root" File: "/etc/ssh/ssh_host_ecdsa_key.pub" Mode: "0644" Owner: "root" Group: "root" File: "/etc/ssh/ssh_host_ed25519_key.pub" Mode: "0644" Owner: "root" Group: "root" Verify all files in the output are: • Mode 0644. • Owner by the user root. • Group owned by the group root. Page 529 Internal Only - General Remediation: Update the access to the public keys being used by the open SSH server. • mode to 0644. • owner to the user root. • group owner to the group root. Run the following script to update the access on the public keys used by the open SSH server: #!/usr/bin/env bash { l_sshd_cmd="$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" l_keygen="$(readlink -e /usr/bin/ssh-keygen || readlink -e /bin/ssh- keygen)" while IFS= read -r l_file; do if "$l_keygen" -lf &>/dev/null "$l_file"; then chown root:root "$l_file" chmod 0644 "$l_file" done < <("$l_sshd_cmd" -T | awk '$1=="hostkey" {print $2".pub"}' 2>/dev/null) } Default Value: Mode: "0644" Owner: "root" Group: "root" References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 530 Internal Only - General 5.1.4 Ensure sshd access is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are several options available to limit which users and group can access the system via SSH. It is recommended that at least one of the following options be leveraged: • AllowUsers: o The AllowUsers variable gives the system administrator the option of allowing specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by only allowing the allowed users to log in from a particular host, the entry can be specified in the form of user@host. • AllowGroups: o The AllowGroups variable gives the system administrator the option of allowing specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable. • DenyUsers: o The DenyUsers variable gives the system administrator the option of denying specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by specifically denying a user's access from a particular host, the entry can be specified in the form of user@host. • DenyGroups: o The DenyGroups variable gives the system administrator the option of denying specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Restricting which users can remotely access the system via SSH will help ensure that only authorized users access the system. Page 531 Internal Only - General Impact: These options are "ANDed" together. If both AllowUsers and AllowGroups are set, connections will be limited to the list of users that are also a member of an allowed group. It is recommended that only one be set for clarity and ease of administration. Audit: Run the following command and verify the output: # sshd -T | grep -Pi -- '^\h*(allow|deny)(users|groups)\h+\H+' Verify that the output matches at least one of the following lines: allowusers -OR- allowgroups -OR- denyusers -OR- denygroups Review the list(s) to ensure included users and/or groups follow local site policy - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '^\h*(allow|deny)(users|groups)\h+\H+' Remediation: Edit the /etc/ssh/sshd_config file to set one or more of the parameters above any Include and Match set statements as follows: AllowUsers - AND/OR - AllowGroups Note: It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user or group and forget to add it to the deny list. Default Value: None References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: AC-3. MP-2 3. SSHD(8) 4. https://documentation.suse.com/en-us/sles/15-SP6/html/SLES-all/cha-ssh.html Page 532 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 533 Internal Only - General 5.1.5 Ensure sshd Banner is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Banner parameter specifies a file whose contents must be sent to the remote user before authentication is permitted. By default, no banner is displayed. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Banners are used to warn connecting users of the particular site's policy regarding connection. Presenting a warning message prior to the normal user login may assist the prosecution of trespassers on the computer system. Not having a properly configured SSH banner, or leaving it at the default value, can expose an organization to legal and compliance risks by failing to provide users with necessary access policies or warnings about unauthorized access. It may violate regulations requiring user acknowledgment of system usage rules, reduce security awareness, and leave systems vulnerable to malicious or unintended access. Audit: 1. Ensure the the Banner option is set. Run the following command to verify Banner is set: # sshd -T | grep -Pi -- '^banner\h+\/\H+' Example: banner /etc/issue.net - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '^banner\h+\/\H+' 2. Ensure the banner matches local site policy. Run the following command and verify that the contents or the file being called by the Banner argument match site policy: # [ -e "$(sshd -T | awk '$1 == "banner" {print $2}')" ] && cat "$(sshd -T | awk '$1 == "banner" {print $2}')" Run the following command and verify no results are returned: # grep -Psi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut - d= -f2 | sed -e 's/"//g')\b)" "$(sshd -T | awk '$1 == "banner" {print $2}')" Page 534 Internal Only - General Remediation: Edit the /etc/ssh/sshd_config file to set the Banner parameter above any Include and Match entries as follows: Banner /etc/issue.net Edit the file being called by the Banner argument with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # printf '%s\n' "Authorized users only. All activity may be monitored and reported." > "$(sshd -T | awk '$1 == "banner" {print $2}')" References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 535 Internal Only - General 5.1.6 Ensure sshd Ciphers are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Secure Shell (SSH) ciphers are encryption algorithms used by the SSH protocol to secure data transmitted between a client and a server. They protect the privacy and integrity of the connection, using symmetric encryption to encrypt data after a secure session is established. During connection setup, the client and server negotiate to select the strongest available cipher that both support, ensuring the connection is as secure as possible More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Weak ciphers that are used for authentication to the cryptographic module cannot be relied upon to provide confidentiality or integrity, and system data may be compromised. Impact: A too restrictive list of ciphers can lead to the "no matching cipher found" error during an SSH connection. This error indicates that the SSH client and server are unable to agree on a common cipher to use for the secure communication. This typically occurs due to a mismatch in supported ciphers or when older, less secure ciphers are disabled on one side but still expected by the other. Audit: Run the following command to verify none of the "weak" ciphers are being used: # sshd -T | grep -Pi -- '^ciphers\h+\"?([^#\n\r]+,)?((3des|blowfish|cast128|aes(128|192|256))- cbc|arcfour(128|256)?|rijndael-cbc@lysator\.liu\.se)\b' Nothing should be returned. Run the following command to determine if the chacha20-poly1305@openssh.com cipher is being used. # sshd -T 2>&1 | awk '($1=="ciphers" && $2~/chacha20- poly1305@openssh\.com/){print}' If any line is returned, review CVE-2023-48795 and verify the system has been patched. Page 536 Internal Only - General Remediation: - IF - CVE-2023-48795 has been addressed, and it meets local site policy, chacha20-poly1305 may be removed from the list of excluded ciphers. Create or edit a file in /etc/crypto-policies/policies/modules/ ending in .pmod and add or modify the the following line: cipher@SSH = -3DES-CBC -AES-128-CBC -AES-192-CBC -AES-256-CBC -CHACHA20- POLY1305 Example: # printf '%s\n' "# This is a subpolicy to disable weak ciphers" "# for the SSH protocol (libssh and OpenSSH)" "cipher@SSH = -3DES-CBC -AES-128-CBC -AES- 192-CBC -AES-256-CBC -CHACHA20-POLY1305" >> /etc/crypto- policies/policies/modules/NO-SSHWEAKCIPHERS.pmod Note: Some organizations may have stricter requirements for approved ciphers. Ensure that ciphers used are in compliance with site policy. Run the following command to update the system-wide cryptographic policy # update-crypto-policies --set ::: Example: # update-crypto-policies --set DEFAULT:NO-SHA1:NO-WEAKMAC:NO-SSHCBC:NO- SSHCHACHA20:NO-SSHWEAKCIPHERS Run the following command to reload the openSSH server to make your cryptographic settings effective: # systemctl reload-or-restart sshd Default Value: Ciphers aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256- ctr,aes128-gcm@openssh.com,aes128-ctr References: 1. https://nvd.nist.gov/vuln/detail/CVE-2023-48795 2. https://nvd.nist.gov/vuln/detail/CVE-2019-1543 3. https://nvd.nist.gov/vuln/detail/CVE-2016-2183 4. https://nvd.nist.gov/vuln/detail/CVE-2008-5161 5. https://www.openssh.com/txt/cbc.adv 6. https://www.openssh.com/txt/cbc.adv 7. SSHD_CONFIG(5) 8. NIST SP 800-53 Rev. 5: SC-8 Page 537 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 538 Internal Only - General 5.1.7 Ensure sshd ClientAliveInterval and ClientAliveCountMax are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Note: To clarify, the two settings described below are only meant for idle connections from a protocol perspective and are not meant to check if the user is active or not. An idle user does not mean an idle connection. SSH does not and never had, intentionally, the capability to drop idle users. In SSH versions before 8.2p1 there was a bug that caused these values to behave in such a manner that they were abused to disconnect idle users. This bug has been resolved in 8.2p1 and thus it can no longer be abused disconnect idle users. The two options ClientAliveInterval and ClientAliveCountMax control the timeout of SSH sessions. Taken directly from man 5 sshd_config: • ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. • ClientAliveCountMax Sets the number of client alive messages which may be sent without sshd(8) receiving any messages back from the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of client alive messages is very different from TCPKeepAlive. The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option en‐abled by TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become unresponsive. The default value is 3. If ClientAliveInterval is set to 15, and ClientAliveCountMax is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds. Setting a zero ClientAliveCountMax disables connection termination. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: In order to prevent resource exhaustion, appropriate values should be set for both ClientAliveInterval and ClientAliveCountMax. Specifically, looking at the source code, ClientAliveCountMax must be greater than zero in order to utilize the ability of Page 539 Internal Only - General SSH to drop idle connections. If connections are allowed to stay open indefinitely, this can potentially be used as a DDOS attack or simple resource exhaustion could occur over unreliable networks. The example set here is a 45 second timeout. Consult your site policy for network timeouts and apply as appropriate. Audit: Run the following command and verify ClientAliveInterval and ClientAliveCountMax are greater than zero: # sshd -T | grep -Pi -- '(clientaliveinterval|clientalivecountmax)' Example Output: clientaliveinterval 15 clientalivecountmax 3 - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '(clientaliveinterval|clientalivecountmax)' Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain). Remediation: Edit the /etc/ssh/sshd_config file to set the ClientAliveInterval and ClientAliveCountMax parameters above any Include and Match entries according to site policy. Example: ClientAliveInterval 15 ClientAliveCountMax 3 Default Value: ClientAliveInterval 0 ClientAliveCountMax 3 References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 540 Internal Only - General Additional Information: https://bugzilla.redhat.com/show_bug.cgi?id=1873547 https://github.com/openssh/openssh-portable/blob/V_8_9/serverloop.c#L137 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 541 Internal Only - General 5.1.8 Ensure sshd DisableForwarding is enabled (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The DisableForwarding parameter disables all forwarding features, including X11, ssh-agent(1), TCP and StreamLocal. This option overrides all other forwarding-related options and may simplify restricted configurations. • X11Forwarding provides the ability to tunnel X11 traffic through the connection to enable remote graphic connections. • ssh-agent is a program to hold private keys used for public key authentication. Through use of environment variables the agent can be located and automatically used for authentication when logging in to other machines using ssh. • SSH port forwarding is a mechanism in SSH for tunneling application ports from the client to the server, or servers to clients. It can be used for adding encryption to legacy applications, going through firewalls, and some system administrators and IT professionals use it for opening backdoors into the internal network from their home machines. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Disable X11 forwarding unless there is an operational requirement to use X11 applications directly. There is a small risk that the remote X11 servers of users who are logged in via SSH with X11 forwarding could be compromised by other users on the X11 server. Note that even if X11 forwarding is disabled, users can always install their own forwarders. anyone with root privilege on the the intermediate server can make free use of ssh- agent to authenticate them to other servers Leaving port forwarding enabled can expose the organization to security risks and backdoors. SSH connections are protected with strong encryption. This makes their contents invisible to most deployed network monitoring and traffic filtering solutions. This invisibility carries considerable risk potential if it is used for malicious purposes such as data exfiltration. Cybercriminals or malware could exploit SSH to hide their unauthorized communications, or to exfiltrate stolen data from the target network. Page 542 Internal Only - General Impact: SSH tunnels are widely used in many corporate environments. In some environments the applications themselves may have very limited native support for security. By utilizing tunneling, compliance with SOX, HIPAA, PCI-DSS, and other standards can be achieved without having to modify the applications. Audit: Run the following command to verify DisableForwarding is set to yes: # sshd -T | grep disableforwarding disableforwarding yes Remediation: Edit the /etc/ssh/sshd_config file to set the DisableForwarding parameter to yes above any Include entry as follows: DisableForwarding yes References: 1. sshd_config(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 543 Internal Only - General 5.1.9 Ensure sshd GSSAPIAuthentication is disabled (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The GSSAPIAuthentication parameter specifies whether user authentication based on GSSAPI is allowed More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, and should be disabled to reduce the attack surface of the system Impact: Disabling GSSAPI authentication in environments that rely on centralized authentication could disrupt legitimate access. Audit: Run the following command to verify GSSAPIAuthentication is set to no: # sshd -T | grep gssapiauthentication gssapiauthentication no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep gssapiauthentication Remediation: Edit the /etc/ssh/sshd_config file to set the GSSAPIAuthentication parameter to no above any Include and Match entries as follows: GSSAPIAuthentication no Default Value: GSSAPIAuthentication no References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 544 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 545 Internal Only - General 5.1.10 Ensure sshd HostbasedAuthentication is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The HostbasedAuthentication parameter specifies if authentication is allowed through trusted hosts via the user of .rhosts, or /etc/hosts.equiv, along with successful public key client host authentication. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Even though the .rhosts files are ineffective if support is disabled in /etc/pam.conf, disabling the ability to use .rhosts files in SSH provides an additional layer of protection. Audit: Run the following command to verify HostbasedAuthentication is set to no: # sshd -T | grep hostbasedauthentication hostbasedauthentication no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep hostbasedauthentication Remediation: Edit the /etc/ssh/sshd_config file to set the HostbasedAuthentication parameter to no above any Include and Match entries as follows: HostbasedAuthentication no Default Value: HostbasedAuthentication no References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 546 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 547 Internal Only - General 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The IgnoreRhosts parameter specifies that .rhosts and .shosts files will not be used in RhostsRSAAuthentication or HostbasedAuthentication. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Setting this parameter forces users to enter a password when authenticating with SSH. Audit: Run the following command to verify IgnoreRhosts is set to yes: # sshd -T | grep ignorerhosts ignorerhosts yes Remediation: Edit the /etc/ssh/sshd_config file to set the IgnoreRhosts parameter to yes above any Include entry as follows: IgnoreRhosts yes Default Value: IgnoreRhosts yes References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 548 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 549 Internal Only - General 5.1.12 Ensure sshd KexAlgorithms is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Key exchange is any method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Key exchange methods that are considered weak should be removed. A key exchange method may be weak because too few bits are used, or the hashing algorithm is considered too weak. Using weak algorithms could expose connections to man-in-the- middle attacks Audit: Run the following command to verify none of the "weak" Key Exchange algorithms are being used: # sshd -T | grep -Pi -- 'kexalgorithms\h+([^#\n\r]+,)?(diffie-hellman-group1- sha1|diffie-hellman-group14-sha1|diffie-hellman-group-exchange-sha1)\b' Nothing should be returned. Note: If anything is returned, review the list of Key Exchange Algorithms. The following are considered "weak" Key Exchange Algorithms, and should not be used: diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group-exchange-sha1 Remediation: Edit the /etc/ssh/sshd_config file and add/modify the KexAlgorithms line to contain a comma separated list of the site unapproved (weak) KexAlgorithms preceded with a - above any Include entries: Example: KexAlgorithms -diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie- hellman-group-exchange-sha1 Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Page 550 Internal Only - General Default Value: Version 9.0 - 9.8: KexAlgorithms sntrup761x25519-sha512,sntrup761x25519- sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,ecdh- sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 Version 9.9 and greater: KexAlgorithms mlkem768x25519-sha256,sntrup761x25519- sha512,sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519- sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 References: 1. https://ubuntu.com/server/docs/openssh-crypto-configuration 2. NIST SP 800-53 Rev. 5: SC-8 3. SSHD(8) 4. SSHD_CONFIG(5) Additional Information: The supported algorithms are: diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group14-sha256 diffie-hellman-group16-sha512 diffie-hellman-group18-sha512 diffie-hellman-group-exchange-sha1 diffie-hellman-group-exchange-sha256 ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 curve25519-sha256 curve25519-sha256@libssh.org sntrup761x25519-sha512 sntrup761x25519-sha512@openssh.com mlkem768x25519-sha256 # Only supported by version 9.9 and greater CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 551 Internal Only - General 5.1.13 Ensure sshd post-quantum cryptography key exchange algorithms are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: OpenSSH has integrated post-quantum cryptography (PQC) to secure SSH connections against potential attacks from future quantum computers. This includes the adoption of hybrid key agreement algorithms that combine classical cryptographic methods with quantum-resistant ones. Rationale: PQC helps secure SSH connections against potential attacks from future quantum computers providing protection against both classical and quantum adversaries. The combination of established classical algorithms with the forward-looking security of PQC algorithms, offers a robust solution during the transition phase to fully quantum- resistant cryptography. Impact: A restrictive list of key exchange algorithms available to the SSH server may prevent some clients from being able to connect. Including a non-supported key exchange algorithm in the kexalgorithms option, may prevent the SSH server from starting. Note: The list of supported key exchange algorithms may also be obtained using the ssh -Q KexAlgorithms command. Page 552 Internal Only - General Audit: 1. Run the following command to determine the version of openSSH-server: # "$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" -V 2>&1 | \ grep -Psio 'openssh_\d+\.\d+' | awk -F'_' '{print $2}' 2. Verify post-quantum cryptography kexalgorithm(s) are available: Run the following command to verify the sntrup761x25519-sha512 post-quantum key agreement algorithm is available: # "$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" -T | \ awk '($1=="kexalgorithms" && $2~/sntrup761x25519-sha512/) {print $2}' Verify output includes sntrup761x25519-sha512 - IF - openSSH-server version is 9.9 or greater, run the following command to verify the mlkem768x25519-sha256 post-quantum key agreement algorithm is also available: # "$(readlink -e /usr/sbin/sshd || readlink -e /sbin/sshd)" -T | \ awk '($1=="kexalgorithms" && $2~/mlkem768x25519-sha256/) {print $2}' Verify output includes mlkem768x25519-sha256 Remediation: Edit the /etc/ssh/sshd_config file and add/modify the KexAlgorithms line above any Include and Match statements. Example: KexAlgorithms -diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie- hellman-group-exchange-sha1 Note: • First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. • If local site policy has stricter requirements, add any additional MACs that are not authorized by local site policy to the list in the example. Default Value: Version 9.0 - 9.8: kexalgorithms sntrup761x25519-sha512,sntrup761x25519- sha512@openssh.com,curve25519-sha256,curve25519-sha256@libssh.org,ecdh- sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 Version 9.9 and greater: kexalgorithms mlkem768x25519-sha256,sntrup761x25519- sha512,sntrup761x25519-sha512@openssh.com,curve25519-sha256,curve25519- sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521 Page 553 Internal Only - General Additional Information: OpenSSH 9.0: Introduced sntrup761x25519-sha512 as the first post-quantum key agreement algorithm, which is a hybrid scheme combining Streamlined NTRU Prime with X25519. OpenSSH 9.9: Added mlkem768x25519-sha256 as another hybrid post-quantum key agreement algorithm. OpenSSH 10.0: Made mlkem768x25519-sha256 the default key agreement algorithm. This algorithm combines ML-KEM (a NIST-standardized key encapsulation mechanism, also known as Kyber) with the classical X25519 elliptic curve method. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 554 Internal Only - General 5.1.14 Ensure sshd LoginGraceTime is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The LoginGraceTime parameter specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated connections can exist. Like other session controls in this session the Grace Period should be limited to appropriate organizational limits to ensure the service is available for needed access. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Setting the LoginGraceTime parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. It will also limit the number of concurrent unauthenticated connections While the recommended setting is 60 seconds (1 Minute), set the number based on site policy. Audit: Run the following command and verify that output LoginGraceTime is between 1 and 60 seconds: # sshd -T | grep logingracetime logingracetime 60 Remediation: Edit the /etc/ssh/sshd_config file to set the LoginGraceTime parameter to 60 seconds or less above any Include entry as follows: LoginGraceTime 60 Default Value: LoginGraceTime 120 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-6 3. SSHD(8) Page 555 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 556 Internal Only - General 5.1.15 Ensure sshd LogLevel is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: SSH provides several logging levels with varying amounts of verbosity. The DEBUG options are specifically not recommended other than strictly for debugging SSH communications. These levels provide so much data that it is difficult to identify important security information, and may violate the privacy of users. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: The INFO level is the basic level that only records login activity of SSH users. In many situations, such as Incident Response, it is important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field. The VERBOSE level specifies that login and logout activity as well as the key fingerprint for any SSH key used for login will be logged. This information is important for SSH key management, especially in legacy environments. Audit: Run the following command and verify that output matches loglevel VERBOSE or loglevel INFO: # sshd -T | grep loglevel loglevel VERBOSE - OR - loglevel INFO - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep loglevel Page 557 Internal Only - General Remediation: Edit the /etc/ssh/sshd_config file to set the LogLevel parameter to VERBOSE or INFO above any Include and Match entries as follows: LogLevel VERBOSE - OR - LogLevel INFO Default Value: LogLevel INFO References: 1. https://www.ssh.com/ssh/sshd_config/ 2. NIST SP 800-53 Rev. 5: AU-3, AU-12, SI-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 558 Internal Only - General 5.1.16 Ensure sshd MACs are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: This variable limits the types of MAC algorithms that SSH can use during communication. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: MD5 and 96-bit MAC algorithms are considered weak and have been shown to increase exploitability in SSH downgrade attacks. Weak algorithms continue to have a great deal of attention as a weak spot that can be exploited with expanded computing power. An attacker that breaks the algorithm could take advantage of a MiTM position to decrypt the SSH tunnel and capture credentials and information. Impact: Incorrectly configured or an overly restrictive list of MACs could lead to a "no matching MAC" error during an SSH connection. This means the client and server have no overlapping MAC algorithms which typically occurs due to a mismatch in supported MACs. Page 559 Internal Only - General Audit: Run the following command to verify none of the "weak" MACs are being used: # sshd -T | grep -Pi -- 'macs\h+([^#\n\r]+,)?(hmac-md5|hmac-md5-96|hmac- ripemd160|hmac-sha1-96|umac-64@openssh\.com|hmac-md5-etm@openssh\.com|hmac- md5-96-etm@openssh\.com|hmac-ripemd160-etm@openssh\.com|hmac-sha1-96- etm@openssh\.com|umac-64-etm@openssh\.com|umac-128-etm@openssh\.com)\b' Nothing should be returned Note: Review CVE-2023-48795 and verify the system has been patched. If the system has not been patched, review the use of the Encrypt Then Mac (etm) MACs. The following are considered "weak" MACs, and should not be used: hmac-md5 hmac-md5-96 hmac-ripemd160 hmac-sha1-96 umac-64@openssh.com hmac-md5-etm@openssh.com hmac-md5-96-etm@openssh.com hmac-ripemd160-etm@openssh.com hmac-sha1-96-etm@openssh.com umac-64-etm@openssh.com umac-128-etm@openssh.com Remediation: Edit the /etc/ssh/sshd_config file and add/modify the MACs line to contain a comma separated list of the site unapproved (weak) MACs preceded with a - above any Include entries: Example: MACs -hmac-md5,hmac-md5-96,hmac-ripemd160,hmac-sha1-96,umac- 64@openssh.com,hmac-md5-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac- ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,umac-64- etm@openssh.com,umac-128-etm@openssh.com - IF - CVE-2023-48795 has not been reviewed and addressed, the following etm MACs should be added to the exclude list: hmac-sha1-etm@openssh.com,hmac-sha2-256- etm@openssh.com,hmac-sha2-512-etm@openssh.com Default Value: MACs umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256- etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1- etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2- 256,hmac-sha2-512,hmac-sha1 References: 1. https://nvd.nist.gov/vuln/detail/CVE-2023-48795 2. More information on SSH downgrade attacks can be found here: http://www.mitls.org/pages/attacks/SLOTH 3. SSHD_CONFIG(5) 4. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 560 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. 16.5 Encrypt Transmittal of Username and v7 Authentication Credentials ● ● Ensure that all account usernames and authentication credentials are transmitted across networks using encrypted channels. Page 561 Internal Only - General 5.1.17 Ensure sshd MaxAuthTries is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxAuthTries parameter specifies the maximum number of authentication attempts permitted per connection. When the login failure count reaches half the number, error messages will be written to the syslog file detailing the login failure. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Setting the MaxAuthTries parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. While the recommended setting is 4, set the number based on site policy. Audit: Run the following command and verify that MaxAuthTries is 4 or less: # sshd -T | grep maxauthtries maxauthtries 4 - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep maxauthtries Remediation: Edit the /etc/ssh/sshd_config file to set the MaxAuthTries parameter to 4 or less above any Include and Match entries as follows: MaxAuthTries 4 Default Value: MaxAuthTries 6 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: AU-3 Page 562 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 563 Internal Only - General 5.1.18 Ensure sshd MaxSessions is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxSessions parameter specifies the maximum number of open sessions permitted from a given connection. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions to protect availability of sshd logins and prevent overwhelming the daemon. Audit: Run the following command and verify that MaxSessions is 10 or less: # sshd -T | grep maxsessions maxsessions 10 Run the following command and verify the output: grep -Psi -- '^\h*MaxSessions\h+\"?(1[1-9]|[2-9][0-9]|[1-9][0-9][0-9]+)\b' /etc/ssh/sshd_config /etc/ssh/sshd_config.d/*.conf Nothing should be returned - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep maxsessions Remediation: Edit the /etc/ssh/sshd_config file to set the MaxSessions parameter to 10 or less above any Include and Match entries as follows: MaxSessions 10 Default Value: MaxSessions 10 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 564 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 565 Internal Only - General 5.1.19 Ensure sshd MaxStartups is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: To protect a system from denial of service due to a large number of pending authentication connection attempts, use the rate limiting function of MaxStartups to protect availability of sshd logins and prevent overwhelming the daemon. Audit: Run the following command to verify MaxStartups is 10:30:60 or more restrictive: # sshd -T | awk '$1 ~ /^\s*maxstartups/{split($2, a, ":");{if(a[1] > 10 || a[2] > 30 || a[3] > 60) print $0}}' Nothing should be returned Remediation: Edit the /etc/ssh/sshd_config file to set the MaxStartups parameter to 10:30:60 or more restrictive above any Include entries as follows: MaxStartups 10:30:60 Default Value: MaxStartups 10:30:100 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 566 Internal Only - General 5.1.20 Ensure sshd PermitEmptyPasswords is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitEmptyPasswords parameter specifies if the SSH server allows login to accounts with empty password strings. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Disallowing remote shell access to accounts that have an empty password reduces the probability of unauthorized access to the system. Audit: Run the following command to verify PermitEmptyPasswords is set to no: # sshd -T | grep permitemptypasswords permitemptypasswords no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep permitemptypasswords Remediation: Edit /etc/ssh/sshd_config and set the PermitEmptyPasswords parameter to no above any Include and Match entries as follows: PermitEmptyPasswords no Default Value: PermitEmptyPasswords no References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 567 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 568 Internal Only - General 5.1.21 Ensure sshd PermitRootLogin is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitRootLogin parameter specifies if the root user can log in using SSH. The default is prohibit-password. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Disallowing root logins over SSH requires system admins to authenticate using their own individual account, then escalating to root. This limits opportunity for non- repudiation and provides a clear audit trail in the event of a security incident. Audit: Run the following command to verify PermitRootLogin is set to no: # sshd -T | grep permitrootlogin permitrootlogin no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep permitrootlogin Remediation: Edit the /etc/ssh/sshd_config file to set the PermitRootLogin parameter to no above any Include and Match entries as follows: PermitRootLogin no Default Value: PermitRootLogin without-password References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5:AC-6 Page 569 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 570 Internal Only - General 5.1.22 Ensure sshd PermitUserEnvironment is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitUserEnvironment option allows users to present environment options to the SSH daemon. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: Permitting users the ability to set environment variables through the SSH daemon could potentially allow users to bypass security controls (e.g. setting an execution path that has SSH executing trojan'd programs) Audit: Run the following command to verify PermitUserEnvironment is set to no: # sshd -T | grep permituserenvironment permituserenvironment no Remediation: Edit the /etc/ssh/sshd_config file to set the PermitUserEnvironment parameter to no above any Include entries as follows: PermitUserEnvironment no Default Value: PermitUserEnvironment no References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 3. SSHD(8) Page 571 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 572 Internal Only - General 5.1.23 Ensure sshd UsePAM is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The UsePAM directive enables the Pluggable Authentication Module (PAM) interface. If set to yes this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication directives in addition to PAM account and session module processing for all authentication types. More information about the openSSH server configuration is available in the "Configure SSH Server" section overview. Rationale: When usePAM is set to yes, PAM runs through account and session types properly. This is important if you want to restrict access to services based off of IP, time or other factors of the account. Additionally, you can make sure users inherit certain environment variables on login or disallow access to the server Audit: Run the following command to verify UsePAM is set to yes: # sshd -T | grep usepam usepam yes Remediation: Edit the /etc/ssh/sshd_config file to set the UsePAM parameter to yes above any Include entries as follows: UsePAM yes Default Value: UsePAM yes References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 3. SSHD(8) Page 573 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 574 Internal Only - General 5.2 Configure privilege escalation There are various tools which allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. sudo sudo documentation The invoking user's real (not effective) user ID is used to determine the user name with which to query the security policy. sudo supports a plug-in architecture for security policies and input/output logging. Third parties can develop and distribute their own policy and I/O logging plug-ins to work seamlessly with the sudo front end. The default security policy is sudoers, which is configured via the file /etc/sudoers and any entries in /etc/sudoers.d. pkexec pkexec documentation pkexec allows an authorized user to execute PROGRAM as another user. If username is not specified, then the program will be executed as the administrative super user, root. Page 575 Internal Only - General 5.2.1 Ensure sudo is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user ID is used to determine the user name with which to query the security policy. Rationale: sudo supports a plug-in architecture for security policies and input/output logging. Third parties can develop and distribute their own policy and I/O logging plug-ins to work seamlessly with the sudo front end. The default security policy is sudoers, which is configured via the file /etc/sudoers and any entries in /etc/sudoers.d. The security policy determines what privileges, if any, a user has to run sudo. The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, sudo will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific. Audit: Run the following command to verify that either sudo or sudo-ldap is installed: # dpkg-query -l | awk '{print $2}' | grep -Pio -- '^sudo|^sudo-ldap' &>/dev/null && echo "sudo is installed" sudo is installed - OR - Run the following to verify that libsss-sudo and sssd is installed: # dpkg-query -s libsss-sudo &>/dev/null && echo "libsss-sudo is installed" libsss-sudo is installed # dpkg-query -s sssd &>/dev/null && echo "sssd is installed" sssd is installed Page 576 Internal Only - General Remediation: First determine is LDAP functionality is required. If so, then install libsss-sudo and sssd. Example: # apt install libsss-sudo sssd Note: Debian 13, "trixie", will be the last version of Debian that supports sudo-ldap. The Debian sudo team recommends the use of libsss-sudo for new installations and the migration of existing installations from sudo-ldap to libsss-sudo and sssd. See /usr/share/doc/sudo-ldap/NEWS.Debian.gz for more explanation. This is also being discussed in #1033728 in the Debian BTS. References: 1. SUDO(8) 2. NIST SP 800-53 Rev. 5: AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 577 Internal Only - General 5.2.2 Ensure sudo commands use pty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo can be configured to run only from a pseudo terminal (pseudo-pty). Rationale: Attackers can run a malicious program using sudo which would fork a background process that remains even when the main program has finished executing. Impact: WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files. Audit: Verify that sudo can only run other commands from a pseudo terminal. Run the following command to verify Defaults use_pty is set: # grep -rPi -- '^\h*Defaults\h+([^#\n\r]+,\h*)?use_pty\b' /etc/sudoers* Verify the output matches: /etc/sudoers:Defaults use_pty Run the follow command to to verify Defaults !use_pty is not set: # grep -rPi -- '^\h*Defaults\h+([^#\n\r]+,\h*)?!use_pty\b' /etc/sudoers* Nothing should be returned Remediation: Edit the file /etc/sudoers with visudo or a file in /etc/sudoers.d/ with visudo -f and add the following line: Defaults use_pty Edit the file /etc/sudoers with visudo and any files in /etc/sudoers.d/ with visudo -f and remove any occurrence of !use_pty Page 578 Internal Only - General Note: • sudo will read each file in /etc/sudoers.d, skipping file names that end in ~ or contain a . character to avoid causing problems with package manager or editor temporary/backup files. • Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second. • Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second. • Using a consistent number of leading zeroes in the file names can be used to avoid such problems. References: 1. SUDO(8) 2. VISUDO(8) 3. sudoers(5) 4. NIST SP 800-53 Rev. 5: AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 579 Internal Only - General 5.2.3 Ensure sudo log file exists (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo can use a custom log file Rationale: A sudo log file simplifies auditing of sudo commands Impact: WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files. Audit: Run the following command to verify that sudo has a custom log file configured: # grep -rPsi "^\h*Defaults\h+([^#]+,\h*)?logfile\h*=\h*(\"|\')?\H+(\"|\')?(,\h*\H+\h*)*\h* (#.*)?$" /etc/sudoers* Verify the output matches: Defaults logfile="/var/log/sudo.log" Remediation: Edit the file /etc/sudoers or a file in /etc/sudoers.d/ with visudo -f and add the following line: Defaults logfile="" Example: Defaults logfile="/var/log/sudo.log" Notes: • sudo will read each file in /etc/sudoers.d, skipping file names that end in ~ or contain a . character to avoid causing problems with package manager or editor temporary/backup files. • Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second. • Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second. • Using a consistent number of leading zeroes in the file names can be used to avoid such problems. Page 580 Internal Only - General References: 1. SUDO(8) 2. VISUDO(8) 3. sudoers(5) 4. NIST SP 800-53 Rev. 5: AU-3, AU-12 Additional Information: visudo edits the sudoers file in a safe fashion, analogous to vipw(8). visudo locks the sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks for parse errors. If the sudoers file is currently being edited you will receive a message to try again later. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 581 Internal Only - General 5.2.4 Ensure users must provide password for escalation (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must be configured so that users must provide a password for privilege escalation. Rationale: Without (re-)authentication, users may access resources or perform tasks for which they do not have authorization. When operating systems provide the capability to escalate a functional capability, it is critical the user (re-)authenticate. Impact: This will prevent automated processes from being able to elevate privileges. Audit: Note: If passwords are not being used for authentication, this is not applicable. Verify the operating system requires users to supply a password for privilege escalation. Check the configuration of the /etc/sudoers and /etc/sudoers.d/* files with the following command: # grep -r "^[^#].*NOPASSWD" /etc/sudoers* If any line is found refer to the remediation procedure below. Remediation: Based on the outcome of the audit procedure, use visudo -f to edit the relevant sudoers file. Remove any line with occurrences of NOPASSWD tags in the file. References: 1. NIST SP 800-53 Rev. 5: AC-6 Page 582 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 583 Internal Only - General 5.2.5 Ensure re-authentication for privilege escalation is not disabled globally (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The operating system must be configured so that users must re-authenticate for privilege escalation. Rationale: Without re-authentication, users may access resources or perform tasks for which they do not have authorization. When operating systems provide the capability to escalate a functional capability, it is critical the user re-authenticate. Audit: Verify the operating system requires users to re-authenticate for privilege escalation. Check the configuration of the /etc/sudoers and /etc/sudoers.d/* files with the following command: # grep -r '^[^#].*\!authenticate' /etc/sudoers* If any line is found with a !authenticate tag, refer to the remediation procedure below. Remediation: Configure the operating system to require users to reauthenticate for privilege escalation. Based on the outcome of the audit procedure, use visudo -f to edit the relevant sudoers file. Remove any occurrences of !authenticate tags in the file(s). References: 1. NIST SP 800-53 Rev. 5: AC-6 Page 584 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 585 Internal Only - General 5.2.6 Ensure sudo timestamp_timeout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo timestamp_timeout controls how long a user's sudo privileges remain active after the initial password entry. Rationale: A timeout value reduces the window of opportunity for unauthorized privileged sudo access. Audit: Ensure that the caching timeout is not disabled and greater than 15 minutes. Run the following command: # grep -roP "timestamp_timeout=\K[0-9]*" /etc/sudoers* If there is no timestamp_timeout configured in /etc/sudoers* then the default of 5 minutes is being used. If the default value is being used, run the following command to verify the default is not disabled or greater than 15 minutes: # sudo -V | grep -Psi -- 'timestamp\h+timeout\b' Example output: Authentication timestamp timeout: 15.0 minutes Verify Authentication timestamp timeout: • Is not a negative number (disabled). • Is not greater than 15 minutes, and follows local site policy. • Follows local site policy Remediation: Edit the file listed in the audit section with visudo -f and modify the entry timestamp_timeout= to 15 minutes or less as per your site policy. The value is in minutes. This particular entry may appear on its own, or on the same line as env_reset. See the following two examples: Example 1: Defaults env_reset, timestamp_timeout=15 Example 2: Defaults timestamp_timeout=15 Defaults env_reset Page 586 Internal Only - General Default Value: timestamp_timeout=15 References: 1. https://www.sudo.ws/man/1.9.0/sudoers.man.html 2. NIST SP 800-53 Rev. 5: AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 587 Internal Only - General 5.2.7 Ensure access to the su command is restricted (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The su command allows a user to run a command or shell as another user. The program has been superseded by sudo, which allows for more granular control over privileged access. Normally, the su command can be executed by any user. By uncommenting the pam_wheel.so statement in /etc/pam.d/su, the su command will only allow users in a specific groups to execute su. This group should be empty to reinforce the use of sudo for privileged access. Rationale: Restricting the use of su , and using sudo in its place, provides system administrators better control of the escalation of user privileges to execute privileged commands. The sudo utility also provides a better logging and audit mechanism, as it can log each command executed via sudo , whereas su can only record that a user executed the su program. Audit: Run the following command: # grep -Pi '^\h*auth\h+(?:required|requisite)\h+pam_wheel\.so\h+(?:[^#\n\r]+\h+)?((?!\2) (use_uid\b|group=\H+\b))\h+(?:[^#\n\r]+\h+)?((?!\1)(use_uid\b|group=\H+\b))(\ h+.*)?$' /etc/pam.d/su Verify the output matches: auth required pam_wheel.so use_uid group= Run the following command and verify that the group specified in contains no users: # grep /etc/group Verify the output does not contain any users in the relevant group: :x:: Remediation: Create an empty group that will be specified for use of the su command. The group should be named according to site policy. Example: # groupadd sugroup Add the following line to the /etc/pam.d/su file, specifying the empty group: auth required pam_wheel.so use_uid group=sugroup Page 588 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 589 Internal Only - General 5.3 Pluggable Authentication Modules Pluggable Authentication Modules (PAM) is a service that implements modular authentication modules on Linux systems. PAM is implemented as a set of shared objects that are loaded and executed when a program needs to authenticate a user. Files for PAM are typically located in the /etc/pam.d directory. PAM must be carefully configured to secure system authentication. While this section covers some of PAM, please consult other PAM resources to fully understand the configuration capabilities. Note: This section includes guidance that requires the additional modules and the latest version of software packages as covered in the "Configure required security packages" subsection of the "Package Management" section Page 590 Internal Only - General 5.3.1 Configure PAM software packages Updated versions of PAM include additional functionality Page 591 Internal Only - General 5.3.1.1 Ensure latest version of pam is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Linux Pluggable Authentication Modules (PAM) is a suite of libraries that allow a Linux system administrator to configure methods to authenticate users. It provides a flexible and centralized way to switch authentication methods for secured applications by using configuration files instead of changing application code The libpam-runtime provides the runtime support for the PAM library Rationale: Older versions of the libpam-runtime package may not include the latest security and feature patches and updates. Note: This Benchmark includes Recommendations that depend on newer libpam- runtime features. Audit: Run the following command to verify libpam-runtime is installed: # dpkg-query -s libpam-runtime &>/dev/null && echo "libpam-runtime is installed" libpam-runtime is installed Run the following command to verify libpam-runtime is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-runtime\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-runtime: # apt install libpam-runtime References: 1. PAM(7) CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 592 Internal Only - General 5.3.1.2 Ensure latest version of libpam-modules is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: libpam-modules is a package containing a set of Pluggable Authentication Modules (PAM) which allows system administrators to configure different authentication methods for user logins, providing flexibility in how users can access applications by using various authentication modules to include password checks and other security mechanisms. Rationale: Older versions of the libpam-modules package may not include the latest security and feature patches and updates. Note: This Benchmark includes Recommendations that depend on newer libpam- modules features. Audit: Run the following command to verify libpam-modules is installed: # dpkg-query -s libpam-modules &>/dev/null && echo "libpam-modules is installed" libpam-modules is installed Run the following command to verify libpam-modules is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-modules\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-modules: # apt install libpam-modules CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 593 Internal Only - General 5.3.1.3 Ensure latest version of libpam-pwquality is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: libpwquality provides common functions for password quality checking and scoring them based on their apparent randomness. The library also provides a function for generating random passwords with good pronounceability. This module can be plugged into the password stack of a given service to provide some plug-in strength-checking for passwords. The code was originally based on pam_cracklib module and the module is backwards compatible with its options. Rationale: Strong passwords reduce the risk of systems being hacked through brute force methods. Older versions of the libpam-pwquality package may not include the latest security and feature patches and updates. Audit: Run the following command to verify libpam-pwquality is installed: # dpkg-query -s libpam-pwquality &>/dev/null && echo "libpam-pwquality is installed" libpam-pwquality is installed Run the following command to verify libpam-pwquality is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-pwquality\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-pwquality: # apt install libpam-pwquality References: 1. https://packages.debian.org/buster/libpam-pwquality Page 594 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 595 Internal Only - General 5.3.2 Configure pam-auth-update profiles pam-auth-update is a utility that permits configuring the central authentication policy for the system using pre-defined profiles as supplied by PAM module packages. Profiles - Shipped in the /usr/share/pam-configs/ directory specify the modules, with options, to enable; the preferred ordering with respect to other profiles; and whether a profile should be enabled by default. Packages providing PAM modules register their profiles at install time by calling pam-auth-update --package. Selection of profiles is done using the standard debconf interface. The profile selection question will be asked at medium priority when packages are added or removed, so no user interaction is required by default. Users may invoke pam-auth-update directly to change their authentication configuration. The pam-auth-update script makes every effort to respect local changes to /etc/pam.d/common-*. Local modifications to the list of module options will be preserved, and additions of modules within the managed portion of the stack will cause pam-auth-update to treat the config files as locally modified and not make further changes to the config files unless given the --force option. If the user specifies that pam-auth-update should override local configuration changes, the locally-modified files will be saved in /etc/pam.d/ with a suffix of .pam-old. Page 596 Internal Only - General 5.3.2.1 Ensure pam_unix module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: pam_unix is the standard Unix authentication module. It uses standard calls from the system's libraries to retrieve and set account information as well as authentication. Usually this is obtained from the /etc/passwd and if shadow is enabled, the /etc/shadow file as well. The account component performs the task of establishing the status of the user's account and password based on the following shadow elements: expire, last_change, max_change, min_change, warn_change. In the case of the latter, it may offer advice to the user on changing their password or, through the PAM_AUTHTOKEN_REQD return, delay giving service to the user until they have established a new password. The entries listed above are documented in the shadow(5) manual page. Should the user's record not contain one or more of these entries, the corresponding shadow check is not performed. The authentication component performs the task of checking the users credentials (password). The default action of this module is to not permit the user access to a service if their official password is blank. Rationale: The system should only provide access after performing authentication of a user. Audit: Run the following command to verify that pam_unix is enabled: # grep -PH -- '\bpam_unix\.so\b' /etc/pam.d/common- {account,auth,password,session,session-noninteractive} Output should be simular to: /etc/pam.d/common-account:account [success=1 new_authtok_reqd=done default=ignore] pam_unix.so /etc/pam.d/common-auth:auth [success=2 default=ignore] pam_unix.so try_first_pass /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt /etc/pam.d/common-session:session required pam_unix.so /etc/pam.d/common-session-noninteractive:session required pam_unix.so Page 597 Internal Only - General Remediation: Run the following command to enable the pam_unix module: # pam-auth-update --enable unix Note: If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_unix module, enable that module instead References: 1. NIST SP 800-53 Rev. 5: IA-5(1) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 598 Internal Only - General 5.3.2.2 Ensure pam_faillock module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_faillock.so module maintains a list of failed authentication attempts per user during a specified interval and locks the account in case there were more than the configured number of consecutive failed authentications (this is defined by the deny parameter in the faillock configuration). It stores the failure records into per-user files in the tally directory. Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Audit: Run the following commands to verify that pam_faillock is enabled: # grep -P -- '\bpam_faillock\.so\b' /etc/pam.d/common-{auth,account} Output should be similar to: /etc/pam.d/common-auth:auth requisite pam_faillock.so preauth /etc/pam.d/common-auth:auth [default=die] pam_faillock.so authfail /etc/pam.d/common-account:account required pam_faillock.so Page 599 Internal Only - General Remediation: Create two pam-auth-update profiles in /usr/share/pam-configs/: 1. Create the faillock profile in /usr/share/pam-configs/ with the following lines: Name: Enable pam_faillock to deny access Default: yes Priority: 0 Auth-Type: Primary Auth: [default=die] pam_faillock.so authfail Example Script: #!/usr/bin/env bash { arr=('Name: Enable pam_faillock to deny access' 'Default: yes' 'Priority: 0' 'Auth-Type: Primary' 'Auth:' ' [default=die] pam_faillock.so authfail') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/faillock } 2. Create the faillock_notify profile in /usr/share/pam-configs/ with the following lines: Name: Notify of failed login attempts and reset count upon success Default: yes Priority: 1024 Auth-Type: Primary Auth: requisite pam_faillock.so preauth Account-Type: Primary Account: required pam_faillock.so Example Script: #!/usr/bin/env bash { arr=('Name: Notify of failed login attempts and reset count upon success' 'Default: yes' 'Priority: 1024' 'Auth-Type: Primary' 'Auth:' ' requisite pam_faillock.so preauth' 'Account-Type: Primary' 'Account:' ' required pam_faillock.so') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/faillock_notify } Run the following command to update the common-auth and common-account PAM files with the new profiles: # pam-auth-update --enable Example: # pam-auth-update --enable faillock # pam-auth-update --enable faillock_notify Page 600 Internal Only - General Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_faillock module, enable that module instead CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 601 Internal Only - General 5.3.2.3 Ensure pam_pwquality module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwquality.so module performs password quality checking. This module can be plugged into the password stack of a given service to provide strength-checking for passwords. The code was originally based on pam_cracklib module and the module is backwards compatible with its options. The action of this module is to prompt the user for a password and check its strength against a system dictionary and a set of rules for identifying poor choices. The first action is to prompt for a single password, check its strength and then, if it is considered strong, prompt for the password a second time (to verify that it was typed correctly on the first occasion). All being well, the password is passed on to subsequent modules to be installed as the new authentication token. Rationale: Use of a unique, complex passwords helps to increase the time and resources required to compromise the password. Audit: Run the following command to verify that pam_pwquality.so is enabled: # grep -P -- '\bpam_pwquality\.so\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwquality.so retry=3 Page 602 Internal Only - General Remediation: Run the following script to verify the pam_pwquality.so line exists in a pam-auth- update profile: # grep -P -- '\bpam_pwquality\.so\b' /usr/share/pam-configs/* Output should be similar to: /usr/share/pam-configs/pwquality: requisite pam_pwquality.so retry=3 /usr/share/pam-configs/pwquality: requisite pam_pwquality.so retry=3 - IF - similar output is returned: Run the following command to update /etc/pam.d/common-password with the returned profile: # pam-auth-update --enable {PROFILE_NAME} Example: # pam-auth-update pwquality - IF - similar output is NOT returned: Create a pam-auth-update profile in /usr/share/pam-configs/ with the following lines: Name: Pwquality password strength checking Default: yes Priority: 1024 Conflicts: cracklib Password-Type: Primary Password: requisite pam_pwquality.so retry=3 Example: #!/usr/bin/env bash { arr=('Name: Pwquality password strength checking' 'Default: yes' 'Priority: 1024' 'Conflicts: cracklib' 'Password-Type: Primary' 'Password:' ' requisite pam_pwquality.so retry=3') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/pwquality } Run the following command to update /etc/pam.d/common-password with the pwquality profile: # pam-auth-update --enable pwquality Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_pwquality module, enable that module instead Page 603 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 604 Internal Only - General 5.3.2.4 Ensure pam_pwhistory module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwhistory.so module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently. This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking. Rationale: Use of a unique, complex passwords helps to increase the time and resources required to compromise the password. Audit: Run the following command to verify that pam_pwhistory.so is enabled: # grep -P -- '\bpam_pwhistory\.so\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Page 605 Internal Only - General Remediation: Run the following script to verify the pam_pwhistory.so line exists in a pam-auth- update profile: # grep -P -- '\bpam_pwhistory\.so\b' /usr/share/pam-configs/* Output should be similar to: /usr/share/pam-configs/pwhistory: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok - IF - similar output is returned: Run the following command to update /etc/pam.d/common-password with the returned profile: # pam-auth-update --enable {PROFILE_NAME} Example: # pam-auth-update pwhistory - IF - similar output is NOT returned: Create a pwhistory profile in /usr/share/pam-configs/ with the following lines: Name: pwhistory password history checking Default: yes Priority: 1024 Password-Type: Primary Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Example Script: #!/usr/bin/env bash { arr=('Name: pwhistory password history checking' 'Default: yes' 'Priority: 1024' 'Password-Type: Primary' 'Password:' ' requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/pwhistory } Run the following command to update /etc/pam.d/common-password with the pwhistory profile: # pam-auth-update --enable pwhistory Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_pwhistory module, enable that module instead Page 606 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 607 Internal Only - General 5.3.3 Configure PAM Arguments Pluggable Authentication Modules (PAM) uses arguments to pass information to a pluggable module during authentication for a particular module type. These arguments allow the PAM configuration files for particular programs to use a common PAM module but in different ways. Invalid arguments are ignored and do not otherwise affect the success or failure of the PAM module. When an invalid argument is passed, an error is usually written to /var/log/messages file. However, since the reporting method is controlled by the PAM module, the module must be written correctly to log the error to this file. Note: If custom PAM files are being used, for this section's remediation, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam- auth-update --enable command skipped Page 608 Internal Only - General 5.3.3.1 Configure pam_faillock module pam_faillock.so provides a way to configure the default settings for locking the user after multiple failed authentication attempts. Options: • - The directory where the user files with the failure records are kept. The default is /var/run/faillock. Note: These files will disappear after reboot on systems configured with directory /var/run/faillock mounted on virtual memory. • audit - Will log the user name into the system log if the user is not found. • silent - Don't print informative messages to the user. Please note that when this option is not used there will be difference in the authentication behavior for users which exist on the system and non-existing users. • no_log_info - Don't log informative messages via syslog(3). • local_users_only - Only track failed user authentications attempts for local users in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users. The faillock(8) command will also no longer track user failed authentication attempts. Enabling this option will prevent a double-lockout scenario where a user is locked out locally and in the centralized mechanism. • nodelay - Don't enforce a delay after authentication failures. • deny= - Deny access if the number of consecutive authentication failures for this user during the recent interval exceeds . The default is 3. • fail_interval=n - The length of the interval during which the consecutive authentication failures must happen for the user account lock out is n seconds. The default is 900 (15 minutes). • unlock_time=n - The access will be re-enabled after n seconds after the lock out. The value 0 has the same meaning as value never - the access will not be re-enabled without resetting the faillock entries by the faillock(8) command. The default is 600 (10 minutes). Note that the default directory that pam_faillock uses is usually cleared on system boot so the access will be also re-enabled after system reboot. If that is undesirable a different tally directory must be set with the dir option. Also note that it is usually undesirable to permanently lock out users as they can become easily a target of denial of service attack unless the usernames are random and kept secret to potential attackers. • even_deny_root - Root account can become locked as well as regular accounts. • root_unlock_time=n - This option implies even_deny_root option. Allow access after n seconds to root account after the account is locked. In case the option is not specified the value is the same as of the unlock_time option. • admin_group=name - If a group name is specified with this option, members of the group will be handled by this module the same as the root account (the options even_deny_root and root_unlock_time will apply to them. By default the option is not set. Page 609 Internal Only - General 5.3.3.1.1 Ensure password failed attempts lockout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The deny= option will deny access if the number of consecutive authentication failures for this user during the recent interval exceeds . Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Audit: Run the following command to verify that Number of failed logon attempts before the account is locked is no greater than 5 and meets local site policy: # grep -Pi -- '^\h*deny\h*=\h*[1-5]\b' /etc/security/faillock.conf deny = 5 Run the following command to verify that the deny argument has not been set, or 5 or less and meets local site policy: # grep -Pi -- '^\h*auth\h+(requisite|required|sufficient)\h+pam_faillock\.so\h+([^#\n\r]+\h +)?deny\h*=\h*(0|[6-9]|[1-9][0-9]+)\b' /etc/pam.d/common-auth Nothing should be returned Remediation: Create or edit the following line in /etc/security/faillock.conf setting the deny option to 5 or less: deny = 5 Run the following command: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?deny\b' /usr/share/pam- configs/* Edit any returned files and remove the deny= arguments from the pam_faillock.so line(s): Default Value: deny = 3 Page 610 Internal Only - General Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 611 Internal Only - General 5.3.3.1.2 Ensure password unlock time is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: unlock_time= - The access will be re-enabled after seconds after the lock out. The value 0 has the same meaning as value never - the access will not be re-enabled without resetting the faillock entries by the faillock(8) command. Note: • The default directory that pam_faillock uses is usually cleared on system boot so the access will be also re-enabled after system reboot. If that is undesirable a different tally directory must be set with the dir option. • It is usually undesirable to permanently lock out users as they can become easily a target of denial of service attack unless the usernames are random and kept secret to potential attackers. • The maximum configurable value for unlock_time is 604800 Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Impact: Use of unlock_time=0 may allow an attacker to cause denial of service to legitimate users. This will also require a systems administrator with elevated privileges to unlock the account. Audit: Run the following command to verify that the time in seconds before the account is unlocked is either 0 (never) or 900 (15 minutes) or more and meets local site policy: # grep -Pi -- '^\h*unlock_time\h*=\h*(0|9[0-9][0-9]|[1-9][0-9]{3,})\b' /etc/security/faillock.conf unlock_time = 900 Run the following command to verify that the unlock_time argument has not been set, or is either 0 (never) or 900 (15 minutes) or more and meets local site policy: # grep -Pi -- '^\h*auth\h+(requisite|required|sufficient)\h+pam_faillock\.so\h+([^#\n\r]+\h +)?unlock_time\h*=\h*([1-9]|[1-9][0-9]|[1-8][0-9][0-9])\b' /etc/pam.d/common- auth Nothing should be returned Page 612 Internal Only - General Remediation: Set password unlock time to conform to site policy. unlock_time should be 0 (never), or 900 seconds or greater. Edit /etc/security/faillock.conf and update or add the following line: unlock_time = 900 Run the following command: remove the unlock_time argument from the pam_faillock.so module in the PAM files: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?unlock_time\b' /usr/share/pam-configs/* Edit any returned files and remove the unlock_time= argument from the pam_faillock.so line(s): Default Value: unlock_time = 600 Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 613 Internal Only - General 5.3.3.1.3 Ensure password failed attempts lockout includes root account (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: even_deny_root - Enables locking of the root account, as well as regular accounts, after failed attempts. By default, root is exempt to prevent denial-of-service risks. root_unlock_time=n - This option implies even_deny_root option. Allow access after n seconds to root account after the account is locked. In case the option is not specified the value is the same as of the unlock_time option. Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigate brute force password attacks against your systems. Impact: Use of unlock_time=0 or root_unlock_time=0 may allow an attacker to cause denial of service to legitimate users. Page 614 Internal Only - General Audit: Run the following command to verify that even_deny_root and/or root_unlock_time is enabled: # grep -Pi -- '^\h*(even_deny_root|root_unlock_time\h*=\h*\d+)\b' /etc/security/faillock.conf Example output: even_deny_root --AND/OR-- root_unlock_time = 60 Run the following command to verify that - IF - root_unlock_time is set, it is set to 60 (One minute) or more: # grep -Pi -- '^\h*root_unlock_time\h*=\h*([1-9]|[1-5][0-9])\b' /etc/security/faillock.conf Nothing should be returned Run the following command to check the pam_faillock.so module for the root_unlock_time argument. Verify -IF- root_unlock_time is set, it is set to 60 (One minute) or more: # grep -Pi -- '^\h*auth\h+([^#\n\r]+\h+)pam_faillock\.so\h+([^#\n\r]+\h+)?root_unlock_time\ h*=\h*([1-9]|[1-5][0-9])\b' /etc/pam.d/common-auth Nothing should be returned Remediation: Edit /etc/security/faillock.conf: • Remove or update any line containing root_unlock_time, - OR - set it to a value of 60 or more • Update or add the following line even_deny_root Run the following command: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?(even_deny_root|root_unlock_time)' /usr/share/pam-configs/* Edit any returned files and remove the even_deny_root and root_unlock_time arguments from the pam_faillock.so line(s). Note: It is recommended to remove any duplicate or contradictory entries of even_deny_root and root_unlock_time found in /usr/share/pam-configs/ files and only use the centralized /etc/security/fallock.conf to set even_deny_root. Default Value: disabled Page 615 Internal Only - General References: 1. https://linux.die.net/man/8/pam_faillock Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 616 Internal Only - General 5.3.3.2 Configure pam_pwquality module The pam_pwquality.so module checks the strength of passwords. It performs checks such as making sure a password is not a dictionary word, it is a certain length, contains a mix of characters (e.g. alphabet, numeric, other) and more. These checks are configurable by either: • use of the module arguments • modifying the /etc/security/pwquality.conf configuration file • creating a .conf file in the /etc/security/pwquality.conf.d/ directory. Note: The module arguments override the settings in the /etc/security/pwquality.conf configuration file. Settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory. The possible options in the file are: • difok - Number of characters in the new password that must not be present in the old password. (default 1). The special value of 0 disables all checks of similarity of the new password with the old password except the new password being exactly the same as the old one. • minlen - Minimum acceptable size for the new password (plus one if credits are not disabled which is the default). (See pam_pwquality(8).) Cannot be set to lower value than 6. (default 8) • dcredit - The maximum credit for having digits in the new password. If less than 0 it is the minimum number of digits in the new password. (default 0) • ucredit - The maximum credit for having uppercase characters in the new password. If less than 0 it is the minimum number of uppercase characters in the new password. (default 0) • lcredit - The maximum credit for having lowercase characters in the new password. If less than 0 it is the minimum number of lowercase characters in the new password. (default 0) • ocredit - The maximum credit for having other characters in the new password. If less than 0 it is the minimum number of other characters in the new password. (default 0) • minclass - The minimum number of required classes of characters for the new password (digits, uppercase, lowercase, others). (default 0) • maxrepeat - The maximum number of allowed same consecutive characters in the new password. The check is disabled if the value is 0. (default 0) • maxsequence - The maximum length of monotonic character sequences in the new password. Examples of such sequence are '12345' or 'fedcb'. Note that most such passwords will not pass the simplicity check unless the sequence is only a minor part of the password. The check is disabled if the value is 0. (default 0) • maxclassrepeat - The maximum number of allowed consecutive characters of the same class in the new password. The check is disabled if the value is 0. (default 0) Page 617 Internal Only - General • gecoscheck - If nonzero, check whether the words longer than 3 characters from the GECOS field of the user's passwd(5) entry are contained in the new password. The check is disabled if the value is 0. (default 0) • dictcheck - If nonzero, check whether the password (with possible modifications) matches a word in a dictionary. Currently the dictionary check is performed using the cracklib library. (default 1) • usercheck= - If nonzero, check whether the password (with possible modifications) contains the user name in some form. It is not performed for user names shorter than 3 characters. (default 1) • usersubstr= - If greater than 3 (due to the minimum length in usercheck), check whether the password contains a substring of at least N length in some form. (default 0) • enforcing= - If nonzero, reject the password if it fails the checks, otherwise only print the warning. This setting applies only to the pam_pwquality module and possibly other applications that explicitly change their behavior based on it. It does not affect pwmake(1) and pwscore(1). (default 1) • badwords - Space separated list of words that must not be contained in the password. These are additional words to the cracklib dictionary check. This setting can be also used by applications to emulate the gecos check for user accounts that are not created yet. • dictpath - Path to the cracklib dictionaries. Default is to use the cracklib default. • retry= - Prompt user at most N times before returning with error. The default is 1. • enforce_for_root - The module will return error on failed check even if the user changing the password is root. This option is off by default which means that just the message about the failed check is printed but root can change the password anyway. Note that root is not asked for an old password so the checks that compare the old and new password are not performed. • local_users_only - The module will not test the password quality for users that are not present in the /etc/passwd file. The module still asks for the password so the following modules in the stack can use the use_authtok option. This option is off by default. Page 618 Internal Only - General 5.3.3.2.1 Ensure password number of changed characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality difok option sets the number of characters in a password that must not be present in the old password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the difok option is set to 2 or more and follows local site policy: # grep -Psi -- '^\h*difok\h*=\h*([2-9]|[1-9][0-9]+)\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwdifok.conf:difok = 2 Verify returned value(s) are 2 or more and meet local site policy Run the following command to verify that difok is not set, is 2 or more, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?difok\h*=\h*([0-1])\b' /etc/pam.d/common-password Nothing should be returned Page 619 Internal Only - General Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set difok to 2 or more. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*difok\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "difok = 2" > /etc/security/pwquality.conf.d/50-pwdifok.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?difok\b' /usr/share/pam- configs/* Edit any returned files and remove the difok argument from the pam_pwquality.so line(s): Default Value: difok = 1 References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 620 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 621 Internal Only - General 5.3.3.2.2 Ensure password length is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The minimum password length setting determines the lowers number of characters that make up a password for a user account. There are many different theories about how to determine the best password length for an organization, but perhaps "passphrase" is a better term than "password". The minlen option sets the minimum acceptable size for the new password (plus one if credits are not disabled which is the default). Cannot be set to lower value than 6. Rationale: Strong passwords help protect systems from password attacks. Types of password attacks include dictionary attacks, which attempt to use common words and phrases, and brute force attacks, which try every possible combination of characters. Also attackers may try to obtain the account database so they can use tools to discover the accounts and passwords. Impact: In general, it is true that longer passwords are better (harder to crack), but it is also true that forced password length requirements can cause user behavior that is predictable and undesirable. For example, requiring users to have a minimum 16-character password may cause them to choose repeating patterns like fourfourfourfour or passwordpassword that meet the requirement but aren’t hard to guess. Additionally, length requirements increase the chances that users will adopt other insecure practices, like writing them down, re-using them or storing them unencrypted in their documents. Having a reasonable minimum length with no maximum character limit increases the resulting average password length used (and therefore the strength).6 Page 622 Internal Only - General Audit: Run the following command to verify that password length is 14 or more characters, and conforms to local site policy: # grep -Psi -- '^\h*minlen\h*=\h*(1[4-9]|[2-9][0-9]|[1-9][0-9]{2,})\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwlength.conf:minlen = 14 Verify returned value(s) are no less than 14 characters and meet local site policy Run the following command to verify that minlen is not set, or is 14 or more characters, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?minlen\h*=\h*([0-9]|1[0-3])\b' /etc/pam.d/system-auth /etc/pam.d/common-password Nothing should be returned Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 623 Internal Only - General Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set password length of 14 or more characters. Ensure that password length conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*minlen\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "minlen = 14" > /etc/security/pwquality.conf.d/50- pwlength.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?minlen\b' /usr/share/pam- configs/* Edit any returned files and remove the minlen argument from the pam_pwquality.so line(s): Default Value: minlen = 8 References: 1. pam_pwquality(8) 2. CIS Password Policy Guide 3. NIST SP 800-53 Rev. 5: IA-5(1) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 624 Internal Only - General 5.3.3.2.3 Ensure password complexity is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Password complexity can be set through: • minclass - The minimum number of classes of characters required in a new password. (digits, uppercase, lowercase, others). e.g. minclass = 4 requires digits, uppercase, lower case, and special characters. • dcredit - The maximum credit for having digits in the new password. If less than 0 it is the minimum number of digits in the new password. e.g. dcredit = -1 requires at least one digit • ucredit - The maximum credit for having uppercase characters in the new password. If less than 0 it is the minimum number of uppercase characters in the new password. e.g. ucredit = -1 requires at least one uppercase character • ocredit - The maximum credit for having other characters in the new password. If less than 0 it is the minimum number of other characters in the new password. e.g. ocredit = -1 requires at least one special character • lcredit - The maximum credit for having lowercase characters in the new password. If less than 0 it is the minimum number of lowercase characters in the new password. e.g. lcredit = -1 requires at least one lowercase character Rationale: Strong passwords protect systems from being hacked through brute force methods. Requiring at least one non-alphabetic character increases the search space beyond pure dictionary words, which makes the resulting password harder to crack. Forcing users to choose an excessively complex password, e.g. some combination of upper-case, lower-case, numbers, and special characters, has a negative impact. It places an extra burden on users and many will use predictable patterns (for example, a capital letter in the first position, followed by lowercase letters, then one or two numbers, and a “special character” at the end). Attackers know this, so dictionary attacks will often contain these common patterns and use the most common substitutions like, $ for s, @ for a, 1 for l, 0 for o. Impact: CIS password complexity requirements may differ from other frameworks or policies, adherence to site-specific policy is imperative. Passwords that are too complex in nature make it harder for users to remember, leading to bad practices. In addition, composition requirements provide no defense against common attack types such as social engineering or insecure storage of passwords. Page 625 Internal Only - General Audit: Run the following command to verify: • dcredit, ucredit, lcredit, and ocredit are not set to a value greater than 0 • Complexity conforms to local site policy: # grep -Psi -- '^\h*(minclass|[dulo]credit)\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwcomplexity.conf:minclass = 3 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:ucredit = -2 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:lcredit = -2 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:dcredit = -1 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:ocredit = 0 The example represents a requirement of three character classes, with passwords requiring two upper case, two lower case, and one numeric character. Run the following command to verify that module arguments in the configuration file(s) are not being overridden by arguments in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?(minclass=\d*|[dulo]credit=-?\d*)\b' /etc/pam.d/common-password Nothing should be returned Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 626 Internal Only - General Remediation: Note: CIS password complexity requirements may differ from other frameworks or policies, adherence to site-specific policy is imperative. Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?(minclass|[dulo]credit)\b' /usr/share/pam-configs/* Edit any returned files and remove the minclass, dcredit, ucredit, lcredit, and ocredit arguments from the pam_pwquality.so line(s) Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line(s) to set complexity according to local site policy: • minclass = _N_ • dcredit = _N_ # Value should be either 0 or a number proceeded by a minus (- ) symbol • ucredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol • ocredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol • lcredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol Example 1 - Set minclass = 3: #!/usr/bin/env bash { sed -ri 's/^\s*minclass\s*=/# &/' /etc/security/pwquality.conf sed -ri 's/^\s*[dulo]credit\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "minclass = 3" > /etc/security/pwquality.conf.d/50- pwcomplexity.conf } Example 2 - set dcredit = -1, ucredit = -1, and lcredit = -1: #!/usr/bin/env bash { sed -ri 's/^\s*minclass\s*=/# &/' /etc/security/pwquality.conf sed -ri 's/^\s*[dulo]credit\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '%s\n' "dcredit = -1" "ucredit = -1" "lcredit = -1" > /etc/security/pwquality.conf.d/50-pwcomplexity.conf } Page 627 Internal Only - General Default Value: minclass = 0 dcredit = 0 ucredit = 0 ocredit = 0 lcredit = 0 References: 1. pam_pwquality(8) 2. PWQUALITY.CONF(5) 3. https://www.cisecurity.org/insights/white-papers/cis-password-policy-guide 4. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 628 Internal Only - General 5.3.3.2.4 Ensure password same consecutive characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality maxrepeat option sets the maximum number of allowed same consecutive characters in a new password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the maxrepeat option is set to 3 or less, not 0, and follows local site policy: # grep -Psi -- '^\h*maxrepeat\h*=\h*[1-3]\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwrepeat.conf:maxrepeat = 3 Verify returned value(s) are 3 or less, not 0, and meet local site policy Run the following command to verify that maxrepeat is not set, is 3 or less, not 0, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?maxrepeat\h*=\h*(0|[4-9]|[1-9][0-9]+)\b' /etc/pam.d/common-password Nothing should be returned Page 629 Internal Only - General Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set maxrepeat to 3 or less and not 0. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*maxrepeat\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "maxrepeat = 3" > /etc/security/pwquality.conf.d/50- pwrepeat.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?maxrepeat\b' /usr/share/pam-configs/* Edit any returned files and remove the maxrepeat argument from the pam_pwquality.so line(s): Default Value: maxrepeat = 0 References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 630 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 631 Internal Only - General 5.3.3.2.5 Ensure password maximum sequential characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality maxsequence option sets the maximum length of monotonic character sequences in the new password. Examples of such sequence are 12345 or fedcb. The check is disabled if the value is 0. Note: Most such passwords will not pass the simplicity check unless the sequence is only a minor part of the password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the maxsequence option is set to 3 or less, not 0, and follows local site policy: # grep -Psi -- '^\h*maxsequence\h*=\h*[1-3]\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwmaxsequence.conf:maxsequence = 3 Verify returned value(s) are 3 or less, not 0, and meet local site policy Run the following command to verify that maxsequence is not set, is 3 or less, not 0, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?maxsequence\h*=\h*(0|[4-9]|[1-9][0-9]+)\b' /etc/pam.d/common-password Nothing should be returned Page 632 Internal Only - General Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set maxsequence to 3 or less and not 0. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*maxsequence\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "maxsequence = 3" > /etc/security/pwquality.conf.d/50- pwmaxsequence.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?maxsequence\b' /usr/share/pam-configs/* Edit any returned files and remove the maxsequence argument from the pam_pwquality.so line(s): Default Value: maxsequence = 0 References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 633 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 634 Internal Only - General 5.3.3.2.6 Ensure password dictionary check is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality dictcheck option sets whether to check for the words from the cracklib dictionary. Rationale: If the operating system allows the user to select passwords based on dictionary words, this increases the chances of password compromise by increasing the opportunity for successful guesses, and brute-force attacks. Audit: Run the following command to verify that the dictcheck option is not set to 0 (disabled) in a pwquality configuration file: # grep -Psi -- '^\h*dictcheck\h*=\h*0\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Nothing should be returned Run the following command to verify that the dictcheck option is not set to 0 (disabled) as a module argument in a PAM file: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?dictcheck\h*=\h*0\b' /etc/pam.d/common-password Nothing should be returned Note: • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 635 Internal Only - General Remediation: Edit any file ending in .conf in the /etc/security/pwquality.conf.d/ directory and/or the file /etc/security/pwquality.conf and comment out or remove any instance of dictcheck = 0: Example: # sed -ri 's/^\s*dictcheck\s*=/# &/' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?dictcheck\b' /usr/share/pam-configs/* Edit any returned files and remove the dictcheck argument from the pam_pwquality.so line(s) Default Value: dictcheck = 1 References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 636 Internal Only - General 5.3.3.2.7 Ensure password quality checking is enforced (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwquality module can be configured to either reject a password if it fails the checks, or only print a warning. This is configured by setting the enforcing= argument. If nonzero, a password will be rejected if it fails the checks, otherwise only a warning message will be provided. This setting applies only to the pam_pwquality module and possibly other applications that explicitly change their behavior based on it. It does not affect pwmake(1) and pwscore(1). Rationale: Strong passwords help protect systems from password attacks. Types of password attacks include dictionary attacks, which attempt to use common words and phrases, and brute force attacks, which try every possible combination of characters. Also attackers may try to obtain the account database so they can use tools to discover the accounts and passwords. Audit: Run the following command to verify that enforcing=0 has not been set in a pwquality configuration file: # grep -PHsi -- '^\h*enforcing\h*=\h*0\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Nothing should be returned Run the following command to verify that the enforcing=0 argument has not been set on the pam_pwquality module: # grep -PHsi -- '^\h*password\h+[^#\n\r]+\h+pam_pwquality\.so\h+([^#\n\r]+\h+)?enforcing=0\b' /etc/pam.d/common-password Nothing should be returned Page 637 Internal Only - General Remediation: Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?enforcing=0\b' /usr/share/pam-configs/* Edit any returned files and remove the enforcing=0 argument from the pam_pwquality.so line(s) Edit /etc/security/pwquality.conf and all files ending in .conf in the /etc/security/pwquality.conf.d/ directory and remove or comment out any line containing the enforcing = 0 argument: Example: # sed -ri 's/^\s*enforcing\s*=\s*0/# &/' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Default Value: enforcing=1 References: 1. pam_pwquality(8) 2. PWQUALITY.CONF(5) 3. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 638 Internal Only - General 5.3.3.2.8 Ensure password quality is enforced for the root user (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: If the pwquality enforce_for_root option is enabled, the module will return error on failed check even if the user changing the password is root. This option is off by default which means that just the message about the failed check is printed but root can change the password anyway. Note: The root is not asked for an old password so the checks that compare the old and new password are not performed. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the enforce_for_root option is enabled in a pwquality configuration file: # grep -Psi -- '^\h*enforce_for_root\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwroot.conf:enforce_for_root Note: • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 639 Internal Only - General Remediation: Edit or add the following line in a *.conf file in /etc/security/pwquality.conf.d or in /etc/security/pwquality.conf: Example: #!/usr/bin/env bash { [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s\n' "enforce_for_root" > /etc/security/pwquality.conf.d/50- pwroot.conf } Default Value: disabled References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 640 Internal Only - General 5.3.3.3 Configure pam_pwhistory module pam_history module - This PAM module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently. This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking pwhistory.conf provides a way to configure the default settings for saving the last passwords for each user. This file is read by the pam_pwhistory module and is the preferred method over configuring pam_pwhistory directly. The file has a very simple name = value format with possible comments starting with # character. The whitespace at the beginning of line, end of line, and around the = sign is ignored. Options: • debug - Turns on debugging via syslog(3). • use_authtok - When password changing enforce the module to use the new password provided by a previously stacked password module (this is used in the example of the stacking of the pam_passwdqc module documented below). • enforce_for_root - If this option is set, the check is enforced for root, too. • remember= - The last passwords for each user are saved. The default is 10. Value of 0 makes the module to keep the existing contents of the opasswd file unchanged. • retry= - Prompt user at most times before returning with error. The default is 1. • authtok_type= - See pam_get_authtok(3) for more details. Examples: /etc/security/pwhistory.conf file example: debug remember=5 file=/tmp/opasswd Note: The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. Page 641 Internal Only - General 5.3.3.3.1 Ensure password history remember is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/security/opasswd file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords. The number of passwords remembered is set via the remember argument value in set for the pam_pwhistory module. The pwhistory.conf provides a way to configure the default settings for saving the last passwords for each user. This file is read by the pam_pwhistory module and is the preferred method over configuring pam_pwhistory directly. • remember= - The last passwords for each user are saved. The default is 10. Value of 0 makes the module to keep the existing contents of the opasswd file unchanged. Rationale: Requiring users not to reuse their passwords make it less likely that an attacker will be able to guess the password or use a compromised password. Note: These changes only apply to accounts configured on the local system. Page 642 Internal Only - General Audit: Run the following command and verify that the remember option is set to 24 or more and meets local site policy in /etc/security/pwhistory.conf: # grep -Pi -- '^\h*remember\h*=\h*(2[4-9]|[3-9][0-9]|[1-9][0-9]{2,})\b' /etc/security/pwhistory.conf remember = 24 - OR/IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory Run the following command and verify: • The pwhistory line in /etc/pam.d/common-password includes remember= • The value of is 24 or more • The value meets local site policy # grep -P -- '\bpam_pwhistory\.so\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Note: • The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. • Only one method should be used to set the values for pwhistory. If output is provided for both locations this is considered a failure. Page 643 Internal Only - General Remediation: Note: The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. Edit or add the remember option in /etc/security/pwhistory.conf setting it to 24 or more depending on local site policy: remember = 24 - IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory. Run the following script to remove the remember= argument from the pam_pwhistory.so line in the Password section: #!/usr/bin/env bash { profiles=$(grep -Rl "pam_pwhistory.so" /usr/share/pam-configs/ || true) for profile in $profiles; do if grep -Pq 'remember\s*=\s*\d+' "$profile"; then sed -Ei 's/remember\s*=\s*[0-9]+//g' "$profile" sed -Ei 's/[[:space:]]+/ /g' "$profile" echo "Updated pam profile: $profile" pam-auth-update --package < /dev/null fi done } References: 1. NIST SP 800-53 Rev. 5: IA-5(1) 2. https://manpages.debian.org/trixie/libpam-runtime/pwhistory.conf.5.en.html 3. https://manpages.debian.org/trixie/libpam-runtime/pam_pwhistory.8.en.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 644 Internal Only - General 5.3.3.3.2 Ensure password history is enforced for the root user (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: If the pwhistory enforce_for_root option is enabled, the module will enforce password history for the root user as well Rationale: Requiring users not to reuse their passwords make it less likely that an attacker will be able to guess the password or use a compromised password Note: These changes only apply to accounts configured on the local system. Audit: Run the following command to verify that the enforce_for_root option is enabled in /etc/security/pwhistory.conf: # grep -Pi -- '^\h*enforce_for_root\b' /etc/security/pwhistory.conf enforce_for_root - OR/IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory Run the following command to verify that the enforce_for_root argument exists on the pwhistory line in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+[^#\n\r]+\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?enforce_for_ro ot\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Note: • The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. • Only one method should be used to set the values for pwhistory. If output is provided for both locations this is considered a failure. Page 645 Internal Only - General Remediation: Edit or add the following line in /etc/security/pwhistory.conf: enforce_for_root - IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory. Run the following script to remove the enforce_for_root argument from the pam_pwhistory.so line in the Password section: #!/usr/bin/env bash { profiles=$(grep -Rl "pam_pwhistory.so" /usr/share/pam-configs/ || true) for profile in $profiles; do if grep -Pq '\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?enforce_for_root\b' "$profile"; then sed -Ei '/pam_pwhistory\.so/s/\enforce_for_root\b//g' "$profile" sed -Ei 's/[[:space:]]+/ /g' "$profile" echo "Updated pam profile: $profile" pam-auth-update --package < /dev/null fi done } Note: The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. Default Value: disabled References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 646 Internal Only - General 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: use_authtok - When password changing enforce the module to set the new password to the one provided by a previously stacked password module Rationale: use_authtok allows multiple pam modules to confirm a new password before it is accepted. Audit: Run the following command to verify that the use_authtok option is enabled in /etc/security/pwhistory.conf: # grep -Pi -- '^\h*use_authtok\b' /etc/security/pwhistory.conf use_authtok - OR/IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory Run the following command to verify that the use_authtok argument exists on the pwhistory line in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+[^#\n\r]+\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?use_authtok\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Note: • The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. • Only one method should be used to set the values for pwhistory. If output is provided for both locations this is considered a failure. Page 647 Internal Only - General Remediation: Edit or add the following line in /etc/security/pwhistory.conf: use_authtok - OR/IF - The pam_pwhistory profile in /usr/share/pam-configs/ has been used to configure pwhistory. Run the following script to remove the use_authtok argument to the pam_pwhistory line in the Password section: #!/usr/bin/env bash { profiles=$(grep -Rl "pam_pwhistory.so" /usr/share/pam-configs/ || true) for profile in $profiles; do if grep -Pq '\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?use_authtok\b' "$profile"; then sed -Ei '/pam_pwhistory\.so/s/\use_authtok\b//g' "$profile" sed -Ei 's/[[:space:]]+/ /g' "$profile" echo "Updated pam profile: $profile" pam-auth-update --package < /dev/null fi done } Note: The options specified on the pwhistory.so module command line override the values from the pwhistory.conf configuration file. The pwhistory.conf file is the preferred method over configuring pam_pwhistory directly. References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 648 Internal Only - General 5.3.3.4 Configure pam_unix module The pam_unix.so module is the standard Unix authentication module. It uses standard calls from the system's libraries to retrieve and set account information as well as authentication. Usually this is obtained from the /etc/passwd and the /etc/shadow file as well if shadow is enabled. Page 649 Internal Only - General 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nullok argument overrides the default action of pam_unix.so to not permit the user access to a service if their official password is blank. Rationale: Using a strong password is essential to helping protect personal and sensitive information from unauthorized access Audit: Run the following command to verify that the nullok argument is not set on the pam_unix.so module: # grep -PHs -- '^\h*[^#\n\r]+\h+pam_unix\.so\h+([^#\n\r]+\h+)?nullok\b' /etc/pam.d/common-{password,auth,account,session,session-noninteractive} Nothing should be returned Page 650 Internal Only - General Remediation: Run the following command: # grep -PH -- '^\h*([^#\n\r]+\h+)?pam_unix\.so\h+([^#\n\r]+\h+)?nullok\b' /usr/share/pam-configs/* Edit any files returned and remove the nullok argument for the pam_unix lines Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary Auth: [success=end default=ignore] pam_unix.so try_first_pass # <- **ensure line does not include nullok nullok** Auth-Initial: [success=end default=ignore] pam_unix.so # <- **ensure line does not include nullok nullok** Account-Type: Primary Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix Note: If custom files are being used, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam-auth-update --enable command skipped CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 651 Internal Only - General 5.3.3.4.2 Ensure pam_unix does not include remember (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The remember=n argument saves the last n passwords for each user in /etc/security/opasswd in order to force password change history and keep the user from alternating between the same password too frequently. The MD5 password hash algorithm is used for storing the old passwords. Instead of this option the pam_pwhistory module should be used. The pam_pwhistory module saves the last n passwords for each user in /etc/security/opasswd using the password hash algorithm set on the pam_unix module. This allows for the yescrypt or sha512 hash algorithm to be used. Rationale: The remember=n argument should be removed to ensure a strong password hashing algorithm is being used. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local user's old passwords stored in /etc/security/opasswd. Audit: Run the following command to verify that the remember argument is not set on the pam_unix.so module: # grep -PHs -- '^\h*^\h*[^#\n\r]+\h+pam_unix\.so\h+([^#\n\r]+\h+)?remember=\d+\b' /etc/pam.d/common-{password,auth,account,session,session-noninteractive} Nothing should be returned Page 652 Internal Only - General Remediation: Run the following command: # grep -PH -- '^\h*([^#\n\r]+\h+)?pam_unix\.so\h+([^#\n\r]+\h+)?remember\b' /usr/share/pam-configs/* Edit any files returned and remove the remember=__ argument for the pam_unix lines Example output: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt remember=5 # **<- remove remember=** [success=end default=ignore] pam_unix.so obscure yescrypt remember=5 # **<- remove remember=** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix Note: If custom files are being used, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam-auth-update --enable command skipped CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 653 Internal Only - General 5.3.3.4.3 Ensure pam_unix includes a strong password hashing algorithm (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A cryptographic hash function converts an arbitrary-length input into a fixed length output. Password hashing performs a one-way transformation of a password, turning the password into another string, called the hashed password. The pam_unix module can be configured to use one of the following hashing algorithms for user's passwords: • md5 - When a user changes their password next, encrypt it with the MD5 algorithm. • bigcrypt - When a user changes their password next, encrypt it with the DEC C2 algorithm. • sha256 - When a user changes their password next, encrypt it with the SHA256 algorithm. The SHA256 algorithm must be supported by the crypt(3) function. • sha512 - When a user changes their password next, encrypt it with the SHA512 algorithm. The SHA512 algorithm must be supported by the crypt(3) function. • blowfish - When a user changes their password next, encrypt it with the blowfish algorithm. The blowfish algorithm must be supported by the crypt(3) function. • gost_yescrypt - When a user changes their password next, encrypt it with the gost-yescrypt algorithm. The gost-yescrypt algorithm must be supported by the crypt(3) function. • yescrypt - When a user changes their password next, encrypt it with the yescrypt algorithm. The yescrypt algorithm must be supported by the crypt(3) function. Rationale: The SHA-512 and yescrypt algorithms provide a stronger hash than other algorithms used by Linux for password hash generation. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local user passwords. Note: These changes only apply to the local system. Page 654 Internal Only - General Audit: Run the following command to verify that a strong password hashing algorithm is set on the pam_unix.so module: # grep -PH -- '^\h*password\h+([^#\n\r]+)\h+pam_unix\.so\h+([^#\n\r]+\h+)?(sha512|yescrypt) \b' /etc/pam.d/common-password Output should be similar to: /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Verify that the line(s) include either sha512 - OR - yescrypt Page 655 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_unix\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files and edit or add a strong hashing algorithm, either sha512 or yescrypt, that meets local site policy to the pam_unix lines in the Password section: Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary # <- Start of "Auth" section Auth: [success=end default=ignore] pam_unix.so try_first_pass Auth-Initial: [success=end default=ignore] pam_unix.so Account-Type: Primary # <- Start of "Account" section Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional # <- Start of "Session" section Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary # <- Start of "Password" section Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt # <- **ensure hashing algorithm is either sha512 or yescrypt** Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt # <- **ensure hashing algorithm is either sha512 or yescrypt** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 656 Internal Only - General Additional Information: The following command may be used to expire all non-system user ID's immediately and force them to change their passwords on next login. Any system accounts that need to be expired should be carefully done separately by the system administrator to prevent any potential problems. # awk -F: '( $3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' && $1 != "nfsnobody" ) { print $1 }' /etc/passwd | xargs -n 1 chage -d 0 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 657 Internal Only - General 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: use_authtok - When password changing enforce the module to set the new password to the one provided by a previously stacked password module Rationale: use_authtok allows multiple pam modules to confirm a new password before it is accepted. Audit: Run the following command to verify that use_authtok is set on the pam_unix.so module lines in the password stack: # grep -PH -- '^\h*password\h+([^#\n\r]+)\h+pam_unix\.so\h+([^#\n\r]+\h+)?use_authtok\b' /etc/pam.d/common-password Output should be similar to: /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Verify that the line(s) include use_authtok Page 658 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_unix\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files add use_authtok to the pam_unix line in the Password section under Password: subsection: Note: The if the file's Password section includes a Password-Initial: subsection, use_authtok should not be added to the pam_unix line in the Password-Initial: subsection Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary # <- Start of "Auth" section Auth: [success=end default=ignore] pam_unix.so try_first_pass Auth-Initial: [success=end default=ignore] pam_unix.so Account-Type: Primary # <- Start of "Account" section Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional # <- Start of "Session" section Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary # <- Start of "Password" section Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt # <- **ensure line includes use_authtok** Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt # <- **Password-Initial: subsection does not include use_authtok Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 659 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 660 Internal Only - General 5.4 User Accounts and Environment This section provides guidance on setting up secure defaults for system and user accounts and their environment. Page 661 Internal Only - General 5.4.1 Configure shadow password suite parameters While a majority of the password control parameters have been moved to PAM, some parameters are still available through the shadow password suite. Any changes made to /etc/login.defs will only be applied if the usermod command is used. If user IDs are added a different way, use the chage command to effect changes to individual user IDs. Page 662 Internal Only - General 5.4.1.1 Ensure password expiration is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PASS_MAX_DAYS parameter in /etc/login.defs allows an administrator to force passwords to expire once they reach a defined age. PASS_MAX_DAYS - The maximum number of days a password may be used. If the password is older than this, a password change will be forced. If not specified, -1 will be assumed (which disables the restriction). Rationale: The window of opportunity for an attacker to leverage compromised credentials or successfully compromise credentials via an online brute force attack is limited by the age of the password. Therefore, reducing the maximum age of a password also reduces an attacker's window of opportunity. We recommend a yearly password change. This is primarily because for all their good intentions users will share credentials across accounts. Therefore, even if a breach is publicly identified, the user may not see this notification, or forget they have an account on that site. This could leave a shared credential vulnerable indefinitely. Having an organizational policy of a 1-year (annual) password expiration is a reasonable compromise to mitigate this with minimal user burden. Impact: The password expiration must be greater than the minimum days between password changes or users will be unable to change their password. Excessive password expiration requirements do more harm than good, because these requirements make users select predictable passwords, composed of sequential words and numbers that are closely related to each other. In these cases, the next password can be predicted based on the previous one (incrementing a number used in the password for example). Also, password expiration requirements offer no containment benefits because attackers will often use credentials as soon as they compromise them. Instead, immediate password changes should be based on key events including, but not limited to: • Indication of compromise • Change of user roles • When a user leaves the organization. Not only does changing passwords every few weeks or months frustrate the user, but it’s also been suggested that it does more harm than good, because it could lead to bad practices by the user such as adding a character to the end of their existing password. Page 663 Internal Only - General Audit: Run the following command and verify PASS_MAX_DAYS is set to 365 days or less and conforms to local site policy: # grep -Pi -- '^\h*PASS_MAX_DAYS\h+\d+\b' /etc/login.defs Example output: PASS_MAX_DAYS 365 Run the following command to verify all /etc/shadow passwords PASS_MAX_DAYS: • is greater than 0 days • is less than or equal to 365 days • conforms to local site policy # awk -F: '($2~/^\$.+\$/) {if($5 > 365 || $5 < 1)print "User: " $1 " PASS_MAX_DAYS: " $5}' /etc/shadow Nothing should be returned Remediation: Set the PASS_MAX_DAYS parameter to conform to site policy in /etc/login.defs : PASS_MAX_DAYS 365 Modify user parameters for all users with a password set to match: # chage --maxdays 365 Edit /etc/login.defs and set PASS_MAX_DAYS to a value greater than 0 that follows local site policy: Example: PASS_MAX_DAYS 365 Run the following command to modify user parameters for all users with a password set to a maximum age no greater than 365 or less than 1 that follows local site policy: # chage --maxdays Example: # awk -F: '($2~/^\$.+\$/) {if($5 > 365 || $5 < 1)system ("chage --maxdays 365 " $1)}' /etc/shadow Warning: If a password has been set at system install or kickstart, the last change date field is not set, In this case, setting PASS_MAX_DAYS will immediately expire the password. One possible solution is to populate the last change date field through a command like: chage -d "$(date +%Y-%m-%d)" root Default Value: PASS_MAX_DAYS 99999 References: 1. CIS Password Policy Guide 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 664 Internal Only - General Additional Information: A value of -1 will disable password expiration. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 665 Internal Only - General 5.4.1.2 Ensure minimum password days is configured (Manual) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: PASS_MIN_DAYS - The minimum number of days allowed between password changes. Any password changes attempted sooner than this will be rejected. If not specified, 0 will be assumed (which disables the restriction). Rationale: Users may have favorite passwords that they like to use because they are easy to remember and they believe that their password choice is secure from compromise. Unfortunately, passwords are compromised and if an attacker is targeting a specific individual user account, with foreknowledge of data about that user, reuse of old, potentially compromised passwords, may cause a security breach. By restricting the frequency of password changes, an administrator can prevent users from repeatedly changing their password in an attempt to circumvent password reuse controls Impact: If a users password is set by other personnel as a procedure in dealing with a lost or expired password, the user should be forced to update this "set" password with their own password. e.g. force "change at next logon". If it is not possible to have a user set their own password immediately, and this recommendation or local site procedure may cause a user to continue using a third party generated password, PASS_MIN_DAYS for the effected user should be temporally changed to 0via chage --mindays , to allow a user to change their password immediately. For applications where the user is not using the password at console, the ability to "change at next logon" may be limited. This may cause a user to continue to use a password created by other personnel. Page 666 Internal Only - General Audit: Run the following command to verify that PASS_MIN_DAYS is set to a value greater than 0 and follows local site policy: # grep -Pi -- '^\h*PASS_MIN_DAYS\h+\d+\b' /etc/login.defs Example output: PASS_MIN_DAYS 1 Run the following command to verify all passwords have a PASS_MIN_DAYS greater than 0: # awk -F: '($2~/^\$.+\$/) {if($4 < 1)print "User: " $1 " PASS_MIN_DAYS: " $4}' /etc/shadow Nothing should be returned Remediation: Edit /etc/login.defs and set PASS_MIN_DAYS to a value greater than 0 that follows local site policy: Example: PASS_MIN_DAYS 1 Run the following command to modify user parameters for all users with a password set to a minimum days greater than zero that follows local site policy: # chage --mindays Example: # awk -F: '($2~/^\$.+\$/) {if($4 < 1)system ("chage --mindays 1 " $1)}' /etc/shadow Default Value: PASS_MIN_DAYS 0 References: 1. CIS Password Policy Guide 2. NIST SP 800-53 :: IA-5 (1) (d) 3. NIST SP 800-53A :: IA-5 (1).1 (v) 4. STIG ID: RHEL-08-020180 | Rule ID: SV-230364r627750 | CAT II 5. STIG ID: RHEL-08-020190 | Rule ID: SV-230365r858727 | CAT II 6. STIG ID: UBTU-20-010007 | Rule ID: SV-238202r1015140 | CAT III 7. STIG ID: UBTU-22-411025 | Rule ID: SV-260545r1015007 | CAT III Page 667 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 668 Internal Only - General 5.4.1.3 Ensure password expiration warning days is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PASS_WARN_AGE parameter in /etc/login.defs allows an administrator to notify users that their password will expire in a defined number of days. PASS_WARN_AGE - The number of days warning given before a password expires. A zero means warning is given only upon the day of expiration, a negative value means no warning is given. If not specified, no warning will be provided. Rationale: Providing an advance warning that a password will be expiring gives users time to think of a secure password. Users caught unaware may choose a simple password or write it down where it may be discovered. Audit: Run the following command and verify PASS_WARN_AGE is 7 or more and follows local site policy: # grep -Pi -- '^\h*PASS_WARN_AGE\h+\d+\b' /etc/login.defs Example output: PASS_WARN_AGE 7 Run the following command to verify all passwords have a PASS_WARN_AGE of 7 or more: # awk -F: '($2~/^\$.+\$/) {if($6 < 7)print "User: " $1 " PASS_WARN_AGE: " $6}' /etc/shadow Nothing should be returned Page 669 Internal Only - General Remediation: Edit /etc/login.defs and set PASS_WARN_AGE to a value of 7 or more that follows local site policy: Example: PASS_WARN_AGE 7 Run the following command to modify user parameters for all users with a password set to a minimum warning to 7 or more days that follows local site policy: # chage --warndays Example: # awk -F: '($2~/^\$.+\$/) {if($6 < 7)system ("chage --warndays 7 " $1)}' /etc/shadow Default Value: PASS_WARN_AGE 7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 670 Internal Only - General 5.4.1.4 Ensure strong password hashing algorithm is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A cryptographic hash function converts an arbitrary-length input into a fixed length output. Password hashing performs a one-way transformation of a password, turning the password into another string, called the hashed password. ENCRYPT_METHOD (string) - This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line). It can take one of these values: • MD5 - MD5-based algorithm will be used for encrypting password • SHA256 - SHA256-based algorithm will be used for encrypting password • SHA512 - SHA512-based algorithm will be used for encrypting password • BCRYPT - BCRYPT-based algorithm will be used for encrypting password • YESCRYPT - YESCRYPT-based algorithm will be used for encrypting password • DES - DES-based algorithm will be used for encrypting password (default) Note: • This parameter overrides the deprecated MD5_CRYPT_ENAB variable. • This parameter will only affect the generation of group passwords. • The generation of user passwords is done by PAM and subject to the PAM configuration. • It is recommended to set this variable consistently with the PAM configuration. Rationale: The SHA-512 and yescrypt algorithms provide a stronger hash than other algorithms used by Linux for password hash generation. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local group passwords. Page 671 Internal Only - General Audit: Run the following command to verify the hashing algorithm is sha512 or yescrypt in /etc/login.defs: # grep -Pi -- '^\h*ENCRYPT_METHOD\h+(SHA512|YESCRYPT)\b' /etc/login.defs Example output: ENCRYPT_METHOD SHA512 - OR - ENCRYPT_METHOD YESCRYPT Remediation: Edit /etc/login.defs and set the ENCRYPT_METHOD to SHA512 or YESCRYPT: ENCRYPT_METHOD Example: ENCRYPT_METHOD YESCRYPT Note: • This only effects local groups' passwords created after updating the file to use sha512 or yescrypt. • If it is determined that the password algorithm being used is not sha512 or yescrypt, once it is changed, it is recommended that all group passwords be updated to use the stronger hashing algorithm. • It is recommended that the chosen hashing algorithm is consistent across /etc/login.defs and the PAM configuration Default Value: ENCRYPT_METHOD SHA512 References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 672 Internal Only - General 5.4.1.5 Ensure inactive password lock is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: User accounts that have been inactive for over a given period of time can be automatically disabled. INACTIVE - Defines the number of days after the password exceeded its maximum age where the user is expected to replace this password. The value is stored in the shadow password file. An input of 0 will disable an expired password with no delay. An input of -1 will blank the respective field in the shadow password file. Rationale: Inactive accounts pose a threat to system security since the users are not logging in to notice failed login attempts or other anomalies. Audit: Run the following command and verify INACTIVE conforms to site policy (no more than 45 days): # useradd -D | grep INACTIVE INACTIVE=45 Verify all users with a password have Password inactive no more than 45 days after password expires Verify all users with a password have Password inactive no more than 45 days after password expires: Run the following command and Review list of users and INACTIVE to verify that all users INACTIVE conforms to site policy (no more than 45 days): # awk -F: '($2~/^\$.+\$/) {if($7 > 45 || $7 < 0)print "User: " $1 " INACTIVE: " $7 "Days"}' /etc/shadow Nothing should be returned Page 673 Internal Only - General Remediation: Run the following command to set the default password inactivity period to 45 days or less that meets local site policy: # useradd -D -f Example: # useradd -D -f 45 Run the following command to modify user parameters for all users with a password set to a inactive age of 45 days or less that follows local site policy: # chage --inactive Example: # awk -F: '($2~/^\$.+\$/) {if($7 > 45 || $7 < 0)system ("chage --inactive 45 " $1)}' /etc/shadow Default Value: INACTIVE=-1 References: 1. CIS Password Policy Guide Additional Information: A value of -1 would disable this setting. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 674 Internal Only - General 5.4.1.6 Ensure all users last password change date is in the past (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: All users should have a password change date in the past. Rationale: If a user's recorded password change date is in the future, then they could bypass any set password expiration. Audit: Run the following script and verify nothing is returned: #!/usr/bin/env bash { while IFS= read -r l_user; do l_change=$(date -d "$(chage --list $l_user | grep '^Last password change' | cut -d: -f2 | grep -v 'never$')" +%s) if [[ "$l_change" -gt "$(date +%s)" ]]; then echo "User: \"$l_user\" last password change was \"$(chage --list $l_user | grep '^Last password change' | cut -d: -f2)\"" fi done < <(awk -F: '$2~/^\$.+\$/{print $1}' /etc/shadow) } Remediation: Investigate any users with a password change date in the future and correct them. Locking the account, expiring the password, or resetting the password manually may be appropriate. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 675 Internal Only - General 5.4.2 Configure root and system accounts and environment Page 676 Internal Only - General 5.4.2.1 Ensure root is the only UID 0 account (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Any account with UID 0 has superuser privileges on the system. Rationale: This access must be limited to only the default root account and only from the system console. Administrative access must be through an unprivileged account using an approved mechanism as noted in the Recommendation "Ensure access to the su command is restricted". Audit: Run the following command and verify that only "root" is returned: # awk -F: '($3 == 0) { print $1 }' /etc/passwd root Remediation: Run the following command to change the root account UID to 0: # usermod -u 0 root Modify any users other than root with UID 0 and assign them a new UID. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 677 Internal Only - General 5.4.2.2 Ensure root is the only GID 0 account (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The usermod command can be used to specify which group the root account belongs to. This affects permissions of files that are created by the root account. Rationale: Using GID 0 for the root account helps prevent root -owned files from accidentally becoming accessible to non-privileged users. Audit: Run the following command to verify the root user's primary GID is 0, and no other user's have GID 0 as their primary GID: # awk -F: '($1 !~ /^(sync|shutdown|halt|operator)/ && $4=="0") {print $1":"$4}' /etc/passwd root:0 Note: User's: sync, shutdown, halt, and operator are excluded from the check for other user's with GID 0 Remediation: Run the following command to set the root user's GID to 0: # usermod -g 0 root Run the following command to set the root group's GID to 0: # groupmod -g 0 root Remove any users other than the root user with GID 0 or assign them a new GID if appropriate. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 678 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 679 Internal Only - General 5.4.2.3 Ensure group root is the only GID 0 group (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The groupmod command can be used to specify which group the root group belongs to. This affects permissions of files that are group owned by the root group. Rationale: Using GID 0 for the root group helps prevent root group owned files from accidentally becoming accessible to non-privileged users. Audit: Run the following command to verify no group other than root is assigned GID 0: # awk -F: '$3=="0"{print $1":"$3}' /etc/group root:0 Remediation: Run the following command to set the root group's GID to 0: # groupmod -g 0 root Remove any groups other than the root group with GID 0 or assign them a new GID if appropriate. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 680 Internal Only - General 5.4.2.4 Ensure root account access is controlled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of methods to access the root account directly. Without a password set any user would be able to gain access and thus control over the entire system. Rationale: Access to root should be secured at all times. Impact: If there are any automated processes that relies on access to the root account without authentication, they will fail after remediation. Audit: Run the following command to verify that either the root user's password is set or the root user's account is locked: # passwd -S root | awk '$2 ~ /^(P|L)/ {print "User: \"" $1 "\" Password is status: " $2}' Verify the output is either: User: "root" Password is status: P - OR - User: "root" Password is status: L Note: • P - Password is set • L - Password is locked Remediation: Run the following command to set a password for the root user: # passwd root - OR - Run the following command to lock the root user account: # usermod -L root Page 681 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 682 Internal Only - General 5.4.2.5 Ensure root path integrity (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The root user can execute any command on the system and could be fooled into executing programs unintentionally if the PATH is not set correctly. Rationale: Including the current working directory (.) or other writable directory in root's executable path makes it likely that an attacker can gain superuser access by forcing an administrator operating as root to execute a Trojan horse program. Page 683 Internal Only - General Audit: Run the following script to verify root's path does not include: • Locations that are not directories • An empty directory (::) • A trailing (:) • Current working directory (.) • Non root owned directories • Directories that less restrictive than mode 0755 #!/usr/bin/env bash { a_output2=() l_pmask="0022" l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" l_root_path="$(sudo su - root -c env | awk -F= '$1=="PATH"{print $2}')" IFS=":" read -ra a_path_loc <<< "$l_root_path" grep -q -- "::" <<< "$l_root_path" && \ a_output2+=(" - root's path contains a empty directory (::)") grep -Pq -- ":\h*$" <<< "$l_root_path" && \ a_output2+=(" - root's path contains a trailing (:)") grep -Pq -- '(^\h*|:)\.(:|\h*$)' <<< "$l_root_path" && \ a_output2+=(" - root's path contains current working directory (.)") for l_path in "${a_path_loc[@]}"; do if [ -d "$l_path" ]; then while IFS=: read -r l_fmode l_fown; do [ "$l_fown" != "root" ] && \ a_output2+=(" - Directory: \"$l_path\" is owned by: \"$l_fown\"" \ " should be owned by \"root\"") [ $(( $l_fmode & $l_pmask )) -gt 0 ] && \ a_output2+=(" - Directory: \"$l_path\" is mode: \"$l_fmode\"" \ " and should be mode: \"$l_maxperm\" or more restrictive") done <<< "$(stat -Lc '%#a:%U' "$l_path")" else a_output2+=(" - \"$l_path\" is not a directory") fi done if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" \ " - Root's path is correctly configured" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" \ "- * Reasons for audit failure * :" "${a_output2[@]}" fi } Page 684 Internal Only - General Remediation: Correct or justify any: • Locations that are not directories • Empty directories (::) • Trailing (:) • Current working directory (.) • Non root owned directories • Directories that less restrictive than mode 0755 References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 685 Internal Only - General 5.4.2.6 Ensure root user umask is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user file-creation mode mask (umask) is used to determine the file permission for newly created directories and files. In Linux, the default permissions for any newly created directory is 0777 (rwxrwxrwx), and for any newly created file it is 0666 (rw-rw- rw-). The umask modifies the default Linux permissions by restricting (masking) these permissions. The umask is not simply subtracted, but is processed bitwise. Bits set in the umask are cleared in the resulting file mode. umask can be set with either Octal or Symbolic values: • Octal (Numeric) Value - Represented by either three or four digits. ie umask 0027 or umask 027. If a four digit umask is used, the first digit is ignored. The remaining three digits effect the resulting permissions for user, group, and world/other respectively. • Symbolic Value - Represented by a comma separated list for User u, group g, and world/other o. The permissions listed are not masked by umask. ie a umask set by umask u=rwx,g=rx,o= is the Symbolic equivalent of the Octal umask 027. This umask would set a newly created directory with file mode drwxr-x--- and a newly created file with file mode rw-r-----. root user Shell Configuration Files: • /root/.profile - Is executed to configure the root users' shell before the initial command prompt. Is only read by login shells. • /root/.bashrc - Is executed for interactive shells. only read by a shell that's both interactive and non-login umask is set by order of precedence. If umask is set in multiple locations, this order of precedence will determine the system's default umask. Order of precedence: 1. /root/.profile 2. /root/.bashrc 3. The system default umask Rationale: Setting a secure value for umask ensures that users make a conscious choice about their file permissions. A permissive umask value could result in directories or files with excessive permissions that can be read and/or written to by unauthorized users. Page 686 Internal Only - General Audit: Run the following command to verify that the root user files, /root/.profile and /root/.bashrc, do not include a umask that is less restrictive than 0027: # grep -Psi -- '^\h*umask\h+((\d{1,2}(\d[^7]|[^2- 7]\d)\b)|(u=[rwx]{1,3},)?(((g=[rx]?[rx]?w[rx]?[rx]?\b)(,o=[rwx]{1,3})?)|((g=[ wrx]{1,3},)?o=[wrx]{1,3}\b)))' /root/.profile /root/.bashrc Nothing should be returned. Remediation: Edit /root/.profile and /root/.bashrc and either: • remove, comment out, or update any line with umask. - OR - • update any line that includes umask to a value of 0027 or more restrictive. Example: umask 027 Note: the Recommendation "Ensure default user umask is configured" includes guidance to set the default umask Default Value: System default umask References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 687 Internal Only - General 5.4.2.7 Ensure system accounts do not have a valid login shell (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of accounts provided with most distributions that are used to manage applications and are not intended to provide an interactive shell. Furthermore, a user may add special accounts that are not intended to provide an interactive shell. Rationale: It is important to make sure that accounts that are not being used by regular users are prevented from being used to provide an interactive shell. By default, most distributions set the password field for these accounts to an invalid string, but it is also recommended that the shell field in the password file be set to the nologin shell. This prevents the account from potentially being used to run any commands. Audit: Run the following command to verify system accounts, except for root, halt, sync, shutdown or nfsnobody, do not have a valid login shell: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 == 65534) && $(NF) ~ pat) {print "Service account: \"" $1 "\" has a valid shell: " $7}' /etc/passwd } Nothing should be returned Page 688 Internal Only - General Remediation: Run the following command to set the shell for any service accounts returned by the audit to nologin: # usermod -s $(command -v nologin) Example script: #!/usr/bin/env bash { l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 == 65534) && $(NF) ~ pat) {system ("usermod -s '"$(command -v nologin)"' " $1)}' /etc/passwd } References: 1. NIST SP 800-53 Rev. 5: AC-2(5), AC-3, AC-11, MP-2 Additional Information: The root, sync, shutdown, and halt users are exempted from requiring a non-login shell. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 689 Internal Only - General 5.4.2.8 Ensure accounts without a valid login shell are locked (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of accounts provided with most distributions that are used to manage applications and are not intended to provide an interactive shell. Furthermore, a user may add special accounts that are not intended to provide an interactive shell. Rationale: It is important to make sure that accounts that are not being used by regular users are prevented from being used to provide an interactive shell. By default, most distributions set the password field for these accounts to an invalid string, but it is also recommended that the shell field in the password file be set to the nologin shell. This prevents the account from potentially being used to run any commands. Audit: Run the following script to verify all non-root accounts without a valid login shell are locked. #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" while IFS= read -r l_user; do passwd -S "$l_user" | awk '$2 !~ /^L/ {print "Account: \"" $1 "\" does not have a valid login shell and is not locked"}' done < <(awk -v pat="$l_valid_shells" -F: '($1 != "root" && $(NF) !~ pat) {print $1}' /etc/passwd) } Nothing should be returned Page 690 Internal Only - General Remediation: Run the following command to lock any non-root accounts without a valid login shell returned by the audit: # usermod -L Example script:: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" while IFS= read -r l_user; do passwd -S "$l_user" | awk '$2 !~ /^L/ {system ("usermod -L " $1)}' done < <(awk -v pat="$l_valid_shells" -F: '($1 != "root" && $(NF) !~ pat) {print $1}' /etc/passwd) } References: 1. NIST SP 800-53 Rev. 5: AC-2(5), AC-3, AC-11, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 691 Internal Only - General 5.4.3 Configure user default environment Page 692 Internal Only - General 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: /etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh and available to be queried by other programs. Be aware that there are programs which consult this file to find out if a user is a normal user; for example, FTP daemons traditionally disallow access to users with shells not included in this file. Rationale: A user can use chsh to change their configured shell. If a user has a shell configured that isn't in in /etc/shells, then the system assumes that they're somehow restricted. In the case of chsh it means that the user cannot change that value. Other programs might query that list and apply similar restrictions. By putting nologin in /etc/shells, any user that has nologin as its shell is considered a full, unrestricted user. This is not the expected behavior for nologin. Audit: Run the following command to verify that nologin is not listed in the /etc/shells file: # grep -Ps '^\h*([^#\n\r]+)?\/nologin\b' /etc/shells Nothing should be returned Remediation: Edit /etc/shells and remove any lines that include nologin References: 1. shells(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 693 Internal Only - General 5.4.3.2 Ensure default user shell timeout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: TMOUT is an environmental setting that determines the timeout of a shell in seconds. • TMOUT=n - Sets the shell timeout to n seconds. A setting of TMOUT=0 disables timeout. • readonly TMOUT- Sets the TMOUT environmental variable as readonly, preventing unwanted modification during run-time. • export TMOUT - exports the TMOUT variable System Wide Shell Configuration Files: • /etc/profile - used to set system wide environmental variables on users shells. The variables are sometimes the same ones that are in the .bash_profile, however this file is used to set an initial PATH or PS1 for all shell users of the system. is only executed for interactive login shells, or shells executed with the --login parameter. • /etc/profile.d - /etc/profile will execute the scripts within /etc/profile.d/*.sh. It is recommended to place your configuration in a shell script within /etc/profile.d to set your own system wide environmental variables. • /etc/bash.bashrc - System wide version of .bashrc. In Fedora derived distributions, /etc/bashrc also invokes /etc/profile.d/*.sh if non-login shell, but redirects output to /dev/null if non-interactive. Is only executed for interactive shells or if BASH_ENV is set to /etc/bash.bashrc. Rationale: Setting a timeout value reduces the window of opportunity for unauthorized user access to another user's shell session that has been left unattended. It also ends the inactive session and releases the resources associated with that session. Audit: Run the following script to verify that TMOUT is configured to: include a timeout of no more than 900 seconds, to be readonly, to be exported, and is not being changed to a longer timeout. Page 694 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=(); l_tmout_set="900" f_tmout_read_chk() { a_out=(); a_out2=() l_tmout_readonly="$(grep -P -- '^\h*(typeset\h\- xr\hTMOUT=\d+|([^#\n\r]+)?\breadonly\h+TMOUT\b)' "$l_file")" l_tmout_export="$(grep -P -- '^\h*(typeset\h\- xr\hTMOUT=\d+|([^#\n\r]+)?\bexport\b([^#\n\r]+\b)?TMOUT\b)' "$l_file")" if [ -n "$l_tmout_readonly" ]; then a_out+=(" - Readonly is set as: \"$l_tmout_readonly\" in: \"$l_file\"") else a_out2+=(" - Readonly is not set in: \"$l_file\"") fi if [ -n "$l_tmout_export" ]; then a_out+=(" - Export is set as: \"$l_tmout_export\" in: \"$l_file\"") else a_out2+=(" - Export is not set in: \"$l_file\"") fi } while IFS= read -r l_file; do l_tmout_value="$(grep -Po -- '^([^#\n\r]+)?\bTMOUT=\d+\b' "$l_file" | awk -F= '{print $2}')" f_tmout_read_chk if [ -n "$l_tmout_value" ]; then if [[ "$l_tmout_value" -le "$l_tmout_set" && "$l_tmout_value" -gt "0" ]]; then a_output+=(" - TMOUT is set to: \"$l_tmout_value\" in: \"$l_file\"") [ "${#a_out[@]}" -gt 0 ] && a_output+=("${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=("${a_out[@]}") fi if [[ "$l_tmout_value" -gt "$l_tmout_set" || "$l_tmout_value" -le "0" ]]; then a_output2+=(" - TMOUT is incorrectly set to: \"$l_tmout_value\" in: \"$l_file\"") [ "${#a_out[@]}" -gt 0 ] && a_output2+=(" ** Incorrect TMOUT value **" "${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=("${a_out2[@]}") fi else [ "${#a_out[@]}" -gt 0 ] && a_output2+=(" - TMOUT is not set" "${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - TMOUT is not set" "${a_out2[@]}") fi done < <(grep -Pls -- '^([^#\n\r]+)?\bTMOUT\b' /etc/*bashrc /etc/profile /etc/profile.d/*.sh) [[ "${#a_output[@]}" -le 0 && "${#a_output2[@]}" -le 0 ]] && a_output2+=(" - TMOUT is not configured") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 695 Internal Only - General Note: If TMOUT is set as readonly through readonly TMOUT and/or typeset -xr in more than once, you will receive an error message when logging into a terminal session or connecting with openSSH. It is recommended that TMOUT be set only once in only one file. Remediation: Review /etc/bashrc, /etc/profile, and all files ending in *.sh in the /etc/profile.d/ directory and remove or edit all TMOUT=_n_ entries to follow local site policy. TMOUT should not exceed 900 or be equal to 0. Configure TMOUT in one of the following files: • A file in the /etc/profile.d/ directory ending in .sh • /etc/profile • /etc/bashrc Example command to set TMOUT to 900 seconds in a file in /etc/profile.d/: # printf '%s\n' "# Set TMOUT to 900 seconds" "typeset -xr TMOUT=900" > /etc/profile.d/50-tmout.sh TMOUT configuration examples: typeset -xr TMOUT=900 Deprecated methods: • As multiple lines: TMOUT=900 readonly TMOUT export TMOUT • As a single line: readonly TMOUT=900 ; export TMOUT Additional Information: The audit and remediation in this recommendation apply to bash and shell. If other shells are supported on the system, it is recommended that their configuration files also are checked. Other methods of setting a timeout exist for other shells not covered here. Ensure that the timeout conforms to your local policy. Page 696 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 697 Internal Only - General 5.4.3.3 Ensure default user umask is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user file-creation mode mask (umask) is used to determine the file permission for newly created directories and files. In Linux, the default permissions for any newly created directory is 0777 (rwxrwxrwx), and for any newly created file it is 0666 (rw-rw- rw-). The umask modifies the default Linux permissions by restricting (masking) these permissions. The umask is not simply subtracted, but is processed bitwise. Bits set in the umask are cleared in the resulting file mode. umask can be set with either Octal or Symbolic values: • Octal (Numeric) Value - Represented by either three or four digits. ie umask 0027 or umask 027. If a four digit umask is used, the first digit is ignored. The remaining three digits effect the resulting permissions for user, group, and world/other respectively. • Symbolic Value - Represented by a comma separated list for User u, group g, and world/other o. The permissions listed are not masked by umask. ie a umask set by umask u=rwx,g=rx,o= is the Symbolic equivalent of the Octal umask 027. This umask would set a newly created directory with file mode drwxr-x--- and a newly created file with file mode rw-r-----. The default umask can be set to use the pam_umask module or in a System Wide Shell Configuration File. The user creating the directories or files has the discretion of changing the permissions via the chmod command, or choosing a different default umask by adding the umask command into a User Shell Configuration File, ( .bash_profile or .bashrc), in their home directory. Setting the default umask: • pam_umask module: o will set the umask according to the system default in /etc/login.defs and user settings, solving the problem of different umask settings with different shells, display managers, remote sessions etc. o umask= value in the /etc/login.defs file is interpreted as Octal o Setting USERGROUPS_ENAB to yes in /etc/login.defs (default): ▪ will enable setting of the umask group bits to be the same as owner bits. (examples: 022 -> 002, 077 -> 007) for non-root users, if the uid is the same as gid, and username is the same as the Page 698 Internal Only - General ▪ userdel will remove the user's group if it contains no more members, and useradd will create by default a group with the name of the user • System Wide Shell Configuration File: o /etc/profile - used to set system wide environmental variables on users shells. The variables are sometimes the same ones that are in the .bash_profile, however this file is used to set an initial PATH or PS1 for all shell users of the system. is only executed for interactive login shells, or shells executed with the --login parameter. o /etc/profile.d - /etc/profile will execute the scripts within /etc/profile.d/*.sh. It is recommended to place your configuration in a shell script within /etc/profile.d to set your own system wide environmental variables. o /etc/bashrc - System wide version of .bashrc. In Fedora derived distributions, etc/bashrc also invokes /etc/profile.d/*.sh if non-login shell, but redirects output to /dev/null if non-interactive. Is only executed for interactive shells or if BASH_ENV is set to /etc/bashrc. User Shell Configuration Files: • ~/.bash_profile - Is executed to configure your shell before the initial command prompt. Is only read by login shells. • ~/.bashrc - Is executed for interactive shells. only read by a shell that's both interactive and non-login umask is set by order of precedence. If umask is set in multiple locations, this order of precedence will determine the system's default umask. Order of precedence: 1. A file in /etc/profile.d/ ending in .sh - This will override any other system- wide umask setting 2. In the file /etc/profile 3. On the pam_umask.so module in /etc/pam.d/postlogin 4. In the file /etc/login.defs 5. In the file /etc/default/login Rationale: Setting a secure default value for umask ensures that users make a conscious choice about their file permissions. A permissive umask value could result in directories or files with excessive permissions that can be read and/or written to by unauthorized users. Satisfies: SRG-OS-000480-GPOS-00228, SRG-OS-000480-GPOS-00227 Page 699 Internal Only - General Audit: Run the following commands to verify the systemwide umask is 0027 (u=rwx,g=rx,o=) or more restrictive: 1. Run the following command to verify umask is set to 027 or more restrictive in a file ending in .sh in /etc/profile.d/ # grep -Psi -- '^\h*umask\b' /etc/profile.d/*.sh Example output: umask 027 2. Run the following command to verify UMASK is 027 or more restrictive in /etc/login.defs: # grep -Psi -- '^\h*UMASK\b' /etc/login.defs Example output: UMASK 027 Remediation: 1. Run the following script to comment out all occurrences of umask that are less restrictive than 027 in files ending in *.sh in the /etc/profile.d/ directory: #!/usr/bin/env bash { while IFS= read -r -d $'\0' l_file; do sed -ri '/^\s*umask\s+0?(0[01][0-7]|0[0-7][^7]|[^0][0-7][0- 7])(\s*|\s+.*)$/s/^/# /' "$l_file" done < <(find /etc/profile.d/ -type f -name '*.sh' -print0) } 2. Create or edit a file in /etc/profile.d/ ending in *.sh and add or modify the following line: umask 0027 Example: # printf '%s\n' "" "umask 027" >> /etc/profile.d/60-default_umask.sh 3. Edit /etc/login.defs and add or update the following line: UMASK 027 Page 700 Internal Only - General Notes: • This method only applies to bash and shell. If other shells are supported on the system, it is recommended that their configuration files also are checked • If the pam_umask.so module is going to be used to set umask, ensure that it's not being overridden by another setting. Refer to the PAM_UMASK(8) man page for more information Default Value: UMASK 022 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-020351 | RULE ID: SV-230383r1017192 | CAT II 5. STIG ID: RHEL-08-020353 | RULE ID: SV-230385r1017194 | CAT II 6. STIG ID: RHEL-09-412055 | RULE ID: SV-258072r1045155 | CAT II 7. STIG ID: RHEL-09-412065 | RULE ID: SV-258074r991590 | CAT II 8. STIG ID: RHEL-09-412070 | RULE ID: SV-258075r991590 | CAT II 9. STIG ID: ALMA-09-017620 | RULE ID: SV-269235r1050117 | CAT II 10. STIG ID: ALMA-09-017840 | RULE ID: SV-269237r1050119 | CAT II 11. STIG ID: UBTU-22-412035 | RULE ID: SV-260555r991590 | CAT II 12. STIG ID: UBTU-24-300030 | RULE ID: SV-270716r1066637 | CAT II 13. STIG ID: SLES-15-040420 | RULE ID: SV-235030r991590 | CAT II Additional Information: • Other methods of setting a default user umask exist • If other methods are in use in your environment they should be audited • The default user umask can be overridden with a user specific umask • The user creating the directories or files has the discretion of changing the permissions: o Using the chmod command o Setting a different default umask by adding the umask command into a User Shell Configuration File, (.bashrc), in their home directory o Manually changing the umask for the duration of a login session by running the umask command Page 701 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 702 Internal Only - General 6 Logging and Auditing The items in this section describe how to configure logging, log monitoring, and auditing, using tools included in most distributions. It is recommended that rsyslog be used for logging (with logwatch providing summarization) and auditd be used for auditing (with aureport providing summarization) to automatically monitor logs for intrusion attempts and other suspicious system behavior. In addition to the local log files created by the steps in this section, it is also recommended that sites collect copies of their system logs on a secure, centralized log server via an encrypted connection. Not only does centralized logging help sites correlate events that may be occurring on multiple systems, but having a second copy of the system log information may be critical after a system compromise where the attacker has modified the local log files on the affected system(s). If a log correlation system is deployed, configure it to process the logs described in this section. Because it is often necessary to correlate log information from many different systems (particularly after a security incident) it is recommended that the time be synchronized among systems and devices connected to the local network. The standard Internet protocol for time synchronization is the Network Time Protocol (NTP), which is supported by most network-ready devices. Reference manual page for more information on configuring chrony. It is important that all logs described in this section be monitored on a regular basis and correlated to determine trends. A seemingly innocuous entry in one log could be more significant when compared to an entry in another log. Note on log file permissions: There really isn't a "one size fits all" solution to the permissions on log files. Many sites utilize group permissions so that administrators who are in a defined security group, such as "wheel" do not have to elevate privileges to root in order to read log files. Also, if a third party log aggregation tool is used, it may need to have group permissions to read the log files, which is preferable to having it run setuid to root. Therefore, there are two remediation and audit steps for log file permissions. One is for systems that do not have a secured group method implemented that only permits root to read the log files (root:root 600). The other is for sites that do have such a setup and are designated as root:securegrp 640 where securegrp is the defined security group (in some cases wheel). Page 703 Internal Only - General 6.1 System Logging Logging services should be configured to prevent information leaks and to aggregate logs on a remote server so that they can be reviewed in the event of a system compromise. A centralized log server provides a single point of entry for further analysis, monitoring and filtering. Security principals for logging • Ensure transport layer security is implemented between the client and the log server. • Ensure that logs are rotated as per the environment requirements. • Ensure all locally generated logs have the appropriate permissions. • Ensure all security logs are sent to a remote log server. • Ensure the required events are logged. What is covered This section will cover the minimum best practices for the usage of either rsyslog or journald. The recommendations are written such that each is wholly independent of each other and only one is implemented. • If your organization makes use of an enterprise wide logging system completely outside of rsyslog or journald, then the following recommendations do not directly apply. However, the principals of the recommendations should be followed regardless of what solution is implemented. If the enterprise solution incorporates either of these tools, careful consideration should be given to the following recommendations to determine exactly what applies. • Should your organization make use of both rsyslog and journald, take care how the recommendations may or may not apply to you. What is not covered • Enterprise logging systems not utilizing rsyslog or journald. As logging is very situational and dependent on the local environment, not everything can be covered here. • Transport layer security should be applied to all remote logging functionality. Both rsyslog and journald supports secure transport and should be configured as such. • The log server. There are a multitude of reasons for a centralized log server (and keeping a short period of logging on the local system), but the log server is out of scope for these recommendations. Page 704 Internal Only - General 6.1.1 Configure journald Included in the systemd suite is a journaling service called systemd- journald.service for the collection and storage of logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources such as: • Classic RFC3164 BSD syslog via the /dev/log socket • STDOUT/STDERR of programs via StandardOutput=journal + StandardError=journal in service files (both of which are default settings) • Kernel log messages via the /dev/kmsg device node • Audit records via the kernel’s audit subsystem • Structured log messages via journald’s native protocol Any changes made to the systemd-journald configuration will require a re-start of systemd-journald Page 705 Internal Only - General 6.1.1.1 Configure systemd-journald service systemd-journald is a system service that collects and stores logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources: • Kernel log messages, via kmsg • Simple system log messages, via the libc syslog call • Structured system log messages via the native Journal API • Standard output and standard error of service units • Audit records, originating from the kernel audit subsystem The daemon will implicitly collect numerous metadata fields for each log messages in a secure and unfakeable way. See systemd.journal-fields man page for more information about the collected metadata. The journal service stores log data either persistently below /var/log/journal or in a volatile way below /run/log/journal/. By default, log data is stored persistently if /var/log/journal/ exists during boot, with an implicit fallback to volatile storage. Use Storage= in journald.conf to configure where log data is placed, independently of the existence of /var/log/journal/. On systems where /var/log/journal/ does not exist but where persistent logging is desired, and the default journald.conf is used, it is sufficient to create the directory and ensure it has the correct access modes and ownership. Page 706 Internal Only - General 6.1.1.1.1 Ensure journald service is active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Ensure that the systemd-journald service is enabled to allow capturing of logging events. Rationale: If the systemd-journald service is not enabled to start on boot, the system will not capture logging events. Audit: Run the following command to verify systemd-journald is active: # systemctl is-active systemd-journald.service active Remediation: Run the following commands to unmask, enable, and start systemd- journald.service # systemctl unmask systemd-journald.service # systemctl --now enable systemd-journald.service References: 1. CCI-001665 2. NIST SP 800-53 :: SC-24 3. NIST SP 800-53A :: SC-24.1 (v) 4. STIG ID: RHEL-09-211040 | RULE ID: SV-257783r991562 | CAT II 5. STIG ID: ALMA-09-041490 | RULE ID: SV-269428r1050311 | CAT II 6. STIG ID: OL09-00-002400 | RULE ID: SV-271739r1091929 | CAT II Page 707 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 708 Internal Only - General 6.1.1.1.2 Ensure journald log file access is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald will create logfiles that do not already exist on the system. This setting controls what permissions will be applied to these newly created files. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected. Page 709 Internal Only - General Audit: First determine if there is an override file /etc/tmpfiles.d/systemd.conf. If so, this file will override all default settings as defined in /usr/lib/tmpfiles.d/systemd.conf and should be inspected. If no override file exists, inspect the default /usr/lib/tmpfiles.d/systemd.conf against the site specific requirements. Ensure that file permissions are mode 0640 or more restrictive. Run the following script to verify if an override file exists or not and if the files permissions are mode 0640 or more restrictive: #!/usr/bin/env bash { config_files=(/etc/tmpfiles.d/systemd.conf /usr/lib/tmpfiles.d/systemd.conf) warn=() for file in "${config_files[@]}"; do [ -f "$file" ] || continue while read -r type path perm _; do if [[ "$type" == "f" && "$perm" =~ ^0?[0-7]{3,4}$ ]]; then perm="${perm#0}" if [ -f "$path" ]; then actual=$(stat -c "%a" "$path" 2>/dev/null) if [[ -n "$actual" && "$actual" -gt 640 ]]; then warn+=("File: $path | Perm: $actual (expected max: 640) | Defined in: $file") fi fi fi done < "$file" done if [ "${#warn[@]}" -eq 0 ]; then echo "No files with permissions more permissive than 0640." else echo -e " *** REVIEW ***" printf "%s\n" "${warn[@]}" fi } Remediation: If the default configuration is not appropriate for the site specific requirements, copy /usr/lib/tmpfiles.d/systemd.conf to /etc/tmpfiles.d/systemd.conf and modify as required. Requirements is either 0640 or site policy if that is less restrictive. References: 1. NIST SP 800-53 Rev. 5: AC-3, AU-2, AU-12, MP-2, SI-5 Page 710 Internal Only - General Additional Information: See man 5 tmpfiles.d for detailed information on the permission sets for the relevant log files. Further information with examples can be found at https://www.freedesktop.org/software/systemd/man/tmpfiles.d.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 711 Internal Only - General 6.1.1.1.3 Ensure journald log file rotation is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald includes the capability of rotating log files regularly to avoid filling up the system with logs or making the logs unmanageably large. The file /etc/systemd/journald.conf is the configuration file used to specify how logs generated by Journald should be rotated. Rationale: By keeping the log files smaller and more manageable, a system administrator can easily archive these files to another system and spend less time looking through inordinately large log files. Audit: Review /etc/systemd/journald.conf and files in the /etc/systemd/journald.conf.d/ directory ending in .conf. Verify logs are rotated according to site policy. Run the following command and ensure logs are rotated according to site policy: # systemd-analyze cat-config systemd/journald.conf | tac | \ grep -Psi -- '\b(SystemMaxUse|SystemKeepFree|RuntimeMaxUse|RuntimeKeepFree|MaxFileSec)=' SystemMaxUse= SystemKeepFree= RuntimeMaxUse= RuntimeKeepFree= MaxFileSec= Remediation: Edit /etc/systemd/journald.conf or a file ending in .conf the /etc/systemd/journald.conf.d/ directory. Set the following parameters in the [Journal] section to ensure logs are rotated according to site policy. The settings should be carefully understood as there are specific edge cases and prioritization of parameters. Example Configuration [Journal] SystemMaxUse=1G SystemKeepFree=500M RuntimeMaxUse=200M RuntimeKeepFree=50M MaxFileSec=1month Note: If these settings appear in a canonically later file, or later in the same file, the setting will be overwritten Page 712 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12 2. https://man7.org/linux/man-pages/man5/journald.conf.5.html Additional Information: See man 5 journald.conf for detailed information regarding the parameters in use. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 713 Internal Only - General 6.1.1.1.4 Ensure journald ForwardToSyslog is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from journald should be kept in the confines of the service and not forwarded to other services. Rationale: - IF - journald is the method for capturing logs, all logs of the system should be handled by journald and not forwarded to other logging mechanisms. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Page 714 Internal Only - General Audit: - IF - journald is the method for capturing logs Run the following script to verify ForwardToSyslog in not set to yes: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="ForwardToSyslog" l_option_value="no" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 715 Internal Only - General Remediation: - IF - rsyslog is the preferred method for capturing logs, this section and Recommendation should be skipped and the "Configure rsyslog" section followed. - IF - journald is the preferred method for capturing logs: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: ForwardToSyslog=no Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "" "ForwardToSyslog=no" >> /etc/systemd/journald.conf.d/60-journald.conf else printf '%s\n' "" "[Journal]" "ForwardToSyslog=no" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald Default Value: ForwardToSyslog=no References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-6, AU-7, AU-12 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html Page 716 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 717 Internal Only - General 6.1.1.1.5 Ensure journald Storage is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from journald may be stored in volatile memory or persisted locally on the server. Logs in memory will be lost upon a system reboot. By persisting logs to local disk on the server they are protected from loss due to a reboot. Rationale: Writing log data to disk will provide the ability to forensically reconstruct events which may have impacted the operations or security of a system even after a system crash or reboot. Page 718 Internal Only - General Audit: Run the following script to verify Storage is set to persistent: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="Storage" l_option_value="persistent" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 719 Internal Only - General Remediation: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: Storage=persistent Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "Storage=persistent" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "" "[Journal]" "Storage=persistent" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-12 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 720 Internal Only - General 6.1.1.1.6 Ensure journald Compress is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The journald system includes the capability of compressing overly large files to avoid filling up the system with logs or making the logs unmanageably large. Rationale: Uncompressed large files may unexpectedly fill a filesystem leading to resource unavailability. Compressing logs prior to write can prevent sudden, unexpected filesystem impacts. Page 721 Internal Only - General Audit: Run the following script to verify Compress is set to yes: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="Compress" l_option_value="yes" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 722 Internal Only - General Remediation: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: Compress=yes Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "" "Compress=yes" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "" "[Journal]" "Compress=yes" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald References: 1. NIST SP 800-53 Rev. 5: AU-4 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html Page 723 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 724 Internal Only - General 6.1.1.2 Configure systemd-journal-remote The systemd-journal-remote package includes systemd-journal-upload. systemd-journal-upload will upload journal entries to the URL specified with --url=. This program reads journal entries from one or more journal files, similarly to journalctl. systemd-journal-upload transfers the raw content of journal file and uses HTTP as a transport protocol. systemd-journal-upload.service is a system service that uses systemd-journal- upload to upload journal entries to a server. It uses the configuration in journal- upload.conf. Page 725 Internal Only - General 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-remote supports the ability to send log events it gathers to a remote log host or to receive messages from remote hosts, thus enabling centralized log management. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Audit: - IF - journald will be used for logging on the system: Run the following command to verify systemd-journal-remote is installed. # dpkg-query -s systemd-journal-remote &>/dev/null && echo "systemd-journal- remote is installed" Verify the output matches: systemd-journal-remote is installed Remediation: Run the following command to install systemd-journal-remote: # apt install systemd-journal-remote References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7 AU-12 Page 726 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 727 Internal Only - General 6.1.1.2.2 Ensure systemd-journal-upload authentication is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-upload supports the ability to send log events it gathers to a remote log host. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Audit: Run the following script to verify systemd-journal-upload authentication is configured: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journal-upload.conf" l_block="Upload" while IFS= read -r l_file; do l_file="${l_file//# /}" gawk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi -- \ '^\h*(URL|ServerKeyFile|ServerCertificateFile|TrustedCertificateFile)\h*=\h*\ H+\b' done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') } Verify the output matches per your environments certificate locations and the URL of the log server: Example output: URL=192.168.50.42 ServerKeyFile=/etc/ssl/private/journal-upload.pem ServerCertificateFile=/etc/ssl/certs/journal-upload.pem TrustedCertificateFile=/etc/ssl/ca/trusted.pem Page 728 Internal Only - General Remediation: Edit the /etc/systemd/journal-upload.conf file or a file in /etc/systemd/journal-upload.conf.d ending in .conf and ensure the following lines are set in the [Upload] section per your environment: [Upload] URL=192.168.50.42 ServerKeyFile=/etc/ssl/private/journal-upload.pem ServerCertificateFile=/etc/ssl/certs/journal-upload.pem TrustedCertificateFile=/etc/ssl/ca/trusted.pem Example script: #!/usr/bin/env bash { [ ! -d "/etc/systemd/journal-upload.conf.d" ] && \ mkdir -p /etc/systemd/journal-upload.conf.d printf '%s\n' "" "[Upload]" "URL=192.168.50.42" \ "ServerKeyFile=/etc/ssl/private/journal-upload.pem" \ "ServerCertificateFile=/etc/ssl/certs/journal-upload.pem" \ "TrustedCertificateFile=/etc/ssl/ca/trusted.pem" \ >> /etc/systemd/journal-upload.conf.d/60-journal-upload.conf } Restart the service: # systemctl reload-or-restart systemd-journal-upload References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 729 Internal Only - General 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-upload supports the ability to send log events it gathers to a remote log host. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Audit: Run the following command to verify systemd-journal-upload is enabled. # systemctl is-enabled systemd-journal-upload.service enabled Run the following command to verify systemd-journal-upload is active: # systemctl is-active systemd-journal-upload.service active Remediation: Run the following commands to unmask, enable and start systemd-journal-upload: # systemctl unmask systemd-journal-upload.service # systemctl --now enable systemd-journal-upload.service References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12 Page 730 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 731 Internal Only - General 6.1.1.2.4 Ensure systemd-journal-remote service is not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-remote supports the ability to receive messages from remote hosts, thus acting as a log server. Clients should not receive data from other hosts. Note: • The same package, systemd-journal-remote, is used for both sending logs to remote hosts and receiving incoming logs. • With regards to receiving logs, there are two services; systemd-journal- remote.socket and systemd-journal-remote.service. Rationale: If a client is configured to also receive data, thus turning it into a server, the client system is acting outside it's operational boundary. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Audit: Run the following command to verify systemd-journal-remote.socket and systemd- journal-remote.service are not enabled: # systemctl is-enabled systemd-journal-remote.socket systemd-journal- remote.service | grep -P -- '^enabled' Nothing should be returned Run the following command to verify systemd-journal-remote.socket and systemd- journal-remote.service are not active: # systemctl is-active systemd-journal-remote.socket systemd-journal- remote.service | grep -P -- '^active' Nothing should be returned Remediation: Run the following commands to stop and mask systemd-journal-remote.socket and systemd-journal-remote.service: # systemctl stop systemd-journal-remote.socket systemd-journal-remote.service # systemctl mask systemd-journal-remote.socket systemd-journal-remote.service Page 732 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7 AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 733 Internal Only - General 6.1.2 Configure rsyslog The rsyslog software package may be used instead of the default journald logging mechanism. Rsyslog has evolved over several decades. For this reason it supports three different configuration formats (“languages”): • basic - previously known as the sysklogd format, this is the format best used to express basic things, such as where the statement fits on a single line. o It stems back to the original syslog.conf format, in use now for several decades. o The most common use case is matching on facility/severity and writing matching messages to a log file. • advanced - previously known as the RainerScript format, this format was first available in rsyslog v6 and is the current, best and most precise format for non- trivial use cases where more than one line is needed. o Prior to v7, there was a performance impact when using this format that encouraged use of the basic format for best results. Current versions of rsyslog do not suffer from this (historical) performance impact. o This new style format is specifically targeted towards more advanced use cases like forwarding to remote hosts that might be partially offline. • obsolete legacy - previously known simply as the legacy format, this format is exactly what its name implies: it is obsolete and should not be used when writing new configurations. It was created in the early days (up to rsyslog version 5) where we expected that rsyslog would extend sysklogd just mildly. Consequently, it was primarily aimed at small additions to the original sysklogd format. o Practice has shown that it was notoriously hard to use for more advanced use cases, and thus we replaced it with the advanced format. o In essence, everything that needs to be written on a single line that starts with a dollar sign is legacy format. Users of this format are encouraged to migrate to the basic or advanced formats. Note: This section only applies if rsyslog is the chosen method for client side logging. Do not apply this section if journald is used. Page 734 Internal Only - General 6.1.2.1 Ensure rsyslog is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsyslog software is recommended in environments where journald does not meet operation requirements. Rationale: The security enhancements of rsyslog such as connection-oriented (i.e. TCP) transmission of logs, the option to log to database formats, and the encryption of log data en route to a central logging server) justify installing and configuring the package. Audit: - IF - rsyslog is being used for logging on the system: Run the following command to verify rsyslog is installed: # dpkg-query -s rsyslog &>/dev/null && echo "rsyslog is installed" Verify the output matches: rsyslog is installed Remediation: Run the following command to install rsyslog: # apt install rsyslog Default Value: Installed References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 Page 735 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 736 Internal Only - General 6.1.2.2 Ensure rsyslog service is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Once the rsyslog package is installed, ensure that the service is enabled. Rationale: If the rsyslog service is not enabled to start on boot, the system will not capture logging events. Audit: - IF - rsyslog is being used for logging on the system: Run the following command to verify rsyslog.service is enabled: # systemctl is-enabled rsyslog enabled Run the following command to verify rsyslog.service is active: # systemctl is-active rsyslog.service active Remediation: - IF - rsyslog is being used for logging on the system: Run the following commands to unmask, enable, and start rsyslog.service: # systemctl unmask rsyslog.service # systemctl enable rsyslog.service # systemctl start rsyslog.service References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-010561 | RULE ID: SV-230298r1017108 | CAT II 5. STIG ID: OL08-00-010561 | RULE ID: SV-248615r991589 | CAT II 6. STIG ID: ALMA-09-053150 | RULE ID: SV-269518r1050401 | CAT II 7. STIG ID: UBTU-22-652010 | RULE ID: SV-260588r991562 | CAT II Page 737 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 738 Internal Only - General 6.1.2.3 Ensure journald is configured to send logs to rsyslog (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from systemd-journald may be stored in volatile memory or persisted locally on the server. Utilities exist to accept remote export of systemd-journald logs, however, use of the rsyslog service provides a consistent means of log collection and export. Rationale: - IF - rsyslog is the preferred method for capturing logs, all logs of the system should be sent to it for further processing. Note: This recommendation only applies if rsyslog is the chosen method for client side logging. Do not apply this recommendation if systemd-journald is used. Page 739 Internal Only - General Audit: - IF - rsyslog is the preferred method for capturing logs Run the following script to verify that logs are forwarded to rsyslog by setting ForwardToSyslog to yes in the systemd-journald configuration: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="ForwardToSyslog" l_option_value="yes" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="/etc/$l_conf_file" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Run the following command to verify systemd-journald.service and rsyslog.service are loaded and active: # systemctl list-units --type service | grep -P -- '(journald|rsyslog)' Output should be similar to: rsyslog.service loaded active running System Logging Service systemd-journald.service loaded active running Journal Service Page 740 Internal Only - General Remediation: - IF - Journald is the preferred method for capturing logs, this section and Recommendation should be skipped and the "Configure Journald" section followed. - IF - rsyslog is the preferred method for capturing logs: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: ForwardToSyslog=yes Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\] /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "ForwardToSyslog=yes" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "[Journal]" "ForwardToSyslog=yes" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: Restart systemd-journald.service: # systemctl reload-or-restart systemd-journald.service References: 1. NIST SP 800-53 Rev. 5: AC-3, AU-2, AU-4, AU-12, MP-2 2. SYSTEMD-JOURNALD.SERVICE(8) 3. JOURNALD.CONF(5) Page 741 Internal Only - General Additional Information: As noted in the systemd-journald man pages, systemd-journald logs may be exported to rsyslog either through the process mentioned here, or through a facility like systemd-journald.service. There are trade-offs involved in each implementation, where ForwardToSyslog will immediately capture all events (and forward to an external log server, if properly configured), but may not capture all boot-up activities. Mechanisms such as systemd-journald.service, on the other hand, will record bootup events, but may delay sending the information to rsyslog, leading to the potential for log manipulation prior to export. Be aware of the limitations of all tools employed to secure a system. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.9 Centralize Audit Logs v8 Centralize, to the extent possible, audit log collection and retention across ● ● enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. 6.5 Central Log Management v7 Ensure that appropriate logs are being aggregated to a central log ● ● management system for analysis and review. Page 742 Internal Only - General 6.1.2.4 Ensure rsyslog log file creation mode is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog will create logfiles that do not already exist on the system. The global() configuration object umask, available in rsyslog 8.26.0+, sets the rsyslogd process’ umask. If not specified, the system-provided default is used. The value given must always be a 4-digit octal number, with the initial digit being zero. The legacy $umask parameter sets the rsyslogd process' umask. If not specified, the system-provided default is used. The value given must always be a 4-digit octal number, with the initial digit being zero. The legacy $FileCreateMode parameter allows the setting of the mode with which rsyslogd creates new files. If not specified, the value 0644 is used. The value given must always be a 4-digit octal number, with the initial digit being zero. Please note that the actual permission depend on rsyslogd process umask. If in doubt, use $umask 0000 right at the beginning of the configuration file to remove any restrictions. The legacy $FileCreateMode may be specified multiple times. If so, it specifies the creation mode for all selector lines that follow until the next $FileCreateMode parameter. Order of lines is vitally important. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected. Audit: Run the following command Run the following command to verify $FileCreateMode: # grep -Ps '^\h*\$FileCreateMode\h+0[0,2,4,6][0,2,4]0\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Verify the output is includes 0640 or more restrictive: $FileCreateMode 0640 Should a site policy dictate less restrictive permissions, ensure to follow said policy. Note: More restrictive permissions such as 0600 is implicitly sufficient. Page 743 Internal Only - General Remediation: Edit either /etc/rsyslog.conf or a dedicated .conf file in /etc/rsyslog.d/ and set $FileCreateMode to 0640 or more restrictive: $FileCreateMode 0640 Restart the service: # systemctl restart rsyslog References: 1. RSYSLOG.CONF(5) 2. NIST SP 800-53 Rev. 5: AC-3, AC-6, MP-2 3. https://www.rsyslog.com/doc/ CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote ● ● ● file systems, databases, and applications. 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 5.1 Establish Secure Configurations v7 Maintain documented, standard security configuration standards for all ● ● ● authorized operating systems and software. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 744 Internal Only - General 6.1.2.5 Ensure rsyslog logging is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files specifies rules for logging and which files are to be used to log certain classes of messages. Rationale: A great deal of important security-related information is sent via rsyslog (e.g., successful and failed su attempts, failed login attempts, root login attempts, etc.). Audit: Review the contents of /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files to ensure appropriate logging is set. In addition, run the following command and verify that the log files are logging information as expected: # ls -l /var/log/ Remediation: Edit the following lines in the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files as appropriate for your environment. Note: The below configuration is shown for example purposes only. Due care should be given to how the organization wishes to store log data. *.emerg :omusrmsg:* auth,authpriv.* /var/log/secure mail.* -/var/log/mail mail.info -/var/log/mail.info mail.warning -/var/log/mail.warn mail.err /var/log/mail.err cron.* /var/log/cron *.=warning;*.=err -/var/log/warn *.crit /var/log/warn *.*;mail.none;news.none -/var/log/messages local0,local1.* -/var/log/localmessages local2,local3.* -/var/log/localmessages local4,local5.* -/var/log/localmessages local6,local7.* -/var/log/localmessages Run the following command to reload the rsyslogd configuration: # systemctl restart rsyslog References: 1. See the rsyslog.conf(5) man page for more information. 2. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12 Page 745 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 746 Internal Only - General 6.1.2.6 Ensure rsyslog is configured to send logs to a remote log host (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog supports the ability to send log events it gathers to a remote log host or to receive messages from remote hosts, thus enabling centralized log management. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Audit: Review the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and verify that logs are sent to a central host: basic format # grep "^*.*[^I][^I]*@" /etc/rsyslog.conf /etc/rsyslog.d/*.conf Output should include @@: Example: *.* @@loghost.example.com advanced format # grep -Psi -- '^\s*([^#]+\s+)?action\(([^#]+\s+)?\btarget=\"?[^#"]+\"?\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Output should include target=: Example: *.* action(type="omfwd" target="loghost.example.com" port="514" protocol="tcp" Remediation: Edit the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and add the following line (where loghost.example.com is the name of your central log host). The target directive may either be a fully qualified domain name or an IP address. Example: *.* action(type="omfwd" target="loghost.example.com" port="514" protocol="tcp" action.resumeRetryCount="100" queue.type="LinkedList" queue.size="1000") Run the following command to reload rsyslog.service: # systemctl reload-or-restart rsyslog.service Page 747 Internal Only - General References: 1. See the rsyslog.conf(5) man page for more information. 2. NIST SP 800-53 Rev. 5: AU-6 3. https://www.rsyslog.com/doc/ Additional Information: In addition, see the rsyslog documentation for implementation details of TLS. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 748 Internal Only - General 6.1.2.7 Ensure rsyslog is not configured to receive logs from a remote client (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog supports the ability to receive messages from remote hosts, thus acting as a log server. Clients should not receive data from other hosts. Rationale: If a client is configured to also receive data, thus turning it into a server, the client system is acting outside its operational boundary. Audit: Review the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and verify that the system is not configured to accept incoming logs. advanced format # grep -Psi -- '^\h*module\(load=\"?imtcp\"?\)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf # grep -Psi -- '^\h*input\(type=\"?imtcp\"?\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Nothing should be returned obsolete legacy format # grep -Psi -- '^\h*\$ModLoad\h+imtcp\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf # grep -Psi -- '^\h*\$InputTCPServerRun\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Nothing should be returned Remediation: Should there be any active log server configuration found in the auditing section, modify those files and remove the specific lines highlighted by the audit. Verify none of the following entries are present in any of /etc/rsyslog.conf or /etc/rsyslog.d/*.conf. advanced format module(load="imtcp") input(type="imtcp" port="514") deprecated legacy format $ModLoad imtcp $InputTCPServerRun Restart the service: # systemctl restart rsyslog Page 749 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12, CM-6 2. https://www.rsyslog.com/doc/index.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 750 Internal Only - General 6.1.2.8 Ensure logrotate is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The system includes the capability of rotating log files regularly to avoid filling up the system with logs or making the logs unmanageably large. The file /etc/logrotate.d/syslog is the configuration file used to rotate log files created by syslog or rsyslog. Rationale: By keeping the log files smaller and more manageable, a system administrator can easily archive these files to another system and spend less time looking through inordinately large log files. Audit: Review /etc/logrotate.conf and /etc/logrotate.d/* and verify logs are rotated according to site policy. Remediation: Edit /etc/logrotate.conf and /etc/logrotate.d/* to ensure logs are rotated according to site policy. References: 1. NIST SP 800-53 Rev. 5: AU-8 Additional Information: If no maxage setting is set for logrotate a situation can occur where logrotate is interrupted and fails to delete rotated log files. It is recommended to set this to a value greater than the longest any log file should exist on your system to ensure that any such log file is removed but standard rotation settings are not overridden. Page 751 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 752 Internal Only - General 6.1.2.9 Ensure rsyslog-gnutls is installed (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: TLS protocol support for rsyslog (GnuTLS). This netstream plugin allows rsyslog to send and receive encrypted syslog messages via the syslog-transport-tls IETF standard protocol using GnuTLS. Rationale: Traditional syslog is a clear-text protocol that means anyone with a sniffer can have a peek at your data. rsyslog-gnutls is a secure communications library implementing the SSL, TLS and DTLS protocols and technologies around them, and provides an easy way to encrypt syslog communication. Impact: Enabling TLS support using rsyslog-gnutls requires certificate management to ensure reliable encrypted logging. If misconfigured, remote log forwarding may fail until valid certificates and trusted CAs are applied. Audit: Run the following command and verify rsyslog-gnutls is installed: # dpkg-query -s rsyslog-gnutls &>/dev/null && echo "rsyslog-gnutls is installed" rsyslog-gnutls is installed Remediation: Run the following command to install rsyslog-gnutls: # apt install rsyslog-gnutls References: 1. https://www.rsyslog.com/doc/tutorials/tls.html Page 753 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 754 Internal Only - General 6.1.2.10 Ensure rsyslog forwarding uses gtls (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Network stream drivers are a layer between various parts of rsyslogd (e.g. the imtcp module) and the transport layer. They provide sequenced delivery, authentication and confidentiality to the upper layers. Drivers implement different capabilities. Rationale: StreamDriver must be set to gtls to enable TLS for encrypting syslog traffic. Impact: Users need to know about netstream drivers because they need to configure the proper driver, and proper driver properties, to achieve desired results. Audit: Run the following command and verify # grep -Psi -- '^\h*StreamDriver=\"gtls\"' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Example Output /etc/rsyslog.d/40-forward.conf: StreamDriver="gtls" StreamDriverMode="1" StreamDriverAuthMode="anon") Remediation: Edit rsyslog.conf or a .conf file in /etc/rsyslog.d/ to use gtls: Example /etc/rsyslog.d/40-forward.conf # certificate files - just CA for a client global(DefaultNetstreamDriverCAFile="/path/to/contrib/gnutls/ca.pem") # set up the action for all messages action(type="omfwd" protocol="tcp" target="s.example.net" port="6514" StreamDriver="gtls" StreamDriverMode="1" StreamDriverAuthMode="anon") References: 1. https://www.rsyslog.com/doc/tutorials/tls_cert_client.html 2. https://www.rsyslog.com/doc/rainerscript/global.html 3. https://www.rsyslog.com/doc/concepts/netstrm_drvr.html 4. https://www.rsyslog.com/doc/concepts/ns_gtls.html Page 755 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 756 Internal Only - General 6.1.2.11 Ensure rsyslog CA certificates are configured (Manual) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: CA Certificate is used to sign all of your other certificates. The CA cert must be trusted by all clients and servers. The private key must be well-protected and not given to any third parties. Rationale: The certificate authority certificates ensures that the client only trusts and connects to rsyslog servers presenting a certificated signed by the CA preventing data leakage or exposure in transit. Impact: Proper certificate management is required to prevent misconfiguration and log forwarding failures until the trust chain is restored. When it comes to certificate validity, keep in mind that you need to recreate all certificates when this one expires. So, it may be a good idea to use a long period, eg. 3650 days (roughly 10 years). You need to specify that the certificates belong to an authority. The certificate is used to sign other certificates. Audit: Run the following command and verify rsyslog is configured to use CA certificate: # grep -Psi -- 'DefaultNetstreamDriverCAFile' /etc/rsyslog.conf /etc/rsyslog.d/* Example Output /etc/rsyslog.d/40- forward.conf:global(DefaultNetstreamDriverCAFile="/path/to/contrib/gnutls/ca. pem") Note: The audit only checks for the CA certificate DefaultNetstreamDriverCAFile parameter for a ca.pem file path, it does not check the validity of the certificate. However, the CA cert must be trusted by all clients and servers. The private key must be well-protected and not given to any third parties. Page 757 Internal Only - General Remediation: Edit rsyslog.conf or a .conf file in /etc/rsyslog.d/ to the correct path for the CA certificate: Example # certificate files - just CA for a client global(DefaultNetstreamDriverCAFile="/path/to/contrib/gnutls/ca.pem") Note: Only distribute the ca.pem, NOT ca-key.pem (the private key). Distributing the CA private key would totally breach security as everybody could issue new certificates on the behalf of this CA. References: 1. https://www.rsyslog.com/doc/tutorials/tls.html#client-setup CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 758 Internal Only - General 6.1.3 Configure Logfiles Page 759 Internal Only - General 6.1.3.1 Ensure access to all logfiles has been configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Log files contain information from many services on the the local system, or in the event of a centralized log server, others systems logs as well. In general log files are found in /var/log/, although application can be configured to store logs elsewhere. Should your application store logs in another, ensure to run the same test on that location. Rationale: It is important that log files have the correct permissions to ensure that sensitive data is protected and that only the appropriate users / groups have access to them. Audit: Run the following script to verify that files in /var/log/ have appropriate permissions and ownership: Page 760 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=() f_file_test_chk() { a_out2=() maxperm="$( printf '%o' $(( 0777 & ~$perm_mask)) )" [ $(( $l_mode & $perm_mask )) -gt 0 ] && \ a_out2+=(" o Mode: \"$l_mode\" should be \"$maxperm\" or more restrictive") [[ ! "$l_user" =~ $l_auser ]] && \ a_out2+=(" o Owned by: \"$l_user\" and should be owned by \"${l_auser//|/ or }\"") [[ ! "$l_group" =~ $l_agroup ]] && \ a_out2+=(" o Group owned by: \"$l_group\" and should be group owned by \"${l_agroup//|/ or }\"") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - File: \"$l_fname\" is:" "${a_out2[@]}") } while IFS= read -r -d $'\0' l_file; do while IFS=: read -r l_fname l_mode l_user l_group; do if grep -Pq -- '\/(apt)\h*$' <<< "$(dirname "$l_fname")"; then perm_mask='0133' l_auser="root" l_agroup="(root|adm)"; f_file_test_chk else case "$(basename "$l_fname")" in lastlog | lastlog.* | wtmp | wtmp.* | wtmp-* | btmp | btmp.* | btmp-* | README) perm_mask='0113' l_auser="root" l_agroup="(root|utmp)" f_file_test_chk ;; cloud-init.log* | localmessages* | waagent.log*) perm_mask='0133' l_auser="(root|syslog)" l_agroup="(root|adm)" file_test_chk ;; secure{,*.*,.*,-*} | auth.log | syslog | messages) perm_mask='0137' l_auser="(root|syslog)" l_agroup="(root|adm)" f_file_test_chk ;; *.journal | *.journal~) perm_mask='0137' l_auser="root" l_agroup="(root|systemd-journal)" f_file_test_chk ;; *) perm_mask='0137' l_auser="(root|syslog)" l_agroup="(root|adm)" if [ "$l_user" = "root" ] || ! grep -Pq -- "^\h*$(awk -F: '$1=="'"$l_user"'" {print $7}' /etc/passwd)\b" /etc/shells; then ! grep -Pq -- "$l_auser" <<< "$l_user" && l_auser="(root|syslog|$l_user)" ! grep -Pq -- "$l_agroup" <<< "$l_group" && l_agroup="(root|adm|$l_group)" fi f_file_test_chk ;; esac fi done < <(stat -Lc '%n:%#a:%U:%G' "$l_file") done < <(find -L /var/log -type f \( -perm /0137 -o ! -user root -o ! -group root \) -print0) if [ "${#a_output2[@]}" -le 0 ]; then a_output+=(" - All files in \"/var/log/\" have appropriate permissions and ownership") printf '\n%s' "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '\n%s' "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" "" fi } Page 761 Internal Only - General Remediation: Run the following script to update permissions and ownership on files in /var/log. Although the script is not destructive, ensure that the output is captured in the event that the remediation causes issues. Page 762 Internal Only - General #!/usr/bin/env bash { a_output2=() f_file_test_fix() { a_out2=() maxperm="$( printf '%o' $(( 0777 & ~$perm_mask)) )" if [ $(( $l_mode & $perm_mask )) -gt 0 ]; then a_out2+=(" o Mode: \"$l_mode\" should be \"$maxperm\" or more restrictive" " x Removing excess permissions") chmod "$l_rperms" "$l_fname" fi if [[ ! "$l_user" =~ $l_auser ]]; then a_out2+=(" o Owned by: \"$l_user\" and should be owned by \"${l_auser//|/ or }\"" " x Changing ownership to: \"$l_fix_account\"") chown "$l_fix_account" "$l_fname" fi if [[ ! "$l_group" =~ $l_agroup ]]; then a_out2+=(" o Group owned by: \"$l_group\" and should be group owned by \"${l_agroup//|/ or }\"" " x Changing group ownership to: \"$l_fix_account\"") chgrp "$l_fix_account" "$l_fname" fi [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - File: \"$l_fname\" is:" "${a_out2[@]}") } l_fix_account='root' while IFS= read -r -d $'\0' l_file; do while IFS=: read -r l_fname l_mode l_user l_group; do if grep -Pq -- '\/(apt)\h*$' <<< "$(dirname "$l_fname")"; then perm_mask='0133' l_rperms="u-x,go-wx" l_auser="root" l_agroup="(root|adm)"; f_file_test_fix else case "$(basename "$l_fname")" in lastlog | lastlog.* | wtmp | wtmp.* | wtmp-* | btmp | btmp.* | btmp-* | README) perm_mask='0113' l_rperms="ug-x,o-wx" l_auser="root" l_agroup="(root|utmp)" f_file_test_fix ;; cloud-init.log* | localmessages* | waagent.log*) perm_mask='0133' l_rperms="u-x,go-wx" l_auser="(root|syslog)" l_agroup="(root|adm)" file_test_fix ;; secure | auth.log | syslog | messages) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="(root|syslog)" l_agroup="(root|adm)" f_file_test_fix ;; *.journal | *.journal~) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="root" l_agroup="(root|systemd-journal)" f_file_test_fix ;; *) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="(root|syslog)" l_agroup="(root|adm)" if [ "$l_user" = "root" ] || ! grep -Pq -- "^\h*$(awk -F: '$1=="'"$l_user"'" {print $7}' /etc/passwd)\b" /etc/shells; then ! grep -Pq -- "$l_auser" <<< "$l_user" && l_auser="(root|syslog|$l_user)" ! grep -Pq -- "$l_agroup" <<< "$l_group" && l_agroup="(root|adm|$l_group)" fi f_file_test_fix ;; esac fi done < <(stat -Lc '%n:%#a:%U:%G' "$l_file") done < <(find -L /var/log -type f \( -perm /0137 -o ! -user root -o ! -group root \) -print0) if [ "${#a_output2[@]}" -le 0 ]; then # If all files passed, then we report no changes a_output+=(" - All files in \"/var/log/\" have appropriate permissions and ownership") printf '\n%s' "- All files in \"/var/log/\" have appropriate permissions and ownership" " o No changes required" "" else printf '\n%s' "${a_output2[@]}" "" fi } Page 763 Internal Only - General Note: • You may also need to change the configuration for your logging software or services for any logs that had incorrect permissions. • If there are services that log to other locations, ensure that those log files have the appropriate access configured. References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 764 Internal Only - General 6.2 System Auditing The Linux Auditing System operates on a set of rules that collects certain types of system activity to facilitate incident investigation, detect unauthorized access or modification of data. By default events will be logged to /var/log/audit/audit.log, which can be configured in /etc/audit/auditd.conf. The following types of audit rules can be specified: • Control rules: Configuration of the auditing system. • File system rules: Allow the auditing of access to a particular file or a directory. Also known as file watches. • System call rules: Allow logging of system calls that any specified program makes. Audit rules can be set: • On the command line using the auditctl utility. These rules are not persistent across reboots. • In /etc/audit/audit.rules. These rules have to be merged and loaded before they are active. Notes: • For 64 bit systems that have arch as a rule parameter, you will need two rules: one for 64 bit and one for 32 bit systems calls. • If the auditing system is configured to be locked (-e 2), a system reboot will be required in order to load any changes. • Key names are optional on the rules and will not be used as a compliance auditing. The usage of key names is highly recommended as it facilitates organization and searching, as such, all remediation steps will have key names supplied. • It is best practice to store the rules, in number prepended files, in /etc/audit/rules.d/. Rules must end in a .rules suffix. This then requires the use of augenrules to merge all the rules into /etc/audit/audit.rules based on their their alphabetical (lexical) sort order. All benchmark recommendations follow this best practice for remediation, specifically using the prefix of 50 which is centre weighed if all rule sets make use of the number prepending naming convention. • Your system may have been customized to change the default UID_MIN. All samples output uses 1000, but this value will not be used in compliance auditing. To confirm the UID_MIN for your system, run the following command: awk '/^\s*UID_MIN/{print $2}' /etc/login.defs Page 765 Internal Only - General Normalization The Audit system normalizes some entries, so when you look at the sample output keep in mind that: • With regards to users whose login UID is not set, the values -1 / unset / 4294967295 are equivalent and normalized to -1. • When comparing field types and both sides of the comparison is valid fields types, such aseuid!=uid, then the auditing system may normalize such that the output is uid!=euid. • Some parts of the rule may be rearranged whilst others are dependant on previous syntax. For example, the following two statements are the same: -a always,exit -F arch=b64 -S execve -C uid!=euid -F auid!=-1 -F key=user_emulation and -a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation Capacity planning The recommendations in this section implement auditing policies that not only produces large quantities of logged data, but may also negatively impact system performance. Capacity planning is critical in order not to adversely impact production environments. • Disk space. If a significantly large set of events are captured, additional on system or off system storage may need to be allocated. If the logs are not sent to a remote log server, ensure that log rotation is implemented else the disk will fill up and the system will halt. Even when logs are sent to a log server, ensure sufficient disk space to allow caching of logs in the case of temporary network outages. • Disk IO. It is not just the amount of data collected that should be considered, but the rate at which logs are generated. • CPU overhead. System call rules might incur considerable CPU overhead. Test the systems open/close syscalls per second with and without the rules to gauge the impact of the rules. Page 766 Internal Only - General 6.2.1 Configure auditd Service The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Page 767 Internal Only - General 6.2.1.1 Ensure auditd packages are installed (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: auditd is the userspace component to the Linux Auditing System. It's responsible for writing audit records to the disk Rationale: The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Audit: Run the following command and verify auditd is installed: # dpkg-query -s auditd &>/dev/null && echo auditd is installed auditd is installed Run the following command to verify audispd-plugins is installed: # dpkg-query -s audispd-plugins &>/dev/null && echo audispd-plugins is installed audispd-plugins is installed Remediation: Run the following command to Install auditd and audispd-plugins # apt install auditd audispd-plugins References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12, SI-5 2. STIG ID: UBTU-20-010182 | RULE ID: SV-238298r958506 | CAT II 3. STIG ID: UBTU-22-653015 | RULE ID: SV-260591r1015023 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 768 Internal Only - General 6.2.1.2 Ensure auditd service is enabled and active (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Turn on the auditd daemon to record system events. Rationale: The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Audit: Run the following command to verify auditd is enabled: # systemctl is-enabled auditd | grep '^enabled' enabled Verify result is "enabled". Run the following command to verify auditd is active: # systemctl is-active auditd | grep '^active' active Verify result is active Remediation: Run the following commands to unmask, enable and start auditd: # systemctl unmask auditd # systemctl enable auditd # systemctl start auditd References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 2. STIG ID: UBTU-20-010182 | RULE ID: SV-238298r958506 | CAT II 3. STIG ID: UBTU-22-653015 | RULE ID: SV-260591r1015023 | CAT II Page 769 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 770 Internal Only - General 6.2.1.3 Ensure auditing for processes that start prior to auditd is enabled (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Configure grub2 so that processes that are capable of being audited can be audited even if they start up prior to auditd startup. Rationale: Audit events need to be captured on processes that start up prior to auditd , so that potential malicious activity cannot go undetected. Audit: Run the following command: # find /boot -type f -name 'grub.cfg' -exec grep -Ph -- '^\h*linux' {} + | grep -v 'audit=1' Nothing should be returned. Remediation: Edit /etc/default/grub or a file in /etc/default/grub.d/ ending in .cfg adding audit=1 to GRUB_CMDLINE_LINUX: Example: printf "\n%s\n" 'GRUB_CMDLINE_LINUX="audit=1"' >> /etc/default/grub.d/40- custom.cfg Run the following command to update the grub2 configuration: # update-grub References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 2. STIG ID: UBTU-20-010198 | RULE ID: SV-238299r991555 | CAT II 3. STIG ID: UBTU-22-212015 | RULE ID: SV-260471r991555 | CAT II Additional Information: This recommendation is designed around the grub2 bootloader, if another bootloader is in use in your environment enact equivalent settings. Page 771 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 772 Internal Only - General 6.2.1.4 Ensure audit_backlog_limit is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: In the kernel-level audit subsystem, a socket buffer queue is used to hold audit events. Whenever a new audit event is received, it is logged and prepared to be added to this queue. The kernel boot parameter audit_backlog_limit=N, with N representing the amount of messages, will ensure that a queue cannot grow beyond a certain size. If an audit event is logged which would grow the queue beyond this limit, then a failure occurs and is handled according to the system configuration Rationale: If an audit event is logged which would grow the queue beyond the audit_backlog_limit, then a failure occurs, auditd records will be lost, and potential malicious activity could go undetected. Audit: Run the following command and verify the audit_backlog_limit= parameter is set: # find /boot -type f -name 'grub.cfg' -exec grep -Ph -- '^\h*linux' {} + | grep -Pv 'audit_backlog_limit=\d+\b' Nothing should be returned. Remediation: Edit /etc/default/grub or a file in /etc/default/grub.d/ ending in .cfg adding audit_backlog_limit=N to GRUB_CMDLINE_LINUX. The recommended size for N is 8192 or larger`: Example: # printf "\n%s\n" 'GRUB_CMDLINE_LINUX="audit_backlog_limit=8192"' >> /etc/default/grub.d/40-custom.cfg Run the following command to update the grub2 configuration: # update-grub Default Value: if audit_backlog_limit is not set, the system defaults to audit_backlog_limit=64 References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 Page 773 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 774 Internal Only - General 6.2.2 Configure Data Retention When auditing, it is important to carefully configure the storage requirements for audit logs. By default, auditd will max out the log files at 5MB and retain only 4 copies of them. Older versions will be deleted. It is possible on a system that the 20 MBs of audit logs may fill up the system causing loss of audit data. While the recommendations here provide guidance, check your site policy for audit storage requirements. Page 775 Internal Only - General 6.2.2.1 Ensure audit log storage size is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Configure the maximum size of the audit log file. Once the log reaches the maximum size, it will be rotated and a new log file will be started. Rationale: It is important that an appropriate size is determined for log files so that they do not impact the system and audit data is not lost. Audit: Run the following command and ensure output is in compliance with site policy: # grep -Po -- '^\h*max_log_file\h*=\h*\d+\b' /etc/audit/auditd.conf max_log_file = Remediation: Set the following parameter in /etc/audit/auditd.conf in accordance with site policy: max_log_file = Default Value: max_log_file = 8 References: 1. NIST SP 800-53 Rev. 5: AU-8 Additional Information: The max_log_file parameter is measured in megabytes. Other methods of log rotation may be appropriate based on site policy. One example is time-based rotation strategies which don't have native support in auditd configurations. Manual audit of custom configurations should be evaluated for effectiveness and completeness. Page 776 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 777 Internal Only - General 6.2.2.2 Ensure audit logs are not automatically deleted (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The max_log_file_action setting determines how to handle the audit log file reaching the max file size. A value of keep_logs will rotate the logs but never delete old logs. Rationale: In high security contexts, the benefits of maintaining a long audit history exceed the cost of storing the audit history. Audit: Run the following command and verify output matches: # grep max_log_file_action /etc/audit/auditd.conf max_log_file_action = keep_logs Remediation: Set the following parameter in /etc/audit/auditd.conf: max_log_file_action = keep_logs References: 1. NIST SP 800-53 Rev. 5: AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 778 Internal Only - General 6.2.2.3 Ensure system is disabled when audit logs are full (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditd daemon can be configured to halt the system or put the system in single user mode, if no free space is available or an error is detected on the partition that holds the audit log files. The disk_full_action parameter tells the system what action to take when no free space is available on the partition that holds the audit log files. Valid values are ignore, syslog, rotate, exec, suspend, single, and halt. • ignore, the audit daemon will issue a syslog message but no other action is taken • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system The disk_error_action parameter tells the system what action to take when an error is detected on the partition that holds the audit log files. Valid values are ignore, syslog, exec, suspend, single, and halt. • ignore, the audit daemon will not take any action • syslog, the audit daemon will issue no more than 5 consecutive warnings to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system Rationale: In high security contexts, the risk of detecting unauthorized access or nonrepudiation exceeds the benefit of the system's availability. Page 779 Internal Only - General Impact: disk_full_action parameter: • Set to halt - the auditd daemon will shutdown the system when the disk partition containing the audit logs becomes full. • Set to single - the auditd daemon will put the computer system in single user mode when the disk partition containing the audit logs becomes full. disk_error_action parameter: • Set to halt - the auditd daemon will shutdown the system when an error is detected on the partition that holds the audit log files. • Set to single - the auditd daemon will put the computer system in single user mode when an error is detected on the partition that holds the audit log files. • Set to syslog - the auditd daemon will issue no more than 5 consecutive warnings to syslog when an error is detected on the partition that holds the audit log files. Audit: Run the following command and verify the disk_full_action is set to either halt or single: # grep -Pi -- '^\h*disk_full_action\h*=\h*(halt|single)\b' /etc/audit/auditd.conf disk_full_action = Run the following command and verify the disk_error_action is set to syslog, single, or halt: # grep -Pi -- '^\h*disk_error_action\h*=\h*(syslog|single|halt)\b' /etc/audit/auditd.conf disk_error_action = Remediation: Set one of the following parameters in /etc/audit/auditd.conf depending on your local security policies. disk_full_action = disk_error_action = Example: disk_full_action = halt disk_error_action = halt References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-8, AU-12, SI-5 2. AUDITD.CONF(5) Page 780 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. Page 781 Internal Only - General 6.2.2.4 Ensure system warns when audit logs are low on space (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditd daemon can be configured to halt the system, put the system in single user mode or send a warning message, if the partition that holds the audit log files is low on space. The space_left_action parameter tells the system what action to take when the system has detected that it is starting to get low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt. • ignore, the audit daemon does nothing • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • email, the audit daemon will send a warning to the email account specified in action_mail_acct as well as sending the message to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system The admin_space_left_action parameter tells the system what action to take when the system has detected that it is low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt. • ignore, the audit daemon does nothing • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • email, the audit daemon will send a warning to the email account specified in action_mail_acct as well as sending the message to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system Page 782 Internal Only - General Rationale: In high security contexts, the risk of detecting unauthorized access or nonrepudiation exceeds the benefit of the system's availability. Impact: If the admin_space_left_action is set to single the audit daemon will put the computer system in single user mode. Audit: Run the following command and verify the space_left_action is set to email, exec, single, or halt: # grep -P -- '^\h*space_left_action\h*=\h*(email|exec|single|halt)\b' /etc/audit/auditd.conf Verify the output is email, exec, single, or halt Example output space_left_action = email Run the following command and verify the admin_space_left_action is set to single - OR - halt: # grep -P -- '^\h*admin_space_left_action\h*=\h*(single|halt)\b' /etc/audit/auditd.conf Verify the output is single or halt Example output: admin_space_left_action = single Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email Remediation: Set the space_left_action parameter in /etc/audit/auditd.conf to email, exec, single, or halt: Example: space_left_action = email Set the admin_space_left_action parameter in /etc/audit/auditd.conf to single or halt: Example: admin_space_left_action = single Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-8, AU-12, SI-5 2. AUDITD.CONF(5) Page 783 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 784 Internal Only - General 6.2.3 Configure auditd Rules The Audit system operates on a set of rules that define what is to be captured in the log files. The following types of Audit rules can be specified: • Control rules: Allow the Audit system's behavior and some of its configuration to be modified. • File system rules: Allow the auditing of access to a particular file or a directory (Also known as file watches). The syntax of these watch rules generally follow this format: -a always,exit - F arch=b64 -F path=path-to-file -F perm=permissions -F key=keyname • System call rules: Allow logging of system calls that any specified program makes. Syscall rules take the general form of: -a action,list -S syscall -F field=value -k keyname Audit rules can be set: • On the command line using the auditctl utility, these rules are not persistent across reboots. • In a file ending in .rules in the /etc/audit/rules.d/ directory. Note: • The rule must start with -a always,exit • The arch= field e.g. arch=b64 is optional but strongly recommended for best performance. b64 is used in the example, but the arch can also be what is on your system (x86_64, aarch64, ppc64le, s390x, etc). • The field -S all will be added by auditctl if it is not included in the rule. • The rule must include the path= field shown in the example output. • The rule must include the perm= field shown in the example output. The options e.g. wa may include additional options e.g. rwxa • The key= field e.g. key=scope is optional but strongly recommended. Though the name scope is used in the example, this can be set to any name. • The -w option e.g. -w /etc/sudoers -p wa -k scope is deprecated. While the deprecated -w is in a "passing" state, it is recommended to update the rule in accordance with the Remediation Procedure as the -w will soon be unsupported. The following script creates and runs a function called f_audit_rules_format_chk that may be used to determine if audit rules have deprecated -w format or missing arch= option: Page 785 Internal Only - General #!/usr/bin/env bash f_audit_rules_format_chk() { rules_dir="/etc/audit/rules.d" deprecated_flag="-w" a_output=() for file in "$rules_dir"/*rules; do [[ -e "$file" ]] || continue while IFS= read -r line; do # Skip empty or commented lines [[ "$line" =~ ^\s*# ]] || [[ -z "$line" ]] && continue # Check for deprecated -w if [[ "$line" == *"$deprecated_flag"* ]]; then a_output+=("Deprecated '-w' found in $file Rule: $(wrap_text "$line") Flag: $deprecated_flag") fi # Check for missing -F arch if [[ "$line" =~ ^-a[[:space:]]+always,exit ]] && [[ "$line" != *"-F arch="* ]] \ ; then a_output+=("Missing '-F arch=' in $file Rule: $(wrap_text "$line") Flag: Missing arch") fi done < "$file" done if [ ${#a_output[@]} -eq 0 ]; then echo -e "No issues found in audit rules files" else echo -e "\nAudit rules issue detected:" for output in "${a_output[@]}"; do echo -e "\n$output" done fi } # wrap_text function for formatting wrap_text() { echo "$1" } f_audit_rules_format_chk Page 786 Internal Only - General 6.2.3.1 Ensure modification of the /etc/sudoers file is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor scope changes for system administrators. If the system has been properly configured to force system administrators to log in as themselves first and then use the sudo command to execute privileged commands, it is possible to monitor changes in scope. The file /etc/sudoers, or files in /etc/sudoers.d, will be written to when the file(s) or related attributes have changed. The audit records will be tagged with the identifier "scope". Rationale: Changes in the /etc/sudoers and /etc/sudoers.d files can indicate that an unauthorized change has been made to the scope of system administrator activity. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, CCI-002884, SRG-OS-000466-GPOS-00210, SRG-OS-000476-GPOS-00221 Audit: Note: The -w option e.g. -w /etc/sudoers -p wa -k scope is deprecated and the rule should be updated in accordance with the Remediation Procedure 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/sudoers' Verify output includes: -a always,exit -F path=/etc/sudoers -F perm=wa -a always,exit -F dir=/etc/sudoers.d -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/sudoers' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-scope.rules:-a always,exit -F arch=b64 -S all -F path=/etc/sudoers -F perm=wa -k scope /etc/audit/rules.d/50-scope.rules:-a always,exit -F arch=b64 -S all -F dir=/etc/sudoers.d -F perm=wa -k scope Page 787 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor scope changes for system administrators. Example: # printf '%s\n' " -a always,exit -F arch=b64 -S all -F path=/etc/sudoers -F perm=wa -k scope -a always,exit -F arch=b64 -S all -F dir=/etc/sudoers.d -F perm=wa -k scope " >> /etc/audit/rules.d/50-scope.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030171 | RULE ID: SV-230409r627750 | CAT II 4. STIG ID: RHEL-08-030172 | RULE ID: SV-230410r627750 | CAT II 5. STIG ID: RHEL-09-654215 | RULE ID: SV-258217r1045436 | CAT II 6. STIG ID: RHEL-09-654220 | RULE ID: SV-258218r1045439 | CAT II 7. STIG ID: ALMA-09-004970 | RULE ID: SV-269129r1050011 | CAT II 8. STIG ID: ALMA-09-006070 | RULE ID: SV-269135r1050017 | CAT II 9. STIG ID: UBTU-22-654220 | RULE ID: SV-260646r991575 | CAT II 10. STIG ID: UBTU-22-654225 | RULE ID: SV-260647r991575 | CAT II 11. STIG ID: UBTU-24-900510 | RULE ID: SV-270807r1066910 | CAT II 12. STIG ID: UBTU-24-900520 | RULE ID: SV-270808r1067100 | CAT II Page 788 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 789 Internal Only - General 6.2.3.2 Ensure actions as another user are always logged (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: sudo provides users with temporary elevated privileges to perform operations, either as the superuser or another user. Rationale: Creating an audit log of users with temporary elevated privileges and the operation(s) they performed is essential to reporting. Administrators will want to correlate the events written to the audit trail with the records written to sudo's logfile to verify if unauthorized commands have been executed. Satisfies: SRG-OS-000326-GPOS-00126, SRG-OS-000327-GPOS-00127 Audit: Note: • The deprecated -w format which allows for backwards compatibility at the expense of system performance is in a "passing" state. However, it is recommended to update the rule in accordance with the Remediation Procedure as the -w will soon be unsupported. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep execve Verify the output includes: -a always,exit -C euid!=uid -F auid!=unset -S execve 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'execve' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-user_emulation.rules:-a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation Page 790 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor elevated privileges. Example: # printf " -a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation " >> /etc/audit/rules.d/50-user_emulation.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Revision 5 :: AC-6 (8) 2. https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/10/html/cons iderations_in_adopting_rhel_10/architectures 3. STIG ID: RHEL-08-030000 | RULE ID: SV-230386r854037 | CAT II 4. STIG ID: RHEL-09-654010 | RULE ID: SV-258176r1045313 | CAT II 5. STIG ID: ALMA-09-007280 | RULE ID: SV-269146r1050028 | CAT II 6. STIG ID: UBTU-22-654230 | RULE ID: SV-260648r958730 | CAT II 7. STIG ID: UBTU-24-200580 | RULE ID: SV-270689r1066556 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 791 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. Page 792 Internal Only - General 6.2.3.3 Ensure events that modify the sudo log file are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the sudo log file. If the system has been properly configured to disable the use of the su command and force all administrators to have to log in first and then use sudo to execute privileged commands, then all administrator commands will be logged to /var/log/sudo.log . Any time a command is executed, an audit event will be triggered as the /var/log/sudo.log file will be opened for write and the executed administration command will be written to the log. Rationale: Changes in /var/log/sudo.log indicate that an administrator has executed a command or the log file itself has been tampered with. Administrators will want to correlate the events written to the audit trail with the records written to /var/log/sudo.log to verify if unauthorized commands have been executed. Audit: Note: • This recommendation requires that the sudo logfile is configured. For additional information see guidance provided in the recommendation "Ensure sudo log file exists" 1. Run the following command to verify that sudo has a custom log file configured: # grep -rPsi "^\h*Defaults\h+([^#]+,\h*)?logfile\h*=\h*(\"|\')?\H+(\"|\')?(,\h*\H+\h*)*\h* (#.*)?$" /etc/sudoers* Example output: Defaults logfile="/var/log/sudo.log" 2. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'sudo.log' Verify the output includes: -a always,exit -F path=/var/log/sudo.log -F perm=wa 3. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'sudo.log' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-sudo.rules: -a always,exit -F arch=b64 -S all -F path=/var/log/sudo.log -F perm=wa -k sudo_log_file Page 793 Internal Only - General Remediation: Note: • This recommendation requires that the sudo logfile is configured. For additional information see guidance provided in the recommendation "Ensure sudo log file exists". • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit the file /etc/sudoers or a file in /etc/sudoers.d/ with visudo -f and add the following line: Defaults logfile="" Example: Defaults logfile="/var/log/sudo.log" 2. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the sudo log file. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/var/log/sudo.log -F perm=wa -k sudo_log_file " >> /etc/audit/rules.d/50-sudo.rules Note: path= should be set to the same sudo log file location as configured above in step 1. 3. Merge and load the rules into active configuration: # augenrules --load 4. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. STIG ID: UBTU-22-654235 | RULE ID: SV-260649r986298 | CAT II 2. STIG ID: UBTU-24-500010 | RULE ID: SV-270740r1066709 | CAT II Page 794 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. Page 795 Internal Only - General 6.2.3.4 Ensure events that modify date and time information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Capture events where the system date and/or time has been modified. The parameters in this section are set to determine if the; • adjtimex - tune kernel clock • settimeofday - set time using timeval and timezone structures • stime - using seconds since 1/1/1970 • clock_settime - allows for the setting of several internal clocks and timers system calls have been executed. Further, ensure to write an audit record to the configured audit log file upon exit, tagging the records with a unique identifier such as "time-change". Rationale: Unexpected changes in system date and/or time could be a sign of malicious activity on the system. Page 796 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. Run the following command to verify a rule exits in the running configuration: 1a. Verify a rule exists for adjtimex, settimeofday, clock_settime in the running configuration: # auditctl -l | grep -Ps -- '(adjtimex|settimeofday|clock_settime)' Verify output of matches: -a always,exit -S adjtimex,settimeofday -a always,exit -S clock_settime -F a0=0x0 1b. verify a rule for time-change exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/localtime' Verify the output matches: -a always,exit -F path=/etc/localtime -F perm=wa Run the following command to verify a rule exists in a rules file: 2a. Run the following command to verify a rule exists for adjtimex, settimeofday, clock_settime in a rules file: # grep -Ps -- '(adjtimex|settimeofday|clock_settime)' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-time-change.rules:-a always,exit -F arch=b64 -S adjtimex,settimeofday -k time-change /etc/audit/rules.d/50-time-change.rules:-a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -k time-change 2b. Run the following command to verify a rule exists for /etc/localtime in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/localtime' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-time-change.rules:-a always,exit -F arch=b64 -S all -F path=/etc/localtime -F perm=wa -k localtime-change Page 797 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify date and time information. 1a. Create a rule for adjtimex, settimeofday, clock_settime: Example # printf " -a always,exit -F arch=b64 -S adjtimex,settimeofday -k time-change -a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -k time-change " >> /etc/audit/rules.d/50-time-change.rules 1b. Create a rule for /etc/localtime: Example # printf " -a always,exit -F arch=b64 -S all -F path=/etc/localtime -F perm=wa -k localtime-change " >> /etc/audit/rules.d/50-local-time-change.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 798 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 799 Internal Only - General 6.2.3.5 Ensure events that modify sethostname and setdomainname are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The below parameters monitors the following system calls, and write an audit event on system call exit: • sethostname - set the systems host name • setdomainname - set the systems domain name Rationale: Monitoring sethostname and setdomainname will identify potential unauthorized changes to host and domain name of a system. The changing of these names could potentially break security parameters that are set based on those names. Audit: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'sethostname|setdomainname' Verify the output matches: -a always,exit -S sethostname,setdomainname 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'sethostname|setdomainname' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-system_locale.rules:-a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale Page 800 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale " >> /etc/audit/rules.d/50-system_locale.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 801 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 802 Internal Only - General 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The files being monitored are: • /etc/issue and /etc/issue.net - messages displayed pre-login Rationale: Monitoring /etc/issue and /etc/issue.net is important, as intruders could put disinformation into those files and trick users into providing information to the intruder. Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/issue' Verify the output includes: -a always,exit -F path=/etc/issue -F perm=wa -a always,exit -F path=/etc/issue.net -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/issue' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-etc_issue_system_locale.rules:-a always,exit -F arch=b64 -S all -F path=/etc/issue -F perm=wa -k system-locale /etc/audit/rules.d/50-etc_issue_system_locale.rules:-a always,exit -F arch=b64 -S all -F path=/etc/issue.net -F perm=wa -k system-locale Page 803 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/issue -F perm=wa -k system- locale -a always,exit -F arch=b64 -S all -F path=/etc/issue.net -F perm=wa -k system-locale " >> /etc/audit/rules.d/50-etc_issue_system_locale.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 804 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 805 Internal Only - General 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The files being monitored are: • /etc/hosts - file containing host names and associated IP addresses • /etc/hostname - file contains the system's host name Rationale: The /etc/hosts file is monitored for changes that can indicate an unauthorized intruder is trying to change machine associations with IP addresses and trick users and processes into connecting to unintended machines. Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/host' Verify the output includes: -a always,exit -F path=/etc/hosts -F perm=wa -a always,exit -F path=/etc/hostname -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/host' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-etc_host_system_locale.rules:-a always,exit -F arch=b64 -S all -F path=/etc/hosts -F perm=wa -k system-locale /etc/audit/rules.d/50-etc_host_system_locale.rules:-a always,exit -F arch=b64 -S all -F path=/etc/hostname -F perm=wa -k system-locale Page 806 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/hosts -F perm=wa -k system- locale -a always,exit -F arch=b64 -S all -F path=/etc/hostname -F perm=wa -k system- locale " >> /etc/audit/rules.d/50-etc_host_system_locale.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 807 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 808 Internal Only - General 6.2.3.8 Ensure events that modify the system's network environment are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The files being monitored are: • /etc/network/interfaces - This file describes the network interfaces available on your system # and how to activate them. • /etc/network/interfaces.d/ - directory containing network interface scripts and configurations files • /etc/netplan/ - central location for YAML networking configurations files Rationale: Monitoring the systems network environment is important as it can show if network interfaces or scripts are being modified in a way that can lead to the machine becoming unavailable or compromised. All audit records should have a relevant tag associated with them. Page 809 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '\/etc/net' Verify the output includes: -a always,exit -F path=/etc/network/interfaces -F perm=wa -a always,exit -F dir=/etc/network/interfaces.d -F perm=wa -a always,exit -F dir=/etc/netplan/ -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '\/etc/net' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-etc_sysconfig_system_locale.rules:-a always,exit -F arch=b64 -S all -F path=/etc/network/interfaces -F perm=wa -k system-locale /etc/audit/rules.d/50-etc_sysconfig_system_locale.rules:-a always,exit -F arch=b64 -S all -F dir=/etc/network/interfaces.d -F perm=wa -k system-locale /etc/audit/rules.d/50-etc_sysconfig_system_locale.rules:-a always,exit -F arch=b64 -S all -F dir=/etc/netplan/ -F perm=wa -k system-locale Page 810 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/network/interfaces -F perm=wa -k system-locale -a always,exit -F arch=b64 -S all -F dir=/etc/network/interfaces.d -F perm=wa -k system-locale -a always,exit -F arch=b64 -S all -F dir=/etc/netplan/ -F perm=wa -k system- locale " >> /etc/audit/rules.d/50-etc_sysconfig_system_locale.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 811 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 812 Internal Only - General 6.2.3.9 Ensure events that modify /etc/NetworkManager directory are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The files being monitored are: • /etc/NetworkManager/ - directory contains configuration files and settings used by the NetworkManager Rationale: Monitoring the /etc/NetworkManager/ directory will identify potential unauthorized changes to network configuration files. Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '\/etc/NetworkManager' Verify the output includes: -a always,exit -F dir=/etc/NetworkManager/ -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '\/etc\/NetworkManager' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-etc_NetworkManager_system_locale.rules:-a always,exit - F arch=b64 -S all -F dir=/etc/NetworkManager/ -F perm=wa -k system-locale Page 813 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S all -F dir=/etc/NetworkManager/ -F perm=wa -k system-locale " >> /etc/audit/rules.d/50-etc_NetworkManager_system_locale.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 814 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 815 Internal Only - General 6.2.3.10 Ensure use of privileged commands are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor privileged programs, those that have the setuid and/or setgid bit set on execution, to determine if unprivileged users are running these commands. Rationale: Execution of privileged commands by non-privileged users could be an indication of someone trying to gain unauthorized access to the system. Impact: Both the audit and remediation section of this recommendation will traverse all mounted file systems that is not mounted with either noexec or nosuid mount options. If there are large file systems without these mount options, such traversal will be significantly detrimental to the performance of the system. Before running either the audit or remediation section, inspect the output of the following command to determine exactly which file systems will be traversed: # findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" To exclude a particular file system due to adverse performance impacts, update the audit and remediation sections by adding a sufficiently unique string to the grep statement. The above command can be used to test the modified exclusions. Page 816 Internal Only - General Audit: On disk configuration Run the following script to check on disk rules: #!/usr/bin/env bash { for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do for PRIVILEGED in $(find "${PARTITION}" -xdev -perm /6000 -type f); do grep -qr "${PRIVILEGED}" /etc/audit/rules.d && printf "OK: '${PRIVILEGED}' found in auditing rules.\n" || printf "Warning: '${PRIVILEGED}' not found in on disk configuration.\n" done done } Verify that all output is OK. Running configuration Run the following script to check loaded rules: #!/usr/bin/env bash { RUNNING=$(auditctl -l) [ -n "${RUNNING}" ] && for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do for PRIVILEGED in $(find "${PARTITION}" -xdev -perm /6000 -type f); do printf -- "${RUNNING}" | grep -q "${PRIVILEGED}" && printf "OK: '${PRIVILEGED}' found in auditing rules.\n" || printf "Warning: '${PRIVILEGED}' not found in running configuration.\n" done done \ || printf "ERROR: Variable 'RUNNING' is unset.\n" } Verify that all output is OK. Special mount points If there are any special mount points that are not visible by default from findmnt as per the above audit, said file systems would have to be manually audited. Page 817 Internal Only - General Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor the use of privileged commands. Example script: #!/usr/bin/env bash { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) AUDIT_RULE_FILE="/etc/audit/rules.d/50-privileged.rules" NEW_DATA=() for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do readarray -t DATA < <(find "${PARTITION}" -xdev -perm /6000 -type f | awk -v UID_MIN=${UID_MIN} '{print "-a always,exit -F arch=b64 -S all -F path=" $1 " -F perm=x -F auid>="UID_MIN" -F auid!=unset -k privileged" }') for ENTRY in "${DATA[@]}"; do NEW_DATA+=("${ENTRY}") done done readarray &> /dev/null -t OLD_DATA < "${AUDIT_RULE_FILE}" COMBINED_DATA=( "${OLD_DATA[@]}" "${NEW_DATA[@]}" ) printf '%s\n' "${COMBINED_DATA[@]}" | sort -u > "${AUDIT_RULE_FILE}" } Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Special mount points If there are any special mount points that are not visible by default from just scanning /, change the PARTITION variable to the appropriate partition and re-run the remediation. References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-3(1) Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 818 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 819 Internal Only - General 6.2.3.11 Ensure unsuccessful file access attempts are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor for unsuccessful attempts to access files. The following parameters are associated with system calls that control files: • creation - creat • opening - open , openat • truncation - truncate , ftruncate An audit log record will only be written if all of the following criteria is met for the user when trying to access a file: • a non-privileged user (auid>=``UID_MIN) • is not a Daemon event (auid=``4294967295/unset/-1) • if the system call returned EACCES (permission denied) or EPERM (some other permanent error associated with the specific system call) Rationale: Failed attempts to open, create or truncate files could be an indication that an individual or process is trying to gain unauthorized access to the system. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033 Page 820 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify UID_MIN is set in /etc/login.defs # awk '/^\s*UID_MIN/{print $2}' /etc/login.defs Example output: 1000 2. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '(EACCES|EPERM)' Verify the output matches: -a always,exit -S creat,open,openat,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -a always,exit -S creat,open,openat,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset 3. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '(EACCES|EPERM)' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-access.rules:-a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k access /etc/audit/rules.d/50-access.rules:-a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k access Page 821 Internal Only - General Remediation: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Edit the /etc/login.defs file and create or add the UID_MIN setting. Example UID_MIN 1000 2. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor unsuccessful file access attempts. Example: # printf " -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EACCES -F auid>=1000 -F auid!=unset -k access -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EPERM -F auid>=1000 -F auid!=unset -k access " >> /etc/audit/rules.d/50-access.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 3. Merge and load the rules into active configuration: # augenrules --load 4. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030420 | RULE ID: SV-230449r810455 | CAT II 4. STIG ID: RHEL-09-654070 | RULE ID: SV-258188r1045349 | CAT II 5. STIG ID: ALMA-09-048090 | RULE ID: SV-269475r1050358 | CAT II 6. STIG ID: UBTU-22-654165 | RULE ID: SV-260635r958446 | CAT II 7. STIG ID: UBTU-24-900160 | RULE ID: SV-270787r1068378 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 822 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 823 Internal Only - General 6.2.3.12 Ensure events that modify /etc/group information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/group - system groups Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/group' Verify the output includes: -a always,exit -F path=/etc/group -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/group' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/group -F perm=wa -k identity Page 824 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/group -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) 5. STIG ID: RHEL-08-030170 | RULE ID: SV-230408r1017214 | CAT II 6. STIG ID: RHEL-09-654225 | RULE ID: SV-258227r1014992 | CAT II 7. STIG ID: ALMA-09-005080 | RULE ID: SV-269129r1050011 | CAT II 8. STIG ID: UBTU-22-654130 | RULE ID: SV-260628r958368 | CAT II 9. STIG ID: UBTU-24-200290 | RULE ID: SV-270685r1066544 | CAT II Page 825 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 826 Internal Only - General 6.2.3.13 Ensure events that modify /etc/passwd information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/passwd - system users Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/passwd' Verify the output includes: -a always,exit -F path=/etc/passwd -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/passwd' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/passwd -F perm=wa -k identity Page 827 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/passwd -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) 5. STIG ID: RHEL-08-030150 | RULE ID: SV-230406r1017212 | CAT II 6. STIG ID: RHEL-09-654240 | RULE ID: SV-258230r958408 | CAT II 7. STIG ID: ALMA-09-005410 | RULE ID: SV-269133r1050015 | CAT II 8. STIG ID: UBTU-22-654145 | RULE ID:SV-260631r958368 | CAT II 9. STIG ID: UBTU-24-200280| RULE ID: SV-270684r1066541 | CAT II Page 828 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 829 Internal Only - General 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/gshadow - encrypted password for each group • /etc/shadow - system user passwords Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Page 830 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*shadow' Verify the output includes: -a always,exit -F path=/etc/gshadow -F perm=wa -a always,exit -F path=/etc/shadow -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'shadow' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/gshadow -F perm=wa -k identity /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/shadow -F perm=wa -k identity Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/gshadow -F perm=wa -k identity -a always,exit -F arch=b64 -S all -F path=/etc/shadow -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Page 831 Internal Only - General References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) 5. STIG ID: RHEL-08-030130 | RULE ID: SV-230404r1017210 | CAT II 6. STIG ID: RHEL-09-654245 | RULE ID: SV-258231r1069375 | CAT II 7. STIG ID: ALMA-09-005960 | RULE ID: SV-269134r1050016 | CAT II 8. STIG ID: UBTU-22-654150 | RULE ID: SV-260632r958368 | CAT II 9. STIG ID: UBTU-24-200300 | RULE ID: SV-270686r1066547 | CAT II 10. STIG ID: RHEL-08-030160 | RULE ID: SV-230407r1017213 | CAT II 11. STIG ID: RHEL-09-654230 | RULE ID: SV-258228r991572 | CAT II 12. STIG ID: ALMA-09-005190 | RULE ID: SV-269131r1050013 | CAT II 13. STIG ID: UBTU-22-654135 | RULE ID: SV-260629r958368 | CAT II 14. STIG ID: UBTU-24-200310 | RULE ID: SV-270687r1066550 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 832 Internal Only - General 6.2.3.15 Ensure events that modify /etc/security/opasswd are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/security/opasswd - storage of old passwords if the relevant PAM module is in use Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/security\/opasswd' Verify the output includes: -a always,exit -F path=/etc/security/opasswd -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/security\/opasswd' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/security/opasswd -F perm=wa -k identity Page 833 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/security/opasswd -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) 5. STIG ID: RHEL-08-030140| RULE ID: SV-230405r1017211 | CAT II 6. STIIG ID: RHEL-09-654235 | RULE ID: SV-258229r958434 | CAT II 7. STIG ID: ALMA-09-005300 | RULE ID: SV-269132r1050014 | CAT II 8. STIG ID: UBTU-22-654140 | RULE ID: SV-260630r958368 | CAT II 9. STIG ID: UBTU-24-200320 | RULE ID: SV-270688r1066553 | CAT II Page 834 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 835 Internal Only - General 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/nsswitch.conf - file configures how the system uses various databases and name resolution mechanisms Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/nsswitch.conf' Verify the output includes: -a always,exit -F path=/etc/nsswitch.conf -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'nsswitch.conf' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/nsswitch.conf -F perm=wa -k identity Page 836 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/nsswitch.conf -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 837 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 838 Internal Only - General 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/ information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/pam.conf - file determines the authentication services to be used, and the order in which the services are used. • /etc/pam.d - directory contains the PAM configuration files for each PAM-aware application. Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000004-GPOS-00004, SRG-OS- 000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462- GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG- OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS- 00091, SRG-OS-000303-GPOS-00120, SRG-OS-000304-GPOS-00121, SRG-OS- 000476-GPOS-00221 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/pam' Verify the output includes: -a always,exit -F path=/etc/pam.conf -F perm-wa -a always,exit -F dir=/etc/pam.d -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/etc\/pam' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F path=/etc/pam.conf -F perm-wa -k identity /etc/audit/rules.d/50-identity.rules:-a always,exit -F arch=b64 -S all -F dir=/etc/pam.d -F perm=wa -k identity Page 839 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/pam.conf -F perm=wa -k identity -a always,exit -F arch=b64 -S all -F dir=/etc/pam.d -F perm=wa -k identity " >> /etc/audit/rules.d/50-identity.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 2. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es 3. NIST SP 800-53 :: AU-12 a 4. NIST SP 800-53A :: AU-12.1 (ii) Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 840 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 841 Internal Only - General 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2 are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor changes to file permissions, attributes, ownership and group. The parameters in this section track changes for system calls that affect file permissions and attributes. The following commands and system calls effect the permissions, ownership and various attributes of files. • chmod: changes the mode of the file • fchmod: changes the mode of the file referred to by the open file descriptor • fchmodat: change permissions of a file • fchmodat2: change permissions of a file relative to a directory file descriptor In all cases, an audit record will only be written for non-system user ids and will ignore Daemon events. All audit records will be tagged with the identifier "perm_mod." Rationale: Monitoring for changes in file attributes could alert a system administrator to activity that could indicate intruder activity or policy violation. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466- GPOS-00210 Page 842 Internal Only - General Audit: Note: • Output showing all audited syscalls, e.g. (-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chmod,fchmod,fchmodat,fchmodat2,setxattr,ls etxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod) is also acceptable. These have been separated by function on the displayed output for clarity. • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exits in the running configuration # auditctl -l | grep -Ps -- 'chmod' Verify the output includes: -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,fchmodat2 -F auid>=1000 - F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'chmod' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_mod.rules:-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,fchmodat2 -F auid>=1000 -F auid!=-1 -k perm_mod Page 843 Internal Only - General Remediation: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor discretionary access control permission modification events. Example: # printf " -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,fchmodat2 -F auid>=1000 - F auid!=unset -k perm_mod " >> /etc/audit/rules.d/50-perm_mod.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030490 | RULE ID: SV-230456r810462 | CAT II 4. STIG ID: RHEL-08-030200 | RULE ID: SV-230413r810463 | CAT II 5. STIG ID: RHEL-09-654015 | RULE ID: SV-258177r1045316 | CAT II 6. STIG ID: RHEL-09-654025 | RULE ID: SV-258179r1045322 | CAT II 7. STIG ID: ALMA-09-048640 | RULE ID: SV-269480r1050363 | CAT II 8. STIG ID: ALMA-09-051390 | RULE ID: SV-269505r1050388 | CAT II 9. STIG ID: UBTU-22-654160 | RULE ID: SV-260634r958446 | CAT II 10. STIG ID: UBTU-22-654180 | RULE ID: SV-260638r958446 | CAT II 11. STIG ID: UBTU-24-900140 | RULE ID: SV-270785r1068373 | CAT II 12. STIG ID: UBTU-24-900130 | RULE ID: SV-270784r1068371 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 844 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 845 Internal Only - General 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor changes to file permissions, attributes, ownership and group. The parameters in this section track changes for system calls that affect file permissions and attributes. The following commands and system calls effect the permissions, ownership and various attributes of files. • chown: changes the user and/or group ownership of each given file • fchown: changes the ownership of the file referred to by the open file descriptor • fchownat: change ownership of a file relative to a directory file descriptor • lchown: change the owner and group of a file In all cases, an audit record will only be written for non-system user ids and will ignore Daemon events. All audit records will be tagged with the identifier "perm_mod." Rationale: Monitoring for changes in file attributes could alert a system administrator to activity that could indicate intruder activity or policy violation. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466- GPOS-00210 Page 846 Internal Only - General Audit: Note: • Output showing all audited syscalls, e.g. (-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chmod,fchmod,fchmodat,setxattr,lsetxattr,fs etxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod) is also acceptable. These have been separated by function on the displayed output for clarity. • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exits in the running configuration # auditctl -l | grep -Ps -- 'chown' Verify the output includes: -a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'chown' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_mod.rules:-a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=-1 -k perm_mod Page 847 Internal Only - General Remediation: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor discretionary access control permission modification events. Example: # printf " -a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=unset -k perm_mod " >> /etc/audit/rules.d/50-perm_mod.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030490 | RULE ID: SV-230456r810462 | CAT II 4. STIG ID: RHEL-08-030200 | RULE ID: SV-230413r810463 | CAT II 5. STIG ID: RHEL-09-654015 | RULE ID: SV-258177r1045316 | CAT II 6. STIG ID: RHEL-09-654025 | RULE ID: SV-258179r1045322 | CAT II 7. STIG ID: ALMA-09-048640 | RULE ID: SV-269480r1050363 | CAT II 8. STIG ID: ALMA-09-051390 | RULE ID: SV-269505r1050388 | CAT II 9. STIG ID: UBTU-22-654160 | RULE ID: SV-260634r958446 | CAT II 10. STIG ID: UBTU-22-654180 | RULE ID: SV-260638r958446 | CAT II 11. STIG ID: UBTU-24-900140 | RULE ID: SV-270785r1068373 | CAT II 12. STIG ID: UBTU-24-900130 | RULE ID: SV-270784r1068371 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 848 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 849 Internal Only - General 6.2.3.20 Ensure discretionary access control permission modification events setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor changes to file permissions, attributes, ownership and group. The parameters in this section track changes for system calls that affect file permissions and attributes. The following commands and system calls effect the permissions, ownership and various attributes of files. • setxattr • lsetxattr • fsetxattr • removexattr • lremovexattr • fremovexattr In all cases, an audit record will only be written for non-system user ids and will ignore Daemon events. All audit records will be tagged with the identifier "perm_mod." Rationale: Monitoring for changes in file attributes could alert a system administrator to activity that could indicate intruder activity or policy violation. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466- GPOS-00210 Page 850 Internal Only - General Audit: Note: • Output showing all audited syscalls, e.g. (-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chmod,fchmod,fchmodat,setxattr,lsetxattr,fs etxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod) is also acceptable. These have been separated by function on the displayed output for clarity. • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exits in the running configuration # auditctl -l | grep -Ps -- 'xattr' Verify the output includes: -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'xattr' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_mod.rules:-a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=-1 -k perm_mod Page 851 Internal Only - General Remediation: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor discretionary access control permission modification events. Example: # printf " -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod " >> /etc/audit/rules.d/50-perm_mod.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030490 | RULE ID: SV-230456r810462 | CAT II 4. STIG ID: RHEL-08-030200 | RULE ID: SV-230413r810463 | CAT II 5. STIG ID: RHEL-09-654015 | RULE ID: SV-258177r1045316 | CAT II 6. STIG ID: RHEL-09-654025 | RULE ID: SV-258179r1045322 | CAT II 7. STIG ID: ALMA-09-048640 | RULE ID: SV-269480r1050363 | CAT II 8. STIG ID: ALMA-09-051390 | RULE ID: SV-269505r1050388 | CAT II 9. STIG ID: UBTU-22-654160 | RULE ID: SV-260634r958446 | CAT II 10. STIG ID: UBTU-22-654180 | RULE ID: SV-260638r958446 | CAT II 11. STIG ID: UBTU-24-900140 | RULE ID: SV-270785r1068373 | CAT II 12. STIG ID: UBTU-24-900130 | RULE ID: SV-270784r1068371 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 852 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 853 Internal Only - General 6.2.3.21 Ensure successful file system mounts are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the use of the mount system call. The mount (and umount ) system call controls the mounting and unmounting of file systems. The parameters below configure the system to create an audit record when the mount system call is used by a non- privileged user Rationale: It is highly unusual for a non privileged user to mount file systems to the system. While tracking mount commands gives the system administrator evidence that external media may have been mounted (based on a review of the source of the mount and confirming it's an external media type), it does not conclusively indicate that data was exported to the media. System administrators who wish to determine if data were exported, would also have to track successful open, creat and truncate system calls requiring write access to a file under the mount point of the external media file system. This could give a fair indication that a write occurred. The only way to truly prove it, would be to track successful writes to the external media. Tracking write system calls could quickly fill up the audit log and is not recommended. Recommendations on configuration options to track data export to media is beyond the scope of this document. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215 Page 854 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exits in the running configuration: # auditctl -l | grep -Ps -- '\-S mount' Verify the output matches: -a always,exit -S mount -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '\-S mount' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-mounts.rules:-a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=-1 -k mounts Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1.Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful file system mounts. Example: # printf " -a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=unset -k mounts " >> /etc/audit/rules.d/50-mounts.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Page 855 Internal Only - General References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030302 | RULE ID: SV-230425r627750 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 856 Internal Only - General 6.2.3.22 Ensure session initiation information is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor session initiation events. The parameters in this section track changes to the files associated with session events. • /var/run/utmp - tracks all currently logged in users. • /var/log/wtmp - file tracks logins, logouts, shutdown, and reboot events. • /var/log/btmp - keeps track of failed login attempts and can be read by entering the command /usr/bin/last -f /var/log/btmp. All audit records will be tagged with the identifier "session." Rationale: Monitoring these files for changes could alert a system administrator to logins occurring at unusual hours, which could indicate intruder activity (i.e. a user logging in at a time when they do not normally log in). Page 857 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '(\/var\/run\/utmp|\/var\/log\/wtmp|\/var\/log\/btmp)' Verify the output matches: -a always,exit -F path=/var/run/utmp -F perm=wa -a always,exit -F path=/var/log/wtmp -F perm=wa -a always,exit -F path=/var/log/btmp -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '(\/var\/run\/utmp|\/var\/log\/wtmp|\/var\/log\/btmp)' /etc/audit/rules.d/*.rules Verify the output matches: /etc/audit/rules.d/50-session.rules:-a always,exit -F arch=b64 -S all -F path=/var/run/utmp -F perm=wa -k session /etc/audit/rules.d/50-session.rules:-a always,exit -F arch=b64 -S all -F path=/var/log/wtmp -F perm=wa -k session /etc/audit/rules.d/50-session.rules:-a always,exit -F arch=b64 -S all -F path=/var/log/btmp -F perm=wa -k session Page 858 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor session initiation information. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/var/run/utmp -F perm=wa -k session -a always,exit -F arch=b64 -S all -F path=/var/log/wtmp -F perm=wa -k session -a always,exit -F arch=b64 -S all -F path=/var/log/btmp -F perm=wa -k session " >> /etc/audit/rules.d/50-session.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-3 2. STIG ID: UBTU-24-900600 | RULE ID: SV-270811r1066922 | CAT II 3. STIG ID: UBTU-22-654205 | RULE ID: SV-260643r991581 | CAT II 4. STIG ID: UBTU-24-900590 | RULE ID: SV-270810r1066919 | CAT II 5. STIG ID: UBTU-22-654200 | RULE ID: SV-260642r991581 | CAT II 6. STIG ID: UBTU-24-900610 | RULE ID: SV-270812r1066925 | CAT II 7. STIG ID: UBTU-22-654195 | RULE ID: SV-260641r991581 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure Page 859 Internal Only - General For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 860 Internal Only - General 6.2.3.23 Ensure login and logout events are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor login and logout events. The parameters below track changes to files associated with login/logout events. • /var/log/lastlog - maintain records of the last time a user successfully logged in. • /var/run/faillock - directory maintains records of login failures via the pam_faillock module. Rationale: Monitoring login/logout events could provide a system administrator with information associated with brute force attacks against user logins. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000473- GPOS-00218 Page 861 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '(lastlog|faillock)' Verify the output includes: -a always,exit -F path=/var/log/lastlog -F perm=wa -a always,exit -F path=/var/run/faillock -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '(lastlog|faillock)' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-login.rules:-a always,exit -F arch=b64 -S all -F path=/var/log/lastlog -F perm=wa -k logins /etc/audit/rules.d/50-login.rules:-a always,exit -F arch=bs4 -S all -F path=/var/run/faillock -F perm=wa -k logins Page 862 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor login and logout events. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/var/log/lastlog -F perm=wa -k logins -a always,exit -F arch=b64 -S all -F path=/var/run/faillock -F perm=wa -k logins " >> /etc/audit/rules.d/50-login.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030600 | RULE ID: SV-230467r627750 | CAT II 4. STIG ID: RHEL-09-654255 | RULE ID: SV-258225r1014990 | CAT II 5. STIG ID: ALMA-09-047540 | RULE ID: SV-269470r1050353 | CAT II 6. STIG ID: UBTU-24-900260 | RULE ID: SV-270797r1066880 | CAT II 7. STIG ID: UBTU-22-654215 | RULE ID: SV-260645r958446 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 863 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 864 Internal Only - General 6.2.3.24 Ensure unlink file deletion events by users are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the use of system calls associated with the deletion or renaming of files and file attributes. This configuration statement sets up monitoring for: • unlink - remove a file • unlinkat - remove a file attribute system calls and tags them with the identifier "delete". Rationale: Monitoring these calls from non-privileged users could provide a system administrator with evidence that inappropriate removal of files and file attributes associated with protected files is occurring. While this audit option will look at all events, system administrators will want to look for specific privileged files that are being deleted or altered. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215 Page 865 Internal Only - General Audit: Note: • Output showing all audited syscalls, e.g. (-a always,exit -S unlink,unlinkat,rename,renameat,renameat2 -F auid>=1000 -F auid!=unset) is also acceptable. These have been separated by function on the displayed output for clarity. • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'unlink' Verify the output includes: -a always,exit -S unlink,unlinkat -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'unlink' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-delete.rules:-a always,exit -F arch=b64 -S unlink,unlinkat -F auid>=1000 -F auid!=-1 -k delete Page 866 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor file deletion events by users. Example: # printf " -a always,exit -F arch=b64 -S unlink,unlinkat -F auid>=1000 -F auid!=unset -k delete " >> /etc/audit/rules.d/50-delete.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030361 | RULE ID: SV-230439r810465 | CAT II 4. STIG ID: RHEL-09-654065 | RULE ID: SV-258187r1045346 | CAT II 5. STIG ID: ALMA-09-048970 | RULE ID: SV-269483r1050366 | CAT II 6. STIG ID: UBTU-22-654185 | RULE ID: SV-260639r991577 | CAT II 7. STIG ID: UBTU-24-900540 | RULE ID: SV-270809r1068388 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 867 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 868 Internal Only - General 6.2.3.25 Ensure rename file deletion events by users are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the use of system calls associated with the deletion or renaming of files and file attributes. This configuration statement sets up monitoring for: • rename: rename a file • renameat: rename a file attribute • renameat2: rename a file relative to directory file descriptors system calls and tags them with the identifier "delete". Rationale: Monitoring these calls from non-privileged users could provide a system administrator with evidence that inappropriate removal of files and file attributes associated with protected files is occurring. While this audit option will look at all events, system administrators will want to look for specific privileged files that are being deleted or altered. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215 Page 869 Internal Only - General Audit: Note: • Output showing all audited syscalls, e.g. (-a always,exit -S unlink,unlinkat,rename,renameat,renameat2 -F auid>=1000 -F auid!=unset) is also acceptable. These have been separated by function on the displayed output for clarity. • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'rename' Verify the output includes: -a always,exit -S rename,renameat,renameat2 -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'rename' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-delete.rules:-a always,exit -F arch=b64 -S rename,renameat,renameat2 -F auid>=1000 -F auid!=-1 -k delete Page 870 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor file deletion events by users. Example: # printf " -a always,exit -F arch=b64 -S rename,renameat,renameat2 -F auid>=1000 -F auid!=unset -k delete " >> /etc/audit/rules.d/50-delete.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030361 | RULE ID: SV-230439r810465 | CAT II 4. STIG ID: RHEL-09-654065 | RULE ID: SV-258187r1045346 | CAT II 5. STIG ID: ALMA-09-048970 | RULE ID: SV-269483r1050366 | CAT II 6. STIG ID: UBTU-22-654185 | RULE ID: SV-260639r991577 | CAT II 7. STIG ID: UBTU-24-900540 | RULE ID: SV-270809r1068388 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 871 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 872 Internal Only - General 6.2.3.26 Ensure events that modify the system's Mandatory Access Controls are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor AppArmor, an implementation of mandatory access controls. The parameters below monitor any write access (potential additional, deletion or modification of files in the directory) or attribute changes to the /etc/apparmor/ and /etc/apparmor.d/ directories. Note: If a different Mandatory Access Control method is used, changes to the corresponding directories should be audited. Rationale: Changes to files in the /etc/apparmor/ and /etc/apparmor.d/ directories could indicate that an unauthorized user is attempting to modify access controls and change security contexts, leading to a compromise of the system. Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'apparmor' Verify the output includes: -a always,exit -F path=/etc/apparmor -F perm=wa -a always,exit -F dir=/etc/apparmor.d -F perm=wa 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'apparmor' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-MAC-policy.rules:-a always,exit -F arch=b64 -S all -F path=/etc/apparmor -F perm=wa -k MAC-policy /etc/audit/rules.d/50-MAC-policy.rules:-a always,exit -F arch=b64 -S all -F dir=/etc/apparmor.d -F perm=wa -k MAC-policy Page 873 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's Mandatory Access Controls. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/etc/apparmor -F perm=wa -k MAC- policy -a always,exit -F arch=b64 -S all -F dir=/etc/apparmor.d -F perm=wa -k MAC- policy " >> /etc/audit/rules.d/50-MAC-policy.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 874 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 875 Internal Only - General 6.2.3.27 Ensure successful and unsuccessful attempts to use the chcon command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the chcon command. Rationale: The chcon command is used to change file security context. Without generating audit records that are specific to the security and needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000468-GPOS-00212, SRG-OS-000471- GPOS-00215 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exits in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/chcon' Verify the output includes: -a always,exit -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/chcon' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_chng.rules:-a always,exit -S all -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=-1 -k perm_chng Page 876 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the chcon command. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030260 | RULE ID: SV-230419r627750 | CAT II 4. STIG ID: RHEL-09-654045 | RULE ID: SV-258183r1045334 | CAT II 5. STIG ID: ALMA-09-048420 | RULE ID: SV-269478r1050361 | CAT II 6. STIG ID: UBTU-22-654025 | RULE ID: SV-260607r958446 | CAT II 7. STIG ID: UBTU-24-900210 | RULE ID: SV-270792r1066865 | CAT II Page 877 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 878 Internal Only - General 6.2.3.28 Ensure successful and unsuccessful attempts to use the setfacl command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the setfacl command Rationale: This utility sets Access Control Lists (ACLs) of files and directories. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps '^\h*[^#\n\r]+\h*\/usr\/bin\/setfacl' Verify the output includes: -a always,exit -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps '^\h*[^#\n\r]+\h*\/usr\/bin\/setfacl' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_chng.rules:-a always,exit -F arch=b64 -S all -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng Page 879 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the setfacl command. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 2. STIG ID: RHEL-08-030330 | RULE ID: SV-230435r627750 | CAT II 3. STIG ID: RHEL-09-654040 | RULE ID: SV-258182r1045331 | CAT II 4. STIG ID: ALMA-09-050180 | RULE ID: SV-269494r1050377 | CAT II 5. STIG ID: UBTU-22-654085 | RULE ID: SV-260619r958446 | CAT II 6. STIG ID: UBTU-24-900230 | RULE ID: SV-270794r1066871 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 880 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 881 Internal Only - General 6.2.3.29 Ensure successful and unsuccessful attempts to use the chacl command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the chacl command. chacl is an IRIX-compatibility command, and is maintained for those users who are familiar with its use from either XFS or IRIX. Rationale: chacl changes the ACL(s) for a file or directory. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466- GPOS-00210 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/chacl' Verify the output includes: -a always,exit -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/chacl' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-perm_chng.rules:-a always,exit -S all -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=-1 -k perm_chng Page 882 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the chacl command. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030570 | RULE ID: SV-230464r627750 | CAT II 4. STIG ID: RHEL-09-654035 | RULE ID: SV-258181r1045328 | CAT II 5. STIG ID: ALMA-09-048200 | RULE ID: SV-269476r1050359 | CAT II 6. STIG ID: UBTU-22-654015 | RULE ID: SV-260605r958446 | CAT II 7. STIG ID: UBTU-24-900240 | RULE ID: SV-270795r1066874 | CAT II Page 883 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 884 Internal Only - General 6.2.3.30 Ensure successful and unsuccessful attempts to use the usermod command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the usermod command. Rationale: The usermod command modifies the system account files to reflect the changes that are specified on the command line. Without generating audit records that are specific to the security and needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466- GPOS-00210 Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/sbin\/usermod' Verify the output includes: -a always,exit -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/sbin\/usermod' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-usermod.rules:-a always,exit -F arch=b64 -S all -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=-1 -k usermod Page 885 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the usermod command. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=unset -k usermod " >> /etc/audit/rules.d/50-usermod.rules unset Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030560 | RULE ID: SV-230463r627750 | CAT II 4. STIG ID: RHEL-09-654175 | RULE ID: SV-258209r1045412 | CAT II 5. STIG ID: ALMA-09-051280 | RULE ID: SV-269504r1050387 | CAT II 6. STIG ID: UBTU-22-654125 | RULE ID: SV-260627r958446 | CAT II 7. STIG ID: UBTU-24-900310 | RULE ID: SV-270802r1066895 | CAT II Page 886 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 887 Internal Only - General 6.2.3.31 Ensure kernel module loading unloading and modification is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the loading and unloading of kernel modules. All the loading / listing / dependency checking of modules is done by kmod via symbolic links. Rationale: Monitoring the use of all the various ways to manipulate kernel modules could provide system administrators with evidence that an unauthorized change was made to a kernel module, possibly compromising the security of the system. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471- GPOS-00216, SRG-OS-000477-GPOS-00222 Page 888 Internal Only - General Audit: Note: The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/kmod' Verify the output includes: -a always,exit -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- '^\h*[^#\n\r]+\h*\/usr\/bin\/kmod' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-kernel_modules.rules:-a always,exit -F arch=b64 -S all -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset -k kernel_modules Symlink audit Run the following script to audit if the symlinks kmod accepts are indeed pointing at it: #!/usr/bin/env bash { a_files=("/usr/sbin/lsmod" "/usr/sbin/rmmod" "/usr/sbin/insmod" "/usr/sbin/modinfo" "/usr/sbin/modprobe" "/usr/sbin/depmod") for l_file in "${a_files[@]}"; do if [ "$(readlink -f "$l_file")" = "$(readlink -f /bin/kmod)" ]; then printf "OK: \"$l_file\"\n" else printf "Issue with symlink for file: \"$l_file\"\n" fi done } Verify the output states OK. If there is a symlink pointing to a different location it should be investigated Page 889 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor kernel module modification. Example: # printf " -a always,exit -F arch=b64 -S all -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset -k kernel_modules " >> /etc/audit/rules.d/50-kernel_modules.rules 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 890 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 891 Internal Only - General 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading unloading and modification is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The following system calls control loading and unloading of modules: • init_module - load a module • finit_module - load a module (used when the overhead of using cryptographically signed modules to determine the authenticity of a module can be avoided) Any execution of the loading and unloading module programs and system calls will trigger an audit record with an identifier of modules. Rationale: Monitoring the use of all the various ways to manipulate kernel modules could provide system administrators with evidence that an unauthorized change was made to a kernel module, possibly compromising the security of the system. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471- GPOS-00216, SRG-OS-000477-GPOS-00222 Page 892 Internal Only - General Audit: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • Output showing all the audited syscalls, e.g. (-a always,exit -F arch=b64 -S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset -k kernel_modules) is also acceptable. These have been separated by function on the displayed output for clarity. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'init_module' Verify the output includes init_module and finite_module: -a always,exit -S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'init_module' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-kernel_modules.rules:-a always,exit -F arch=b64 -S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset -k kernel_modules Page 893 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor kernel module modification. Example: # printf " -a always,exit -F arch=b64 -S init_module,finit_module -F auid>=1000 -F auid!=unset -k kernel_modules " >> /etc/audit/rules.d/50-kernel_modules.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030360 | RULE ID: SV-230438r1017241 | CAT II 4. STIG ID: RHEL-09-654080 | RULE ID: SV-258198r1045379 | CAT II 5. STIG ID: ALMA-09-046660 | RULE ID: SV-269466r1050349 | CAT II 6. STIG ID: UBTU-22-654175 | RULE ID: SV-260637r958446 | CAT II 7. STIG ID: UBTU-24-900340 | RULE ID: SV-270805r1068384 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 894 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 895 Internal Only - General 6.2.3.33 Ensure kernel "delete_module" loading unloading and modification is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the loading and unloading of kernel modules. All the loading / listing / dependency checking of modules is done by kmod via symbolic links. The following system calls control loading and unloading of modules: • delete_module - delete a module Any execution of the loading and unloading module programs and system calls will trigger an audit record with an identifier of modules. Rationale: Monitoring the use of all the various ways to manipulate kernel modules could provide system administrators with evidence that an unauthorized change was made to a kernel module, possibly compromising the security of the system. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471- GPOS-00216, SRG-OS-000477-GPOS-00222 Page 896 Internal Only - General Audit: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • Output showing all the audited syscalls, e.g. (-a always,exit -F arch=b64 - S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset -k kernel_modules) is also acceptable. These have been separated by function on the displayed output for clarity. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'delete_module' Verify the output includes delete_module: -a always,exit -S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'delete_module' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-kernel_modules.rules:-a always,exit -F arch=b64 -S delete_module -F auid>=1000 -F auid!=-1 -k kernel_modules Page 897 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor kernel module modification. Example: # printf " -a always,exit -F arch=b64 -S delete_module -F auid>=1000 -F auid!=unset -k kernel_modules " >> /etc/audit/rules.d/50-kernel_modules.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2.Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) 3. STIG ID: RHEL-08-030390 | RULE ID: SV-230446r627750 | CAT II 4. STIG ID: RHEL-09-654075 | RULE ID: SV-258189r1045352 | CAT II 5. STIG ID: ALMA-09-046660 | RULE ID: SV-269466r1050349 | CAT II 6. STIG ID: UBTU-22-654170 | RULE ID: SV-260636r958446 | CAT II 7. STIG ID: UBTU-24-900350 | RULE ID: SV-270806r1068386 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 898 Internal Only - General System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 899 Internal Only - General 6.2.3.34 Ensure kernel query_module loading unloading and modification is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the loading and unloading of kernel modules. All the loading / listing / dependency checking of modules is done by kmod via symbolic links. The following system calls control loading and unloading of modules: • create_module - create a loadable module entry • query_module - query the kernel for various bits pertaining to modules Any execution of the loading and unloading module programs and system calls will trigger an audit record with an identifier of modules. Rationale: Monitoring the use of all the various ways to manipulate kernel modules could provide system administrators with evidence that an unauthorized change was made to a kernel module, possibly compromising the security of the system. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS- 000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471- GPOS-00216, SRG-OS-000477-GPOS-00222 Page 900 Internal Only - General Audit: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • Output showing all the audited syscalls, e.g. (-a always,exit -F arch=b64 -S init_module,finit_module,delete_module,create_module,query_module -F auid>=1000 -F auid!=unset -k kernel_modules) is also acceptable. These have been separated by function on the displayed output for clarity. 1. Run the following command to verify a rule exists in the running configuration: # auditctl -l | grep -Ps -- 'query_module' Verify the output includes query_module: -a always,exit-S init_module,finit_module,delete_module,query_module -F auid>=1000 -F auid!=unset 2. Run the following command to verify a rule exists in a rules file: # grep -Ps -- 'query_module' /etc/audit/rules.d/*.rules Example output: /etc/audit/rules.d/50-kernel_modules.rules :-a always,exit -F arch=b64 -S init_module,delete_module,query_module,finit_module -F auid>=1000 -F auid!=-1 -k kernel_modules Page 901 Internal Only - General Remediation: Note: • The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure. • For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated. 1. Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor kernel module modification. Example: # printf " -a always,exit -F arch=b64 -S query_module -F auid>=1000 -F auid!=unset -k kernel_modules " >> /etc/audit/rules.d/50-kernel_modules.rules Note: The auid>= value should be set to the same value as UID_MIN value in /etc/login.defs. 2. Merge and load the rules into active configuration: # augenrules --load 3. Check if reboot is required: # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 :: AU-12 a 2. NIST SP 800-53A :: AU-12.1 (ii) Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 902 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 903 Internal Only - General 6.2.3.35 Ensure the audit configuration is loaded regardless of errors (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Set -c flag so that auditctl will continue loading rules in spite of an error. The exit code will not be success if any rule fails to load. Rationale: The default behaviour of auditctl is to stop loading any further rules if it encounters an error in the rules (for example a file watcher referencing a non-existent file). This can lead to auditd running without valid rules being present. It is best to have all valid rules loaded and active rather than a subset. Audit: Run the following command and verify output matches: # grep -Ph -- '^\h*-c\b' /etc/audit/rules.d/*.rules | tail -1 -c Remediation: Edit or create the file /etc/audit/rules.d/01-initialize.rules and add the line - c at the end of the file: Example: # printf '%s\n' "" "-c" >> /etc/audit/rules.d/01-initialize.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. Page 904 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 905 Internal Only - General 6.2.3.36 Ensure the audit configuration is immutable (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Set system audit so that audit rules cannot be modified with auditctl . Setting the flag "-e 2" forces audit to be put in immutable mode. Audit changes can only be made on system reboot. Note: This setting will require the system to be rebooted to update the active auditd configuration settings. Rationale: In immutable mode, unauthorized users cannot execute changes to the audit system to potentially hide malicious activity and then put the audit rules back. Users would most likely notice a system reboot and that could alert administrators of an attempt to make unauthorized audit changes. Audit: Run the following command and verify output matches: # grep -Ph -- '^\h*-e\h+2\b' /etc/audit/rules.d/*.rules | tail -1 -e 2 Remediation: Edit or create the file /etc/audit/rules.d/99-finalize.rules and add the line -e 2 at the end of the file: Example: # printf '\n%s' "-e 2" >> /etc/audit/rules.d/99-finalize.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Page 906 Internal Only - General References: 1. NIST SP 800-53 :: AU-9 2. NIST SP 800-53A :: AU-9.1 3. STIG ID: OL08-00-030121 | RULE ID: SV-248738r958434 | CAT II 4. STIG ID: RHEL-08-030121 | RULE ID: SV-230402r1017208 | CAT II 5. STIG ID: RHEL-09-654275 | RULE ID: SV-258241r1051259 | CAT II 6. STIG ID: ALMA-09-057110 | RULE ID: SV-269195r1050078 | CAT II 7. STIG ID: OL09-00-008005 | RULE ID: SV-271886r1092370 | CAT II 8. STIG ID: UBTU-24-909000 | RULE ID: SV-270832r1068399 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 907 Internal Only - General 6.2.3.37 Ensure the running and on disk configuration is the same (Manual) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The Audit system have both on disk and running configuration. It is possible for these configuration settings to differ. Note: Due to the limitations of augenrules and auditctl, it is not absolutely guaranteed that loading the rule sets via augenrules --load will result in all rules being loaded or even that the user will be informed if there was a problem loading the rules. Rationale: Configuration differences between what is currently running and what is on disk could cause unexpected problems or may give a false impression of compliance requirements. Audit: Merged rule sets Ensure that all rules in /etc/audit/rules.d have been merged into /etc/audit/audit.rules: # augenrules --check /usr/sbin/augenrules: No change Should there be any drift, run augenrules --load to merge and load all rules. Remediation: If the rules are not aligned across all three () areas, run the following command to merge and load all rules: # augenrules --load Check if reboot is required. if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then echo "Reboot required to load rules"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 908 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 909 Internal Only - General 6.2.4 Configure auditd File Access Without the capability to restrict which roles and individuals can select which events are audited, unauthorized personnel may be able to prevent the auditing of critical events. Page 910 Internal Only - General 6.2.4.1 Ensure audit log files mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Audit: Run the following script to verify audit log files are mode 0640 or more restrictive: #!/usr/bin/env bash { l_perm_mask="0137" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then l_maxperm="$(printf '%o' $(( 0777 & ~$l_perm_mask )) )" a_files=() while IFS= read -r -d $'\0' l_file; do [ -e "$l_file" ] && a_files+=("$l_file") done < <(find "$l_audit_log_directory" -maxdepth 1 -type f -perm /"$l_perm_mask" -print0) if (( "${#a_files[@]}" > 0 )); then for l_file in "${a_files[@]}"; do l_file_mode="$(stat -Lc '%#a' "$l_file")" echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"$l_file\" is mode: \"$l_file_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" done else echo -e "\n- Audit Result:\n ** PASS **\n - All files in \"$l_audit_log_directory\" are mode: \"$l_maxperm\" or more restrictive" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"/etc/audit/auditd.conf\" not found.\n - ** Verify auditd is installed **" fi } Page 911 Internal Only - General Remediation: Run the following command to remove more permissive mode than 0640 from audit log files: # [ -f /etc/audit/auditd.conf ] && find "$(dirname $(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs))" -type f -perm /0137 -exec chmod u-x,g-wx,o-rwx {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 912 Internal Only - General 6.2.4.2 Ensure audit log files owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Audit: Run the following script to verify audit log files are owned by the root user: #!/usr/bin/env bash { l_output="" l_output2="" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then while IFS= read -r -d $'\0' l_file; do l_output2="$l_output2\n - File: \"$l_file\" is owned by user: \"$(stat -Lc '%U' "$l_file")\"\n (should be owned by user: \"root\")\n" done < <(find "$l_audit_log_directory" -maxdepth 1 -type f ! -user root -print0) else l_output2="$l_output2\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else l_output2="$l_output2\n - File: \"/etc/audit/auditd.conf\" not found.\n - ** Verify auditd is installed **" fi if [ -z "$l_output2" ]; then l_output="$l_output\n - All files in \"$l_audit_log_directory\" are owned by user: \"root\"\n" echo -e "\n- Audit Result:\n ** PASS **\n - * Correctly configured * :$l_output" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :$l_output2\n" fi } Page 913 Internal Only - General Remediation: Run the following command to configure the audit log files to be owned by the root user: # [ -f /etc/audit/auditd.conf ] && find "$(dirname $(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs))" -type f ! -user root -exec chown root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 914 Internal Only - General 6.2.4.3 Ensure audit log files group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Audit: Run the following command to verify log_group parameter is set to either adm or root in /etc/audit/auditd.conf: # grep -Piws -- '^\h*log_group\h*=\h*\H+\b' /etc/audit/auditd.conf | grep - Pvi -- '(adm)' Nothing should be returned Using the path of the directory containing the audit logs, verify audit log files are owned by the "root" or "adm" group by running the following script: #!/usr/bin/env bash { if [ -e /etc/audit/auditd.conf ]; then l_fpath="$(dirname "$(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs)")" find -L "$l_fpath" -not -path "$l_fpath"/lost+found -type f \( ! -group root -a ! -group adm \) -exec ls -l {} + fi } Nothing should be returned Page 915 Internal Only - General Remediation: Run the following command to configure the audit log files to be group owned by adm: # find $(dirname $(awk -F"=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs)) -type f \( ! -group adm -a ! -group root \) -exec chgrp adm {} + Run the following command to set the log_group parameter in the audit configuration file to log_group = adm: # sed -ri 's/^\s*#?\s*log_group\s*=\s*\S+(\s*#.*)?.*$/log_group = adm\1/' /etc/audit/auditd.conf Run the following command to restart the audit daemon to reload the configuration file: # systemctl restart auditd References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 916 Internal Only - General 6.2.4.4 Ensure the audit log file directory mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The audit log directory contains audit log files. Rationale: Audit information includes all information including: audit records, audit settings and audit reports. This information is needed to successfully audit system activity. This information must be protected from unauthorized modification or deletion. If this information were to be compromised, forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. Audit: Run the following script to verify the audit log directory is mode 0750 or more restrictive: #!/usr/bin/env bash { l_perm_mask="0027" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then l_maxperm="$(printf '%o' $(( 0777 & ~$l_perm_mask )) )" l_directory_mode="$(stat -Lc '%#a' "$l_audit_log_directory")" if [ $(( $l_directory_mode & $l_perm_mask )) -gt 0 ]; then echo -e "\n- Audit Result:\n ** FAIL **\n - Directory: \"$l_audit_log_directory\" is mode: \"$l_directory_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" else echo -e "\n- Audit Result:\n ** PASS **\n - Directory: \"$l_audit_log_directory\" is mode: \"$l_directory_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"/etc/audit/auditd.conf\" not found\n - ** Verify auditd is installed **" fi } Page 917 Internal Only - General Remediation: Run the following command to configure the audit log directory to have a mode of "0750" or less permissive: # chmod g-w,o-rwx "$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" Default Value: 750 References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 918 Internal Only - General 6.2.4.5 Ensure audit configuration files mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following script to verify that the audit configuration files are mode 0640 or more restrictive: #!/usr/bin/env bash { l_output="" l_output2="" l_perm_mask="0137" l_maxperm="$( printf '%o' $(( 0777 & ~$l_perm_mask )) )" while IFS= read -r -d $'\0' l_fname; do l_mode=$(stat -Lc '%#a' "$l_fname") if [ $(( "$l_mode" & "$l_perm_mask" )) -gt 0 ]; then l_output2="$l_output2\n - file: \"$l_fname\" is mode: \"$l_mode\" (should be mode: \"$l_maxperm\" or more restrictive)" fi done < <(find /etc/audit/ -type f \( -name "*.conf" -o -name '*.rules' \) -print0) if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n - All audit configuration files are mode: \"$l_maxperm\" or more restrictive" else echo -e "\n- Audit Result:\n ** FAIL **\n$l_output2" fi } Page 919 Internal Only - General Remediation: Run the following command to remove more permissive mode than 0640 from the audit configuration files: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) -exec chmod u-x,g-wx,o-rwx {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 920 Internal Only - General 6.2.4.6 Ensure audit configuration files owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following command to verify that the audit configuration files are owned by the root user: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -user root Nothing should be returned Remediation: Run the following command to change ownership to root user: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -user root -exec chown root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 921 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 922 Internal Only - General 6.2.4.7 Ensure audit configuration files group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following command to verify that the audit configuration files are owned by the group root: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -group root Nothing should be returned Remediation: Run the following command to change group to root: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -group root -exec chgrp root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 923 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 924 Internal Only - General 6.2.4.8 Ensure audit tools mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following script to verify the audit tools are mode 0755 or more restrictive: #!/usr/bin/env bash { l_output="" l_output2="" l_perm_mask="0022" l_maxperm="$( printf '%o' $(( 0777 & ~$l_perm_mask )) )" a_audit_tools=("/sbin/auditctl" "/sbin/aureport" "/sbin/ausearch" "/sbin/auditd" "/sbin/augenrules") for l_audit_tool in "${a_audit_tools[@]}"; do l_mode="$(stat -Lc '%#a' "$l_audit_tool")" if [ $(( "$l_mode" & "$l_perm_mask" )) -gt 0 ]; then l_output2="$l_output2\n - Audit tool \"$l_audit_tool\" is mode: \"$l_mode\" and should be mode: \"$l_maxperm\" or more restrictive" else l_output="$l_output\n - Audit tool \"$l_audit_tool\" is correctly configured to mode: \"$l_mode\"" fi done if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n - * Correctly configured * :$l_output" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :$l_output2\n" [ -n "$l_output" ] && echo -e "\n - * Correctly configured * :\n$l_output\n" fi unset a_audit_tools } Page 925 Internal Only - General Remediation: Run the following command to remove more permissive mode from the audit tools: # chmod go-w /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 926 Internal Only - General 6.2.4.9 Ensure audit tools owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following command to verify the audit tools are owned by the root user: # stat -Lc "%n %U" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/auditd /sbin/augenrules | awk '$2 != "root" {print}' Nothing should be returned Remediation: Run the following command to change the owner of the audit tools to the root user: # chown root /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 927 Internal Only - General 6.2.4.10 Ensure audit tools group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following command to verify the audit tools are owned by the group root # stat -Lc "%n %G" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/auditd /sbin/augenrules | awk '$2 != "root" {print}' Nothing should be returned Remediation: Run the following command to change group ownership to the group root: # chgrp root /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 928 Internal Only - General 6.3 Configure Integrity Checking AIDE is a file integrity checking tool, similar in nature to Tripwire. While it cannot prevent intrusions, it can detect unauthorized changes to configuration files by alerting when the files are changed. When setting up AIDE, decide internally what the site policy will be concerning integrity checking. Review the AIDE quick start guide and AIDE documentation before proceeding. Page 929 Internal Only - General 6.3.1 Ensure AIDE is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AIDE takes a snapshot of filesystem state including modification times, permissions, and file hashes which can then be used to compare against the current state of the filesystem to detect modifications to the system. Rationale: By monitoring the filesystem state compromised files can be detected to prevent or limit the exposure of accidental or malicious misconfigurations or modified binaries. Audit: Run the following command to verify aide is installed: # dpkg-query -s aide &>/dev/null && echo "aide is installed" aide is installed Run the following command to verify aide-common is installed: # dpkg-query -s aide-common &>/dev/null && echo "aide-common is installed" aide-common is installed Remediation: Install AIDE using the appropriate package manager or manual installation: # apt install aide aide-common Configure AIDE as appropriate for your environment. Consult the AIDE documentation for options. Run the following commands to initialize AIDE: # aideinit # mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db References: 1. NIST SP 800-53 Rev. 5: AU-2 Additional Information: The prelinking feature can interfere with AIDE because it alters binaries to speed up their start up times. Run prelink -ua to restore the binaries to their prelinked state, thus avoiding false positives from AIDE. Page 930 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 931 Internal Only - General 6.3.2 Ensure filesystem integrity is regularly checked (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Periodic checking of the filesystem integrity is needed to detect changes to the filesystem. Rationale: Periodic file checking allows the system administrator to determine on a regular basis if critical files have been changed in an unauthorized fashion. Audit: Run the following command: # systemctl list-unit-files | awk '$1~/^dailyaidecheck\.(timer|service)$/{print $1 "\t" $2}' Example output: dailyaidecheck.service static dailyaidecheck.timer enabled Verify dailyaidecheck.timer is enabled and dailyaidecheck.service is either static or enabled. Run the following command to verify dailyaidecheck.timer is active: # systemctl is-active dailyaidecheck.timer active Remediation: Run the following command to unmask dailyaidecheck.timer and dailyaidecheck.service: # systemctl unmask dailyaidecheck.timer dailyaidecheck.service Run the following command to enable and start dailyaidecheck.timer: # systemctl --now enable dailyaidecheck.timer References: 1. https://github.com/konstruktoid/hardening/blob/master/config/aidecheck.service 2. https://github.com/konstruktoid/hardening/blob/master/config/aidecheck.timer 3. NIST SP 800-53 Rev. 5: AU-2 Page 932 Internal Only - General Additional Information: The checking in this recommendation occurs every day at 5am. Alter the frequency and time of the checks in compliance with site policy systemd timers, timer file aidecheck.timer and service file aidecheck.service, have been included as an optional alternative to using cron Ubuntu advises using /usr/bin/aide.wrapper rather than calling /usr/bin/aide directly in order to protect the database and prevent conflicts CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 933 Internal Only - General 6.3.3 Ensure cryptographic mechanisms are used to protect the integrity of audit tools (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. aide.conf is case-sensitive. Leading and trailing white spaces are ignored. Each config lines must end with new line. AIDE uses the backslash character \ as escape character for ' ' (space), '@' and '' (backslash) (e.g. '\ ' or '@'). To literally match a '' in a file path with a regular expression you have to escape the backslash twice (i.e. '\\'). There are three types of lines in aide.conf: • The configuration options which are used to set configuration parameters and define groups. • (restricted) rules that are used to indicate which files are added to the database. • Macro lines define or undefine variables within the config file. Note: Lines beginning with # are ignored as comments. @@include - Include . • The content of the file is used as if it were inserted in this part of the config file. • The maximum depth of nested includes is 16. `@@include - [RULE_PREFIX] (added in AIDE v0.17) • Include all (regular) files found in matching regular expression (sub-directories are ignored). • The file are included in lexical sort order. • If RULE_PREFIX is set, all rules included by the statement are prefixed with given (added in AIDE v0.18). Prefixes from nested include statements are concatenated. • The content of the files is used as if it were inserted in this part of the config file. @x_include: • is identical to @@include, except that if a config file is executable is is run and the output is used as config. Page 934 Internal Only - General • If the executable file exits with status greater than zero or writes to stderr aide stops with an error. • For security reasons and each executable config file must be owned by the current user or root. They must not be group- or world-writable. • @@x_include __ (added in AIDE v0.17): • `@@x_include [RULE_PREFIX] (added in AIDE v0.17) @@x_include_setenv (added in AIDE v0.17) • Adds the variable with the value to the environment used for config file execution. • Environment variable names are limited to alphanumeric characters (A-Za-z0-9) and the underscore '_' and must not begin with a digit. Rationale: Protecting the integrity of the tools used for auditing purposes is a critical step toward ensuring the integrity of audit information. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. Attackers may replace the audit tools or inject code into the existing tools with the purpose of providing the capability to hide or erase system activity from the audit logs. Audit tools should be cryptographically signed in order to provide the capability to identify when the audit tools have been modified, manipulated, or replaced. An example is a checksum hash of the file or files. Audit: Verify that Advanced Intrusion Detection Environment (AIDE) is properly configured . Run the following script to verify: • AIDE is configured to use cryptographic mechanisms to protect the integrity of audit tools: • The following audit tool files include the options "p, i, n, u, g, s, b, acl, xattrs and sha512" o auditctl o auditd o ausearch o aureport o augenrules Page 935 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() l_tool_dir="$(readlink -f /sbin)" a_items=("p" "i" "n" "u" "g" "s" "b" "acl" "xattrs" "sha512") l_aide_cmd="$(whereis aide | awk '{print $2}')" a_audit_files=("auditctl" "auditd" "ausearch" "aureport" "augenrules") if [ -f "$l_aide_cmd" ] && command -v "$l_aide_cmd" &>/dev/null; then a_aide_conf_files=("$(find -L /etc -type f -name 'aide.conf')") f_file_par_chk() { a_out2=() for l_item in "${a_items[@]}"; do ! grep -Psiq -- '(\h+|\+)'"$l_item"'(\h+|\+)' <<< "$l_out" && \ a_out2+=(" - Missing the \"$l_item\" option") done if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=(" - Audit tool file: \"$l_file\"" "${a_out2[@]}") else a_output+=(" - Audit tool file: \"$l_file\" includes:" " \"${a_items[*]}\"") fi } for l_file in "${a_audit_files[@]}"; do if [ -f "$l_tool_dir/$l_file" ]; then l_out="$("$l_aide_cmd" --config "${a_aide_conf_files[@]}" -p f:"$l_tool_dir/$l_file")" f_file_par_chk else a_output+=(" - Audit tool file \"$l_file\" doesn't exist") fi done else a_output2+=(" - The command \"aide\" was not found" " Please install AIDE") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } Note: The script is written to read the "winning" configuration setting, to include any configuration settings in files included as part of the @@x_include setting. Page 936 Internal Only - General Remediation: Run the following command to determine the absolute path to the non-symlinked version on the audit tools: # readlink -f /sbin The output will be either /usr/sbin - OR - /sbin. Ensure the correct path is used. Edit /etc/aide/aide.conf and add or update the following selection lines replacing with the correct path returned in the command above: # Audit Tools /auditctl p+i+n+u+g+s+b+acl+xattrs+sha512 /auditd p+i+n+u+g+s+b+acl+xattrs+sha512 /ausearch p+i+n+u+g+s+b+acl+xattrs+sha512 /aureport p+i+n+u+g+s+b+acl+xattrs+sha512 /augenrules p+i+n+u+g+s+b+acl+xattrs+sha512 Example # printf '%s\n' "" "# Audit Tools" "$(readlink -f /sbin/auditctl) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/auditd) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/ausearch) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/aureport) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -f /sbin/augenrules) p+i+n+u+g+s+b+acl+xattrs+sha512" >> /etc/aide/aide.conf Note: - IF - /etc/aide/aide.conf includes a @@x_include statement: • and each executable config file must be owned by the current user or root • They must not be group or world-writable Example: @@x_include /etc/aide.conf.d ^[a-zA-Z0-9_-]+$ References: 1. AIDE.CONF(5) CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 937 Internal Only - General 7 System Maintenance Recommendations in this section are intended as maintenance and are intended to be checked on a frequent basis to ensure system stability. Many recommendations do not have quick remediations and require investigation into the cause and best fix available and may indicate an attempted breach of system security. Page 938 Internal Only - General 7.1 Configure system file and directory access This section provides guidance on securing aspects of system files and directories. Page 939 Internal Only - General 7.1.1 Ensure access to /etc/passwd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/passwd file contains user account information that is used by many system utilities and therefore must be readable for these utilities to operate. Rationale: It is critical to ensure that the /etc/passwd file is protected from unauthorized write access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/passwd is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/passwd Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/passwd: # chmod u-x,go-wx /etc/passwd # chown root:root /etc/passwd Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 940 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 941 Internal Only - General 7.1.2 Ensure access to /etc/passwd- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/passwd- file contains backup user account information. Rationale: It is critical to ensure that the /etc/passwd- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/passwd- is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/passwd- Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/passwd-: # chmod u-x,go-wx /etc/passwd- # chown root:root /etc/passwd- Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 942 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 943 Internal Only - General 7.1.3 Ensure access to /etc/group is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/group file contains a list of all the valid groups defined in the system. The command below allows read/write access for root and read access for everyone else. Rationale: The /etc/group file needs to be protected from unauthorized changes by non- privileged users, but needs to be readable as this information is used with many non- privileged programs. Audit: Run the following command to verify /etc/group is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/group Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/group: # chmod u-x,go-wx /etc/group # chown root:root /etc/group Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 944 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 945 Internal Only - General 7.1.4 Ensure access to /etc/group- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/group- file contains a backup list of all the valid groups defined in the system. Rationale: It is critical to ensure that the /etc/group- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/group- is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/group- Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/group-: # chmod u-x,go-wx /etc/group- # chown root:root /etc/group- Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 946 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 947 Internal Only - General 7.1.5 Ensure access to /etc/shadow is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/shadow file is used to store the information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert the user accounts. Audit: Run the following command to verify /etc/shadow is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or ({GID}/ shadow): # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/shadow to root and group to either root or shadow: # chown root:shadow /etc/shadow -OR- # chown root:root /etc/shadow Run the following command to remove excess permissions form /etc/shadow: # chmod u-x,g-wx,o-rwx /etc/shadow Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 948 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 949 Internal Only - General 7.1.6 Ensure access to /etc/shadow- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/shadow- file is used to store backup information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: It is critical to ensure that the /etc/shadow- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/shadow- is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow- Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/shadow- to root and group to either root or shadow: # chown root:shadow /etc/shadow- -OR- # chown root:root /etc/shadow- Run the following command to remove excess permissions form /etc/shadow-: # chmod u-x,g-wx,o-rwx /etc/shadow- Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 950 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 951 Internal Only - General 7.1.7 Ensure access to /etc/gshadow is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/gshadow file is used to store the information about groups that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: If attackers can gain read access to the /etc/gshadow file, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/gshadow file (such as group administrators) could also be useful to subvert the group. Audit: Run the following command to verify /etc/gshadow is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or `{GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/gshadow Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/gshadow to root and group to either root or shadow: # chown root:shadow /etc/gshadow -OR- # chown root:root /etc/gshadow Run the following command to remove excess permissions form /etc/gshadow: # chmod u-x,g-wx,o-rwx /etc/gshadow Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 952 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 953 Internal Only - General 7.1.8 Ensure access to /etc/gshadow- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/gshadow- file is used to store backup information about groups that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: It is critical to ensure that the /etc/gshadow- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/gshadow- is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/gshadow- Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/gshadow- to root and group to either root or shadow: # chown root:shadow /etc/gshadow- -OR- # chown root:root /etc/gshadow- Run the following command to remove excess permissions form /etc/gshadow-: # chmod u-x,g-wx,o-rwx /etc/gshadow- Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 954 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 955 Internal Only - General 7.1.9 Ensure access to /etc/shells is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: /etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh and available to be queried by other programs. Rationale: It is critical to ensure that the /etc/shells file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/shells is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shells Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/shells: # chmod u-x,go-wx /etc/shells # chown root:root /etc/shells Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 956 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 957 Internal Only - General 7.1.10 Ensure access to /etc/security/opasswd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: /etc/security/opasswd and it's backup /etc/security/opasswd.old hold user's previous passwords if pam_unix or pam_pwhistory is in use on the system Rationale: It is critical to ensure that /etc/security/opasswd is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following commands to verify /etc/security/opasswd and /etc/security/opasswd.old are mode 600 or more restrictive, Uid is 0/root and Gid is 0/root if they exist: # [ -e "/etc/security/opasswd" ] && stat -Lc '%n Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/security/opasswd /etc/security/opasswd Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) -OR- Nothing is returned # [ -e "/etc/security/opasswd.old" ] && stat -Lc '%n Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/security/opasswd.old /etc/security/opasswd.old Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) -OR- Nothing is returned Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/security/opasswd and /etc/security/opasswd.old is they exist: # [ -e "/etc/security/opasswd" ] && chmod u-x,go-rwx /etc/security/opasswd # [ -e "/etc/security/opasswd" ] && chown root:root /etc/security/opasswd # [ -e "/etc/security/opasswd.old" ] && chmod u-x,go-rwx /etc/security/opasswd.old # [ -e "/etc/security/opasswd.old" ] && chown root:root /etc/security/opasswd.old Page 958 Internal Only - General Default Value: /etc/security/opasswd Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 959 Internal Only - General 7.1.11 Ensure world writable files and directories are secured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: World writable files are the least secure. Data in world-writable files can be modified and compromised by any user on the system. World writable files may also indicate an incorrectly written script or program that could potentially be the cause of a larger compromise to the system's integrity. See the chmod(2) man page for more information. Setting the sticky bit on world writable directories prevents users from deleting or renaming files in that directory that are not owned by them. Rationale: Data in world-writable files can be modified and compromised by any user on the system. World writable files may also indicate an incorrectly written script or program that could potentially be the cause of a larger compromise to the system's integrity. This feature prevents the ability to delete or rename files in world writable directories (such as /tmp ) that are owned by another user. Audit: Run the following script to verify: • No world writable files exist • No world writable directories without the sticky bit exist Page 960 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_file=() a_dir=() l_smask='01000' l_exclude="nfs|proc|cifs|smb|vfat|iso9660|efivarfs|selinuxfs|ncpfs" l_exclude2="\/run|\/tmp|\/var\/tmp" a_path=(-path "*/containers/storage/*" -o -path "*/containerd/*" -o -path "*/kubelet/*" -o -path "/sys/*" -o -path "/snap/*" -o -path "/boot/efi/*") while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then [ -f "$l_file" ] && a_file+=("$l_file") if [ -d "$l_file" ]; then l_mode="$(stat -Lc '%#a' "$l_file")" [ ! $(( $l_mode & $l_smask )) -gt 0 ] && a_dir+=("$l_file") fi fi done < <(find "$l_mount" -mount -xdev \( "${a_path[@]}" \) \ -prune -o \( -type f -o -type d \) -perm -0002 -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | \ awk '($1 !~ /^\s*('"$l_exclude"')/ && $2 !~ /^('"$l_exclude2"')(\/|$)/){print $2}') if [ "${#a_file[@]}" -le 0 ]; then printf '%s\n' "" " - No world writable files exist on the local filesystem." else printf '%s\n' "" " - There are \"${#a_file[@]}\" World writable files on the system." \ " - The following is a list of World writable files:" \ "${a_file[@]}" " - end of list" fi if [ "${#a_dir[@]}" -le 0 ]; then printf '%s\n' "" \ " - Sticky bit is set on world writable directories on the local filesystem." else printf '%s\n' "" " - There are \"${#a_dir[@]}\" World writable directories" \ " without the sticky bit on the system." \ " - The following is a list of World writable directories without the sticky bit:" \ "${a_dir[@]}" " - end of list" fi } Note: On systems with a large number of files and/or directories, this audit may be a long running process Page 961 Internal Only - General Remediation: • World Writable Files: o It is recommended that write access is removed from other with the command ( chmod o-w ), but always consult relevant vendor documentation to avoid breaking any application dependencies on a given file. • World Writable Directories: o Set the sticky bit on all world writable directories with the command ( chmod a+t ) Run the following script to: • Remove other write permission from any world writable files • Add the sticky bit to all world writable directories #!/usr/bin/env bash { l_smask='01000' a_file=() a_dir=() a_path=(-path "*/containers/storage/*" -o -path "*/containerd/*" -o -path "*/kubelet/*" -o -path "/sys/*" -o -path "/snap/*" -o -path "/boot/efi/*") l_exclude="nfs|proc|cifs|smb|vfat|iso9660|efivarfs|selinuxfs|ncpfs" l_exclude2="\/run|\/tmp|\/var\/tmp" while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do l_mode="$(stat -Lc '%#a' "$l_file" 2>/dev/null)" if [ -f "$l_file" ]; then # Remove excess permissions from WW files printf '%s\n' "" " - File: \"$l_file\" is mode: \"$l_mode\"" \ " - removing write permission on \"$l_file\" from \"other\"" chmod o-w "$l_file" fi if [ -d "$l_file" ]; then # Add sticky bit if [ ! $(( $l_mode & $l_smask )) -gt 0 ]; then printf '%s\n' "" " - Directory: \"$l_file\" is mode: \"$l_mode\"" \ " and doesn't have the sticky bit set" \ " - Adding the sticky bit" chmod a+t "$l_file" fi fi done < <(find "$l_mount" -mount -xdev \( "${a_path[@]}" \) \ -prune -o \( -type f -o -type d \) -perm -0002 -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | \ awk '($1 !~ /^\s*('"$l_exclude"')/ && $2 !~ /^('"$l_exclude2"')(\/|$)/){print $2}') } References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 2. STIG ID: UBTU-20-010411 | Rule ID: SV-238332r958524 | CAT || Page 962 Internal Only - General 3. STIG ID: UBTU-22-232145 | Rule ID: SV-260513r958524 | CAT || CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 963 Internal Only - General 7.1.12 Ensure no files or directories without an owner and a group exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Administrators may delete users or groups from the system and neglect to remove all files and/or directories owned by those users or groups. Rationale: A new user or group who is assigned a deleted user's user ID or group ID may then end up "owning" a deleted user or group's files, and thus have more access on the system than was intended. Audit: Run the following script to verify no unowned or ungrouped files or directories exist: Page 964 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_nouser=() a_nogroup=() # Initialize arrays a_path=(-path "*/containers/storage/*" -o -path "*/containerd/*" -o -path "*/kubelet/*" -o -path "/sys/*" -o -path "/snap/*" -o -path "/boot/efi/*") while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then while IFS=: read -r l_user l_group; do [ "$l_user" = "UNKNOWN" ] && a_nouser+=("$l_file") [ "$l_group" = "UNKNOWN" ] && a_nogroup+=("$l_file") done < <(stat -Lc '%U:%G' "$l_file") fi done < <(find "$l_mount" -mount -xdev \( "${a_path[@]}" \) -prune -o \( -type f -o -type d \) \( -nouser -o -nogroup \) -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | awk '($1 !~ /^\s*(nfs|proc|cifs|smb|vfat|iso9660|efivarfs|selinuxfs|ncpfs)/ && $2 !~ /^(\/run|\/tmp|\/var\/tmp)(\/|$)/){print $2}') if [ "${#a_nouser[@]}" -le 0 ]; then a_output+=(" - No files or directories without an owner exist on the local filesystem.") else a_output2+=(" - There are \"${#a_nouser[@]}\" unowned files or directories on the system." \ " - The following is a list of unowned files and/or directories:" \ "${a_nouser[@]}" " - end of list") fi if [ "${#a_nogroup[@]}" -le 0 ]; then a_output+=(" - No files or directories without a group owner exist on the local filesystem.") else a_output2+=(" - There are \"${#a_nogroup[@]}\" ungrouped files or directories on the system." \ " - The following is a list of ungrouped files and/or directories:" \ "${a_nogroup[@]}" " - end of list") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Note: On systems with a large number of files and/or directories, this audit may be a long running process Page 965 Internal Only - General Remediation: Remove or set ownership and group ownership of these files and/or directories to an active user on the system as appropriate. References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 966 Internal Only - General 7.1.13 Ensure SUID and SGID files are reviewed (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The owner of a file can set the file's permissions to run with the owner's or group's permissions, even if the user running the program is not the owner or a member of the group. The most common reason for a SUID or SGID program is to enable users to perform functions (such as changing their password) that require root privileges. Rationale: There are valid reasons for SUID and SGID programs, but it is important to identify and review such programs to ensure they are legitimate. Review the files returned by the action in the audit section and check to see if system binaries have a different checksum than what from the package. This is an indication that the binary may have been replaced. Audit: Run the following script to generate a list of SUID and SGID files: Page 967 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" a_suid=(); a_sgid=() # initialize arrays while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then l_mode="$(stat -Lc '%#a' "$l_file")" [ $(( $l_mode & 04000 )) -gt 0 ] && a_suid+=("$l_file") [ $(( $l_mode & 02000 )) -gt 0 ] && a_sgid+=("$l_file") fi done < <(find "$l_mount" -xdev -type f \( -perm -2000 -o -perm -4000 \) -print0 2>/dev/null) done < <(findmnt -Dkerno fstype,target,options | awk '($1 !~ /^\s*(nfs|proc|smb|vfat|iso9660|efivarfs|selinuxfs)/ && $2 !~ /^\/run\/user\// && $3 !~/noexec/ && $3 !~/nosuid/) {print $2}') if ! (( ${#a_suid[@]} > 0 )); then l_output="$l_output\n - No executable SUID files exist on the system" else l_output2="$l_output2\n - List of \"$(printf '%s' "${#a_suid[@]}")\" SUID executable files:\n$(printf '%s\n' "${a_suid[@]}")\n - end of list -\n" fi if ! (( ${#a_sgid[@]} > 0 )); then l_output="$l_output\n - No SGID files exist on the system" else l_output2="$l_output2\n - List of \"$(printf '%s' "${#a_sgid[@]}")\" SGID executable files:\n$(printf '%s\n' "${a_sgid[@]}")\n - end of list -\n" fi [ -n "$l_output2" ] && l_output2="$l_output2\n- Review the preceding list(s) of SUID and/or SGID files to\n- ensure that no rogue programs have been introduced onto the system.\n" unset a_arr; unset a_suid; unset a_sgid # Remove arrays # If l_output2 is empty, Nothing to report if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n$l_output\n" else echo -e "\n- Audit Result:\n$l_output2\n" [ -n "$l_output" ] && echo -e "$l_output\n" fi } Note: on systems with a large number of files, this may be a long running process Page 968 Internal Only - General Remediation: Ensure that no rogue SUID or SGID programs have been introduced into the system. Review the files returned by the action in the Audit section and confirm the integrity of these binaries. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5, AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 969 Internal Only - General 7.2 Local User and Group Settings This section provides guidance on securing aspects of the local users and groups. Note: The recommendations in this section check local users and groups. Any users or groups from other sources such as LDAP will not be audited. In a domain environment similar checks should be performed against domain users and groups. Page 970 Internal Only - General 7.2.1 Ensure accounts in /etc/passwd use shadowed passwords (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Local accounts can uses shadowed passwords. With shadowed passwords, The passwords are saved in shadow password file, /etc/shadow, encrypted by a salted one-way hash. Accounts with a shadowed password have an x in the second field in /etc/passwd. Rationale: The /etc/passwd file also contains information like user ID's and group ID's that are used by many system programs. Therefore, the /etc/passwd file must remain world readable. In spite of encoding the password with a randomly-generated one-way hash function, an attacker could still break the system if they got access to the /etc/passwd file. This can be mitigated by using shadowed passwords, thus moving the passwords in the /etc/passwd file to /etc/shadow. The /etc/shadow file is set so only root will be able to read and write. This helps mitigate the risk of an attacker gaining access to the encoded passwords with which to perform a dictionary attack. Note: • All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user. • A user account with an empty second field in /etc/passwd allows the account to be logged into by providing only the username. Audit: Run the following command and verify that no output is returned: # awk -F: '($2 != "x" ) { print "User: \"" $1 "\" is not set to shadowed passwords "}' /etc/passwd Remediation: Run the following command to set accounts to use shadowed passwords and migrate passwords in /etc/passwd to /etc/shadow: # pwconv Investigate to determine if the account is logged in and what it is being used for, to determine if it needs to be forced off. Page 971 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: IA-5 2. PWCONV(8) Additional Information: The pwconv command creates shadow from passwd and an optionally existing shadow. • The pwunconv command creates passwd from passwd and shadow and then removes shadow. • The grpconv command creates gshadow from group and an optionally existing gshadow. • The grpunconv command creates group from group and gshadow and then removes gshadow. These four programs all operate on the normal and shadow password and group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow. Each program acquires the necessary locks before conversion. pwconv and grpconv are similar. First, entries in the shadowed file which don't exist in the main file are removed. Then, shadowed entries which don't have x' as the password in the main file are updated. Any missing shadowed entries are added. Finally, passwords in the main file are replaced with x'. These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand. pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and PASS_WARN_AGE from /etc/login.defs when adding new entries to /etc/shadow. pwunconv and grpunconv are similar. Passwords in the main file are updated from the shadowed file. Entries which exist in the main file but not in the shadowed file are left alone. Finally, the shadowed file is removed. Some password aging information is lost by pwunconv. It will convert what it can. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 972 Internal Only - General 7.2.2 Ensure /etc/shadow password fields are not empty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An account with an empty password field means that anybody may log in as that user without providing a password. Rationale: All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user. Audit: Run the following command and verify that no output is returned: # awk -F: '($2 == "" ) { print $1 " does not have a password "}' /etc/shadow Remediation: If any accounts in the /etc/shadow file do not have a password, run the following command to lock the account until it can be determined why it does not have a password: # passwd -l Also, check to see if the account is logged in and investigate what it is being used for to determine if it needs to be forced off. References: 1. NIST SP 800-53 Rev. 5: IA-5 2. NIST SP 800-53 Revision 5 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) Page 973 Internal Only - General Additional Information: Red Hat Enterprise Linux 8 Security Technical Implementation Guide Version 1, Release: 14 Benchmark Date: 24 APR 2024 Vul ID: V-251706 Rule ID: SV-251706r809342 STIG ID: RHEL-08-010121 Severity: CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 974 Internal Only - General 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Over time, system administration errors and changes can lead to groups being defined in /etc/passwd but not in /etc/group . Rationale: Groups defined in the /etc/passwd file but not in the /etc/group file pose a threat to system security since group permissions are not properly managed. Audit: Run the following script to verify all GIDs in /etc/passwd exist in /etc/group: #!/usr/bin/env bash { a_passwd_group_gid=("$(awk -F: '{print $4}' /etc/passwd | sort -u)") a_group_gid=("$(awk -F: '{print $3}' /etc/group | sort -u)") a_passwd_group_diff=("$(printf '%s\n' "${a_group_gid[@]}" "${a_passwd_group_gid[@]}" | sort | uniq -u)") while IFS= read -r l_gid; do awk -F: '($4 == '"$l_gid"') {print " - User: \"" $1 "\" has GID: \"" $4 "\" which does not exist in /etc/group" }' /etc/passwd done < <(printf '%s\n' "${a_passwd_group_gid[@]}" "${a_passwd_group_diff[@]}" | sort | uniq -D | uniq) unset a_passwd_group_gid; unset a_group_gid; unset a_passwd_group_diff } Nothing should be returned Remediation: Analyze the output of the Audit step above and perform the appropriate action to correct any discrepancies found. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 975 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote ● ● ● file systems, databases, and applications. 14.6 Train Workforce Members on Recognizing and v8 Reporting Security Incidents ● ● ● Train workforce members to be able to recognize a potential incident and be able to report such an incident. Page 976 Internal Only - General 7.2.4 Ensure shadow group is empty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The shadow group allows system programs which require access the ability to read the /etc/shadow file. No users should be assigned to the shadow group. Rationale: Any users assigned to the shadow group would be granted read access to the /etc/shadow file. If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed passwords to break them. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert additional user accounts. Audit: Run the following commands and verify no results are returned: # awk -F: '($1=="shadow") {print $NF}' /etc/group # awk -F: '($4 == '"$(getent group shadow | awk -F: '{print $3}' | xargs)"') {print " - user: \"" $1 "\" primary group is the shadow group"}' /etc/passwd Remediation: Run the following command to remove all users from the shadow group # sed -ri 's/(^shadow:[^:]*:[^:]*:)([^:]+$)/\1/' /etc/group Change the primary group of any users with shadow as their primary group. # usermod -g References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 977 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 978 Internal Only - General 7.2.5 Ensure no duplicate UIDs exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the useradd program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually edit the /etc/passwd file and change the UID field. Rationale: Users must be assigned unique UIDs for accountability and to ensure appropriate access protections. Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062, SRG-OS- 000042-GPOS-00020 Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_uid; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate UID: \"$l_uid\" Users: \"$(awk -F: '($3 == n) { print $1 }' n=$l_uid /etc/passwd | xargs)\"" fi done < <(cut -f3 -d":" /etc/passwd | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique UIDs and review all files owned by the shared UIDs to determine which UID they are supposed to belong to. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 2. NIST SP 800-53A :: IA-2.1 Page 979 Internal Only - General Additional Information: Red Hat Enterprise Linux 8 Security Technical Implementation Guide Version 1, Release: 14 Benchmark Date: 24 APR 2024 Vul ID: V-230371 Rule ID: SV-230371r627750 STIG ID: RHEL-08-020240 Severity: CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 980 Internal Only - General 7.2.6 Ensure no duplicate GIDs exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the groupadd program will not let you create a duplicate Group ID (GID), it is possible for an administrator to manually edit the /etc/group file and change the GID field. Rationale: User groups must be assigned unique GIDs for accountability and to ensure appropriate access protections. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_gid; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate GID: \"$l_gid\" Groups: \"$(awk -F: '($3 == n) { print $1 }' n=$l_gid /etc/group | xargs)\"" fi done < <(cut -f3 -d":" /etc/group | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique GIDs and review all files owned by the shared GID to determine which group they are supposed to belong to. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Additional Information: You can also use the grpck command to check for other inconsistencies in the /etc/group file. Page 981 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 982 Internal Only - General 7.2.7 Ensure no duplicate user names exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the useradd program will not let you create a duplicate user name, it is possible for an administrator to manually edit the /etc/passwd file and change the user name. Rationale: If a user is assigned a duplicate user name, it will create and have access to files with the first UID for that username in /etc/passwd . For example, if "test4" has a UID of 1000 and a subsequent "test4" entry has a UID of 2000, logging in as "test4" will use UID 1000. Effectively, the UID is shared, which is a security problem. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_user; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate User: \"$l_user\" Users: \"$(awk -F: '($1 == n) { print $1 }' n=$l_user /etc/passwd | xargs)\"" fi done < <(cut -f1 -d":" /etc/passwd | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique user names for the users. File ownerships will automatically reflect the change as long as the users have unique UIDs. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 983 Internal Only - General 7.2.8 Ensure no duplicate group names exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the groupadd program will not let you create a duplicate group name, it is possible for an administrator to manually edit the /etc/group file and change the group name. Rationale: If a group is assigned a duplicate group name, it will create and have access to files with the first GID for that group in /etc/group . Effectively, the GID is shared, which is a security problem. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_group; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate Group: \"$l_group\" Groups: \"$(awk -F: '($1 == n) { print $1 }' n=$l_group /etc/group | xargs)\"" fi done < <(cut -f1 -d":" /etc/group | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique names for the user groups. File group ownerships will automatically reflect the change as long as the groups have unique GIDs. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 984 Internal Only - General 7.2.9 Ensure local interactive user home directories are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user home directory is space defined for the particular user to set local environment variables and to store personal files. While the system administrator can establish secure permissions for users' home directories, the users can easily override these. Users can be defined in /etc/passwd without a home directory or with a home directory that does not actually exist. Rationale: Since the user is accountable for files stored in the user home directory, the user must be the owner of the directory. Group or world-writable user home directories may enable malicious users to steal or modify other users' data or to gain another user's system privileges. If the user's home directory does not exist or is unassigned, the user will be placed in "/" and will not be able to write any files or have local environment variables set. Audit: Run the following script to Ensure: • local interactive user home directories exist • Ensure local interactive users own their home directories • Ensure local interactive user home directories are mode 750 or more restrictive Page 985 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_exists2=() a_mode2=() a_owner2=() l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" l_mask='0027'; l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" l_users="$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd | wc -l)" [ "$l_users" -gt 10000 ] && printf '%s\n' "" " ** INFO **" \ " $l_users Local interactive users found on the system" " This may be a long running check" " **********" while IFS=" " read -r l_user l_home; do if [ -d "$l_home" ]; then while IFS=: read -r l_own l_mode; do [ "$l_user" != "$l_own" ] && a_owner2+=(" - User: \"$l_user\" Home \"$l_home\" is owned by: \"$l_own\"") [ $(( $l_mode & $l_mask )) -gt 0 ] && a_mode2+=(" - User: \"$l_user\" Home \"$l_home\" is mode: \"$l_mode\"" \ " should be mode: \"$l_max\" or more restrictive") done <<< "$(stat -Lc '%U:%#a' "$l_home")" else a_exists2+=(" - User: \"$l_user\" Home Directory: \"$l_home\" Doesn't exist") fi done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" [ "${#a_exists2[@]}" -gt 0 ] && a_output2+=("${a_exists2[@]}") || \ a_output+=(" - All interactive users home directories exist") [ "${#a_mode2[@]}" -gt 0 ] && a_output2+=("${a_mode2[@]}") || \ a_output+=(" - All interactive users home directories are mode \"$l_max\" or more restrictive") [ "${#a_owner2[@]}" -gt 0 ] && a_output2+=("${a_owner2[@]}") || \ a_output+=(" - All interactive users own their home directory") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 986 Internal Only - General Remediation: If a local interactive users' home directory is undefined and/or doesn't exist, follow local site policy and perform one of the following: • Lock the user account • Remove the user from the system • create a directory for the user. If undefined, edit /etc/passwd and add the absolute path to the directory to the last field of the user. Run the following script to: • Remove excessive permissions from local interactive users home directories • Update the home directory's owner #!/usr/bin/env bash { a_output=() a_output2=() a_exists2=() a_mode2=() a_owner2=() l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" l_mask='0027'; l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" l_users="$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd | wc -l)" [ "$l_users" -gt 10000 ] && printf '%s\n' "" " ** INFO **" \ " $l_users Local interactive users found on the system" " This may be a long running process" " **********" while IFS=" " read -r l_user l_home; do if [ -d "$l_home" ]; then while IFS=: read -r l_own l_mode; do if [ "$l_user" != "$l_own" ]; then a_owner2+=(" - User: \"$l_user\" Home \"$l_home\" is owned by: \"$l_own\"" \ " changing owner to: \"$l_user\"") && chown "$l_user" "$l_home" fi if [ $(( $l_mode & $l_mask )) -gt 0 ]; then a_mode2+=(" - User: \"$l_user\" Home \"$l_home\" is mode: \"$l_mode\"" \ " changing to mode: \"$l_max\" or more restrictive") chmod g-w,o-rwx "$l_home" fi done <<< "$(stat -Lc '%U:%#a' "$l_home")" else a_exists2+=(" - User: \"$l_user\" Home Directory: \"$l_home\" Doesn't exist") fi done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" [ "${#a_exists2[@]}" -gt 0 ] && a_output2+=("${a_exists2[@]}") [ "${#a_mode2[@]}" -gt 0 ] && a_output2+=("${a_mode2[@]}") [ "${#a_owner2[@]}" -gt 0 ] && a_output2+=("${a_owner2[@]}") if [ "${#a_output2[@]}" -gt 0 ]; then printf '%s\n' "" "${a_output2[@]}" else printf '%s\n' "" "- No changes required" fi } Page 987 Internal Only - General References: 1. NIST SP 800-53 Revision 5 :: CM-6 b 2. NIST SP 800-53A :: CM-6.1 (iv) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 988 Internal Only - General 7.2.10 Ensure local interactive user dot files access is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: While the system administrator can establish secure permissions for users' "dot" files, the users can easily override these. • .forward file specifies an email address to forward the user's mail to. • .rhost file provides the "remote authentication" database for the rcp, rlogin, and rsh commands and the rcmd() function. These files bypass the standard password-based user authentication mechanism. They specify remote hosts and users that are considered trusted (i.e. are allowed to access the local system without supplying a password) • .netrc file contains data for logging into a remote host or passing authentication to an API. • .bash_history file keeps track of the user’s commands. Rationale: User configuration files with excessive or incorrect access may enable malicious users to steal or modify other users' data or to gain another user's system privileges. Audit: Run the following script to verify local interactive user dot files: • Don't include .forward, .rhost, or .netrc files • Are mode 0644 or more restrictive • Are owned by the local interactive user • Are group owned by the user's primary group • .bash_history is mode 0600 or more restrictive Note: If a .netrc file is required, and follows local site policy, it should be mode 0600 or more restrictive. Page 989 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=() l_maxsize="1000" # Maximum number of local interactive users before warning (Default 1,000) l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" a_user_and_home=() # Create array with local users and their home directories while read -r l_local_user l_local_user_home; do # Populate array with users and user home location [[ -n "$l_local_user" && -n "$l_local_user_home" ]] && a_user_and_home+=("$l_local_user:$l_local_user_home") done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" l_asize="${#a_user_and_home[@]}" # Here if we want to look at number of users before proceeding [ "${#a_user_and_home[@]}" -gt "$l_maxsize" ] && printf '%s\n' "" " ** INFO **" \ " - \"$l_asize\" Local interactive users found on the system" \ " - This may be a long running check" "" file_access_chk() { a_access_out=() l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" if [ $(( $l_mode & $l_mask )) -gt 0 ]; then a_access_out+=(" - File: \"$l_hdfile\" is mode: \"$l_mode\" and should be mode: \"$l_max\" or more restrictive") fi if [[ ! "$l_owner" =~ ($l_user) ]]; then a_access_out+=(" - File: \"$l_hdfile\" owned by: \"$l_owner\" and should be owned by \"${l_user//|/ or }\"") fi if [[ ! "$l_gowner" =~ ($l_group) ]]; then a_access_out+=(" - File: \"$l_hdfile\" group owned by: \"$l_gowner\" and should be group owned by \"${l_group//|/ or }\"") fi } while IFS=: read -r l_user l_home; do a_dot_file=(); a_netrc=(); a_netrc_warn=(); a_bhout=(); a_hdirout=() if [ -d "$l_home" ]; then l_group="$(id -gn "$l_user" | xargs)";l_group="${l_group// /|}" while IFS= read -r -d $'\0' l_hdfile; do while read -r l_mode l_owner l_gowner; do case "$(basename "$l_hdfile")" in .forward | .rhost ) a_dot_file+=(" - File: \"$l_hdfile\" exists") ;; .netrc ) l_mask='0177'; file_access_chk if [ "${#a_access_out[@]}" -gt 0 ]; then a_netrc+=("${a_access_out[@]}") else a_netrc_warn+=(" - File: \"$l_hdfile\" exists") fi ;; .bash_history ) l_mask='0177'; file_access_chk [ "${#a_access_out[@]}" -gt 0 ] && a_bhout+=("${a_access_out[@]}") ;; * ) l_mask='0133'; file_access_chk [ "${#a_access_out[@]}" -gt 0 ] && a_hdirout+=("${a_access_out[@]}") ;; esac done < <(stat -Lc '%#a %U %G' "$l_hdfile") Page 990 Internal Only - General done < <(find "$l_home" -xdev -type f -name '.*' -print0) fi if [[ "${#a_dot_file[@]}" -gt 0 || "${#a_netrc[@]}" -gt 0 || "${#a_bhout[@]}" - gt 0 || "${#a_hdirout[@]}" -gt 0 ]]; then a_output2+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_dot_file[@]}" "${a_netrc[@]}" "${a_bhout[@]}" "${a_hdirout[@]}") fi [ "${#a_netrc_warn[@]}" -gt 0 ] && a_output3+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_netrc_warn[@]}") done <<< "$(printf '%s\n' "${a_user_and_home[@]}")" if [ "${#a_output2[@]}" -le 0 ]; then # If l_output2 is empty, we pass [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' " ** WARNING **" "${a_output3[@]}" printf '%s\n' "- Audit Result:" " ** PASS **" else printf '%s\n' "- Audit Result:" " ** FAIL **" " - * Reasons for audit failure * :" "${a_output2[@]}" "" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' " ** WARNING **" "${a_output3[@]}" fi } Page 991 Internal Only - General Remediation: Making global modifications to users' files without alerting the user community can result in unexpected outages and unhappy users. Therefore, it is recommended that a monitoring policy be established to report user dot file permissions and determine the action to be taken in accordance with site policy. The following script will: • remove excessive permissions on dot files within interactive users' home directories • change ownership of dot files within interactive users' home directories to the user • change group ownership of dot files within interactive users' home directories to the user's primary group • list .forward and .rhost files to be investigated and manually deleted Page 992 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=() l_maxsize="1000" # Maximum number of local interactive users before warning (Default 1,000) l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" a_user_and_home=() # Create array with local users and their home directories while read -r l_local_user l_local_user_home; do # Populate array with users and user home location [[ -n "$l_local_user" && -n "$l_local_user_home" ]] && a_user_and_home+=("$l_local_user:$l_local_user_home") done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" l_asize="${#a_user_and_home[@]}" # Here if we want to look at number of users before proceeding [ "${#a_user_and_home[@]}" -gt "$l_maxsize" ] && printf '%s\n' "" " ** INFO **" \ " - \"$l_asize\" Local interactive users found on the system" \ " - This may be a long running check" "" file_access_fix() { a_access_out=() l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" if [ $(( $l_mode & $l_mask )) -gt 0 ]; then printf '%s\n' "" " - File: \"$l_hdfile\" is mode: \"$l_mode\" and should be mode: \"$l_max\" or more restrictive" \ " Updating file: \"$l_hdfile\" to be mode: \"$l_max\" or more restrictive" chmod "$l_change" "$l_hdfile" fi if [[ ! "$l_owner" =~ ($l_user) ]]; then printf '%s\n' "" " - File: \"$l_hdfile\" owned by: \"$l_owner\" and should be owned by \"${l_user//|/ or }\"" \ " Updating file: \"$l_hdfile\" to be owned by \"${l_user//|/ or }\"" chown "$l_user" "$l_hdfile" fi if [[ ! "$l_gowner" =~ ($l_group) ]]; then printf '%s\n' "" " - File: \"$l_hdfile\" group owned by: \"$l_gowner\" and should be group owned by \"${l_group//|/ or }\"" \ " Updating file: \"$l_hdfile\" to be group owned by \"${l_group//|/ or }\"" chgrp "$l_group" "$l_hdfile" fi } while IFS=: read -r l_user l_home; do a_dot_file=(); a_netrc=(); a_netrc_warn=(); a_bhout=(); a_hdirout=() if [ -d "$l_home" ]; then l_group="$(id -gn "$l_user" | xargs)";l_group="${l_group// /|}" while IFS= read -r -d $'\0' l_hdfile; do while read -r l_mode l_owner l_gowner; do case "$(basename "$l_hdfile")" in .forward | .rhost ) Page 993 Internal Only - General a_dot_file+=(" - File: \"$l_hdfile\" exists" " Please review and manually delete this file") ;; .netrc ) l_mask='0177'; l_change="u-x,go-rwx"; file_access_fix a_netrc_warn+=(" - File: \"$l_hdfile\" exists") ;; .bash_history ) l_mask='0177'; l_change="u-x,go-rwx"; file_access_fix ;; * ) l_mask='0133'; l_change="u-x,go-wx"; file_access_fix ;; esac done < <(stat -Lc '%#a %U %G' "$l_hdfile") done < <(find "$l_home" -xdev -type f -name '.*' -print0) fi [ "${#a_dot_file[@]}" -gt 0 ] && a_output2+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_dot_file[@]}") [ "${#a_netrc_warn[@]}" -gt 0 ] && a_output3+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_netrc_warn[@]}") done <<< "$(printf '%s\n' "${a_user_and_home[@]}")" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " ** WARNING **" "${a_output3[@]}" "" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" } References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 994 Internal Only - General Appendix: Summary Table CIS Benchmark Recommendation Set Correctly Yes No 1 Initial Setup 1.1 Filesystem 1.1.1 Configure Filesystem Kernel Modules 1.1.1.1 Ensure cramfs kernel module is not available   (Automated) 1.1.1.2 Ensure freevxfs kernel module is not available   (Automated) 1.1.1.3 Ensure hfs kernel module is not available (Automated)   1.1.1.4 Ensure hfsplus kernel module is not available   (Automated) 1.1.1.5 Ensure jffs2 kernel module is not available (Automated)   1.1.1.6 Ensure overlay kernel module is not available   (Automated) 1.1.1.7 Ensure squashfs kernel module is not available   (Automated) 1.1.1.8 Ensure udf kernel module is not available (Automated)   1.1.1.9 Ensure firewire-core kernel module is not available   (Automated) 1.1.1.10 Ensure usb-storage kernel module is not available   (Automated) 1.1.1.11 Ensure unused filesystems kernel modules are not   available (Manual) 1.1.2 Configure Filesystem Partitions 1.1.2.1 Configure /tmp 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated)   1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated)   1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated)   1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated)   1.1.2.2 Configure /dev/shm 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   (Automated) 1.1.2.2.2 Ensure nodev option set on /dev/shm partition   (Automated) 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   (Automated) 1.1.2.2.4 Ensure noexec option set on /dev/shm partition   (Automated) 1.1.2.3 Configure /home 1.1.2.3.1 Ensure separate partition exists for /home (Automated)   Page 995 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.1.2.3.2 Ensure nodev option set on /home partition (Automated)   1.1.2.3.3 Ensure nosuid option set on /home partition (Automated)   1.1.2.4 Configure /var 1.1.2.4.1 Ensure separate partition exists for /var (Automated)   1.1.2.4.2 Ensure nodev option set on /var partition (Automated)   1.1.2.4.3 Ensure nosuid option set on /var partition (Automated)   1.1.2.5 Configure /var/tmp 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated)   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   (Automated) 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   (Automated) 1.1.2.5.4 Ensure noexec option set on /var/tmp partition   (Automated) 1.1.2.6 Configure /var/log 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated)   1.1.2.6.2 Ensure nodev option set on /var/log partition   (Automated) 1.1.2.6.3 Ensure nosuid option set on /var/log partition   (Automated) 1.1.2.6.4 Ensure noexec option set on /var/log partition   (Automated) 1.1.2.7 Configure /var/log/audit 1.1.2.7.1 Ensure separate partition exists for /var/log/audit   (Automated) 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   (Automated) 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   (Automated) 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   (Automated) 1.2 Package Management 1.2.1 Configure Package Repositories 1.2.1.1 Ensure the source.list and .source files use the Signed-   By option (Manual) 1.2.1.2 Ensure weak dependencies are configured (Automated)   1.2.1.3 Ensure access to gpg key files are configured   (Automated) 1.2.1.4 Ensure access to /etc/apt/trusted.gpg.d directory is   configured (Automated) 1.2.1.5 Ensure access to /etc/apt/auth.conf.d directory is   configured (Automated) Page 996 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured (Automated) 1.2.1.7 Ensure access to /usr/share/keyrings directory is   configured (Automated) 1.2.1.8 Ensure access to /etc/apt/sources.list.d directory is   configured (Automated) 1.2.1.9 Ensure access to files in /etc/apt/sources.list.d are   configured (Automated) 1.2.2 Configure Package Updates 1.2.2.1 Ensure updates, patches, and additional security   software are installed (Manual) 1.3 Mandatory Access Control 1.3.1 Configure AppArmor 1.3.1.1 Ensure apparmor packages are installed (Automated)   1.3.1.2 Ensure AppArmor is enabled (Automated)   1.3.1.3 Ensure all AppArmor Profiles are enforcing (Automated)   1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is   enabled (Automated) 1.4 Configure Bootloader 1.4.1 Ensure bootloader password is set (Automated)   1.4.2 Ensure access to bootloader config is configured   (Automated) 1.5 Configure Additional Process Hardening 1.5.1 Ensure fs.protected_hardlinks is configured (Automated)   1.5.2 Ensure fs.protected_symlinks is configured (Automated)   1.5.3 Ensure kernel.yama.ptrace_scope is configured   (Automated) 1.5.4 Ensure fs.suid_dumpable is configured (Automated)   1.5.5 Ensure kernel.dmesg_restrict is configured (Automated)   1.5.6 Ensure prelink is not installed (Automated)   1.5.7 Ensure Automatic Error Reporting is configured   (Automated) 1.5.8 Ensure kernel.kptr_restrict is configured (Automated)   1.5.9 Ensure kernel.randomize_va_space is configured   (Automated) 1.5.10 Ensure kernel.yama.ptrace_scope is configured   (Automated) 1.5.11 Ensure core file size is configured (Automated)   1.5.12 Ensure systemd-coredump ProcessSizeMax is   configured (Automated) 1.5.13 Ensure systemd-coredump Storage is configured   (Automated) Page 997 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.6 Configure Command Line Warning Banners 1.6.1 Ensure /etc/motd is configured (Automated)   1.6.2 Ensure /etc/issue is configured (Automated)   1.6.3 Ensure /etc/issue.net is configured (Automated)   1.6.4 Ensure access to /etc/motd is configured (Automated)   1.6.5 Ensure access to /etc/issue is configured (Automated)   1.6.6 Ensure access to /etc/issue.net is configured   (Automated) 1.7 Configure GNOME Display Manager 1.7.1 Ensure GDM is removed (Automated)   1.7.2 Ensure GDM login banner is configured (Automated)   1.7.3 Ensure GDM disable-user-list option is enabled   (Automated) 1.7.4 Ensure GDM screen locks when the user is idle   (Automated) 1.7.5 Ensure GDM screen locks cannot be overridden   (Automated) 1.7.6 Ensure GDM automatic mounting of removable media is   disabled (Automated) 1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden (Automated) 1.7.8 Ensure GDM autorun-never is enabled (Automated)   1.7.9 Ensure GDM autorun-never is not overridden   (Automated) 1.7.10 Ensure XDMCP is not enabled (Automated)   1.7.11 Ensure Xwayland is configured (Automated)   2 Services 2.1 Configure Server Services 2.1.1 Ensure autofs services are not in use (Automated)   2.1.2 Ensure avahi daemon services are not in use   (Automated) 2.1.3 Ensure dhcp server services are not in use (Automated)   2.1.4 Ensure dns server services are not in use (Automated)   2.1.5 Ensure dnsmasq services are not in use (Automated)   2.1.6 Ensure ftp server services are not in use (Automated)   2.1.7 Ensure ldap server services are not in use (Automated)   2.1.8 Ensure message access server services are not in use   (Automated) 2.1.9 Ensure network file system services are not in use   (Automated) 2.1.10 Ensure nis server services are not in use (Automated)   2.1.11 Ensure print server services are not in use (Automated)   Page 998 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 2.1.12 Ensure rpcbind services are not in use (Automated)   2.1.13 Ensure rsync services are not in use (Automated)   2.1.14 Ensure samba file server services are not in use   (Automated) 2.1.15 Ensure snmp services are not in use (Automated)   2.1.16 Ensure telnet-server services are not in use (Automated)   2.1.17 Ensure tftp server services are not in use (Automated)   2.1.18 Ensure web proxy server services are not in use   (Automated) 2.1.19 Ensure web server services are not in use (Automated)   2.1.20 Ensure xinetd services are not in use (Automated)   2.1.21 Ensure X window server services are not in use   (Automated) 2.1.22 Ensure mail transfer agents are configured for local-only   mode (Automated) 2.1.23 Ensure only approved services are listening on a   network interface (Manual) 2.2 Configure Client Services 2.2.1 Ensure nis client is not installed (Automated)   2.2.2 Ensure rsh client is not installed (Automated)   2.2.3 Ensure talk client is not installed (Automated)   2.2.4 Ensure telnet client is not installed (Automated)   2.2.5 Ensure ldap client is not installed (Automated)   2.2.6 Ensure ftp client is not installed (Automated)   2.3 Configure Time Synchronization 2.3.1 Ensure time synchronization is in use 2.3.1.1 Ensure a single time synchronization daemon is in use   (Automated) 2.3.2 Configure systemd-timesyncd 2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver (Automated) 2.3.2.2 Ensure systemd-timesyncd is enabled and running   (Automated) 2.3.3 Configure chrony 2.3.3.1 Ensure chrony is configured with authorized timeserver   (Automated) 2.3.3.2 Ensure chrony is running as user _chrony (Automated)   2.3.3.3 Ensure chrony is enabled and running (Automated)   2.4 Job Schedulers 2.4.1 Configure cron 2.4.1.1 Ensure cron daemon is enabled and active (Automated)   2.4.1.2 Ensure access to /etc/crontab is configured (Automated)   Page 999 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 2.4.1.3 Ensure access to /etc/cron.hourly is configured   (Automated) 2.4.1.4 Ensure access to /etc/cron.daily is configured   (Automated) 2.4.1.5 Ensure access to /etc/cron.weekly is configured   (Automated) 2.4.1.6 Ensure access to /etc/cron.monthly is configured   (Automated) 2.4.1.7 Ensure access to /etc/cron.yearly is configured   (Automated) 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated)   2.4.1.9 Ensure access to crontab is configured (Automated)   2.4.2 Configure at 2.4.2.1 Ensure access to at is configured (Automated)   3 Network 3.1 Configure Network Devices 3.1.1 Ensure IPv6 status is identified (Manual)   3.1.2 Ensure wireless interfaces are not available (Automated)   3.1.3 Ensure bluetooth services are not in use (Automated)   3.2 Configure Network Kernel Modules 3.2.1 Ensure atm kernel module is not available (Automated)   3.2.2 Ensure can kernel module is not available (Automated)   3.2.3 Ensure dccp kernel module is not available (Automated)   3.2.4 Ensure rds kernel module is not available (Automated)   3.2.5 Ensure sctp kernel module is not available (Automated)   3.2.6 Ensure tipc kernel module is not available (Automated)   3.3 Configure Network Kernel Parameters 3.3.1 Configure IPv4 parameters 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated)   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   (Automated) 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   (Automated) 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   (Automated) 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   (Automated) 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured (Automated) 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured (Automated) Page 1000 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   (Automated) 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured (Automated) 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   (Automated) 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured (Automated) 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   (Automated) 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   (Automated) 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured (Automated) 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured (Automated) 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   (Automated) 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   (Automated) 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   (Automated) 3.3.2 Configure IPv6 parameters 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   (Automated) 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   (Automated) 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   (Automated) 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured (Automated) 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured (Automated) 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured (Automated) 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   (Automated) 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   (Automated) 4 Host Based Firewall 4.1 Configure Uncomplicated Firewall 4.1.1 Ensure ufw is installed (Automated)   Page 1001 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 4.1.2 Ensure ufw service is configured (Automated)   4.1.3 Ensure ufw incoming default is configured (Automated)   4.1.4 Ensure ufw outgoing default is configured (Automated)   4.1.5 Ensure ufw routed default is configured (Automated)   5 Access Control 5.1 Configure SSH Server 5.1.1 Ensure access to /etc/ssh/sshd_config is configured   (Automated) 5.1.2 Ensure access to SSH private host key files is   configured (Automated) 5.1.3 Ensure access to SSH public host key files is configured   (Automated) 5.1.4 Ensure sshd access is configured (Automated)   5.1.5 Ensure sshd Banner is configured (Automated)   5.1.6 Ensure sshd Ciphers are configured (Automated)   5.1.7 Ensure sshd ClientAliveInterval and   ClientAliveCountMax are configured (Automated) 5.1.8 Ensure sshd DisableForwarding is enabled (Automated)   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   (Automated) 5.1.10 Ensure sshd HostbasedAuthentication is disabled   (Automated) 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated)   5.1.12 Ensure sshd KexAlgorithms is configured (Automated)   5.1.13 Ensure sshd post-quantum cryptography key exchange   algorithms are configured (Automated) 5.1.14 Ensure sshd LoginGraceTime is configured (Automated)   5.1.15 Ensure sshd LogLevel is configured (Automated)   5.1.16 Ensure sshd MACs are configured (Automated)   5.1.17 Ensure sshd MaxAuthTries is configured (Automated)   5.1.18 Ensure sshd MaxSessions is configured (Automated)   5.1.19 Ensure sshd MaxStartups is configured (Automated)   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   (Automated) 5.1.21 Ensure sshd PermitRootLogin is disabled (Automated)   5.1.22 Ensure sshd PermitUserEnvironment is disabled   (Automated) 5.1.23 Ensure sshd UsePAM is enabled (Automated)   5.2 Configure privilege escalation 5.2.1 Ensure sudo is installed (Automated)   5.2.2 Ensure sudo commands use pty (Automated)   5.2.3 Ensure sudo log file exists (Automated)   Page 1002 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.2.4 Ensure users must provide password for escalation   (Automated) 5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally (Automated) 5.2.6 Ensure sudo timestamp_timeout is configured   (Automated) 5.2.7 Ensure access to the su command is restricted   (Automated) 5.3 Pluggable Authentication Modules 5.3.1 Configure PAM software packages 5.3.1.1 Ensure latest version of pam is installed (Automated)   5.3.1.2 Ensure latest version of libpam-modules is installed   (Automated) 5.3.1.3 Ensure latest version of libpam-pwquality is installed   (Automated) 5.3.2 Configure pam-auth-update profiles 5.3.2.1 Ensure pam_unix module is enabled (Automated)   5.3.2.2 Ensure pam_faillock module is enabled (Automated)   5.3.2.3 Ensure pam_pwquality module is enabled (Automated)   5.3.2.4 Ensure pam_pwhistory module is enabled (Automated)   5.3.3 Configure PAM Arguments 5.3.3.1 Configure pam_faillock module 5.3.3.1.1 Ensure password failed attempts lockout is configured   (Automated) 5.3.3.1.2 Ensure password unlock time is configured (Automated)   5.3.3.1.3 Ensure password failed attempts lockout includes root   account (Automated) 5.3.3.2 Configure pam_pwquality module 5.3.3.2.1 Ensure password number of changed characters is   configured (Automated) 5.3.3.2.2 Ensure password length is configured (Automated)   5.3.3.2.3 Ensure password complexity is configured (Manual)   5.3.3.2.4 Ensure password same consecutive characters is   configured (Automated) 5.3.3.2.5 Ensure password maximum sequential characters is   configured (Automated) 5.3.3.2.6 Ensure password dictionary check is enabled   (Automated) 5.3.3.2.7 Ensure password quality checking is enforced   (Automated) 5.3.3.2.8 Ensure password quality is enforced for the root user   (Automated) Page 1003 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.3.3.3 Configure pam_pwhistory module 5.3.3.3.1 Ensure password history remember is configured   (Automated) 5.3.3.3.2 Ensure password history is enforced for the root user   (Automated) 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   (Automated) 5.3.3.4 Configure pam_unix module 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated)   5.3.3.4.2 Ensure pam_unix does not include remember   (Automated) 5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm (Automated) 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated)   5.4 User Accounts and Environment 5.4.1 Configure shadow password suite parameters 5.4.1.1 Ensure password expiration is configured (Automated)   5.4.1.2 Ensure minimum password days is configured (Manual)   5.4.1.3 Ensure password expiration warning days is configured   (Automated) 5.4.1.4 Ensure strong password hashing algorithm is configured   (Automated) 5.4.1.5 Ensure inactive password lock is configured (Automated)   5.4.1.6 Ensure all users last password change date is in the past   (Automated) 5.4.2 Configure root and system accounts and environment 5.4.2.1 Ensure root is the only UID 0 account (Automated)   5.4.2.2 Ensure root is the only GID 0 account (Automated)   5.4.2.3 Ensure group root is the only GID 0 group (Automated)   5.4.2.4 Ensure root account access is controlled (Automated)   5.4.2.5 Ensure root path integrity (Automated)   5.4.2.6 Ensure root user umask is configured (Automated)   5.4.2.7 Ensure system accounts do not have a valid login shell   (Automated) 5.4.2.8 Ensure accounts without a valid login shell are locked   (Automated) 5.4.3 Configure user default environment 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated)   5.4.3.2 Ensure default user shell timeout is configured   (Automated) 5.4.3.3 Ensure default user umask is configured (Automated)   6 Logging and Auditing Page 1004 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.1 System Logging 6.1.1 Configure journald 6.1.1.1 Configure systemd-journald service 6.1.1.1.1 Ensure journald service is active (Automated)   6.1.1.1.2 Ensure journald log file access is configured (Manual)   6.1.1.1.3 Ensure journald log file rotation is configured (Manual)   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   (Automated) 6.1.1.1.5 Ensure journald Storage is configured (Automated)   6.1.1.1.6 Ensure journald Compress is configured (Automated)   6.1.1.2 Configure systemd-journal-remote 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated)   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured (Manual) 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   (Automated) 6.1.1.2.4 Ensure systemd-journal-remote service is not in use   (Automated) 6.1.2 Configure rsyslog 6.1.2.1 Ensure rsyslog is installed (Automated)   6.1.2.2 Ensure rsyslog service is enabled and active   (Automated) 6.1.2.3 Ensure journald is configured to send logs to rsyslog   (Automated) 6.1.2.4 Ensure rsyslog log file creation mode is configured   (Automated) 6.1.2.5 Ensure rsyslog logging is configured (Manual)   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host (Manual) 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client (Automated) 6.1.2.8 Ensure logrotate is configured (Manual)   6.1.2.9 Ensure rsyslog-gnutls is installed (Automated)   6.1.2.10 Ensure rsyslog forwarding uses gtls (Automated)   6.1.2.11 Ensure rsyslog CA certificates are configured (Manual)   6.1.3 Configure Logfiles 6.1.3.1 Ensure access to all logfiles has been configured   (Automated) 6.2 System Auditing 6.2.1 Configure auditd Service 6.2.1.1 Ensure auditd packages are installed (Automated)   6.2.1.2 Ensure auditd service is enabled and active (Automated)   Page 1005 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled (Automated) 6.2.1.4 Ensure audit_backlog_limit is configured (Automated)   6.2.2 Configure Data Retention 6.2.2.1 Ensure audit log storage size is configured (Automated)   6.2.2.2 Ensure audit logs are not automatically deleted   (Automated) 6.2.2.3 Ensure system is disabled when audit logs are full   (Automated) 6.2.2.4 Ensure system warns when audit logs are low on space   (Automated) 6.2.3 Configure auditd Rules 6.2.3.1 Ensure modification of the /etc/sudoers file is collected   (Automated) 6.2.3.2 Ensure actions as another user are always logged   (Automated) 6.2.3.3 Ensure events that modify the sudo log file are collected   (Automated) 6.2.3.4 Ensure events that modify date and time information are   collected (Automated) 6.2.3.5 Ensure events that modify sethostname and   setdomainname are collected (Automated) 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net   are collected (Automated) 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname   are collected (Automated) 6.2.3.8 Ensure events that modify the system's network   environment are collected (Automated) 6.2.3.9 Ensure events that modify /etc/NetworkManager   directory are collected (Automated) 6.2.3.10 Ensure use of privileged commands are collected   (Automated) 6.2.3.11 Ensure unsuccessful file access attempts are collected   (Automated) 6.2.3.12 Ensure events that modify /etc/group information are   collected (Automated) 6.2.3.13 Ensure events that modify /etc/passwd information are   collected (Automated) 6.2.3.14 Ensure events that modify /etc/shadow and   /etc/gshadow are collected (Automated) 6.2.3.15 Ensure events that modify /etc/security/opasswd are   collected (Automated) Page 1006 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are   collected (Automated) 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/   information are collected (Automated) 6.2.3.18 Ensure discretionary access control permission   modification events chmod,fchmod,fchmodat,fchmodat2 are collected (Automated) 6.2.3.19 Ensure discretionary access control permission   modification events chown,fchown,lchown,fchownat are collected (Automated) 6.2.3.20 Ensure discretionary access control permission   modification events setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremo vexattr collected (Automated) 6.2.3.21 Ensure successful file system mounts are collected   (Automated) 6.2.3.22 Ensure session initiation information is collected   (Automated) 6.2.3.23 Ensure login and logout events are collected   (Automated) 6.2.3.24 Ensure unlink file deletion events by users are collected   (Automated) 6.2.3.25 Ensure rename file deletion events by users are   collected (Automated) 6.2.3.26 Ensure events that modify the system's Mandatory   Access Controls are collected (Automated) 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected (Automated) 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected (Automated) 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected (Automated) 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected (Automated) 6.2.3.31 Ensure kernel module loading unloading and   modification is collected (Automated) 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected (Automated) 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected (Automated) 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected (Automated) Page 1007 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors (Automated) 6.2.3.36 Ensure the audit configuration is immutable (Automated)   6.2.3.37 Ensure the running and on disk configuration is the same   (Manual) 6.2.4 Configure auditd File Access 6.2.4.1 Ensure audit log files mode is configured (Automated)   6.2.4.2 Ensure audit log files owner is configured (Automated)   6.2.4.3 Ensure audit log files group owner is configured   (Automated) 6.2.4.4 Ensure the audit log file directory mode is configured   (Automated) 6.2.4.5 Ensure audit configuration files mode is configured   (Automated) 6.2.4.6 Ensure audit configuration files owner is configured   (Automated) 6.2.4.7 Ensure audit configuration files group owner is   configured (Automated) 6.2.4.8 Ensure audit tools mode is configured (Automated)   6.2.4.9 Ensure audit tools owner is configured (Automated)   6.2.4.10 Ensure audit tools group owner is configured   (Automated) 6.3 Configure Integrity Checking 6.3.1 Ensure AIDE is installed (Automated)   6.3.2 Ensure filesystem integrity is regularly checked   (Automated) 6.3.3 Ensure cryptographic mechanisms are used to protect   the integrity of audit tools (Automated) 7 System Maintenance 7.1 Configure system file and directory access 7.1.1 Ensure access to /etc/passwd is configured (Automated)   7.1.2 Ensure access to /etc/passwd- is configured   (Automated) 7.1.3 Ensure access to /etc/group is configured (Automated)   7.1.4 Ensure access to /etc/group- is configured (Automated)   7.1.5 Ensure access to /etc/shadow is configured (Automated)   7.1.6 Ensure access to /etc/shadow- is configured   (Automated) 7.1.7 Ensure access to /etc/gshadow is configured   (Automated) 7.1.8 Ensure access to /etc/gshadow- is configured   (Automated) Page 1008 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 7.1.9 Ensure access to /etc/shells is configured (Automated)   7.1.10 Ensure access to /etc/security/opasswd is configured   (Automated) 7.1.11 Ensure world writable files and directories are secured   (Automated) 7.1.12 Ensure no files or directories without an owner and a   group exist (Automated) 7.1.13 Ensure SUID and SGID files are reviewed (Manual)   7.2 Local User and Group Settings 7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords (Automated) 7.2.2 Ensure /etc/shadow password fields are not empty   (Automated) 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   (Automated) 7.2.4 Ensure shadow group is empty (Automated)   7.2.5 Ensure no duplicate UIDs exist (Automated)   7.2.6 Ensure no duplicate GIDs exist (Automated)   7.2.7 Ensure no duplicate user names exist (Automated)   7.2.8 Ensure no duplicate group names exist (Automated)   7.2.9 Ensure local interactive user home directories are   configured (Automated) 7.2.10 Ensure local interactive user dot files access is   configured (Automated) Page 1009 Internal Only - General Appendix: CIS Controls v7 IG 1 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   Page 1010 Internal Only - General Recommendation Set Correctly Yes No 1.5.5 Ensure kernel.dmesg_restrict is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   2.1.1 Ensure autofs services are not in use   2.1.16 Ensure telnet-server services are not in use   2.1.21 Ensure X window server services are not in use   2.2.1 Ensure nis client is not installed   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.15 Ensure sshd LogLevel is configured   5.1.21 Ensure sshd PermitRootLogin is disabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally Page 1011 Internal Only - General Recommendation Set Correctly Yes No 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.2.1 Ensure pam_unix module is enabled   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.10 Ensure use of privileged commands are collected   6.2.3.23 Ensure login and logout events are collected   6.2.3.24 Ensure unlink file deletion events by users are collected   6.2.3.25 Ensure rename file deletion events by users are collected   Page 1012 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.31 Ensure kernel module loading unloading and modification   is collected 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors 6.2.3.36 Ensure the audit configuration is immutable   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   Page 1013 Internal Only - General Recommendation Set Correctly Yes No 7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1014 Internal Only - General Appendix: CIS Controls v7 IG 2 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure firewire-core kernel module is not available   1.1.1.10 Ensure usb-storage kernel module is not available   1.1.1.11 Ensure unused filesystems kernel modules are not   available 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 1015 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is   enabled 1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.3 Ensure kernel.yama.ptrace_scope is configured   1.5.5 Ensure kernel.dmesg_restrict is configured   1.5.7 Ensure Automatic Error Reporting is configured   1.5.8 Ensure kernel.kptr_restrict is configured   1.5.9 Ensure kernel.randomize_va_space is configured   1.5.10 Ensure kernel.yama.ptrace_scope is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   Page 1016 Internal Only - General Recommendation Set Correctly Yes No 2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure telnet-server services are not in use   2.1.17 Ensure tftp server services are not in use   2.1.18 Ensure web proxy server services are not in use   2.1.19 Ensure web server services are not in use   2.1.20 Ensure xinetd services are not in use   2.1.21 Ensure X window server services are not in use   2.1.22 Ensure mail transfer agents are configured for local-only   mode 2.1.23 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.3 Ensure bluetooth services are not in use   Page 1017 Internal Only - General Recommendation Set Correctly Yes No 3.2.1 Ensure atm kernel module is not available   3.2.2 Ensure can kernel module is not available   3.2.3 Ensure dccp kernel module is not available   3.2.4 Ensure rds kernel module is not available   3.2.5 Ensure sctp kernel module is not available   3.2.6 Ensure tipc kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   Page 1018 Internal Only - General Recommendation Set Correctly Yes No 4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.13 Ensure sshd post-quantum cryptography key exchange   algorithms are configured 5.1.15 Ensure sshd LogLevel is configured   5.1.16 Ensure sshd MACs are configured   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   5.1.21 Ensure sshd PermitRootLogin is disabled   5.1.23 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured Page 1019 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.2.2 Ensure password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured Page 1020 Internal Only - General Recommendation Set Correctly Yes No 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.2.10 Ensure rsyslog forwarding uses gtls   6.1.2.11 Ensure rsyslog CA certificates are configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure modification of the /etc/sudoers file is collected   6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify sethostname and   setdomainname are collected 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net   are collected 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname   are collected 6.2.3.8 Ensure events that modify the system's network   environment are collected 6.2.3.9 Ensure events that modify /etc/NetworkManager   directory are collected 6.2.3.10 Ensure use of privileged commands are collected   Page 1021 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.12 Ensure events that modify /etc/group information are   collected 6.2.3.13 Ensure events that modify /etc/passwd information are   collected 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow   are collected 6.2.3.15 Ensure events that modify /etc/security/opasswd are   collected 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are   collected 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/   information are collected 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2   are collected 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are   collected 6.2.3.20 Ensure discretionary access control permission modification events   setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremo vexattr collected 6.2.3.21 Ensure successful file system mounts are collected   6.2.3.22 Ensure session initiation information is collected   6.2.3.23 Ensure login and logout events are collected   6.2.3.24 Ensure unlink file deletion events by users are collected   6.2.3.25 Ensure rename file deletion events by users are collected   6.2.3.26 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.31 Ensure kernel module loading unloading and modification   is collected 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected Page 1022 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors 6.2.3.36 Ensure the audit configuration is immutable   6.2.3.37 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1023 Internal Only - General Page 1024 Internal Only - General Appendix: CIS Controls v7 IG 3 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure firewire-core kernel module is not available   1.1.1.10 Ensure usb-storage kernel module is not available   1.1.1.11 Ensure unused filesystems kernel modules are not   available 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 1025 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is   enabled 1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.3 Ensure kernel.yama.ptrace_scope is configured   1.5.5 Ensure kernel.dmesg_restrict is configured   1.5.6 Ensure prelink is not installed   1.5.7 Ensure Automatic Error Reporting is configured   1.5.8 Ensure kernel.kptr_restrict is configured   1.5.9 Ensure kernel.randomize_va_space is configured   1.5.10 Ensure kernel.yama.ptrace_scope is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   Page 1026 Internal Only - General Recommendation Set Correctly Yes No 2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure telnet-server services are not in use   2.1.17 Ensure tftp server services are not in use   2.1.18 Ensure web proxy server services are not in use   2.1.19 Ensure web server services are not in use   2.1.20 Ensure xinetd services are not in use   2.1.21 Ensure X window server services are not in use   2.1.22 Ensure mail transfer agents are configured for local-only   mode 2.1.23 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   Page 1027 Internal Only - General Recommendation Set Correctly Yes No 3.1.2 Ensure wireless interfaces are not available   3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure atm kernel module is not available   3.2.2 Ensure can kernel module is not available   3.2.3 Ensure dccp kernel module is not available   3.2.4 Ensure rds kernel module is not available   3.2.5 Ensure sctp kernel module is not available   3.2.6 Ensure tipc kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured Page 1028 Internal Only - General Recommendation Set Correctly Yes No 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.13 Ensure sshd post-quantum cryptography key exchange   algorithms are configured 5.1.15 Ensure sshd LogLevel is configured   5.1.16 Ensure sshd MACs are configured   5.1.17 Ensure sshd MaxAuthTries is configured   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   5.1.21 Ensure sshd PermitRootLogin is disabled   5.1.23 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   Page 1029 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   Page 1030 Internal Only - General Recommendation Set Correctly Yes No 6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.2.10 Ensure rsyslog forwarding uses gtls   6.1.2.11 Ensure rsyslog CA certificates are configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure modification of the /etc/sudoers file is collected   6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify sethostname and   setdomainname are collected 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net   are collected 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname   are collected 6.2.3.8 Ensure events that modify the system's network   environment are collected Page 1031 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.9 Ensure events that modify /etc/NetworkManager   directory are collected 6.2.3.10 Ensure use of privileged commands are collected   6.2.3.11 Ensure unsuccessful file access attempts are collected   6.2.3.12 Ensure events that modify /etc/group information are   collected 6.2.3.13 Ensure events that modify /etc/passwd information are   collected 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow   are collected 6.2.3.15 Ensure events that modify /etc/security/opasswd are   collected 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are   collected 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/   information are collected 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2   are collected 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are   collected 6.2.3.20 Ensure discretionary access control permission modification events   setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremo vexattr collected 6.2.3.21 Ensure successful file system mounts are collected   6.2.3.22 Ensure session initiation information is collected   6.2.3.23 Ensure login and logout events are collected   6.2.3.24 Ensure unlink file deletion events by users are collected   6.2.3.25 Ensure rename file deletion events by users are collected   6.2.3.26 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected Page 1032 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.31 Ensure kernel module loading unloading and modification   is collected 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors 6.2.3.36 Ensure the audit configuration is immutable   6.2.3.37 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   6.3.1 Ensure AIDE is installed   6.3.2 Ensure filesystem integrity is regularly checked   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords Page 1033 Internal Only - General Recommendation Set Correctly Yes No 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1034 Internal Only - General Appendix: CIS Controls v7 Unmapped Recommendations Recommendation Set Correctly Yes No 1.2.1.2 Ensure weak dependencies are configured   1.2.1.3 Ensure access to gpg key files are configured   1.2.1.4 Ensure access to /etc/apt/trusted.gpg.d directory is   configured 1.2.1.5 Ensure access to /etc/apt/auth.conf.d directory is   configured 1.2.1.7 Ensure access to /usr/share/keyrings directory is   configured 1.2.1.8 Ensure access to /etc/apt/sources.list.d directory is   configured 1.2.1.9 Ensure access to files in /etc/apt/sources.list.d are   configured 1.7.2 Ensure GDM login banner is configured   1.7.3 Ensure GDM disable-user-list option is enabled   1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden 2.4.1.7 Ensure access to /etc/cron.yearly is configured   6.2.2.3 Ensure system is disabled when audit logs are full   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   Page 1035 Internal Only - General Appendix: CIS Controls v8 IG 1 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.10 Ensure usb-storage kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   Page 1036 Internal Only - General Recommendation Set Correctly Yes No 1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.5 Ensure kernel.dmesg_restrict is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   2.1.1 Ensure autofs services are not in use   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.15 Ensure sshd LogLevel is configured   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   5.1.21 Ensure sshd PermitRootLogin is disabled   5.1.23 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   Page 1037 Internal Only - General Recommendation Set Correctly Yes No 5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   Page 1038 Internal Only - General Recommendation Set Correctly Yes No 5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.8 Ensure logrotate is configured   6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.36 Ensure the audit configuration is immutable   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   Page 1039 Internal Only - General Recommendation Set Correctly Yes No 6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1040 Internal Only - General Appendix: CIS Controls v8 IG 2 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure firewire-core kernel module is not available   1.1.1.10 Ensure usb-storage kernel module is not available   1.1.1.11 Ensure unused filesystems kernel modules are not   available 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 1041 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is   enabled 1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.3 Ensure kernel.yama.ptrace_scope is configured   1.5.5 Ensure kernel.dmesg_restrict is configured   1.5.7 Ensure Automatic Error Reporting is configured   1.5.9 Ensure kernel.randomize_va_space is configured   1.5.10 Ensure kernel.yama.ptrace_scope is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   Page 1042 Internal Only - General Recommendation Set Correctly Yes No 2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure telnet-server services are not in use   2.1.17 Ensure tftp server services are not in use   2.1.18 Ensure web proxy server services are not in use   2.1.19 Ensure web server services are not in use   2.1.20 Ensure xinetd services are not in use   2.1.21 Ensure X window server services are not in use   2.1.22 Ensure mail transfer agents are configured for local-only   mode 2.1.23 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.2 Ensure wireless interfaces are not available   3.1.3 Ensure bluetooth services are not in use   Page 1043 Internal Only - General Recommendation Set Correctly Yes No 3.2.1 Ensure atm kernel module is not available   3.2.2 Ensure can kernel module is not available   3.2.3 Ensure dccp kernel module is not available   3.2.4 Ensure rds kernel module is not available   3.2.5 Ensure sctp kernel module is not available   3.2.6 Ensure tipc kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   Page 1044 Internal Only - General Recommendation Set Correctly Yes No 4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.13 Ensure sshd post-quantum cryptography key exchange   algorithms are configured 5.1.15 Ensure sshd LogLevel is configured   5.1.16 Ensure sshd MACs are configured   5.1.17 Ensure sshd MaxAuthTries is configured   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   5.1.21 Ensure sshd PermitRootLogin is disabled   5.1.23 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account Page 1045 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   Page 1046 Internal Only - General Recommendation Set Correctly Yes No 6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.2.10 Ensure rsyslog forwarding uses gtls   6.1.2.11 Ensure rsyslog CA certificates are configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure modification of the /etc/sudoers file is collected   6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify sethostname and   setdomainname are collected 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net   are collected 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname   are collected 6.2.3.8 Ensure events that modify the system's network   environment are collected Page 1047 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.9 Ensure events that modify /etc/NetworkManager   directory are collected 6.2.3.10 Ensure use of privileged commands are collected   6.2.3.11 Ensure unsuccessful file access attempts are collected   6.2.3.12 Ensure events that modify /etc/group information are   collected 6.2.3.13 Ensure events that modify /etc/passwd information are   collected 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow   are collected 6.2.3.15 Ensure events that modify /etc/security/opasswd are   collected 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are   collected 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/   information are collected 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2   are collected 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are   collected 6.2.3.20 Ensure discretionary access control permission modification events   setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremo vexattr collected 6.2.3.21 Ensure successful file system mounts are collected   6.2.3.22 Ensure session initiation information is collected   6.2.3.23 Ensure login and logout events are collected   6.2.3.24 Ensure unlink file deletion events by users are collected   6.2.3.25 Ensure rename file deletion events by users are collected   6.2.3.26 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected Page 1048 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.31 Ensure kernel module loading unloading and modification   is collected 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors 6.2.3.36 Ensure the audit configuration is immutable   6.2.3.37 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   Page 1049 Internal Only - General Recommendation Set Correctly Yes No 7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1050 Internal Only - General Appendix: CIS Controls v8 IG 3 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure firewire-core kernel module is not available   1.1.1.10 Ensure usb-storage kernel module is not available   1.1.1.11 Ensure unused filesystems kernel modules are not   available 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 1051 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure the source.list and .source files use the Signed-   By option 1.2.1.6 Ensure access to files in the /etc/apt/auth.conf.d/   directory is configured 1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are enforcing   1.3.1.4 Ensure apparmor_restrict_unprivileged_unconfined is   enabled 1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.3 Ensure kernel.yama.ptrace_scope is configured   1.5.5 Ensure kernel.dmesg_restrict is configured   1.5.6 Ensure prelink is not installed   1.5.7 Ensure Automatic Error Reporting is configured   1.5.9 Ensure kernel.randomize_va_space is configured   1.5.10 Ensure kernel.yama.ptrace_scope is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   Page 1052 Internal Only - General Recommendation Set Correctly Yes No 2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure telnet-server services are not in use   2.1.17 Ensure tftp server services are not in use   2.1.18 Ensure web proxy server services are not in use   2.1.19 Ensure web server services are not in use   2.1.20 Ensure xinetd services are not in use   2.1.21 Ensure X window server services are not in use   2.1.22 Ensure mail transfer agents are configured for local-only   mode 2.1.23 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.2 Ensure wireless interfaces are not available   Page 1053 Internal Only - General Recommendation Set Correctly Yes No 3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure atm kernel module is not available   3.2.2 Ensure can kernel module is not available   3.2.3 Ensure dccp kernel module is not available   3.2.4 Ensure rds kernel module is not available   3.2.5 Ensure sctp kernel module is not available   3.2.6 Ensure tipc kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   Page 1054 Internal Only - General Recommendation Set Correctly Yes No 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.13 Ensure sshd post-quantum cryptography key exchange   algorithms are configured 5.1.15 Ensure sshd LogLevel is configured   5.1.16 Ensure sshd MACs are configured   5.1.17 Ensure sshd MaxAuthTries is configured   5.1.20 Ensure sshd PermitEmptyPasswords is disabled   5.1.21 Ensure sshd PermitRootLogin is disabled   5.1.23 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   Page 1055 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   Page 1056 Internal Only - General Recommendation Set Correctly Yes No 6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.2.9 Ensure rsyslog-gnutls is installed   6.1.2.10 Ensure rsyslog forwarding uses gtls   6.1.2.11 Ensure rsyslog CA certificates are configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure modification of the /etc/sudoers file is collected   6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify sethostname and   setdomainname are collected 6.2.3.6 Ensure events that modify /etc/issue and /etc/issue.net   are collected 6.2.3.7 Ensure events that modify /etc/hosts and /etc/hostname   are collected Page 1057 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.8 Ensure events that modify the system's network   environment are collected 6.2.3.9 Ensure events that modify /etc/NetworkManager   directory are collected 6.2.3.10 Ensure use of privileged commands are collected   6.2.3.11 Ensure unsuccessful file access attempts are collected   6.2.3.12 Ensure events that modify /etc/group information are   collected 6.2.3.13 Ensure events that modify /etc/passwd information are   collected 6.2.3.14 Ensure events that modify /etc/shadow and /etc/gshadow   are collected 6.2.3.15 Ensure events that modify /etc/security/opasswd are   collected 6.2.3.16 Ensure events that modify /etc/nsswitch.conf file are   collected 6.2.3.17 Ensure events that modify /etc/pam.conf and /etc/pam.d/   information are collected 6.2.3.18 Ensure discretionary access control permission modification events chmod,fchmod,fchmodat,fchmodat2   are collected 6.2.3.19 Ensure discretionary access control permission modification events chown,fchown,lchown,fchownat are   collected 6.2.3.20 Ensure discretionary access control permission modification events   setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremo vexattr collected 6.2.3.21 Ensure successful file system mounts are collected   6.2.3.22 Ensure session initiation information is collected   6.2.3.23 Ensure login and logout events are collected   6.2.3.24 Ensure unlink file deletion events by users are collected   6.2.3.25 Ensure rename file deletion events by users are collected   6.2.3.26 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.27 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.28 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.29 Ensure successful and unsuccessful attempts to use the   chacl command are collected Page 1058 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.30 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.31 Ensure kernel module loading unloading and modification   is collected 6.2.3.32 Ensure kernel "init_module" and "finit_module" loading   unloading and modification is collected 6.2.3.33 Ensure kernel "delete_module" loading unloading and   modification is collected 6.2.3.34 Ensure kernel query_module loading unloading and   modification is collected 6.2.3.35 Ensure the audit configuration is loaded regardless of   errors 6.2.3.36 Ensure the audit configuration is immutable   6.2.3.37 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   6.3.1 Ensure AIDE is installed   6.3.2 Ensure filesystem integrity is regularly checked   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   Page 1059 Internal Only - General Recommendation Set Correctly Yes No 7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 1060 Internal Only - General Appendix: CIS Controls v8 Unmapped Recommendations Recommendation Set Correctly Yes No 1.2.1.2 Ensure weak dependencies are configured   1.2.1.3 Ensure access to gpg key files are configured   1.2.1.4 Ensure access to /etc/apt/trusted.gpg.d directory is   configured 1.2.1.5 Ensure access to /etc/apt/auth.conf.d directory is   configured 1.2.1.7 Ensure access to /usr/share/keyrings directory is   configured 1.2.1.8 Ensure access to /etc/apt/sources.list.d directory is   configured 1.2.1.9 Ensure access to files in /etc/apt/sources.list.d are   configured 1.5.8 Ensure kernel.kptr_restrict is configured   1.7.2 Ensure GDM login banner is configured   1.7.3 Ensure GDM disable-user-list option is enabled   1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden 2.4.1.7 Ensure access to /etc/cron.yearly is configured   Page 1061 Internal Only - General Appendix: Change History Date Version Changes for this version Page 1062 Internal Only - General