Configure auditing of unsuccessful permission changes

An XCCDF Rule

Description

Ensure that unsuccessful attempts to change file or directory permissions are audited. The following rules configure audit as described above:

## Unsuccessful permission change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change

Load new Audit rules into kernel by running:

augenrules --load

Note: This rule uses a special set of Audit rules to comply with OSPP 4.2.1. You may reuse this rule in different profiles. If you decide to do so, it is recommended that you inspect contents of the file closely and make sure that they are alligned with your needs.

Rationale

Unsuccessful attempts to change permissions of files or directories might be signs of malicious activity. Having such events audited helps in monitoring and investigation of such activities.

ID: xccdf_org.ssgproject.content_rule_audit_perm_change_failed
Severity: Medium
References: AU-2(a)

FAU_GEN.1.1.c

SRG-OS-000064-GPOS-00033 SRG-OS-000462-GPOS-00206 SRG-OS-000463-GPOS-00207 SRG-OS-000465-GPOS-00209 SRG-OS-000466-GPOS-00210 SRG-OS-000474-GPOS-00219 SRG-OS-000475-GPOS-00220
Updated: about 1 year ago

- name: Put contents into /etc/audit/rules.d/30-ospp-v42-5-perm-change-failed.rules
    according to policy
  copy:
    dest: /etc/audit/rules.d/30-ospp-v42-5-perm-change-failed.rules
    content: |
      ## Unsuccessful permission change      -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
      -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
      -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
      -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
    force: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AU-2(a)
  - audit_perm_change_failed
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

- name: Remove any permissions from other group
  file:
    path: /etc/audit/rules.d/30-ospp-v42-5-perm-change-failed.rules
    mode: o-rwx
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AU-2(a)
  - audit_perm_change_failed
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

cat << 'EOF' > /etc/audit/rules.d/30-ospp-v42-5-perm-change-failed.rules
## Unsuccessful permission change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EACCES -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b32 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F exit=-EPERM -F auid>=1000 -F auid!=unset -F key=unsuccessful-perm-change
EOF

chmod o-rwx /etc/audit/rules.d/30-ospp-v42-5-perm-change-failed.rules

augenrules --load

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

Configure auditing of unsuccessful permission changes

Description

Rationale

Remediation - Ansible

Remediation - Shell Script