Extend Audit Backlog Limit for the Audit Daemon

An XCCDF Rule

Description

To improve the kernel capacity to queue all log events, even those which occurred prior to the audit daemon, add the argument audit_backlog_limit=8192 to the default GRUB 2 command line for the Linux operating system. To ensure that audit_backlog_limit=8192 is added as a kernel command line argument to newly installed kernels, add audit_backlog_limit=8192 to the default Grub2 command line for Linux operating systems. Modify the line within /etc/default/grub as shown below:

GRUB_CMDLINE_LINUX="... audit_backlog_limit=8192 ..."

Run the following command to update command line for already installed kernels:

# grubby --update-kernel=ALL --args="audit_backlog_limit=8192"

Rationale

audit_backlog_limit sets the queue length for audit events awaiting transfer to the audit daemon. Until the audit daemon is up and running, all log messages are stored in this queue. If the queue is overrun during boot process, the action defined by audit failure flag is taken.

ID: xccdf_org.ssgproject.content_rule_grub2_audit_backlog_limit_argument
Severity: Low
References: CCI-000130 CCI-000135 CCI-000169 CCI-000172 CCI-001849 CCI-002884

CM-6(a)

FAU_STG.1 FAU_STG.3

SRG-OS-000037-GPOS-00015 SRG-OS-000042-GPOS-00020 SRG-OS-000062-GPOS-00031 SRG-OS-000254-GPOS-00095 SRG-OS-000341-GPOS-00132 SRG-OS-000392-GPOS-00172 SRG-OS-000462-GPOS-00206 SRG-OS-000471-GPOS-00215

10.7.2
Updated: about 1 year ago

[customizations.kernel]
append = "audit_backlog_limit=8192"

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && { rpm --quiet -q grub2-common; }; then

# Correct the form of default kernel command line in GRUB
if grep -q '^\s*GRUB_CMDLINE_LINUX=.*audit_backlog_limit=.*"'  '/etc/default/grub' ; then
       # modify the GRUB command-line if an audit_backlog_limit= arg already exists       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)audit_backlog_limit=[^[:space:]]\+\(.*\"\)/\1audit_backlog_limit=8192\2/"  '/etc/default/grub'
# Add to already existing GRUB_CMDLINE_LINUX parameters
elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
       # no audit_backlog_limit=arg is present, append it
       sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 audit_backlog_limit=8192\"/"  '/etc/default/grub'
# Add GRUB_CMDLINE_LINUX parameters line
else
       echo "GRUB_CMDLINE_LINUX=\"audit_backlog_limit=8192\"" >> '/etc/default/grub'
fi
grubby --update-kernel=ALL --args=audit_backlog_limit=8192

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

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check audit_backlog_limit argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=.*audit_backlog_limit=' /etc/default/grub
  failed_when: false
  register: argcheck
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Check audit_backlog_limit argument exists
  command: grep '^\s*GRUB_CMDLINE_LINUX=' /etc/default/grub
  failed_when: false
  register: linecheck
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add audit_backlog_limit argument
  ansible.builtin.lineinfile:
    line: GRUB_CMDLINE_LINUX="audit_backlog_limit=8192 "
    state: present
    dest: /etc/default/grub
    create: true
    mode: '0644'
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc != 0
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Replace existing audit_backlog_limit argument
  replace:
    path: /etc/default/grub
    regexp: audit_backlog_limit=[a-zA-Z0-9,]+
    replace: audit_backlog_limit=8192
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc == 0 and
    linecheck.rc == 0
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Add audit_backlog_limit argument
  replace:
    path: /etc/default/grub
    regexp: (^\s*GRUB_CMDLINE_LINUX=.*)"
    replace: \1 audit_backlog_limit=8192"
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  - argcheck is not skipped and linecheck is not skipped and argcheck.rc != 0 and
    linecheck.rc == 0
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

- name: Update grub defaults and the bootloader menu
  command: /sbin/grubby --update-kernel=ALL --args="audit_backlog_limit=8192"
  when:
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - '"grub2-common" in ansible_facts.packages'
  tags:
  - NIST-800-53-CM-6(a)
  - PCI-DSSv4-10.7.2
  - grub2_audit_backlog_limit_argument
  - low_disruption
  - low_severity
  - medium_complexity
  - reboot_required
  - restrict_strategy

Extend Audit Backlog Limit for the Audit Daemon

Description

Rationale

Remediation - OS Build Blueprint

Remediation - Shell Script

Remediation - Ansible