Extend Audit Backlog Limit for the Audit Daemon in zIPL

An XCCDF Rule

Description

To improve the kernel capacity to queue all log events, even those which start prior to the audit daemon, check that all boot entries in /boot/loader/entries/*.conf have audit_backlog_limit=8192 included in its options.
To ensure that new kernels and boot entries continue to extend the audit log events queue, add audit_backlog_limit=8192 to /etc/kernel/cmdline.

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_zipl_audit_backlog_limit_argument
Severity: Medium
References: FAU_STG.1 FAU_STG.3
Updated: about 1 year ago

# Remediation is applicable only in certain platforms
if grep -q s390x /proc/sys/kernel/osrelease && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then

# Correct BLS option using grubby, which is a thin wrapper around BLS operations
grubby --update-kernel=ALL --args="audit_backlog_limit=8192"
# Ensure new kernels and boot entries retain the boot option
if [ ! -f /etc/kernel/cmdline ]; then
    echo "audit_backlog_limit=8192" > /etc/kernel/cmdline
elif ! grep -q '^(.*\s)?audit_backlog_limit=8192(\s.*)?$' /etc/kernel/cmdline; then
    
    sed -Ei 's/^(.*)$/\1 audit_backlog_limit=8192/' /etc/kernel/cmdline
fi

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

- name: Ensure BLS boot entries options contain audit_backlog_limit=8192
  block:

  - name: 'Check how many boot entries exist '
    find:
      paths: /boot/loader/entries/      patterns: '*.conf'
    register: n_entries

  - name: Check how many boot entries set audit_backlog_limit=8192
    find:
      paths: /boot/loader/entries/
      contains: ^options .*audit_backlog_limit=8192.*$
      patterns: '*.conf'
    register: n_entries_options

  - name: Update boot entries options
    command: grubby --update-kernel=ALL --args="audit_backlog_limit=8192"
    when: n_entries is defined and n_entries_options is defined and n_entries.matched
      != n_entries_options.matched

  - name: Check if /etc/kernel/cmdline exists
    stat:
      path: /etc/kernel/cmdline
    register: cmdline_stat

  - name: Check if /etc/kernel/cmdline contains audit_backlog_limit=8192
    find:
      paths: /etc/kernel/
      patterns: cmdline
      contains: ^.*audit_backlog_limit=8192.*$
    register: cmdline_find

  - name: Add /etc/kernel/cmdline contains audit_backlog_limit=8192
    lineinfile:
      create: true
      path: /etc/kernel/cmdline
      line: audit_backlog_limit=8192
    when: cmdline_stat is defined and not cmdline_stat.stat.exists

  - name: Append /etc/kernel/cmdline contains audit_backlog_limit=8192
    lineinfile:
      path: /etc/kernel/cmdline
      backrefs: true
      regexp: ^(.*)$
      line: \1 audit_backlog_limit=8192
    when: cmdline_stat is defined and cmdline_stat.stat.exists and cmdline_find is
      defined and cmdline_find.matched == 0
  when:
  - ansible_architecture == "s390x"
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - configure_strategy
  - low_disruption
  - medium_complexity
  - medium_severity
  - reboot_required
  - zipl_audit_backlog_limit_argument

Extend Audit Backlog Limit for the Audit Daemon in zIPL

Description

Rationale

Remediation - Shell Script

Remediation - Ansible