Verify /boot/grub2/user.cfg User Ownership

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Description

The file /boot/grub2/user.cfg should be owned by the root user to prevent reading or modification of the file.

To properly set the owner of /boot/grub2/user.cfg, run the command:

$ sudo chown root /boot/grub2/user.cfg

Rationale

Only root should be able to modify important boot parameters. Also, non-root users who read the boot parameters may be able to identify weaknesses in security upon boot and be able to exploit them.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

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

chown 0 /boot/grub2/user.cfg

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

Ansible playbook

The following playbook can be run with Ansible to remediate the issue.

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - CCE-86014-8
  - CJIS-5.5.2.2
  - NIST-800-171-3.4.5
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-7.1
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_user_cfg
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Test for existence /boot/grub2/user.cfg
  stat:
    path: /boot/grub2/user.cfg
  register: file_exists
  when:
  - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CCE-86014-8
  - CJIS-5.5.2.2
  - NIST-800-171-3.4.5
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-7.1
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_user_cfg
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner 0 on /boot/grub2/user.cfg
  file:
    path: /boot/grub2/user.cfg
    owner: '0'
  when:
  - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
  - '"grub2-common" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - file_exists.stat is defined and file_exists.stat.exists
  tags:
  - CCE-86014-8
  - CJIS-5.5.2.2
  - NIST-800-171-3.4.5
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-7.1
  - PCI-DSSv4-2.2.6
  - configure_strategy
  - file_owner_user_cfg
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed