Restrict Access to Kernel Message Buffer

An XCCDF Rule

Description

To set the runtime status of the kernel.dmesg_restrict kernel parameter, run the following command:

$ sudo sysctl -w kernel.dmesg_restrict=1

To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:

kernel.dmesg_restrict = 1

Rationale

Unprivileged access to the kernel syslog can expose sensitive kernel address information.

ID: xccdf_org.ssgproject.content_rule_sysctl_kernel_dmesg_restrict
Severity: Low
References: 3.1.5

CCI-001090 CCI-001314

164.308(a)(1)(ii)(D) 164.308(a)(3) 164.308(a)(4) 164.310(b) 164.310(c) 164.312(a) 164.312(e)

SI-11(a) SI-11(b)

SRG-OS-000132-GPOS-00067 SRG-OS-000138-GPOS-00069

SRG-APP-000243-CTR-000600

R9
Updated: 5 days ago

- name: List /etc/sysctl.d/*.conf files
  find:
    paths:
    - /etc/sysctl.d/
    - /run/sysctl.d/
    - /usr/local/lib/sysctl.d/    - /usr/lib/sysctl.d/
    contains: ^[\s]*kernel.dmesg_restrict.*$
    patterns: '*.conf'
    file_type: any
  register: find_sysctl_d
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.5
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - disable_strategy
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required
  - sysctl_kernel_dmesg_restrict

- name: Comment out any occurrences of kernel.dmesg_restrict from config files
  replace:
    path: '{{ item.path }}'
    regexp: ^[\s]*kernel.dmesg_restrict
    replace: '#kernel.dmesg_restrict'
  loop: '{{ find_sysctl_d.files }}'
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.5
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - disable_strategy
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required
  - sysctl_kernel_dmesg_restrict

- name: Ensure sysctl kernel.dmesg_restrict is set to 1
  sysctl:
    name: kernel.dmesg_restrict
    value: '1'
    sysctl_file: /etc/sysctl.conf
    state: present
    reload: true
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.5
  - NIST-800-53-SI-11(a)
  - NIST-800-53-SI-11(b)
  - disable_strategy
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required
  - sysctl_kernel_dmesg_restrict

Restrict Access to Kernel Message Buffer

Description

Rationale

Remediation - Ansible