# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-BOOT-008
title: Install and enable AppArmor
finding:
  title: AppArmor mandatory access control is not active
  description: Without a mandatory access control system, a compromised service keeps every right of its Unix user.
status: active
profiles: [core]
risk:
  severity: medium
assessment: automated
tags: [apparmor, mac, lsm]

description: |
  AppArmor is the mandatory access control (MAC) system of Ubuntu. It confines programs with
  per-program profiles that list the files, capabilities and network access they may use, on top
  of the classic Unix permissions. It needs the `apparmor` package (parser and profiles) and the
  AppArmor security module enabled in the running kernel.
rationale: |
  Unix permissions only depend on the user a program runs as. A compromised service confined by
  an AppArmor profile cannot read or write outside what its profile allows, even as root, which
  limits what an attacker can do after exploiting it.
impact: |
  None known on a default install: Ubuntu ships AppArmor installed and enabled on every
  release, and its profiles are written not to break the packaged programs.
notes: |
  AppArmor is the default security module of the Ubuntu kernels, so no `apparmor=1` or
  `security=apparmor` boot parameter is needed. If it was disabled with `apparmor=0` or a
  `security=` / `lsm=` kernel parameter, remove that parameter from `GRUB_CMDLINE_LINUX` in
  `/etc/default/grub`, run `update-grub` and reboot.

setting:
  location: Package `apparmor`; kernel security modules (`/sys/kernel/security/lsm`)
  default_value: Installed and enabled
  recommended_value: Installed and enabled

audit:
  manual: |
    1. Run `dpkg -s apparmor`. The package must be installed.
    2. Run `aa-enabled`. It must print `Yes`.
  checks:
    - id: package
      engine: package
      description: The apparmor package is installed.
      spec: { name: apparmor, state: installed }
    - id: enabled
      engine: file-content
      description: The AppArmor kernel module reports itself enabled.
      spec: { path: /sys/module/apparmor/parameters/enabled, pattern: "^Y$" }

remediation:
  manual: |
    1. Install the package: `apt install apparmor`.
    2. If `aa-enabled` still says it is disabled, remove `apparmor=0`, `security=` or `lsm=`
       from the kernel command line in `/etc/default/grub`, run `update-grub` and reboot.
  effects:
    restart: none
    disruption: low
    lockout_risk: false
  rollback: |
    AppArmor can be disabled for one boot with the `apparmor=0` kernel parameter.
  scripts:
    - id: install
      from_check: package

references:
  - title: Ubuntu Server documentation - AppArmor
    url: https://documentation.ubuntu.com/server/how-to/security/apparmor/
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: aa-status(8), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man8/aa-status.8.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R45)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-19
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: R45
    relation: partial
    note: R45 also asks to put every profile in enforce mode, which is CB-UBU-BOOT-010.
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: AC-3
    relation: related
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "1.3.1.1"
    relation: partial
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "1.3.1.2"
    relation: partial
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "1.3.1.1"
    relation: partial
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "1.3.1.2"
    relation: partial
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "1.3.1.1"
    relation: partial
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "1.3.1.2"
    relation: partial
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "1.3.1.1"
    relation: partial
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "1.3.1.2"
    relation: partial
threats:
  - framework: mitre-attack
    id: T1068
related_controls:
  - id: CB-UBU-BOOT-010
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["20.04"]
    environment: Proxmox VM, Ubuntu 20.04 cloud image, kernel 5.4.0-216-generic, BIOS boot
    notes: "Check passes on a fresh install; still passes after remediation and reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["22.04"]
    environment: Proxmox VM, Ubuntu 22.04 cloud image, kernel 5.15.0-198-generic, BIOS boot
    notes: "Check passes on a fresh install; still passes after remediation and reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["24.04"]
    environment: Proxmox VM, Ubuntu 24.04 cloud image, kernel 6.8.0-147-generic, BIOS boot
    notes: "Check passes on a fresh install; still passes after remediation and reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["26.04"]
    environment: Proxmox VM, Ubuntu 26.04 cloud image, kernel 7.0.0-38-generic, BIOS boot
    notes: "Check passes on a fresh install; still passes after remediation and reboot."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19