# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-DESK-011
title: Remove the Ctrl-Alt-Del shortcut from GNOME
finding:
  title: Ctrl-Alt-Del in GNOME opens the power-off and restart dialog
  description: A key sequence pressed out of habit, or by someone at the console, leads to a restart or power-off of the machine in two clicks.
status: active
profiles: [desktop-hardened]
risk:
  severity: low
assessment: automated
tags: [gnome, dconf, availability]

applicability:
  facts: [desktop-gnome]

description: |
  `org.gnome.settings-daemon.plugins.media-keys logout` binds Ctrl-Alt-Del to the log out
  dialog, which also offers restart and power off. Setting it to `['']` removes the binding;
  the key is set in the system dconf database `local` and locked.
rationale: |
  Ctrl-Alt-Del is pressed by reflex on machines used alongside Windows, and on a shared
  console it gives anyone a quick path to restarting the machine. Removing the shortcut
  avoids accidental or opportunistic restarts of the workstation.
impact: |
  Users log out or power off from the system menu. Ctrl-Alt-Del does nothing in GNOME.
notes: |
  This only concerns the GNOME shortcut. Ctrl-Alt-Del on a text console is handled by systemd
  (`ctrl-alt-del.target`).

setting:
  location: /etc/dconf/db/local.d/, key /org/gnome/settings-daemon/plugins/media-keys/logout
  default_value: "['<Control><Alt>Delete']"
  recommended_value: "[''], locked"

audit:
  manual: |
    1. `dconf read /org/gnome/settings-daemon/plugins/media-keys/logout` must print `['']`.
    2. The key must be listed in a file of `/etc/dconf/db/local.d/locks/`.
  checks:
    - id: logout-key
      engine: dconf
      description: No GNOME shortcut opens the log out dialog.
      facts: [desktop-gnome]
      spec:
        key: /org/gnome/settings-daemon/plugins/media-keys/logout
        value: "['']"

remediation:
  manual: |
    1. Make sure `/etc/dconf/profile/user` contains `user-db:user` and `system-db:local`.
    2. Create `/etc/dconf/db/local.d/00-ctrl-alt-del`:
       ```
       [org/gnome/settings-daemon/plugins/media-keys]
       logout=['']
       ```
    3. List `/org/gnome/settings-daemon/plugins/media-keys/logout` in
       `/etc/dconf/db/local.d/locks/00-ctrl-alt-del` and run `dconf update`.
  effects:
    restart: session
    disruption: none
    lockout_risk: false
  rollback: |
    Delete the files written in `/etc/dconf/db/local.d/` and its `locks/` directory, then run
    `dconf update`.
  scripts:
    - id: logout-key
      from_check: logout-key

references:
  - title: gnome-settings-daemon - media-keys schema
    url: https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/blob/master/data/org.gnome.settings-daemon.plugins.media-keys.gschema.xml.in
    publisher: The GNOME Project
    kind: vendor-doc
    accessed: 2026-10-19
  - title: GNOME System Administration Guide - Lock down specific settings
    url: https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en
    publisher: The GNOME Project
    kind: vendor-doc
    accessed: 2026-10-19
mappings:
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: CM-6
    relation: related
threats:
  - framework: mitre-attack
    id: T1529

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["20.04"]
    environment: Proxmox VM with Ubuntu Desktop (GNOME 3.36, gdm3), Ubuntu 20.04.6, kernel 5.4.0-216-generic
    notes: "Generated dconf check and fix (desktop-hardened); value and lock confirmed with gsettings get/writable as a user under dbus-run-session (write refused); second remediation reported compliant; state kept after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["22.04"]
    environment: Proxmox VM with Ubuntu Desktop (GNOME 42, gdm3), Ubuntu 22.04.5, kernel 5.15.0-198-generic
    notes: "Generated dconf check and fix (desktop-hardened); value and lock confirmed with gsettings get/writable as a user under dbus-run-session (write refused); second remediation reported compliant; state kept after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["24.04"]
    environment: Proxmox VM with Ubuntu Desktop (GNOME 46, gdm3), Ubuntu 24.04.5, kernel 6.8.0-147-generic
    notes: "Generated dconf check and fix (desktop-hardened); value and lock confirmed with gsettings get/writable as a user under dbus-run-session (write refused); second remediation reported compliant; state kept after reboot."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["26.04"]
    environment: Proxmox VM with Ubuntu Desktop (GNOME 50, gdm3), Ubuntu 26.04.1, kernel 7.0.0-38-generic
    notes: "Generated dconf check and fix (desktop-hardened); value and lock confirmed with gsettings get/writable as a user under dbus-run-session (write refused); second remediation reported compliant; state kept after reboot."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19