# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-UBU-AUTH-007
title: Never disable authentication for sudo globally
finding:
  title: sudo is configured to skip authentication
  description: With authentication disabled, every sudo rule works without a password, for every user it applies to.
status: active
profiles: [core]
risk:
  severity: high
assessment: automated
tags: [sudo, privilege-escalation]

applicability:
  facts: [sudo]

description: |
  The `!authenticate` default turns off password checks for every rule it applies to. Unlike a
  `NOPASSWD:` tag on one rule, it is easy to miss because it sits in a `Defaults` line.
rationale: |
  A global `!authenticate` silently turns every administrator account into a password-less root
  account: stealing any of their sessions is enough to control the system.
impact: |
  None for a standard configuration. Ubuntu does not set it.
notes: |
  sudo-rs, the `sudo` of Ubuntu 26.04, does not know the `authenticate` setting: its `visudo`
  rejects the line. The check still applies, since the original sudo stays installed and can be
  selected again through the `sudo` alternative.

audit:
  manual: |
    Run `grep -r '!authenticate' /etc/sudoers /etc/sudoers.d/`. There must be no match.
  checks:
    - id: sudoers
      engine: file-content
      description: No !authenticate in /etc/sudoers.
      spec: { path: /etc/sudoers, pattern: "^[^#]*!\\s*authenticate", expect: no_match }
    - id: sudoers-d
      engine: file-content
      description: No !authenticate in /etc/sudoers.d/.
      spec: { path: /etc/sudoers.d/*, pattern: "^[^#]*!\\s*authenticate", expect: no_match }

remediation:
  manual: |
    Remove every `Defaults ... !authenticate` entry with `visudo` (or `visudo -f` for files in
    `/etc/sudoers.d/`).
  rollback: |
    Add the entry back with `visudo`.

references:
  - title: sudoers(5), Ubuntu manual pages
    url: https://manpages.ubuntu.com/manpages/noble/man5/sudoers.5.html
    publisher: Canonical
    kind: vendor-doc
    accessed: 2026-10-19
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R39)
    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: R39
    relation: partial
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: IA-11
    relation: related
  - framework: cis-ubuntu-2004
    framework_version: "3.0.0"
    id: "5.2.5"
    relation: equivalent
  - framework: cis-ubuntu-2204
    framework_version: "3.0.0"
    id: "5.2.5"
    relation: equivalent
  - framework: cis-ubuntu-2404
    framework_version: "2.0.0"
    id: "5.2.5"
    relation: equivalent
  - framework: cis-ubuntu-2604
    framework_version: "1.0.0"
    id: "5.2.5"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1548.003

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
    notes: "Passes on a fresh install; profiles core and server-hardened."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["22.04"]
    environment: Proxmox VM, Ubuntu 22.04 cloud image, kernel 5.15.0-198-generic
    notes: "Passes on a fresh install; profiles core and server-hardened."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["24.04"]
    environment: Proxmox VM, Ubuntu 24.04 cloud image, kernel 6.8.0-147-generic
    notes: "Passes on a fresh install; profiles core and server-hardened."
  - date: 2026-10-19
    by: Sn0wAlice
    versions: ["26.04"]
    environment: Proxmox VM, Ubuntu 26.04 cloud image, kernel 7.0.0-38-generic
    notes: "Passes on a fresh install; profiles core and server-hardened."
introduced_in: 0.1.0
created: 2026-10-19
updated: 2026-10-19