# yaml-language-server: $schema=../../../../schema/control.schema.json
id: CB-DEB-AUDIT-026
title: Audit every use of setuid and setgid programs
finding:
  title: Use of privileged programs is not recorded
  description: Programs that run with more rights than their caller are the main path to privilege escalation and are used without a record.
status: active
profiles: [server-hardened, desktop-hardened]
risk:
  severity: medium
assessment: automated
tags: [auditd, setuid]

description: |
  One auditd rule per setuid or setgid program found on the local file systems that allow
  them (not mounted `nosuid` or `noexec`), key `privileged`, in
  `/etc/audit/rules.d/60-cirsec-privileged.rules`. Each rule records every run of the program by a
  user who logged in. The list is rebuilt from the file system each time the check or the fix runs.
rationale: |
  `passwd`, `su`, `sudo`, `mount`, `chsh` and similar programs run as root on behalf of a user.
  Recording each use shows who used them and is the first place to look after a privilege escalation.
impact: |
  Installing or removing a package that ships a setuid program makes the check fail until the fix
  runs again. Once the audit configuration is locked (CB-DEB-AUDIT-029), the new rule only loads at
  the next reboot.
notes: |
  The scan covers local file systems listed by `findmnt --real`. Programs on network file systems are not covered.

setting:
  location: /etc/audit/rules.d/60-cirsec-privileged.rules
  default_value: No audit rules
  recommended_value: "Rules loaded (auditctl -l) and present in /etc/audit/rules.d/60-cirsec-privileged.rules"

audit:
  manual: |
    1. Run `auditctl -l` as root. It must list the rules shown below (keys `privileged`).
    2. Run `grep -h . /etc/audit/rules.d/*.rules`. The same rules must be present, so they load at boot.

    Expected rules, as `auditctl -l` prints them:
    ```
    -a always,exit -S all -F path=<program> -F perm=x -F auid>=1000 -F auid!=-1 -F key=privileged
    ```
  checks:
    - id: rules
      engine: shell
      description: Rules loaded in the kernel and present in /etc/audit/rules.d.
      spec:
        script: |
          command -v auditctl >/dev/null 2>&1 || { echo "auditctl not found: auditd is not installed"; exit 1; }
          want() {
          # every setuid or setgid file on local file systems mounted without nosuid or noexec
          for m in $(findmnt -rn --real -O nonosuid,nonoexec -o TARGET); do
            find "$m" -xdev -type f \( -perm -4000 -o -perm -2000 \) 2>/dev/null
          done | sort -u | while IFS= read -r p; do
            echo "-a always,exit -S all -F path=$p -F perm=x -F auid>=1000 -F auid!=-1 -F key=privileged"
          done
          }
          loaded=$(auditctl -l 2>&1) || { echo "$loaded"; exit 3; }
          disk=$(cat /etc/audit/rules.d/*.rules 2>/dev/null)
          n=0 rc=0
          while IFS= read -r r; do
            [ -n "$r" ] || continue
            n=$((n + 1))
            printf '%s\n' "$loaded" | grep -Fxq -- "$r" || { echo "not loaded: $r"; rc=1; }
            printf '%s\n' "$disk" | grep -Fxq -- "$r" || { echo "not in /etc/audit/rules.d: $r"; rc=1; }
          done <<EOF
          $(want)
          EOF
          [ "$rc" = 1 ] || echo "$n rules loaded and present in /etc/audit/rules.d"
          exit "$rc"

remediation:
  manual: |
    1. Write the expected rules to `/etc/audit/rules.d/60-cirsec-privileged.rules` (mode 0640).
    2. Run `augenrules --load`. If `auditctl -s` shows `enabled 2`, the configuration is locked:
       reboot to load the new rules.
  effects:
    restart: none
    disruption: none
    lockout_risk: false
  rollback: |
    Delete `/etc/audit/rules.d/60-cirsec-privileged.rules` and run `augenrules --load` (or reboot if the configuration is locked).
  scripts:
    - id: rules-file
      engine: shell
      content: |
        command -v augenrules >/dev/null 2>&1 || { echo "auditd is not installed" >&2; exit 1; }
        want() {
        # every setuid or setgid file on local file systems mounted without nosuid or noexec
        for m in $(findmnt -rn --real -O nonosuid,nonoexec -o TARGET); do
          find "$m" -xdev -type f \( -perm -4000 -o -perm -2000 \) 2>/dev/null
        done | sort -u | while IFS= read -r p; do
          echo "-a always,exit -S all -F path=$p -F perm=x -F auid>=1000 -F auid!=-1 -F key=privileged"
        done
        }
        f=/etc/audit/rules.d/60-cirsec-privileged.rules
        t=$(mktemp)
        { echo '# Written by CIRSEC Baselines CB-DEB-AUDIT-026'; want; } >"$t"
        if ! cmp -s "$t" "$f"; then
          cb_backup "$f"
          cat "$t" >"$f"
        fi
        rm -f "$t"
        chmod 640 "$f"
        if auditctl -s | grep -q '^enabled 2'; then
          echo "audit rules are locked (-e 2): reboot to load $f"
        else
          augenrules --load >/dev/null
        fi

references:
  - title: audit.rules(7), Debian manual pages
    url: https://manpages.debian.org/trixie/auditd/audit.rules.7.en.html
    publisher: Debian
    kind: vendor-doc
    accessed: 2026-10-18
  - title: auditctl(8), Debian manual pages
    url: https://manpages.debian.org/trixie/auditd/auditctl.8.en.html
    publisher: Debian
    kind: vendor-doc
    accessed: 2026-10-18
  - title: ANSSI-BP-028 v2.0 - Recommandations de configuration d'un système GNU/Linux (R73)
    url: https://messervices.cyber.gouv.fr/documents-guides/fr_np_linux_configuration-v2.0.pdf
    publisher: ANSSI
    kind: guide
    accessed: 2026-10-18
mappings:
  - framework: anssi-linux
    framework_version: "2.0"
    id: "R33"
    relation: partial
  - framework: anssi-linux
    framework_version: "2.0"
    id: "R73"
    relation: partial
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: "AU-12"
    relation: related
  - framework: nist-800-53r5
    framework_version: "5.1.1"
    id: "AC-6(9)"
    relation: related
  - framework: cis-debian-12
    framework_version: "2.0.0"
    id: "6.2.3.10"
    relation: equivalent
  - framework: cis-debian-13
    framework_version: "1.1.0"
    id: "6.2.3.10"
    relation: equivalent
threats:
  - framework: mitre-attack
    id: T1548.001
related_controls:
  - id: CB-DEB-AUDIT-011
    type: requires
  - id: CB-DEB-AUDIT-029
    type: related

authors:
  - name: Alice
    github: Sn0wAlice
verified:
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["12"]
    environment: Proxmox VM, Debian 12 genericcloud image, kernel 6.1.0-54-cloud-amd64, auditd 1:3.0.9-1, BIOS boot
    notes: "Rules fail on fresh install; fix writes /etc/audit/rules.d/60-cirsec-privileged.rules and loads it; rules match auditctl -l, kept after reboot; second run idempotent."
  - date: 2026-10-18
    by: Sn0wAlice
    versions: ["13"]
    environment: Proxmox VM, Debian 13 genericcloud image, kernel 6.12.113+deb13-cloud-amd64, auditd 1:4.0.2-2+deb13u1, BIOS boot
    notes: "Rules fail on fresh install; fix writes /etc/audit/rules.d/60-cirsec-privileged.rules and loads it; rules match auditctl -l, kept after reboot; second run idempotent."
introduced_in: 0.1.0
created: 2026-10-18
updated: 2026-10-18