linux-cron-permissions-check: Cron Access File Ownership & Permissions

id: linux-cron-permissions-check

info:
  name: Cron Access File Ownership & Permissions
  author: songyaeji
  severity: high
  description: |
    /etc/cron.allow and /etc/cron.deny (if present) were required to be owned by root (UID 0) with strict 640 permissions.If neither file existed, only the root user could use cron, which was considered the safe default behavior.
  reference:
    - https://isms.kisa.or.kr
  tags: local,linux,audit,kisa,compliance

self-contained: true

code:
  - engine:
      - bash
    source: |
      result=""

      check_file() {
        file=$1
        if [ -f "$file" ]; then
          owner=$(stat -c "%u" "$file")   # numeric UID
          perm=$(stat -c "%a" "$file")   # permissions
          if [ "$owner" -ne 0 ] || [ "$perm" -ne 640 ]; then
            result+="[WARN] $file misconfigured\n"
          fi
        fi
      }

      check_file /etc/cron.allow
      check_file /etc/cron.deny

      if [ -n "$result" ]; then
        echo -e "$result"
      else
        if [ ! -f /etc/cron.allow ] && [ ! -f /etc/cron.deny ]; then
          echo "[OK] no cron access files found (default safe behavior)"
        else
          echo "[OK] cron files properly configured"
        fi
      fi

    matchers:
      - type: word
        part: response
        words:
          - "[WARN] /etc/cron.allow misconfigured"
          - "[WARN] /etc/cron.deny misconfigured"
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