Performing Docker Bench Security Assessment

Performing Docker Bench Security Assessment

Overview

Docker Bench for Security is an open-source script that checks dozens of common best practices around deploying Docker containers in production. Based on the CIS Docker Benchmark, it audits host configuration, Docker daemon settings, container images, runtime configurations, and security operations to generate a compliance report with pass/fail/warn results.

When to Use

• When conducting security assessments that involve performing docker bench security assessment
• When following incident response procedures for related security events
• When performing scheduled security testing or auditing activities
• When validating security controls through hands-on testing

Coverage Gaps & Validation

Docker Bench reports on the host and daemon it can reach - which is rarely the whole picture:

• Host-scoped, not cluster-scoped: the script audits one Docker host's daemon, config, and running containers. It does not assess Kubernetes, containerd-only nodes, or other hosts in the fleet; a PASS here says nothing about the rest of the estate.
• Mounts gate the checks: the container run needs --net host --pid host --userns host and read-only mounts of /etc, /var/lib, /usr/lib/systemd, and docker.sock. Miss one and the affected checks silently [INFO]/skip rather than fail - looking like success.
• WARN is not PASS: many image/runtime items (5.x) emit [WARN] requiring manual judgement (e.g. per-container --cap-drop, --read-only, no-new-privileges); counting only [FAIL] understates exposure.
• Point-in-time, running containers only: checks evaluate currently-running containers; an insecure image not running at scan time is invisible.

Validate: confirm the scan actually inspected the daemon by checking total check count and that section 2 (daemon) and 5 (runtime) ran, not just section 1. Re-run after remediating /etc/docker/daemon.json (icc, no-new-privileges) and systemctl restart docker, since the script reads live daemon state. Treat WARN items as manual to-dos and pair Docker Bench with an image scanner (Trivy/Grype) for the vulnerabilities it does not cover.

Prerequisites

• Docker Engine installed and running
• Root or sudo access on Docker host
• Docker Bench Security script or container image

Workflow

Step 1: Run Docker Bench Security

# Run as a container (recommended)
docker run --rm --net host --pid host --userns host --cap-add audit_control \
  -e DOCKER_CONTENT_TRUST=$DOCKER_CONTENT_TRUST \
  -v /etc:/etc:ro \
  -v /usr/bin/containerd:/usr/bin/containerd:ro \
  -v /usr/bin/runc:/usr/bin/runc:ro \
  -v /usr/lib/systemd:/usr/lib/systemd:ro \
  -v /var/lib:/var/lib:ro \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  --label docker_bench_security \
  docker/docker-bench-security

# Run with JSON output
docker run --rm --net host --pid host --userns host --cap-add audit_control \
  -v /etc:/etc:ro \
  -v /var/lib:/var/lib:ro \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  docker/docker-bench-security -l /dev/stdout 2>/dev/null | tee docker-bench-results.json

# Run specific sections only
docker run --rm --net host --pid host --userns host \
  -v /var/run/docker.sock:/var/run/docker.sock:ro \
  docker/docker-bench-security -c container_images,container_runtime

Step 2: Interpret Results

[INFO] 1 - Host Configuration
[PASS] 1.1.1 - Ensure a separate partition for containers has been created
[WARN] 1.1.2 - Ensure only trusted users are allowed to control Docker daemon
[PASS] 1.1.3 - Ensure auditing is configured for the Docker daemon

[INFO] 2 - Docker daemon configuration
[FAIL] 2.1 - Run the Docker daemon as a non-root user
[PASS] 2.2 - Ensure network traffic is restricted between containers on the default bridge

Step 3: Remediate Common Failures

# Fix 2.2: Restrict inter-container communication
echo '{"icc": false}' | sudo tee /etc/docker/daemon.json

# Fix 2.17: Restrict containers from acquiring new privileges
echo '{"no-new-privileges": true}' | sudo tee -a /etc/docker/daemon.json

# Fix 5.3: Restrict Linux kernel capabilities
# Use --cap-drop ALL in docker run commands

# Fix 5.12: Mount container's root filesystem as read only
# Use --read-only flag in docker run commands

# Restart Docker daemon after configuration changes
sudo systemctl restart docker

Step 4: Automate Scheduled Assessments

# docker-compose for scheduled assessment
version: '3.8'
services:
  bench-security:
    image: docker/docker-bench-security
    network_mode: host
    pid: host
    userns_mode: host
    cap_add:
      - audit_control
    volumes:
      - /etc:/etc:ro
      - /var/lib:/var/lib:ro
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - ./results:/results
    command: -l /results/bench-$(date +%Y%m%d).log
    deploy:
      restart_policy:
        condition: none

Validation Commands

# Verify remediation
docker run --rm docker/docker-bench-security 2>&1 | grep -E "(PASS|FAIL|WARN)" | sort | uniq -c

# Count results by type
docker run --rm docker/docker-bench-security 2>&1 | grep -c "PASS"
docker run --rm docker/docker-bench-security 2>&1 | grep -c "FAIL"
docker run --rm docker/docker-bench-security 2>&1 | grep -c "WARN"

References

• Docker Bench Security
• CIS Docker Benchmark
• Docker Security Best Practices