security-docker

name

security-docker

description

Review Docker and container security audit patterns. Use for auditing secrets in layers, port exposure, and non-root users. Use proactively when Dockerfile or docker-compose.yml is present. Examples: - user: "Audit this Dockerfile" → check for secrets in ENV/ARG and non-root USER - user: "Review docker-compose ports" → find accidentally exposed databases - user: "Check for secrets in image history" → audit layers and build artifacts - user: "Optimize Docker security" → implement multi-stage builds and minimal base images - user: "Audit container privileges" → check for privileged: true or docker.sock mounts

Security audit patterns for Docker and container deployments covering secrets in images, port exposure, user privileges, and compose security.

Secrets in Images (Critical)

Secrets in Build Args/ENV

# ❌ CRITICAL: Secret in ENV (visible in image history)
ENV API_KEY=sk_live_abc123
ENV DATABASE_URL=postgres://user:password@host/db

# ❌ CRITICAL: Secret in ARG (visible in image history)
ARG AWS_SECRET_ACCESS_KEY
RUN aws configure set aws_secret_access_key $AWS_SECRET_ACCESS_KEY

# ✓ Use runtime secrets
# Pass via docker run -e or docker-compose environment/env_file

# ✓ Docker secrets (Swarm) or orchestrator-specific secrets
# Use /run/secrets/* instead of ENV/ARG when available

Secrets Baked into Layers

# ❌ CRITICAL: Even if deleted, secret is in layer history
COPY .env /app/.env
RUN source /app/.env && do_something
RUN rm /app/.env  # Still in previous layer!

# ❌ CRITICAL: Copying all files includes secrets
COPY . /app/  # Copies .env, .git, etc.

# ✓ Use .dockerignore
# In .dockerignore:
# .env*
# .git
# *.pem
# *.key

# ✓ Or explicit COPY
COPY package*.json /app/
COPY src/ /app/src/

Checking Image History

# Audit existing images for secrets
docker history --no-trunc <image>
docker inspect <image> | jq '.[0].Config.Env'