security-docker

# ❌ 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/

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

# ❌ CRITICAL: Database exposed to host network
services:
  db:
    image: postgres
    ports:
      - "5432:5432"  # Accessible from outside!
 
# ❌ CRITICAL: Redis without password
  redis:
    image: redis
    ports:
      - "6379:6379"  # And no AUTH!
 
# ✓ Internal only (accessible to other containers)
services:
  db:
    image: postgres
    expose:
      - "5432"  # Only internal
    # No 'ports' = not exposed to host
 
# ✓ If must expose, bind to localhost
  db:
    ports:
      - "127.0.0.1:5432:5432"  # Only localhost

# ❌ No password or default password
services:
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD: postgres  # Default!
 
  redis:
    image: redis
    # No password at all
 
# ✓ Strong passwords from secrets
services:
  db:
    image: postgres
    environment:
      POSTGRES_PASSWORD_FILE: /run/secrets/db_password
    secrets:
      - db_password
 
secrets:
  db_password:
    file: ./secrets/db_password.txt  # MUST NOT be in git!

# ❌ Running as root (default)
FROM node:18
COPY . /app
CMD ["node", "server.js"]  # Runs as root
 
# ✓ Create and use non-root user
FROM node:18
WORKDIR /app
COPY --chown=node:node . .
USER node
CMD ["node", "server.js"]
 
# ✓ Using numeric UID (more portable)
FROM node:18
RUN useradd -r -u 1001 appuser
WORKDIR /app
COPY --chown=1001:1001 . .
USER 1001
CMD ["node", "server.js"]

# ❌ Build tools and secrets in final image
FROM node:18
COPY . .
RUN npm install
RUN npm run build
CMD ["node", "dist/server.js"]
# Final image has: source, node_modules (dev deps), build tools
 
# ✓ Multi-stage: only production artifacts
FROM node:18 AS builder
WORKDIR /app
COPY package*.json .
RUN npm ci
COPY . .
RUN npm run build
 
FROM node:18-slim AS production
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
USER node
CMD ["node", "dist/server.js"]
# Final image: minimal, no source, no build tools

# ❌ CRITICAL: Full host access
services:
  app:
    privileged: true  # Container can do anything on host!
 
# ❌ HIGH: Dangerous capabilities
services:
  app:
    cap_add:
      - SYS_ADMIN
      - NET_ADMIN

# ❌ CRITICAL: Docker socket access = root on host
services:
  app:
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
 
# ❌ HIGH: Sensitive host paths
services:
  app:
    volumes:
      - /etc:/etc
      - /root:/root

# ❌ HIGH: Host network mode
services:
  app:
    network_mode: host  # Bypasses Docker network isolation

# ❌ Outdated or unverified
FROM node:14  # EOL version
FROM random-user/node-app  # Unverified
 
# ✓ Official, recent, minimal
FROM node:20-slim
FROM node:20-alpine

# Scan for vulnerabilities
docker scout cves <image>
trivy image <image>
grype <image>

# Find secrets in Dockerfile
rg "(ENV|ARG).*(KEY|SECRET|PASSWORD|TOKEN)" Dockerfile*
 
# Find exposed ports in compose
rg "ports:" docker-compose*.yml -A 3
 
# Check for privileged/capabilities
rg "(privileged|cap_add|network_mode)" docker-compose*.yml
 
# Check for docker.sock mount
rg "docker.sock" docker-compose*.yml
 
# Check for USER instruction
grep "^USER" Dockerfile
 
# Check .dockerignore exists and has secrets
cat .dockerignore | grep -E "(env|key|secret|pem)"