docker-security

# Docker Security — 安全加固与防护 Comprehensive guidance for securing Docker across the full lifecycle. ## When to Use **ALWAYS use this skill when the user mentions:** - "docker 安全", "镜像安全", "container security" - "非root运行", "rootless", "least privilege" - "seccomp", "AppArmor", "SELinux" - "Docker Bench", "CIS" - "secrets management", "密钥管理" - "image signing", "content trust" ## Security Model — Layered Defense ``` Layer 1: Image Security — minimal base, non-root, pinned versions Layer 2: Build Security — secret injection, noCOPY secrets Layer 3: Runtime Security — capabilities, seccomp, AppArmor, read-only Layer 4: Registry Security — content trust, signing, vulnerability scan Layer 5: Host Security — Docker Bench, CIS, user namespace ``` ## Image Security Checklist | # | Practice | How | |---|----------|-----| | 1 | **Minimal base image** | Use `alpine` or `distroless` (Go → `scratch`) | | 2 | **Non-root user** | `USER 1000:1000` at end of Dockerfile | | 3 | **Pin versions** | `FROM alpine:3.20@sha256:...` not `alpine:latest` | | 4 | **COPY over ADD** | ADD auto-extracts tar — unexpected behavior | | 5 | **No secrets in image** | Use `--secret` or runtime injection | | 6 | **`.dockerignore`** | Exclude `.env`, `.git`, credentials | ### Secure Dockerfile ```dockerfile FROM alpine:3.20 RUN apk add --no-cache ca-certificates RUN addgroup -S app && adduser -S -G app app COPY --chown=app:app ./app /app WORKDIR /app USER app CMD ["./server"] ``` ## Runtime Security ### Capabilities (Least Privilege) ```bash # Drop ALL capabilities, add only what's needed docker run --cap-drop=ALL --cap-add=NET_BIND_SERVICE nginx # Common needed caps: NET_BIND_SERVICE, CHOWN, DAC_OVERRIDE # NEVER: --privileged (gives full host access) ``` ### Read-Only Root Filesystem ```bash # Prevents container from writing anywhere (except volumes/tmpfs) docker run --read-only --tmpfs /tmp --tmpfs /run nginx ``` ### Seccomp Profile ```bash # Custom seccomp profile (block syscalls) docker run --security-opt seccomp=profile.json app # Unconfined (NEVER in production) docker run --security-opt seccomp=unconfined app ``` ### No New Privileges ```bash # Prevent privilege escalation via setuid binaries docker run --security-opt no-new-privileges app ``` ## Secrets Management ### BuildKit Secrets (build-time) ```dockerfile # syntax=docker/dockerfile:1 FROM alpine RUN --mount=type=secret,id=aws_creds \ AWS_ACCESS_KEY_ID=$(cat /run/secrets/aws_creds) \ aws s3 cp s3://bucket/file . ``` ```bash docker build --secret id=aws_creds,src=$HOME/.aws/credentials -t app . ``` ### Docker Secrets (Swarm runtime) ```bash echo "mysecretpassword" | docker secret create db_password - docker service create --secret db_password postgres ``` ## Docker Bench Security Audit ```bash docker run --rm \ --pid host --network host \ -v /var/run/docker.sock:/var/run/docker.sock \ docker/docker-bench-security ``` ## Workflow — 安全加固流程 Step 1: **镜像安全**: `docker scout cves <image>` 扫描漏洞 → 更新基础镜像/依赖 Step 2: **Dockerfile 加固**: USER 非 root、COPY 优于 ADD、固定 digest Step 3: **运行时安全**: --read-only、--cap-drop=ALL、--security-opt no-new-privileges Step 4: **审计检查**: `docker run --rm docker/docker-bench-security` 逐条修复 Step 5: **CI 门禁**: Scout 策略阻断 critical/high CVE 合并 ## Gotchas — Common Pitfalls - **`--privileged` flag**: Gives full host access. Never use in production. → **Recovery**: Use specific `--cap-add=NET_BIND_SERVICE` instead; audit with `docker inspect --format='{{.HostConfig.Privileged}}'`. - **API keys in Dockerfile**: `ENV API_KEY=xxx` is baked into image layers forever. → **Recovery**: Use runtime injection: `docker run -e API_KEY=$KEY` or BuildKit `--mount=type=secret`. - **Root container**: Default user is root. Escaping the container means root on the host. → **Recovery**: Always `USER 1000:1000` in Dockerfile; verify with `docker exec myapp whoami`. - **Docker socket mount**: `-v /var/run/docker.sock` gives container control over ALL containers. → **Recovery**: Use Docker API with TLS auth instead of socket mount; never mount socket in production. - **Ignoring CVE remediation**: Running `docker scout` but never fixing findings. → **Recovery**: Set CI policy to block critical/high CVEs; update base images regularly. ## Boundary — 能力边界（适用与不适用场景） | 分类 | 场景 | 说明 | |------|------|------| | ✅ 能做 | Dockerfile 安全加固 | USER 非 root、COPY 优先 ADD、digest 固定 | | ✅ 能做 | 运行时安全配置 | seccomp/AppArmor/capabilities/read-only | | ✅ 能做 | Secrets 管理 | Docker secrets + BuildKit --secret + Vault | | ✅ 能做 | 安全审计（Docker Bench Security） | CIS 检查清单 + 逐条修复 | | ⚠️ 需条件 | 镜像签名（Notary） | 需 `DOCKER_CONTENT_TRUST=1` 环境变量 | | ⚠️ 需条件 | 完整合规检查 | 需结合 Scout 扫描 + 组织安全策略 | | ❌ 超范围 | CVE 漏洞扫描 | 使用 `docker-scout` | | ❌ 超范围 | 主机系统安全 | 操作系统层级 | | ❌ 超范围 | 网络安全/防火墙 | 网络管理员范畴 | ## When NOT to Use This Skill | ❌ Skip | ✅ Use Instead | |---------|---------------| | Vulnerability scanning | `docker-scout` | | Docker basics | `docker-basics` | | Production deployment | `docker-production` | | Registry management | `docker-hub` | ## Security & Stability - All security practices are based on CIS Docker Benchmark and Docker official security guidance. - Run Docker Bench Security regularly in CI/CD to detect configuration drift. - Subscribe to Docker security advisories for CVE notifications. - No executable scripts bundled. Guidance only. ## 📚 官方文档参考 | 文档 | 地址 | |------|------| | Docker 安全 | https://docs.docker.com/security/ | | Docker Hardened Images | https://docs.docker.com/dhi/ | | Docker Scout | https://docs.docker.com/scout/ | | Docker Bench Security | https://docs.docker.com/engine/security/bench/ | | seccomp 配置 | https://docs.docker.com/engine/security/seccomp/ | | AppArmor | https://docs.docker.com/engine/security/apparmor/ | ## 🧭 Docker Skills Journey > 📍 **You are here: `docker-security` — 安全加固** **← Previous**: `docker-build` | **→ Next**: `docker-scout` / `docker-cicd`