Individual skill
container-security
Hardening for Dockerfiles, OCI images, Kubernetes manifests, and Helm charts. Use when generating a Dockerfile or image build, writing Kubernetes, Helm, or Kustomize manifests, or reviewing container changes in a pull request.
dist/claude-skills/.claude/skills/container-security/SKILL.md
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- claude-skills Repository topic
- llm Repository topic
- security Repository topic
- skills Repository topic
- writing Derived category
- devops Derived category
- security Derived category
- devops-containers Derived category
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SKILL.mdcore · 10,191 bytesSKILL.mdcore · 10,191 bytesSKILL.mdcore · 10,191 bytesSKILL.mdcore · 10,191 bytesmetadata.jsonasset · 1,062 bytesreferences/eol-base-images.mddoc · 1,644 bytesreferences/verifying-findings.mddoc · 3,962 bytes
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<!-- Native skill bundle for Claude Code. Generated by `secure-vibe dev regenerate`. -->
<!-- Do not edit by hand; the source of truth is skills/container-security/SKILL.md. -->
# Container Security
Hardening for Dockerfiles, OCI images, Kubernetes manifests, and Helm charts. Use when generating a Dockerfile or image build, writing Kubernetes, Helm, or Kustomize manifests, or reviewing container changes in a pull request.
## ALWAYS
- Use **multi-stage builds**: separate builder/test stages from the final runtime image so build toolchains and source aren't shipped. The last stage should be a minimal base — `gcr.io/distroless/<variant>`, `scratch`, or a versioned `-slim` / `-alpine` variant — pinned by SHA256 digest, not just tag. Two bases have nothing to pin: `scratch`, and a reference to an earlier stage in the same file (`FROM base`), which is pinned on that stage's own `FROM` line.
- Run as a non-root user: set `USER` explicitly on the **final stage**, as a **number** not a name. Omitting it leaves the container running as root. K8s `runAsNonRoot` rejects UID 0 and cannot resolve a username, so `USER appuser` fails at startup with "image has non-numeric user"; any non-zero UID passes, and 10000+ by convention also avoids colliding with host accounts.
- Use **`npm ci`** (and equivalents `pnpm install --frozen-lockfile`, `yarn install --frozen-lockfile`) in container builds, not `npm install`. `npm install` mutates the lockfile and resolves versions per-build, producing non-deterministic images that drift from the lockfile.
- Add a `.dockerignore` excluding `.git`, `node_modules`, `.env`, `*.pem`, `*.key`, `target/`, `.terraform/`, `dist/`, `coverage/`.
- Build with **BuildKit** (default since Docker Engine 23; `DOCKER_BUILDKIT=1` on older engines) so `RUN --mount=type=secret,id=<name>` is available for build-time credentials. `# syntax=docker/dockerfile:1` selects the frontend and does **not** enable BuildKit by itself.