Container Security

Container Security

Secure container images, registries, runtime, and orchestration for "$ARGUMENTS". Assess the full container lifecycle from image build to production runtime and define security controls at each stage.

Prerequisites

Read .metapowers/security/$ARGUMENTS/00-govern.md. If this file does not exist, tell the user:

Phase 0 (Govern) has not been completed for "$ARGUMENTS". Run a Govern skill first (e.g., /security:security-policy $ARGUMENTS), or use --skip-checks to bypass.

If --skip-checks is present in $ARGUMENTS, skip this check and log to .metapowers/security/$ARGUMENTS/skip-log.md.

Process

1. Assess base image selection:

   • Verify base images are minimal (Alpine, distroless, or slim variants preferred)
   • Confirm base images are from official, trusted sources
   • Check base image update frequency and vulnerability patching cadence
   • Identify custom base images and their maintenance process

2. Review Dockerfile best practices:

   • Run as non-root user (USER directive)
   • Use multi-stage builds to minimize final image size and attack surface
   • No secrets in image layers (no COPY of .env files, no ARG for passwords)
   • Pin dependency versions (no latest tags for base images or packages)
   • Minimize installed packages (no build tools in production images)
   • Use .dockerignore to prevent sensitive files from being included in build context

3. Plan image scanning:

   • Select scanning tools (Trivy, Snyk Container, Grype, Clair)
   • Integrate scanning into CI/CD pipeline (fail build on critical/high vulnerabilities)
   • Define scanning cadence for images already in production (catch newly discovered CVEs)
   • Set vulnerability thresholds (block critical, warn on high, track medium)

4. Secure container registry:

   • Use private registry with access controls (not public Docker Hub for proprietary images)
   • Enable image signing and verification (Docker Content Trust, cosign/Sigstore)
   • Implement image promotion workflow (dev -> staging -> production with gates)
   • Set image retention and cleanup policies
   • Enable vulnerability scanning at registry level

5. Harden runtime security:

   • Run containers with read-only root filesystem where possible
   • Set resource limits (CPU, memory) to prevent resource exhaustion attacks
   • Drop all Linux capabilities and add back only those required
   • Use seccomp and AppArmor/SELinux profiles to restrict system calls
   • Disable privilege escalation (no-new-privileges flag)

6. Secure orchestration (Kubernetes):

   • Implement Kubernetes RBAC with least-privilege service accounts
   • Enforce Pod Security Standards (restricted level for production workloads)
   • Define network policies to restrict pod-to-pod communication
   • Use namespaces for multi-tenant isolation
   • Secure the Kubernetes API server (authentication, audit logging, admission controllers)
   • Implement admission controllers (OPA/Gatekeeper, Kyverno) to enforce policies

7. Write the artifact to .metapowers/security/$ARGUMENTS/02-protect.md with heading:

   Container Security

   Include sections:

   • Base Image Assessment — current base images, sources, and update practices
   • Dockerfile Review — findings on build best practices
   • Image Scanning — tool selection, CI/CD integration, and vulnerability thresholds
   • Registry Security — access controls, signing, and promotion workflow
   • Runtime Hardening — resource limits, capability restrictions, and filesystem policies
   • Orchestration Security — RBAC, pod security, network policies, and admission control
   • Implementation Roadmap — prioritized actions from quick wins to long-term hardening

Output

The container security plan written to .metapowers/security/$ARGUMENTS/02-protect.md. Present a summary to the user highlighting:

• Current container security posture and key gaps
• Image scanning integration plan
• Runtime hardening priorities
• Orchestration security controls to implement