Node Image Provenance: SLSA Attestations Before ECS or Lambda Pulls

Attacker pushes evil:latest to ECR
  OR steals CI OIDC to build from a fork
Without verify: ECS rolls out evil
With SLSA gate: digest lacks trusted provenance → deploy fails closed

# GitHub Actions sketch
- uses: docker/build-push-action@v6
  with:
    push: true
    tags: ${{ env.ECR }}/checkout:${{ github.sha }}
    provenance: true
    sbom: true

- name: Cosign sign
  run: |
    cosign sign --yes ${{ env.ECR }}/checkout@${{ steps.build.outputs.digest }}
    cosign attest --yes --predicate slsa-provenance.json \
      ${{ env.ECR }}/checkout@${{ steps.build.outputs.digest }}

# Node image: reproducible-ish defaults
FROM public.ecr.aws/docker/library/node:22-bookworm-slim@sha256:...
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci --omit=dev
COPY dist ./dist
USER node
CMD ["node", "dist/server.js"]

# CD gate
DIGEST=$(aws ecr describe-images --repository-name checkout \
  --image-ids imageTag=$GIT_SHA --query 'imageDetails[0].imageDigest' --output text)

cosign verify --certificate-identity-regexp '.*github.com/acme/checkout.*' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  "$ECR/checkout@$DIGEST"

cosign verify-attestation --type slsaprovenance \
  "$ECR/checkout@$DIGEST" | jq -e '.payload' >/dev/null

# only then:
aws ecs update-service --force-new-deployment ...
# or Lambda package / container image URI with that digest

# OPA/Conftest: deny mutable tags
deny[msg] {
  input.image.tag == "latest"
  msg := "mutable tag latest forbidden"
}
deny[msg] {
  not input.provenance.verified
  msg := "missing verified SLSA provenance"
}