Q: Following an executive order on cybersecurity, your platform team must guarantee that every container deployed into production was built exclusively from approved source repositories via verified CI/CD workflows, without external tamper risks. You need to implement an immutable SLSA Level 3 provenance attestation pipeline that signs artifacts without static long-lived private keys, publishes in-toto attestations to the OCI registry, and enforces runtime verification in Kubernetes via Kyverno.

Adopt the official SLSA GitHub Actions generator workflow (`slsa-framework/slsa-github-generator`). This workflow executes in an isolated, trusted GitHub runner with hardened permissions, verifying that the source code, build inputs, and container image digest cannot be forged by runner tampering.

name: SLSA Build
on:
  push:
    tags: ['v*.*.*']

jobs:
  build:
    runs-on: ubuntu-latest
    outputs:
      image: ${{ steps.build.outputs.image }}
      digest: ${{ steps.build.outputs.digest }}
    steps:
      - uses: actions/checkout@v4
      - id: build
        run: |
          docker buildx build --push -t ghcr.io/myorg/app:v1.0.0 .
          DIGEST=$(docker inspect --format='{{index .RepoDigests 0}}' ghcr.io/myorg/app:v1.0.0 | cut -d'@' -f2)
          echo "image=ghcr.io/myorg/app" >> $GITHUB_OUTPUT
          echo "digest=$DIGEST" >> $GITHUB_OUTPUT

  provenance:
    needs: [build]
    permissions:
      id-token: write
      packages: write
    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_container_slsa3.yml@v1.9.0
    with:
      image: ${{ needs.build.outputs.image }}
      digest: ${{ needs.build.outputs.digest }}
      registry-username: ${{ github.actor }}
    secrets:
      registry-password: ${{ secrets.GITHUB_TOKEN }}

Use `cosign` to verify the generated predicate in the OCI registry. Inspect the JSON attestation containing the builder identity, source commit SHA, workflow inputs, and build environment metadata.

# Verify SLSA attestation using Cosign keyless verification
cosign verify-attestation \
  --type slsaprovenance \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  --certificate-identity-regexp '^https://github.com/slsa-framework/slsa-github-generator/' \
  ghcr.io/myorg/app@sha256:d8b74a58...

# Extract and view the in-toto predicate
cosign verify-attestation --type slsaprovenance ghcr.io/myorg/app@sha256:... | jq '.payload | @base64d | fromjson'

Configure Kyverno on the production Kubernetes cluster to reject any Pod whose container image lacks a valid SLSA provenance attestation issued by the enterprise repository.

apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
  name: verify-slsa-provenance
spec:
  validationFailureAction: Enforce
  rules:
    - name: check-slsa-attestation
      match:
        resources:
          kinds: [Pod]
      verifyImages:
        - imageReferences: ['ghcr.io/myorg/*']
          attestations:
            - type: https://slsa.dev/provenance/v0.2
              conditions:
                - all:
                    - key: "{{ builder.id }}"
                      operator: Equals
                      value: "https://github.com/slsa-framework/slsa-github-generator/.github/workflows/generator_container_slsa3.yml@refs/tags/v1.9.0"
              issuer: https://token.actions.githubusercontent.com
              subject: https://github.com/myorg/*

Conduct penetration tests simulating compromised build dependencies. Validate that unauthorized builds or locally pushed developer tags fail Kyverno validation and trigger security alerts.