This is unreleased documentation for Runtime Enforcer 0.11-dev.

Verifying Kubewarden Runtime Enforcer

The Kubewarden Runtime Enforcer project signs what it publishes, so that you can check that an artifact is the one the project built. For each release, the project publishes:

  • Signed container images, one per component.

  • A signed Software Bill of Materials (SBOM) and a signed provenance attestation for each image and architecture.

  • A signed Helm chart.

The signatures use Sigstore in keyless mode. The signing certificate names the GitHub Actions workflow that built the artifact. Each cosign command below passes two values:

  • --certificate-oidc-issuer: always https://token.actions.githubusercontent.com.

  • --certificate-identity: the workflow file and the Git ref of the release. For a release of Runtime Enforcer, this is https://github.com/kubewarden/runtime-enforcer/.github/workflows/release.yml@refs/tags/v0.10.1.

Use the exact identity, with the release tag, as the commands below do. A pattern such as https://github.com/kubewarden/* passed to --certificate-identity-regexp accepts an artifact from any workflow in any repository of the organization. The exact identity accepts only an artifact that this release workflow built.

The examples use the release v0.10.1 and the chart version 0.2.1. Replace them with the versions that you verify.

Container images

Runtime Enforcer publishes three images, all at ghcr.io/kubewarden/runtime-enforcer/:

  • controller

  • agent

  • debugger

The release workflow signs each single-architecture image and the multi-architecture index. To verify the controller image, run:

cosign verify \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity="https://github.com/kubewarden/runtime-enforcer/.github/workflows/release.yml@refs/tags/v0.10.1" \
  ghcr.io/kubewarden/runtime-enforcer/controller:v0.10.1

Verification for ghcr.io/kubewarden/runtime-enforcer/controller:v0.10.1 --
The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - Existence of the claims in the transparency log was verified offline
  - The code-signing certificate was verified using trusted certificate authority certificates

<snipped json>

The same command, with agent or debugger in place of controller, verifies the other two images.

SBOM and provenance attestations

For each image and each architecture, the release workflow extracts an SBOM in SPDX format and a provenance attestation in SLSA format. It signs each file and attaches the files to the GitHub release. The names follow this pattern:

  • RuntimeEnforcer-<component>-attestation-<arch>-provenance.intoto.jsonl

  • RuntimeEnforcer-<component>-attestation-<arch>-sbom.json

Each file has a Sigstore bundle with the same name and the suffix .bundle.sigstore. Download the file and its bundle from the release page, then verify the provenance:

cosign verify-blob \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity="https://github.com/kubewarden/runtime-enforcer/.github/workflows/release.yml@refs/tags/v0.10.1" \
  --bundle RuntimeEnforcer-controller-attestation-amd64-provenance.intoto.jsonl.bundle.sigstore \
  RuntimeEnforcer-controller-attestation-amd64-provenance.intoto.jsonl

Verified OK

And the SBOM:

cosign verify-blob \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity="https://github.com/kubewarden/runtime-enforcer/.github/workflows/release.yml@refs/tags/v0.10.1" \
  --bundle RuntimeEnforcer-controller-attestation-amd64-sbom.json.bundle.sigstore \
  RuntimeEnforcer-controller-attestation-amd64-sbom.json

Verified OK

After the check, you can read the files. The SBOM lists the packages in the image. The provenance names the source commit, the builder, and the build parameters.

The same attestations are also attached to each image in the registry, in the format that Docker uses. The signed copies are the release assets. To read the registry copy, list the attestation manifest with crane:

crane manifest ghcr.io/kubewarden/runtime-enforcer/controller:v0.10.1 \
  | jq '.manifests[] | select(.annotations["vnd.docker.reference.type"]=="attestation-manifest")'

Then fetch the manifest by its digest and read each layer with crane blob.

Helm chart

The Runtime Enforcer chart is in the Helm repository at https://charts.kubewarden.io and, as an OCI artifact, at ghcr.io/kubewarden/charts/runtime-enforcer. The OCI copy is signed. The chart is released from the kubewarden/helm-charts repository, so the identity names that workflow:

cosign verify \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity="https://github.com/kubewarden/helm-charts/.github/workflows/helm-chart-release.yml@refs/heads/main" \
  ghcr.io/kubewarden/charts/runtime-enforcer:0.2.1

Verification for ghcr.io/kubewarden/charts/runtime-enforcer:0.2.1 --
The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - Existence of the claims in the transparency log was verified offline
  - The code-signing certificate was verified using trusted certificate authority certificates

<snipped json>

The chart also has a GitHub build provenance attestation. The GitHub CLI verifies it:

gh attestation verify oci://ghcr.io/kubewarden/charts/runtime-enforcer:0.2.1 \
  --repo kubewarden/helm-charts

To list every image that the chart deploys, render it and extract the image fields:

helm template runtime-enforcer oci://ghcr.io/kubewarden/charts/runtime-enforcer \
  --version 0.2.1 \
  | yq '..|.image? | select(.)' \
  | sort -u

Verify each Runtime Enforcer image in that list as the container images section shows.

Third-party images

The chart also deploys one image that the Runtime Enforcer project does not build and does not sign:

  • otel/opentelemetry-collector-contrib, when telemetry.collectorStrategy is default.

Verify it with the method that its own project documents.

kubectl plugin

The kubectl-runtime_enforcer binaries on the release page come with a SHA-256 checksum file each, named with the suffix .sha256. The checksum lets you check that the download is complete and not corrupted:

sha256sum -c kubectl-runtime_enforcer-linux-amd64.sha256
kubectl-runtime_enforcer-linux-amd64: OK

The plugin binaries have no signature and no provenance attestation at this time. The checksum shows that the file matches what the release page lists. It does not show who built the file. If you need that assurance, build the plugin from the tagged source. See Build requirements.