This is unreleased documentation for Network Enforcer 0.4-dev.

Verifying Kubewarden Network Enforcer

The Kubewarden Network 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:

A signed container image.
A signed Software Bill of Materials (SBOM) and a signed provenance attestation for each architecture of the image.
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-regexp: the workflow file that built the artifact.

Network Enforcer builds, signs and attests its image with one shared reusable workflow that lives in the kubewarden/github-actions repository. The signer identity of the image and of the SBOM and provenance files is:

https://github.com/kubewarden/github-actions/.github/workflows/container-release.yml@<ref>

The <ref> is the commit of the reusable workflow, not the release tag of Network Enforcer. For that reason the commands below match the identity with --certificate-identity-regexp, anchored to the full path of the workflow file.

That identity names the builder, not the release. The same builder signs the artifacts of every Kubewarden component. So each command also pins the caller repository and the release tag, with --certificate-github-workflow-repository and --certificate-github-workflow-ref. A signed file from another repository or another release does not pass. The flags do not bind the component. Every component of one release shares these certificate values, so a blob and its bundle from one component verify under another component’s filename. To check which image a file describes, read the subject field inside the file.

Keep the full path of the workflow file in the pattern, as the commands below do. A pattern such as https://github.com/kubewarden/* accepts an artifact from any workflow in any repository of the organization. The anchored pattern accepts only an artifact that container-release.yml built.

The examples use the release v0.3.0 and the chart version 0.1.3. Replace them with the versions that you verify.

Container images

Network Enforcer publishes one image, ghcr.io/kubewarden/network-enforcer/controller. The shared workflow signs each single-architecture image and the multi-architecture index. To verify it, run:

cosign verify \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity-regexp='^https://github\.com/kubewarden/github-actions/\.github/workflows/container-release\.yml@' \
  --certificate-github-workflow-repository=kubewarden/network-enforcer \
  --certificate-github-workflow-ref='refs/tags/v0.3.0' \
  ghcr.io/kubewarden/network-enforcer/controller:v0.3.0

Verification for ghcr.io/kubewarden/network-enforcer/controller:v0.3.0 --
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>

Build provenance (SLSA Build L3)

The shared workflow runs actions/attest on the multi-architecture index of the image. GitHub writes the provenance from the OIDC token of the workflow job and signs it. No build step can change it. This attestation is what gives the image SLSA Build L3.

GitHub stores the attestation in the Network Enforcer repository and next to the image in the registry. Verify it with the GitHub CLI:

gh attestation verify oci://ghcr.io/kubewarden/network-enforcer/controller:v0.3.0 \
  --repo kubewarden/network-enforcer \
  --signer-workflow kubewarden/github-actions/.github/workflows/container-release.yml

Loaded digest sha256:... for oci://ghcr.io/kubewarden/network-enforcer/controller:v0.3.0
Loaded 1 attestation from GitHub API
✓ Verification succeeded!

--repo names the repository that stores the attestation. --signer-workflow names the workflow that signed it. The check fails for an attestation signed by any other workflow.

SBOM and provenance attestations

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

NetworkEnforcer-controller-attestation-<arch>-provenance.intoto.jsonl
NetworkEnforcer-controller-attestation-<arch>-sbom.json

These files come from the container build. They carry the layer and build-arg detail that actions/attest does not. The actions/attest attestation above is the one that carries the SLSA level.

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-regexp='^https://github\.com/kubewarden/github-actions/\.github/workflows/container-release\.yml@' \
  --certificate-github-workflow-repository=kubewarden/network-enforcer \
  --certificate-github-workflow-ref='refs/tags/v0.3.0' \
  --bundle NetworkEnforcer-controller-attestation-amd64-provenance.intoto.jsonl.bundle.sigstore \
  NetworkEnforcer-controller-attestation-amd64-provenance.intoto.jsonl

Verified OK

And the SBOM:

cosign verify-blob \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity-regexp='^https://github\.com/kubewarden/github-actions/\.github/workflows/container-release\.yml@' \
  --certificate-github-workflow-repository=kubewarden/network-enforcer \
  --certificate-github-workflow-ref='refs/tags/v0.3.0' \
  --bundle NetworkEnforcer-controller-attestation-amd64-sbom.json.bundle.sigstore \
  NetworkEnforcer-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 the 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/network-enforcer/controller:v0.3.0 \
  | 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 Network Enforcer chart is in the Helm repository at https://charts.kubewarden.io and, as an OCI artifact, at ghcr.io/kubewarden/charts/network-enforcer. The OCI copy is signed. The kubewarden/helm-charts repository builds, signs and attests the chart with its own chart-release.yml reusable workflow. The workflow packages the chart from the commit that the signature and the attestation name, so no step outside the workflow can change it.

The chart carries two cosign signature formats. Run the following two commands to verify them:

cosign verify --new-bundle-format=false \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity-regexp='^https://github\.com/kubewarden/helm-charts/\.github/workflows/chart-release\.yml@' \
  --certificate-github-workflow-repository=kubewarden/helm-charts \
  --certificate-github-workflow-ref='refs/heads/main' \
  ghcr.io/kubewarden/charts/network-enforcer:0.1.3

Verification for ghcr.io/kubewarden/charts/network-enforcer:0.1.3 --
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>

cosign verify-attestation --new-bundle-format=true \
  --type https://sigstore.dev/cosign/sign/v1 \
  --certificate-oidc-issuer=https://token.actions.githubusercontent.com \
  --certificate-identity-regexp='^https://github\.com/kubewarden/helm-charts/\.github/workflows/chart-release\.yml@' \
  ghcr.io/kubewarden/charts/network-enforcer:0.1.3

The workflow also runs actions/attest on the chart. That attestation gives the chart SLSA Build L3. GitHub stores it in the kubewarden/helm-charts repository. The GitHub CLI verifies it:

gh attestation verify oci://ghcr.io/kubewarden/charts/network-enforcer:0.1.3 \
  --repo kubewarden/helm-charts \
  --signer-workflow kubewarden/helm-charts/.github/workflows/chart-release.yml

The workflow also attests the packaged .tgz file that the GitHub release carries. Download the file from the release page, then verify it:

gh attestation verify network-enforcer-0.1.3.tgz \
  --repo kubewarden/helm-charts \
  --signer-workflow kubewarden/helm-charts/.github/workflows/chart-release.yml

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

helm template network-enforcer oci://ghcr.io/kubewarden/charts/network-enforcer \
  --version 0.1.3 \
  | yq '..|.image? | select(.)' \
  | sort -u

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

Third-party images

The chart also deploys images that the Network Enforcer project does not build and does not sign:

otel/opentelemetry-collector-contrib, when telemetry.collectorStrategy is default.
fluent/fluent-bit, when controller.provider.name is istio.

Verify them with the method that their own projects document.