Verification configuration

Example

Here you can see an example of a configuration for verifying signatures using the Sigstore workflow:

---
apiVersion: v1

allOf:
  - kind: githubAction
    owner: kubewarden   # mandatory
    repo: policy-server # optional
    annotations:  # optional
      env: prod

anyOf: # at least `anyOf.minimumMatches` are required to match
  minimumMatches: 2 # default is 1
  signatures:
  - kind: pubKey
    owner: alice # optional
    key: | # mandatory
         -----BEGIN PUBLIC KEY-----
         MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEQiTy5S+2JFvVlhUwWPLziM7iTM2j
         byLgh2IjpNQN0Uio/9pZOTP/CsJmXoUNshfpTUHd3OxgHgz/6adtf2nBwQ==
         -----END PUBLIC KEY-----
    annotations:  # optional
      env: prod
  - kind: genericIssuer
    issuer: https://github.com/login/oauth
    subject:
      equal: alice@example.com
  - kind: genericIssuer
    issuer: https://token.actions.githubusercontent.com
    subject:
      equal: https://github.com/bob/app-example/.github/workflows/release.yml@refs/heads/main
    annotations:  # optional
      env: prod
  - kind: genericIssuer
    issuer: https://token.actions.githubusercontent.com
    subject:
      urlPrefix: https://github.com/bob # <- it will be post-fixed with `/` for security reasons

Format

The config has 2 root keys:

• allOf: All verification info listed here must be satisfied for accepting a container image as signed.
• anyOf: At least anyOf.minimumMatches of all info listed here must be satisfied for accepting a container image as signed.

These two root keys accept an array of keys of type kind. A full list of accepted keys based on different use cases is given below.

• pubKey: for signatures performed with traditional public/private key cryptography.
• githubAction: for signatures performed with Sigstore's keyless workflow inside GitHub Actions. Kubewarden checks this information against the x509 certificate extension workflow_repository created by the OpenID Connect of Github, and not only the issuer and subject. Hence, it is strongly recommended to use this kind if dealing with GitHub Actions.
• genericIssuer: for signatures performed with Sigstore's keyless worfklow, where the user needs to validate the certificate issuer and subject on their own. It accepts a subject, which can be:
  • equal: the value passed here must match exactly against the subject in the signing certificate.
  • urlPrefix: the value passed here is post-fixed with / to prevent typo-squatting, and must be a prefix of the subject in the signing certificate.

the kind key optionally accepts an annotations key, with a list of key-values, that must be present in the signature.