Description

mathieu-benoit

opened on Feb 3, 2026

Issue body actions

Description

Today if we do this:

    uses: docker/github-builder/.github/workflows/build.yml@v1
    with:
      output: image
      push: true
      platforms: linux/amd64,linux/arm64
      sbom: true
      meta-images: |
        ghcr.io/my-org/my-image
      meta-tags: |
        latest

We are able to cosign verify the two manifests per platform linux/amd64 and linux/arm64 individually and explicitly.

But we are not able to do this:

cosign verify \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  --certificate-identity-regexp ^https://github.com/docker/github-builder/.github/workflows/build.yml.*$ \
  ghcr.io/my-org/my-image:FIXME-WITH-LATEST-DIGEST

We'll get this error because there is no signature on the main tag/manifest:

Error: no signatures found
error during command execution: no signatures found

It's common practice to have the main tag/digest in Dockerfile for base images and in Kubernetes manifests for final container images to refer to the main tag/digest, letting then the platform pulling the actual digest based on the arch/platform. In the meantime, admission controller like Kyverno will check the signature on the main tag/digest.

Could we add the cosign signature on the main tag/digest too?

Reacted by AFCMS and Ganesh Tiwari

Reacted by AFCMS and Ganesh Tiwari

Reacted by Tang Rufus and Ganesh Tiwari

Activity

1. mathieu-benoit

   added

   kind/enhancementNew feature or requestNew feature or request

   status/triage

   on Feb 3, 2026
2. mathieu-benoit commented on Mar 15, 2026

   

   mathieu-benoit

   on Mar 15, 2026

   Author

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   It was also reported there docker-hardened-images/catalog#38. Not directly related but just capturing that as a common ask/requirement, simplifying the UX for end users to do cosign verify.

   See other examples here:

   • https://kubernetes.io/docs/tasks/administer-cluster/verify-signed-artifacts/#verifying-image-signatures
   • https://some-natalie.dev/blog/sigstore-multiarch/

   Reacted by Ganesh Tiwari
3. mathieu-benoit commented on Mar 19, 2026

   

   mathieu-benoit

   on Mar 19, 2026

   Author

   More actions

   Related to this too: #153.

   Reacted by Ganesh Tiwari
4. AFCMS commented on Apr 10, 2026

   

   AFCMS

   on Apr 10, 2026

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   I migrated a project from manual build + cosign to github-builder with signing enabled, this caused artifacthub to consider the package not signed.

   I am pretty sure it expect the main manifest to be signed.

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