[fseldow]

Description

Adds cosign v3 Sigstore bundle signature support to Ratify v2.

Cosign v3 stores signatures as OCI 1.1 referrers with artifact type application/vnd.dev.sigstore.bundle.v0.3+json. Attestations (cosign attest, GitHub artifact attestations, etc.) use the same artifact type and are only distinguished by the in-toto predicate type.

Changes:

• Bump github.com/notaryproject/ratify-verifier-go/cosign to feat(cosign): support cosign v3 Sigstore bundle signatures ratify-verifier-go#83, which adds bundle verification.
• Verifiable now delegates to cosign.IsVerifiable:
  • legacy application/vnd.dev.cosign.artifact.sig.v1+json signatures: unchanged
  • bundle referrers annotated with dev.sigstore.bundle.predicateType: https://sigstore.dev/cosign/sign/v1 (or without the annotation): verified
  • bundle referrers annotated with any other predicate type (attestations, possibly from other signers): skipped, so they produce no verifier report and cannot fail the policy
• Because the annotation is unsigned, ratify-verifier-go additionally enforces the signed in-toto predicateType after verification, so a trusted attestation cannot be accepted as a signature.

This mirrors the v1 change in #3060.

Dependency

Draft until notaryproject/ratify-verifier-go#83 merges; the dependency will then be bumped to the merged commit.

Testing

• Unit tests for Verifiable covering legacy signatures, bundle signatures, bundles without the annotation, and attestation bundles.
• go test ./internal/verifier/... ./internal/executor/...
• E2E coverage with cosign v3-signed images can follow in a separate PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.50%. Comparing base (0e33d55) to head (577833f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3087   +/-   ##
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  Coverage   86.50%   86.50%           
=======================================
  Files          54       54           
  Lines        2935     2935           
=======================================
  Hits         2539     2539           
  Misses        302      302           
  Partials       94       94           

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[Copilot]

🔵 Needs a closer look

Cryptographic bundle verification and signed-predicate enforcement rely on unmerged ratify-verifier-go#83, requiring review of the final merged dependency and validation of real cosign v3 interoperability before approval.

No open issues 🎉

What changed in this PR

Adds cosign v3 Sigstore bundle signature support to Ratify v2 while preserving legacy signature handling and skipping bundles annotated as attestations.

Changes:

• Updates the cosign verifier dependency to a revision with bundle verification support.
• Delegates artifact eligibility checks to cosign.IsVerifiable.
• Adds unit cases for bundle signatures, missing predicate annotations, and attestation exclusion.

File	Description
internal/​verifier/​cosign/​register.go	Delegates signature eligibility checks to the cosign library.
internal/​verifier/​cosign/​register_test.go	Covers bundle eligibility and uses library artifact-type constants.
go.sum	Updates checksums for the cosign dependency revision.
go.mod	Pins the cosign dependency with bundle support.

_{Review effort: Balanced}