Method GetSignaturesWithFormat

docker/docker_image_src.go:464–486

GetSignaturesWithFormat returns the image's signatures. It may use a remote (= slow) service. If instanceDigest is not nil, it contains a digest of the specific manifest instance to retrieve signatures for (when the primary manifest is a manifest list); this never happens if the primary manifest is

(ctx context.Context, instanceDigest *digest.Digest)

// (when the primary manifest is a manifest list); this never happens if the primary manifest is not a manifest list
// (e.g. if the source never returns manifest lists).
func (s *dockerImageSource) GetSignaturesWithFormat(ctx context.Context, instanceDigest *digest.Digest) ([]signature.Signature, error) {
	if err := s.c.detectProperties(ctx); err != nil {
		return nil, err
	}
	var res []signature.Signature
	switch {
	case s.c.supportsSignatures:
		if err := s.appendSignaturesFromAPIExtension(ctx, &res, instanceDigest); err != nil {
			return nil, err
		}
	case s.c.signatureBase != nil:
		if err := s.appendSignaturesFromLookaside(ctx, &res, instanceDigest); err != nil {
			return nil, err
		}
	default:
		return nil, errors.New("Internal error: X-Registry-Supports-Signatures extension not supported, and lookaside should not be empty configuration")
	}

	if err := s.appendSignaturesFromSigstoreAttachments(ctx, &res, instanceDigest); err != nil {
		return nil, err
	}
	return res, nil
}

// manifestDigest returns a digest of the manifest, from instanceDigest if non-nil; or from the supplied reference,
// or finally, from a fetched manifest.