Handle signing and attesting blobs #1395
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The following is the coverage report on the affected files.
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/lgtm |
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| se, err := ociremote.SignedEntity(req.Artifact, ociremote.WithRemoteOptions(s.remoteOpts...)) | ||
| if err != nil { | ||
| if _, isEntityNotFoundErr := err.(*ociremote.EntityNotFoundError); isEntityNotFoundErr { |
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Whenever there is an entity not found we are default considering it as a blob, what if the digest was incorrect or the blob is not there? Is there a possibility to check if such a blob exists before attesting?
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The code is not necessarily handling a blob but it's handling the case where the image reference does not reference an existing Image Manifest or Image Index. It just so happens that this is what makes the blob signing/attesting work. I linked in the description how cosign itself implements this logic. I think it's safe to copy what they're doing there.
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@lcarva Could you help clarify the scenario in which Tekton PRs or TRs would result in standalone blobs being pushed to container registries (i.e., not part of an image or manifest)? From my understanding, typical Tekton outputs are full OCI images. Are there cases where individual blobs are pushed independently and need signing or attestation support? This context would help in understanding the need for handling blob references explicitly in this logic. |
Chains fetches existing information about the container images it signs and attests. This works well when the image reference refers to an Image Index or an Image Manifest since those are served from the same endpoint in a container registry. However, when fetching information about a blob (layer) a different endpoint is needed. Cosign handles this behavior by making this step optional: https://github.com/sigstore/cosign/blob/c86498055d0c4ea2f39076064aa094db12f85f6a/cmd/cosign/cli/sign/sign.go#L181-L186 Thus it is possible to sign/attest a blob with the cosign CLI. This commit implements the same logic to Chains so it can also sign/attest blobs. Signed-off-by: Luiz Carvalho <[email protected]>
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It's really up to a Task. With something like oras, I can push individual blobs to the registry and emit those references in my Task result. The use case I'm exploring that highlighted this was that I was using a Tekton Task to build a python wheel. I want to make sure the digest of the wheel (same as the digest of the blob) is in the SLSA Provenance. |
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The following is the coverage report on the affected files.
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| ctx := logtesting.TestContextWithLogger(t) | ||
| _, err = storer.Store(ctx, &api.StoreRequest[name.Digest, *intoto.Statement]{ |
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Any chance we can assert the output anyway ?
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I don't think that's important. It looks like the Store method is half-baked and always returns &api.StoreResponse{}.
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Yeah I did check that, but thought if we can assert the logs, but that should be fine as we are check if the error is nil or not
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/approve |
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/lgtm Not sure if I can do this 🙏 |
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/lgtm |
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Chains fetches existing information about the container images it signs and attests. This works well when the image reference refers to an Image Index or an Image Manifest since those are served from the same endpoint in a container registry. However, when fetching information about a blob (layer) a different endpoint is needed.
Cosign handles this behavior by making this step optional: https://github.com/sigstore/cosign/blob/c86498055d0c4ea2f39076064aa094db12f85f6a/cmd/cosign/cli/sign/sign.go#L181-L186
Thus it is possible to sign/attest a blob with the cosign CLI. This commit implements the same logic to Chains so it can also sign/attest blobs.
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