Optional: Signing the Lambda Layers with AWS Code Signing

Is your feature request related to a problem? Please describe.

https://github.com/open-telemetry/opentelemetry-lambda/blob/main/.github/workflows/publish-layer-collector.yml

Running the above workflow to produce private layers.

If a team is running an AWS CodeSigner, then the publish job should also include an optional capability to sign the layers to confirm the provenance.

https://docs.aws.amazon.com/lambda/latest/dg/governance-code-signing.html

Describe the solution you'd like

I'd like the GitHub action to include an artefact attestation for the zip binaries and each of the language-specific binaries released.
https://docs.github.com/en/actions/how-tos/secure-your-work/use-artifact-attestations/use-artifact-attestations and couple that with AWS's codesigner for the zip files.

aws signer start-signing-job \
--source 's3={bucketName=xxxx,key=collector-layer.zip,version=xxxxx}' \
--destination 's3={bucketName=xxxx,prefix=signed/}' \
--profile-name SigningProfile_XXXXX
--client-request-token XXXUNIQUE_FROM_GITHUB_JOB

The additional parameter would need to be the SigningProfile, that would need to be present in the account that the GHA is uploading to.

Prerequisites

• The Github OIDC role would also need permission to be able to sign.
• The S3 bucket needs to have versioning enabled.

Describe alternatives you've considered

I think the GitHub attestation step is optional, but could allow extra confidence that the artefacts have not been tampered with, especially if the signing job connects directly to the GitHub attestation.

Additional context

I'm keen to raise a PR to demonstrate that this could be an optional extra; but wanted to raise the issue first as I couldn't find evidence of where this has been/not-been considered.

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Start with .github/workflows/publish-layer-collector.yml and review the AWS Code Signing documentation and example command in the issue. Trace how the workflow uploads layer ZIPs, then determine how optional signing-profile input, OIDC signing permissions, S3 versioning, and artifact attestations should fit. Done means the workflow can enable signing without affecting its default path.