feat: cosign-compatible signatures for OCI-SIF #3510
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Add a new `--cosign` mode to `singularity sign`, which will apply a cosign-compatible signature to a container image in an OCI-SIF, and store the signature image in the OCI-SIF, using the name.ref association defined by sylabs/oci-tools. Unlike the upstream sylabs/oci-tools code, Singularity currently only creates / considers OCI-SIF images that contain a single OCI image. Consequently there is no signature handling for image indices in Singularity at this point. From this commit onwards, Singularity ignores cosign images in the OCI-SIF when looking for an OCI image to execute, push etc. Older versions of Singularity will error when attempting to execute a signed image, as they expect only one image in an OCI-SIF, with no filtering of non-executable cosign related images. Fixes sylabs#3492
tri-adam
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Feb 8, 2025
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Description of the Pull Request (PR):
Add a new
--cosignmode tosingularity sign, which will apply a cosign-compatible signature to a container image in an OCI-SIF, and store the signature image in the OCI-SIF, using the name.ref association defined by sylabs/oci-tools.Unlike the upstream sylabs/oci-tools code, Singularity currently only creates / considers OCI-SIF images that contain a single OCI image. Consequently there is no signature handling for image indices in Singularity at this point.
From this commit onwards, Singularity ignores cosign images in the OCI-SIF when looking for an OCI image to execute, push etc. Older versions of Singularity will error when attempting to execute a signed image, as they expect only one image in an OCI-SIF, with no filtering of non-executable cosign related images.
This fixes or addresses the following GitHub issues:
Before submitting a PR, make sure you have done the following:
make checkand tested this PR locally with amake test, andmake testallif possible (see CONTRIBUTING.md).