Add logic to detect and use ambient OIDC from exec envs. #644
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This is based on some work I have been doing here: https://github.com/mattmoor/oidc-magic At present, it is fairly tedious to use the "keyless" flow inside of environments that have a form of ambient OIDC (e.g. GKE workload identity). For example, in the context of Tekton, one needs to overlay `cosign` on an image like `docker.io/google/cloud-sdk:slim`, and then during execution have the step do something like: ```yaml command: ["/bin/sh"] args: - "-c" - | # Generate an identity token. IDENTITY_TOKEN=$(gcloud auth print-identity-token --audiences=sigstore) # Use the identity token to sign the image. cosign sign \ -identity-token $IDENTITY_TOKEN \ my.registry/the-image@sha256:deadbeef ``` This change adds support for detecting when `cosign` is executing within an environment with this kind of ambient authentication, and automatically producing one when `-identity-token` is not specified (and `COSIGN_EXPERIMENTAL=true`). This means the same signing can now be done with: ```yaml args: ["sign", "my.registry/the-image@sha256:deadbeef"] ``` This is much simpler, but also the image will be both smaller (distroless) and more portable (not just GCP, but any provider we link). Signed-off-by: Matt Moore <mattomata@gmail.com>
dlorenc
approved these changes
Sep 11, 2021
This was referenced Dec 2, 2021
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This is based on some work I have been doing here: https://github.com/mattmoor/oidc-magic
At present, it is fairly tedious to use the "keyless" flow inside of environments that have a form of ambient OIDC (e.g. GKE workload identity). For example, in the context of Tekton, one needs to overlay
cosignon an image likedocker.io/google/cloud-sdk:slim, and then during execution have the step do something like:This change adds support for detecting when
cosignis executing within an environment with this kind of ambient authentication, and automatically producing one when-identity-tokenis not specified (andCOSIGN_EXPERIMENTAL=true).This means the same signing can now be done with:
This is much simpler, but also the image will be both smaller (distroless) and more portable (not just GCP, but any provider we link).