Docker CLI plugins for cosign

These plugins aim to make it slightly easier to use cosign using docker CLI commands.

They require that you have cosign and crane installed.

⚠️ These plugins are unofficial, unsupported, experimental, and likely to change. ⚠️

Ideally, this functionality would be built into the docker CLI directly (see docker/cli#3283). Until then, CLI plugins are simply a temporary solution.

Install

Docker CLI plugins are found in ~/.docker/cli-plugins, with names like docker-<command>.

You can fetch and install these from this repo like so:

mkdir -p ~/.docker/cli-plugins
for cmd in docker-pullx docker-pushx docker-sign docker-verify; do
    curl https://raw.githubusercontent.com/imjasonh/cosign-docker-cli-plugins/main/${cmd}.sh \
        -o ~/.docker/cli-plugins/${cmd} && \
        chmod +x ~/.docker/cli-plugins/${cmd}
done

Please inspect the source of these plugins before using them; you are implicitly trusting them to make security decisions for you.

Commands

docker pushx [image]

This runs docker push [image] then cosign sign [image], passing any remaining args to cosign sign.

• Note: This will not affect images pushed during docker buildx --push.
• Note: It's strongly recommended that you sign images by digest, to avoid race conditions. This command does not currently do this. For this reason, you should prefer to docker push the image separately, then cosign sign the pushed image by digest.

docker pullx [image]

This runs cosign verify [image] then docker pull [image], passing any remaining args to cosign verify.

• Note: This will not affect images pulled during builds, for example in FROM [image] statements.
• Note: It's strongly recommended that you verify images by digest, to avoid race conditions.

docker sign [image]

This ensures the image exists in the registry, and if not, pushes it using docker push [image]. Then, it runs cosign sign [image], passing any remaining args to cosign sign.

• Note: It's strongly recommended that you sign images by digest, to avoid race conditions. For this reason, you should prefer to docker push the image separately, then cosign sign the pushed image by digest.

docker verify [image]

This is simply a wrapper for cosign verify, passing all args to cosign verify.

• Note: It's strongly recommended that you verify images by digest, to avoid race conditions.

COSIGN_EXPERIMENTAL

All of these plugins support the COSIGN_EXPERIMENTAL environment variable, which enables keyless signing and verification.

For example:

COSIGN_EXPERIMENTAL=1 docker pullx ghcr.io/shipwright-io/build/shipwright-build-controller