Feature Request: Ensure GitHub Action Dependencies are Pinned

[wadells]

The GitHub Actions documentation on "Using 3rd Party Actions" states that users should:

Pin actions to a full length commit SHA

Pinning an action to a full length commit SHA is currently the only way to use an action as an immutable release. Pinning to a particular SHA helps mitigate the risk of a bad actor adding a backdoor to the action's repository, as they would need to generate a SHA-1 collision for a valid Git object payload. When selecting a SHA, you should verify it is from the action's repository and not a repository fork.

However, GitHub does not currently provide a way for users to enforce this guideline when new GitHub Actions are added to a repository. Instead, users are turning to 3rd party actions like the following:

https://github.com/zgosalvez/github-actions-ensure-sha-pinned-actions

At Teleport, we already use dependency review to look for security and license issues in incoming dependencies. I'd also like dependency-review-action to have a way to enforce that dependencies are pinned. I care about this feature for GitHub Actions more than my other ecosystems (go, javascript, terraform) because those ecosystems have lock files built into the dependency management toolchain.

[febuiles]

@wadells thank you for taking the time to share your ideas.

I think this would be a nice thing to have, maybe added as a config option (another one 😅) to maintain support with existing users. I've tagged it and hopefully can get to this at some point in the future. If you want to open a pull request I'd be more than happy to help out getting this out quicker.