Add OpenSSF Scorecard gating action

[cgwalters]

A while ago I was working on goose and found they'd committed binary files into their git repo, and worked on a PR to block that:
block/goose#6031

However at the time I'd investigated OpenSSF (which has a check for this among other things) but didn't quite get it to work.

After some iteration with my agent, this model seems to work well. That said I think what I'd like to do is propose something like this to upstream OpenSSF - their default action doesn't check each commit for example, but we want to deny binaries in all commits.

This also implements a model where the check only fails if the score regresses.

Assisted-by: OpenCode (Opus 4.5)

[gemini-code-assist]

Summary of Changes

Hello @cgwalters, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new GitHub Action aimed at bolstering the security posture of the repository by integrating OpenSSF Scorecard checks directly into the CI/CD pipeline. The action is designed to proactively identify and prevent any regression in the project's OpenSSF Scorecard rating by evaluating each commit within a pull request against a defined baseline. This ensures that security standards are consistently maintained and any potential vulnerabilities or deviations are caught early in the development cycle.

Highlights

• New GitHub Action: Introduces a new composite GitHub Action named 'OpenSSF Scorecard Gate' to integrate security checks into the CI/CD pipeline.
• Regression Detection: The action is designed to detect and prevent regressions in the OpenSSF Scorecard score by comparing each commit within a pull request against a baseline SHA.
• Commit-by-Commit Analysis: Unlike standard OpenSSF actions, this custom action checks the scorecard score for each commit in the PR's range, failing the workflow if any commit's score drops below the baseline.
• Tooling Setup: The action includes steps to install the OpenSSF Scorecard CLI tool and jq for efficient JSON parsing within the action's execution environment.

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[gemini-code-assist]

Code Review

This pull request introduces a new composite GitHub Action to gate pull requests based on OpenSSF Scorecard regressions. While the implementation is clean, a medium-severity command injection vulnerability was identified in openssf-scorecard/action.yml. The git checkout command uses user-controlled inputs without proper sanitization, which could allow an attacker to pass malicious options. The provided suggestions address this by ensuring user inputs are treated as arguments and also include improvements for readability.

[jeckersb]

Looks sane at a glance, I'm not familiar with any of this but it's low-risk just as a gating action so let's see how it goes!

[jeckersb]

Oh apparently I don't have write access to this repo 😿

[cgwalters]

Oh apparently I don't have write access to this repo 😿

bootc-dev/infra#18 (comment)

Does it work now?

[jeckersb]

Does it work now?

Yep I was able to approve+merge #4 🥳