Read config and .codeowners from base ref instead of head

[BakerNet]

Related Issue(s)

closes: #74

Summary / Background

Update docs to use base_ref for actions/checkout to prevent PR authors from removing required reviews in their PR

[pooyaw]

✅ Snyk checks have passed. No issues have been found so far.

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[gemini-code-assist]

Summary of Changes

Hello @BakerNet, 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 enhances the security posture of recommended GitHub Actions workflows by modifying the actions/checkout configuration. The update ensures that the workflow operates on the target branch of a pull request, thereby mitigating a potential vector for pull request authors to circumvent established review processes and maintain the integrity of code merges.

Highlights

• GitHub Actions Workflow Security: The actions/checkout step in the example GitHub Actions workflow has been updated to explicitly use ref: ${{ github.base_ref }}. This change ensures that the workflow checks out the base branch of the pull request, rather than the head branch, to prevent potential bypasses of required reviews by PR authors.

Ignored Files

• Ignored by pattern: .github/workflows/** (1)
  • .github/workflows/codeowners.yml

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[github-actions]

Codeowners approval required for this PR:

• ✅ @zbedforrest

[gemini-code-assist]

Code Review

This pull request updates the documentation to recommend checking out github.base_ref in the example GitHub Actions workflow. The goal is to enhance security by preventing pull request authors from modifying .codeowners files to bypass reviews. While this is a positive change, I've pointed out in a comment that it doesn't fully mitigate the security risk, as the workflow file itself can still be modified by the PR author when using the pull_request trigger. For a more secure setup, I've recommended using the pull_request_target trigger instead.

[gemini-code-assist]

While using ref: ${{ github.base_ref }} is a good step to prevent using potentially malicious .codeowners files from the pull request branch, this setup is still vulnerable. Because the workflow is triggered by pull_request, the workflow file itself is sourced from the pull request branch. A malicious actor could simply remove this ref line in their PR to bypass the protection.

For robust security, you should use the pull_request_target trigger instead of pull_request. Workflows triggered by pull_request_target run using the workflow file from the base branch, which prevents malicious modifications to the workflow itself. When using pull_request_target, actions/checkout defaults to checking out the base ref, making your action secure against this type of bypass.

[BakerNet]

Using pull_request_target is NOT the right answer here. But the issue is worth paying attention to. Will switch to base ref in Codeowners Plus itself