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April 2, 2021

GHSL-2020-372: Unauthorized repository modification or secrets exfiltration in GitHub workflows of 418sec/huntr

Jaroslav Lobacevski

Coordinated Disclosure Timeline

Summary

The process-disclosure.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.

Product

418sec/huntr GitHub repository

Tested Version

The latest changeset be289b1 to the date.

Details

Issue: Untrusted code is explicitly checked out and run on a Pull Request from a fork

Workflows triggered on pull_request_target have read/write tokens for the base repository and the access to secrets. By explicitly checking out and running the build script from a fork, the untrusted code is running in an environment that is able to push to the base repository and to access secrets. More details can be found in the article Keeping your GitHub Actions and workflows secure: Preventing pwn requests.

on:
  - pull_request_target
...
      - id: checkout
        uses: actions/checkout@v2
        with:
          fetch-depth: 0
          ref: refs/pull/${{ github.event.number }}/merge
...
      - id: dependency-install
        name: Install npm dependencies
        run: npm ci
      - id: generate-diff
        name: Generate the diff
        env:
          PR_NUMBER: ${{ github.event.pull_request.number }}
          GITHUB_TOKEN: ${{ secrets.HUNTR_HELPER_TOKEN }}
        run: node ./generate-diff.js
...

Impact

The vulnerability allows for unauthorized modification of the base repository and secrets exfiltration.

Credit

This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).

Contact

You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2020-372 in any communication regarding this issue.