GHSL-2020-269: Unauthorized repository modification or secrets exfiltration in a GitHub workflow of alibaba/hooks
2021-03-03 23:00:00 Author: securitylab.github.com(查看原文) 阅读量:131 收藏

Coordinated Disclosure Timeline

  • 2020-11-30-2020-12-01: Report sent to various maintainers.
  • 2020-12-05: No reply. Created public issue asking for security contact.
  • 2020-12-06: Report sent to the provided contact.
  • 2020-12-07: Report acknowledged.
  • 2020-12-16: Issue resolved.

Summary

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

Product

alibaba/hooks GitHub repository

Tested Version

The latest changeset b0b1c8a to the date.

Details

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

pull_request_target was introduced to allow triggered workflows to comment on PRs, label them, assign people, etc.. In order to make it possible the triggered action runner has read/write token for the base repository and the access to secrets. In order to prevent untrusted code from execution it runs in a context of the base repository.

By explicitly checking out and running 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.

on: pull_request_target
...
    steps:
      - uses: actions/checkout@v2
        with:
          ref: refs/pull/${{ github.event.pull_request.number }}/merge
      - uses: afc163/surge-preview@v1
        with:
          surge_token: ${{ secrets.SURGE_TOKEN }}
          github_token: ${{ secrets.GITHUB_TOKEN }}
          build: |
            npm run init
            npm run build:doc
          dist: dist

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 [email protected], please include a reference to GHSL-2020-269 in any communication regarding this issue.


文章来源: https://securitylab.github.com/advisories/GHSL-2020-269-alibaba-hooks-workflow
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