Summary
The ‘tests_build.yml’ GitHub workflow is vulnerable to arbitrary code execution.
Product
rism-ch/verovio GitHub repository
Tested Version
The latest changeset 4923b8f 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:
branches: develop
...
- name: Checkout the PR
uses: actions/checkout@v2
with:
ref: ${{ github.event.pull_request.head.sha }}
path: ${{ env.PR_DIR }}/
- name: Build Python toolkit and run the tests for the PR
working-directory: ${{ github.workspace }}/${{ env.PR_DIR }}/bindings
run: |
cmake ../cmake -DBUILD_AS_PYTHON=ON -B python
...
Impact
The vulnerability allows for unauthorized modification of the base repository and secrets exfiltration.
Coordinated Disclosure Timeline
- 2020-11-26: Report sent to maintainer
- 2020-11-30: Maintainers acknowledged
- 2020-12-02: Issue resolved
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-2020-248 in any communication regarding this issue.