Coordinated Disclosure Timeline
- 2020-12-21: Report sent to maintainers.
- 2020-12-22: Maintainers acknowledged.
- 2020-12-22: Issue resolved.
Summary
The pull_request.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Product
android-password-store/Android-Password-Store GitHub repository
Tested Version
The latest changeset 67393ef 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]
...
- name: Checkout code (pull_request)
if: github.event_name == 'pull_request' || github.event_name == 'pull_request_target'
uses: actions/checkout@v2
with:
ref: 'refs/pull/${{ github.event.number }}/merge'
...
- name: Checkout repository
if: ${{ steps.service-changed.outputs.result == 'true' }}
uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f
with:
ref: refs/pull/${{ github.event.pull_request.number }}/merge
...
- name: Run unit tests
if: ${{ steps.service-changed.outputs.result == 'true' }}
uses: burrunan/gradle-cache-action@03c71a8ba93d670980695505f48f49daf43704a6
with:
arguments: apiCheck testFreeDebug lintFreeDebug
...
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-2020-367 in any communication regarding this issue.