Coordinated Disclosure Timeline
- 2020-12-11-2020-12-11: Report sent to various maintainers.
- 2020-12-21: Maintainers acknowledged.
- 2021-01-06: Issue resolved.
Summary
The ci.yml GitHub workflow is vulnerable to unauthorized modification of the base repository or secrets exfiltration from a Pull Request.
Product
dmlc/gluon-cv GitHub repository
Tested Version
The latest changeset 1e8efef 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:
push:
branches:
- master
pull_request_target:
...
- name: Checkout repository(For push)
if: ${{ github.event_name == 'push' }}
uses: actions/checkout@v2
- name: Checkout Pull Request Repository(For pull request)
if: ${{ github.event_name == 'pull_request' || github.event_name == 'pull_request_target' }}
uses: actions/checkout@v2
with:
repository: ${{ github.event.pull_request.head.repo.full_name }}
ref: ${{ github.event.pull_request.head.ref }}
...
- name: sanity-check
shell: bash -l {0}
run: |
conda env create -n gluon_cv_lint -f ./tests/pylint.yml
conda env update -n gluon-cv-lint -f ./tests/pylint.yml --prune
conda activate gluon-cv-lint
conda list
make clean
make pylint
...
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-2020-327 in any communication regarding this issue.