GHSA-hw6r-g8gj-2987

The pytorch/pytorch filter-test-configs workflow is vulnerable to an expression injection in Actions, allowing an attacker to potentially leak secrets and alter the repository using the workflow.

Details

The filter-test-configs workflow is using the raw github.event.workflow_run.head_branch value inside the filter step:

- name: Select all requested test configurations
  shell: bash
  env:
    GITHUB_TOKEN: ${{ inputs.github-token }}
    JOB_NAME: ${{ steps.get-job-name.outputs.job-name }}
  id: filter
  run: |
    ...
    python3 "${GITHUB_ACTION_PATH}/../../scripts/filter_test_configs.py" \
      ...
      --branch "${{ github.event.workflow_run.head_branch }}"

In the event of a repository using filter-test-configs in a pull_request_target-triggered workflow, an attacker could use a malicious branch name to gain command execution in the step and potentially leak secrets.

name: Example

on: pull_request_target

jobs:
  example:
    runs-on: ubuntu-latest
    steps:
      - name: Filter
        uses: pytorch/pytorch/.github/actions/filter-test-configs@v2

Impact

This issue may lead to stealing workflow secrets.

Remediation

1. Use an intermediate environment variable for potentially attacker-controlled values such as github.event.workflow_run.head_branch:

- name: Select all requested test configurations
  shell: bash
  env:
    GITHUB_TOKEN: ${{ inputs.github-token }}
    JOB_NAME: ${{ steps.get-job-name.outputs.job-name }}
    HEAD_BRANCH: ${{ github.event.workflow_run.head_branch }}
  id: filter
  run: |
    ...
    python3 "${GITHUB_ACTION_PATH}/../../scripts/filter_test_configs.py" \
      ...
      --branch "$HEAD_BRANCH"

Resources

• CodeQL for JavaScript - Expression injection in Actions
• Keeping your GitHub Actions and workflows secure Part 2: Untrusted input
• Keeping your GitHub Actions and workflows secure Part 1: Preventing pwn requests