February 3, 2021

GHSL-2020-275: Arbitrary code execution in LedgerHQ/ledger-live-desktop workflow

Jaroslav Lobačevski

Coordinated Disclosure Timeline

  • 2020-11-30: Report sent to maintainers.
  • 2020-11-30: Maintainers acknowledged.
  • 2021-01-21: 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

LedgerHQ/ledger-live-desktop GitHub repository

Tested Version

The latest changeset a9f67b7 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:
      - "*"
...
        with:
          ref: ${{ github.event.pull_request.head.sha }}
          repository: ${{github.event.pull_request.head.repo.full_name}}
...
      - name: install dependencies
        run: yarn --frozen-lockfile
      - name: run code checks
        run: yarn ci 2>lint.txt
...

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-2020-275 in any communication regarding this issue.