Impact

The CodeQL runner tool, provided to run CodeQL-based code scanning on non-GitHub CI/CD systems, requires a GitHub access token to connect to a GitHub repository.

The runner and its documentation previously suggested passing the GitHub token as a command-line parameter to the process instead of reading it from a file, standard input, or an environment variable. For example:

/path/to-runner/codeql-runner-linux <command> <args> --github-auth TOKEN

This approach made the token visible to other processes on the same machine, for example in the output of the ps command.
If the CI system publicly exposes the output of ps, for example by logging the output, then the GitHub access token can be exposed beyond the scope intended.

Users of the CodeQL runner on 3rd-party systems, who are passing a GitHub token via the --github-auth flag, are affected. This applies to both GitHub.com and GitHub Enterprise users.
Users of the CodeQL Action on GitHub Actions are not affected.

Mitigation / new behavior

The --github-auth flag is now considered insecure and deprecated. The undocumented --external-repository-token flag has been removed. To securely provide a GitHub access token to the CodeQL runner, users should do one of the following instead:

• Use the --github-auth-stdin flag and pass the token on the command line via standard input:

  echo "$TOKEN" | /path/to-runner/codeql-runner-linux <command> <args> --github-auth-stdin
  

• Set the GITHUB_TOKEN environment variable to contain the token, then call the command without passing in the token:

  # set GITHUB_TOKEN to the token, using your CI system's secret storage mechanism
  /path/to-runner/codeql-runner-linux <command> <args>
  

The old flag remains present for backwards compatibility with existing workflows. If the user tries to specify an access token using the --github-auth flag, there is a deprecation warning printed to the terminal that directs the user to one of the above options.

For more information, see the GitHub documentation pages linked below.

Patches

All CodeQL runner releases from https://github.com/github/codeql-action/releases/tag/codeql-bundle-20210304 onwards contain the patches:

• 88714e3 deprecates the --github-auth flag
• 58defc0 removes the --external-repository-token flag

Workarounds

• We recommend updating to a recent version of the CodeQL runner, storing a token in your CI system's secret storage mechanism, and passing the token to the CodeQL runner using --github-auth-stdin or the GITHUB_TOKEN environment variable.
• If still using the old flag, ensure that process output, such as from ps, is not persisted in CI logs.

References

• GitHub documentation
  • https://docs.github.com/en/code-security/secure-coding/using-codeql-code-scanning-with-your-existing-ci-system/running-codeql-runner-in-your-ci-system
  • https://docs.github.com/en/code-security/secure-coding/using-codeql-code-scanning-with-your-existing-ci-system/configuring-codeql-runner-in-your-ci-system#init
• https://cwe.mitre.org/data/definitions/214.html
• https://www.netmeister.org/blog/passing-passwords.html

For more information

If you have any questions or comments about this advisory:

• Open an issue
• Contact us as described in the security policy

Credit

Thanks to @jlleitschuh for reporting this vulnerability through our Bug Bounty program.