Hydra missing authentication when triggering evaluations through GitHub and Gitea plugins

Vulnerability Description

Hydra is a continuous integration service for Nix based projects. Prior to commit f7bda02, /api/push-github and /api/push-gitea are called by the corresponding forge without HTTP Basic authentication. Both forges do however feature HMAC signing with a secret key. Triggering an evaluation can be very taxing on the infrastructure when large evaluations are done, introducing potential denial of service attacks on the host running the evaluator. This issue has been patched by commit f7bda02. A workaround involves blocking /api/push-github and /api/push-gitea via a reverse proxy.

References

• https://github.com/NixOS/hydra/security/advisories/GHSA-qpq3-646c-vgx9
• https://github.com/NixOS/hydra/commit/f7bda020c6144913f134ec616783e57817f7686f