fix: harden the narinfo route pattern [backport #841]

[kalbasit]

Bot-based backport to release-0.8, triggered by a label in #841.

The narinfo hash was updated in #840 to reflect the upstream definition
in NixOS/nix#15004 and so the server should only allow narinfo requests
that match this pattern.

[dosubot]

Related Documentation

Checked 7 published document(s) in 1 knowledge base(s). No updates required.

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[gemini-code-assist]

Summary of Changes

Hello @kalbasit, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request strengthens the narinfo route pattern to enforce a more precise hash format, consistent with upstream Nix specifications. This change improves the robustness of the server's request handling by integrating hash validation directly into the routing mechanism, thereby removing the need for a separate validation step in the handler. The associated test suite has been updated to reflect these enhanced security measures.

Highlights

• Stricter Narinfo Route Pattern: Updated the narinfo route pattern in pkg/server/server.go to use a more stringent narinfo.HashPattern, aligning with upstream Nix definitions for enhanced security and validation.
• Removed Redundant Hash Validation: Eliminated the explicit helper.IsValidHash check within the getNarInfo handler in pkg/server/server.go, as hash validation is now handled directly by the updated route pattern.
• Updated Security Test Cases: Adjusted test cases in pkg/server/security_test.go to reflect the new narinfo hash validation logic, including removing an outdated valid hash test and updating expected status codes for malicious path attempts.

Changelog

• pkg/server/security_test.go
  • Removed a test case for a 52-character narinfo hash that is no longer considered valid under the new pattern.
  • Modified a path traversal test case to expect a StatusNotFound response instead of StatusBadRequest due to the updated routing logic.
• pkg/server/server.go
  • Imported the narinfo package to access the new hash pattern.
  • Updated the routeNarInfo constant to incorporate narinfo.HashPattern for stricter URL routing.
  • Removed the helper.IsValidHash check from the getNarInfo handler, as validation is now performed by the route pattern.

Activity

• This is a bot-based backport to the release-0.8 branch, triggered by a label in pull request fix: harden the narinfo route pattern #841.

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[gemini-code-assist]

Code Review

This pull request hardens the narinfo route pattern to align with the upstream Nix definition, which is a good security and correctness improvement. The route now uses a stricter regular expression to validate the hash format at the routing layer, simplifying the handler logic by removing now-redundant validation. The tests have been updated to reflect these changes. I've identified a minor consistency issue where the validation removal was not applied to all relevant handlers, and I've left a comment with a suggestion to address it.