Description

Resolves #920.

Improves OriginValidationMiddleware (backend/middleware/csrf.py) with fail-closed failure recovery. When origin extraction or validation encounters an unexpected runtime error (e.g. malformed headers or parsing faults), the middleware catches the exception, logs a detailed error traceback, and securely rejects the request with an HTTP 500 JSON response rather than allowing unvalidated requests to proceed or causing unhandled crashes.

Key Changes

• Security Middleware (backend/middleware/csrf.py):

  • Wrapped origin header extraction and validation logic in dispatch() inside a try...except Exception block.
  • Logged errors with logger.error("Failure recovery triggered in security middleware...", exc_info=True).
  • Returned fail-closed JSONResponse({"detail": "Security verification error: middleware failure recovery triggered"}, status_code=500).

• Unit Tests (backend/tests/test_csrf.py):

  • Added test_security_middleware_failure_recovery_on_exception to verify that mutating requests return an HTTP 500 response when header extraction/validation raises an exception.
  • Added test_security_middleware_failure_recovery_safe_methods to verify that safe HTTP methods (GET) bypass origin verification and succeed normally.

• Documentation (docs/csrf-protection.md):

  • Documented failure recovery behavior in the Implementation and Design Decisions sections.

Acceptance Criteria Checklist

• Implement the change in the security middleware (OriginValidationMiddleware).
• Add or update unit tests (test_csrf.py).
• Update documentation (docs/csrf-protection.md).

Verification

Run the test suite:

python -m pytest backend/tests/test_csrf.py -v