🛡️ Sentinel: [CRITICAL] Fix Path Validation AttributeError bypass in SafeStaticFiles

.jules/sentinel.md

@@ -1,4 +1,9 @@
 ## 2025-02-21 - Path Traversal in Mix Endpoint API Parameter
 **Vulnerability:** The `/projects/{project_id}/mix` API endpoint in `src/audioformation/server/routes.py` accepted a `music` parameter (meant to specify a filename within the `05_MUSIC/generated` directory) but directly passed it to `mix_project` without sanitization. This allowed directory traversal payloads like `../../../etc/passwd` to be used for background music resolution.
 **Learning:** Even internal API inputs that map strictly to filenames inside an expected directory must be sanitized. A simple check for file existence (`if not bg_music_path.exists():`) is insufficient as it confirms existence but allows looking outside the bounded directory.
-**Prevention:** Always use established sanitization helpers (like `sanitize_filename`) or bound checks (like `validate_path_within`) for any user-supplied string that forms part of a filesystem path. Ensure bypass parameters like `FORCE_NO_MUSIC` are handled before and mutually exclusively from sanitization.
+**Prevention:** Always use established sanitization helpers (like `sanitize_filename`) or bound checks (like `validate_path_within`) for any user-supplied string that forms part of a filesystem path. Ensure bypass parameters like `FORCE_NO_MUSIC` are handled before and mutually exclusively from sanitization.
+
+## 2024-05-24 - [Path Validation Bypass via AttributeError]
+**Vulnerability:** In `src/audioformation/server/app.py`, the `SafeStaticFiles` middleware attempted to normalize paths for security checks using `p = Path(path).lower()`. However, `Path` objects don't have a `.lower()` method, causing an `AttributeError` when a path is processed. This completely bypasses the security check because `SafeStaticFiles` could raise an unhandled exception or fail to block access to sensitive files depending on how the error is handled upstream.
+**Learning:** Security validations that crash or raise exceptions before completing their checks can lead to open failure modes or denial of service. The path normalization must occur on the string *before* conversion to a `Path` object to successfully block restricted directories like `00_config`.
+**Prevention:** Always verify string manipulations are applied to string objects and validate that security checks do not crash and fail open. Convert path strings to lower case before instantiating `Path` objects (e.g. `Path(path.lower())`) to avoid `AttributeError`.

src/audioformation/server/app.py

@@ -24,7 +24,7 @@ class SafeStaticFiles(StaticFiles):
 
     async def get_response(self, path: str, scope) -> Response:
         # Normalize path for check
-        p = Path(path).lower()
+        p = Path(path.lower())
         if "00_config" in p.parts or p.name.startswith(".env") or ".git" in p.parts:
             raise HTTPException(
                 status_code=403, detail="Access denied to sensitive resource"