🛡️ Sentinel: [CRITICAL] Fix path traversal vulnerability in file utilities

🚨 Severity: CRITICAL
💡 Vulnerability: The generic file hashing utility `app/utils/file_operations.py:hash_file` was vulnerable to path traversal. An attacker controlling the `filepath` argument could read arbitrary files on the system by passing relative paths like `../../../etc/passwd` or providing absolute paths directly.
🎯 Impact: This could lead to Arbitrary File Read and potential information disclosure.
🔧 Fix: Used `pathlib.Path.resolve()` to resolve both the target file path and the allowed base directory (`settings.workdir`). Added a strict check to ensure the resolved target path is strictly within the allowed boundary using `filepath_obj.relative_to(workdir_obj)`, catching the `ValueError` raised when the path is out of bounds. This safely blocks both relative traversal attacks and arbitrary absolute paths, without breaking legitimate relative application paths.
✅ Verification: Ran the test suite `pytest tests/test_path_traversal_security.py -v` successfully, which explicitly checks for `FileNotFoundError` upon traversal attempts.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

.jules/sentinel.md

@@ -1,4 +1,4 @@
-## 2024-05-24 - SSRF in WebDAV connection test
-**Vulnerability:** The `_test_webdav_connection` function had a custom SSRF check that failed to resolve DNS names, allowing attackers to bypass the check by providing a domain that resolves to an internal IP (e.g., `127.0.0.1`).
-**Learning:** DNS resolution is required for robust SSRF protection when validating URLs provided by users.
-**Prevention:** Use a centralized `is_private_ip` function (now in `app/utils/network.py`) that resolves the hostname to its IPs and checks if any are private.
+## 2026-03-20 - Safe Path Traversal Prevention in Low-Level Utilities
+**Vulnerability:** The generic file utility `hash_file` in `app/utils/file_operations.py` accepted any file path and was vulnerable to reading arbitrary files via path traversal (e.g., `../../../etc/passwd`) or absolute paths if an attacker could control the `filepath` argument.
+**Learning:** Naively checking for `".." in path` breaks legitimate relative paths used internally by the application. Blocking absolute paths entirely also breaks functionality. Input validation should occur at the API boundary, but for defense-in-depth, low-level utilities must enforce expected boundaries (e.g., the application's `workdir`).
+**Prevention:** Use `pathlib.Path.resolve()` on both the target path and the allowed base directory (`settings.workdir`). Ensure the resolved target path is strictly within the allowed boundary using `filepath_obj.relative_to(workdir_obj)`, catching the `ValueError` that is raised when the path is out of bounds. This safely blocks both relative traversal attacks and arbitrary absolute paths.

app/utils/file_operations.py

@@ -7,8 +7,19 @@ def hash_file(filepath: str | Path, chunk_size: int = 65536) -> str:
     Returns the SHA-256 hash of the file at 'filepath'.
     Reads the file in chunks to handle large files efficiently.
     """
+    from app.config import settings
+
+    filepath_obj = Path(filepath).resolve()
+    workdir_obj = Path(settings.workdir).resolve()
+
+    # Security check: Ensure the resolved path is strictly within the allowed workdir
+    try:
+        filepath_obj.relative_to(workdir_obj)
+    except ValueError:
+        raise FileNotFoundError(f"Access denied: path traversal attempt or file outside workdir '{filepath}'")
+
     sha256 = hashlib.sha256()
-    with open(filepath, "rb") as f:
+    with open(filepath_obj, "rb") as f:
         while True:
             data = f.read(chunk_size)
             if not data: