🛡️ Sentinel: [HIGH] hmac.compare_digest Non-ASCII DoS 취약점 수정

.jules/sentinel.md

@@ -65,3 +65,7 @@
 **Vulnerability:** Path traversal in `media_shrinker.py` via unresolved `..` segments or symlink escapes before deriving conversion output paths.
 **Learning:** `Path.relative_to()` is only a lexical containment check unless both the source and root have first been resolved into canonical absolute paths. Relative paths and symlinks can otherwise bypass root-boundary assumptions.
 **Prevention:** Resolve both source and root once, reject sources outside the resolved root with a sanitized `MediaShrinkerError`, and derive `rel_source` from the resolved paths before planning outputs.
+## 2024-05-24 - hmac.compare_digest Non-ASCII DoS
+**Vulnerability:** `hmac.compare_digest()` crashes with a `TypeError` when comparing strings containing non-ASCII characters. Since `x-api-key` is user input, this causes an unhandled exception and a Denial of Service.
+**Learning:** Python's `hmac.compare_digest` does not support non-ASCII string comparisons.
+**Prevention:** Always encode user-controlled input and secrets to bytes (`.encode('utf-8')`) before using `hmac.compare_digest`.

saas_web.py

@@ -113,8 +113,9 @@ async def require_api_key(request: Request, call_next):
     configured_keys = get_configured_api_keys()
     if configured_keys and not (request.method == "GET" and request.url.path == "/"):
         provided_key = request.headers.get("x-api-key", "")
+        provided_key_bytes = provided_key.encode('utf-8')
         if not any(
-            hmac.compare_digest(provided_key, key) for key in configured_keys
+            hmac.compare_digest(provided_key_bytes, key.encode('utf-8')) for key in configured_keys
         ):
             return JSONResponse(
                 status_code=401,

tests/test_saas_web.py

@@ -707,6 +707,29 @@ def test_missing_header_rejected_when_keys_configured(self):
         self.assertEqual(response.json(), {"error": "Invalid or missing API key"})
         self.assertNotIn("secret-key", response.text)
 
+    @patch("saas_web.JSONResponse")
+    def test_non_ascii_key_does_not_crash(self, mock_json_response):
+        # httpx TestClient forbids non-ascii headers entirely; test middleware directly.
+        from starlette.requests import Request
+        import asyncio
+
+        with patch.dict(os.environ, {"CODEC_CARVER_API_KEYS": "secret-key"}):
+            scope = {
+                "type": "http",
+                "method": "POST",
+                "path": "/shrink",
+                "headers": [(b"x-api-key", "에스".encode("utf-8"))],
+            }
+            request = Request(scope)
+
+            async def mock_call_next(req):
+                return "SUCCESS"
+
+            mock_json_response.return_value = "REJECTED"
+
+            result = asyncio.run(saas_web.require_api_key(request, mock_call_next))
+            self.assertEqual(result, "REJECTED")
+
     def test_wrong_key_rejected(self):
         with patch.dict(os.environ, {"CODEC_CARVER_API_KEYS": "secret-key"}):
             response = self._post_shrink(headers={"X-API-Key": "wrong-key"})