Add an option to avoid checking claimed mimetype

src/matrix_content_scanner/config.py

@@ -83,6 +83,7 @@ def _parse_size(size: Optional[Union[str, float]]) -> Optional[float]:
                 "script": {"type": "string"},
                 "temp_directory": {"type": "string"},
                 "removal_command": {"type": "string"},
+                "check_claimed_mimetype": {"type": "boolean"},
                 "allowed_mimetypes": {"type": "array", "items": {"type": "string"}},
             },
         },
@@ -139,6 +140,7 @@ class ScanConfig:
     script: str
     temp_directory: str
     removal_command: str = "rm"
+    check_claimed_mimetype: bool = True
     allowed_mimetypes: Optional[List[str]] = None
 
 

src/matrix_content_scanner/scanner/scanner.py

@@ -82,6 +82,8 @@ def __init__(self, mcs: "MatrixContentScanner"):
 
         self._max_size_to_cache = mcs.config.result_cache.max_file_size
 
+        self._check_claimed_mimetype = mcs.config.scan.check_claimed_mimetype
+
         # List of MIME types we should allow. If None, we don't fail files based on their
         # MIME types (besides comparing it with the Content-Type header from the server
         # for unencrypted files).
@@ -526,7 +528,7 @@ def _check_mimetype(
         # Check if the MIME type is matching the one that's expected, but only if the file
         # is not encrypted (because otherwise we'll always have 'application/octet-stream'
         # in the Content-Type header regardless of the actual MIME type of the file).
-        if encrypted is False and detected_mimetype != claimed_mimetype:
+        if self._check_claimed_mimetype and encrypted is False and detected_mimetype != claimed_mimetype:
             logger.error(
                 "Mismatching MIME type (%s) and Content-Type header (%s)",
                 detected_mimetype,