Check for field name and raise if not found

python_multipart/multipart.py

@@ -1562,7 +1562,7 @@ def __init__(
 
             def on_start() -> None:
                 nonlocal file
-                file = FileClass(file_name, config=cast("FileConfig", self.config))
+                file = FileClass(file_name, b"", config=cast("FileConfig", self.config))
 
             def on_data(data: bytes, start: int, end: int) -> None:
                 nonlocal file
@@ -1692,9 +1692,11 @@ def on_headers_finished() -> None:
                 disp, options = parse_options_header(content_disp)
 
                 # Get the field and filename.
-                field_name = options.get(b"name", b"")
+                field_name = options.get(b"name")
                 file_name = options.get(b"filename")
-                # TODO: check for errors
+                if field_name is None:
+                    raise FormParserError('Field name not found in Content-Disposition: "{!r}"'.format(content_disp))
+                # TODO: check for other errors
 
                 # Create the proper class.
                 content_type_b = headers.get("content-type")

tests/test_multipart.py

@@ -1235,6 +1235,23 @@ def on_file(f: FileProtocol) -> None:
         f.finalize()
         self.assert_file_data(files[0], b"Test")
 
+    def test_bad_content_disposition(self) -> None:
+        # Field name is required.
+        data = (
+            b"----boundary\r\nContent-Disposition: form-data;\r\n"
+            b"Content-Type: text/plain\r\n"
+            b"Test\r\n----boundary--\r\n"
+        )
+
+        on_field = Mock()
+        on_file = Mock()
+
+        f = FormParser("multipart/form-data", on_field, on_file, boundary="--boundary")
+
+        with self.assertRaises(FormParserError):
+            f.write(data)
+            f.finalize()
+
     def test_handles_None_fields(self) -> None:
         fields: list[Field] = []