snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

zerver/upload_handler.py

@@ -0,0 +1,60 @@
+import os
+import tempfile
+
+from django.core.files.uploadhandler import TemporaryFileUploadHandler
+from typing_extensions import override
+
+# Django spools each uploaded file to a temporary file named
+# f"{tempfile.gettempprefix()}{8 random characters}.upload{extension}",
+# where the extension is taken verbatim from the client-provided filename.
+#
+# Since a filename is limited to NAME_MAX (255) bytes, a sufficiently
+# long extension makes creating that temporary file fail with
+# 'OSError: [Errno 36] File name too long', which Django does not handle.
+TEMPORARY_FILE_MAX_EXTENSION_LENGTH = 255 - len(tempfile.gettempprefix()) - 8 - len(".upload")
+
+
+def truncate_filename_extension(filename: str) -> str:
+    """Shortens filename extensions that are too long to fit in the name of
+    the temporary file Django spools an upload to. NAME_MAX limits bytes
+    rather than characters, so we truncate the encoded extension and discard
+    any character left partially encoded at the end.
+    """
+    root, extension = os.path.splitext(filename)
+    encoded_extension = extension.encode()
+    if len(encoded_extension) <= TEMPORARY_FILE_MAX_EXTENSION_LENGTH:
+        return filename
+    return root + encoded_extension[:TEMPORARY_FILE_MAX_EXTENSION_LENGTH].decode(errors="ignore")
+
+
+class ZulipTemporaryFileUploadHandler(TemporaryFileUploadHandler):
+    """Django's TemporaryFileUploadHandler, made tolerant of filenames whose
+    extension alone exceeds what the filesystem allows in a filename.
+
+    Django does sanitize an over-long filename, in UploadedFile._set_name,
+    but only after creating the temporary file whose name embeds the
+    extension; shortening the extension is therefore something we have to do
+    beforehand. The cap is far longer than any extension in practice.
+
+    This workaround can go away once https://code.djangoproject.com/ticket/37292
+    is fixed upstream.
+    """
+
+    @override
+    def new_file(
+        self,
+        field_name: str,
+        file_name: str,
+        content_type: str,
+        content_length: int | None,
+        charset: str | None = None,
+        content_type_extra: dict[str, bytes] | None = None,
+    ) -> None:
+        super().new_file(
+            field_name,
+            truncate_filename_extension(file_name),
+            content_type,
+            content_length,
+            charset,
+            content_type_extra,
+        )