From c2bdf040aa93f3b542d1b0e2f6ce57853630ec6f Mon Sep 17 00:00:00 2001
From: Will Hunt <will@half-shot.uk>
Date: Tue, 29 Sep 2020 17:15:27 +0100
Subject: [PATCH] Discard an empty upload_name before persisting an uploaded
 file (#7905)

---
 changelog.d/7905.bugfix                   | 1 +
 synapse/rest/media/v1/media_repository.py | 7 ++++---
 synapse/rest/media/v1/upload_resource.py  | 4 ++++
 3 files changed, 9 insertions(+), 3 deletions(-)
 create mode 100644 changelog.d/7905.bugfix

diff --git a/changelog.d/7905.bugfix b/changelog.d/7905.bugfix
new file mode 100644
index 000000000000..e60e62441210
--- /dev/null
+++ b/changelog.d/7905.bugfix
@@ -0,0 +1 @@
+Fix a longstanding bug when storing a media file with an empty `upload_name`.
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 69f353d46f9e..ae6822d6e742 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -139,7 +139,7 @@ def mark_recently_accessed(self, server_name, media_id):
     async def create_content(
         self,
         media_type: str,
-        upload_name: str,
+        upload_name: Optional[str],
         content: IO,
         content_length: int,
         auth_user: str,
@@ -147,8 +147,8 @@ async def create_content(
         """Store uploaded content for a local user and return the mxc URL
 
         Args:
-            media_type: The content type of the file
-            upload_name: The name of the file
+            media_type: The content type of the file.
+            upload_name: The name of the file, if provided.
             content: A file like object that is the content to store
             content_length: The length of the content
             auth_user: The user_id of the uploader
@@ -156,6 +156,7 @@ async def create_content(
         Returns:
             The mxc url of the stored content
         """
+
         media_id = random_string(24)
 
         file_info = FileInfo(server_name=None, file_id=media_id)
diff --git a/synapse/rest/media/v1/upload_resource.py b/synapse/rest/media/v1/upload_resource.py
index 3ebf7a68e673..d76f7389e101 100644
--- a/synapse/rest/media/v1/upload_resource.py
+++ b/synapse/rest/media/v1/upload_resource.py
@@ -63,6 +63,10 @@ async def _async_render_POST(self, request):
                     msg="Invalid UTF-8 filename parameter: %r" % (upload_name), code=400
                 )
 
+        # If the name is falsey (e.g. an empty byte string) ensure it is None.
+        else:
+            upload_name = None
+
         headers = request.requestHeaders
 
         if headers.hasHeader(b"Content-Type"):