From 6a080ea184844f6ee9412a8d6170eb7ff2e5dd56 Mon Sep 17 00:00:00 2001
From: Patrick Cloke <clokep@users.noreply.github.com>
Date: Fri, 24 Jul 2020 07:08:07 -0400
Subject: [PATCH] Return an empty body for OPTIONS requests. (#7886)

---
 changelog.d/7886.misc  |  1 +
 synapse/http/server.py | 24 +++++-------------------
 tests/test_server.py   | 12 ++++++------
 3 files changed, 12 insertions(+), 25 deletions(-)
 create mode 100644 changelog.d/7886.misc

diff --git a/changelog.d/7886.misc b/changelog.d/7886.misc
new file mode 100644
index 0000000000..e729ab2451
--- /dev/null
+++ b/changelog.d/7886.misc
@@ -0,0 +1 @@
+Return an empty body for OPTIONS requests.
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 8e003689c4..d4f9ad6e67 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -442,21 +442,6 @@ class StaticResource(File):
         return super().render_GET(request)
 
 
-def _options_handler(request):
-    """Request handler for OPTIONS requests
-
-    This is a request handler suitable for return from
-    _get_handler_for_request. It returns a 200 and an empty body.
-
-    Args:
-        request (twisted.web.http.Request):
-
-    Returns:
-        Tuple[int, dict]: http code, response body.
-    """
-    return 200, {}
-
-
 def _unrecognised_request_handler(request):
     """Request handler for unrecognised requests
 
@@ -490,11 +475,12 @@ class OptionsResource(resource.Resource):
     """Responds to OPTION requests for itself and all children."""
 
     def render_OPTIONS(self, request):
-        code, response_json_object = _options_handler(request)
+        request.setResponseCode(204)
+        request.setHeader(b"Content-Length", b"0")
 
-        return respond_with_json(
-            request, code, response_json_object, send_cors=True, canonical_json=False,
-        )
+        set_cors_headers(request)
+
+        return b""
 
     def getChildWithDefault(self, path, request):
         if request.method == b"OPTIONS":
diff --git a/tests/test_server.py b/tests/test_server.py
index 42cada8964..073b2362cc 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -193,10 +193,10 @@ class OptionsResourceTests(unittest.TestCase):
         return channel
 
     def test_unknown_options_request(self):
-        """An OPTIONS requests to an unknown URL still returns 200 OK."""
+        """An OPTIONS requests to an unknown URL still returns 204 No Content."""
         channel = self._make_request(b"OPTIONS", b"/foo/")
-        self.assertEqual(channel.result["code"], b"200")
-        self.assertEqual(channel.result["body"], b"{}")
+        self.assertEqual(channel.result["code"], b"204")
+        self.assertNotIn("body", channel.result)
 
         # Ensure the correct CORS headers have been added
         self.assertTrue(
@@ -213,10 +213,10 @@ class OptionsResourceTests(unittest.TestCase):
         )
 
     def test_known_options_request(self):
-        """An OPTIONS requests to an known URL still returns 200 OK."""
+        """An OPTIONS requests to an known URL still returns 204 No Content."""
         channel = self._make_request(b"OPTIONS", b"/res/")
-        self.assertEqual(channel.result["code"], b"200")
-        self.assertEqual(channel.result["body"], b"{}")
+        self.assertEqual(channel.result["code"], b"204")
+        self.assertNotIn("body", channel.result)
 
         # Ensure the correct CORS headers have been added
         self.assertTrue(