Fix handling of User-Agent headers with bad utf-8.

changelog.d/8632.bugfix

@@ -0,0 +1 @@
+Fix handling of User-Agent headers that are invalid UTF-8, which caused user agents of users to not get correctly recorded.

synapse/api/auth.py

@@ -186,7 +186,7 @@ async def get_user_by_req(
             ip_addr = self.hs.get_ip_from_request(request)
             user_agent = request.requestHeaders.getRawHeaders(
                 b"User-Agent", default=[b""]
-            )[0].decode("ascii", "surrogateescape")
+            )[0].decode("ascii", "replace")
 
             access_token = self.get_access_token_from_request(request)
 

synapse/handlers/auth.py

@@ -472,7 +472,7 @@ async def check_ui_auth(
 
         user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
             0
-        ].decode("ascii", "surrogateescape")
+        ].decode("ascii", "replace")
 
         await self.store.add_user_agent_ip_to_ui_auth_session(
             session.session_id, user_agent, clientip

synapse/handlers/cas_handler.py

@@ -214,7 +214,7 @@ async def handle_ticket(
                 # Pull out the user-agent and IP from the request.
                 user_agent = request.requestHeaders.getRawHeaders(
                     b"User-Agent", default=[b""]
-                )[0].decode("ascii", "surrogateescape")
+                )[0].decode("ascii", "replace")
                 ip_address = self.hs.get_ip_from_request(request)
 
                 registered_user_id = await self._registration_handler.register_user(

synapse/handlers/oidc_handler.py

@@ -697,7 +697,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
         # Pull out the user-agent and IP from the request.
         user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
             0
-        ].decode("ascii", "surrogateescape")
+        ].decode("ascii", "replace")
         ip_address = self.hs.get_ip_from_request(request)
 
         # Call the mapper to register/login the user

synapse/handlers/saml_handler.py

@@ -218,7 +218,7 @@ async def handle_saml_response(self, request: SynapseRequest) -> None:
         # Pull out the user-agent and IP from the request.
         user_agent = request.requestHeaders.getRawHeaders(b"User-Agent", default=[b""])[
             0
-        ].decode("ascii", "surrogateescape")
+        ].decode("ascii", "replace")
         ip_address = self.hs.get_ip_from_request(request)
 
         # Call the mapper to register/login the user