Don't forget to ratelimit calls outside of RegistrationHandler

synapse/handlers/register.py

@@ -168,7 +168,7 @@ class RegistrationHandler(BaseHandler):
         Raises:
             RegistrationError if there was a problem registering.
         """
-        yield self._check_registration_ratelimit(address)
+        yield self.check_registration_ratelimit(address)
 
         yield self.auth.check_auth_blocking(threepid=threepid)
         password_hash = None
@@ -415,7 +415,7 @@ class RegistrationHandler(BaseHandler):
             ratelimit=False,
         )
 
-    def _check_registration_ratelimit(self, address):
+    def check_registration_ratelimit(self, address):
         """A simple helper method to check whether the registration rate limit has been hit
         for a given IP address
 

synapse/replication/http/register.py

@@ -75,6 +75,8 @@ class ReplicationRegisterServlet(ReplicationEndpoint):
     async def _handle_request(self, request, user_id):
         content = parse_json_object_from_request(request)
 
+        await self.registration_handler.check_registration_ratelimit(content["address"])
+
         await self.registration_handler.register_with_store(
             user_id=user_id,
             password_hash=content["password_hash"],