Factor out an `is_mine_server_name` method (#15542)

Add an `is_mine_server_name` method, similar to `is_mine_id`.

Ideally we would use this consistently, instead of sometimes comparing
against `hs.hostname` and other times reaching into
`hs.config.server.server_name`.

Also fix a bug in the tests where `hs.hostname` would sometimes differ
from `hs.config.server.server_name`.

Signed-off-by: Sean Quah <seanq@matrix.org>

2 files changed, 6 insertions, 3 deletions

diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index bc70b94f68..d2fa9976da 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -58,9 +58,9 @@ class TransportLayerClient:
     """Sends federation HTTP requests to other servers"""
 
     def __init__(self, hs: "HomeServer"):
-        self.server_name = hs.hostname
         self.client = hs.get_federation_http_client()
         self._faster_joins_enabled = hs.config.experimental.faster_joins_enabled
+        self._is_mine_server_name = hs.is_mine_server_name
 
     async def get_room_state_ids(
         self, destination: str, room_id: str, event_id: str
@@ -235,7 +235,7 @@ class TransportLayerClient:
             transaction.transaction_id,
         )
 
-        if transaction.destination == self.server_name:
+        if self._is_mine_server_name(transaction.destination):
             raise RuntimeError("Transport layer cannot send to itself!")
 
         # FIXME: This is only used by the tests. The actual json sent is
diff --git a/synapse/federation/transport/server/_base.py b/synapse/federation/transport/server/_base.py
index cdaf0d5de7..b6e9c58760 100644
--- a/synapse/federation/transport/server/_base.py
+++ b/synapse/federation/transport/server/_base.py
@@ -57,6 +57,7 @@ class Authenticator:
         self._clock = hs.get_clock()
         self.keyring = hs.get_keyring()
         self.server_name = hs.hostname
+        self._is_mine_server_name = hs.is_mine_server_name
         self.store = hs.get_datastores().main
         self.federation_domain_whitelist = (
             hs.config.federation.federation_domain_whitelist
@@ -100,7 +101,9 @@ class Authenticator:
                 json_request["signatures"].setdefault(origin, {})[key] = sig
 
                 # if the origin_server sent a destination along it needs to match our own server_name
-                if destination is not None and destination != self.server_name:
+                if destination is not None and not self._is_mine_server_name(
+                    destination
+                ):
                     raise AuthenticationError(
                         HTTPStatus.UNAUTHORIZED,
                         "Destination mismatch in auth header",