Add redis SSL configuration options (#15312)

* Add SSL options to redis config

* fix lint issues

* Add documentation and changelog file

* add missing . at the end of the changelog

* Move client context factory to new file

* Rename ssl to tls and fix typo

* fix lint issues

* Added when redis attributes were added

1 files changed, 22 insertions, 7 deletions

diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py

index 2290b3e6fe..233ad61d49 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -46,6 +46,7 @@ from synapse.replication.tcp.commands import (
     UserIpCommand,
     UserSyncCommand,
 )
+from synapse.replication.tcp.context import ClientContextFactory
 from synapse.replication.tcp.protocol import IReplicationConnection
 from synapse.replication.tcp.streams import (
     STREAMS_MAP,
@@ -348,13 +349,27 @@ class ReplicationCommandHandler:
             outbound_redis_connection,
             channel_names=self._channels_to_subscribe_to,
         )
-        hs.get_reactor().connectTCP(
-            hs.config.redis.redis_host,
-            hs.config.redis.redis_port,
-            self._factory,
-            timeout=30,
-            bindAddress=None,
-        )
+
+        reactor = hs.get_reactor()
+        redis_config = hs.config.redis
+        if hs.config.redis.redis_use_tls:
+            ssl_context_factory = ClientContextFactory(hs.config.redis)
+            reactor.connectSSL(
+                redis_config.redis_host,
+                redis_config.redis_port,
+                self._factory,
+                ssl_context_factory,
+                timeout=30,
+                bindAddress=None,
+            )
+        else:
+            reactor.connectTCP(
+                redis_config.redis_host,
+                redis_config.redis_port,
+                self._factory,
+                timeout=30,
+                bindAddress=None,
+            )
 
     def get_streams(self) -> Dict[str, Stream]:
         """Get a map from stream name to all streams."""