Suppress CryptographyDeprecationWarning (#9698)

This warning is somewhat confusing to users, so let's suppress it

changelog.d/9698.misc

@@ -0,0 +1 @@
+Suppress "CryptographyDeprecationWarning: int_from_bytes is deprecated".

synapse/app/_base.py

@@ -21,8 +21,10 @@
 import socket
 import sys
 import traceback
+import warnings
 from typing import Awaitable, Callable, Iterable
 
+from cryptography.utils import CryptographyDeprecationWarning
 from typing_extensions import NoReturn
 
 from twisted.internet import defer, error, reactor
@@ -195,6 +197,25 @@ def listen_metrics(bind_addresses, port):
         start_http_server(port, addr=host, registry=RegistryProxy)
 
 
+def listen_manhole(bind_addresses: Iterable[str], port: int, manhole_globals: dict):
+    # twisted.conch.manhole 21.1.0 uses "int_from_bytes", which produces a confusing
+    # warning. It's fixed by https://github.com/twisted/twisted/pull/1522), so
+    # suppress the warning for now.
+    warnings.filterwarnings(
+        action="ignore",
+        category=CryptographyDeprecationWarning,
+        message="int_from_bytes is deprecated",
+    )
+
+    from synapse.util.manhole import manhole
+
+    listen_tcp(
+        bind_addresses,
+        port,
+        manhole(username="matrix", password="rabbithole", globals=manhole_globals),
+    )
+
+
 def listen_tcp(bind_addresses, port, factory, reactor=reactor, backlog=50):
     """
     Create a TCP socket for a port and several addresses

synapse/app/generic_worker.py

@@ -147,7 +147,6 @@
 from synapse.types import ReadReceipt
 from synapse.util.async_helpers import Linearizer
 from synapse.util.httpresourcetree import create_resource_tree
-from synapse.util.manhole import manhole
 from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger("synapse.app.generic_worker")
@@ -640,12 +639,8 @@ def start_listening(self, listeners: Iterable[ListenerConfig]):
             if listener.type == "http":
                 self._listen_http(listener)
             elif listener.type == "manhole":
-                _base.listen_tcp(
-                    listener.bind_addresses,
-                    listener.port,
-                    manhole(
-                        username="matrix", password="rabbithole", globals={"hs": self}
-                    ),
+                _base.listen_manhole(
+                    listener.bind_addresses, listener.port, manhole_globals={"hs": self}
                 )
             elif listener.type == "metrics":
                 if not self.get_config().enable_metrics:

synapse/app/homeserver.py

@@ -67,7 +67,6 @@
 from synapse.storage.engines import IncorrectDatabaseSetup
 from synapse.storage.prepare_database import UpgradeDatabaseException
 from synapse.util.httpresourcetree import create_resource_tree
-from synapse.util.manhole import manhole
 from synapse.util.module_loader import load_module
 from synapse.util.versionstring import get_version_string
 
@@ -288,12 +287,8 @@ def start_listening(self, listeners: Iterable[ListenerConfig]):
             if listener.type == "http":
                 self._listening_services.extend(self._listener_http(config, listener))
             elif listener.type == "manhole":
-                listen_tcp(
-                    listener.bind_addresses,
-                    listener.port,
-                    manhole(
-                        username="matrix", password="rabbithole", globals={"hs": self}
-                    ),
+                _base.listen_manhole(
+                    listener.bind_addresses, listener.port, manhole_globals={"hs": self}
                 )
             elif listener.type == "replication":
                 services = listen_tcp(