Apply the federation_ip_range_blacklist to well-known look-ups.

These protections were already being applied due to the use of
IPBlacklistingResolver, but making it explicit should help ensure
there are fewer avenues for holes.

synapse/http/federation/matrix_federation_agent.py

@@ -16,7 +16,7 @@ import logging
 import urllib.parse
 from typing import List, Optional
 
-from netaddr import AddrFormatError, IPAddress
+from netaddr import AddrFormatError, IPAddress, IPSet
 from zope.interface import implementer
 
 from twisted.internet import defer
@@ -31,6 +31,7 @@ from twisted.web.http_headers import Headers
 from twisted.web.iweb import IAgent, IAgentEndpointFactory, IBodyProducer
 
 from synapse.crypto.context_factory import FederationPolicyForHTTPS
+from synapse.http.client import BlacklistingAgentWrapper
 from synapse.http.federation.srv_resolver import Server, SrvResolver
 from synapse.http.federation.well_known_resolver import WellKnownResolver
 from synapse.logging.context import make_deferred_yieldable, run_in_background
@@ -70,6 +71,7 @@ class MatrixFederationAgent:
         reactor: IReactorCore,
         tls_client_options_factory: Optional[FederationPolicyForHTTPS],
         user_agent: bytes,
+        ip_blacklist: IPSet,
         _srv_resolver: Optional[SrvResolver] = None,
         _well_known_resolver: Optional[WellKnownResolver] = None,
     ):
@@ -90,12 +92,18 @@ class MatrixFederationAgent:
         self.user_agent = user_agent
 
         if _well_known_resolver is None:
+            # Note that the name resolver has already been wrapped in a
+            # IPBlacklistingResolver by MatrixFederationHttpClient.
             _well_known_resolver = WellKnownResolver(
                 self._reactor,
-                agent=Agent(
+                agent=BlacklistingAgentWrapper(
+                    Agent(
+                        self._reactor,
+                        pool=self._pool,
+                        contextFactory=tls_client_options_factory,
+                    ),
                     self._reactor,
-                    pool=self._pool,
-                    contextFactory=tls_client_options_factory,
+                    ip_blacklist=ip_blacklist,
                 ),
                 user_agent=self.user_agent,
             )

synapse/http/matrixfederationclient.py

@@ -245,7 +245,10 @@ class MatrixFederationHttpClient:
         user_agent = user_agent.encode("ascii")
 
         self.agent = MatrixFederationAgent(
-            self.reactor, tls_client_options_factory, user_agent
+            self.reactor,
+            tls_client_options_factory,
+            user_agent,
+            hs.config.federation_ip_range_blacklist,
         )
 
         # Use a BlacklistingAgentWrapper to prevent circumventing the IP

tests/http/federation/test_matrix_federation_agent.py

@@ -17,6 +17,7 @@ import logging
 from mock import Mock
 
 import treq
+from netaddr import IPSet
 from service_identity import VerificationError
 from zope.interface import implementer
 
@@ -103,6 +104,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
             reactor=self.reactor,
             tls_client_options_factory=self.tls_factory,
             user_agent="test-agent",  # Note that this is unused since _well_known_resolver is provided.
+            ip_blacklist=IPSet(),
             _srv_resolver=self.mock_resolver,
             _well_known_resolver=self.well_known_resolver,
         )
@@ -736,6 +738,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
             reactor=self.reactor,
             tls_client_options_factory=tls_factory,
             user_agent=b"test-agent",  # This is unused since _well_known_resolver is passed below.
+            ip_blacklist=IPSet(),
             _srv_resolver=self.mock_resolver,
             _well_known_resolver=WellKnownResolver(
                 self.reactor,