Stop hardcoding trust of old matrix.org key (#5374)

There are a few changes going on here:

* We make checking the signature on a key server response optional: if no
  verify_keys are specified, we trust to TLS to validate the connection.

* We change the default config so that it does not require responses to be
  signed by the old key.

* We replace the old 'perspectives' config with 'trusted_key_servers', which
  is also formatted slightly differently.

* We emit a warning to the logs every time we trust a key server response
  signed by the old key.

2 files changed, 29 insertions, 15 deletions

diff --git a/tests/crypto/test_keyring.py b/tests/crypto/test_keyring.py
index 18121f4f6c..4b1901ce31 100644
--- a/tests/crypto/test_keyring.py
+++ b/tests/crypto/test_keyring.py
@@ -19,7 +19,7 @@ from mock import Mock
 import canonicaljson
 import signedjson.key
 import signedjson.sign
-from signedjson.key import get_verify_key
+from signedjson.key import encode_verify_key_base64, get_verify_key
 
 from twisted.internet import defer
 
@@ -40,7 +40,7 @@ class MockPerspectiveServer(object):
 
     def get_verify_keys(self):
         vk = signedjson.key.get_verify_key(self.key)
-        return {"%s:%s" % (vk.alg, vk.version): vk}
+        return {"%s:%s" % (vk.alg, vk.version): encode_verify_key_base64(vk)}
 
     def get_signed_key(self, server_name, verify_key):
         key_id = "%s:%s" % (verify_key.alg, verify_key.version)
@@ -48,9 +48,7 @@ class MockPerspectiveServer(object):
             "server_name": server_name,
             "old_verify_keys": {},
             "valid_until_ts": time.time() * 1000 + 3600,
-            "verify_keys": {
-                key_id: {"key": signedjson.key.encode_verify_key_base64(verify_key)}
-            },
+            "verify_keys": {key_id: {"key": encode_verify_key_base64(verify_key)}},
         }
         self.sign_response(res)
         return res
@@ -63,10 +61,18 @@ class KeyringTestCase(unittest.HomeserverTestCase):
     def make_homeserver(self, reactor, clock):
         self.mock_perspective_server = MockPerspectiveServer()
         self.http_client = Mock()
-        hs = self.setup_test_homeserver(handlers=None, http_client=self.http_client)
-        keys = self.mock_perspective_server.get_verify_keys()
-        hs.config.perspectives = {self.mock_perspective_server.server_name: keys}
-        return hs
+
+        config = self.default_config()
+        config["trusted_key_servers"] = [
+            {
+                "server_name": self.mock_perspective_server.server_name,
+                "verify_keys": self.mock_perspective_server.get_verify_keys(),
+            }
+        ]
+
+        return self.setup_test_homeserver(
+            handlers=None, http_client=self.http_client, config=config
+        )
 
     def check_context(self, _, expected):
         self.assertEquals(
@@ -371,10 +377,18 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):
     def make_homeserver(self, reactor, clock):
         self.mock_perspective_server = MockPerspectiveServer()
         self.http_client = Mock()
-        hs = self.setup_test_homeserver(handlers=None, http_client=self.http_client)
-        keys = self.mock_perspective_server.get_verify_keys()
-        hs.config.perspectives = {self.mock_perspective_server.server_name: keys}
-        return hs
+
+        config = self.default_config()
+        config["trusted_key_servers"] = [
+            {
+                "server_name": self.mock_perspective_server.server_name,
+                "verify_keys": self.mock_perspective_server.get_verify_keys(),
+            }
+        ]
+
+        return self.setup_test_homeserver(
+            handlers=None, http_client=self.http_client, config=config
+        )
 
     def test_get_keys_from_perspectives(self):
         # arbitrarily advance the clock a bit
@@ -439,8 +453,7 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):
         self.assertEqual(res["ts_valid_until_ms"], VALID_UNTIL_TS)
 
         self.assertEqual(
-            bytes(res["key_json"]),
-            canonicaljson.encode_canonical_json(response),
+            bytes(res["key_json"]), canonicaljson.encode_canonical_json(response)
         )
 
     def test_invalid_perspectives_responses(self):
diff --git a/tests/http/federation/test_matrix_federation_agent.py b/tests/http/federation/test_matrix_federation_agent.py
index 4153da4da7..05880a1048 100644
--- a/tests/http/federation/test_matrix_federation_agent.py
+++ b/tests/http/federation/test_matrix_federation_agent.py
@@ -57,6 +57,7 @@ class MatrixFederationAgentTests(TestCase):
         # present will not be trusted. We should do better here, though.
         config_dict = default_config("test", parse=False)
         config_dict["federation_verify_certificates"] = False
+        config_dict["trusted_key_servers"] = []
         config = HomeServerConfig()
         config.parse_config_dict(config_dict)