Add authentication to thirdparty bridge APIs

changelog.d/12746.bugfix

@@ -0,0 +1 @@
+Always send an `access_token` in `/thirdparty/` requests to appservices, as required by the [Matrix specification](https://spec.matrix.org/v1.1/application-service-api/#third-party-networks).

synapse/appservice/api.py

@@ -14,7 +14,7 @@
 # limitations under the License.
 import logging
 import urllib.parse
-from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Tuple
+from typing import TYPE_CHECKING, Any, Dict, Iterable, List, Mapping, Optional, Tuple
 
 from prometheus_client import Counter
 from typing_extensions import TypeGuard
@@ -155,14 +155,21 @@ async def query_3pe(
         if service.url is None:
             return []
 
+        # This is required by the configuration.
+        assert service.hs_token is not None
+
         uri = "%s%s/thirdparty/%s/%s" % (
             service.url,
             APP_SERVICE_PREFIX,
             kind,
             urllib.parse.quote(protocol),
         )
         try:
-            response = await self.get_json(uri, fields)
+            args: Mapping[Any, Any] = {
+                **fields,
+                b"access_token": service.hs_token,
+            }
+            response = await self.get_json(uri, args=args)
             if not isinstance(response, list):
                 logger.warning(
                     "query_3pe to %s returned an invalid response %r", uri, response
@@ -190,13 +197,15 @@ async def get_3pe_protocol(
             return {}
 
         async def _get() -> Optional[JsonDict]:
+            # This is required by the configuration.
+            assert service.hs_token is not None
             uri = "%s%s/thirdparty/protocol/%s" % (
                 service.url,
                 APP_SERVICE_PREFIX,
                 urllib.parse.quote(protocol),
             )
             try:
-                info = await self.get_json(uri)
+                info = await self.get_json(uri, {"access_token": service.hs_token})
 
                 if not _is_valid_3pe_metadata(info):
                     logger.warning(

tests/appservice/test_api.py

@@ -0,0 +1,102 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from typing import Any, List, Mapping
+from unittest.mock import Mock
+
+from twisted.test.proto_helpers import MemoryReactor
+
+from synapse.appservice import ApplicationService
+from synapse.server import HomeServer
+from synapse.types import JsonDict
+from synapse.util import Clock
+
+from tests import unittest
+
+PROTOCOL = "myproto"
+TOKEN = "myastoken"
+URL = "http://mytestservice"
+
+
+class ApplicationServiceApiTestCase(unittest.HomeserverTestCase):
+    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer):
+        self.api = hs.get_application_service_api()
+        self.service = ApplicationService(
+            id="unique_identifier",
+            sender="@as:test",
+            url=URL,
+            token="unused",
+            hs_token=TOKEN,
+            hostname="myserver",
+        )
+
+    def test_query_3pe_authenticates_token(self):
+        """
+        Tests that 3pe queries to the appservice are authenticated
+        with the appservice's token.
+        """
+
+        SUCCESS_RESULT_USER = [
+            {
+                "protocol": PROTOCOL,
+                "userid": "@a:user",
+                "fields": {
+                    "more": "fields",
+                },
+            }
+        ]
+        SUCCESS_RESULT_LOCATION = [
+            {
+                "protocol": PROTOCOL,
+                "alias": "#a:room",
+                "fields": {
+                    "more": "fields",
+                },
+            }
+        ]
+
+        URL_USER = f"{URL}/_matrix/app/unstable/thirdparty/user/{PROTOCOL}"
+        URL_LOCATION = f"{URL}/_matrix/app/unstable/thirdparty/location/{PROTOCOL}"
+
+        self.request_url = None
+
+        async def get_json(url: str, args: Mapping[Any, Any]) -> List[JsonDict]:
+            if not args.get(b"access_token"):
+                raise RuntimeError("Access token not provided")
+
+            self.assertEqual(args.get(b"access_token"), TOKEN)
+            self.request_url = url
+            if url == URL_USER:
+                return SUCCESS_RESULT_USER
+            elif url == URL_LOCATION:
+                return SUCCESS_RESULT_LOCATION
+            else:
+                raise RuntimeError(
+                    "URL provided was invalid. This should never be seen."
+                )
+
+        # We assign to a method, which mypy doesn't like.
+        self.api.get_json = Mock(side_effect=get_json)  # type: ignore[assignment]
+
+        result = self.get_success(
+            self.api.query_3pe(self.service, "user", PROTOCOL, {b"some": [b"field"]})
+        )
+        self.assertEqual(self.request_url, URL_USER)
+        self.assertEqual(result, SUCCESS_RESULT_USER)
+        result = self.get_success(
+            self.api.query_3pe(
+                self.service, "location", PROTOCOL, {b"some": [b"field"]}
+            )
+        )
+        self.assertEqual(self.request_url, URL_LOCATION)
+        self.assertEqual(result, SUCCESS_RESULT_LOCATION)