Send the appservice access token as a header. (#13996)

Implements MSC2832 by sending application service access
tokens in the Authorization header.

The access token is also still sent as a query parameter until
the application service ecosystem has fully migrated to using
headers. In the future this could be made opt-in, or removed
completely.

3 files changed, 26 insertions, 6 deletions

diff --git a/changelog.d/13996.feature b/changelog.d/13996.feature
new file mode 100644
index 0000000000..771f1c97a3
--- /dev/null
+++ b/changelog.d/13996.feature
@@ -0,0 +1 @@
+Send application service access tokens as a header (and query parameter). Implement [MSC2832](https://github.com/matrix-org/matrix-spec-proposals/pull/2832).
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index 0963fb3bb4..fbac4375b0 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -120,7 +120,11 @@ class ApplicationServiceApi(SimpleHttpClient):
 
         uri = service.url + ("/users/%s" % urllib.parse.quote(user_id))
         try:
-            response = await self.get_json(uri, {"access_token": service.hs_token})
+            response = await self.get_json(
+                uri,
+                {"access_token": service.hs_token},
+                headers={"Authorization": f"Bearer {service.hs_token}"},
+            )
             if response is not None:  # just an empty json object
                 return True
         except CodeMessageException as e:
@@ -140,7 +144,11 @@ class ApplicationServiceApi(SimpleHttpClient):
 
         uri = service.url + ("/rooms/%s" % urllib.parse.quote(alias))
         try:
-            response = await self.get_json(uri, {"access_token": service.hs_token})
+            response = await self.get_json(
+                uri,
+                {"access_token": service.hs_token},
+                headers={"Authorization": f"Bearer {service.hs_token}"},
+            )
             if response is not None:  # just an empty json object
                 return True
         except CodeMessageException as e:
@@ -181,7 +189,9 @@ class ApplicationServiceApi(SimpleHttpClient):
                 **fields,
                 b"access_token": service.hs_token,
             }
-            response = await self.get_json(uri, args=args)
+            response = await self.get_json(
+                uri, args=args, headers={"Authorization": f"Bearer {service.hs_token}"}
+            )
             if not isinstance(response, list):
                 logger.warning(
                     "query_3pe to %s returned an invalid response %r", uri, response
@@ -217,7 +227,11 @@ class ApplicationServiceApi(SimpleHttpClient):
                 urllib.parse.quote(protocol),
             )
             try:
-                info = await self.get_json(uri, {"access_token": service.hs_token})
+                info = await self.get_json(
+                    uri,
+                    {"access_token": service.hs_token},
+                    headers={"Authorization": f"Bearer {service.hs_token}"},
+                )
 
                 if not _is_valid_3pe_metadata(info):
                     logger.warning(
@@ -313,6 +327,7 @@ class ApplicationServiceApi(SimpleHttpClient):
                 uri=uri,
                 json_body=body,
                 args={"access_token": service.hs_token},
+                headers={"Authorization": f"Bearer {service.hs_token}"},
             )
             if logger.isEnabledFor(logging.DEBUG):
                 logger.debug(
diff --git a/tests/appservice/test_api.py b/tests/appservice/test_api.py
index 532b676365..11008ac1fb 100644
--- a/tests/appservice/test_api.py
+++ b/tests/appservice/test_api.py
@@ -69,10 +69,14 @@ class ApplicationServiceApiTestCase(unittest.HomeserverTestCase):
 
         self.request_url = None
 
-        async def get_json(url: str, args: Mapping[Any, Any]) -> List[JsonDict]:
-            if not args.get(b"access_token"):
+        async def get_json(
+            url: str, args: Mapping[Any, Any], headers: Mapping[Any, Any]
+        ) -> List[JsonDict]:
+            # Ensure the access token is passed as both a header and query arg.
+            if not headers.get("Authorization") or not args.get(b"access_token"):
                 raise RuntimeError("Access token not provided")
 
+            self.assertEqual(headers.get("Authorization"), f"Bearer {TOKEN}")
             self.assertEqual(args.get(b"access_token"), TOKEN)
             self.request_url = url
             if url == URL_USER: