Add experimental support for MSC3202: allowing application services to masquerade as specific devices.

synapse/api/auth.py

@@ -155,24 +155,34 @@ async def get_user_by_req(
 
             access_token = self.get_access_token_from_request(request)
 
-            user_id, app_service = await self._get_appservice_user_id(request)
+            (
+                user_id,
+                device_id,
+                app_service,
+            ) = await self._get_appservice_user_id_and_device_id(request)
             if user_id and app_service:
                 if ip_addr and self._track_appservice_user_ips:
                     await self.store.insert_client_ip(
                         user_id=user_id,
                         access_token=access_token,
                         ip=ip_addr,
                         user_agent=user_agent,
-                        device_id="dummy-device",  # stubbed
+                        device_id="dummy-device"
+                        if device_id is None
+                        else device_id,  # stubbed
                     )
 
-                requester = create_requester(user_id, app_service=app_service)
+                requester = create_requester(
+                    user_id, app_service=app_service, device_id=device_id
+                )
 
                 request.requester = user_id
                 if user_id in self._force_tracing_for_users:
                     opentracing.force_tracing()
                 opentracing.set_tag("authenticated_entity", user_id)
                 opentracing.set_tag("user_id", user_id)
+                if device_id is not None:
+                    opentracing.set_tag("device_id", device_id)
                 opentracing.set_tag("appservice_id", app_service.id)
 
                 return requester
@@ -274,33 +284,58 @@ async def validate_appservice_can_control_user_id(
                 403, "Application service has not registered this user (%s)" % user_id
             )
 
-    async def _get_appservice_user_id(
+    async def _get_appservice_user_id_and_device_id(
         self, request: Request
-    ) -> Tuple[Optional[str], Optional[ApplicationService]]:
+    ) -> Tuple[Optional[str], Optional[str], Optional[ApplicationService]]:
+        """
+        Given a request, reads the request parameters to determine:
+        - whether it's an application service that's making this request
+        - what user the application service should be treated as controlling
+          (the user_id URI parameter allows an application service to masquerade
+          any applicable user in its namespace)
+        - what device the application service should be treated as controlling
+          (the device_id[^1] URI parameter allows an application service to masquerade
+          as any device that exists for the relevant user)
+
+        [^1] Unstable and provided by MSC3202.
+             Must use `org.matrix.msc3202.device_id` in place of `device_id` for now.
+
+        Returns:
+            3-tuple of
+            (user ID?, device ID?, application service?)
+
+        Postconditions:
+        - If an application service is returned, so is a user ID
+        - A user ID is never returned without an application service
+        - A device ID is never returned without a user ID or an application service
+        - The returned application service, if present, is permitted to control the
+          returned user ID.
+        - The returned device ID, if present, has been checked to be a valid device ID
+          for the returned user ID.
+        """
         app_service = self.store.get_app_service_by_token(
             self.get_access_token_from_request(request)
         )
         if app_service is None:
-            return None, None
+            return None, None, None
 
         if app_service.ip_range_whitelist:
             ip_address = IPAddress(request.getClientIP())
             if ip_address not in app_service.ip_range_whitelist:
-                return None, None
+                return None, None, None
 
         # This will always be set by the time Twisted calls us.
         assert request.args is not None
 
-        if b"user_id" not in request.args:
-            return app_service.sender, app_service
-
-        user_id = request.args[b"user_id"][0].decode("utf8")
-        await self.validate_appservice_can_control_user_id(app_service, user_id)
-
-        if app_service.sender == user_id:
-            return app_service.sender, app_service
+        if b"user_id" in request.args:
+            effective_user_id = request.args[b"user_id"][0].decode("utf8")
+            await self.validate_appservice_can_control_user_id(
+                app_service, effective_user_id
+            )
+        else:
+            effective_user_id = app_service.sender
 
-        return user_id, app_service
+        return effective_user_id, None, app_service
 
     async def get_user_by_access_token(
         self,

synapse/storage/databases/main/devices.py

@@ -112,6 +112,8 @@ async def get_device(self, user_id: str, device_id: str) -> Dict[str, Any]:
             A dict containing the device information
         Raises:
             StoreError: if the device is not found
+        See also:
+            `get_device_opt` which returns None instead if the device is not found
         """
         return await self.db_pool.simple_select_one(
             table="devices",
@@ -120,6 +122,26 @@ async def get_device(self, user_id: str, device_id: str) -> Dict[str, Any]:
             desc="get_device",
         )
 
+    async def get_device_opt(
+        self, user_id: str, device_id: str
+    ) -> Optional[Dict[str, Any]]:
+        """Retrieve a device. Only returns devices that are not marked as
+        hidden.
+
+        Args:
+            user_id: The ID of the user which owns the device
+            device_id: The ID of the device to retrieve
+        Returns:
+            A dict containing the device information, or None if the device does not exist.
+        """
+        return await self.db_pool.simple_select_one(
+            table="devices",
+            keyvalues={"user_id": user_id, "device_id": device_id, "hidden": False},
+            retcols=("user_id", "device_id", "display_name"),
+            desc="get_device",
+            allow_none=True,
+        )
+
     async def get_devices_by_user(self, user_id: str) -> Dict[str, Dict[str, str]]:
         """Retrieve all of a user's registered devices. Only returns devices
         that are not marked as hidden.