1 files changed, 17 insertions, 2 deletions
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index cc4af23962..b0eb0c6d9d 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -32,6 +32,14 @@ HOUR_IN_MS = 60 * 60 * 1000
 APP_SERVICE_PREFIX = "/_matrix/app/unstable"
 
 
+def _is_valid_3pe_metadata(info):
+    if "instances" not in info:
+        return False
+    if not isinstance(info["instances"], list):
+        return False
+    return True
+
+
 def _is_valid_3pe_result(r, field):
     if not isinstance(r, dict):
         return False
@@ -162,11 +170,18 @@ class ApplicationServiceApi(SimpleHttpClient):
                 urllib.quote(protocol)
             )
             try:
-                defer.returnValue((yield self.get_json(uri, {})))
+                info = yield self.get_json(uri, {})
+
+                if not _is_valid_3pe_metadata(info):
+                    logger.warning("query_3pe_protocol to %s did not return a"
+                                   " valid result", uri)
+                    defer.returnValue(None)
+
+                defer.returnValue(info)
             except Exception as ex:
                 logger.warning("query_3pe_protocol to %s threw exception %s",
                                uri, ex)
-                defer.returnValue({})
+                defer.returnValue(None)
 
         key = (service.id, protocol)
         return self.protocol_meta_cache.get(key) or (