1 files changed, 50 insertions, 1 deletions
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 43492add6f..5aed78e5cc 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -26,6 +26,7 @@ import synapse.logging.opentracing as opentracing
 from synapse.api.errors import CodeMessageException, SynapseError
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.types import UserID, get_domain_from_id
+from synapse.util import unwrapFirstError
 from synapse.util.retryutils import NotRetryingDestination
 
 logger = logging.getLogger(__name__)
@@ -128,9 +129,57 @@ class E2eKeysHandler(object):
         @opentracing.trace
         @defer.inlineCallbacks
         def do_remote_query(destination):
+            """This is called when we are querying the device list of a user on
+            a remote homeserver and their device list is not in the device list
+            cache. If we share a room with this user and we're not querying for
+            specific user we will update the cache
+            with their device list."""
+
             destination_query = remote_queries_not_in_cache[destination]
 
             opentracing.set_tag("key_query", destination_query)
+            # We first consider whether we wish to update the device list cache with
+            # the users device list. We want to track a user's devices when the
+            # authenticated user shares a room with the queried user and the query
+            # has not specified a particular device.
+            # If we update the cache for the queried user we remove them from further
+            # queries. We use the more efficient batched query_client_keys for all
+            # remaining users
+            user_ids_updated = []
+            for (user_id, device_list) in destination_query.items():
+                if user_id in user_ids_updated:
+                    continue
+
+                if device_list:
+                    continue
+
+                room_ids = yield self.store.get_rooms_for_user(user_id)
+                if not room_ids:
+                    continue
+
+                # We've decided we're sharing a room with this user and should
+                # probably be tracking their device lists. However, we haven't
+                # done an initial sync on the device list so we do it now.
+                try:
+                    user_devices = yield self.device_handler.device_list_updater.user_device_resync(
+                        user_id
+                    )
+                    user_devices = user_devices["devices"]
+                    for device in user_devices:
+                        results[user_id] = {device["device_id"]: device["keys"]}
+                    user_ids_updated.append(user_id)
+                except Exception as e:
+                    failures[destination] = _exception_to_failure(e)
+
+            if len(destination_query) == len(user_ids_updated):
+                # We've updated all the users in the query and we do not need to
+                # make any further remote calls.
+                return
+
+            # Remove all the users from the query which we have updated
+            for user_id in user_ids_updated:
+                destination_query.pop(user_id)
+
             try:
                 remote_result = yield self.federation.query_client_keys(
                     destination, {"device_keys": destination_query}, timeout=timeout
@@ -153,7 +202,7 @@ class E2eKeysHandler(object):
                     for destination in remote_queries_not_in_cache
                 ],
                 consumeErrors=True,
-            )
+            ).addErrback(unwrapFirstError)
         )
 
         return {"device_keys": results, "failures": failures}