Allowing specifying IS to use in unbind API.

By default the homeserver will use the identity server used during the
binding of the 3PID to unbind the 3PID. However, we need to allow
clients to explicitly ask the homeserver to unbind via a particular
identity server, for the case where the 3PID was bound out of band from
the homeserver.

Implements MSC915.

synapse/handlers/auth.py

@@ -912,7 +912,7 @@ class AuthHandler(BaseHandler):
         )
 
     @defer.inlineCallbacks
-    def delete_threepid(self, user_id, medium, address):
+    def delete_threepid(self, user_id, medium, address, id_server=None):
         """Attempts to unbind the 3pid on the identity servers and deletes it
         from the local database.
 
@@ -920,6 +920,10 @@ class AuthHandler(BaseHandler):
             user_id (str)
             medium (str)
             address (str)
+            id_server (str|None): Use the given identity server when unbinding
+                any threepids. If None then will attempt to unbind using the
+                identity server specified when binding (if known).
+
 
         Returns:
             Deferred[bool]: Returns True if successfully unbound the 3pid on
@@ -937,6 +941,7 @@ class AuthHandler(BaseHandler):
             {
                 'medium': medium,
                 'address': address,
+                'id_server': id_server,
             },
         )
 

synapse/handlers/deactivate_account.py

@@ -43,12 +43,15 @@ class DeactivateAccountHandler(BaseHandler):
         hs.get_reactor().callWhenRunning(self._start_user_parting)
 
     @defer.inlineCallbacks
-    def deactivate_account(self, user_id, erase_data):
+    def deactivate_account(self, user_id, erase_data, id_server=None):
         """Deactivate a user's account
 
         Args:
             user_id (str): ID of user to be deactivated
             erase_data (bool): whether to GDPR-erase the user's data
+            id_server (str|None): Use the given identity server when unbinding
+                any threepids. If None then will attempt to unbind using the
+                identity server specified when binding (if known).
 
         Returns:
             Deferred[bool]: True if identity server supports removing

synapse/handlers/identity.py

@@ -159,6 +159,9 @@ class IdentityHandler(BaseHandler):
             Deferred[bool]: True on success, otherwise False if the identity
             server doesn't support unbinding
         """
+        if threepid.get("id_server"):
+            id_servers = [threepid["id_server"]]
+        else:
             id_servers = yield self.store.get_id_servers_user_bound(
                 user_id=mxid,
                 medium=threepid["medium"],

synapse/rest/client/v2_alpha/account.py

@@ -215,6 +215,7 @@ class DeactivateAccountRestServlet(RestServlet):
         )
         result = yield self._deactivate_account_handler.deactivate_account(
             requester.user.to_string(), erase,
+            id_server=body.get("id_server"),
         )
         if result:
             id_server_unbind_result = "success"
@@ -380,7 +381,7 @@ class ThreepidDeleteRestServlet(RestServlet):
 
         try:
             ret = yield self.auth_handler.delete_threepid(
-                user_id, body['medium'], body['address']
+                user_id, body['medium'], body['address'], body.get("id_server"),
             )
         except Exception:
             # NB. This endpoint should succeed if there is nothing to