Track IS used to bind 3PIDs

This will then be used to know which IS to default to when unbinding the
threepid.

synapse/handlers/identity.py

@@ -132,6 +132,14 @@ class IdentityHandler(BaseHandler):
                 }
             )
             logger.debug("bound threepid %r to %s", creds, mxid)
+
+            # Remember where we bound the threepid
+            yield self.store.add_user_bound_threepid(
+                user_id=mxid,
+                medium=data["medium"],
+                address=data["address"],
+                id_server=id_server,
+            )
         except CodeMessageException as e:
             data = json.loads(e.msg)  # XXX WAT?
         defer.returnValue(data)
@@ -188,6 +196,13 @@ class IdentityHandler(BaseHandler):
                 content,
                 headers,
             )
+
+            yield self.store.remove_user_bound_threepid(
+                user_id=mxid,
+                medium=threepid["medium"],
+                address=threepid["address"],
+                id_server=id_server,
+            )
         except HttpResponseException as e:
             if e.code in (400, 404, 501,):
                 # The remote server probably doesn't support unbinding (yet)

synapse/storage/registration.py

@@ -328,6 +328,83 @@ class RegistrationWorkerStore(SQLBaseStore):
             desc="user_delete_threepids",
         )
 
+    def add_user_bound_threepid(self, user_id, medium, address, id_server):
+        """The server proxied a bind request to the given identity server on
+        behalf of the given user. We need to remember this in case the user
+        asks us to unbind the threepid.
+
+        Args:
+            user_id (str)
+            medium (str)
+            address (str)
+            id_server (str)
+
+        Returns:
+            Deferred
+        """
+        # We need to use an upsert, in case they user had already bound the
+        # threepid
+        return self._simple_upsert(
+            table="user_threepid_id_server",
+            keyvalues={
+                "user_id": user_id,
+                "medium": medium,
+                "address": address,
+                "id_server": id_server,
+            },
+            values={},
+            insertion_values={},
+            desc="add_user_bound_threepid",
+        )
+
+    def remove_user_bound_threepid(self, user_id, medium, address, id_server):
+        """The server proxied a bind request to the given identity server on
+        behalf of the given user. We need to remember this in case the user
+        asks us to unbind the threepid.
+
+        Args:
+            user_id (str)
+            medium (str)
+            address (str)
+            id_server (str)
+
+        Returns:
+            Deferred
+        """
+        return self._simple_delete(
+            table="user_threepid_id_server",
+            keyvalues={
+                "user_id": user_id,
+                "medium": medium,
+                "address": address,
+                "id_server": id_server,
+            },
+            desc="remove_user_bound_threepid",
+        )
+
+    def get_id_servers_user_bound(self, user_id, medium, address):
+        """Get the list of identity servers that the server proxied bind
+        requests to for given user and threepid
+
+        Args:
+            user_id (str)
+            medium (str)
+            address (str)
+
+        Returns:
+            Deferred[list[str]]: Resolves to a list of identity servers
+        """
+        return self._simple_select_onecol(
+            table="user_threepid_id_server",
+            keyvalues={
+                "user_id": user_id,
+                "medium": medium,
+                "address": address,
+            },
+            retcol="id_server",
+            desc="get_id_servers_user_bound",
+        )
+
 
 class RegistrationStore(RegistrationWorkerStore,
                         background_updates.BackgroundUpdateStore):

synapse/storage/schema/delta/53/user_threepid_id.sql

@@ -0,0 +1,27 @@
+/* Copyright 2019 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Tracks when
+CREATE TABlE user_threepid_id_server (
+    user_id TEXT NOT NULL,
+    medium TEXT NOT NULL,
+    address TEXT NOT NULL,
+    id_server TEXT NOT NULL
+);
+
+CREATE UNIQUE INDEX user_threepid_id_server_idx ON user_threepid_id_server(
+    user_id, medium, address, id_server
+);
+