1 files changed, 113 insertions, 0 deletions
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py
new file mode 100644
index 0000000000..8f5d95696b
--- /dev/null
+++ b/synapse/events/third_party_rules.py
@@ -0,0 +1,113 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+from twisted.internet import defer
+
+
+class ThirdPartyEventRules(object):
+    """Allows server admins to provide a Python module implementing an extra
+    set of rules to apply when processing events.
+
+    This is designed to help admins of closed federations with enforcing custom
+    behaviours.
+    """
+
+    def __init__(self, hs):
+        self.third_party_rules = None
+
+        self.store = hs.get_datastore()
+
+        module = None
+        config = None
+        if hs.config.third_party_event_rules:
+            module, config = hs.config.third_party_event_rules
+
+        if module is not None:
+            self.third_party_rules = module(
+                config=config, http_client=hs.get_simple_http_client()
+            )
+
+    @defer.inlineCallbacks
+    def check_event_allowed(self, event, context):
+        """Check if a provided event should be allowed in the given context.
+
+        Args:
+            event (synapse.events.EventBase): The event to be checked.
+            context (synapse.events.snapshot.EventContext): The context of the event.
+
+        Returns:
+            defer.Deferred[bool]: True if the event should be allowed, False if not.
+        """
+        if self.third_party_rules is None:
+            defer.returnValue(True)
+
+        prev_state_ids = yield context.get_prev_state_ids(self.store)
+
+        # Retrieve the state events from the database.
+        state_events = {}
+        for key, event_id in prev_state_ids.items():
+            state_events[key] = yield self.store.get_event(event_id, allow_none=True)
+
+        ret = yield self.third_party_rules.check_event_allowed(event, state_events)
+        defer.returnValue(ret)
+
+    @defer.inlineCallbacks
+    def on_create_room(self, requester, config, is_requester_admin):
+        """Intercept requests to create room to allow, deny or update the
+        request config.
+
+        Args:
+            requester (Requester)
+            config (dict): The creation config from the client.
+            is_requester_admin (bool): If the requester is an admin
+
+        Returns:
+            defer.Deferred
+        """
+
+        if self.third_party_rules is None:
+            return
+
+        yield self.third_party_rules.on_create_room(
+            requester, config, is_requester_admin
+        )
+
+    @defer.inlineCallbacks
+    def check_threepid_can_be_invited(self, medium, address, room_id):
+        """Check if a provided 3PID can be invited in the given room.
+
+        Args:
+            medium (str): The 3PID's medium.
+            address (str): The 3PID's address.
+            room_id (str): The room we want to invite the threepid to.
+
+        Returns:
+            defer.Deferred[bool], True if the 3PID can be invited, False if not.
+        """
+
+        if self.third_party_rules is None:
+            defer.returnValue(True)
+
+        state_ids = yield self.store.get_filtered_current_state_ids(room_id)
+        room_state_events = yield self.store.get_events(state_ids.values())
+
+        state_events = {}
+        for key, event_id in state_ids.items():
+            state_events[key] = room_state_events[event_id]
+
+        ret = yield self.third_party_rules.check_threepid_can_be_invited(
+            medium, address, state_events
+        )
+        defer.returnValue(ret)