1 files changed, 64 insertions, 0 deletions
diff --git a/synapse/api/events/utils.py b/synapse/api/events/utils.py
new file mode 100644
index 0000000000..c3a32be8c1
--- /dev/null
+++ b/synapse/api/events/utils.py
@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 OpenMarket 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.
+
+from .room import (
+    RoomMemberEvent, RoomJoinRulesEvent, RoomPowerLevelsEvent,
+    RoomAddStateLevelEvent, RoomSendEventLevelEvent, RoomOpsPowerLevelsEvent,
+    RoomAliasesEvent, RoomCreateEvent,
+)
+
+def prune_event(event):
+    """ Prunes the given event of all keys we don't know about or think could
+    potentially be dodgy.
+
+    This is used when we "redact" an event. We want to remove all fields that
+    the user has specified, but we do want to keep necessary information like
+    type, state_key etc.
+    """
+
+    # Remove all extraneous fields.
+    event.unrecognized_keys = {}
+
+    new_content = {}
+
+    def add_fields(*fields):
+        for field in fields:
+            if field in event.content:
+                new_content[field] = event.content[field]
+
+    if event.type == RoomMemberEvent.TYPE:
+        add_fields("membership")
+    elif event.type == RoomCreateEvent.TYPE:
+        add_fields("creator")
+    elif event.type == RoomJoinRulesEvent.TYPE:
+        add_fields("join_rule")
+    elif event.type == RoomPowerLevelsEvent.TYPE:
+        # TODO: Actually check these are valid user_ids etc.
+        add_fields("default")
+        for k, v in event.content.items():
+            if k.startswith("@") and isinstance(v, (int, long)):
+                new_content[k] = v
+    elif event.type == RoomAddStateLevelEvent.TYPE:
+        add_fields("level")
+    elif event.type == RoomSendEventLevelEvent.TYPE:
+        add_fields("level")
+    elif event.type == RoomOpsPowerLevelsEvent.TYPE:
+        add_fields("kick_level", "ban_level", "redact_level")
+    elif event.type == RoomAliasesEvent.TYPE:
+        add_fields("aliases")
+
+    event.content = new_content
+
+    return event