1 files changed, 133 insertions, 0 deletions
diff --git a/synapse/events/utils.py b/synapse/events/utils.py
new file mode 100644
index 0000000000..4849d3ce41
--- /dev/null
+++ b/synapse/events/utils.py
@@ -0,0 +1,133 @@
+# -*- 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 synapse.api.constants import EventTypes
+from . import EventBase
+
+
+def prune_event(event):
+    """ Returns a pruned version of the given event, which removes 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.
+    """
+    event_type = event.type
+
+    allowed_keys = [
+        "event_id",
+        "sender",
+        "room_id",
+        "hashes",
+        "signatures",
+        "content",
+        "type",
+        "state_key",
+        "depth",
+        "prev_events",
+        "prev_state",
+        "auth_events",
+        "origin",
+        "origin_server_ts",
+        "membership",
+    ]
+
+    new_content = {}
+
+    def add_fields(*fields):
+        for field in fields:
+            if field in event.content:
+                new_content[field] = event.content[field]
+
+    if event_type == EventTypes.Member:
+        add_fields("membership")
+    elif event_type == EventTypes.Create:
+        add_fields("creator")
+    elif event_type == EventTypes.JoinRules:
+        add_fields("join_rule")
+    elif event_type == EventTypes.PowerLevels:
+        add_fields(
+            "users",
+            "users_default",
+            "events",
+            "events_default",
+            "events_default",
+            "state_default",
+            "ban",
+            "kick",
+            "redact",
+        )
+    elif event_type == EventTypes.Aliases:
+        add_fields("aliases")
+
+    allowed_fields = {
+        k: v
+        for k, v in event.get_dict().items()
+        if k in allowed_keys
+    }
+
+    allowed_fields["content"] = new_content
+
+    allowed_fields["unsigned"] = {}
+
+    if "age_ts" in event.unsigned:
+        allowed_fields["unsigned"]["age_ts"] = event.unsigned["age_ts"]
+
+    return type(event)(allowed_fields)
+
+
+def serialize_event(hs, e):
+    # FIXME(erikj): To handle the case of presence events and the like
+    if not isinstance(e, EventBase):
+        return e
+
+    # Should this strip out None's?
+    d = {k: v for k, v in e.get_dict().items()}
+    if "age_ts" in d["unsigned"]:
+        now = int(hs.get_clock().time_msec())
+        d["unsigned"]["age"] = now - d["unsigned"]["age_ts"]
+        del d["unsigned"]["age_ts"]
+
+    d["user_id"] = d.pop("sender", None)
+
+    if "redacted_because" in e.unsigned:
+        d["redacted_because"] = serialize_event(
+            hs, e.unsigned["redacted_because"]
+        )
+
+        del d["unsigned"]["redacted_because"]
+
+    if "redacted_by" in e.unsigned:
+        d["redacted_by"] = e.unsigned["redacted_by"]
+        del d["unsigned"]["redacted_by"]
+
+    if "replaces_state" in e.unsigned:
+        d["replaces_state"] = e.unsigned["replaces_state"]
+        del d["unsigned"]["replaces_state"]
+
+    if "prev_content" in e.unsigned:
+        d["prev_content"] = e.unsigned["prev_content"]
+        del d["unsigned"]["prev_content"]
+
+    del d["auth_events"]
+    del d["prev_events"]
+    del d["hashes"]
+    del d["signatures"]
+    d.pop("depth", None)
+    d.pop("unsigned", None)
+    d.pop("origin", None)
+
+    return d