1 files changed, 132 insertions, 0 deletions
diff --git a/synapse/visibility.py b/synapse/visibility.py
index 015c2bab37..ddce41efaf 100644
--- a/synapse/visibility.py
+++ b/synapse/visibility.py
@@ -20,6 +20,7 @@ from twisted.internet import defer
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.events.utils import prune_event
+from synapse.types import get_domain_from_id
 from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
 
 logger = logging.getLogger(__name__)
@@ -225,3 +226,134 @@ def filter_events_for_client(store, user_id, events, is_peeking=False,
 
     # we turn it into a list before returning it.
     defer.returnValue(list(filtered_events))
+
+
+@defer.inlineCallbacks
+def filter_events_for_server(store, server_name, events):
+    """Filter the given events for the given server, redacting those the
+    server can't see.
+
+    Assumes the server is currently in the room.
+
+    Returns
+        list[FrozenEvent]
+    """
+    # First lets check to see if all the events have a history visibility
+    # of "shared" or "world_readable". If thats the case then we don't
+    # need to check membership (as we know the server is in the room).
+    event_to_state_ids = yield store.get_state_ids_for_events(
+        frozenset(e.event_id for e in events),
+        types=(
+            (EventTypes.RoomHistoryVisibility, ""),
+        )
+    )
+
+    visibility_ids = set()
+    for sids in event_to_state_ids.itervalues():
+        hist = sids.get((EventTypes.RoomHistoryVisibility, ""))
+        if hist:
+            visibility_ids.add(hist)
+
+    # If we failed to find any history visibility events then the default
+    # is "shared" visiblity.
+    if not visibility_ids:
+        defer.returnValue(events)
+
+    event_map = yield store.get_events(visibility_ids)
+    all_open = all(
+        e.content.get("history_visibility") in (None, "shared", "world_readable")
+        for e in event_map.itervalues()
+    )
+
+    if all_open:
+        defer.returnValue(events)
+
+    # Ok, so we're dealing with events that have non-trivial visibility
+    # rules, so we need to also get the memberships of the room.
+
+    event_to_state_ids = yield store.get_state_ids_for_events(
+        frozenset(e.event_id for e in events),
+        types=(
+            (EventTypes.RoomHistoryVisibility, ""),
+            (EventTypes.Member, None),
+        )
+    )
+
+    # We only want to pull out member events that correspond to the
+    # server's domain.
+
+    def check_match(id):
+        try:
+            return server_name == get_domain_from_id(id)
+        except Exception:
+            return False
+
+    # Parses mapping `event_id -> (type, state_key) -> state event_id`
+    # to get all state ids that we're interested in.
+    event_map = yield store.get_events([
+        e_id
+        for key_to_eid in list(event_to_state_ids.values())
+        for key, e_id in key_to_eid.items()
+        if key[0] != EventTypes.Member or check_match(key[1])
+    ])
+
+    event_to_state = {
+        e_id: {
+            key: event_map[inner_e_id]
+            for key, inner_e_id in key_to_eid.iteritems()
+            if inner_e_id in event_map
+        }
+        for e_id, key_to_eid in event_to_state_ids.iteritems()
+    }
+
+    erased_senders = yield store.are_users_erased(
+        e.sender for e in events,
+    )
+
+    def redact_disallowed(event, state):
+        # if the sender has been gdpr17ed, always return a redacted
+        # copy of the event.
+        if erased_senders[event.sender]:
+            logger.info(
+                "Sender of %s has been erased, redacting",
+                event.event_id,
+            )
+            return prune_event(event)
+
+        if not state:
+            return event
+
+        history = state.get((EventTypes.RoomHistoryVisibility, ''), None)
+        if history:
+            visibility = history.content.get("history_visibility", "shared")
+            if visibility in ["invited", "joined"]:
+                # We now loop through all state events looking for
+                # membership states for the requesting server to determine
+                # if the server is either in the room or has been invited
+                # into the room.
+                for ev in state.itervalues():
+                    if ev.type != EventTypes.Member:
+                        continue
+                    try:
+                        domain = get_domain_from_id(ev.state_key)
+                    except Exception:
+                        continue
+
+                    if domain != server_name:
+                        continue
+
+                    memtype = ev.membership
+                    if memtype == Membership.JOIN:
+                        return event
+                    elif memtype == Membership.INVITE:
+                        if visibility == "invited":
+                            return event
+                else:
+                    return prune_event(event)
+
+        return event
+
+    defer.returnValue([
+        redact_disallowed(e, event_to_state[e.event_id])
+        for e in events
+    ])