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-rw-r--r--synapse/api/constants.py7
-rw-r--r--synapse/api/filtering.py3
-rw-r--r--synapse/config/server.py28
-rw-r--r--synapse/handlers/federation.py8
-rw-r--r--synapse/handlers/message.py123
-rw-r--r--synapse/handlers/room.py50
-rw-r--r--synapse/logging/_terse_json.py1
-rw-r--r--synapse/rest/client/versions.py3
-rw-r--r--synapse/rest/media/v1/thumbnailer.py5
-rw-r--r--synapse/storage/data_stores/main/end_to_end_keys.py23
-rw-r--r--synapse/storage/data_stores/main/events.py126
-rw-r--r--synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql21
-rw-r--r--synapse/storage/data_stores/main/schema/delta/56/signing_keys.sql3
-rw-r--r--synapse/storage/data_stores/main/schema/delta/56/signing_keys_nonunique_signatures.sql22
-rw-r--r--synapse/storage/data_stores/main/stream.py3
15 files changed, 393 insertions, 33 deletions
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index e3f086f1c3..0ade47e624 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -1,7 +1,8 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2017 Vector Creations Ltd
-# Copyright 2018 New Vector Ltd
+# Copyright 2018-2019 New Vector Ltd
+# 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.
@@ -147,3 +148,7 @@ class EventContentFields(object):
 
     # Labels for the event, cf https://github.com/matrix-org/matrix-doc/pull/2326
     LABELS = "org.matrix.labels"
+
+    # Timestamp to delete the event after
+    # cf https://github.com/matrix-org/matrix-doc/pull/2228
+    SELF_DESTRUCT_AFTER = "org.matrix.self_destruct_after"
diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index bec13f08d8..6eab1f13f0 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
+# Copyright 2017 Vector Creations Ltd
+# Copyright 2018-2019 New Vector Ltd
+# 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.
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 7a9d711669..a4bef00936 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -118,15 +118,16 @@ class ServerConfig(Config):
             self.allow_public_rooms_without_auth = False
             self.allow_public_rooms_over_federation = False
         else:
-            # If set to 'False', requires authentication to access the server's public
-            # rooms directory through the client API. Defaults to 'True'.
+            # If set to 'true', removes the need for authentication to access the server's
+            # public rooms directory through the client API, meaning that anyone can
+            # query the room directory. Defaults to 'false'.
             self.allow_public_rooms_without_auth = config.get(
-                "allow_public_rooms_without_auth", True
+                "allow_public_rooms_without_auth", False
             )
-            # If set to 'False', forbids any other homeserver to fetch the server's public
-            # rooms directory via federation. Defaults to 'True'.
+            # If set to 'true', allows any other homeserver to fetch the server's public
+            # rooms directory via federation. Defaults to 'false'.
             self.allow_public_rooms_over_federation = config.get(
-                "allow_public_rooms_over_federation", True
+                "allow_public_rooms_over_federation", False
             )
 
         default_room_version = config.get("default_room_version", DEFAULT_ROOM_VERSION)
@@ -490,6 +491,8 @@ class ServerConfig(Config):
             "cleanup_extremities_with_dummy_events", True
         )
 
+        self.enable_ephemeral_messages = config.get("enable_ephemeral_messages", False)
+
     def has_tls_listener(self) -> bool:
         return any(l["tls"] for l in self.listeners)
 
@@ -618,15 +621,16 @@ class ServerConfig(Config):
         #
         #require_auth_for_profile_requests: true
 
-        # If set to 'false', requires authentication to access the server's public rooms
-        # directory through the client API. Defaults to 'true'.
+        # If set to 'true', removes the need for authentication to access the server's
+        # public rooms directory through the client API, meaning that anyone can
+        # query the room directory. Defaults to 'false'.
         #
-        #allow_public_rooms_without_auth: false
+        #allow_public_rooms_without_auth: true
 
-        # If set to 'false', forbids any other homeserver to fetch the server's public
-        # rooms directory via federation. Defaults to 'true'.
+        # If set to 'true', allows any other homeserver to fetch the server's public
+        # rooms directory via federation. Defaults to 'false'.
         #
-        #allow_public_rooms_over_federation: false
+        #allow_public_rooms_over_federation: true
 
         # The default room version for newly created rooms.
         #
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index d3267734f7..d9d0cd9eef 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -121,6 +121,7 @@ class FederationHandler(BaseHandler):
         self.pusher_pool = hs.get_pusherpool()
         self.spam_checker = hs.get_spam_checker()
         self.event_creation_handler = hs.get_event_creation_handler()
+        self._message_handler = hs.get_message_handler()
         self._server_notices_mxid = hs.config.server_notices_mxid
         self.config = hs.config
         self.http_client = hs.get_simple_http_client()
@@ -141,6 +142,8 @@ class FederationHandler(BaseHandler):
 
         self.third_party_event_rules = hs.get_third_party_event_rules()
 
+        self._ephemeral_messages_enabled = hs.config.enable_ephemeral_messages
+
     @defer.inlineCallbacks
     def on_receive_pdu(self, origin, pdu, sent_to_us_directly=False):
         """ Process a PDU received via a federation /send/ transaction, or
@@ -2715,6 +2718,11 @@ class FederationHandler(BaseHandler):
                 event_and_contexts, backfilled=backfilled
             )
 
+            if self._ephemeral_messages_enabled:
+                for (event, context) in event_and_contexts:
+                    # If there's an expiry timestamp on the event, schedule its expiry.
+                    self._message_handler.maybe_schedule_expiry(event)
+
             if not backfilled:  # Never notify for backfilled events
                 for event, _ in event_and_contexts:
                     yield self._notify_persisted_event(event, max_stream_id)
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 3b0156f516..4f53a5f5dc 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -15,6 +15,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from typing import Optional
 
 from six import iteritems, itervalues, string_types
 
@@ -22,9 +23,16 @@ from canonicaljson import encode_canonical_json, json
 
 from twisted.internet import defer
 from twisted.internet.defer import succeed
+from twisted.internet.interfaces import IDelayedCall
 
 from synapse import event_auth
-from synapse.api.constants import EventTypes, Membership, RelationTypes, UserTypes
+from synapse.api.constants import (
+    EventContentFields,
+    EventTypes,
+    Membership,
+    RelationTypes,
+    UserTypes,
+)
 from synapse.api.errors import (
     AuthError,
     Codes,
@@ -62,6 +70,17 @@ class MessageHandler(object):
         self.storage = hs.get_storage()
         self.state_store = self.storage.state
         self._event_serializer = hs.get_event_client_serializer()
+        self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages
+        self._is_worker_app = bool(hs.config.worker_app)
+
+        # The scheduled call to self._expire_event. None if no call is currently
+        # scheduled.
+        self._scheduled_expiry = None  # type: Optional[IDelayedCall]
+
+        if not hs.config.worker_app:
+            run_as_background_process(
+                "_schedule_next_expiry", self._schedule_next_expiry
+            )
 
     @defer.inlineCallbacks
     def get_room_data(
@@ -225,6 +244,100 @@ class MessageHandler(object):
             for user_id, profile in iteritems(users_with_profile)
         }
 
+    def maybe_schedule_expiry(self, event):
+        """Schedule the expiry of an event if there's not already one scheduled,
+        or if the one running is for an event that will expire after the provided
+        timestamp.
+
+        This function needs to invalidate the event cache, which is only possible on
+        the master process, and therefore needs to be run on there.
+
+        Args:
+            event (EventBase): The event to schedule the expiry of.
+        """
+        assert not self._is_worker_app
+
+        expiry_ts = event.content.get(EventContentFields.SELF_DESTRUCT_AFTER)
+        if not isinstance(expiry_ts, int) or event.is_state():
+            return
+
+        # _schedule_expiry_for_event won't actually schedule anything if there's already
+        # a task scheduled for a timestamp that's sooner than the provided one.
+        self._schedule_expiry_for_event(event.event_id, expiry_ts)
+
+    @defer.inlineCallbacks
+    def _schedule_next_expiry(self):
+        """Retrieve the ID and the expiry timestamp of the next event to be expired,
+        and schedule an expiry task for it.
+
+        If there's no event left to expire, set _expiry_scheduled to None so that a
+        future call to save_expiry_ts can schedule a new expiry task.
+        """
+        # Try to get the expiry timestamp of the next event to expire.
+        res = yield self.store.get_next_event_to_expire()
+        if res:
+            event_id, expiry_ts = res
+            self._schedule_expiry_for_event(event_id, expiry_ts)
+
+    def _schedule_expiry_for_event(self, event_id, expiry_ts):
+        """Schedule an expiry task for the provided event if there's not already one
+        scheduled at a timestamp that's sooner than the provided one.
+
+        Args:
+            event_id (str): The ID of the event to expire.
+            expiry_ts (int): The timestamp at which to expire the event.
+        """
+        if self._scheduled_expiry:
+            # If the provided timestamp refers to a time before the scheduled time of the
+            # next expiry task, cancel that task and reschedule it for this timestamp.
+            next_scheduled_expiry_ts = self._scheduled_expiry.getTime() * 1000
+            if expiry_ts < next_scheduled_expiry_ts:
+                self._scheduled_expiry.cancel()
+            else:
+                return
+
+        # Figure out how many seconds we need to wait before expiring the event.
+        now_ms = self.clock.time_msec()
+        delay = (expiry_ts - now_ms) / 1000
+
+        # callLater doesn't support negative delays, so trim the delay to 0 if we're
+        # in that case.
+        if delay < 0:
+            delay = 0
+
+        logger.info("Scheduling expiry for event %s in %.3fs", event_id, delay)
+
+        self._scheduled_expiry = self.clock.call_later(
+            delay,
+            run_as_background_process,
+            "_expire_event",
+            self._expire_event,
+            event_id,
+        )
+
+    @defer.inlineCallbacks
+    def _expire_event(self, event_id):
+        """Retrieve and expire an event that needs to be expired from the database.
+
+        If the event doesn't exist in the database, log it and delete the expiry date
+        from the database (so that we don't try to expire it again).
+        """
+        assert self._ephemeral_events_enabled
+
+        self._scheduled_expiry = None
+
+        logger.info("Expiring event %s", event_id)
+
+        try:
+            # Expire the event if we know about it. This function also deletes the expiry
+            # date from the database in the same database transaction.
+            yield self.store.expire_event(event_id)
+        except Exception as e:
+            logger.error("Could not expire event %s: %r", event_id, e)
+
+        # Schedule the expiry of the next event to expire.
+        yield self._schedule_next_expiry()
+
 
 # The duration (in ms) after which rooms should be removed
 # `_rooms_to_exclude_from_dummy_event_insertion` (with the effect that we will try
@@ -295,6 +408,10 @@ class EventCreationHandler(object):
                 5 * 60 * 1000,
             )
 
+        self._message_handler = hs.get_message_handler()
+
+        self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages
+
     @defer.inlineCallbacks
     def create_event(
         self,
@@ -877,6 +994,10 @@ class EventCreationHandler(object):
             event, context=context
         )
 
+        if self._ephemeral_events_enabled:
+            # If there's an expiry timestamp on the event, schedule its expiry.
+            self._message_handler.maybe_schedule_expiry(event)
+
         yield self.pusher_pool.on_new_notifications(event_stream_id, max_stream_id)
 
         def _notify():
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index e92b2eafd5..22768e97ff 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014 - 2016 OpenMarket Ltd
-# Copyright 2018 New Vector Ltd
+# Copyright 2018-2019 New Vector Ltd
+# 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.
@@ -198,21 +199,21 @@ class RoomCreationHandler(BaseHandler):
         # finally, shut down the PLs in the old room, and update them in the new
         # room.
         yield self._update_upgraded_room_pls(
-            requester, old_room_id, new_room_id, old_room_state
+            requester, old_room_id, new_room_id, old_room_state,
         )
 
         return new_room_id
 
     @defer.inlineCallbacks
     def _update_upgraded_room_pls(
-        self, requester, old_room_id, new_room_id, old_room_state
+        self, requester, old_room_id, new_room_id, old_room_state,
     ):
         """Send updated power levels in both rooms after an upgrade
 
         Args:
             requester (synapse.types.Requester): the user requesting the upgrade
-            old_room_id (unicode): the id of the room to be replaced
-            new_room_id (unicode): the id of the replacement room
+            old_room_id (str): the id of the room to be replaced
+            new_room_id (str): the id of the replacement room
             old_room_state (dict[tuple[str, str], str]): the state map for the old room
 
         Returns:
@@ -298,7 +299,7 @@ class RoomCreationHandler(BaseHandler):
             tombstone_event_id (unicode|str): the ID of the tombstone event in the old
                 room.
         Returns:
-            Deferred[None]
+            Deferred
         """
         user_id = requester.user.to_string()
 
@@ -333,6 +334,7 @@ class RoomCreationHandler(BaseHandler):
             (EventTypes.Encryption, ""),
             (EventTypes.ServerACL, ""),
             (EventTypes.RelatedGroups, ""),
+            (EventTypes.PowerLevels, ""),
         )
 
         old_room_state_ids = yield self.store.get_filtered_current_state_ids(
@@ -346,6 +348,31 @@ class RoomCreationHandler(BaseHandler):
             if old_event:
                 initial_state[k] = old_event.content
 
+        # Resolve the minimum power level required to send any state event
+        # We will give the upgrading user this power level temporarily (if necessary) such that
+        # they are able to copy all of the state events over, then revert them back to their
+        # original power level afterwards in _update_upgraded_room_pls
+
+        # Copy over user power levels now as this will not be possible with >100PL users once
+        # the room has been created
+
+        power_levels = initial_state[(EventTypes.PowerLevels, "")]
+
+        # Calculate the minimum power level needed to clone the room
+        event_power_levels = power_levels.get("events", {})
+        state_default = power_levels.get("state_default", 0)
+        ban = power_levels.get("ban")
+        needed_power_level = max(state_default, ban, max(event_power_levels.values()))
+
+        # Raise the requester's power level in the new room if necessary
+        current_power_level = power_levels["users"][requester.user.to_string()]
+        if current_power_level < needed_power_level:
+            # Assign this power level to the requester
+            power_levels["users"][requester.user.to_string()] = needed_power_level
+
+        # Set the power levels to the modified state
+        initial_state[(EventTypes.PowerLevels, "")] = power_levels
+
         yield self._send_events_for_new_room(
             requester,
             new_room_id,
@@ -874,6 +901,10 @@ class RoomContextHandler(object):
             room_id, event_id, before_limit, after_limit, event_filter
         )
 
+        if event_filter:
+            results["events_before"] = event_filter.filter(results["events_before"])
+            results["events_after"] = event_filter.filter(results["events_after"])
+
         results["events_before"] = yield filter_evts(results["events_before"])
         results["events_after"] = yield filter_evts(results["events_after"])
         results["event"] = event
@@ -902,7 +933,12 @@ class RoomContextHandler(object):
         state = yield self.state_store.get_state_for_events(
             [last_event_id], state_filter=state_filter
         )
-        results["state"] = list(state[last_event_id].values())
+
+        state_events = list(state[last_event_id].values())
+        if event_filter:
+            state_events = event_filter.filter(state_events)
+
+        results["state"] = state_events
 
         # We use a dummy token here as we only care about the room portion of
         # the token, which we replace.
diff --git a/synapse/logging/_terse_json.py b/synapse/logging/_terse_json.py
index 05fc64f409..03934956f4 100644
--- a/synapse/logging/_terse_json.py
+++ b/synapse/logging/_terse_json.py
@@ -256,6 +256,7 @@ class TerseJSONToTCPLogObserver(object):
             # transport is the same, just trigger a resumeProducing.
             if self._producer and r.transport is self._producer.transport:
                 self._producer.resumeProducing()
+                self._connection_waiter = None
                 return
 
             # If the producer is still producing, stop it.
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index bb30ce3f34..2a477ad22e 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
 # Copyright 2016 OpenMarket Ltd
+# Copyright 2017 Vector Creations Ltd
+# Copyright 2018-2019 New Vector Ltd
+# 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.
diff --git a/synapse/rest/media/v1/thumbnailer.py b/synapse/rest/media/v1/thumbnailer.py
index 8cf415e29d..c234ea7421 100644
--- a/synapse/rest/media/v1/thumbnailer.py
+++ b/synapse/rest/media/v1/thumbnailer.py
@@ -129,5 +129,8 @@ class Thumbnailer(object):
 
     def _encode_image(self, output_image, output_type):
         output_bytes_io = BytesIO()
-        output_image.save(output_bytes_io, self.FORMATS[output_type], quality=80)
+        fmt = self.FORMATS[output_type]
+        if fmt == "JPEG":
+            output_image = output_image.convert("RGB")
+        output_image.save(output_bytes_io, fmt, quality=80)
         return output_bytes_io
diff --git a/synapse/storage/data_stores/main/end_to_end_keys.py b/synapse/storage/data_stores/main/end_to_end_keys.py
index d8ad59ad93..643327b57b 100644
--- a/synapse/storage/data_stores/main/end_to_end_keys.py
+++ b/synapse/storage/data_stores/main/end_to_end_keys.py
@@ -145,13 +145,28 @@ class EndToEndKeyWorkerStore(SQLBaseStore):
         txn.execute(signature_sql, signature_query_params)
         rows = self.cursor_to_dict(txn)
 
+        # add each cross-signing signature to the correct device in the result dict.
         for row in rows:
+            signing_user_id = row["user_id"]
+            signing_key_id = row["key_id"]
             target_user_id = row["target_user_id"]
             target_device_id = row["target_device_id"]
-            if target_user_id in result and target_device_id in result[target_user_id]:
-                result[target_user_id][target_device_id].setdefault(
-                    "signatures", {}
-                ).setdefault(row["user_id"], {})[row["key_id"]] = row["signature"]
+            signature = row["signature"]
+
+            target_user_result = result.get(target_user_id)
+            if not target_user_result:
+                continue
+
+            target_device_result = target_user_result.get(target_device_id)
+            if not target_device_result:
+                # note that target_device_result will be None for deleted devices.
+                continue
+
+            target_device_signatures = target_device_result.setdefault("signatures", {})
+            signing_user_signatures = target_device_signatures.setdefault(
+                signing_user_id, {}
+            )
+            signing_user_signatures[signing_key_id] = signature
 
         log_kv(result)
         return result
diff --git a/synapse/storage/data_stores/main/events.py b/synapse/storage/data_stores/main/events.py
index 2737a1d3ae..79c91fe284 100644
--- a/synapse/storage/data_stores/main/events.py
+++ b/synapse/storage/data_stores/main/events.py
@@ -130,6 +130,8 @@ class EventsStore(
         if self.hs.config.redaction_retention_period is not None:
             hs.get_clock().looping_call(_censor_redactions, 5 * 60 * 1000)
 
+        self._ephemeral_messages_enabled = hs.config.enable_ephemeral_messages
+
     @defer.inlineCallbacks
     def _read_forward_extremities(self):
         def fetch(txn):
@@ -940,6 +942,12 @@ class EventsStore(
                     txn, event.event_id, labels, event.room_id, event.depth
                 )
 
+            if self._ephemeral_messages_enabled:
+                # If there's an expiry timestamp on the event, store it.
+                expiry_ts = event.content.get(EventContentFields.SELF_DESTRUCT_AFTER)
+                if isinstance(expiry_ts, int) and not event.is_state():
+                    self._insert_event_expiry_txn(txn, event.event_id, expiry_ts)
+
         # Insert into the room_memberships table.
         self._store_room_members_txn(
             txn,
@@ -1101,12 +1109,7 @@ class EventsStore(
         def _update_censor_txn(txn):
             for redaction_id, event_id, pruned_json in updates:
                 if pruned_json:
-                    self._simple_update_one_txn(
-                        txn,
-                        table="event_json",
-                        keyvalues={"event_id": event_id},
-                        updatevalues={"json": pruned_json},
-                    )
+                    self._censor_event_txn(txn, event_id, pruned_json)
 
                 self._simple_update_one_txn(
                     txn,
@@ -1117,6 +1120,22 @@ class EventsStore(
 
         yield self.runInteraction("_update_censor_txn", _update_censor_txn)
 
+    def _censor_event_txn(self, txn, event_id, pruned_json):
+        """Censor an event by replacing its JSON in the event_json table with the
+        provided pruned JSON.
+
+        Args:
+            txn (LoggingTransaction): The database transaction.
+            event_id (str): The ID of the event to censor.
+            pruned_json (str): The pruned JSON
+        """
+        self._simple_update_one_txn(
+            txn,
+            table="event_json",
+            keyvalues={"event_id": event_id},
+            updatevalues={"json": pruned_json},
+        )
+
     @defer.inlineCallbacks
     def count_daily_messages(self):
         """
@@ -1957,6 +1976,101 @@ class EventsStore(
             ],
         )
 
+    def _insert_event_expiry_txn(self, txn, event_id, expiry_ts):
+        """Save the expiry timestamp associated with a given event ID.
+
+        Args:
+            txn (LoggingTransaction): The database transaction to use.
+            event_id (str): The event ID the expiry timestamp is associated with.
+            expiry_ts (int): The timestamp at which to expire (delete) the event.
+        """
+        return self._simple_insert_txn(
+            txn=txn,
+            table="event_expiry",
+            values={"event_id": event_id, "expiry_ts": expiry_ts},
+        )
+
+    @defer.inlineCallbacks
+    def expire_event(self, event_id):
+        """Retrieve and expire an event that has expired, and delete its associated
+        expiry timestamp. If the event can't be retrieved, delete its associated
+        timestamp so we don't try to expire it again in the future.
+
+        Args:
+             event_id (str): The ID of the event to delete.
+        """
+        # Try to retrieve the event's content from the database or the event cache.
+        event = yield self.get_event(event_id)
+
+        def delete_expired_event_txn(txn):
+            # Delete the expiry timestamp associated with this event from the database.
+            self._delete_event_expiry_txn(txn, event_id)
+
+            if not event:
+                # If we can't find the event, log a warning and delete the expiry date
+                # from the database so that we don't try to expire it again in the
+                # future.
+                logger.warning(
+                    "Can't expire event %s because we don't have it.", event_id
+                )
+                return
+
+            # Prune the event's dict then convert it to JSON.
+            pruned_json = encode_json(prune_event_dict(event.get_dict()))
+
+            # Update the event_json table to replace the event's JSON with the pruned
+            # JSON.
+            self._censor_event_txn(txn, event.event_id, pruned_json)
+
+            # We need to invalidate the event cache entry for this event because we
+            # changed its content in the database. We can't call
+            # self._invalidate_cache_and_stream because self.get_event_cache isn't of the
+            # right type.
+            txn.call_after(self._get_event_cache.invalidate, (event.event_id,))
+            # Send that invalidation to replication so that other workers also invalidate
+            # the event cache.
+            self._send_invalidation_to_replication(
+                txn, "_get_event_cache", (event.event_id,)
+            )
+
+        yield self.runInteraction("delete_expired_event", delete_expired_event_txn)
+
+    def _delete_event_expiry_txn(self, txn, event_id):
+        """Delete the expiry timestamp associated with an event ID without deleting the
+        actual event.
+
+        Args:
+            txn (LoggingTransaction): The transaction to use to perform the deletion.
+            event_id (str): The event ID to delete the associated expiry timestamp of.
+        """
+        return self._simple_delete_txn(
+            txn=txn, table="event_expiry", keyvalues={"event_id": event_id}
+        )
+
+    def get_next_event_to_expire(self):
+        """Retrieve the entry with the lowest expiry timestamp in the event_expiry
+        table, or None if there's no more event to expire.
+
+        Returns: Deferred[Optional[Tuple[str, int]]]
+            A tuple containing the event ID as its first element and an expiry timestamp
+            as its second one, if there's at least one row in the event_expiry table.
+            None otherwise.
+        """
+
+        def get_next_event_to_expire_txn(txn):
+            txn.execute(
+                """
+                SELECT event_id, expiry_ts FROM event_expiry
+                ORDER BY expiry_ts ASC LIMIT 1
+                """
+            )
+
+            return txn.fetchone()
+
+        return self.runInteraction(
+            desc="get_next_event_to_expire", func=get_next_event_to_expire_txn
+        )
+
 
 AllNewEventsResult = namedtuple(
     "AllNewEventsResult",
diff --git a/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql b/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql
new file mode 100644
index 0000000000..81a36a8b1d
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/delta/56/event_expiry.sql
@@ -0,0 +1,21 @@
+/* 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.
+ */
+
+CREATE TABLE IF NOT EXISTS event_expiry (
+    event_id TEXT PRIMARY KEY,
+    expiry_ts BIGINT NOT NULL
+);
+
+CREATE INDEX event_expiry_expiry_ts_idx ON event_expiry(expiry_ts);
diff --git a/synapse/storage/data_stores/main/schema/delta/56/signing_keys.sql b/synapse/storage/data_stores/main/schema/delta/56/signing_keys.sql
index 27a96123e3..5c5fffcafb 100644
--- a/synapse/storage/data_stores/main/schema/delta/56/signing_keys.sql
+++ b/synapse/storage/data_stores/main/schema/delta/56/signing_keys.sql
@@ -40,7 +40,8 @@ CREATE TABLE IF NOT EXISTS e2e_cross_signing_signatures (
     signature TEXT NOT NULL
 );
 
-CREATE UNIQUE INDEX e2e_cross_signing_signatures_idx ON e2e_cross_signing_signatures(user_id, target_user_id, target_device_id);
+-- replaced by the index created in signing_keys_nonunique_signatures.sql
+-- CREATE UNIQUE INDEX e2e_cross_signing_signatures_idx ON e2e_cross_signing_signatures(user_id, target_user_id, target_device_id);
 
 -- stream of user signature updates
 CREATE TABLE IF NOT EXISTS user_signature_stream (
diff --git a/synapse/storage/data_stores/main/schema/delta/56/signing_keys_nonunique_signatures.sql b/synapse/storage/data_stores/main/schema/delta/56/signing_keys_nonunique_signatures.sql
new file mode 100644
index 0000000000..0aa90ebf0c
--- /dev/null
+++ b/synapse/storage/data_stores/main/schema/delta/56/signing_keys_nonunique_signatures.sql
@@ -0,0 +1,22 @@
+/* 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.
+ */
+
+/* The cross-signing signatures index should not be a unique index, because a
+ * user may upload multiple signatures for the same target user. The previous
+ * index was unique, so delete it if it's there and create a new non-unique
+ * index. */
+
+DROP INDEX IF EXISTS e2e_cross_signing_signatures_idx; CREATE INDEX IF NOT
+EXISTS e2e_cross_signing_signatures2_idx ON e2e_cross_signing_signatures(user_id, target_user_id, target_device_id);
diff --git a/synapse/storage/data_stores/main/stream.py b/synapse/storage/data_stores/main/stream.py
index 9ae4a913a1..21a410afd0 100644
--- a/synapse/storage/data_stores/main/stream.py
+++ b/synapse/storage/data_stores/main/stream.py
@@ -1,5 +1,8 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2017 Vector Creations Ltd
+# Copyright 2018-2019 New Vector Ltd
+# 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.