Merge tag 'v1.2.1' into shhs shhs-v1.2.1

Synapse 1.2.1 (2019-07-26)
==========================

Security update
---------------

This release includes *four* security fixes:

- Prevent an attack where a federated server could send redactions for arbitrary events in v1 and v2 rooms. ([\#5767](https://github.com/matrix-org/synapse/issues/5767))
- Prevent a denial-of-service attack where cycles of redaction events would make Synapse spin infinitely. Thanks to `@lrizika:matrix.org` for identifying and responsibly disclosing this issue. ([0f2ecb961](https://github.com/matrix-org/synapse/commit/0f2ecb961))
- Prevent an attack where users could be joined or parted from public rooms without their consent. Thanks to @Dylanger for identifying and responsibly disclosing this issue. ([\#5744](https://github.com/matrix-org/synapse/issues/5744))
- Fix a vulnerability where a federated server could spoof read-receipts from
  users on other servers. Thanks to @Dylanger for identifying this issue too. ([\#5743](https://github.com/matrix-org/synapse/issues/5743))

Additionally, the following fix was in Synapse **1.2.0**, but was not correctly
identified during the original release:

- It was possible for a room moderator to send a redaction for an `m.room.create` event, which would downgrade the room to version 1. Thanks to `/dev/ponies` for identifying and responsibly disclosing this issue! ([\#5701](https://github.com/matrix-org/synapse/issues/5701))

1 files changed, 22 insertions, 13 deletions

diff --git a/synapse/handlers/receipts.py b/synapse/handlers/receipts.py
index a85dd8cdee..e58bf7e360 100644
--- a/synapse/handlers/receipts.py
+++ b/synapse/handlers/receipts.py
@@ -17,7 +17,7 @@ import logging
 from twisted.internet import defer
 
 from synapse.handlers._base import BaseHandler
-from synapse.types import ReadReceipt
+from synapse.types import ReadReceipt, get_domain_from_id
 
 logger = logging.getLogger(__name__)
 
@@ -40,18 +40,27 @@ class ReceiptsHandler(BaseHandler):
     def _received_remote_receipt(self, origin, content):
         """Called when we receive an EDU of type m.receipt from a remote HS.
         """
-        receipts = [
-            ReadReceipt(
-                room_id=room_id,
-                receipt_type=receipt_type,
-                user_id=user_id,
-                event_ids=user_values["event_ids"],
-                data=user_values.get("data", {}),
-            )
-            for room_id, room_values in content.items()
-            for receipt_type, users in room_values.items()
-            for user_id, user_values in users.items()
-        ]
+        receipts = []
+        for room_id, room_values in content.items():
+            for receipt_type, users in room_values.items():
+                for user_id, user_values in users.items():
+                    if get_domain_from_id(user_id) != origin:
+                        logger.info(
+                            "Received receipt for user %r from server %s, ignoring",
+                            user_id,
+                            origin,
+                        )
+                        continue
+
+                    receipts.append(
+                        ReadReceipt(
+                            room_id=room_id,
+                            receipt_type=receipt_type,
+                            user_id=user_id,
+                            event_ids=user_values["event_ids"],
+                            data=user_values.get("data", {}),
+                        )
+                    )
 
         yield self._handle_new_receipts(receipts)