Support for MSC2285 (hidden read receipts) (#10413)

Implementation of matrix-org/matrix-spec-proposals#2285

changelog.d/10413.feature

@@ -0,0 +1 @@
+Support for [MSC2285 (hidden read receipts)](https://github.com/matrix-org/matrix-doc/pull/2285). Contributed by @SimonBrandner.

synapse/api/constants.py

@@ -224,3 +224,7 @@ class HistoryVisibility:
     JOINED = "joined"
     SHARED = "shared"
     WORLD_READABLE = "world_readable"
+
+
+class ReadReceiptEventFields:
+    MSC2285_HIDDEN = "org.matrix.msc2285.hidden"

synapse/config/experimental.py

@@ -33,5 +33,8 @@ def read_config(self, config: JsonDict, **kwargs):
         # MSC2716 (backfill existing history)
         self.msc2716_enabled: bool = experimental.get("msc2716_enabled", False)
 
+        # MSC2285 (hidden read receipts)
+        self.msc2285_enabled: bool = experimental.get("msc2285_enabled", False)
+
         # MSC3244 (room version capabilities)
         self.msc3244_enabled: bool = experimental.get("msc3244_enabled", False)

synapse/handlers/initial_sync.py

@@ -21,6 +21,7 @@
 from synapse.api.errors import SynapseError
 from synapse.events.validator import EventValidator
 from synapse.handlers.presence import format_user_presence_state
+from synapse.handlers.receipts import ReceiptEventSource
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.storage.roommember import RoomsForUser
 from synapse.streams.config import PaginationConfig
@@ -134,6 +135,8 @@ async def _snapshot_all_rooms(
             joined_rooms,
             to_key=int(now_token.receipt_key),
         )
+        if self.hs.config.experimental.msc2285_enabled:
+            receipt = ReceiptEventSource.filter_out_hidden(receipt, user_id)
 
         tags_by_room = await self.store.get_tags_for_user(user_id)
 
@@ -430,7 +433,9 @@ async def get_receipts():
                 room_id, to_key=now_token.receipt_key
             )
             if not receipts:
-                receipts = []
+                return []
+            if self.hs.config.experimental.msc2285_enabled:
+                receipts = ReceiptEventSource.filter_out_hidden(receipts, user_id)
             return receipts
 
         presence, receipts, (messages, token) = await make_deferred_yieldable(

synapse/handlers/receipts.py

@@ -14,9 +14,10 @@
 import logging
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
+from synapse.api.constants import ReadReceiptEventFields
 from synapse.appservice import ApplicationService
 from synapse.handlers._base import BaseHandler
-from synapse.types import JsonDict, ReadReceipt, get_domain_from_id
+from synapse.types import JsonDict, ReadReceipt, UserID, get_domain_from_id
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -137,7 +138,7 @@ async def _handle_new_receipts(self, receipts: List[ReadReceipt]) -> bool:
         return True
 
     async def received_client_receipt(
-        self, room_id: str, receipt_type: str, user_id: str, event_id: str
+        self, room_id: str, receipt_type: str, user_id: str, event_id: str, hidden: bool
     ) -> None:
         """Called when a client tells us a local user has read up to the given
         event_id in the room.
@@ -147,23 +148,67 @@ async def received_client_receipt(
             receipt_type=receipt_type,
             user_id=user_id,
             event_ids=[event_id],
-            data={"ts": int(self.clock.time_msec())},
+            data={"ts": int(self.clock.time_msec()), "hidden": hidden},
         )
 
         is_new = await self._handle_new_receipts([receipt])
         if not is_new:
             return
 
-        if self.federation_sender:
+        if self.federation_sender and not (
+            self.hs.config.experimental.msc2285_enabled and hidden
+        ):
             await self.federation_sender.send_read_receipt(receipt)
 
 
 class ReceiptEventSource:
     def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastore()
+        self.config = hs.config
+
+    @staticmethod
+    def filter_out_hidden(events: List[JsonDict], user_id: str) -> List[JsonDict]:
+        visible_events = []
+
+        # filter out hidden receipts the user shouldn't see
+        for event in events:
+            content = event.get("content", {})
+            new_event = event.copy()
+            new_event["content"] = {}
+
+            for event_id in content.keys():
+                event_content = content.get(event_id, {})
+                m_read = event_content.get("m.read", {})
+
+                # If m_read is missing copy over the original event_content as there is nothing to process here
+                if not m_read:
+                    new_event["content"][event_id] = event_content.copy()
+                    continue
+
+                new_users = {}
+                for rr_user_id, user_rr in m_read.items():
+                    hidden = user_rr.get("hidden", None)
+                    if hidden is not True or rr_user_id == user_id:
+                        new_users[rr_user_id] = user_rr.copy()
+                        # If hidden has a value replace hidden with the correct prefixed key
+                        if hidden is not None:
+                            new_users[rr_user_id].pop("hidden")
+                            new_users[rr_user_id][
+                                ReadReceiptEventFields.MSC2285_HIDDEN
+                            ] = hidden
+
+                # Set new users unless empty
+                if len(new_users.keys()) > 0:
+                    new_event["content"][event_id] = {"m.read": new_users}
+
+            # Append new_event to visible_events unless empty
+            if len(new_event["content"].keys()) > 0:
+                visible_events.append(new_event)
+
+        return visible_events
 
     async def get_new_events(
-        self, from_key: int, room_ids: List[str], **kwargs
+        self, from_key: int, room_ids: List[str], user: UserID, **kwargs
     ) -> Tuple[List[JsonDict], int]:
         from_key = int(from_key)
         to_key = self.get_current_key()
@@ -175,6 +220,9 @@ async def get_new_events(
             room_ids, from_key=from_key, to_key=to_key
         )
 
+        if self.config.experimental.msc2285_enabled:
+            events = ReceiptEventSource.filter_out_hidden(events, user.to_string())
+
         return (events, to_key)
 
     async def get_new_events_as(

synapse/replication/tcp/client.py

@@ -393,6 +393,11 @@ async def _on_new_receipts(self, rows):
             # we only want to send on receipts for our own users
             if not self._is_mine_id(receipt.user_id):
                 continue
+            if (
+                receipt.data.get("hidden", False)
+                and self._hs.config.experimental.msc2285_enabled
+            ):
+                continue
             receipt_info = ReadReceipt(
                 receipt.room_id,
                 receipt.receipt_type,

synapse/rest/client/v2_alpha/read_marker.py

@@ -14,6 +14,8 @@
 
 import logging
 
+from synapse.api.constants import ReadReceiptEventFields
+from synapse.api.errors import Codes, SynapseError
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 
 from ._base import client_patterns
@@ -37,14 +39,24 @@ async def on_POST(self, request, room_id):
         await self.presence_handler.bump_presence_active_time(requester.user)
 
         body = parse_json_object_from_request(request)
-
         read_event_id = body.get("m.read", None)
+        hidden = body.get(ReadReceiptEventFields.MSC2285_HIDDEN, False)
+
+        if not isinstance(hidden, bool):
+            raise SynapseError(
+                400,
+                "Param %s must be a boolean, if given"
+                % ReadReceiptEventFields.MSC2285_HIDDEN,
+                Codes.BAD_JSON,
+            )
+
         if read_event_id:
             await self.receipts_handler.received_client_receipt(
                 room_id,
                 "m.read",
                 user_id=requester.user.to_string(),
                 event_id=read_event_id,
+                hidden=hidden,
             )
 
         read_marker_event_id = body.get("m.fully_read", None)

synapse/rest/client/v2_alpha/receipts.py

@@ -14,8 +14,9 @@
 
 import logging
 
-from synapse.api.errors import SynapseError
-from synapse.http.servlet import RestServlet
+from synapse.api.constants import ReadReceiptEventFields
+from synapse.api.errors import Codes, SynapseError
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
 
 from ._base import client_patterns
 
@@ -42,10 +43,25 @@ async def on_POST(self, request, room_id, receipt_type, event_id):
         if receipt_type != "m.read":
             raise SynapseError(400, "Receipt type must be 'm.read'")
 
+        body = parse_json_object_from_request(request)
+        hidden = body.get(ReadReceiptEventFields.MSC2285_HIDDEN, False)
+
+        if not isinstance(hidden, bool):
+            raise SynapseError(
+                400,
+                "Param %s must be a boolean, if given"
+                % ReadReceiptEventFields.MSC2285_HIDDEN,
+                Codes.BAD_JSON,
+            )
+
         await self.presence_handler.bump_presence_active_time(requester.user)
 
         await self.receipts_handler.received_client_receipt(
-            room_id, receipt_type, user_id=requester.user.to_string(), event_id=event_id
+            room_id,
+            receipt_type,
+            user_id=requester.user.to_string(),
+            event_id=event_id,
+            hidden=hidden,
         )
 
         return 200, {}

synapse/rest/client/versions.py

@@ -82,6 +82,8 @@ def on_GET(self, request):
                     "io.element.e2ee_forced.trusted_private": self.e2ee_forced_trusted_private,
                     # Supports the busy presence state described in MSC3026.
                     "org.matrix.msc3026.busy_presence": self.config.experimental.msc3026_enabled,
+                    # Supports receiving hidden read receipts as per MSC2285
+                    "org.matrix.msc2285": self.config.experimental.msc2285_enabled,
                 },
             },
         )