feat(base): Remember when a user explicitly accepted an invite

crates/matrix-sdk-base/CHANGELOG.md

@@ -6,6 +6,13 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased] - ReleaseDate
 
+### Features
+- The `RoomInfo` now remembers when an invite was explicitly accepted when the
+  `BaseClient::room_joined()` method was called. A new getter for this
+  timestamp exists, the `RoomInfo::invite_accepted_at()` method returns this
+  timestamp.
+  ([#5333](https://github.com/matrix-org/matrix-rust-sdk/pull/5333))
+
 ### Refactor
 
 - The cached `ServerCapabilities` has been renamed to `ServerInfo` and

crates/matrix-sdk-base/src/client.rs

@@ -459,12 +459,30 @@ impl BaseClient {
             let _sync_lock = self.sync_lock().lock().await;
 
             let mut room_info = room.clone_info();
+
+            // If our previous state was an invite and we're now in the joined state, this
+            // means that the user has explicitly accepted the invite. Let's
+            // remember when this has happened.
+            //
+            // This is somewhat of a workaround for our lack of cryptographic membership.
+            // Later on we will decide if historic room keys should be accepted
+            // based on this info. If a user has accepted an invite and we receive a room
+            // key bundle shortly after, we might accept it. If we don't do
+            // this, the homeserver could trick us into accepting any historic room key
+            // bundle.
+            if room.state() == RoomState::Invited {
+                room_info.set_invite_accepted_now();
+            }
+
             room_info.mark_as_joined();
             room_info.mark_state_partially_synced();
             room_info.mark_members_missing(); // the own member event changed
+
             let mut changes = StateChanges::default();
             changes.add_room(room_info.clone());
+
             self.state_store.save_changes(&changes).await?; // Update the store
+
             room.set_room_info(room_info, RoomInfoNotableUpdateReasons::MEMBERSHIP);
         }
 

crates/matrix-sdk-base/src/room/room_info.rs

@@ -46,8 +46,8 @@ use ruma::{
     },
     room::RoomType,
     serde::Raw,
-    EventId, MxcUri, OwnedEventId, OwnedMxcUri, OwnedRoomAliasId, OwnedRoomId, OwnedUserId,
-    RoomAliasId, RoomId, RoomVersionId, UserId,
+    EventId, MilliSecondsSinceUnixEpoch, MxcUri, OwnedEventId, OwnedMxcUri, OwnedRoomAliasId,
+    OwnedRoomId, OwnedUserId, RoomAliasId, RoomId, RoomVersionId, UserId,
 };
 use serde::{Deserialize, Serialize};
 use tracing::{debug, field::debug, info, instrument, warn};
@@ -464,6 +464,14 @@ pub struct RoomInfo {
     /// more accurate than relying on the latest event.
     #[serde(default)]
     pub(crate) recency_stamp: Option<u64>,
+
+    /// A timestamp remembering when we observed the user accepting an invite on
+    /// this current device.
+    ///
+    /// This is useful to remember if the user accepted this a join on this
+    /// specific client.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub(crate) invite_accepted_at: Option<MilliSecondsSinceUnixEpoch>,
 }
 
 impl RoomInfo {
@@ -486,6 +494,7 @@ impl RoomInfo {
             cached_display_name: None,
             cached_user_defined_notification_mode: None,
             recency_stamp: None,
+            invite_accepted_at: None,
         }
     }
 
@@ -749,6 +758,22 @@ impl RoomInfo {
         self.summary.invited_member_count = count;
     }
 
+    /// Mark that the user has accepted an invite and remember when this has
+    /// happened using a timestamp set to [`MilliSecondsSinceUnixEpoch::now()`].
+    pub(crate) fn set_invite_accepted_now(&mut self) {
+        self.invite_accepted_at = Some(MilliSecondsSinceUnixEpoch::now());
+    }
+
+    /// Returns the timestamp when an invite to this room has been accepted by
+    /// this specific client.
+    ///
+    /// # Returns
+    /// - `Some` if the invite has been accepted by this specific client.
+    /// - `None` if the invite has not been accepted
+    pub fn invite_accepted_at(&self) -> Option<MilliSecondsSinceUnixEpoch> {
+        self.invite_accepted_at
+    }
+
     /// Updates the room heroes.
     pub(crate) fn update_heroes(&mut self, heroes: Vec<RoomHero>) {
         self.summary.room_heroes = heroes;
@@ -1173,6 +1198,7 @@ mod tests {
         owned_mxc_uri, owned_user_id, room_id, serde::Raw,
     };
     use serde_json::json;
+    use similar_asserts::assert_eq;
 
     use super::{BaseRoomInfo, RoomInfo, SyncInfo};
     use crate::{
@@ -1221,6 +1247,7 @@ mod tests {
             cached_display_name: None,
             cached_user_defined_notification_mode: None,
             recency_stamp: Some(42),
+            invite_accepted_at: None,
         };
 
         let info_json = json!({

crates/matrix-sdk-base/src/store/migration_helpers.rs

@@ -121,6 +121,7 @@ impl RoomInfoV1 {
             cached_display_name: None,
             cached_user_defined_notification_mode: None,
             recency_stamp: None,
+            invite_accepted_at: None,
         }
     }
 }