WIP

Author: andybalaam

crates/matrix-sdk-crypto/src/olm/group_sessions/inbound.rs

@@ -38,7 +38,8 @@ use vodozemac::{
 };
 
 use super::{
-    BackedUpRoomKey, ExportedRoomKey, OutboundGroupSession, SessionCreationError, SessionKey,
+    inbound_group_session_sender_data::InboundGroupSessionSenderData, BackedUpRoomKey,
+    ExportedRoomKey, OutboundGroupSession, SessionCreationError, SessionKey,
 };
 use crate::{
     error::{EventError, MegolmResult},
@@ -123,6 +124,12 @@ pub struct InboundGroupSession {
     /// on how the session was received.
     pub(crate) creator_info: SessionCreatorInfo,
 
+    /// Information about the sender of this session and how much we trust that
+    /// information. Holds the information we have about the device that created
+    /// the session, or, if we can use that device information to find the
+    /// sender's cross-signing identity, holds the user ID and cross-signing key.
+    pub(crate) sender_data: InboundGroupSessionSenderData,
+
     /// The Room this GroupSession belongs to
     pub room_id: OwnedRoomId,
 

crates/matrix-sdk-crypto/src/olm/group_sessions/inbound_group_session_sender_data.rs

@@ -0,0 +1,82 @@
+// Copyright 2022 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.
+
+use std::time::SystemTime;
+
+use ruma::OwnedUserId;
+use vodozemac::Ed25519PublicKey;
+
+use crate::types::DeviceKeys;
+
+/// Information on the device and user that sent the megolm session data to us
+///
+/// Sessions start off in `UnknownDevice` state, and progress into `DeviceInfo`
+/// state when we get the device info. Finally, if we can look up the sender
+/// using the device info, the session can be moved into `SenderKnown` state.
+#[derive(Clone)]
+pub(crate) enum InboundGroupSessionSenderData {
+    /// We have not yet found the (signed) device info for the sending device
+    UnknownDevice {
+        // TODO: we may need to handle unsigned and unknown devices separately, which
+        // probably necessitates a flag here
+        /// When we will next try again to find device info for this session,
+        /// and how many times we have tried
+        retry_details: RetryDetails,
+
+        /// Was this session created before we started collecting trust
+        /// information about sessions? If so, we may choose to display its
+        /// messages even though trust info is missing.
+        legacy_session: bool,
+    },
+
+    /// We have the signed device info for the sending device, but not yet the
+    /// cross-signing key that it was signed with.
+    DeviceInfo {
+        /// Information about the device that sent the to-device message creating
+        /// this session.
+        device_keys: DeviceKeys,
+        /// When we will next try again to find a cross-signing key that signed
+        /// the device information, and how many times we have tried.
+        retry_details: RetryDetails,
+
+        /// Was this session created before we started collecting trust
+        /// information about sessions? If so, we may choose to display its
+        /// messages even though trust info is missing.
+        legacy_session: bool,
+    },
+
+    /// We have found proof that this user, with this cross-signing key, sent
+    /// the to-device message that established this session.
+    SenderKnown {
+        /// The user ID of the user who established this session.
+        user_id: OwnedUserId,
+
+        /// The cross-signing key of the user who established this session.
+        msk: Ed25519PublicKey,
+
+        /// Whether, at the time we checked the signature on the device,
+        /// we had actively verified that `msk` belongs to the user.
+        /// If false, we had simply accepted the key as this user's latest
+        /// key.
+        msk_verified: bool,
+    },
+}
+
+/// Tracking information about when we need to try again fetching device or
+/// user information, and how many times we have already tried.
+#[derive(Clone)]
+pub(crate) struct RetryDetails {
+    retry_count: u8,
+    next_retry_time: SystemTime,
+}

crates/matrix-sdk-crypto/src/olm/group_sessions/mod.rs

@@ -16,6 +16,7 @@ use ruma::{DeviceKeyAlgorithm, OwnedRoomId};
 use serde::{Deserialize, Serialize};
 
 mod inbound;
+mod inbound_group_session_sender_data;
 mod outbound;
 
 pub use inbound::{InboundGroupSession, PickledInboundGroupSession};