feat: Add forwarder: ForwarderInfo to EncryptionInfo.

crates/matrix-sdk-base/src/event_cache/store/integration_tests.rs

@@ -79,6 +79,7 @@ pub fn make_test_event_with_event_id(
     let encryption_info = Arc::new(EncryptionInfo {
         sender: (*ALICE).into(),
         sender_device: None,
+        forwarder: None,
         algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
             curve25519_key: "1337".to_owned(),
             sender_claimed_keys: Default::default(),

crates/matrix-sdk-common/CHANGELOG.md

@@ -14,6 +14,8 @@ All notable changes to this project will be documented in this file.
 
 ### Features
 
+- Add field `forwarder` of type `ForwarderInfo` to `EncryptionInfo`, which which exposes information about the forwarder of the  keys with which an event was encrypted if they were shared as part of an [MSC4268](https://github.com/matrix-org/matrix-spec-proposals/pull/4268) room key bundle.
+  ([#5945](https://github.com/matrix-org/matrix-rust-sdk/pull/5945)).
 - [**breaking**] Cross-process lock can be dirty. The `CrossProcess::try_lock_once` now returns a new type `CrossProcessResult`, which is an enum with `Clean`, `Dirty` or `Unobtained` variants. When the lock is dirty it means it's been acquired once, then acquired another time from another holder, so the current holder may want to refresh its internal state.
   ([#5672](https://github.com/matrix-org/matrix-rust-sdk/pull/5672)).
 

crates/matrix-sdk-common/src/deserialized_responses.rs

@@ -319,6 +319,16 @@ pub enum AlgorithmInfo {
     },
 }
 
+/// Struct containing information on the forwarder of the keys used to decrypt
+/// an event.
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct ForwarderInfo {
+    /// The user ID of the forwarder.
+    pub user_id: OwnedUserId,
+    /// The device ID of the forwarder.
+    pub device_id: OwnedDeviceId,
+}
+
 /// Struct containing information on how an event was decrypted.
 #[derive(Clone, Debug, PartialEq, Serialize)]
 pub struct EncryptionInfo {
@@ -328,6 +338,11 @@ pub struct EncryptionInfo {
     /// The device ID of the device that sent us the event, note this is
     /// untrusted data unless `verification_state` is `Verified` as well.
     pub sender_device: Option<OwnedDeviceId>,
+    /// If the keys for this message were shared-on-invite as part of an
+    /// [MSC4268] key bundle, information about the forwarder.
+    ///
+    /// [MSC4268]: https://github.com/matrix-org/matrix-spec-proposals/pull/4268
+    pub forwarder: Option<ForwarderInfo>,
     /// Information about the algorithm that was used to encrypt the event.
     pub algorithm_info: AlgorithmInfo,
     /// The verification state of the device that sent us the event, note this
@@ -361,14 +376,21 @@ impl<'de> Deserialize<'de> for EncryptionInfo {
         struct Helper {
             pub sender: OwnedUserId,
             pub sender_device: Option<OwnedDeviceId>,
+            pub forwarder: Option<ForwarderInfo>,
             pub algorithm_info: AlgorithmInfo,
             pub verification_state: VerificationState,
             #[serde(rename = "session_id")]
             pub old_session_id: Option<String>,
         }
 
-        let Helper { sender, sender_device, algorithm_info, verification_state, old_session_id } =
-            Helper::deserialize(deserializer)?;
+        let Helper {
+            sender,
+            sender_device,
+            forwarder,
+            algorithm_info,
+            verification_state,
+            old_session_id,
+        } = Helper::deserialize(deserializer)?;
 
         let algorithm_info = match algorithm_info {
             AlgorithmInfo::MegolmV1AesSha2 { curve25519_key, sender_claimed_keys, session_id } => {
@@ -382,7 +404,7 @@ impl<'de> Deserialize<'de> for EncryptionInfo {
             other => other,
         };
 
-        Ok(EncryptionInfo { sender, sender_device, algorithm_info, verification_state })
+        Ok(EncryptionInfo { sender, sender_device, forwarder, algorithm_info, verification_state })
     }
 }
 
@@ -1617,6 +1639,7 @@ mod tests {
                 encryption_info: Arc::new(EncryptionInfo {
                     sender: user_id!("@sender:example.com").to_owned(),
                     sender_device: None,
+                    forwarder: None,
                     algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
                         curve25519_key: "xxx".to_owned(),
                         sender_claimed_keys: Default::default(),
@@ -1657,6 +1680,7 @@ mod tests {
                         "encryption_info": {
                             "sender": "@sender:example.com",
                             "sender_device": null,
+                            "forwarder": null,
                             "algorithm_info": {
                                 "MegolmV1AesSha2": {
                                     "curve25519_key": "xxx",
@@ -2041,6 +2065,7 @@ mod tests {
         let info = EncryptionInfo {
             sender: user_id!("@alice:localhost").to_owned(),
             sender_device: Some(device_id!("ABCDEFGH").to_owned()),
+            forwarder: None,
             algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
                 curve25519_key: "curvecurvecurve".into(),
                 sender_claimed_keys: Default::default(),
@@ -2062,6 +2087,7 @@ mod tests {
                 encryption_info: Arc::new(EncryptionInfo {
                     sender: user_id!("@sender:example.com").to_owned(),
                     sender_device: Some(device_id!("ABCDEFGHIJ").to_owned()),
+                    forwarder: None,
                     algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
                         curve25519_key: "xxx".to_owned(),
                         sender_claimed_keys: BTreeMap::from([

crates/matrix-sdk-common/src/snapshots/matrix_sdk_common__deserialized_responses__tests__encryption_info_migration.snap

@@ -5,6 +5,7 @@ expression: deserialized
 {
   "sender": "@alice:localhost",
   "sender_device": "ABCDEFGH",
+  "forwarder": null,
   "algorithm_info": {
     "MegolmV1AesSha2": {
       "curve25519_key": "curvecurvecurve",

crates/matrix-sdk-common/src/snapshots/snapshot_test_encryption_info.snap

@@ -5,6 +5,7 @@ expression: info
 {
   "sender": "@alice:localhost",
   "sender_device": "ABCDEFGH",
+  "forwarder": null,
   "algorithm_info": {
     "MegolmV1AesSha2": {
       "curve25519_key": "curvecurvecurve",

crates/matrix-sdk-common/src/snapshots/snapshot_test_sync_timeline_event.snap

@@ -16,6 +16,7 @@ expression: "serde_json::to_value(&room_event).unwrap()"
             "session_id": "mysessionid112"
           }
         },
+        "forwarder": null,
         "sender": "@sender:example.com",
         "sender_device": "ABCDEFGHIJ",
         "verification_state": "Verified"

crates/matrix-sdk-crypto/CHANGELOG.md

@@ -8,6 +8,8 @@ All notable changes to this project will be documented in this file.
 
 ### Features
 
+- Added a new field `forwarder` to `InboundGroupSession` of type `ForwarderData`, which stores information about the forwarder of a session shared in a room key bundle under [MSC4268](https://github.com/matrix-org/matrix-spec-proposals/pull/4268).
+  ([#5980])(https://github.com/matrix-org/matrix-rust-sdk/pull/5980)
 - The `OutboundGroupSession` and `OlmMachine` now return the `EncryptionInfo` 
   used when encrypting raw events.
   ([#5936](https://github.com/matrix-org/matrix-rust-sdk/pull/5936))

crates/matrix-sdk-crypto/src/machine/mod.rs

@@ -26,7 +26,7 @@ use matrix_sdk_common::deserialized_responses::WithheldCode;
 use matrix_sdk_common::{
     BoxFuture,
     deserialized_responses::{
-        AlgorithmInfo, DecryptedRoomEvent, DeviceLinkProblem, EncryptionInfo,
+        AlgorithmInfo, DecryptedRoomEvent, DeviceLinkProblem, EncryptionInfo, ForwarderInfo,
         ProcessedToDeviceEvent, ToDeviceUnableToDecryptInfo, ToDeviceUnableToDecryptReason,
         UnableToDecryptInfo, UnableToDecryptReason, UnsignedDecryptionResult,
         UnsignedEventLocation, VerificationLevel, VerificationState,
@@ -1136,6 +1136,7 @@ impl OlmMachine {
         EncryptionInfo {
             sender: self.inner.user_id.clone(),
             sender_device: Some(self.inner.device_id.clone()),
+            forwarder: None,
             algorithm_info,
             verification_state: VerificationState::Verified,
         }
@@ -2016,11 +2017,18 @@ impl OlmMachine {
         let (verification_state, device_id) =
             self.get_room_event_verification_state(session, sender).await?;
 
-        let sender = sender.to_owned();
-
         Ok(Arc::new(EncryptionInfo {
-            sender,
+            sender: sender.to_owned(),
             sender_device: device_id,
+            forwarder: session.forwarder_data.as_ref().and_then(|data| {
+                // Per the comment on `KnownSenderData::device_id`, we should never encounter a
+                // `None` value here, but must still deal with an `Optional` for backwards
+                // compatibility. The approach below allows us to avoid unwrapping.
+                data.device_id().map(|device_id| ForwarderInfo {
+                    device_id: device_id.to_owned(),
+                    user_id: data.user_id().to_owned(),
+                })
+            }),
             algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
                 curve25519_key: session.sender_key().to_base64(),
                 sender_claimed_keys: session

crates/matrix-sdk-crypto/src/olm/account.rs

@@ -1704,6 +1704,7 @@ impl Account {
         EncryptionInfo {
             sender: sender_id.to_owned(),
             sender_device: sender_device.as_ref().map(|d| d.device_id().to_owned()),
+            forwarder: None,
             algorithm_info: AlgorithmInfo::OlmV1Curve25519AesSha2 {
                 curve25519_public_key_base64: sender_key.to_base64(),
             },

crates/matrix-sdk-ui/src/timeline/controller/decryption_retry_task.rs

@@ -296,6 +296,7 @@ mod tests {
             encryption_info: Some(Arc::new(EncryptionInfo {
                 sender: owned_user_id!("@u:s.co"),
                 sender_device: None,
+                forwarder: None,
                 algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
                     curve25519_key: "".to_owned(),
                     sender_claimed_keys: BTreeMap::new(),

crates/matrix-sdk-ui/src/timeline/tests/edit.rs

@@ -163,6 +163,7 @@ async fn test_edit_updates_encryption_info() {
     let mut encryption_info = Arc::new(EncryptionInfo {
         sender: (*ALICE).into(),
         sender_device: None,
+        forwarder: None,
         algorithm_info: AlgorithmInfo::MegolmV1AesSha2 {
             curve25519_key: "123".to_owned(),
             sender_claimed_keys: BTreeMap::new(),

crates/matrix-sdk/tests/integration/encryption/shared_history.rs

@@ -195,6 +195,13 @@ async fn test_shared_history_out_of_order() {
         .await
         .expect("Bob should be able to fetch the event Alice has sent");
 
+    let encryption_info = event.encryption_info().expect("Event did not have encryption info");
+
+    // Check Bob stored information about the key forwarder.
+    let forwarder_info = encryption_info.forwarder.as_ref().unwrap();
+    assert_eq!(forwarder_info.user_id, alice_user_id);
+    assert_eq!(forwarder_info.device_id, alice_device_id);
+
     assert_decrypted_message_eq!(
         event,
         "It's a secret to everybody",