refactor(crypto): Use the vodozemac method to decide if a session is better

This patch delegates the decision making if a session is better to
vodozemac. Vodozemac has better insights if a group session can be
considered to be better.

bindings/matrix-sdk-crypto-ffi/Cargo.toml

@@ -57,7 +57,7 @@ features = ["rt-multi-thread"]
 
 [dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"
 
 [build-dependencies]
 uniffi_build = { version = "0.18.0", features = ["builtin-bindgen"] }

bindings/matrix-sdk-crypto-js/Cargo.toml

@@ -41,5 +41,5 @@ tracing-subscriber = { version = "0.3.14", default-features = false, features =
 
 [dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"
 features = ["js"]

bindings/matrix-sdk-crypto-nodejs/Cargo.toml

@@ -36,7 +36,7 @@ tracing-subscriber = { version = "0.3", default-features = false, features = ["t
 
 [dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"
 features = ["js"]
 
 [build-dependencies]

crates/matrix-sdk-crypto/Cargo.toml

@@ -62,11 +62,11 @@ features = ["client-api-c", "rand", "canonical-json", "unstable-msc2676", "unsta
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"
 features = ["js"]
 
 [dev-dependencies]

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

@@ -36,7 +36,7 @@ use ruma::{
     OwnedUserId, RoomId, TransactionId, UserId,
 };
 use tracing::{debug, info, trace, warn};
-use vodozemac::Curve25519PublicKey;
+use vodozemac::{megolm::SessionOrdering, Curve25519PublicKey};
 
 use super::{GossipRequest, KeyForwardDecision, RequestEvent, RequestInfo, SecretInfo, WaitQueue};
 use crate::{
@@ -899,10 +899,7 @@ impl GossipMachine {
                 // If we have a previous session, check if we have a better version
                 // and store the new one if so.
                 let session = if let Some(old_session) = old_session {
-                    let first_old_index = old_session.first_known_index();
-                    let first_index = session.first_known_index();
-
-                    if first_old_index > first_index {
+                    if session.compare(&old_session).await == SessionOrdering::Better {
                         self.mark_as_done(info).await?;
                         Some(session)
                     } else {

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

@@ -43,7 +43,7 @@ use ruma::{
 };
 use serde_json::{value::to_raw_value, Value};
 use tracing::{debug, error, info, trace, warn};
-use vodozemac::{Curve25519PublicKey, Ed25519Signature};
+use vodozemac::{megolm::SessionOrdering, Curve25519PublicKey, Ed25519Signature};
 
 #[cfg(feature = "backups_v1")]
 use crate::backups::BackupMachine;
@@ -1330,45 +1330,18 @@ impl OlmMachine {
         #[allow(unused_variables)] from_backup: bool,
         progress_listener: impl Fn(usize, usize),
     ) -> StoreResult<RoomKeyImportResult> {
-        type SessionIdToIndexMap = BTreeMap<Arc<str>, u32>;
-
-        #[derive(Debug)]
-        struct ShallowSessions {
-            inner: BTreeMap<Arc<RoomId>, BTreeMap<String, SessionIdToIndexMap>>,
-        }
-
-        impl ShallowSessions {
-            fn has_better_session(&self, session: &InboundGroupSession) -> bool {
-                self.inner
-                    .get(&session.room_id)
-                    .and_then(|m| {
-                        m.get(&session.sender_key.to_base64()).and_then(|m| {
-                            m.get(&session.session_id)
-                                .map(|existing| existing <= &session.first_known_index())
-                        })
-                    })
-                    .unwrap_or(false)
-            }
-        }
-
         let mut sessions = Vec::new();
 
-        let existing_sessions = ShallowSessions {
-            inner: self.store.get_inbound_group_sessions().await?.into_iter().fold(
-                BTreeMap::new(),
-                |mut acc, s| {
-                    let index = s.first_known_index();
-
-                    acc.entry(s.room_id)
-                        .or_default()
-                        .entry(s.sender_key.to_base64())
-                        .or_default()
-                        .insert(s.session_id, index);
-
-                    acc
-                },
-            ),
-        };
+        async fn new_session_better(
+            session: &InboundGroupSession,
+            old_session: Option<InboundGroupSession>,
+        ) -> bool {
+            if let Some(old_session) = &old_session {
+                session.compare(old_session).await == SessionOrdering::Better
+            } else {
+                true
+            }
+        }
 
         let total_count = exported_keys.len();
         let mut keys = BTreeMap::new();
@@ -1376,10 +1349,18 @@ impl OlmMachine {
         for (i, key) in exported_keys.into_iter().enumerate() {
             match InboundGroupSession::from_export(&key) {
                 Ok(session) => {
-                    // Only import the session if we didn't have this session or if it's
-                    // a better version of the same session, that is the first known
-                    // index is lower.
-                    if !existing_sessions.has_better_session(&session) {
+                    let old_session = self
+                        .store
+                        .get_inbound_group_session(
+                            session.room_id(),
+                            &session.sender_key.to_base64(),
+                            session.session_id(),
+                        )
+                        .await?;
+
+                    // Only import the session if we didn't have this session or
+                    // if it's a better version of the same session.
+                    if new_session_better(&session, old_session).await {
                         #[cfg(feature = "backups_v1")]
                         if from_backup {
                             session.mark_as_backed_up();

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

@@ -35,7 +35,7 @@ use serde_json::Value;
 use vodozemac::{
     megolm::{
         DecryptedMessage, DecryptionError, ExportedSessionKey, InboundGroupSession as InnerSession,
-        InboundGroupSessionPickle, MegolmMessage,
+        InboundGroupSessionPickle, MegolmMessage, SessionOrdering,
     },
     Curve25519PublicKey, PickleError,
 };
@@ -330,6 +330,13 @@ impl InboundGroupSession {
         self.first_known_index
     }
 
+    /// Check if the `InboundGroupSession` is better than the given other
+    /// `InboundGroupSession`
+    pub async fn compare(&self, other: &InboundGroupSession) -> SessionOrdering {
+        let mut other = other.inner.lock().await;
+        self.inner.lock().await.compare(&mut other)
+    }
+
     /// Decrypt the given ciphertext.
     ///
     /// Returns the decrypted plaintext or an `DecryptionError` if

crates/matrix-sdk-qrcode/Cargo.toml

@@ -30,4 +30,4 @@ thiserror = "1.0.30"
 
 [dependencies.vodozemac]
 git = "https://github.com/matrix-org/vodozemac/"
-rev = "18bcbc3359298894415931547ea41abb75af2d4a"
+rev = "779e85258ec83b10ae62ec4d848188b188aa7b42"