Use the last olm session that got a message

.travis.yml

@@ -1,5 +1,5 @@
 language: node_js
 node_js:
-    - node # Latest stable version of nodejs.
+    - "10.11.0"
 script:
     - ./travis.sh

src/crypto/OlmDevice.js

@@ -295,8 +295,8 @@ OlmDevice.prototype._storeAccount = function(txn, account) {
  */
 OlmDevice.prototype._getSession = function(deviceKey, sessionId, txn, func) {
     this._cryptoStore.getEndToEndSession(
-        deviceKey, sessionId, txn, (pickledSession) => {
-            this._unpickleSession(pickledSession, func);
+        deviceKey, sessionId, txn, (sessionInfo) => {
+            this._unpickleSession(sessionInfo, func);
         },
     );
 };
@@ -306,15 +306,17 @@ OlmDevice.prototype._getSession = function(deviceKey, sessionId, txn, func) {
  * function with it. The session object is destroyed once the function
  * returns.
  *
- * @param {string} pickledSession
+ * @param {object} sessionInfo
  * @param {function} func
  * @private
  */
-OlmDevice.prototype._unpickleSession = function(pickledSession, func) {
+OlmDevice.prototype._unpickleSession = function(sessionInfo, func) {
     const session = new global.Olm.Session();
     try {
-        session.unpickle(this._pickleKey, pickledSession);
-        func(session);
+        session.unpickle(this._pickleKey, sessionInfo.session);
+        const unpickledSessInfo = Object.assign({}, sessionInfo, {session});
+
+        func(unpickledSessInfo);
     } finally {
         session.free();
     }
@@ -324,14 +326,17 @@ OlmDevice.prototype._unpickleSession = function(pickledSession, func) {
  * store our OlmSession in the session store
  *
  * @param {string} deviceKey
- * @param {OlmSession} session
+ * @param {object} sessionInfo {session: OlmSession, lastReceivedMessageTs: int}
  * @param {*} txn Opaque transaction object from cryptoStore.doTxn()
  * @private
  */
-OlmDevice.prototype._saveSession = function(deviceKey, session, txn) {
-    const pickledSession = session.pickle(this._pickleKey);
+OlmDevice.prototype._saveSession = function(deviceKey, sessionInfo, txn) {
+    const sessionId = sessionInfo.session.session_id();
+    const pickledSessionInfo = Object.assign(sessionInfo, {
+        session: sessionInfo.session.pickle(this._pickleKey),
+    });
     this._cryptoStore.storeEndToEndSession(
-        deviceKey, session.session_id(), pickledSession, txn,
+        deviceKey, sessionId, pickledSessionInfo, txn,
     );
 };
 
@@ -461,7 +466,14 @@ OlmDevice.prototype.createOutboundSession = async function(
                     session.create_outbound(account, theirIdentityKey, theirOneTimeKey);
                     newSessionId = session.session_id();
                     this._storeAccount(txn, account);
-                    this._saveSession(theirIdentityKey, session, txn);
+                    const sessionInfo = {
+                        session,
+                        // Pretend we've received a message at this point, otherwise
+                        // if we try to send a message to the device, it won't use
+                        // this session
+                        lastReceivedMessageTs: Date.now(),
+                    };
+                    this._saveSession(theirIdentityKey, sessionInfo, txn);
                 } finally {
                     session.free();
                 }
@@ -510,7 +522,13 @@ OlmDevice.prototype.createInboundSession = async function(
 
                     const payloadString = session.decrypt(messageType, ciphertext);
 
-                    this._saveSession(theirDeviceIdentityKey, session, txn);
+                    const sessionInfo = {
+                        session,
+                        // this counts as a received message: set last received message time
+                        // to now
+                        lastReceivedMessageTs: Date.now(),
+                    };
+                    this._saveSession(theirDeviceIdentityKey, sessionInfo, txn);
 
                     result = {
                         payload: payloadString,
@@ -558,13 +576,30 @@ OlmDevice.prototype.getSessionIdsForDevice = async function(theirDeviceIdentityK
  * @return {Promise<?string>}  session id, or null if no established session
  */
 OlmDevice.prototype.getSessionIdForDevice = async function(theirDeviceIdentityKey) {
-    const sessionIds = await this.getSessionIdsForDevice(theirDeviceIdentityKey);
-    if (sessionIds.length === 0) {
+    const sessionInfos = await this.getSessionInfoForDevice(theirDeviceIdentityKey);
+    if (sessionInfos.length === 0) {
         return null;
     }
-    // Use the session with the lowest ID.
-    sessionIds.sort();
-    return sessionIds[0];
+    // Use the session that has most recently received a message
+    let idxOfBest = 0;
+    for (let i = 1; i < sessionInfos.length; i++) {
+        const thisSessInfo = sessionInfos[i];
+        const thisLastReceived = thisSessInfo.lastReceivedMessageTs === undefined ?
+            0 : thisSessInfo.lastReceivedMessageTs;
+
+        const bestSessInfo = sessionInfos[idxOfBest];
+        const bestLastReceived = bestSessInfo.lastReceivedMessageTs === undefined ?
+            0 : bestSessInfo.lastReceivedMessageTs;
+        if (
+            thisLastReceived > bestLastReceived || (
+                thisLastReceived === bestLastReceived &&
+                thisSessInfo.sessionId < bestSessInfo.sessionId
+            )
+        ) {
+            idxOfBest = i;
+        }
+    }
+    return sessionInfos[idxOfBest].sessionId;
 };
 
 /**
@@ -587,9 +622,10 @@ OlmDevice.prototype.getSessionInfoForDevice = async function(deviceIdentityKey)
             this._cryptoStore.getEndToEndSessions(deviceIdentityKey, txn, (sessions) => {
                 const sessionIds = Object.keys(sessions).sort();
                 for (const sessionId of sessionIds) {
-                    this._unpickleSession(sessions[sessionId], (session) => {
+                    this._unpickleSession(sessions[sessionId], (sessInfo) => {
                         info.push({
-                            hasReceivedMessage: session.has_received_message(),
+                            lastReceivedMessageTs: sessInfo.lastReceivedMessageTs,
+                            hasReceivedMessage: sessInfo.session.has_received_message(),
                             sessionId: sessionId,
                         });
                     });
@@ -620,9 +656,9 @@ OlmDevice.prototype.encryptMessage = async function(
     await this._cryptoStore.doTxn(
         'readwrite', [IndexedDBCryptoStore.STORE_SESSIONS],
         (txn) => {
-            this._getSession(theirDeviceIdentityKey, sessionId, txn, (session) => {
-                res = session.encrypt(payloadString);
-                this._saveSession(theirDeviceIdentityKey, session, txn);
+            this._getSession(theirDeviceIdentityKey, sessionId, txn, (sessionInfo) => {
+                res = sessionInfo.session.encrypt(payloadString);
+                this._saveSession(theirDeviceIdentityKey, sessionInfo, txn);
             });
         },
     );
@@ -647,9 +683,10 @@ OlmDevice.prototype.decryptMessage = async function(
     await this._cryptoStore.doTxn(
         'readwrite', [IndexedDBCryptoStore.STORE_SESSIONS],
         (txn) => {
-            this._getSession(theirDeviceIdentityKey, sessionId, txn, (session) => {
-                payloadString = session.decrypt(messageType, ciphertext);
-                this._saveSession(theirDeviceIdentityKey, session, txn);
+            this._getSession(theirDeviceIdentityKey, sessionId, txn, (sessionInfo) => {
+                payloadString = sessionInfo.session.decrypt(messageType, ciphertext);
+                sessionInfo.lastReceivedMessageTs = Date.now();
+                this._saveSession(theirDeviceIdentityKey, sessionInfo, txn);
             });
         },
     );
@@ -679,8 +716,8 @@ OlmDevice.prototype.matchesSession = async function(
     await this._cryptoStore.doTxn(
         'readonly', [IndexedDBCryptoStore.STORE_SESSIONS],
         (txn) => {
-            this._getSession(theirDeviceIdentityKey, sessionId, txn, (session) => {
-                matches = session.matches_inbound(ciphertext);
+            this._getSession(theirDeviceIdentityKey, sessionId, txn, (sessionInfo) => {
+                matches = sessionInfo.session.matches_inbound(ciphertext);
             });
         },
     );

src/crypto/store/indexeddb-crypto-store-backend.js

@@ -314,7 +314,10 @@ export class Backend {
         getReq.onsuccess = function() {
             const cursor = getReq.result;
             if (cursor) {
-                results[cursor.value.sessionId] = cursor.value.session;
+                results[cursor.value.sessionId] = {
+                    session: cursor.value.session,
+                    lastReceivedMessageTs: cursor.value.lastReceivedMessageTs,
+                };
                 cursor.continue();
             } else {
                 try {
@@ -332,7 +335,10 @@ export class Backend {
         getReq.onsuccess = function() {
             try {
                 if (getReq.result) {
-                    func(getReq.result.session);
+                    func({
+                        session: getReq.result.session,
+                        lastReceivedMessageTs: getReq.result.lastReceivedMessageTs,
+                    });
                 } else {
                     func(null);
                 }
@@ -342,9 +348,14 @@ export class Backend {
         };
     }
 
-    storeEndToEndSession(deviceKey, sessionId, session, txn) {
+    storeEndToEndSession(deviceKey, sessionId, sessionInfo, txn) {
         const objectStore = txn.objectStore("sessions");
-        objectStore.put({deviceKey, sessionId, session});
+        objectStore.put({
+            deviceKey,
+            sessionId,
+            session: sessionInfo.session,
+            lastReceivedMessageTs: sessionInfo.lastReceivedMessageTs,
+        });
     }
 
     // Inbound group sessions

src/crypto/store/indexeddb-crypto-store.js

@@ -284,7 +284,10 @@ export default class IndexedDBCryptoStore {
      * @param {string} sessionId The ID of the session to retrieve
      * @param {*} txn An active transaction. See doTxn().
      * @param {function(object)} func Called with A map from sessionId
-     *     to Base64 end-to-end session.
+     *     to session information object with 'session' key being the
+     *     Base64 end-to-end session and lastReceivedMessageTs being the
+     *     timestamp in milliseconds at which the session last received
+     *     a message.
      */
     getEndToEndSession(deviceKey, sessionId, txn, func) {
         this._backendPromise.value().getEndToEndSession(deviceKey, sessionId, txn, func);
@@ -296,7 +299,10 @@ export default class IndexedDBCryptoStore {
      * @param {string} deviceKey The public key of the other device.
      * @param {*} txn An active transaction. See doTxn().
      * @param {function(object)} func Called with A map from sessionId
-     *     to Base64 end-to-end session.
+     *     to session information object with 'session' key being the
+     *     Base64 end-to-end session and lastReceivedMessageTs being the
+     *     timestamp in milliseconds at which the session last received
+     *     a message.
      */
     getEndToEndSessions(deviceKey, txn, func) {
         this._backendPromise.value().getEndToEndSessions(deviceKey, txn, func);
@@ -306,12 +312,12 @@ export default class IndexedDBCryptoStore {
      * Store a session between the logged-in user and another device
      * @param {string} deviceKey The public key of the other device.
      * @param {string} sessionId The ID for this end-to-end session.
-     * @param {string} session Base64 encoded end-to-end session.
+     * @param {string} sessionInfo Session information object
      * @param {*} txn An active transaction. See doTxn().
      */
-    storeEndToEndSession(deviceKey, sessionId, session, txn) {
+    storeEndToEndSession(deviceKey, sessionId, sessionInfo, txn) {
         this._backendPromise.value().storeEndToEndSession(
-            deviceKey, sessionId, session, txn,
+            deviceKey, sessionId, sessionInfo, txn,
         );
     }
 

src/crypto/store/localStorage-crypto-store.js

@@ -67,7 +67,21 @@ export default class LocalStorageCryptoStore extends MemoryCryptoStore {
     }
 
     _getEndToEndSessions(deviceKey, txn, func) {
-        return getJsonItem(this.store, keyEndToEndSessions(deviceKey));
+        const sessions = getJsonItem(this.store, keyEndToEndSessions(deviceKey));
+        const fixedSessions = {};
+
+        // fix up any old sessions to be objects rather than just the base64 pickle
+        for (const [sid, val] of Object.entries(sessions || {})) {
+            if (typeof val === 'string') {
+                fixedSessions[sid] = {
+                    session: val,
+                };
+            } else {
+                fixedSessions[sid] = val;
+            }
+        }
+
+        return fixedSessions;
     }
 
     getEndToEndSession(deviceKey, sessionId, txn, func) {
@@ -79,9 +93,9 @@ export default class LocalStorageCryptoStore extends MemoryCryptoStore {
         func(this._getEndToEndSessions(deviceKey) || {});
     }
 
-    storeEndToEndSession(deviceKey, sessionId, session, txn) {
+    storeEndToEndSession(deviceKey, sessionId, sessionInfo, txn) {
         const sessions = this._getEndToEndSessions(deviceKey) || {};
-        sessions[sessionId] = session;
+        sessions[sessionId] = sessionInfo;
         setJsonItem(
             this.store, keyEndToEndSessions(deviceKey), sessions,
         );

src/crypto/store/memory-crypto-store.js

@@ -234,13 +234,13 @@ export default class MemoryCryptoStore {
         func(this._sessions[deviceKey] || {});
     }
 
-    storeEndToEndSession(deviceKey, sessionId, session, txn) {
+    storeEndToEndSession(deviceKey, sessionId, sessionInfo, txn) {
         let deviceSessions = this._sessions[deviceKey];
         if (deviceSessions === undefined) {
             deviceSessions = {};
             this._sessions[deviceKey] = deviceSessions;
         }
-        deviceSessions[sessionId] = session;
+        deviceSessions[sessionId] = sessionInfo;
     }
 
     // Inbound Group Sessions