Merge branch 'e2e_backups' of git://github.com/uhoreg/matrix-js-sdk into uhoreg-e2e_backups

src/crypto/algorithms/megolm.js

@@ -814,7 +814,7 @@ MegolmDecryption.prototype.onRoomKeyEvent = function(event) {
     }
 
     console.log(`Adding key for megolm session ${senderKey}|${sessionId}`);
-    this._olmDevice.addInboundGroupSession(
+    return this._olmDevice.addInboundGroupSession(
         content.room_id, senderKey, forwardingKeyChain, sessionId,
         content.session_key, keysClaimed,
         exportFormat,
@@ -829,6 +829,12 @@ MegolmDecryption.prototype.onRoomKeyEvent = function(event) {
 
         // have another go at decrypting events sent with this session.
         this._retryDecryption(senderKey, sessionId);
+    }).then(() => {
+        return this.backupGroupSession(
+            content.room_id, senderKey, forwardingKeyChain,
+            content.session_id, content.session_key, keysClaimed,
+            exportFormat,
+        );
     }).catch((e) => {
         console.error(`Error handling m.room_key_event: ${e}`);
     });
@@ -951,6 +957,54 @@ MegolmDecryption.prototype.importRoomKey = function(session) {
     });
 };
 
+MegolmDecryption.prototype.backupGroupSession = async function(
+    roomId, senderKey, forwardingCurve25519KeyChain,
+    sessionId, sessionKey, keysClaimed,
+    exportFormat,
+) {
+    // new session.
+    const session = new Olm.InboundGroupSession();
+    let first_known_index;
+    try {
+        if (exportFormat) {
+            session.import_session(sessionKey);
+        } else {
+            session.create(sessionKey);
+        }
+        if (sessionId != session.session_id()) {
+            throw new Error(
+                "Mismatched group session ID from senderKey: " +
+                    senderKey,
+            );
+        }
+
+        if (!exportFormat) {
+            sessionKey = session.export_session();
+        }
+        const first_known_index = session.first_known_index();
+
+        const sessionData = {
+            algorithm: olmlib.MEGOLM_ALGORITHM,
+            sender_key: senderKey,
+            sender_claimed_keys: keysClaimed,
+            forwardingCurve25519KeyChain: forwardingCurve25519KeyChain,
+            session_key: sessionKey
+        };
+        const encrypted = this._crypto.backupKey.encrypt(JSON.stringify(sessionData));
+        const data = {
+            first_message_index: first_known_index,
+            forwarded_count: forwardingCurve25519KeyChain.length,
+            is_verified: false, // FIXME: how do we determine this?
+            session_data: encrypted
+        };
+        return this._baseApis.sendKeyBackup(roomId, sessionId, data);
+    } catch (e) {
+        return Promise.reject(e);
+    } finally {
+        session.free();
+    }
+}
+
 /**
  * Have another go at decrypting events after we receive a key
  *