Try to load keys from key backup when a message fails to decrypt (#2373)

Co-authored-by: Travis Ralston <travisr@matrix.org>

spec/TestClient.js

@@ -1,238 +0,0 @@
-/*
-Copyright 2016 OpenMarket Ltd
-Copyright 2017 Vector Creations Ltd
-Copyright 2018-2019 New Vector Ltd
-
-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.
-*/
-
-// load olm before the sdk if possible
-import './olm-loader';
-
-import MockHttpBackend from 'matrix-mock-request';
-
-import { LocalStorageCryptoStore } from '../src/crypto/store/localStorage-crypto-store';
-import { logger } from '../src/logger';
-import { WebStorageSessionStore } from "../src/store/session/webstorage";
-import { syncPromise } from "./test-utils/test-utils";
-import { createClient } from "../src/matrix";
-import { MockStorageApi } from "./MockStorageApi";
-
-/**
- * Wrapper for a MockStorageApi, MockHttpBackend and MatrixClient
- *
- * @constructor
- * @param {string} userId
- * @param {string} deviceId
- * @param {string} accessToken
- *
- * @param {WebStorage=} sessionStoreBackend a web storage object to use for the
- *     session store. If undefined, we will create a MockStorageApi.
- * @param {object} options additional options to pass to the client
- */
-export function TestClient(
-    userId, deviceId, accessToken, sessionStoreBackend, options,
-) {
-    this.userId = userId;
-    this.deviceId = deviceId;
-
-    if (sessionStoreBackend === undefined) {
-        sessionStoreBackend = new MockStorageApi();
-    }
-    const sessionStore = new WebStorageSessionStore(sessionStoreBackend);
-
-    this.httpBackend = new MockHttpBackend();
-
-    options = Object.assign({
-        baseUrl: "http://" + userId + ".test.server",
-        userId: userId,
-        accessToken: accessToken,
-        deviceId: deviceId,
-        sessionStore: sessionStore,
-        request: this.httpBackend.requestFn,
-    }, options);
-    if (!options.cryptoStore) {
-        // expose this so the tests can get to it
-        this.cryptoStore = new LocalStorageCryptoStore(sessionStoreBackend);
-        options.cryptoStore = this.cryptoStore;
-    }
-    this.client = createClient(options);
-
-    this.deviceKeys = null;
-    this.oneTimeKeys = {};
-    this.callEventHandler = {
-        calls: new Map(),
-    };
-}
-
-TestClient.prototype.toString = function() {
-    return 'TestClient[' + this.userId + ']';
-};
-
-/**
- * start the client, and wait for it to initialise.
- *
- * @return {Promise}
- */
-TestClient.prototype.start = function() {
-    logger.log(this + ': starting');
-    this.httpBackend.when("GET", "/versions").respond(200, {});
-    this.httpBackend.when("GET", "/pushrules").respond(200, {});
-    this.httpBackend.when("POST", "/filter").respond(200, { filter_id: "fid" });
-    this.expectDeviceKeyUpload();
-
-    // we let the client do a very basic initial sync, which it needs before
-    // it will upload one-time keys.
-    this.httpBackend.when("GET", "/sync").respond(200, { next_batch: 1 });
-
-    this.client.startClient({
-        // set this so that we can get hold of failed events
-        pendingEventOrdering: 'detached',
-    });
-
-    return Promise.all([
-        this.httpBackend.flushAllExpected(),
-        syncPromise(this.client),
-    ]).then(() => {
-        logger.log(this + ': started');
-    });
-};
-
-/**
- * stop the client
- * @return {Promise} Resolves once the mock http backend has finished all pending flushes
- */
-TestClient.prototype.stop = function() {
-    this.client.stopClient();
-    return this.httpBackend.stop();
-};
-
-/**
- * Set up expectations that the client will upload device keys.
- */
-TestClient.prototype.expectDeviceKeyUpload = function() {
-    const self = this;
-    this.httpBackend.when("POST", "/keys/upload").respond(200, function(path, content) {
-        expect(content.one_time_keys).toBe(undefined);
-        expect(content.device_keys).toBeTruthy();
-
-        logger.log(self + ': received device keys');
-        // we expect this to happen before any one-time keys are uploaded.
-        expect(Object.keys(self.oneTimeKeys).length).toEqual(0);
-
-        self.deviceKeys = content.device_keys;
-        return { one_time_key_counts: { signed_curve25519: 0 } };
-    });
-};
-
-/**
- * If one-time keys have already been uploaded, return them. Otherwise,
- * set up an expectation that the keys will be uploaded, and wait for
- * that to happen.
- *
- * @returns {Promise} for the one-time keys
- */
-TestClient.prototype.awaitOneTimeKeyUpload = function() {
-    if (Object.keys(this.oneTimeKeys).length != 0) {
-        // already got one-time keys
-        return Promise.resolve(this.oneTimeKeys);
-    }
-
-    this.httpBackend.when("POST", "/keys/upload")
-        .respond(200, (path, content) => {
-            expect(content.device_keys).toBe(undefined);
-            expect(content.one_time_keys).toBe(undefined);
-            return { one_time_key_counts: {
-                signed_curve25519: Object.keys(this.oneTimeKeys).length,
-            } };
-        });
-
-    this.httpBackend.when("POST", "/keys/upload")
-          .respond(200, (path, content) => {
-              expect(content.device_keys).toBe(undefined);
-              expect(content.one_time_keys).toBeTruthy();
-              expect(content.one_time_keys).not.toEqual({});
-              logger.log('%s: received %i one-time keys', this,
-                          Object.keys(content.one_time_keys).length);
-              this.oneTimeKeys = content.one_time_keys;
-              return { one_time_key_counts: {
-                  signed_curve25519: Object.keys(this.oneTimeKeys).length,
-              } };
-          });
-
-    // this can take ages
-    return this.httpBackend.flush('/keys/upload', 2, 1000).then((flushed) => {
-        expect(flushed).toEqual(2);
-        return this.oneTimeKeys;
-    });
-};
-
-/**
- * Set up expectations that the client will query device keys.
- *
- * We check that the query contains each of the users in `response`.
- *
- * @param {Object} response   response to the query.
- */
-TestClient.prototype.expectKeyQuery = function(response) {
-    this.httpBackend.when('POST', '/keys/query').respond(
-        200, (path, content) => {
-            Object.keys(response.device_keys).forEach((userId) => {
-                expect(content.device_keys[userId]).toEqual(
-                    [],
-                    "Expected key query for " + userId + ", got " +
-                    Object.keys(content.device_keys),
-                );
-            });
-            return response;
-        });
-};
-
-/**
- * get the uploaded curve25519 device key
- *
- * @return {string} base64 device key
- */
-TestClient.prototype.getDeviceKey = function() {
-    const keyId = 'curve25519:' + this.deviceId;
-    return this.deviceKeys.keys[keyId];
-};
-
-/**
- * get the uploaded ed25519 device key
- *
- * @return {string} base64 device key
- */
-TestClient.prototype.getSigningKey = function() {
-    const keyId = 'ed25519:' + this.deviceId;
-    return this.deviceKeys.keys[keyId];
-};
-
-/**
- * flush a single /sync request, and wait for the syncing event
- *
- * @returns {Promise} promise which completes once the sync has been flushed
- */
-TestClient.prototype.flushSync = function() {
-    logger.log(`${this}: flushSync`);
-    return Promise.all([
-        this.httpBackend.flush('/sync', 1),
-        syncPromise(this.client),
-    ]).then(() => {
-        logger.log(`${this}: flushSync completed`);
-    });
-};
-
-TestClient.prototype.isFallbackICEServerAllowed = function() {
-    return true;
-};

spec/TestClient.ts

@@ -0,0 +1,239 @@
+/*
+Copyright 2016 OpenMarket Ltd
+Copyright 2017 Vector Creations Ltd
+Copyright 2018-2019 New Vector Ltd
+
+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.
+*/
+
+// load olm before the sdk if possible
+import './olm-loader';
+
+import MockHttpBackend from 'matrix-mock-request';
+
+import { LocalStorageCryptoStore } from '../src/crypto/store/localStorage-crypto-store';
+import { logger } from '../src/logger';
+import { WebStorageSessionStore } from "../src/store/session/webstorage";
+import { syncPromise } from "./test-utils/test-utils";
+import { createClient } from "../src/matrix";
+import { ICreateClientOpts, IDownloadKeyResult, MatrixClient, PendingEventOrdering } from "../src/client";
+import { MockStorageApi } from "./MockStorageApi";
+import { encodeUri } from "../src/utils";
+import { IDeviceKeys, IOneTimeKey } from "../src/crypto/dehydration";
+import { IKeyBackupSession } from "../src/crypto/keybackup";
+
+/**
+ * Wrapper for a MockStorageApi, MockHttpBackend and MatrixClient
+ */
+export class TestClient {
+    public readonly httpBackend: MockHttpBackend;
+    public readonly client: MatrixClient;
+    private deviceKeys: IDeviceKeys;
+    private oneTimeKeys: Record<string, IOneTimeKey>;
+
+    constructor(
+        public readonly userId?: string,
+        public readonly deviceId?: string,
+        accessToken?: string,
+        sessionStoreBackend?: Storage,
+        options?: Partial<ICreateClientOpts>,
+    ) {
+        if (sessionStoreBackend === undefined) {
+            sessionStoreBackend = new MockStorageApi();
+        }
+        const sessionStore = new WebStorageSessionStore(sessionStoreBackend);
+
+        this.httpBackend = new MockHttpBackend();
+
+        const fullOptions: ICreateClientOpts = {
+            baseUrl: "http://" + userId + ".test.server",
+            userId: userId,
+            accessToken: accessToken,
+            deviceId: deviceId,
+            sessionStore: sessionStore,
+            request: this.httpBackend.requestFn,
+            ...options,
+        };
+        if (!fullOptions.cryptoStore) {
+            // expose this so the tests can get to it
+            fullOptions.cryptoStore = new LocalStorageCryptoStore(sessionStoreBackend);
+        }
+        this.client = createClient(fullOptions);
+
+        this.deviceKeys = null;
+        this.oneTimeKeys = {};
+    }
+
+    public toString(): string {
+        return 'TestClient[' + this.userId + ']';
+    }
+
+    /**
+     * start the client, and wait for it to initialise.
+     */
+    public start(): Promise<void> {
+        logger.log(this + ': starting');
+        this.httpBackend.when("GET", "/versions").respond(200, {});
+        this.httpBackend.when("GET", "/pushrules").respond(200, {});
+        this.httpBackend.when("POST", "/filter").respond(200, { filter_id: "fid" });
+        this.expectDeviceKeyUpload();
+
+        // we let the client do a very basic initial sync, which it needs before
+        // it will upload one-time keys.
+        this.httpBackend.when("GET", "/sync").respond(200, { next_batch: 1 });
+
+        this.client.startClient({
+            // set this so that we can get hold of failed events
+            pendingEventOrdering: PendingEventOrdering.Detached,
+        });
+
+        return Promise.all([
+            this.httpBackend.flushAllExpected(),
+            syncPromise(this.client),
+        ]).then(() => {
+            logger.log(this + ': started');
+        });
+    }
+
+    /**
+     * stop the client
+     * @return {Promise} Resolves once the mock http backend has finished all pending flushes
+     */
+    public stop(): Promise<void> {
+        this.client.stopClient();
+        return this.httpBackend.stop();
+    }
+
+    /**
+     * Set up expectations that the client will upload device keys.
+     */
+    public expectDeviceKeyUpload() {
+        this.httpBackend.when("POST", "/keys/upload").respond(200, (path, content) => {
+            expect(content.one_time_keys).toBe(undefined);
+            expect(content.device_keys).toBeTruthy();
+
+            logger.log(this + ': received device keys');
+            // we expect this to happen before any one-time keys are uploaded.
+            expect(Object.keys(this.oneTimeKeys).length).toEqual(0);
+
+            this.deviceKeys = content.device_keys;
+            return { one_time_key_counts: { signed_curve25519: 0 } };
+        });
+    }
+
+    /**
+     * If one-time keys have already been uploaded, return them. Otherwise,
+     * set up an expectation that the keys will be uploaded, and wait for
+     * that to happen.
+     *
+     * @returns {Promise} for the one-time keys
+     */
+    public awaitOneTimeKeyUpload(): Promise<Record<string, IOneTimeKey>> {
+        if (Object.keys(this.oneTimeKeys).length != 0) {
+            // already got one-time keys
+            return Promise.resolve(this.oneTimeKeys);
+        }
+
+        this.httpBackend.when("POST", "/keys/upload")
+            .respond(200, (path, content) => {
+                expect(content.device_keys).toBe(undefined);
+                expect(content.one_time_keys).toBe(undefined);
+                return { one_time_key_counts: {
+                    signed_curve25519: Object.keys(this.oneTimeKeys).length,
+                } };
+            });
+
+        this.httpBackend.when("POST", "/keys/upload")
+            .respond(200, (path, content) => {
+                expect(content.device_keys).toBe(undefined);
+                expect(content.one_time_keys).toBeTruthy();
+                expect(content.one_time_keys).not.toEqual({});
+                logger.log('%s: received %i one-time keys', this,
+                    Object.keys(content.one_time_keys).length);
+                this.oneTimeKeys = content.one_time_keys;
+                return { one_time_key_counts: {
+                    signed_curve25519: Object.keys(this.oneTimeKeys).length,
+                } };
+            });
+
+        // this can take ages
+        return this.httpBackend.flush('/keys/upload', 2, 1000).then((flushed) => {
+            expect(flushed).toEqual(2);
+            return this.oneTimeKeys;
+        });
+    }
+
+    /**
+     * Set up expectations that the client will query device keys.
+     *
+     * We check that the query contains each of the users in `response`.
+     *
+     * @param {Object} response   response to the query.
+     */
+    public expectKeyQuery(response: IDownloadKeyResult) {
+        this.httpBackend.when('POST', '/keys/query').respond(
+            200, (path, content) => {
+                Object.keys(response.device_keys).forEach((userId) => {
+                    expect(content.device_keys[userId]).toEqual([]);
+                });
+                return response;
+            });
+    }
+
+    /**
+     * Set up expectations that the client will query key backups for a particular session
+     */
+    public expectKeyBackupQuery(roomId: string, sessionId: string, status: number, response: IKeyBackupSession) {
+        this.httpBackend.when('GET', encodeUri("/room_keys/keys/$roomId/$sessionId", {
+            $roomId: roomId,
+            $sessionId: sessionId,
+        })).respond(status, response);
+    }
+
+    /**
+     * get the uploaded curve25519 device key
+     *
+     * @return {string} base64 device key
+     */
+    public getDeviceKey(): string {
+        const keyId = 'curve25519:' + this.deviceId;
+        return this.deviceKeys.keys[keyId];
+    }
+
+    /**
+     * get the uploaded ed25519 device key
+     *
+     * @return {string} base64 device key
+     */
+    public getSigningKey(): string {
+        const keyId = 'ed25519:' + this.deviceId;
+        return this.deviceKeys.keys[keyId];
+    }
+
+    /**
+     * flush a single /sync request, and wait for the syncing event
+     */
+    public flushSync(): Promise<void> {
+        logger.log(`${this}: flushSync`);
+        return Promise.all([
+            this.httpBackend.flush('/sync', 1),
+            syncPromise(this.client),
+        ]).then(() => {
+            logger.log(`${this}: flushSync completed`);
+        });
+    }
+
+    public isFallbackICEServerAllowed(): boolean {
+        return true;
+    }
+}

spec/integ/matrix-client-crypto.spec.js

@@ -161,7 +161,7 @@ function aliDownloadsKeys() {
     return Promise.all([p1, p2]).then(() => {
         return aliTestClient.client.crypto.deviceList.saveIfDirty();
     }).then(() => {
-        aliTestClient.cryptoStore.getEndToEndDeviceData(null, (data) => {
+        aliTestClient.client.cryptoStore.getEndToEndDeviceData(null, (data) => {
             const devices = data.devices[bobUserId];
             expect(devices[bobDeviceId].keys).toEqual(bobTestClient.deviceKeys.keys);
             expect(devices[bobDeviceId].verified).

spec/integ/matrix-client-retrying.spec.ts

@@ -1,10 +1,26 @@
-import { EventStatus, RoomEvent } from "../../src/matrix";
+/*
+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.
+*/
+
+import { EventStatus, RoomEvent, MatrixClient } from "../../src/matrix";
 import { MatrixScheduler } from "../../src/scheduler";
 import { Room } from "../../src/models/room";
 import { TestClient } from "../TestClient";
 
 describe("MatrixClient retrying", function() {
-    let client: TestClient = null;
+    let client: MatrixClient = null;
     let httpBackend: TestClient["httpBackend"] = null;
     let scheduler;
     const userId = "@alice:localhost";

spec/integ/megolm-backup.spec.ts

@@ -0,0 +1,165 @@
+/*
+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.
+*/
+
+import { Account } from "@matrix-org/olm";
+
+import { logger } from "../../src/logger";
+import { decodeRecoveryKey } from "../../src/crypto/recoverykey";
+import { IKeyBackupInfo, IKeyBackupSession } from "../../src/crypto/keybackup";
+import { TestClient } from "../TestClient";
+import { IEvent } from "../../src";
+import { MatrixEvent, MatrixEventEvent } from "../../src/models/event";
+
+const ROOM_ID = '!ROOM:ID';
+
+const SESSION_ID = 'o+21hSjP+mgEmcfdslPsQdvzWnkdt0Wyo00Kp++R8Kc';
+
+const ENCRYPTED_EVENT: Partial<IEvent> = {
+    type: 'm.room.encrypted',
+    content: {
+        algorithm: 'm.megolm.v1.aes-sha2',
+        sender_key: 'SENDER_CURVE25519',
+        session_id: SESSION_ID,
+        ciphertext: 'AwgAEjD+VwXZ7PoGPRS/H4kwpAsMp/g+WPvJVtPEKE8fmM9IcT/N'
+            + 'CiwPb8PehecDKP0cjm1XO88k6Bw3D17aGiBHr5iBoP7oSw8CXULXAMTkBl'
+            + 'mkufRQq2+d0Giy1s4/Cg5n13jSVrSb2q7VTSv1ZHAFjUCsLSfR0gxqcQs',
+    },
+    room_id: '!ROOM:ID',
+    event_id: '$event1',
+    origin_server_ts: 1507753886000,
+};
+
+const CURVE25519_KEY_BACKUP_DATA: IKeyBackupSession = {
+    first_message_index: 0,
+    forwarded_count: 0,
+    is_verified: false,
+    session_data: {
+        ciphertext: '2z2M7CZ+azAiTHN1oFzZ3smAFFt+LEOYY6h3QO3XXGdw'
+            + '6YpNn/gpHDO6I/rgj1zNd4FoTmzcQgvKdU8kN20u5BWRHxaHTZ'
+            + 'Slne5RxE6vUdREsBgZePglBNyG0AogR/PVdcrv/v18Y6rLM5O9'
+            + 'SELmwbV63uV9Kuu/misMxoqbuqEdG7uujyaEKtjlQsJ5MGPQOy'
+            + 'Syw7XrnesSwF6XWRMxcPGRV0xZr3s9PI350Wve3EncjRgJ9IGF'
+            + 'ru1bcptMqfXgPZkOyGvrphHoFfoK7nY3xMEHUiaTRfRIjq8HNV'
+            + '4o8QY1qmWGnxNBQgOlL8MZlykjg3ULmQ3DtFfQPj/YYGS3jzxv'
+            + 'C+EBjaafmsg+52CTeK3Rswu72PX450BnSZ1i3If4xWAUKvjTpe'
+            + 'Ug5aDLqttOv1pITolTJDw5W/SD+b5rjEKg1CFCHGEGE9wwV3Nf'
+            + 'QHVCQL+dfpd7Or0poy4dqKMAi3g0o3Tg7edIF8d5rREmxaALPy'
+            + 'iie8PHD8mj/5Y0GLqrac4CD6+Mop7eUTzVovprjg',
+        mac: '5lxYBHQU80M',
+        ephemeral: '/Bn0A4UMFwJaDDvh0aEk1XZj3k1IfgCxgFY9P9a0b14',
+    },
+};
+
+const CURVE25519_BACKUP_INFO: IKeyBackupInfo = {
+    algorithm: "m.megolm_backup.v1.curve25519-aes-sha2",
+    version: "1",
+    auth_data: {
+        public_key: "hSDwCYkwp1R0i33ctD73Wg2/Og0mOBr066SpjqqbTmo",
+    },
+};
+
+const RECOVERY_KEY = "EsTc LW2K PGiF wKEA 3As5 g5c4 BXwk qeeJ ZJV8 Q9fu gUMN UE4d";
+
+/**
+ * start an Olm session with a given recipient
+ */
+function createOlmSession(olmAccount: Olm.Account, recipientTestClient: TestClient): Promise<Olm.Session> {
+    return recipientTestClient.awaitOneTimeKeyUpload().then((keys) => {
+        const otkId = Object.keys(keys)[0];
+        const otk = keys[otkId];
+
+        const session = new global.Olm.Session();
+        session.create_outbound(
+            olmAccount, recipientTestClient.getDeviceKey(), otk.key,
+        );
+        return session;
+    });
+}
+
+describe("megolm key backups", function() {
+    if (!global.Olm) {
+        logger.warn('not running megolm tests: Olm not present');
+        return;
+    }
+    const Olm = global.Olm;
+
+    let testOlmAccount: Account;
+    let aliceTestClient: TestClient;
+
+    beforeAll(function() {
+        return Olm.init();
+    });
+
+    beforeEach(async function() {
+        aliceTestClient = new TestClient(
+            "@alice:localhost", "xzcvb", "akjgkrgjs",
+        );
+        testOlmAccount = new Olm.Account();
+        testOlmAccount.create();
+        await aliceTestClient.client.initCrypto();
+        aliceTestClient.client.crypto.backupManager.backupInfo = CURVE25519_BACKUP_INFO;
+    });
+
+    afterEach(function() {
+        return aliceTestClient.stop();
+    });
+
+    it("Alice checks key backups when receiving a message she can't decrypt", function() {
+        const syncResponse = {
+            next_batch: 1,
+            rooms: {
+                join: {},
+            },
+        };
+        syncResponse.rooms.join[ROOM_ID] = {
+            timeline: {
+                events: [ENCRYPTED_EVENT],
+            },
+        };
+
+        return aliceTestClient.start().then(() => {
+            return createOlmSession(testOlmAccount, aliceTestClient);
+        }).then(() => {
+            const privkey = decodeRecoveryKey(RECOVERY_KEY);
+            return aliceTestClient.client.crypto.storeSessionBackupPrivateKey(privkey);
+        }).then(() => {
+            aliceTestClient.httpBackend.when("GET", "/sync").respond(200, syncResponse);
+            aliceTestClient.expectKeyBackupQuery(
+                ROOM_ID,
+                SESSION_ID,
+                200,
+                CURVE25519_KEY_BACKUP_DATA,
+            );
+            return aliceTestClient.httpBackend.flushAllExpected();
+        }).then(function(): Promise<MatrixEvent> {
+            const room = aliceTestClient.client.getRoom(ROOM_ID);
+            const event = room.getLiveTimeline().getEvents()[0];
+
+            if (event.getContent()) {
+                return Promise.resolve(event);
+            }
+
+            return new Promise((resolve, reject) => {
+                event.once(MatrixEventEvent.Decrypted, (ev) => {
+                    logger.log(`${Date.now()} event ${event.getId()} now decrypted`);
+                    resolve(ev);
+                });
+            });
+        }).then((event) => {
+            expect(event.getContent()).toEqual('testytest');
+        });
+    });
+});

spec/unit/webrtc/callEventHandler.spec.ts

@@ -15,7 +15,16 @@ limitations under the License.
 */
 
 import { TestClient } from '../../TestClient';
-import { ClientEvent, EventType, MatrixEvent, RoomEvent } from "../../../src";
+import {
+    ClientEvent,
+    EventTimeline,
+    EventTimelineSet,
+    EventType,
+    IRoomTimelineData,
+    MatrixEvent,
+    Room,
+    RoomEvent,
+} from "../../../src";
 import { CallEventHandler, CallEventHandlerEvent } from "../../../src/webrtc/callEventHandler";
 import { SyncState } from "../../../src/sync";
 
@@ -23,6 +32,8 @@ describe("callEventHandler", () => {
     it("should ignore a call if invite & hangup come within a single sync", () => {
         const testClient = new TestClient();
         const client = testClient.client;
+        const room = new Room("!room:id", client, "@user:id");
+        const timelineData: IRoomTimelineData = { timeline: new EventTimeline(new EventTimelineSet(room, {})) };
         client.callEventHandler = new CallEventHandler(client);
         client.callEventHandler.start();
 
@@ -33,7 +44,7 @@ describe("callEventHandler", () => {
                 call_id: "123",
             },
         });
-        client.emit(RoomEvent.Timeline, callInvite);
+        client.emit(RoomEvent.Timeline, callInvite, room, false, false, timelineData);
 
         const callHangup = new MatrixEvent({
             type: EventType.CallHangup,
@@ -41,13 +52,13 @@ describe("callEventHandler", () => {
                 call_id: "123",
             },
         });
-        client.emit(RoomEvent.Timeline, callHangup);
+        client.emit(RoomEvent.Timeline, callHangup, room, false, false, timelineData);
 
         const incomingCallEmitted = jest.fn();
         client.on(CallEventHandlerEvent.Incoming, incomingCallEmitted);
 
         client.getSyncState = jest.fn().mockReturnValue(SyncState.Syncing);
-        client.emit(ClientEvent.Sync);
+        client.emit(ClientEvent.Sync, SyncState.Syncing);
 
         expect(incomingCallEmitted).not.toHaveBeenCalled();
     });

src/client.ts

@@ -3100,6 +3100,18 @@ export class MatrixClient extends TypedEventEmitter<EmittedEvents, ClientEventHa
         return this.restoreKeyBackup(privKey, targetRoomId, targetSessionId, backupInfo, opts);
     }
 
+    public async restoreKeyBackupWithBackupManager(
+        targetRoomId: string | undefined,
+        targetSessionId: string | undefined,
+        backupInfo: IKeyBackupInfo,
+        opts: IKeyBackupRestoreOpts,
+    ): Promise<IKeyBackupRestoreResult> {
+        const privKey = await this.crypto.backupManager.getKey();
+        return this.restoreKeyBackup(
+            privKey, targetRoomId, targetSessionId, backupInfo, opts,
+        );
+    }
+
     private async restoreKeyBackup(
         privKey: ArrayLike<number>,
         targetRoomId: undefined,

src/crypto/algorithms/megolm.ts

@@ -1298,7 +1298,9 @@ class MegolmDecryption extends DecryptionAlgorithm {
 
         if (res === null) {
             // We've got a message for a session we don't have.
-            //
+            // try and get the missing key from the backup first
+            this.crypto.backupManager.queryKeyBackupRateLimited(event.getRoomId(), content.session_id).catch(() => {});
+
             // (XXX: We might actually have received this key since we started
             // decrypting, in which case we'll have scheduled a retry, and this
             // request will be redundant. We could probably check to see if the

src/crypto/backup.ts

@@ -35,6 +35,7 @@ import { UnstableValue } from "../NamespacedValue";
 import { CryptoEvent, IMegolmSessionData } from "./index";
 
 const KEY_BACKUP_KEYS_PER_REQUEST = 200;
+const KEY_BACKUP_CHECK_RATE_LIMIT = 5000; // ms
 
 type AuthData = IKeyBackupInfo["auth_data"];
 
@@ -111,6 +112,8 @@ export class BackupManager {
     public backupInfo: IKeyBackupInfo | undefined; // The info dict from /room_keys/version
     public checkedForBackup: boolean; // Have we checked the server for a backup we can use?
     private sendingBackups: boolean; // Are we currently sending backups?
+    private sessionLastCheckAttemptedTime: Record<string, number> = {}; // When did we last try to check the server for a given session id?
+
     constructor(private readonly baseApis: MatrixClient, public readonly getKey: GetKey) {
         this.checkedForBackup = false;
         this.sendingBackups = false;
@@ -282,6 +285,26 @@ export class BackupManager {
         return this.checkAndStart();
     }
 
+    /**
+     * Attempts to retrieve a session from a key backup, if enough time
+     * has elapsed since the last check for this session id.
+     */
+    public async queryKeyBackupRateLimited(
+        targetRoomId: string | undefined,
+        targetSessionId: string | undefined,
+    ): Promise<void> {
+        if (!this.backupInfo) { return; }
+
+        const now = new Date().getTime();
+        if (
+            !this.sessionLastCheckAttemptedTime[targetSessionId]
+                || now - this.sessionLastCheckAttemptedTime[targetSessionId] > KEY_BACKUP_CHECK_RATE_LIMIT
+        ) {
+            this.sessionLastCheckAttemptedTime[targetSessionId] = now;
+            await this.baseApis.restoreKeyBackupWithBackupManager(targetRoomId, targetSessionId, this.backupInfo, {});
+        }
+    }
+
     /**
      * Check if the given backup info is trusted.
      *

src/crypto/keybackup.ts

@@ -15,17 +15,19 @@ limitations under the License.
 */
 
 import { ISigned } from "../@types/signed";
+import { IEncryptedPayload } from "./aes";
+
+export interface Curve25519SessionData {
+    ciphertext: string;
+    ephemeral: string;
+    mac: string;
+}
 
 export interface IKeyBackupSession {
     first_message_index: number; // eslint-disable-line camelcase
     forwarded_count: number; // eslint-disable-line camelcase
     is_verified: boolean; // eslint-disable-line camelcase
-    session_data: { // eslint-disable-line camelcase
+    session_data: Curve25519SessionData | IEncryptedPayload; // eslint-disable-line camelcase
-        ciphertext: string;
-        ephemeral: string;
-        mac: string;
-        iv: string;
-    };
 }
 
 export interface IKeyBackupRoomSessions {