matrix-js-sdk/src/crypto/index.js

/*
Copyright 2016 OpenMarket Ltd
Copyright 2017 Vector Creations 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.
*/
"use strict";

/**
 * @module crypto
 */

const anotherjson = require('another-json');
const q = require("q");
import {EventEmitter} from 'events';

const utils = require("../utils");
const OlmDevice = require("./OlmDevice");
const olmlib = require("./olmlib");
const algorithms = require("./algorithms");
const DeviceInfo = require("./deviceinfo");
const DeviceVerification = DeviceInfo.DeviceVerification;
const DeviceList = require('./DeviceList').default;

import OutgoingRoomKeyRequestManager from './OutgoingRoomKeyRequestManager';

/**
 * Cryptography bits
 *
 * @constructor
 * @alias module:crypto
 *
 * @param {module:base-apis~MatrixBaseApis} baseApis base matrix api interface
 *
 * @param {external:EventEmitter} eventEmitter event source where we can register
 *    for event notifications
 *
 * @param {module:store/session/webstorage~WebStorageSessionStore} sessionStore
 *    Store to be used for end-to-end crypto session data
 *
 * @param {string} userId The user ID for the local user
 *
 * @param {string} deviceId The identifier for this device.
 *
 * @param {Object} clientStore the MatrixClient data store.
 *
 * @param {module:crypto/store/base~CryptoStore} cryptoStore
 *    storage for the crypto layer.
 */
function Crypto(baseApis, eventEmitter, sessionStore, userId, deviceId,
                clientStore, cryptoStore) {
    this._baseApis = baseApis;
    this._sessionStore = sessionStore;
    this._userId = userId;
    this._deviceId = deviceId;
    this._clientStore = clientStore;
    this._cryptoStore = cryptoStore;

    this._olmDevice = new OlmDevice(sessionStore);
    this._deviceList = new DeviceList(baseApis, sessionStore, this._olmDevice);
    this._initialDeviceListInvalidationPending = false;

    this._clientRunning = false;

    // the last time we did a check for the number of one-time-keys on the
    // server.
    this._lastOneTimeKeyCheck = null;
    this._oneTimeKeyCheckInProgress = false;

    // EncryptionAlgorithm instance for each room
    this._roomEncryptors = {};

    // map from algorithm to DecryptionAlgorithm instance, for each room
    this._roomDecryptors = {};

    this._supportedAlgorithms = utils.keys(
        algorithms.DECRYPTION_CLASSES,
    );

    // build our device keys: these will later be uploaded
    this._deviceKeys = {};
    this._deviceKeys["ed25519:" + this._deviceId] =
        this._olmDevice.deviceEd25519Key;
    this._deviceKeys["curve25519:" + this._deviceId] =
        this._olmDevice.deviceCurve25519Key;

    this._globalBlacklistUnverifiedDevices = false;

    this._outgoingRoomKeyRequestManager = new OutgoingRoomKeyRequestManager(
         baseApis, this._deviceId, this._cryptoStore,
    );

    // list of IncomingRoomKeyRequests/IncomingRoomKeyRequestCancellations
    // we received in the current sync.
    this._receivedRoomKeyRequests = [];
    this._receivedRoomKeyRequestCancellations = [];

    let myDevices = this._sessionStore.getEndToEndDevicesForUser(
        this._userId,
    );

    if (!myDevices) {
        myDevices = {};
    }

    if (!myDevices[this._deviceId]) {
        // add our own deviceinfo to the sessionstore
        const deviceInfo = {
            keys: this._deviceKeys,
            algorithms: this._supportedAlgorithms,
            verified: DeviceVerification.VERIFIED,
            known: true,
        };

        myDevices[this._deviceId] = deviceInfo;
        this._sessionStore.storeEndToEndDevicesForUser(
            this._userId, myDevices,
        );
    }

    _registerEventHandlers(this, eventEmitter);
}
utils.inherits(Crypto, EventEmitter);


function _registerEventHandlers(crypto, eventEmitter) {
    eventEmitter.on("sync", function(syncState, oldState, data) {
        try {
            if (syncState === "STOPPED") {
                crypto._clientRunning = false;
                crypto._outgoingRoomKeyRequestManager.stop();
            } else if (syncState === "PREPARED") {
                crypto._clientRunning = true;
                crypto._outgoingRoomKeyRequestManager.start();
            }
            if (syncState === "SYNCING") {
                crypto._onSyncCompleted(data);
            }
        } catch (e) {
            console.error("Error handling sync", e);
        }
    });

    eventEmitter.on("RoomMember.membership", function(event, member, oldMembership) {
        try {
            crypto._onRoomMembership(event, member, oldMembership);
        } catch (e) {
             console.error("Error handling membership change:", e);
        }
    });

    eventEmitter.on("toDeviceEvent", function(event) {
        try {
            if (event.getType() == "m.room_key") {
                crypto._onRoomKeyEvent(event);
            } else if (event.getType() == "m.new_device") {
                crypto._onNewDeviceEvent(event);
            } else if (event.getType() == "m.room_key_request") {
                crypto._onRoomKeyRequestEvent(event);
            }
        } catch (e) {
            console.error("Error handling toDeviceEvent:", e);
        }
    });

    eventEmitter.on("event", function(event) {
        try {
            if (!event.isState() || event.getType() != "m.room.encryption") {
                return;
            }
            crypto._onCryptoEvent(event);
        } catch (e) {
            console.error("Error handling crypto event:", e);
        }
    });
}

/**
 * @return {string} The version of Olm.
 */
Crypto.getOlmVersion = function() {
    return OlmDevice.getOlmVersion();
};

/**
 * Get the Ed25519 key for this device
 *
 * @return {string} base64-encoded ed25519 key.
 */
Crypto.prototype.getDeviceEd25519Key = function() {
    return this._olmDevice.deviceEd25519Key;
};

/**
 * Set the global override for whether the client should ever send encrypted
 * messages to unverified devices.  If false, it can still be overridden
 * per-room.  If true, it overrides the per-room settings.
 *
 * @param {boolean} value whether to unilaterally blacklist all
 * unverified devices
 */
Crypto.prototype.setGlobalBlacklistUnverifiedDevices = function(value) {
    this._globalBlacklistUnverifiedDevices = value;
};

/**
 * @return {boolean} whether to unilaterally blacklist all unverified devices
 */
Crypto.prototype.getGlobalBlacklistUnverifiedDevices = function() {
    return this._globalBlacklistUnverifiedDevices;
};

/**
 * Upload the device keys to the homeserver.
 * @return {object} A promise that will resolve when the keys are uploaded.
 */
Crypto.prototype.uploadDeviceKeys = function() {
    const crypto = this;
    const userId = crypto._userId;
    const deviceId = crypto._deviceId;

    const deviceKeys = {
        algorithms: crypto._supportedAlgorithms,
        device_id: deviceId,
        keys: crypto._deviceKeys,
        user_id: userId,
    };
    crypto._signObject(deviceKeys);

    return crypto._baseApis.uploadKeysRequest({
        device_keys: deviceKeys,
    }, {
        // for now, we set the device id explicitly, as we may not be using the
        // same one as used in login.
        device_id: deviceId,
    });
};

// check if it's time to upload one-time keys, and do so if so.
function _maybeUploadOneTimeKeys(crypto) {
    // frequency with which to check & upload one-time keys
    const uploadPeriod = 1000 * 60; // one minute

    // max number of keys to upload at once
    // Creating keys can be an expensive operation so we limit the
    // number we generate in one go to avoid blocking the application
    // for too long.
    const maxKeysPerCycle = 5;

    if (crypto._oneTimeKeyCheckInProgress) {
        return;
    }

    const now = Date.now();
    if (crypto._lastOneTimeKeyCheck !== null &&
        now - crypto._lastOneTimeKeyCheck < uploadPeriod
       ) {
        // we've done a key upload recently.
        return;
    }

    crypto._lastOneTimeKeyCheck = now;

    function uploadLoop(numberToGenerate) {
        if (numberToGenerate <= 0) {
            // If we don't need to generate any more keys then we are done.
            return;
        }

        const keysThisLoop = Math.min(numberToGenerate, maxKeysPerCycle);

        // Ask olm to generate new one time keys, then upload them to synapse.
        crypto._olmDevice.generateOneTimeKeys(keysThisLoop);
        return _uploadOneTimeKeys(crypto).then(() => {
            return uploadLoop(numberToGenerate - keysThisLoop);
        });
    }

    crypto._oneTimeKeyCheckInProgress = true;
    q().then(() => {
        // ask the server how many keys we have
        return crypto._baseApis.uploadKeysRequest({}, {
            device_id: crypto._deviceId,
        });
    }).then((res) => {
        // We need to keep a pool of one time public keys on the server so that
        // other devices can start conversations with us. But we can only store
        // a finite number of private keys in the olm Account object.
        // To complicate things further then can be a delay between a device
        // claiming a public one time key from the server and it sending us a
        // message. We need to keep the corresponding private key locally until
        // we receive the message.
        // But that message might never arrive leaving us stuck with duff
        // private keys clogging up our local storage.
        // So we need some kind of enginering compromise to balance all of
        // these factors.

        // We first find how many keys the server has for us.
        const keyCount = res.one_time_key_counts.signed_curve25519 || 0;
        // We then check how many keys we can store in the Account object.
        const maxOneTimeKeys = crypto._olmDevice.maxNumberOfOneTimeKeys();
        // Try to keep at most half that number on the server. This leaves the
        // rest of the slots free to hold keys that have been claimed from the
        // server but we haven't recevied a message for.
        // If we run out of slots when generating new keys then olm will
        // discard the oldest private keys first. This will eventually clean
        // out stale private keys that won't receive a message.
        const keyLimit = Math.floor(maxOneTimeKeys / 2);

        // We work out how many new keys we need to create to top up the server
        // If there are too many keys on the server then we don't need to
        // create any more keys.
        const numberToGenerate = Math.max(keyLimit - keyCount, 0);

        return uploadLoop(numberToGenerate);
    }).catch((e) => {
        console.error("Error uploading one-time keys", e.stack || e);
    }).finally(() => {
        crypto._oneTimeKeyCheckInProgress = false;
    }).done();
}

// returns a promise which resolves to the response
function _uploadOneTimeKeys(crypto) {
    const oneTimeKeys = crypto._olmDevice.getOneTimeKeys();
    const oneTimeJson = {};

    for (const keyId in oneTimeKeys.curve25519) {
        if (oneTimeKeys.curve25519.hasOwnProperty(keyId)) {
            const k = {
                key: oneTimeKeys.curve25519[keyId],
            };
            crypto._signObject(k);
            oneTimeJson["signed_curve25519:" + keyId] = k;
        }
    }

    return crypto._baseApis.uploadKeysRequest({
        one_time_keys: oneTimeJson,
    }, {
        // for now, we set the device id explicitly, as we may not be using the
        // same one as used in login.
        device_id: crypto._deviceId,
    }).then(function(res) {
        crypto._olmDevice.markKeysAsPublished();
        return res;
    });
}

/**
 * Download the keys for a list of users and stores the keys in the session
 * store.
 * @param {Array} userIds The users to fetch.
 * @param {bool} forceDownload Always download the keys even if cached.
 *
 * @return {Promise} A promise which resolves to a map userId->deviceId->{@link
 * module:crypto/deviceinfo|DeviceInfo}.
 */
Crypto.prototype.downloadKeys = function(userIds, forceDownload) {
    return this._deviceList.downloadKeys(userIds, forceDownload);
};

/**
 * Get the stored device keys for a user id
 *
 * @param {string} userId the user to list keys for.
 *
 * @return {module:crypto/deviceinfo[]|null} list of devices, or null if we haven't
 * managed to get a list of devices for this user yet.
 */
Crypto.prototype.getStoredDevicesForUser = function(userId) {
    return this._deviceList.getStoredDevicesForUser(userId);
};

/**
 * Get the stored keys for a single device
 *
 * @param {string} userId
 * @param {string} deviceId
 *
 * @return {module:crypto/deviceinfo?} device, or undefined
 * if we don't know about this device
 */
Crypto.prototype.getStoredDevice = function(userId, deviceId) {
    return this._deviceList.getStoredDevice(userId, deviceId);
};

/**
 * List the stored device keys for a user id
 *
 * @deprecated prefer {@link module:crypto#getStoredDevicesForUser}
 *
 * @param {string} userId the user to list keys for.
 *
 * @return {object[]} list of devices with "id", "verified", "blocked",
 *    "key", and "display_name" parameters.
 */
Crypto.prototype.listDeviceKeys = function(userId) {
    const devices = this.getStoredDevicesForUser(userId) || [];

    const result = [];

    for (let i = 0; i < devices.length; ++i) {
        const device = devices[i];
        const ed25519Key = device.getFingerprint();
        if (ed25519Key) {
            result.push({
                id: device.deviceId,
                key: ed25519Key,
                verified: Boolean(device.isVerified()),
                blocked: Boolean(device.isBlocked()),
                display_name: device.getDisplayName(),
            });
        }
    }

    // sort by deviceid
    result.sort(function(a, b) {
        if (a.deviceId < b.deviceId) {
            return -1;
        }
        if (a.deviceId > b.deviceId) {
            return 1;
        }
        return 0;
    });

    return result;
};

/**
 * Update the blocked/verified state of the given device
 *
 * @param {string} userId owner of the device
 * @param {string} deviceId unique identifier for the device
 *
 * @param {?boolean} verified whether to mark the device as verified. Null to
 *     leave unchanged.
 *
 * @param {?boolean} blocked whether to mark the device as blocked. Null to
 *      leave unchanged.
 *
 * @param {?boolean} known whether to mark that the user has been made aware of
 *      the existence of this device. Null to leave unchanged
 *
 * @return {module:crypto/deviceinfo} updated DeviceInfo
 */
Crypto.prototype.setDeviceVerification = function(userId, deviceId, verified,
                                                  blocked, known) {
    const devices = this._sessionStore.getEndToEndDevicesForUser(userId);
    if (!devices || !devices[deviceId]) {
        throw new Error("Unknown device " + userId + ":" + deviceId);
    }

    const dev = devices[deviceId];
    let verificationStatus = dev.verified;

    if (verified) {
        verificationStatus = DeviceVerification.VERIFIED;
    } else if (verified !== null && verificationStatus == DeviceVerification.VERIFIED) {
        verificationStatus = DeviceVerification.UNVERIFIED;
    }

    if (blocked) {
        verificationStatus = DeviceVerification.BLOCKED;
    } else if (blocked !== null && verificationStatus == DeviceVerification.BLOCKED) {
        verificationStatus = DeviceVerification.UNVERIFIED;
    }

    let knownStatus = dev.known;
    if (known !== null && known !== undefined) {
        knownStatus = known;
    }

    if (dev.verified !== verificationStatus || dev.known !== knownStatus) {
        dev.verified = verificationStatus;
        dev.known = knownStatus;
        this._sessionStore.storeEndToEndDevicesForUser(userId, devices);
    }
    return DeviceInfo.fromStorage(dev, deviceId);
};


/**
 * Get information on the active olm sessions with a user
 * <p>
 * Returns a map from device id to an object with keys 'deviceIdKey' (the
 * device's curve25519 identity key) and 'sessions' (an array of objects in the
 * same format as that returned by
 * {@link module:crypto/OlmDevice#getSessionInfoForDevice}).
 * <p>
 * This method is provided for debugging purposes.
 *
 * @param {string} userId id of user to inspect
 *
 * @return {Object.<string, {deviceIdKey: string, sessions: object[]}>}
 */
Crypto.prototype.getOlmSessionsForUser = function(userId) {
    const devices = this.getStoredDevicesForUser(userId) || [];
    const result = {};
    for (let j = 0; j < devices.length; ++j) {
        const device = devices[j];
        const deviceKey = device.getIdentityKey();
        const sessions = this._olmDevice.getSessionInfoForDevice(deviceKey);

        result[device.deviceId] = {
            deviceIdKey: deviceKey,
            sessions: sessions,
        };
    }
    return result;
};


/**
 * Get the device which sent an event
 *
 * @param {module:models/event.MatrixEvent} event event to be checked
 *
 * @return {module:crypto/deviceinfo?}
 */
Crypto.prototype.getEventSenderDeviceInfo = function(event) {
    const senderKey = event.getSenderKey();
    const algorithm = event.getWireContent().algorithm;

    if (!senderKey || !algorithm) {
        return null;
    }

    // senderKey is the Curve25519 identity key of the device which the event
    // was sent from. In the case of Megolm, it's actually the Curve25519
    // identity key of the device which set up the Megolm session.

    const device = this._deviceList.getDeviceByIdentityKey(
        event.getSender(), algorithm, senderKey,
    );

    if (device === null) {
        // we haven't downloaded the details of this device yet.
        return null;
    }

    // so far so good, but now we need to check that the sender of this event
    // hadn't advertised someone else's Curve25519 key as their own. We do that
    // by checking the Ed25519 claimed by the event (or, in the case of megolm,
    // the event which set up the megolm session), to check that it matches the
    // fingerprint of the purported sending device.
    //
    // (see https://github.com/vector-im/vector-web/issues/2215)

    const claimedKey = event.getKeysClaimed().ed25519;
    if (!claimedKey) {
        console.warn("Event " + event.getId() + " claims no ed25519 key: " +
                     "cannot verify sending device");
        return null;
    }

    if (claimedKey !== device.getFingerprint()) {
        console.warn(
            "Event " + event.getId() + " claims ed25519 key " + claimedKey +
                "but sender device has key " + device.getFingerprint());
        return null;
    }

    return device;
};


/**
 * Configure a room to use encryption (ie, save a flag in the sessionstore).
 *
 * @param {string} roomId The room ID to enable encryption in.
 *
 * @param {object} config The encryption config for the room.
 *
 * @param {boolean=} inhibitDeviceQuery true to suppress device list query for
 *   users in the room (for now)
 */
Crypto.prototype.setRoomEncryption = function(roomId, config, inhibitDeviceQuery) {
    // if we already have encryption in this room, we should ignore this event
    // (for now at least. maybe we should alert the user somehow?)
    const existingConfig = this._sessionStore.getEndToEndRoom(roomId);
    if (existingConfig) {
        if (JSON.stringify(existingConfig) != JSON.stringify(config)) {
            console.error("Ignoring m.room.encryption event which requests " +
                          "a change of config in " + roomId);
            return;
        }
    }

    const AlgClass = algorithms.ENCRYPTION_CLASSES[config.algorithm];
    if (!AlgClass) {
        throw new Error("Unable to encrypt with " + config.algorithm);
    }

    this._sessionStore.storeEndToEndRoom(roomId, config);

    const alg = new AlgClass({
        userId: this._userId,
        deviceId: this._deviceId,
        crypto: this,
        olmDevice: this._olmDevice,
        baseApis: this._baseApis,
        roomId: roomId,
        config: config,
    });
    this._roomEncryptors[roomId] = alg;

    // make sure we are tracking the device lists for all users in this room.
    console.log("Enabling encryption in " + roomId + "; " +
                "starting to track device lists for all users therein");
    const room = this._clientStore.getRoom(roomId);
    const members = room.getJoinedMembers();
    members.forEach((m) => {
        this._deviceList.startTrackingDeviceList(m.userId);
    });
    if (!inhibitDeviceQuery) {
        this._deviceList.refreshOutdatedDeviceLists();
    }
};


/**
 * @typedef {Object} module:crypto~OlmSessionResult
 * @property {module:crypto/deviceinfo} device  device info
 * @property {string?} sessionId base64 olm session id; null if no session
 *    could be established
 */

/**
 * Try to make sure we have established olm sessions for all known devices for
 * the given users.
 *
 * @param {string[]} users list of user ids
 *
 * @return {module:client.Promise} resolves once the sessions are complete, to
 *    an Object mapping from userId to deviceId to
 *    {@link module:crypto~OlmSessionResult}
 */
Crypto.prototype.ensureOlmSessionsForUsers = function(users) {
    const devicesByUser = {};

    for (let i = 0; i < users.length; ++i) {
        const userId = users[i];
        devicesByUser[userId] = [];

        const devices = this.getStoredDevicesForUser(userId) || [];
        for (let j = 0; j < devices.length; ++j) {
            const deviceInfo = devices[j];

            const key = deviceInfo.getIdentityKey();
            if (key == this._olmDevice.deviceCurve25519Key) {
                // don't bother setting up session to ourself
                continue;
            }
            if (deviceInfo.verified == DeviceVerification.BLOCKED) {
                // don't bother setting up sessions with blocked users
                continue;
            }

            devicesByUser[userId].push(deviceInfo);
        }
    }

    return olmlib.ensureOlmSessionsForDevices(
        this._olmDevice, this._baseApis, devicesByUser,
    );
};

/**
 * Whether encryption is enabled for a room.
 * @param {string} roomId the room id to query.
 * @return {bool} whether encryption is enabled.
 */
Crypto.prototype.isRoomEncrypted = function(roomId) {
    return Boolean(this._roomEncryptors[roomId]);
};


/**
 * Get a list containing all of the room keys
 *
 * @return {module:client.Promise} a promise which resolves to a list of
 *    session export objects
 */
Crypto.prototype.exportRoomKeys = function() {
    return q(
        this._sessionStore.getAllEndToEndInboundGroupSessionKeys().map(
            (s) => {
                const sess = this._olmDevice.exportInboundGroupSession(
                    s.senderKey, s.sessionId,
                );

                sess.algorithm = olmlib.MEGOLM_ALGORITHM;
                return sess;
            },
        ),
    );
};

/**
 * Import a list of room keys previously exported by exportRoomKeys
 *
 * @param {Object[]} keys a list of session export objects
 */
Crypto.prototype.importRoomKeys = function(keys) {
    keys.map((session) => {
        if (!session.room_id || !session.algorithm) {
            console.warn("ignoring session entry with missing fields", session);
            return;
        }

        const alg = this._getRoomDecryptor(session.room_id, session.algorithm);
        alg.importRoomKey(session);
    });
};

/**
 * Encrypt an event according to the configuration of the room, if necessary.
 *
 * @param {module:models/event.MatrixEvent} event  event to be sent
 *
 * @param {module:models/room?} room destination room. Null if the destination
 *     is not a room we have seen over the sync pipe.
 *
 * @return {module:client.Promise?} Promise which resolves when the event has been
 *     encrypted, or null if nothing was needed
 */
Crypto.prototype.encryptEventIfNeeded = function(event, room) {
    if (event.isEncrypted()) {
        // this event has already been encrypted; this happens if the
        // encryption step succeeded, but the send step failed on the first
        // attempt.
        return null;
    }

    if (!room) {
        throw new Error("Cannot send encrypted messages in unknown rooms");
    }

    const roomId = event.getRoomId();

    const alg = this._roomEncryptors[roomId];
    if (!alg) {
        // not encrypting messages in this room

        // check that the HS hasn't hidden the crypto event
        if (this._sessionStore.getEndToEndRoom(roomId)) {
            throw new Error(
                "Room was previously configured to use encryption, but is " +
                "no longer. Perhaps the homeserver is hiding the " +
                "configuration event.",
            );
        }
        return null;
    }

    // We can claim and prove ownership of all our device keys in the local
    // echo of the event since we know that all the local echos come from
    // this device.
    const myKeys = {
        curve25519: this._olmDevice.deviceCurve25519Key,
        ed25519: this._olmDevice.deviceEd25519Key,
    };

    return alg.encryptMessage(
        room, event.getType(), event.getContent(),
    ).then(function(encryptedContent) {
        event.makeEncrypted("m.room.encrypted", encryptedContent, myKeys);
    });
};

/**
 * Decrypt a received event
 *
 * @param {MatrixEvent} event
 *
 * @raises {algorithms.DecryptionError} if there is a problem decrypting the event
 */
Crypto.prototype.decryptEvent = function(event) {
    const content = event.getWireContent();
    const alg = this._getRoomDecryptor(event.getRoomId(), content.algorithm);
    alg.decryptEvent(event);
};

/**
 * Handle the notification from /sync that a user has updated their device list.
 *
 * @param {String} userId
 */
Crypto.prototype.userDeviceListChanged = function(userId) {
    this._deviceList.invalidateUserDeviceList(userId);

    // don't flush the outdated device list yet - we do it once we finish
    // processing the sync.
};

/**
 * Send a request for some room keys, if we have not already done so
 *
 * @param {module:crypto~RoomKeyRequestBody} requestBody
 * @param {Array<{userId: string, deviceId: string}>} recipients
 */
Crypto.prototype.requestRoomKey = function(requestBody, recipients) {
    this._outgoingRoomKeyRequestManager.sendRoomKeyRequest(
        requestBody, recipients,
    ).catch((e) => {
        // this normally means we couldn't talk to the store
        console.error(
            'Error requesting key for event', e,
        );
    }).done();
};

/**
 * handle an m.room.encryption event
 *
 * @private
 * @param {module:models/event.MatrixEvent} event encryption event
 */
Crypto.prototype._onCryptoEvent = function(event) {
    const roomId = event.getRoomId();
    const content = event.getContent();

    try {
        // inhibit the device list refresh for now - it will happen once we've
        // finished processing the sync, in _onSyncCompleted.
        this.setRoomEncryption(roomId, content, true);
    } catch (e) {
        console.error("Error configuring encryption in room " + roomId +
                      ":", e);
    }
};

/**
 * handle the completion of a /sync
 *
 * This is called after the processing of each successful /sync response.
 * It is an opportunity to do a batch process on the information received.
 *
 * @param {Object} syncData  the data from the 'MatrixClient.sync' event
 */
Crypto.prototype._onSyncCompleted = function(syncData) {
    const nextSyncToken = syncData.nextSyncToken;

    if (!syncData.oldSyncToken) {
        console.log("Completed initial sync");

        // an initialsync.
        this._sendNewDeviceEvents();

        // if we have a deviceSyncToken, we can tell the deviceList to
        // invalidate devices which have changed since then.
        const oldSyncToken = this._sessionStore.getEndToEndDeviceSyncToken();
        if (oldSyncToken !== null) {
            this._initialDeviceListInvalidationPending = true;
            this._invalidateDeviceListsSince(
                oldSyncToken, nextSyncToken,
            ).catch((e) => {
                // if that failed, we fall back to invalidating everyone.
                console.warn("Error fetching changed device list", e);
                this._deviceList.invalidateAllDeviceLists();
            }).done(() => {
                this._initialDeviceListInvalidationPending = false;
                this._deviceList.lastKnownSyncToken = nextSyncToken;
                this._deviceList.refreshOutdatedDeviceLists();
            });
        } else {
            // otherwise, we have to invalidate all devices for all users we
            // are tracking.
            console.log("Completed first initialsync; invalidating all " +
                        "device list caches");
            this._deviceList.invalidateAllDeviceLists();
        }
    }

    if (!this._initialDeviceListInvalidationPending) {
        // we can now store our sync token so that we can get an update on
        // restart rather than having to invalidate everyone.
        //
        // (we don't really need to do this on every sync - we could just
        // do it periodically)
        this._sessionStore.storeEndToEndDeviceSyncToken(nextSyncToken);
    }

    // catch up on any new devices we got told about during the sync.
    this._deviceList.lastKnownSyncToken = nextSyncToken;
    this._deviceList.refreshOutdatedDeviceLists();

    // we don't start uploading one-time keys until we've caught up with
    // to-device messages, to help us avoid throwing away one-time-keys that we
    // are about to receive messages for
    // (https://github.com/vector-im/riot-web/issues/2782).
    if (!syncData.catchingUp) {
        _maybeUploadOneTimeKeys(this);
        this._processReceivedRoomKeyRequests();
    }
};

/**
 * Send m.new_device messages to any devices we share a room with.
 *
 * (TODO: we can get rid of this once a suitable number of homeservers and
 * clients support the more reliable device list update stream mechanism)
 *
 * @private
 */
Crypto.prototype._sendNewDeviceEvents = function() {
    if (this._sessionStore.getDeviceAnnounced()) {
        return;
    }

    // we need to tell all the devices in all the rooms we are members of that
    // we have arrived.
    // build a list of rooms for each user.
    const roomsByUser = {};
    for (const room of this._getE2eRooms()) {
        const members = room.getJoinedMembers();
        for (let j = 0; j < members.length; j++) {
            const m = members[j];
            if (!roomsByUser[m.userId]) {
                roomsByUser[m.userId] = [];
            }
            roomsByUser[m.userId].push(room.roomId);
        }
    }

    // build a per-device message for each user
    const content = {};
    for (const userId in roomsByUser) {
        if (!roomsByUser.hasOwnProperty(userId)) {
            continue;
        }
        content[userId] = {
            "*": {
                device_id: this._deviceId,
                rooms: roomsByUser[userId],
            },
        };
    }

    const self = this;
    this._baseApis.sendToDevice(
        "m.new_device", // OH HAI!
        content,
    ).done(function() {
        self._sessionStore.setDeviceAnnounced();
    });
};

/**
 * Ask the server which users have new devices since a given token,
 * and invalidate them
 *
 * @param {String} oldSyncToken
 * @param {String} lastKnownSyncToken
 *
 * @returns {Promise} resolves once the query is complete. Rejects if the
 *   keyChange query fails.
 */
Crypto.prototype._invalidateDeviceListsSince = function(
    oldSyncToken, lastKnownSyncToken,
) {
    return this._baseApis.getKeyChanges(
        oldSyncToken, lastKnownSyncToken,
    ).then((r) => {
        console.log("got key changes since", oldSyncToken, ":", r.changed);

        if (!r.changed || !Array.isArray(r.changed)) {
            return;
        }

        r.changed.forEach((u) => {
            this._deviceList.invalidateUserDeviceList(u);
        });
    });
};

/**
 * Get a list of the e2e-enabled rooms we are members of
 *
 * @returns {module:models.Room[]}
 */
Crypto.prototype._getE2eRooms = function() {
    return this._clientStore.getRooms().filter((room) => {
        // check for rooms with encryption enabled
        const alg = this._roomEncryptors[room.roomId];
        if (!alg) {
            return false;
        }

        // ignore any rooms which we have left
        const me = room.getMember(this._userId);
        if (!me || (
            me.membership !== "join" && me.membership !== "invite"
        )) {
            return false;
        }

        return true;
    });
};

/**
 * Handle a key event
 *
 * @private
 * @param {module:models/event.MatrixEvent} event key event
 */
Crypto.prototype._onRoomKeyEvent = function(event) {
    const content = event.getContent();

    if (!content.room_id || !content.algorithm) {
        console.error("key event is missing fields");
        return;
    }

    const alg = this._getRoomDecryptor(content.room_id, content.algorithm);
    alg.onRoomKeyEvent(event);
};

/**
 * Handle a change in the membership state of a member of a room
 *
 * @private
 * @param {module:models/event.MatrixEvent} event  event causing the change
 * @param {module:models/room-member} member  user whose membership changed
 * @param {string=} oldMembership  previous membership
 */
Crypto.prototype._onRoomMembership = function(event, member, oldMembership) {
    // this event handler is registered on the *client* (as opposed to the room
    // member itself), which means it is only called on changes to the *live*
    // membership state (ie, it is not called when we back-paginate, nor when
    // we load the state in the initialsync).
    //
    // Further, it is automatically registered and called when new members
    // arrive in the room.

    const roomId = member.roomId;

    const alg = this._roomEncryptors[roomId];
    if (!alg) {
        // not encrypting in this room
        return;
    }

    if (member.membership == 'join') {
        console.log('Join event for ' + member.userId + ' in ' + roomId);
        // make sure we are tracking the deviceList for this user
        this._deviceList.startTrackingDeviceList(member.userId);
    }

    alg.onRoomMembership(event, member, oldMembership);
};


/**
 * Called when a new device announces itself
 *
 * @private
 * @param {module:models/event.MatrixEvent} event announcement event
 */
Crypto.prototype._onNewDeviceEvent = function(event) {
    const content = event.getContent();
    const userId = event.getSender();
    const deviceId = content.device_id;
    const rooms = content.rooms;

    if (!rooms || !deviceId) {
        console.warn("new_device event missing keys");
        return;
    }

    console.log("m.new_device event from " + userId + ":" + deviceId +
                " for rooms " + rooms);

    if (this.getStoredDevice(userId, deviceId)) {
        console.log("Known device; ignoring");
        return;
    }

    this._deviceList.invalidateUserDeviceList(userId);
};

/**
 * Called when we get an m.room_key_request event.
 *
 * @private
 * @param {module:models/event.MatrixEvent} event key request event
 */
Crypto.prototype._onRoomKeyRequestEvent = function(event) {
    const content = event.getContent();
    if (content.action === "request") {
        // Queue it up for now, because they tend to arrive before the room state
        // events at initial sync, and we want to see if we know anything about the
        // room before passing them on to the app.
        const req = new IncomingRoomKeyRequest(event);
        this._receivedRoomKeyRequests.push(req);
    } else if (content.action === "request_cancellation") {
        const req = new IncomingRoomKeyRequestCancellation(event);
        this._receivedRoomKeyRequestCancellations.push(req);
    }
};

/**
 * Process any m.room_key_request events which were queued up during the
 * current sync.
 *
 * @private
 */
Crypto.prototype._processReceivedRoomKeyRequests = function() {
    const requests = this._receivedRoomKeyRequests;
    this._receivedRoomKeyRequests = [];
    for (const req of requests) {
        const userId = req.userId;
        const deviceId = req.deviceId;

        const body = req.requestBody;
        const roomId = body.room_id;
        const alg = body.algorithm;

        console.log(`m.room_key_request from ${userId}:${deviceId}` +
                ` for ${roomId} / ${body.session_id} (id ${req.requestId})`);

        if (userId !== this._userId) {
            // TODO: determine if we sent this device the keys already: in
            // which case we can do so again.
            console.log("Ignoring room key request from other user for now");
            return;
        }

        // todo: should we queue up requests we don't yet have keys for,
        // in case they turn up later?

        // if we don't have a decryptor for this room/alg, we don't have
        // the keys for the requested events, and can drop the requests.
        if (!this._roomDecryptors[roomId]) {
            console.log(`room key request for unencrypted room ${roomId}`);
            continue;
        }

        const decryptor = this._roomDecryptors[roomId][alg];
        if (!decryptor) {
            console.log(`room key request for unknown alg ${alg} in room ${roomId}`);
            continue;
        }

        if (!decryptor.hasKeysForKeyRequest(req)) {
            console.log(
                `room key request for unknown session ${roomId} / ` +
                body.session_id,
            );
            continue;
        }

        req.share = () => {
            decryptor.shareKeysWithDevice(req);
        };

        // if the device is is verified already, share the keys
        const device = this._deviceList.getStoredDevice(userId, deviceId);
        if (device && device.isVerified()) {
            console.log('device is already verified: sharing keys');
            req.share();
            return;
        }

        this.emit("crypto.roomKeyRequest", req);
    }

    const cancellations = this._receivedRoomKeyRequestCancellations;
    this._receivedRoomKeyRequestCancellations = [];
    for (const cancellation of cancellations) {
        console.log(
            `m.room_key_request cancellation for ${cancellation.userId}:` +
            `${cancellation.deviceId} (id ${cancellation.requestId})`,
        );

        // we should probably only notify the app of cancellations we told it
        // about, but we don't currently have a record of that, so we just pass
        // everything through.
        this.emit("crypto.roomKeyRequestCancellation", cancellation);
    }
};

/**
 * Get a decryptor for a given room and algorithm.
 *
 * If we already have a decryptor for the given room and algorithm, return
 * it. Otherwise try to instantiate it.
 *
 * @private
 *
 * @param {string?} roomId   room id for decryptor. If undefined, a temporary
 * decryptor is instantiated.
 *
 * @param {string} algorithm  crypto algorithm
 *
 * @return {module:crypto.algorithms.base.DecryptionAlgorithm}
 *
 * @raises {module:crypto.algorithms.DecryptionError} if the algorithm is
 * unknown
 */
Crypto.prototype._getRoomDecryptor = function(roomId, algorithm) {
    let decryptors;
    let alg;

    roomId = roomId || null;
    if (roomId) {
        decryptors = this._roomDecryptors[roomId];
        if (!decryptors) {
            this._roomDecryptors[roomId] = decryptors = {};
        }

        alg = decryptors[algorithm];
        if (alg) {
            return alg;
        }
    }

    const AlgClass = algorithms.DECRYPTION_CLASSES[algorithm];
    if (!AlgClass) {
        throw new algorithms.DecryptionError(
            'Unknown encryption algorithm "' + algorithm + '".',
        );
    }
    alg = new AlgClass({
        userId: this._userId,
        crypto: this,
        olmDevice: this._olmDevice,
        baseApis: this._baseApis,
        roomId: roomId,
    });

    if (decryptors) {
        decryptors[algorithm] = alg;
    }
    return alg;
};


/**
 * sign the given object with our ed25519 key
 *
 * @param {Object} obj  Object to which we will add a 'signatures' property
 */
Crypto.prototype._signObject = function(obj) {
    const sigs = {};
    sigs[this._userId] = {};
    sigs[this._userId]["ed25519:" + this._deviceId] =
        this._olmDevice.sign(anotherjson.stringify(obj));
    obj.signatures = sigs;
};


/**
 * The parameters of a room key request. The details of the request may
 * vary with the crypto algorithm, but the management and storage layers for
 * outgoing requests expect it to have 'room_id' and 'session_id' properties.
 *
 * @typedef {Object} RoomKeyRequestBody
 */

/**
 * Represents a received m.room_key_request event
 *
 * @property {string} userId    user requesting the key
 * @property {string} deviceId  device requesting the key
 * @property {string} requestId unique id for the request
 * @property {RoomKeyRequestBody} requestBody
 * @property {Function} share  callback which, when called, will ask
 *    the relevant crypto algorithm implementation to share the keys for
 *    this request.
 */
class IncomingRoomKeyRequest {
    constructor(event) {
        const content = event.getContent();

        this.userId = event.getSender();
        this.deviceId = content.requesting_device_id;
        this.requestId = content.request_id;
        this.requestBody = content.body || {};
        this.share = () => {
            throw new Error("don't know how to share keys for this request yet");
        };
    }
}

/**
 * Represents a received m.room_key_request cancellation
 *
 * @property {string} userId    user requesting the cancellation
 * @property {string} deviceId  device requesting the cancellation
 * @property {string} requestId unique id for the request to be cancelled
 */
class IncomingRoomKeyRequestCancellation {
    constructor(event) {
        const content = event.getContent();

        this.userId = event.getSender();
        this.deviceId = content.requesting_device_id;
        this.requestId = content.request_id;
    }
}

/**
 * Fires when we receive a room key request
 *
 * @event module:client~MatrixClient#"crypto.roomKeyRequest"
 * @param {module:crypto~IncomingRoomKeyRequest} req  request details
 */

/**
 * Fires when we receive a room key request cancellation
 *
 * @event module:client~MatrixClient#"crypto.roomKeyRequestCancellation"
 * @param {module:crypto~IncomingRoomKeyRequestCancellation} req
 */

/** */
module.exports = Crypto;