Send a room key request on decryption failure

When we are missing the keys to decrypt an event, send out a request for those
keys to our other devices and to the original sender.

src/crypto/OutgoingRoomKeyRequestManager.js

@@ -0,0 +1,217 @@
+/*
+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.
+*/
+
+import q from 'q';
+
+import utils from '../utils';
+
+/**
+ * Internal module. Management of outgoing room key requests.
+ *
+ * See https://docs.google.com/document/d/1m4gQkcnJkxNuBmb5NoFCIadIY-DyqqNAS3lloE73BlQ
+ * for draft documentation on what we're supposed to be implementing here.
+ *
+ * @module
+ */
+
+// delay between deciding we want some keys, and sending out the request, to
+// allow for (a) it turning up anyway, (b) grouping requests together
+const SEND_KEY_REQUESTS_DELAY_MS = 500;
+
+/** possible states for a room key request
+ *
+ * @enum {number}
+ */
+const ROOM_KEY_REQUEST_STATES = {
+    /** request not yet sent */
+    UNSENT: 0,
+
+    /** request sent, awaiting reply */
+    SENT: 1,
+};
+
+export default class OutgoingRoomKeyRequestManager {
+    constructor(baseApis, deviceId, cryptoStore) {
+        this._baseApis = baseApis;
+        this._deviceId = deviceId;
+        this._cryptoStore = cryptoStore;
+
+        // handle for the delayed call to _sendOutgoingRoomKeyRequests. Non-null
+        // if the callback has been set, or if it is still running.
+        this._sendOutgoingRoomKeyRequestsTimer = null;
+
+        // sanity check to ensure that we don't end up with two concurrent runs
+        // of _sendOutgoingRoomKeyRequests
+        this._sendOutgoingRoomKeyRequestsRunning = false;
+
+        this._clientRunning = false;
+    }
+
+    /**
+     * Called when the client is started. Sets background processes running.
+     */
+    start() {
+        this._clientRunning = true;
+
+        // set the timer going, to handle any requests which didn't get sent
+        // on the previous run of the client.
+        this._startTimer();
+    }
+
+    /**
+     * Called when the client is stopped. Stops any running background processes.
+     */
+    stop() {
+        // stop the timer on the next run
+        this._clientRunning = false;
+    }
+
+    /**
+     * Send off a room key request, if we haven't already done so.
+     *
+     * The `requestBody` is compared (with a deep-equality check) against
+     * previous queued or sent requests and if it matches, no change is made.
+     * Otherwise, a request is added to the pending list, and a job is started
+     * in the background to send it.
+     *
+     * @param {module:crypto~RoomKeyRequestBody} requestBody
+     * @param {Array<{userId: string, deviceId: string}>} recipients
+     *
+     * @returns {Promise} resolves when the request has been added to the
+     *    pending list (or we have established that a similar request already
+     *    exists)
+     */
+    sendRoomKeyRequest(requestBody, recipients) {
+        return this._cryptoStore.getOrAddOutgoingRoomKeyRequest({
+            requestBody: requestBody,
+            recipients: recipients,
+            requestId: this._baseApis.makeTxnId(),
+            state: ROOM_KEY_REQUEST_STATES.UNSENT,
+        }).then((req) => {
+            if (req.state === ROOM_KEY_REQUEST_STATES.UNSENT) {
+                this._startTimer();
+            }
+        });
+    }
+
+    // start the background timer to send queued requests, if the timer isn't
+    // already running
+    _startTimer() {
+        if (this._sendOutgoingRoomKeyRequestsTimer) {
+            return;
+        }
+
+        const startSendingOutgoingRoomKeyRequests = () => {
+            if (this._sendOutgoingRoomKeyRequestsRunning) {
+                throw new Error("RoomKeyRequestSend already in progress!");
+            }
+            this._sendOutgoingRoomKeyRequestsRunning = true;
+
+            this._sendOutgoingRoomKeyRequests().finally(() => {
+                this._sendOutgoingRoomKeyRequestsRunning = false;
+            }).done();
+        };
+
+        this._sendOutgoingRoomKeyRequestsTimer = global.setTimeout(
+            startSendingOutgoingRoomKeyRequests,
+            SEND_KEY_REQUESTS_DELAY_MS,
+        );
+    }
+
+    // look for and send any queued requests. Runs itself recursively until
+    // there are no more requests, or there is an error (in which case, the
+    // timer will be restarted before the promise resolves).
+    _sendOutgoingRoomKeyRequests() {
+        if (!this._clientRunning) {
+            this._sendOutgoingRoomKeyRequestsTimer = null;
+            return q();
+        }
+
+        console.log("Looking for queued outgoing room key requests");
+
+        return this._cryptoStore.getOutgoingRoomKeyRequestByState([
+            ROOM_KEY_REQUEST_STATES.UNSENT,
+        ]).then((req) => {
+            if (!req) {
+                console.log("No more outgoing room key requests");
+                this._sendOutgoingRoomKeyRequestsTimer = null;
+                return;
+            }
+
+            return this._sendOutgoingRoomKeyRequest(req).then(() => {
+                // go around the loop again
+                return this._sendOutgoingRoomKeyRequests();
+            }).catch((e) => {
+                console.error("Error sending room key request; will retry later.", e);
+                this._sendOutgoingRoomKeyRequestsTimer = null;
+                this._startTimer();
+            }).done();
+        });
+    }
+
+    // given a RoomKeyRequest, send it and update the request record
+    _sendOutgoingRoomKeyRequest(req) {
+        console.log(
+            `Requesting keys for ${stringifyRequestBody(req.requestBody)}` +
+            ` from ${stringifyRecipientList(req.recipients)}` +
+            `(id ${req.requestId})`,
+        );
+
+        const requestMessage = {
+            action: "request",
+            requesting_device_id: this._deviceId,
+            request_id: req.requestId,
+            body: req.requestBody,
+        };
+
+        return this._sendMessageToDevices(
+            requestMessage, req.recipients, req.requestId,
+        ).then(() => {
+            return this._cryptoStore.updateOutgoingRoomKeyRequest(
+                req.requestId, ROOM_KEY_REQUEST_STATES.UNSENT,
+                { state: ROOM_KEY_REQUEST_STATES.SENT },
+            );
+        });
+    }
+
+    // send a RoomKeyRequest to a list of recipients
+    _sendMessageToDevices(message, recipients, txnId) {
+        const contentMap = {};
+        for (const recip of recipients) {
+            if (!contentMap[recip.userId]) {
+                contentMap[recip.userId] = {};
+            }
+            contentMap[recip.userId][recip.deviceId] = message;
+        }
+
+        return this._baseApis.sendToDevice(
+            'm.room_key_request', contentMap, txnId,
+        );
+    }
+}
+
+function stringifyRequestBody(requestBody) {
+    // we assume that the request is for megolm keys, which are identified by
+    // room id and session id
+    return requestBody.room_id + " / " + requestBody.session_id;
+}
+
+function stringifyRecipientList(recipients) {
+    return '['
+        + utils.map(recipients, (r) => `${r.userId}:${r.deviceId}`).join(",")
+        + ']';
+}
+