[IMP] Add per-channel encryption feature

ThanhDodeurOdoo · alexkuhn · commit 3b3a85b197db · 2024-05-07T15:35:21.000+02:00
This commit adds per-channel encryption to prevent users from signing
JWTs for channels that they did not create.

This features works by allowing an additional `key` claim in the JWT
used to request a room. When this claim is set, the JWTs used to
authenticate users are expected to be signed by this new key and not
the "global" SFU key (`AUTH_KEY` global variable).

This change is useful for cases like Odoo.SH where multiple parties
can use the same SFU with the same credentials.

task-3861455
diff --git a/src/client.js b/src/client.js
@@ -158,13 +158,15 @@ export class SfuClient extends EventTarget {
      * @param {string} url
      * @param {string} jsonWebToken
      * @param {Object} [options]
+     * @param {string} [options.channelUUID]
      * @param {[]} [options.iceServers]
      */
-    async connect(url, jsonWebToken, { iceServers } = {}) {
+    async connect(url, jsonWebToken, { channelUUID, iceServers } = {}) {
         // saving the options for so that the parameters are saved for reconnection attempts
         this._url = url.replace(/^http/, "ws"); // makes sure the url is a websocket url
         this._jsonWebToken = jsonWebToken;
         this._iceServers = iceServers;
+        this._channelUUID = channelUUID;
         this._connectRetryDelay = INITIAL_RECONNECT_DELAY;
         this._device = this._createDevice();
         await this._connect();
@@ -393,7 +395,9 @@ export class SfuClient extends EventTarget {
             webSocket.addEventListener(
                 "open",
                 () => {
-                    webSocket.send(JSON.stringify(this._jsonWebToken));
+                    webSocket.send(
+                        JSON.stringify({ channelUUID: this._channelUUID, jwt: this._jsonWebToken })
+                    );
                 },
                 { once: true }
             );
diff --git a/src/models/channel.js b/src/models/channel.js
@@ -37,6 +37,8 @@ export class Channel extends EventEmitter {
     uuid;
     /** @type {string} short of uuid for logging */
     name;
+    /** @type {WithImplicitCoercion<string>} base 64 buffer key */
+    key;
     /** @type {import("mediasoup").types.Router}*/
     router;
     /** @type {Map<number, Session>} */
@@ -50,18 +52,19 @@ export class Channel extends EventEmitter {
      * @param {string} remoteAddress
      * @param {string} issuer
      * @param {Object} [options]
+     * @param {string} [options.key] if the key is set, authentication with this channel uses this key
      * @param {boolean} [options.useWebRtc=true] whether to use WebRTC:
      *  with webRTC: can stream audio/video
      *  without webRTC: can only use websocket
      */
-    static async create(remoteAddress, issuer, { useWebRtc = true } = {}) {
+    static async create(remoteAddress, issuer, { key, useWebRtc = true } = {}) {
         const safeIssuer = `${remoteAddress}::${issuer}`;
         const oldChannel = Channel.recordsByIssuer.get(safeIssuer);
         if (oldChannel) {
             logger.verbose(`reusing channel ${oldChannel.uuid}`);
             return oldChannel;
         }
-        const options = {};
+        const options = { key };
         if (useWebRtc) {
             options.worker = await getWorker();
             options.router = await options.worker.createRouter({
@@ -71,7 +74,9 @@ export class Channel extends EventEmitter {
         const channel = new Channel(remoteAddress, options);
         Channel.recordsByIssuer.set(safeIssuer, channel);
         Channel.records.set(channel.uuid, channel);
-        logger.info(`created channel ${channel.uuid} for ${safeIssuer}`);
+        logger.info(
+            `created channel ${channel.uuid} (${key ? "unique" : "global"} key) for ${safeIssuer}`
+        );
         const onWorkerDeath = () => {
             logger.warn(`worker died, closing channel ${channel.uuid}`);
             channel.close();
@@ -111,14 +116,16 @@ export class Channel extends EventEmitter {
     /**
      * @param {string} remoteAddress
      * @param {Object} [options]
+     * @param {string} [options.key]
      * @param {import("mediasoup").types.Worker} [options.worker]
      * @param {import("mediasoup").types.Router} [options.router]
      */
-    constructor(remoteAddress, { worker, router } = {}) {
+    constructor(remoteAddress, { key, worker, router } = {}) {
         super();
         const now = new Date();
         this.createDate = now.toISOString();
         this.remoteAddress = remoteAddress;
+        this.key = key && Buffer.from(key, "base64");
         this.uuid = crypto.randomUUID();
         this.name = `${remoteAddress}*${this.uuid.slice(-5)}`;
         this.router = router;
diff --git a/src/services/auth.js b/src/services/auth.js
@@ -22,12 +22,13 @@ export function close() {
 
 /**
  * @param {string} jsonWebToken
+ * @param {WithImplicitCoercion<string>} [key] buffer/b64 str
  * @returns {Promise<any>} json serialized data
  * @throws {AuthenticationError}
  */
-export async function verify(jsonWebToken) {
+export async function verify(jsonWebToken, key = jwtKey) {
     try {
-        return jwt.verify(jsonWebToken, jwtKey, {
+        return jwt.verify(jsonWebToken, key, {
             algorithms: ["HS256"],
         });
     } catch {
diff --git a/src/services/http.js b/src/services/http.js
@@ -52,14 +52,15 @@ export async function start({ httpInterface = config.HTTP_INTERFACE, port = conf
         callback: async (req, res, { host, protocol, remoteAddress, searchParams }) => {
             try {
                 const jsonWebToken = req.headers.authorization?.split(" ")[1];
-                /** @type {{ iss: string }} */
+                /** @type {{ iss: string, key: string || undefined }} */
                 const claims = await auth.verify(jsonWebToken);
                 if (!claims.iss) {
                     logger.warn(`${remoteAddress}: missing issuer claim when creating channel`);
                     res.statusCode = 403; // forbidden
                     return res.end();
                 }
                 const channel = await Channel.create(remoteAddress, claims.iss, {
+                    key: claims.key,
                     useWebRtc: searchParams.get("webRTC") !== "false",
                 });
                 res.setHeader("Content-Type", "application/json");
diff --git a/src/services/ws.js b/src/services/ws.js
@@ -9,6 +9,12 @@ import { SESSION_CLOSE_CODE } from "#src/models/session.js";
 import { Channel } from "#src/models/channel.js";
 import { verify } from "#src/services/auth.js";
 
+/**
+ * @typedef Credentials
+ * @property {string} channelUUID
+ * @property {string} jwt
+ */
+
 const logger = new Logger("WS");
 /** @type {Map<number, import("ws").WebSocket>} */
 const unauthenticatedWebSockets = new Map();
@@ -44,8 +50,12 @@ export async function start(options) {
         }, config.timeouts.authentication);
         webSocket.once("message", async (message) => {
             try {
-                const jsonWebToken = JSON.parse(message);
-                const session = await connect(webSocket, jsonWebToken);
+                /** @type {Credentials | String} can be a string (the jwt) for backwards compatibility with version 1.1 and earlier */
+                const credentials = JSON.parse(message);
+                const session = await connect(webSocket, {
+                    channelUUID: credentials?.channelUUID,
+                    jwt: credentials.jwt || credentials,
+                });
                 session.remote = remoteAddress;
                 logger.info(`session [${session.name}] authenticated and created`);
                 webSocket.send(); // client can start using ws after this message.
@@ -91,17 +101,30 @@ export function close() {
 
 /**
  * @param {import("ws").WebSocket} webSocket
- * @param {string} jsonWebToken
+ * @param {Credentials}
  */
-async function connect(webSocket, jsonWebToken) {
+async function connect(webSocket, { channelUUID, jwt }) {
+    let channel = Channel.records.get(channelUUID);
     /** @type {{sfu_channel_uuid: string, session_id: number, ice_servers: Object[] }} */
-    const authResult = await verify(jsonWebToken);
+    const authResult = await verify(jwt, channel?.key);
     const { sfu_channel_uuid, session_id, ice_servers } = authResult;
-    if (!sfu_channel_uuid || !session_id) {
+    if (!channelUUID && sfu_channel_uuid) {
+        // Cases where the channelUUID is not provided in the credentials for backwards compatibility with version 1.1 and earlier.
+        channel = Channel.records.get(sfu_channel_uuid);
+        if (channel.key) {
+            throw new AuthenticationError(
+                "A channel with a key can only be accessed by providing a channelUUID in the credentials"
+            );
+        }
+    }
+    if (!channel) {
+        throw new AuthenticationError(`Channel does not exist`);
+    }
+    if (!session_id) {
         throw new AuthenticationError("Malformed JWT payload");
     }
     const bus = new Bus(webSocket, { batchDelay: config.timeouts.busBatch });
-    const { session } = Channel.join(sfu_channel_uuid, session_id);
+    const { session } = Channel.join(channel.uuid, session_id);
     session.once("close", ({ code }) => {
         let wsCloseCode = WS_CLOSE_CODE.CLEAN;
         switch (code) {
diff --git a/tests/utils/network.js b/tests/utils/network.js
@@ -51,6 +51,7 @@ export class LocalNetwork {
     async getChannelUUID(useWebRtc = true) {
         const jwt = this.makeJwt({
             iss: `http://${this.hostname}:${this.port}/`,
+            key: HMAC_B64_KEY,
         });
         const response = await fetch(
             `http://${this.hostname}:${this.port}/v${http.API_VERSION}/channel?webRTC=${useWebRtc}`,
@@ -59,7 +60,7 @@ export class LocalNetwork {
                 headers: {
                     Authorization: "jwt " + jwt,
                 },
-            },
+            }
         );
         const result = await response.json();
         return result.uuid;
@@ -104,6 +105,7 @@ export class LocalNetwork {
                 sfu_channel_uuid: channelUUID,
                 session_id: sessionId,
             }),
+            { channelUUID }
         );
         const channel = Channel.records.get(channelUUID);
         await isClientAuthenticated;
