websocket.js

'use strict';

const EventEmitter = require('events');
const crypto = require('crypto');
const https = require('https');
const http = require('http');
const url = require('url');

const PerMessageDeflate = require('./permessage-deflate');
const EventTarget = require('./event-target');
const extension = require('./extension');
const constants = require('./constants');
const Receiver = require('./receiver');
const Sender = require('./sender');

const readyStates = ['CONNECTING', 'OPEN', 'CLOSING', 'CLOSED'];
const protocolVersions = [8, 13];
const closeTimeout = 30 * 1000; // Allow 30 seconds to terminate the connection cleanly.

/**
 * Class representing a WebSocket.
 *
 * @extends EventEmitter
 */
class WebSocket extends EventEmitter {
  /**
   * Create a new `WebSocket`.
   *
   * @param {String} address The URL to which to connect
   * @param {(String|String[])} protocols The subprotocols
   * @param {Object} options Connection options
   */
  constructor (address, protocols, options) {
    super();

    this.readyState = WebSocket.CONNECTING;
    this.protocol = '';

    this._binaryType = constants.BINARY_TYPES[0];
    this._finalize = this.finalize.bind(this);
    this._closeFrameReceived = false;
    this._closeFrameSent = false;
    this._closeMessage = '';
    this._closeTimer = null;
    this._finalized = false;
    this._closeCode = 1006;
    this._extensions = {};
    this._isServer = true;
    this._receiver = null;
    this._sender = null;
    this._socket = null;
    this._error = null;

    if (address !== null) {
      if (!protocols) {
        protocols = [];
      } else if (typeof protocols === 'string') {
        protocols = [protocols];
      } else if (!Array.isArray(protocols)) {
        options = protocols;
        protocols = [];
      }

      initAsClient.call(this, address, protocols, options);
    }
  }

  get CONNECTING () { return WebSocket.CONNECTING; }
  get CLOSING () { return WebSocket.CLOSING; }
  get CLOSED () { return WebSocket.CLOSED; }
  get OPEN () { return WebSocket.OPEN; }

  /**
   * This deviates from the WHATWG interface since ws doesn't support the required
   * default "blob" type (instead we define a custom "nodebuffer" type).
   *
   * @type {String}
   */
  get binaryType () {
    return this._binaryType;
  }

  set binaryType (type) {
    if (constants.BINARY_TYPES.indexOf(type) < 0) return;

    this._binaryType = type;

    //
    // Allow to change `binaryType` on the fly.
    //
    if (this._receiver) this._receiver._binaryType = type;
  }

  /**
   * @type {Number}
   */
  get bufferedAmount () {
    if (!this._socket) return 0;

    //
    // `socket.bufferSize` is `undefined` if the socket is closed.
    //
    return (this._socket.bufferSize || 0) + this._sender._bufferedBytes;
  }

  /**
   * @type {String}
   */
  get extensions () {
    return Object.keys(this._extensions).join();
  }

  /**
   * Set up the socket and the internal resources.
   *
   * @param {net.Socket} socket The network socket between the server and client
   * @param {Buffer} head The first packet of the upgraded stream
   * @param {Number} maxPayload The maximum allowed message size
   * @private
   */
  setSocket (socket, head, maxPayload) {
    socket.setTimeout(0);
    socket.setNoDelay();

    socket.on('close', this._finalize);
    socket.on('error', this._finalize);
    socket.on('end', this._finalize);

    this._receiver = new Receiver(this._extensions, maxPayload, this.binaryType);
    this._sender = new Sender(socket, this._extensions);
    this._socket = socket;

    if (head.length > 0) socket.unshift(head);

    socket.on('data', this._receiver.add);

    this._receiver.onmessage = (data) => this.emit('message', data);
    this._receiver.onping = (data) => {
      this.pong(data, !this._isServer, constants.NOOP);
      this.emit('ping', data);
    };
    this._receiver.onpong = (data) => this.emit('pong', data);
    this._receiver.onclose = (code, reason) => {
      //
      // Discard any additional data that is received on the socket.
      //
      this._socket.removeListener('data', this._receiver.add);

      this._closeFrameReceived = true;
      this._closeMessage = reason;
      this._closeCode = code;

      if (code === 1005) this.close();
      else this.close(code, reason);
    };
    this._receiver.onerror = (error, code) => {
      if (this._error) return;

      this._closeCode = code;

      if (!this._finalized) this.finalize(error);
      else this.emit('error', error);
    };

    this.readyState = WebSocket.OPEN;
    this.emit('open');
  }

  /**
   * Clean up internal resources and emit the `'close'` event.
   *
   * @param {(Boolean|Error)} error Indicates whether or not an error occurred
   * @private
   */
  finalize (error) {
    if (this._finalized) return;

    this.readyState = WebSocket.CLOSING;
    this._finalized = true;

    if (!this._socket) {
      //
      // `error` is always an `Error` instance in this case.
      //
      this.emit('error', error);
      this.readyState = WebSocket.CLOSED;
      this.emit('close', this._closeCode, this._closeMessage);
      return;
    }

    clearTimeout(this._closeTimer);

    this._socket.removeListener('data', this._receiver.add);
    this._socket.removeListener('close', this._finalize);
    this._socket.removeListener('error', this._finalize);
    this._socket.removeListener('end', this._finalize);
    this._socket.on('error', constants.NOOP);

    if (error) {
      if (error !== true) this._error = error;
      this._socket.destroy();
    } else {
      this._socket.end();
    }

    this._receiver.cleanup(() => {
      const err = this._error;

      if (err) {
        this._error = null;
        this.emit('error', err);
      }

      this.readyState = WebSocket.CLOSED;

      if (this._extensions[PerMessageDeflate.extensionName]) {
        this._extensions[PerMessageDeflate.extensionName].cleanup();
      }

      this.emit('close', this._closeCode, this._closeMessage);
    });
  }

  /**
   * Start a closing handshake.
   *
   *            +----------+     +-----------+   +----------+
   *     + - - -|ws.close()|---->|close frame|-->|ws.close()|- - - -
   *            +----------+     +-----------+   +----------+       |
   *     |      +----------+     +-----------+         |
   *            |ws.close()|<----|close frame|<--------+            |
   *            +----------+     +-----------+         |
   *  CLOSING         |              +---+             |         CLOSING
   *                  |          +---|fin|<------------+
   *     |            |          |   +---+                          |
   *                  |          |   +---+      +-------------+
   *     |            +----------+-->|fin|----->|ws.finalize()| - - +
   *                             |   +---+      +-------------+
   *     |     +-------------+   |
   *      - - -|ws.finalize()|<--+
   *           +-------------+
   *
   * @param {Number} code Status code explaining why the connection is closing
   * @param {String} data A string explaining why the connection is closing
   * @public
   */
  close (code, data) {
    if (this.readyState === WebSocket.CLOSED) return;
    if (this.readyState === WebSocket.CONNECTING) {
      this._req.abort();
      this.finalize(
        new Error('WebSocket was closed before the connection was established')
      );
      return;
    }

    if (this.readyState === WebSocket.CLOSING) {
      if (this._closeFrameSent && this._closeFrameReceived) this._socket.end();
      return;
    }

    this.readyState = WebSocket.CLOSING;
    this._sender.close(code, data, !this._isServer, (err) => {
      //
      // This error is handled by the `'error'` listener on the socket. We only
      // want to know if the close frame has been sent here.
      //
      if (err) return;

      this._closeFrameSent = true;

      if (!this._finalized) {
        if (this._closeFrameReceived) this._socket.end();

        //
        // Ensure that the connection is cleaned up even when the closing
        // handshake fails.
        //
        this._closeTimer = setTimeout(this._finalize, closeTimeout, true);
      }
    });
  }

  /**
   * Send a ping.
   *
   * @param {*} data The data to send
   * @param {Boolean} mask Indicates whether or not to mask `data`
   * @param {Function} cb Callback which is executed when the ping is sent
   * @public
   */
  ping (data, mask, cb) {
    if (typeof data === 'function') {
      cb = data;
      data = mask = undefined;
    } else if (typeof mask === 'function') {
      cb = mask;
      mask = undefined;
    }

    if (this.readyState !== WebSocket.OPEN) {
      const err = new Error(
        `WebSocket is not open: readyState ${this.readyState} ` +
          `(${readyStates[this.readyState]})`
      );

      if (cb) return cb(err);
      throw err;
    }

    if (typeof data === 'number') data = data.toString();
    if (mask === undefined) mask = !this._isServer;
    this._sender.ping(data || constants.EMPTY_BUFFER, mask, cb);
  }

  /**
   * Send a pong.
   *
   * @param {*} data The data to send
   * @param {Boolean} mask Indicates whether or not to mask `data`
   * @param {Function} cb Callback which is executed when the pong is sent
   * @public
   */
  pong (data, mask, cb) {
    if (typeof data === 'function') {
      cb = data;
      data = mask = undefined;
    } else if (typeof mask === 'function') {
      cb = mask;
      mask = undefined;
    }

    if (this.readyState !== WebSocket.OPEN) {
      const err = new Error(
        `WebSocket is not open: readyState ${this.readyState} ` +
          `(${readyStates[this.readyState]})`
      );

      if (cb) return cb(err);
      throw err;
    }

    if (typeof data === 'number') data = data.toString();
    if (mask === undefined) mask = !this._isServer;
    this._sender.pong(data || constants.EMPTY_BUFFER, mask, cb);
  }

  /**
   * Send a data message.
   *
   * @param {*} data The message to send
   * @param {Object} options Options object
   * @param {Boolean} options.compress Specifies whether or not to compress `data`
   * @param {Boolean} options.binary Specifies whether `data` is binary or text
   * @param {Boolean} options.fin Specifies whether the fragment is the last one
   * @param {Boolean} options.mask Specifies whether or not to mask `data`
   * @param {Function} cb Callback which is executed when data is written out
   * @public
   */
  send (data, options, cb) {
    if (typeof options === 'function') {
      cb = options;
      options = {};
    }

    if (this.readyState !== WebSocket.OPEN) {
      const err = new Error(
        `WebSocket is not open: readyState ${this.readyState} ` +
          `(${readyStates[this.readyState]})`
      );

      if (cb) return cb(err);
      throw err;
    }

    if (typeof data === 'number') data = data.toString();

    const opts = Object.assign({
      binary: typeof data !== 'string',
      mask: !this._isServer,
      compress: true,
      fin: true
    }, options);

    if (!this._extensions[PerMessageDeflate.extensionName]) {
      opts.compress = false;
    }

    this._sender.send(data || constants.EMPTY_BUFFER, opts, cb);
  }

  /**
   * Forcibly close the connection.
   *
   * @public
   */
  terminate () {
    if (this.readyState === WebSocket.CLOSED) return;
    if (this.readyState === WebSocket.CONNECTING) {
      this._req.abort();
      this.finalize(
        new Error('WebSocket was closed before the connection was established')
      );
      return;
    }

    this.finalize(true);
  }
}

readyStates.forEach((readyState, i) => {
  WebSocket[readyStates[i]] = i;
});

//
// Add the `onopen`, `onerror`, `onclose`, and `onmessage` attributes.
// See https://html.spec.whatwg.org/multipage/comms.html#the-websocket-interface
//
['open', 'error', 'close', 'message'].forEach((method) => {
  Object.defineProperty(WebSocket.prototype, `on${method}`, {
    /**
     * Return the listener of the event.
     *
     * @return {(Function|undefined)} The event listener or `undefined`
     * @public
     */
    get () {
      const listeners = this.listeners(method);
      for (var i = 0; i < listeners.length; i++) {
        if (listeners[i]._listener) return listeners[i]._listener;
      }
    },
    /**
     * Add a listener for the event.
     *
     * @param {Function} listener The listener to add
     * @public
     */
    set (listener) {
      const listeners = this.listeners(method);
      for (var i = 0; i < listeners.length; i++) {
        //
        // Remove only the listeners added via `addEventListener`.
        //
        if (listeners[i]._listener) this.removeListener(method, listeners[i]);
      }
      this.addEventListener(method, listener);
    }
  });
});

WebSocket.prototype.addEventListener = EventTarget.addEventListener;
WebSocket.prototype.removeEventListener = EventTarget.removeEventListener;

module.exports = WebSocket;

/**
 * Initialize a WebSocket client.
 *
 * @param {String} address The URL to which to connect
 * @param {String[]} protocols The list of subprotocols
 * @param {Object} options Connection options
 * @param {String} options.protocol Value of the `Sec-WebSocket-Protocol` header
 * @param {(Boolean|Object)} options.perMessageDeflate Enable/disable permessage-deflate
 * @param {Number} options.handshakeTimeout Timeout in milliseconds for the handshake request
 * @param {String} options.localAddress Local interface to bind for network connections
 * @param {Number} options.protocolVersion Value of the `Sec-WebSocket-Version` header
 * @param {Object} options.headers An object containing request headers
 * @param {String} options.origin Value of the `Origin` or `Sec-WebSocket-Origin` header
 * @param {http.Agent} options.agent Use the specified Agent
 * @param {String} options.host Value of the `Host` header
 * @param {Number} options.family IP address family to use during hostname lookup (4 or 6).
 * @param {Function} options.checkServerIdentity A function to validate the server hostname
 * @param {Boolean} options.rejectUnauthorized Verify or not the server certificate
 * @param {String} options.passphrase The passphrase for the private key or pfx
 * @param {String} options.ciphers The ciphers to use or exclude
 * @param {String} options.ecdhCurve The curves for ECDH key agreement to use or exclude
 * @param {(String|String[]|Buffer|Buffer[])} options.cert The certificate key
 * @param {(String|String[]|Buffer|Buffer[])} options.key The private key
 * @param {(String|Buffer)} options.pfx The private key, certificate, and CA certs
 * @param {(String|String[]|Buffer|Buffer[])} options.ca Trusted certificates
 * @private
 */
function initAsClient (address, protocols, options) {
  options = Object.assign({
    protocolVersion: protocolVersions[1],
    protocol: protocols.join(','),
    perMessageDeflate: true,
    handshakeTimeout: null,
    localAddress: null,
    headers: null,
    family: null,
    origin: null,
    agent: null,
    host: null,

    //
    // SSL options.
    //
    checkServerIdentity: null,
    rejectUnauthorized: null,
    passphrase: null,
    ciphers: null,
    ecdhCurve: null,
    cert: null,
    key: null,
    pfx: null,
    ca: null
  }, options);

  if (protocolVersions.indexOf(options.protocolVersion) === -1) {
    throw new RangeError(
      `Unsupported protocol version: ${options.protocolVersion} ` +
        `(supported versions: ${protocolVersions.join(', ')})`
    );
  }

  this._isServer = false;
  this.url = address;

  const serverUrl = url.parse(address);
  const isUnixSocket = serverUrl.protocol === 'ws+unix:';

  if (!serverUrl.host && (!isUnixSocket || !serverUrl.path)) {
    throw new Error(`Invalid URL: ${address}`);
  }

  const isSecure = serverUrl.protocol === 'wss:' || serverUrl.protocol === 'https:';
  const key = crypto.randomBytes(16).toString('base64');
  const httpObj = isSecure ? https : http;
  var perMessageDeflate;

  const requestOptions = {
    port: serverUrl.port || (isSecure ? 443 : 80),
    host: serverUrl.hostname,
    path: '/',
    headers: {
      'Sec-WebSocket-Version': options.protocolVersion,
      'Sec-WebSocket-Key': key,
      'Connection': 'Upgrade',
      'Upgrade': 'websocket'
    }
  };

  if (options.headers) Object.assign(requestOptions.headers, options.headers);
  if (options.perMessageDeflate) {
    perMessageDeflate = new PerMessageDeflate(
      options.perMessageDeflate !== true ? options.perMessageDeflate : {},
      false
    );
    requestOptions.headers['Sec-WebSocket-Extensions'] = extension.format({
      [PerMessageDeflate.extensionName]: perMessageDeflate.offer()
    });
  }
  if (options.protocol) {
    requestOptions.headers['Sec-WebSocket-Protocol'] = options.protocol;
  }
  if (options.origin) {
    if (options.protocolVersion < 13) {
      requestOptions.headers['Sec-WebSocket-Origin'] = options.origin;
    } else {
      requestOptions.headers.Origin = options.origin;
    }
  }
  if (options.host) requestOptions.headers.Host = options.host;
  if (serverUrl.auth) requestOptions.auth = serverUrl.auth;

  if (options.localAddress) requestOptions.localAddress = options.localAddress;
  if (options.family) requestOptions.family = options.family;

  if (isUnixSocket) {
    const parts = serverUrl.path.split(':');

    requestOptions.socketPath = parts[0];
    requestOptions.path = parts[1];
  } else if (serverUrl.path) {
    //
    // Make sure that path starts with `/`.
    //
    if (serverUrl.path.charAt(0) !== '/') {
      requestOptions.path = `/${serverUrl.path}`;
    } else {
      requestOptions.path = serverUrl.path;
    }
  }

  var agent = options.agent;

  //
  // A custom agent is required for these options.
  //
  if (
    options.rejectUnauthorized != null ||
    options.checkServerIdentity ||
    options.passphrase ||
    options.ciphers ||
    options.ecdhCurve ||
    options.cert ||
    options.key ||
    options.pfx ||
    options.ca
  ) {
    if (options.passphrase) requestOptions.passphrase = options.passphrase;
    if (options.ciphers) requestOptions.ciphers = options.ciphers;
    if (options.ecdhCurve) requestOptions.ecdhCurve = options.ecdhCurve;
    if (options.cert) requestOptions.cert = options.cert;
    if (options.key) requestOptions.key = options.key;
    if (options.pfx) requestOptions.pfx = options.pfx;
    if (options.ca) requestOptions.ca = options.ca;
    if (options.checkServerIdentity) {
      requestOptions.checkServerIdentity = options.checkServerIdentity;
    }
    if (options.rejectUnauthorized != null) {
      requestOptions.rejectUnauthorized = options.rejectUnauthorized;
    }

    if (!agent) agent = new httpObj.Agent(requestOptions);
  }

  if (agent) requestOptions.agent = agent;

  this._req = httpObj.get(requestOptions);

  if (options.handshakeTimeout) {
    this._req.setTimeout(options.handshakeTimeout, () => {
      this._req.abort();
      this.finalize(new Error('Opening handshake has timed out'));
    });
  }

  this._req.on('error', (error) => {
    if (this._req.aborted) return;

    this._req = null;
    this.finalize(error);
  });

  this._req.on('response', (res) => {
    if (!this.emit('unexpected-response', this._req, res)) {
      this._req.abort();
      this.finalize(new Error(`Unexpected server response: ${res.statusCode}`));
    }
  });

  this._req.on('upgrade', (res, socket, head) => {
    this.emit('upgrade', res);

    //
    // The user may have closed the connection from a listener of the `upgrade`
    // event.
    //
    if (this.readyState !== WebSocket.CONNECTING) return;

    this._req = null;

    const digest = crypto.createHash('sha1')
      .update(key + constants.GUID, 'binary')
      .digest('base64');

    if (res.headers['sec-websocket-accept'] !== digest) {
      socket.destroy();
      return this.finalize(new Error('Invalid Sec-WebSocket-Accept header'));
    }

    const serverProt = res.headers['sec-websocket-protocol'];
    const protList = (options.protocol || '').split(/, */);
    var protError;

    if (!options.protocol && serverProt) {
      protError = 'Server sent a subprotocol but none was requested';
    } else if (options.protocol && !serverProt) {
      protError = 'Server sent no subprotocol';
    } else if (serverProt && protList.indexOf(serverProt) === -1) {
      protError = 'Server sent an invalid subprotocol';
    }

    if (protError) {
      socket.destroy();
      return this.finalize(new Error(protError));
    }

    if (serverProt) this.protocol = serverProt;

    if (perMessageDeflate) {
      try {
        const extensions = extension.parse(
          res.headers['sec-websocket-extensions']
        );

        if (extensions[PerMessageDeflate.extensionName]) {
          perMessageDeflate.accept(
            extensions[PerMessageDeflate.extensionName]
          );
          this._extensions[PerMessageDeflate.extensionName] = perMessageDeflate;
        }
      } catch (err) {
        socket.destroy();
        this.finalize(new Error('Invalid Sec-WebSocket-Extensions header'));
        return;
      }
    }

    this.setSocket(socket, head, 0);
  });
}