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receiver.js13.7 KB · 608 lines
'use strict'; const { Writable } = require('stream'); const PerMessageDeflate = require('./permessage-deflate');const {  BINARY_TYPES,  EMPTY_BUFFER,  kStatusCode,  kWebSocket} = require('./constants');const { concat, toArrayBuffer, unmask } = require('./buffer-util');const { isValidStatusCode, isValidUTF8 } = require('./validation'); const GET_INFO = 0;const GET_PAYLOAD_LENGTH_16 = 1;const GET_PAYLOAD_LENGTH_64 = 2;const GET_MASK = 3;const GET_DATA = 4;const INFLATING = 5; /** * HyBi Receiver implementation. * * @extends Writable */class Receiver extends Writable {  /**   * Creates a Receiver instance.   *   * @param {String} [binaryType=nodebuffer] The type for binary data   * @param {Object} [extensions] An object containing the negotiated extensions   * @param {Boolean} [isServer=false] Specifies whether to operate in client or   *     server mode   * @param {Number} [maxPayload=0] The maximum allowed message length   */  constructor(binaryType, extensions, isServer, maxPayload) {    super();     this._binaryType = binaryType || BINARY_TYPES[0];    this[kWebSocket] = undefined;    this._extensions = extensions || {};    this._isServer = !!isServer;    this._maxPayload = maxPayload | 0;     this._bufferedBytes = 0;    this._buffers = [];     this._compressed = false;    this._payloadLength = 0;    this._mask = undefined;    this._fragmented = 0;    this._masked = false;    this._fin = false;    this._opcode = 0;     this._totalPayloadLength = 0;    this._messageLength = 0;    this._fragments = [];     this._state = GET_INFO;    this._loop = false;  }   /**   * Implements `Writable.prototype._write()`.   *   * @param {Buffer} chunk The chunk of data to write   * @param {String} encoding The character encoding of `chunk`   * @param {Function} cb Callback   * @private   */  _write(chunk, encoding, cb) {    if (this._opcode === 0x08 && this._state == GET_INFO) return cb();     this._bufferedBytes += chunk.length;    this._buffers.push(chunk);    this.startLoop(cb);  }   /**   * Consumes `n` bytes from the buffered data.   *   * @param {Number} n The number of bytes to consume   * @return {Buffer} The consumed bytes   * @private   */  consume(n) {    this._bufferedBytes -= n;     if (n === this._buffers[0].length) return this._buffers.shift();     if (n < this._buffers[0].length) {      const buf = this._buffers[0];      this._buffers[0] = buf.slice(n);      return buf.slice(0, n);    }     const dst = Buffer.allocUnsafe(n);     do {      const buf = this._buffers[0];      const offset = dst.length - n;       if (n >= buf.length) {        dst.set(this._buffers.shift(), offset);      } else {        dst.set(new Uint8Array(buf.buffer, buf.byteOffset, n), offset);        this._buffers[0] = buf.slice(n);      }       n -= buf.length;    } while (n > 0);     return dst;  }   /**   * Starts the parsing loop.   *   * @param {Function} cb Callback   * @private   */  startLoop(cb) {    let err;    this._loop = true;     do {      switch (this._state) {        case GET_INFO:          err = this.getInfo();          break;        case GET_PAYLOAD_LENGTH_16:          err = this.getPayloadLength16();          break;        case GET_PAYLOAD_LENGTH_64:          err = this.getPayloadLength64();          break;        case GET_MASK:          this.getMask();          break;        case GET_DATA:          err = this.getData(cb);          break;        default:          // `INFLATING`          this._loop = false;          return;      }    } while (this._loop);     cb(err);  }   /**   * Reads the first two bytes of a frame.   *   * @return {(RangeError|undefined)} A possible error   * @private   */  getInfo() {    if (this._bufferedBytes < 2) {      this._loop = false;      return;    }     const buf = this.consume(2);     if ((buf[0] & 0x30) !== 0x00) {      this._loop = false;      return error(        RangeError,        'RSV2 and RSV3 must be clear',        true,        1002,        'WS_ERR_UNEXPECTED_RSV_2_3'      );    }     const compressed = (buf[0] & 0x40) === 0x40;     if (compressed && !this._extensions[PerMessageDeflate.extensionName]) {      this._loop = false;      return error(        RangeError,        'RSV1 must be clear',        true,        1002,        'WS_ERR_UNEXPECTED_RSV_1'      );    }     this._fin = (buf[0] & 0x80) === 0x80;    this._opcode = buf[0] & 0x0f;    this._payloadLength = buf[1] & 0x7f;     if (this._opcode === 0x00) {      if (compressed) {        this._loop = false;        return error(          RangeError,          'RSV1 must be clear',          true,          1002,          'WS_ERR_UNEXPECTED_RSV_1'        );      }       if (!this._fragmented) {        this._loop = false;        return error(          RangeError,          'invalid opcode 0',          true,          1002,          'WS_ERR_INVALID_OPCODE'        );      }       this._opcode = this._fragmented;    } else if (this._opcode === 0x01 || this._opcode === 0x02) {      if (this._fragmented) {        this._loop = false;        return error(          RangeError,          `invalid opcode ${this._opcode}`,          true,          1002,          'WS_ERR_INVALID_OPCODE'        );      }       this._compressed = compressed;    } else if (this._opcode > 0x07 && this._opcode < 0x0b) {      if (!this._fin) {        this._loop = false;        return error(          RangeError,          'FIN must be set',          true,          1002,          'WS_ERR_EXPECTED_FIN'        );      }       if (compressed) {        this._loop = false;        return error(          RangeError,          'RSV1 must be clear',          true,          1002,          'WS_ERR_UNEXPECTED_RSV_1'        );      }       if (this._payloadLength > 0x7d) {        this._loop = false;        return error(          RangeError,          `invalid payload length ${this._payloadLength}`,          true,          1002,          'WS_ERR_INVALID_CONTROL_PAYLOAD_LENGTH'        );      }    } else {      this._loop = false;      return error(        RangeError,        `invalid opcode ${this._opcode}`,        true,        1002,        'WS_ERR_INVALID_OPCODE'      );    }     if (!this._fin && !this._fragmented) this._fragmented = this._opcode;    this._masked = (buf[1] & 0x80) === 0x80;     if (this._isServer) {      if (!this._masked) {        this._loop = false;        return error(          RangeError,          'MASK must be set',          true,          1002,          'WS_ERR_EXPECTED_MASK'        );      }    } else if (this._masked) {      this._loop = false;      return error(        RangeError,        'MASK must be clear',        true,        1002,        'WS_ERR_UNEXPECTED_MASK'      );    }     if (this._payloadLength === 126) this._state = GET_PAYLOAD_LENGTH_16;    else if (this._payloadLength === 127) this._state = GET_PAYLOAD_LENGTH_64;    else return this.haveLength();  }   /**   * Gets extended payload length (7+16).   *   * @return {(RangeError|undefined)} A possible error   * @private   */  getPayloadLength16() {    if (this._bufferedBytes < 2) {      this._loop = false;      return;    }     this._payloadLength = this.consume(2).readUInt16BE(0);    return this.haveLength();  }   /**   * Gets extended payload length (7+64).   *   * @return {(RangeError|undefined)} A possible error   * @private   */  getPayloadLength64() {    if (this._bufferedBytes < 8) {      this._loop = false;      return;    }     const buf = this.consume(8);    const num = buf.readUInt32BE(0);     //    // The maximum safe integer in JavaScript is 2^53 - 1. An error is returned    // if payload length is greater than this number.    //    if (num > Math.pow(2, 53 - 32) - 1) {      this._loop = false;      return error(        RangeError,        'Unsupported WebSocket frame: payload length > 2^53 - 1',        false,        1009,        'WS_ERR_UNSUPPORTED_DATA_PAYLOAD_LENGTH'      );    }     this._payloadLength = num * Math.pow(2, 32) + buf.readUInt32BE(4);    return this.haveLength();  }   /**   * Payload length has been read.   *   * @return {(RangeError|undefined)} A possible error   * @private   */  haveLength() {    if (this._payloadLength && this._opcode < 0x08) {      this._totalPayloadLength += this._payloadLength;      if (this._totalPayloadLength > this._maxPayload && this._maxPayload > 0) {        this._loop = false;        return error(          RangeError,          'Max payload size exceeded',          false,          1009,          'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH'        );      }    }     if (this._masked) this._state = GET_MASK;    else this._state = GET_DATA;  }   /**   * Reads mask bytes.   *   * @private   */  getMask() {    if (this._bufferedBytes < 4) {      this._loop = false;      return;    }     this._mask = this.consume(4);    this._state = GET_DATA;  }   /**   * Reads data bytes.   *   * @param {Function} cb Callback   * @return {(Error|RangeError|undefined)} A possible error   * @private   */  getData(cb) {    let data = EMPTY_BUFFER;     if (this._payloadLength) {      if (this._bufferedBytes < this._payloadLength) {        this._loop = false;        return;      }       data = this.consume(this._payloadLength);      if (this._masked) unmask(data, this._mask);    }     if (this._opcode > 0x07) return this.controlMessage(data);     if (this._compressed) {      this._state = INFLATING;      this.decompress(data, cb);      return;    }     if (data.length) {      //      // This message is not compressed so its lenght is the sum of the payload      // length of all fragments.      //      this._messageLength = this._totalPayloadLength;      this._fragments.push(data);    }     return this.dataMessage();  }   /**   * Decompresses data.   *   * @param {Buffer} data Compressed data   * @param {Function} cb Callback   * @private   */  decompress(data, cb) {    const perMessageDeflate = this._extensions[PerMessageDeflate.extensionName];     perMessageDeflate.decompress(data, this._fin, (err, buf) => {      if (err) return cb(err);       if (buf.length) {        this._messageLength += buf.length;        if (this._messageLength > this._maxPayload && this._maxPayload > 0) {          return cb(            error(              RangeError,              'Max payload size exceeded',              false,              1009,              'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH'            )          );        }         this._fragments.push(buf);      }       const er = this.dataMessage();      if (er) return cb(er);       this.startLoop(cb);    });  }   /**   * Handles a data message.   *   * @return {(Error|undefined)} A possible error   * @private   */  dataMessage() {    if (this._fin) {      const messageLength = this._messageLength;      const fragments = this._fragments;       this._totalPayloadLength = 0;      this._messageLength = 0;      this._fragmented = 0;      this._fragments = [];       if (this._opcode === 2) {        let data;         if (this._binaryType === 'nodebuffer') {          data = concat(fragments, messageLength);        } else if (this._binaryType === 'arraybuffer') {          data = toArrayBuffer(concat(fragments, messageLength));        } else {          data = fragments;        }         this.emit('message', data);      } else {        const buf = concat(fragments, messageLength);         if (!isValidUTF8(buf)) {          this._loop = false;          return error(            Error,            'invalid UTF-8 sequence',            true,            1007,            'WS_ERR_INVALID_UTF8'          );        }         this.emit('message', buf.toString());      }    }     this._state = GET_INFO;  }   /**   * Handles a control message.   *   * @param {Buffer} data Data to handle   * @return {(Error|RangeError|undefined)} A possible error   * @private   */  controlMessage(data) {    if (this._opcode === 0x08) {      this._loop = false;       if (data.length === 0) {        this.emit('conclude', 1005, '');        this.end();      } else if (data.length === 1) {        return error(          RangeError,          'invalid payload length 1',          true,          1002,          'WS_ERR_INVALID_CONTROL_PAYLOAD_LENGTH'        );      } else {        const code = data.readUInt16BE(0);         if (!isValidStatusCode(code)) {          return error(            RangeError,            `invalid status code ${code}`,            true,            1002,            'WS_ERR_INVALID_CLOSE_CODE'          );        }         const buf = data.slice(2);         if (!isValidUTF8(buf)) {          return error(            Error,            'invalid UTF-8 sequence',            true,            1007,            'WS_ERR_INVALID_UTF8'          );        }         this.emit('conclude', code, buf.toString());        this.end();      }    } else if (this._opcode === 0x09) {      this.emit('ping', data);    } else {      this.emit('pong', data);    }     this._state = GET_INFO;  }} module.exports = Receiver; /** * Builds an error object. * * @param {function(new:Error|RangeError)} ErrorCtor The error constructor * @param {String} message The error message * @param {Boolean} prefix Specifies whether or not to add a default prefix to *     `message` * @param {Number} statusCode The status code * @param {String} errorCode The exposed error code * @return {(Error|RangeError)} The error * @private */function error(ErrorCtor, message, prefix, statusCode, errorCode) {  const err = new ErrorCtor(    prefix ? `Invalid WebSocket frame: ${message}` : message  );   Error.captureStackTrace(err, error);  err.code = errorCode;  err[kStatusCode] = statusCode;  return err;}