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