'use strict';
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const Limiter = require('async-limiter');
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const zlib = require('zlib');
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const bufferUtil = require('./buffer-util');
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const { kStatusCode, NOOP } = require('./constants');
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const TRAILER = Buffer.from([0x00, 0x00, 0xff, 0xff]);
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const EMPTY_BLOCK = Buffer.from([0x00]);
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const kPerMessageDeflate = Symbol('permessage-deflate');
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const kTotalLength = Symbol('total-length');
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const kCallback = Symbol('callback');
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const kBuffers = Symbol('buffers');
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const kError = Symbol('error');
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//
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// We limit zlib concurrency, which prevents severe memory fragmentation
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// as documented in https://github.com/nodejs/node/issues/8871#issuecomment-250915913
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// and https://github.com/websockets/ws/issues/1202
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//
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// Intentionally global; it's the global thread pool that's an issue.
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//
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let zlibLimiter;
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/**
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* permessage-deflate implementation.
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*/
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class PerMessageDeflate {
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/**
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* Creates a PerMessageDeflate instance.
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*
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* @param {Object} options Configuration options
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* @param {Boolean} options.serverNoContextTakeover Request/accept disabling
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* of server context takeover
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* @param {Boolean} options.clientNoContextTakeover Advertise/acknowledge
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* disabling of client context takeover
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* @param {(Boolean|Number)} options.serverMaxWindowBits Request/confirm the
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* use of a custom server window size
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* @param {(Boolean|Number)} options.clientMaxWindowBits Advertise support
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* for, or request, a custom client window size
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* @param {Object} options.zlibDeflateOptions Options to pass to zlib on deflate
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* @param {Object} options.zlibInflateOptions Options to pass to zlib on inflate
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* @param {Number} options.threshold Size (in bytes) below which messages
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* should not be compressed
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* @param {Number} options.concurrencyLimit The number of concurrent calls to
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* zlib
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* @param {Boolean} isServer Create the instance in either server or client
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* mode
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* @param {Number} maxPayload The maximum allowed message length
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*/
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constructor(options, isServer, maxPayload) {
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this._maxPayload = maxPayload | 0;
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this._options = options || {};
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this._threshold =
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this._options.threshold !== undefined ? this._options.threshold : 1024;
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this._isServer = !!isServer;
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this._deflate = null;
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this._inflate = null;
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this.params = null;
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if (!zlibLimiter) {
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const concurrency =
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this._options.concurrencyLimit !== undefined
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? this._options.concurrencyLimit
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: 10;
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zlibLimiter = new Limiter({ concurrency });
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}
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}
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/**
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* @type {String}
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*/
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static get extensionName() {
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return 'permessage-deflate';
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}
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/**
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* Create an extension negotiation offer.
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*
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* @return {Object} Extension parameters
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* @public
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*/
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offer() {
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const params = {};
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if (this._options.serverNoContextTakeover) {
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params.server_no_context_takeover = true;
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}
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if (this._options.clientNoContextTakeover) {
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params.client_no_context_takeover = true;
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}
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if (this._options.serverMaxWindowBits) {
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params.server_max_window_bits = this._options.serverMaxWindowBits;
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}
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if (this._options.clientMaxWindowBits) {
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params.client_max_window_bits = this._options.clientMaxWindowBits;
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} else if (this._options.clientMaxWindowBits == null) {
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params.client_max_window_bits = true;
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}
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return params;
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}
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/**
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* Accept an extension negotiation offer/response.
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*
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* @param {Array} configurations The extension negotiation offers/reponse
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* @return {Object} Accepted configuration
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* @public
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*/
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accept(configurations) {
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configurations = this.normalizeParams(configurations);
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this.params = this._isServer
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? this.acceptAsServer(configurations)
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: this.acceptAsClient(configurations);
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return this.params;
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}
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/**
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* Releases all resources used by the extension.
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*
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* @public
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*/
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cleanup() {
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if (this._inflate) {
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this._inflate.close();
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this._inflate = null;
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}
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if (this._deflate) {
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this._deflate.close();
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this._deflate = null;
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}
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}
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/**
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* Accept an extension negotiation offer.
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*
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* @param {Array} offers The extension negotiation offers
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* @return {Object} Accepted configuration
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* @private
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*/
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acceptAsServer(offers) {
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const opts = this._options;
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const accepted = offers.find((params) => {
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if (
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(opts.serverNoContextTakeover === false &&
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params.server_no_context_takeover) ||
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(params.server_max_window_bits &&
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(opts.serverMaxWindowBits === false ||
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(typeof opts.serverMaxWindowBits === 'number' &&
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opts.serverMaxWindowBits > params.server_max_window_bits))) ||
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(typeof opts.clientMaxWindowBits === 'number' &&
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!params.client_max_window_bits)
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) {
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return false;
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}
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return true;
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});
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if (!accepted) {
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throw new Error('None of the extension offers can be accepted');
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}
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if (opts.serverNoContextTakeover) {
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accepted.server_no_context_takeover = true;
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}
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if (opts.clientNoContextTakeover) {
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accepted.client_no_context_takeover = true;
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}
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if (typeof opts.serverMaxWindowBits === 'number') {
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accepted.server_max_window_bits = opts.serverMaxWindowBits;
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}
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if (typeof opts.clientMaxWindowBits === 'number') {
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accepted.client_max_window_bits = opts.clientMaxWindowBits;
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} else if (
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accepted.client_max_window_bits === true ||
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opts.clientMaxWindowBits === false
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) {
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delete accepted.client_max_window_bits;
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}
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return accepted;
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}
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/**
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* Accept the extension negotiation response.
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*
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* @param {Array} response The extension negotiation response
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* @return {Object} Accepted configuration
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* @private
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*/
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acceptAsClient(response) {
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const params = response[0];
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if (
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this._options.clientNoContextTakeover === false &&
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params.client_no_context_takeover
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) {
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throw new Error('Unexpected parameter "client_no_context_takeover"');
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}
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if (!params.client_max_window_bits) {
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if (typeof this._options.clientMaxWindowBits === 'number') {
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params.client_max_window_bits = this._options.clientMaxWindowBits;
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}
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} else if (
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this._options.clientMaxWindowBits === false ||
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(typeof this._options.clientMaxWindowBits === 'number' &&
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params.client_max_window_bits > this._options.clientMaxWindowBits)
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) {
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throw new Error(
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'Unexpected or invalid parameter "client_max_window_bits"'
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);
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}
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return params;
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}
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/**
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* Normalize parameters.
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*
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* @param {Array} configurations The extension negotiation offers/reponse
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* @return {Array} The offers/response with normalized parameters
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* @private
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*/
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normalizeParams(configurations) {
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configurations.forEach((params) => {
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Object.keys(params).forEach((key) => {
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var value = params[key];
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if (value.length > 1) {
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throw new Error(`Parameter "${key}" must have only a single value`);
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}
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value = value[0];
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if (key === 'client_max_window_bits') {
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if (value !== true) {
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const num = +value;
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if (!Number.isInteger(num) || num < 8 || num > 15) {
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throw new TypeError(
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`Invalid value for parameter "${key}": ${value}`
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);
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}
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value = num;
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} else if (!this._isServer) {
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throw new TypeError(
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`Invalid value for parameter "${key}": ${value}`
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);
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}
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} else if (key === 'server_max_window_bits') {
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const num = +value;
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if (!Number.isInteger(num) || num < 8 || num > 15) {
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throw new TypeError(
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`Invalid value for parameter "${key}": ${value}`
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);
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}
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value = num;
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} else if (
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key === 'client_no_context_takeover' ||
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key === 'server_no_context_takeover'
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) {
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if (value !== true) {
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throw new TypeError(
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`Invalid value for parameter "${key}": ${value}`
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);
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}
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} else {
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throw new Error(`Unknown parameter "${key}"`);
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}
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params[key] = value;
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});
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});
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return configurations;
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}
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/**
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* Decompress data. Concurrency limited by async-limiter.
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*
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* @param {Buffer} data Compressed data
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* @param {Boolean} fin Specifies whether or not this is the last fragment
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* @param {Function} callback Callback
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* @public
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*/
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decompress(data, fin, callback) {
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zlibLimiter.push((done) => {
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this._decompress(data, fin, (err, result) => {
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done();
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callback(err, result);
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});
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});
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}
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/**
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* Compress data. Concurrency limited by async-limiter.
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*
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* @param {Buffer} data Data to compress
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* @param {Boolean} fin Specifies whether or not this is the last fragment
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* @param {Function} callback Callback
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* @public
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*/
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compress(data, fin, callback) {
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zlibLimiter.push((done) => {
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this._compress(data, fin, (err, result) => {
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done();
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callback(err, result);
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});
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});
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}
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/**
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* Decompress data.
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*
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* @param {Buffer} data Compressed data
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* @param {Boolean} fin Specifies whether or not this is the last fragment
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* @param {Function} callback Callback
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* @private
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*/
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_decompress(data, fin, callback) {
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const endpoint = this._isServer ? 'client' : 'server';
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if (!this._inflate) {
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const key = `${endpoint}_max_window_bits`;
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const windowBits =
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typeof this.params[key] !== 'number'
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? zlib.Z_DEFAULT_WINDOWBITS
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: this.params[key];
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this._inflate = zlib.createInflateRaw(
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Object.assign({}, this._options.zlibInflateOptions, { windowBits })
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);
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this._inflate[kPerMessageDeflate] = this;
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this._inflate[kTotalLength] = 0;
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this._inflate[kBuffers] = [];
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this._inflate.on('error', inflateOnError);
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this._inflate.on('data', inflateOnData);
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}
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this._inflate[kCallback] = callback;
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this._inflate.write(data);
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if (fin) this._inflate.write(TRAILER);
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this._inflate.flush(() => {
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const err = this._inflate[kError];
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if (err) {
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this._inflate.close();
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this._inflate = null;
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callback(err);
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return;
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}
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const data = bufferUtil.concat(
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this._inflate[kBuffers],
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this._inflate[kTotalLength]
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);
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if (fin && this.params[`${endpoint}_no_context_takeover`]) {
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this._inflate.close();
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this._inflate = null;
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} else {
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this._inflate[kTotalLength] = 0;
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this._inflate[kBuffers] = [];
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}
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callback(null, data);
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});
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}
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/**
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* Compress data.
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*
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* @param {Buffer} data Data to compress
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* @param {Boolean} fin Specifies whether or not this is the last fragment
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* @param {Function} callback Callback
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* @private
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*/
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_compress(data, fin, callback) {
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if (!data || data.length === 0) {
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process.nextTick(callback, null, EMPTY_BLOCK);
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return;
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}
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const endpoint = this._isServer ? 'server' : 'client';
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if (!this._deflate) {
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const key = `${endpoint}_max_window_bits`;
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const windowBits =
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typeof this.params[key] !== 'number'
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? zlib.Z_DEFAULT_WINDOWBITS
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: this.params[key];
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this._deflate = zlib.createDeflateRaw(
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Object.assign({}, this._options.zlibDeflateOptions, { windowBits })
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);
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this._deflate[kTotalLength] = 0;
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this._deflate[kBuffers] = [];
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//
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// An `'error'` event is emitted, only on Node.js < 10.0.0, if the
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// `zlib.DeflateRaw` instance is closed while data is being processed.
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// This can happen if `PerMessageDeflate#cleanup()` is called at the wrong
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// time due to an abnormal WebSocket closure.
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//
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this._deflate.on('error', NOOP);
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this._deflate.on('data', deflateOnData);
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}
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this._deflate.write(data);
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this._deflate.flush(zlib.Z_SYNC_FLUSH, () => {
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if (!this._deflate) {
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//
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// This `if` statement is only needed for Node.js < 10.0.0 because as of
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// commit https://github.com/nodejs/node/commit/5e3f5164, the flush
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// callback is no longer called if the deflate stream is closed while
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// data is being processed.
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//
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return;
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}
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var data = bufferUtil.concat(
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this._deflate[kBuffers],
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this._deflate[kTotalLength]
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);
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if (fin) data = data.slice(0, data.length - 4);
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if (fin && this.params[`${endpoint}_no_context_takeover`]) {
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this._deflate.close();
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this._deflate = null;
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} else {
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this._deflate[kTotalLength] = 0;
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this._deflate[kBuffers] = [];
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}
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callback(null, data);
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});
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}
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}
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module.exports = PerMessageDeflate;
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/**
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* The listener of the `zlib.DeflateRaw` stream `'data'` event.
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*
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* @param {Buffer} chunk A chunk of data
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* @private
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*/
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function deflateOnData(chunk) {
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this[kBuffers].push(chunk);
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this[kTotalLength] += chunk.length;
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}
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/**
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* The listener of the `zlib.InflateRaw` stream `'data'` event.
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*
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* @param {Buffer} chunk A chunk of data
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* @private
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*/
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function inflateOnData(chunk) {
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this[kTotalLength] += chunk.length;
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if (
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this[kPerMessageDeflate]._maxPayload < 1 ||
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this[kTotalLength] <= this[kPerMessageDeflate]._maxPayload
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) {
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this[kBuffers].push(chunk);
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return;
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}
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this[kError] = new RangeError('Max payload size exceeded');
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this[kError][kStatusCode] = 1009;
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this.removeListener('data', inflateOnData);
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this.reset();
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}
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/**
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* The listener of the `zlib.InflateRaw` stream `'error'` event.
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*
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* @param {Error} err The emitted error
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* @private
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*/
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function inflateOnError(err) {
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//
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// There is no need to call `Zlib#close()` as the handle is automatically
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// closed when an error is emitted.
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//
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this[kPerMessageDeflate]._inflate = null;
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err[kStatusCode] = 1007;
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this[kCallback](err);
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}
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