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receiver.js
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Wed, Jul 16, 01:57

receiver.js
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'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 FastBuffer = Buffer[Symbol.species];
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 {Object} [options] Options object
* @param {String} [options.binaryType=nodebuffer] The type for binary data
* @param {Object} [options.extensions] An object containing the negotiated
* extensions
* @param {Boolean} [options.isServer=false] Specifies whether to operate in
* client or server mode
* @param {Number} [options.maxPayload=0] The maximum allowed message length
* @param {Boolean} [options.skipUTF8Validation=false] Specifies whether or
* not to skip UTF-8 validation for text and close messages
*/
constructor(options = {}) {
super();
this._binaryType = options.binaryType || BINARY_TYPES[0];
this._extensions = options.extensions || {};
this._isServer = !!options.isServer;
this._maxPayload = options.maxPayload | 0;
this._skipUTF8Validation = !!options.skipUTF8Validation;
this[kWebSocket] = undefined;
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] = new FastBuffer(
buf.buffer,
buf.byteOffset + n,
buf.length - n
);
return new FastBuffer(buf.buffer, buf.byteOffset, 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] = new FastBuffer(
buf.buffer,
buf.byteOffset + n,
buf.length - 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._opcode === 0x08 && this._payloadLength === 1)
) {
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 &&
(this._mask[0] | this._mask[1] | this._mask[2] | this._mask[3]) !== 0
) {
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 length 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, true);
} else {
const buf = concat(fragments, messageLength);
if (!this._skipUTF8Validation && !isValidUTF8(buf)) {
this._loop = false;
return error(
Error,
'invalid UTF-8 sequence',
true,
1007,
'WS_ERR_INVALID_UTF8'
);
}
this.emit('message', buf, false);
}
}
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, EMPTY_BUFFER);
this.end();
} 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 = new FastBuffer(
data.buffer,
data.byteOffset + 2,
data.length - 2
);
if (!this._skipUTF8Validation && !isValidUTF8(buf)) {
return error(
Error,
'invalid UTF-8 sequence',
true,
1007,
'WS_ERR_INVALID_UTF8'
);
}
this.emit('conclude', code, buf);
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;
}

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