139 lines
3.3 KiB
JavaScript
139 lines
3.3 KiB
JavaScript
'use strict'
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const { maxUnsigned16Bit, opcodes } = require('./constants')
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const BUFFER_SIZE = 8 * 1024
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/** @type {import('crypto')} */
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let crypto
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let buffer = null
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let bufIdx = BUFFER_SIZE
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try {
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crypto = require('node:crypto')
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/* c8 ignore next 3 */
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} catch {
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crypto = {
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// not full compatibility, but minimum.
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randomFillSync: function randomFillSync (buffer, _offset, _size) {
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for (let i = 0; i < buffer.length; ++i) {
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buffer[i] = Math.random() * 255 | 0
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}
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return buffer
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}
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}
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}
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function generateMask () {
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if (bufIdx === BUFFER_SIZE) {
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bufIdx = 0
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crypto.randomFillSync((buffer ??= Buffer.allocUnsafeSlow(BUFFER_SIZE)), 0, BUFFER_SIZE)
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}
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return [buffer[bufIdx++], buffer[bufIdx++], buffer[bufIdx++], buffer[bufIdx++]]
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}
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class WebsocketFrameSend {
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/**
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* @param {Buffer|undefined} data
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*/
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constructor (data) {
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this.frameData = data
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}
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createFrame (opcode) {
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const frameData = this.frameData
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const maskKey = generateMask()
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const bodyLength = frameData?.byteLength ?? 0
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/** @type {number} */
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let payloadLength = bodyLength // 0-125
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let offset = 6
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if (bodyLength > maxUnsigned16Bit) {
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offset += 8 // payload length is next 8 bytes
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payloadLength = 127
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} else if (bodyLength > 125) {
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offset += 2 // payload length is next 2 bytes
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payloadLength = 126
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}
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const buffer = Buffer.allocUnsafe(bodyLength + offset)
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// Clear first 2 bytes, everything else is overwritten
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buffer[0] = buffer[1] = 0
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buffer[0] |= 0x80 // FIN
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buffer[0] = (buffer[0] & 0xF0) + opcode // opcode
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/*! ws. MIT License. Einar Otto Stangvik <einaros@gmail.com> */
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buffer[offset - 4] = maskKey[0]
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buffer[offset - 3] = maskKey[1]
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buffer[offset - 2] = maskKey[2]
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buffer[offset - 1] = maskKey[3]
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buffer[1] = payloadLength
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if (payloadLength === 126) {
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buffer.writeUInt16BE(bodyLength, 2)
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} else if (payloadLength === 127) {
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// Clear extended payload length
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buffer[2] = buffer[3] = 0
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buffer.writeUIntBE(bodyLength, 4, 6)
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}
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buffer[1] |= 0x80 // MASK
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// mask body
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for (let i = 0; i < bodyLength; ++i) {
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buffer[offset + i] = frameData[i] ^ maskKey[i & 3]
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}
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return buffer
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}
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/**
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* @param {Uint8Array} buffer
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*/
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static createFastTextFrame (buffer) {
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const maskKey = generateMask()
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const bodyLength = buffer.length
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// mask body
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for (let i = 0; i < bodyLength; ++i) {
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buffer[i] ^= maskKey[i & 3]
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}
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let payloadLength = bodyLength
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let offset = 6
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if (bodyLength > maxUnsigned16Bit) {
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offset += 8 // payload length is next 8 bytes
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payloadLength = 127
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} else if (bodyLength > 125) {
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offset += 2 // payload length is next 2 bytes
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payloadLength = 126
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}
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const head = Buffer.allocUnsafeSlow(offset)
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head[0] = 0x80 /* FIN */ | opcodes.TEXT /* opcode TEXT */
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head[1] = payloadLength | 0x80 /* MASK */
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head[offset - 4] = maskKey[0]
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head[offset - 3] = maskKey[1]
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head[offset - 2] = maskKey[2]
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head[offset - 1] = maskKey[3]
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if (payloadLength === 126) {
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head.writeUInt16BE(bodyLength, 2)
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} else if (payloadLength === 127) {
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head[2] = head[3] = 0
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head.writeUIntBE(bodyLength, 4, 6)
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}
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return [head, buffer]
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}
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}
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module.exports = {
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WebsocketFrameSend
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}
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