MeshCentral/rdp/security/rc4.js
2022-05-01 02:02:49 -07:00

70 lines
2.1 KiB
JavaScript

function RC4(key) {
this.privateKey = keySetup(key);
this.byteStream = byteStreamGenerator(this.privateKey.slice(0));
}
/**
* Converts the text into an array of the characters numeric Unicode values
* @param {String} text, the text to convert
* @return {Array} the array of Unicode values
*/
function convert(text) {
var codes = [];
for (var i = 0, ii = text.length; i < ii; i++) { codes.push(text.charCodeAt(i)); }
return codes;
}
/**
* Sets up the key to use with the byte stream
* @param {String} key, The key that you want to use
* @return {Array}, the key stream which with be used in the byteStreamGenerator
*/
function keySetup(key) {
var K = [...Array(256).keys()], j = 0, key = convert(key);
for (var i = 0, ii = K.length; i < ii; i++) {
j = (j + K[i] + key[i % key.length]) % 256;
[K[i], K[j]] = [K[j], K[i]];
}
return K;
}
/**
* byteStreamGenerator uses ES6 generators which will be 'XOR-ed' to encrypt and decrypt
* @param {Array} K, the array generated from the keySetup
* @yield {Integer}, the current value which will be 'XOR-ed' to encrypt or decrypt
*/
var byteStreamGenerator = function* (K) {
var i = 0, j = 0;
while (true) {
i = (i + 1) % 256;
j = (j + K[i]) % 256;
[K[i], K[j]] = [K[j], K[i]];
yield (K[(K[i] + K[j]) % 256]);
}
}
/**
* Encrypts the input text
* @param {String} input, the text to encrypt
* @return {String}, the encrypted text
*/
RC4.prototype.encrypt = function (input) {
var outputText = '';
for (var i = 0, ii = input.length; i < ii; i++) { outputText += ('00' + (input.charCodeAt(i) ^ this.byteStream.next().value).toString(16)).substr(-2); }
return outputText;
}
/**
* Decrypts the input text
* @param {String} input, the text to decrypt
* @return {String}, the decrypted text (if the same key was used)
*/
RC4.prototype.decrypt = function (input) {
var outputText = '';
input = input.match(/[a-z0-9]{2}/gi);
for (var i = 0, ii = input.length; i < ii; i++) { outputText += String.fromCharCode((parseInt(input[i], 16) ^ byteStream.next().value)); }
return outputText;
}
module.exports = RC4;