mirror of https://github.com/gchq/CyberChef.git
131 lines
3.0 KiB
JavaScript
Executable File
131 lines
3.0 KiB
JavaScript
Executable File
/**
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* Checksum operations.
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*
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* @author n1474335 [n1474335@gmail.com]
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* @copyright Crown Copyright 2016
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* @license Apache-2.0
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*
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* @namespace
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*/
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var Checksum = {
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/**
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* Fletcher-16 Checksum operation.
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*
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* @param {byte_array} input
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* @param {Object[]} args
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* @returns {string}
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*/
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run_fletcher16: function(input, args) {
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var a = 0,
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b = 0;
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for (var i = 0; i < input.length; i++) {
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a = (a + input[i]) % 0xff;
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b = (b + a) % 0xff;
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}
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return Utils.hex(((b << 8) | a) >>> 0, 4);
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},
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/**
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* Adler-32 Checksum operation.
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*
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* @param {byte_array} input
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* @param {Object[]} args
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* @returns {string}
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*/
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run_adler32: function(input, args) {
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var MOD_ADLER = 65521,
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a = 1,
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b = 0;
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for (var i = 0; i < input.length; i++) {
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a += input[i];
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b += a;
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}
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a %= MOD_ADLER;
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b %= MOD_ADLER;
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return Utils.hex(((b << 16) | a) >>> 0, 8);
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},
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/**
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* CRC-32 Checksum operation.
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*
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* @param {byte_array} input
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* @param {Object[]} args
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* @returns {string}
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*/
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run_crc32: function(input, args) {
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var crc_table = window.crc_table || (window.crc_table = Checksum._gen_crc_table()),
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crc = 0 ^ (-1);
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for (var i = 0; i < input.length; i++) {
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crc = (crc >>> 8) ^ crc_table[(crc ^ input[i]) & 0xff];
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}
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return Utils.hex((crc ^ (-1)) >>> 0);
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},
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/**
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* TCP/IP Checksum operation.
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*
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* @author GCHQ Contributor [1]
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* @param {byte_array} input
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* @param {Object[]} args
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* @returns {string}
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*
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* @example
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* // returns '3f2c'
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* Checksum.run_tcp_ip([0x45,0x00,0x00,0x87,0xa3,0x1b,0x40,0x00,0x40,0x06,
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* 0x00,0x00,0xac,0x11,0x00,0x04,0xac,0x11,0x00,0x03])
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*
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* // returns 'a249'
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* Checksum.run_tcp_ip([0x45,0x00,0x01,0x11,0x3f,0x74,0x40,0x00,0x40,0x06,
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* 0x00,0x00,0xac,0x11,0x00,0x03,0xac,0x11,0x00,0x04])
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*/
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run_tcp_ip: function(input, args) {
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var csum = 0;
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for (var i = 0; i < input.length; i++) {
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if(i % 2 === 0) {
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csum += (input[i] << 8);
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} else {
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csum += input[i];
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}
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}
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csum = (csum >> 16) + (csum & 0xffff);
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return Utils.hex(0xffff - csum);
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},
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/**
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* Generates a CRC table for use with CRC checksums.
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*
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* @private
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* @returns {array}
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*/
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_gen_crc_table: function() {
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var c,
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crc_table = [];
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for (var n = 0; n < 256; n++) {
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c = n;
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for (var k = 0; k < 8; k++) {
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c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1));
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}
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crc_table[n] = c;
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}
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return crc_table;
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},
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};
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