mirror of https://github.com/gchq/CyberChef.git
124 lines
3.4 KiB
JavaScript
124 lines
3.4 KiB
JavaScript
/**
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* @author n1474335 [n1474335@gmail.com]
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* @copyright Crown Copyright 2017
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* @license Apache-2.0
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*/
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import Operation from "../Operation";
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import Utils from "../Utils";
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import OperationError from "../errors/OperationError";
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import {ENCODING_SCHEME, ENCODING_LOOKUP, FORMAT} from "../lib/BCD";
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import BigNumber from "bignumber.js";
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/**
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* From BCD operation
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*/
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class FromBCD extends Operation {
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/**
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* FromBCD constructor
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*/
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constructor() {
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super();
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this.name = "From BCD";
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this.module = "Default";
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this.description = "Binary-Coded Decimal (BCD) is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of bits, usually four or eight. Special bit patterns are sometimes used for a sign.";
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this.infoURL = "https://wikipedia.org/wiki/Binary-coded_decimal";
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this.inputType = "string";
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this.outputType = "BigNumber";
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this.args = [
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{
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"name": "Scheme",
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"type": "option",
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"value": ENCODING_SCHEME
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},
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{
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"name": "Packed",
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"type": "boolean",
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"value": true
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},
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{
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"name": "Signed",
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"type": "boolean",
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"value": false
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},
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{
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"name": "Input format",
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"type": "option",
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"value": FORMAT
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}
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];
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this.patterns = [
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{
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match: "^(?:\\d{4} ){3,}\\d{4}$",
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flags: "",
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args: ["8 4 2 1", true, false, "Nibbles"]
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},
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];
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}
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/**
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* @param {string} input
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* @param {Object[]} args
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* @returns {BigNumber}
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*/
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run(input, args) {
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const encoding = ENCODING_LOOKUP[args[0]],
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packed = args[1],
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signed = args[2],
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inputFormat = args[3],
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nibbles = [];
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let output = "",
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byteArray;
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// Normalise the input
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switch (inputFormat) {
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case "Nibbles":
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case "Bytes":
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input = input.replace(/\s/g, "");
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for (let i = 0; i < input.length; i += 4) {
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nibbles.push(parseInt(input.substr(i, 4), 2));
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}
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break;
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case "Raw":
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default:
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byteArray = Utils.strToByteArray(input);
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byteArray.forEach(b => {
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nibbles.push(b >>> 4);
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nibbles.push(b & 15);
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});
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break;
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}
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if (!packed) {
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// Discard each high nibble
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for (let i = 0; i < nibbles.length; i++) {
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nibbles.splice(i, 1);
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}
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}
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if (signed) {
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const sign = nibbles.pop();
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if (sign === 13 ||
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sign === 11) {
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// Negative
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output += "-";
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}
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}
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nibbles.forEach(n => {
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if (isNaN(n)) throw new OperationError("Invalid input");
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const val = encoding.indexOf(n);
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if (val < 0) throw new OperationError(`Value ${Utils.bin(n, 4)} is not in the encoding scheme`);
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output += val.toString();
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});
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return new BigNumber(output);
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}
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}
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export default FromBCD;
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