mirror of https://github.com/gchq/CyberChef.git
106 lines
3.3 KiB
JavaScript
106 lines
3.3 KiB
JavaScript
/**
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* @author PenguinGeorge [george@penguingeorge.com]
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* @copyright Crown Copyright 2018
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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 OperationError from "../errors/OperationError";
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import Utils from "../Utils";
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import {alphabetName, ALPHABET_OPTIONS} from "../lib/Base85";
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/**
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* From Base85 operation
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*/
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class FromBase85 extends Operation {
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/**
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* From Base85 constructor
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*/
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constructor() {
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super();
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this.name = "From Base85";
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this.module = "Default";
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this.description = "Base85 (also called Ascii85) is a notation for encoding arbitrary byte data. It is usually more efficient that Base64.<br><br>This operation decodes data from an ASCII string (with an alphabet of your choosing, presets included).<br><br>e.g. <code>BOu!rD]j7BEbo7</code> becomes <code>hello world</code><br><br>Base85 is commonly used in Adobe's PostScript and PDF file formats.";
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this.infoURL = "https://wikipedia.org/wiki/Ascii85";
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this.inputType = "string";
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this.outputType = "byteArray";
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this.args = [
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{
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name: "Alphabet",
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type: "editableOption",
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value: ALPHABET_OPTIONS
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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 {byteArray}
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*/
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run(input, args) {
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const alphabet = Utils.expandAlphRange(args[0]).join(""),
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encoding = alphabetName(alphabet),
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result = [];
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if (alphabet.length !== 85 ||
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[].unique.call(alphabet).length !== 85) {
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throw new OperationError("Alphabet must be of length 85");
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}
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if (input.length === 0) return [];
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const matches = input.match(/<~(.+?)~>/);
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if (matches !== null) input = matches[1];
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let i = 0;
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let block, blockBytes;
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while (i < input.length) {
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if (encoding === "Standard" && input[i] === "z") {
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result.push(0, 0, 0, 0);
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i++;
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} else {
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let digits = [];
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digits = input
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.substr(i, 5)
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.split("")
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.map((chr, idx) => {
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const digit = alphabet.indexOf(chr);
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if (digit < 0 || digit > 84) {
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throw `Invalid character '${chr}' at index ${idx}`;
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}
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return digit;
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});
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block =
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digits[0] * 52200625 +
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digits[1] * 614125 +
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(i + 2 < input.length ? digits[2] : 84) * 7225 +
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(i + 3 < input.length ? digits[3] : 84) * 85 +
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(i + 4 < input.length ? digits[4] : 84);
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blockBytes = [
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(block >> 24) & 0xff,
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(block >> 16) & 0xff,
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(block >> 8) & 0xff,
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block & 0xff
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];
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if (input.length < i + 5) {
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blockBytes.splice(input.length - (i + 5), 5);
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}
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result.push.apply(result, blockBytes);
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i += 5;
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}
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}
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return result;
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}
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}
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export default FromBase85;
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