cyberchef
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The Cyber Swiss Army Knife for encryption, encoding, compression and data analysis.
370 lines (349 loc) • 11.4 kB
JavaScript
/**
* Emulation of the Enigma machine.
*
* @author s2224834
* @copyright Crown Copyright 2019
* @license Apache-2.0
*/
import OperationError from "../errors/OperationError.mjs";
import Utils from "../Utils.mjs";
/**
* Provided default Enigma rotor set.
* These are specified as a list of mappings from the letters A through Z in order, optionally
* followed by < and a list of letters at which the rotor steps.
*/
export const ROTORS = [
{name: "I", value: "EKMFLGDQVZNTOWYHXUSPAIBRCJ<R"},
{name: "II", value: "AJDKSIRUXBLHWTMCQGZNPYFVOE<F"},
{name: "III", value: "BDFHJLCPRTXVZNYEIWGAKMUSQO<W"},
{name: "IV", value: "ESOVPZJAYQUIRHXLNFTGKDCMWB<K"},
{name: "V", value: "VZBRGITYUPSDNHLXAWMJQOFECK<A"},
{name: "VI", value: "JPGVOUMFYQBENHZRDKASXLICTW<AN"},
{name: "VII", value: "NZJHGRCXMYSWBOUFAIVLPEKQDT<AN"},
{name: "VIII", value: "FKQHTLXOCBJSPDZRAMEWNIUYGV<AN"},
];
export const ROTORS_FOURTH = [
{name: "Beta", value: "LEYJVCNIXWPBQMDRTAKZGFUHOS"},
{name: "Gamma", value: "FSOKANUERHMBTIYCWLQPZXVGJD"},
];
/**
* Provided default Enigma reflector set.
* These are specified as 13 space-separated transposed pairs covering every letter.
*/
export const REFLECTORS = [
{name: "B", value: "AY BR CU DH EQ FS GL IP JX KN MO TZ VW"},
{name: "C", value: "AF BV CP DJ EI GO HY KR LZ MX NW TQ SU"},
{name: "B Thin", value: "AE BN CK DQ FU GY HW IJ LO MP RX SZ TV"},
{name: "C Thin", value: "AR BD CO EJ FN GT HK IV LM PW QZ SX UY"},
];
export const LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
/**
* Map a letter to a number in 0..25.
*
* @param {char} c
* @param {boolean} permissive - Case insensitive; don't throw errors on other chars.
* @returns {number}
*/
export function a2i(c, permissive=false) {
const i = Utils.ord(c);
if (i >= 65 && i <= 90) {
return i - 65;
}
if (permissive) {
// Allow case insensitivity
if (i >= 97 && i <= 122) {
return i - 97;
}
return -1;
}
throw new OperationError("a2i called on non-uppercase ASCII character");
}
/**
* Map a number in 0..25 to a letter.
*
* @param {number} i
* @returns {char}
*/
export function i2a(i) {
if (i >= 0 && i < 26) {
return Utils.chr(i+65);
}
throw new OperationError("i2a called on value outside 0..25");
}
/**
* A rotor in the Enigma machine.
*/
export class Rotor {
/**
* Rotor constructor.
*
* @param {string} wiring - A 26 character string of the wiring order.
* @param {string} steps - A 0..26 character string of stepping points.
* @param {char} ringSetting - The ring setting.
* @param {char} initialPosition - The initial position of the rotor.
*/
constructor(wiring, steps, ringSetting, initialPosition) {
if (!/^[A-Z]{26}$/.test(wiring)) {
throw new OperationError("Rotor wiring must be 26 unique uppercase letters");
}
if (!/^[A-Z]{0,26}$/.test(steps)) {
throw new OperationError("Rotor steps must be 0-26 unique uppercase letters");
}
if (!/^[A-Z]$/.test(ringSetting)) {
throw new OperationError("Rotor ring setting must be exactly one uppercase letter");
}
if (!/^[A-Z]$/.test(initialPosition)) {
throw new OperationError("Rotor initial position must be exactly one uppercase letter");
}
this.map = new Array(26);
this.revMap = new Array(26);
const uniq = {};
for (let i=0; i<LETTERS.length; i++) {
const a = a2i(LETTERS[i]);
const b = a2i(wiring[i]);
this.map[a] = b;
this.revMap[b] = a;
uniq[b] = true;
}
if (Object.keys(uniq).length !== LETTERS.length) {
throw new OperationError("Rotor wiring must have each letter exactly once");
}
const rs = a2i(ringSetting);
this.steps = new Set();
for (const x of steps) {
this.steps.add(Utils.mod(a2i(x) - rs, 26));
}
if (this.steps.size !== steps.length) {
// This isn't strictly fatal, but it's probably a mistake
throw new OperationError("Rotor steps must be unique");
}
this.pos = Utils.mod(a2i(initialPosition) - rs, 26);
}
/**
* Step the rotor forward by one.
*/
step() {
this.pos = Utils.mod(this.pos + 1, 26);
return this.pos;
}
/**
* Transform a character through this rotor forwards.
*
* @param {number} c - The character.
* @returns {number}
*/
transform(c) {
return Utils.mod(this.map[Utils.mod(c + this.pos, 26)] - this.pos, 26);
}
/**
* Transform a character through this rotor backwards.
*
* @param {number} c - The character.
* @returns {number}
*/
revTransform(c) {
return Utils.mod(this.revMap[Utils.mod(c + this.pos, 26)] - this.pos, 26);
}
}
/**
* Base class for plugboard and reflector (since these do effectively the same
* thing).
*/
class PairMapBase {
/**
* PairMapBase constructor.
*
* @param {string} pairs - A whitespace separated string of letter pairs to swap.
* @param {string} [name='PairMapBase'] - For errors, the name of this object.
*/
constructor(pairs, name="PairMapBase") {
// I've chosen to make whitespace significant here to make a) code and
// b) inputs easier to read
this.pairs = pairs;
this.map = {};
if (pairs === "") {
return;
}
pairs.split(/\s+/).forEach(pair => {
if (!/^[A-Z]{2}$/.test(pair)) {
throw new OperationError(name + " must be a whitespace-separated list of uppercase letter pairs");
}
const a = a2i(pair[0]), b = a2i(pair[1]);
if (a === b) {
// self-stecker
return;
}
if (Object.prototype.hasOwnProperty.call(this.map, a)) {
throw new OperationError(`${name} connects ${pair[0]} more than once`);
}
if (Object.prototype.hasOwnProperty.call(this.map, b)) {
throw new OperationError(`${name} connects ${pair[1]} more than once`);
}
this.map[a] = b;
this.map[b] = a;
});
}
/**
* Transform a character through this object.
* Returns other characters unchanged.
*
* @param {number} c - The character.
* @returns {number}
*/
transform(c) {
if (!Object.prototype.hasOwnProperty.call(this.map, c)) {
return c;
}
return this.map[c];
}
/**
* Alias for transform, to allow interchangeable use with rotors.
*
* @param {number} c - The character.
* @returns {number}
*/
revTransform(c) {
return this.transform(c);
}
}
/**
* Reflector. PairMapBase but requires that all characters are accounted for.
*
* Includes a couple of optimisations on that basis.
*/
export class Reflector extends PairMapBase {
/**
* Reflector constructor. See PairMapBase.
* Additional restriction: every character must be accounted for.
*/
constructor(pairs) {
super(pairs, "Reflector");
const s = Object.keys(this.map).length;
if (s !== 26) {
throw new OperationError("Reflector must have exactly 13 pairs covering every letter");
}
const optMap = new Array(26);
for (const x of Object.keys(this.map)) {
optMap[x] = this.map[x];
}
this.map = optMap;
}
/**
* Transform a character through this object.
*
* @param {number} c - The character.
* @returns {number}
*/
transform(c) {
return this.map[c];
}
}
/**
* Plugboard. Unmodified PairMapBase.
*/
export class Plugboard extends PairMapBase {
/**
* Plugboard constructor. See PairMapbase.
*/
constructor(pairs) {
super(pairs, "Plugboard");
}
}
/**
* Base class for the Enigma machine itself. Holds rotors, a reflector, and a plugboard.
*/
export class EnigmaBase {
/**
* EnigmaBase constructor.
*
* @param {Object[]} rotors - List of Rotors.
* @param {Object} reflector - A Reflector.
* @param {Plugboard} plugboard - A Plugboard.
*/
constructor(rotors, reflector, plugboard) {
this.rotors = rotors;
this.rotorsRev = [].concat(rotors).reverse();
this.reflector = reflector;
this.plugboard = plugboard;
}
/**
* Step the rotors forward by one.
*
* This happens before the output character is generated.
*
* Note that rotor 4, if it's there, never steps.
*
* Why is all the logic in EnigmaBase and not a nice neat method on
* Rotor that knows when it should advance the next item?
* Because the double stepping anomaly is a thing. tl;dr if the left rotor
* should step the next time the middle rotor steps, the middle rotor will
* immediately step.
*/
step() {
const r0 = this.rotors[0];
const r1 = this.rotors[1];
r0.step();
// The second test here is the double-stepping anomaly
if (r0.steps.has(r0.pos) || r1.steps.has(Utils.mod(r1.pos + 1, 26))) {
r1.step();
if (r1.steps.has(r1.pos)) {
const r2 = this.rotors[2];
r2.step();
}
}
}
/**
* Encrypt (or decrypt) some data.
* Takes an arbitrary string and runs the Engima machine on that data from
* *its current state*, and outputs the result. Non-alphabetic characters
* are returned unchanged.
*
* @param {string} input - Data to encrypt.
* @returns {string}
*/
crypt(input) {
let result = "";
for (const c of input) {
let letter = a2i(c, true);
if (letter === -1) {
result += c;
continue;
}
// First, step the rotors forward.
this.step();
// Now, run through the plugboard.
letter = this.plugboard.transform(letter);
// Then through each wheel in sequence, through the reflector, and
// backwards through the wheels again.
for (const rotor of this.rotors) {
letter = rotor.transform(letter);
}
letter = this.reflector.transform(letter);
for (const rotor of this.rotorsRev) {
letter = rotor.revTransform(letter);
}
// Finally, back through the plugboard.
letter = this.plugboard.revTransform(letter);
result += i2a(letter);
}
return result;
}
}
/**
* The Enigma machine itself. Holds 3-4 rotors, a reflector, and a plugboard.
*/
export class EnigmaMachine extends EnigmaBase {
/**
* EnigmaMachine constructor.
*
* @param {Object[]} rotors - List of Rotors.
* @param {Object} reflector - A Reflector.
* @param {Plugboard} plugboard - A Plugboard.
*/
constructor(rotors, reflector, plugboard) {
super(rotors, reflector, plugboard);
if (rotors.length !== 3 && rotors.length !== 4) {
throw new OperationError("Enigma must have 3 or 4 rotors");
}
}
}