shamir/src/test/js/SchemeTests.js

A JavaScript implementation of Shamir's Secret Sharing algorithm over GF(256).

/*
 * Copyright © 2019 Simon Massey (massey1905@gmail.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const test = require('tape');

const { split, join } = require('../../main/js/Scheme.js');

const { randomBytes } = require('crypto');

/* eslint-disable prefer-arrow-callback */
/* eslint-disable func-names */
/* eslint-disable no-plusplus */
/* eslint-disable no-bitwise */

// https://codereview.stackexchange.com/a/3589/75693
function bytesToSring(bytes) {
  const chars = [];
  for (let i = 0, n = bytes.length; i < n;) {
    chars.push(((bytes[i++] & 0xff) << 8) | (bytes[i++] & 0xff));
  }
  return String.fromCharCode.apply(null, chars);
}


// https://codereview.stackexchange.com/a/3589/75693
function stringToBytes(str) {
  const bytes = [];
  for (let i = 0, n = str.length; i < n; i++) {
    const char = str.charCodeAt(i);
    bytes.push(char >>> 8, char & 0xff);
  }
  return bytes;
}

test('SchemeTests roundtrip', function (t) {
  const parts = 5;
  const quorum = 3;

  // http://kermitproject.org/utf8.html
  // From the Anglo-Saxon Rune Poem (Rune version)
  const secretUtf8 = `ᚠᛇᚻ᛫ᛒᛦᚦ᛫ᚠᚱᚩᚠᚢᚱ᛫ᚠᛁᚱᚪ᛫ᚷᛖᚻᚹᛦᛚᚳᚢᛗ
ᛋᚳᛖᚪᛚ᛫ᚦᛖᚪᚻ᛫ᛗᚪᚾᚾᚪ᛫ᚷᛖᚻᚹᛦᛚᚳ᛫ᛗᛁᚳᛚᚢᚾ᛫ᚻᛦᛏ᛫ᛞᚫᛚᚪᚾ
ᚷᛁᚠ᛫ᚻᛖ᛫ᚹᛁᛚᛖ᛫ᚠᚩᚱ᛫ᛞᚱᛁᚻᛏᚾᛖ᛫ᛞᚩᛗᛖᛋ᛫ᚻᛚᛇᛏᚪᚾ᛬`;

  // string length is only 117 characters but the byte length is 234.
  const secret = stringToBytes(secretUtf8);

  const splits = split(randomBytes, parts, quorum, secret);
  // only quorum parts are necessary
  delete parts[2];
  delete parts[3];
  t.equal(Object.keys(splits).length, parts);
  const joined = join(splits);
  t.equal(joined[200], secret[200]);
  t.equal(joined[201], secret[201]);
  const joinedUtf8 = bytesToSring(joined);
  t.equal(secretUtf8, joinedUtf8);
  t.end();
});

test('SchemeTests roundtrip two parts', function (t) {
  const parts = 3;
  const quorum = 2;

  const secretUtf8 = 'ᚠᛇᚻ';
  const secret = stringToBytes(secretUtf8);

  for (let i = 1; i <= 3; i++) {
    const splits = split(randomBytes, parts, quorum, secret);
    delete splits[`${i}`];
    const joinedUtf8 = bytesToSring(join(splits));
    t.equal(secretUtf8, joinedUtf8);
  }

  t.end();
});

test('SchemeTests split input validation', function (t) {
  const secretUtf8 = 'ᚠᛇᚻ';
  const secret = stringToBytes(secretUtf8);

  t.plan(3);

  try {
    split(randomBytes, 256, 2, secret);
    t.notOk(true);
  } catch (e) {
    t.ok(e.toString().includes('N must be <= 255'), e);
  }

  try {
    split(randomBytes, 3, 1, secret);
    t.notOk(true);
  } catch (e) {
    t.ok(e.toString().includes('K must be > 1'), e);
  }

  try {
    split(randomBytes, 2, 3, secret);
    t.notOk(true);
  } catch (e) {
    t.ok(e.toString().includes('N must be >= K'), e);
  }

  t.end();
});

test('SchemeTests join input validation', function (t) {
  try {
    join({});
    t.notOk(true);
  } catch (e) {
    t.ok(e.toString().includes('No parts provided'), e);
  }

  try {
    const splits = split(randomBytes, 3, 2, stringToBytes('ᚠᛇᚻ'));
    splits['2'] = Uint8Array.of(216, 30, 190, 102);
    join(splits);
    t.notOk(true);
  } catch (e) {
    t.ok(e.toString().includes('Varying lengths of part values'), e);
  }

  t.end();
});