tenvoy/openpgpjs/src/crypto/public_key/elliptic/eddsa.js

PGP, NaCl, and PBKDF2 in node.js and the browser (hashing, random, encryption, decryption, signatures, conversions), used by TogaTech.org

// OpenPGP.js - An OpenPGP implementation in javascript
// Copyright (C) 2018 Proton Technologies AG
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3.0 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

/**
 * @fileoverview Implementation of EdDSA following RFC4880bis-03 for OpenPGP
 * @requires hash.js
 * @requires tweetnacl
 * @requires crypto/public_key/elliptic/curve
 * @requires util
 * @module crypto/public_key/elliptic/eddsa
 */

import sha512 from 'hash.js/lib/hash/sha/512';
import nacl from 'tweetnacl/nacl-fast-light.js';
import util from '../../../util';

nacl.hash = bytes => new Uint8Array(sha512().update(bytes).digest());

/**
 * Sign a message using the provided key
 * @param  {module:type/oid}   oid          Elliptic curve object identifier
 * @param  {module:enums.hash} hash_algo    Hash algorithm used to sign
 * @param  {Uint8Array}        message      Message to sign
 * @param  {Uint8Array}        publicKey    Public key
 * @param  {Uint8Array}        privateKey   Private key used to sign the message
 * @param  {Uint8Array}        hashed       The hashed message
 * @returns {{R: Uint8Array,
 *            S: Uint8Array}}               Signature of the message
 * @async
 */
async function sign(oid, hash_algo, message, publicKey, privateKey, hashed) {
  const secretKey = util.concatUint8Array([privateKey, publicKey.subarray(1)]);
  const signature = nacl.sign.detached(hashed, secretKey);
  // EdDSA signature params are returned in little-endian format
  return {
    R: signature.subarray(0, 32),
    S: signature.subarray(32)
  };
}

/**
 * Verifies if a signature is valid for a message
 * @param  {module:type/oid}   oid       Elliptic curve object identifier
 * @param  {module:enums.hash} hash_algo Hash algorithm used in the signature
 * @param  {{R: Uint8Array,
             S: Uint8Array}}   signature Signature to verify the message
 * @param  {Uint8Array}        m         Message to verify
 * @param  {Uint8Array}        publicKey Public key used to verify the message
 * @param  {Uint8Array}        hashed    The hashed message
 * @returns {Boolean}
 * @async
 */
async function verify(oid, hash_algo, { R, S }, m, publicKey, hashed) {
  const signature = util.concatUint8Array([R, S]);
  return nacl.sign.detached.verify(hashed, signature, publicKey.subarray(1));
}

/**
 * Validate EdDSA parameters
 * @param {module:type/oid}    oid Elliptic curve object identifier
 * @param {Uint8Array}         Q   EdDSA public point
 * @param {Uint8Array}         k   EdDSA secret seed
 * @returns {Promise<Boolean>} whether params are valid
 * @async
 */
async function validateParams(oid, Q, k) {
  // Check whether the given curve is supported
  if (oid.getName() !== 'ed25519') {
    return false;
  }

  /**
   * Derive public point Q' = dG from private key
   * and expect Q == Q'
   */
  const { publicKey } = nacl.sign.keyPair.fromSeed(k);
  const dG = new Uint8Array([0x40, ...publicKey]); // Add public key prefix
  return util.equalsUint8Array(Q, dG);
}

/**
 * Parses MPI params and returns them as byte arrays of fixed length
 * @param {Array} params key parameters
 * @returns {Object} parameters in the form
 *  { oid, seed: Uint8Array, Q: Uint8Array }
 */
function parseParams(params) {
  if (params.length < 2 || params.length > 3) {
    throw new Error('Unexpected number of parameters');
  }

  const parsedParams = {
    oid: params[0],
    Q: params[1].toUint8Array('be', 33)
  };

  if (params.length === 3) {
    parsedParams.seed = params[2].toUint8Array('be', 32);
  }

  return parsedParams;
}


export default { sign, verify, validateParams, parseParams };