ethereum-web-token/dist/util/signature.js

EWT bundles Ethereum function-calls into [JWT](https://jwt.io/)-like tokens. It simplifies the use of ECDSA signatures for webapps and the development of [Smart Oracles](https://github.com/codius/codius/wiki/Smart-Oracles:-A-Simple,-Powerful-Approach-to-S

'use strict';


var _jsSha = require('js-sha3');
var _format = require('../spec/paramType/format');var BN = require('bn.js'); // eslint-disable-line camelcase

var elliptic = require('elliptic');
var utils = elliptic.utils;
var assert = utils.assert;

function Signature(options, enc) {
  if (options instanceof Signature)
  return options;

  if (this._importDER(options, enc))
  return;

  assert(options.r && options.s, 'Signature without r or s');
  this.r = new BN(options.r, 16);
  this.s = new BN(options.s, 16);
  if (options.recoveryParam === undefined)
  this.recoveryParam = null;else

  this.recoveryParam = options.recoveryParam;
}
module.exports = Signature;

function Position() {
  this.place = 0;
}

function getLength(buf, p) {
  var initial = buf[p.place++];
  if (!(initial & 0x80)) {
    return initial;
  }
  var octetLen = initial & 0xf;
  var val = 0;
  for (var i = 0, off = p.place; i < octetLen; i++, off++) {
    val <<= 8;
    val |= buf[off];
  }
  p.place = off;
  return val;
}

function rmPadding(buf) {
  var i = 0;
  var len = buf.length - 1;
  while (!buf[i] && !(buf[i + 1] & 0x80) && i < len) {
    i++;
  }
  if (i === 0) {
    return buf;
  }
  return buf.slice(i);
}

Signature.prototype._importDER = function _importDER(data, enc) {
  data = utils.toArray(data, enc);
  var p = new Position();
  if (data[p.place++] !== 0x30) {
    return false;
  }
  var len = getLength(data, p);
  if (len + p.place !== data.length) {
    return false;
  }
  if (data[p.place++] !== 0x02) {
    return false;
  }
  var rlen = getLength(data, p);
  var r = data.slice(p.place, rlen + p.place);
  p.place += rlen;
  if (data[p.place++] !== 0x02) {
    return false;
  }
  var slen = getLength(data, p);
  if (data.length !== slen + p.place) {
    return false;
  }
  var s = data.slice(p.place, slen + p.place);
  if (r[0] === 0 && r[1] & 0x80) {
    r = r.slice(1);
  }
  if (s[0] === 0 && s[1] & 0x80) {
    s = s.slice(1);
  }

  this.r = new BN(r);
  this.s = new BN(s);
  this.recoveryParam = null;

  return true;
};

function constructLength(arr, len) {
  if (len < 0x80) {
    arr.push(len);
    return;
  }
  var octets = 1 + (Math.log(len) / Math.LN2 >>> 3);
  arr.push(octets | 0x80);
  while (--octets) {
    arr.push(len >>> (octets << 3) & 0xff);
  }
  arr.push(len);
}

Signature.prototype.toDER = function toDER(enc) {
  var r = this.r.toArray();
  var s = this.s.toArray();

  // Pad values
  if (r[0] & 0x80)
  r = [0].concat(r);
  // Pad values
  if (s[0] & 0x80)
  s = [0].concat(s);

  r = rmPadding(r);
  s = rmPadding(s);

  while (!s[0] && !(s[1] & 0x80)) {
    s = s.slice(1);
  }
  var arr = [0x02];
  constructLength(arr, r.length);
  arr = arr.concat(r);
  arr.push(0x02);
  constructLength(arr, s.length);
  var backHalf = arr.concat(s);
  var res = [0x30];
  constructLength(res, backHalf.length);
  res = res.concat(backHalf);
  return utils.encode(res, enc);
};