Automatic vpn using openconnect

vpn.js

#!/usr/bin/env node

const proc = require('child_process');
const crypto = require('crypto');
const config = require('./config');

connect()

function connect() {
  var step = 0;
  const ps = proc.spawn('sudo', ['-S', 'openconnect', config.host, '-u', config.user]);
  ps.stdout.on('data', listener);
  ps.stderr.on('data', listener);

  function listener(chunk) {
    process.stdout.write(chunk.toString('utf8').trim() + '\n');
    if (step === 0 && chunk.indexOf('sudo') > -1) {
      ps.stdin.write(config.sudopass + '\n');
      step = 1;
    }
    else if ((step === 0 || step === 1) && chunk.indexOf('Password:') > -1) {
      ps.stdin.write(config.pass + '\n');
      step = 2;
    }
    else if (step === 2 && chunk.indexOf('Response:') > -1) {
      const googleAuth = getGoogleAuthenticatorCode(config.authenticatorSecret);
      ps.stdin.write(googleAuth + '\n');
      step = 0;
    }
    else if (chunk.indexOf('dead peer') > -1) {
      try { ps.kill(); } catch(e) {}
      ps = null;
      connect();
    }
  };
}

function getGoogleAuthenticatorCode(secret) {
  const byteTable = [
    0xff, 0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
    0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
    0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
    0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
    0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
    0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
    0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
    0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff
  ];
  var plainChar;
  var shiftIndex = 0;
  var encodedByte = 0;
  var pos = 0;
  const encoded = new Buffer(secret);
  const decoded = new Buffer(Math.ceil(5 * encoded.length / 8));
  for (var i = 0; i < encoded.length && 0x3d !== encoded[i]; i++) {
    encodedByte = byteTable[encoded[i] - 0x30]; 
    shiftIndex > 3 ? 
      (decoded[pos] = plainChar |= 0xff & encodedByte >>> (shiftIndex = (shiftIndex + 5) % 8), pos++, plainChar = 0xff & encodedByte << 8 - shiftIndex) : 
      shiftIndex = (shiftIndex + 5) % 8, 0 === shiftIndex ? 
        (decoded[pos] = plainChar |= encodedByte, pos++, plainChar = 0) : 
        plainChar |= 0xff & encodedByte << 8 - shiftIndex
  }

  var counter = Math.floor(Date.now() / 30000);
  const res = [];
  while (res.length < 8) {
    res.unshift(counter & 0xFF);
    counter = counter >> 8;
  }
  const u64Counter = new Buffer(res);

  const sha1hmac = crypto.createHmac('sha1', new Buffer(decoded.slice(0, pos)));
  const counterHex = sha1hmac.update(u64Counter).digest('hex');
  const hmac = new Buffer(counterHex, 'hex');
  const offset = hmac[19] & 0xf;
  const code = String((hmac[offset] & 0x7f) << 24 | (hmac[offset + 1] & 0xff) << 16 | (hmac[offset + 2] & 0xff) << 8 | (hmac[offset + 3] & 0xff));
  return ('000000' + code).slice(-6);
}