<?php
/**
* PHP Class for handling Google Authenticator 2-factor authentication.
*
* @author Michael Kliewe
* @copyright 2012 Michael Kliewe
* @license http://www.opensource.org/licenses/bsd-license.php BSD License
*
* @link http://www.phpgangsta.de/
*/
class PHPGangsta_GoogleAuthenticator
{
protected $_codeLength = 6;
public function getCode($secret, $timeSlice = null)
{
if ($timeSlice === null) {
$timeSlice = floor(time() / 30);
}
$secretkey = $this->_base32Decode($secret);
$time = chr(0).chr(0).chr(0).chr(0).pack('N*', $timeSlice);
$hm = hash_hmac('SHA1', $time, $secretkey, true);
$offset = ord(substr($hm, -1)) & 0x0F;
$hashpart = substr($hm, $offset, 4);
$value = unpack('N', $hashpart);
$value = $value[1];
$value = $value & 0x7FFFFFFF;
$modulo = pow(10, $this->_codeLength);
return str_pad($value % $modulo, $this->_codeLength, '0', STR_PAD_LEFT);
}
protected function _base32Decode($secret)
{
if (empty($secret)) {
return '';
}
$base32chars = $this->_getBase32LookupTable();
$base32charsFlipped = array_flip($base32chars);
$paddingCharCount = substr_count($secret, $base32chars[32]);
$allowedValues = array(6, 4, 3, 1, 0);
if (!in_array($paddingCharCount, $allowedValues)) {
return false;
}
for ($i = 0; $i < 4; ++$i) {
if ($paddingCharCount == $allowedValues[$i] &&
substr($secret, -($allowedValues[$i])) != str_repeat($base32chars[32], $allowedValues[$i])) {
return false;
}
}
$secret = str_replace('=', '', $secret);
$secret = str_split($secret);
$binaryString = '';
for ($i = 0; $i < count($secret); $i = $i + 8) {
$x = '';
if (!in_array($secret[$i], $base32chars)) {
return false;
}
for ($j = 0; $j < 8; ++$j) {
$x .= str_pad(base_convert(@$base32charsFlipped[@$secret[$i + $j]], 10, 2), 5, '0', STR_PAD_LEFT);
}
$eightBits = str_split($x, 8);
for ($z = 0; $z < count($eightBits); ++$z) {
$binaryString .= (($y = chr(base_convert($eightBits[$z], 2, 10))) || ord($y) == 48) ? $y : '';
}
}
return $binaryString;
}
protected function _getBase32LookupTable()
{
return array(
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', // 7
'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', // 15
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', // 23
'Y', 'Z', '2', '3', '4', '5', '6', '7', // 31
'=', // padding char
);
}
}
?>