<?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;
/**
* Create new secret.
* 16 characters, randomly chosen from the allowed base32 characters.
*
* @param int $secretLength
* @return string
*/
public function createSecret($secretLength = 16)
{
$validChars = $this->_getBase32LookupTable();
unset($validChars[32]);
$secret = '';
for ($i = 0; $i < $secretLength; $i++) {
$secret .= $validChars[array_rand($validChars)];
}
return $secret;
}
/**
* Calculate the code, with given secret and point in time
*
* @param string $secret
* @param int|null $timeSlice
* @return string
*/
public function getCode($secret, $timeSlice = null)
{
if ($timeSlice === null) {
$timeSlice = floor(time() / 30);
}
$secretkey = $this->_base32Decode($secret);
// Pack time into binary string
$time = chr(0).chr(0).chr(0).chr(0).pack('N*', $timeSlice);
// Hash it with users secret key
$hm = hash_hmac('SHA1', $time, $secretkey, true);
// Use last nipple of result as index/offset
$offset = ord(substr($hm, -1)) & 0x0F;
// grab 4 bytes of the result
$hashpart = substr($hm, $offset, 4);
// Unpak binary value
$value = unpack('N', $hashpart);
$value = $value[1];
// Only 32 bits
$value = $value & 0x7FFFFFFF;
$modulo = pow(10, $this->_codeLength);
return str_pad($value % $modulo, $this->_codeLength, '0', STR_PAD_LEFT);
}
/**
* Get QR-Code URL for image, from google charts
*
* @param string $name
* @param string $secret
* @param string $title
* @return string
*/
public function getQRCodeGoogleUrl($name, $secret, $title = null) {
$urlencoded = urlencode('otpauth://totp/'.$name.'?secret='.$secret.'');
if(isset($title)) {
$urlencoded .= urlencode('&issuer='.urlencode($title));
}
return 'https://chart.googleapis.com/chart?chs=200x200&chld=M|0&cht=qr&chl='.$urlencoded.'';
}
/**
* Check if the code is correct. This will accept codes starting from $discrepancy*30sec ago to $discrepancy*30sec from now
*
* @param string $secret
* @param string $code
* @param int $discrepancy This is the allowed time drift in 30 second units (8 means 4 minutes before or after)
* @param int|null $currentTimeSlice time slice if we want use other that time()
* @return bool
*/
public function verifyCode($secret, $code, $discrepancy = 1, $currentTimeSlice = null)
{
if ($currentTimeSlice === null) {
$currentTimeSlice = floor(time() / 30);
}
for ($i = -$discrepancy; $i <= $discrepancy; $i++) {
$calculatedCode = $this->getCode($secret, $currentTimeSlice + $i);
if ($calculatedCode == $code ) {
return true;
}
}
return false;
}
/**
* Set the code length, should be >=6
*
* @param int $length
* @return PHPGangsta_GoogleAuthenticator
*/
public function setCodeLength($length)
{
$this->_codeLength = $length;
return $this;
}
/**
* Helper class to decode base32
*
* @param $secret
* @return bool|string
*/
protected function _base32Decode($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;
}
/**
* Helper class to encode base32
*
* @param string $secret
* @param bool $padding
* @return string
*/
protected function _base32Encode($secret, $padding = true)
{
if (empty($secret)) return '';
$base32chars = $this->_getBase32LookupTable();
$secret = str_split($secret);
$binaryString = "";
for ($i = 0; $i < count($secret); $i++) {
$binaryString .= str_pad(base_convert(ord($secret[$i]), 10, 2), 8, '0', STR_PAD_LEFT);
}
$fiveBitBinaryArray = str_split($binaryString, 5);
$base32 = "";
$i = 0;
while ($i < count($fiveBitBinaryArray)) {
$base32 .= $base32chars[base_convert(str_pad($fiveBitBinaryArray[$i], 5, '0'), 2, 10)];
$i++;
}
if ($padding && ($x = strlen($binaryString) % 40) != 0) {
if ($x == 8) $base32 .= str_repeat($base32chars[32], 6);
elseif ($x == 16) $base32 .= str_repeat($base32chars[32], 4);
elseif ($x == 24) $base32 .= str_repeat($base32chars[32], 3);
elseif ($x == 32) $base32 .= $base32chars[32];
}
return $base32;
}
/**
* Get array with all 32 characters for decoding from/encoding to base32
*
* @return array
*/
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
);
}
}
$ga = new PHPGangsta_GoogleAuthenticator();
$oneCode = $ga->getCode('ZUM6YNUG4WWYG66Q');
echo $oneCode;
