1 <?php

     2 

     3 /**

     4  * Returns OTP data. Numeric except for public and private IDs, which are hex.

     5  * @return array Associative

     6  */

     7 

     8 function yms_decode_otp($otp, $key)

     9 {

    10   static $aes = false;

    11   if ( !is_object($aes) )

    12     $aes = AESCrypt::singleton(128, 128);

    13   

    14   $return = array();

    15   

    16   $otp = yms_tobinary($otp);

    17   if ( strlen($otp) != 22 )

    18   {

    19     return false;

    20   }

    21   $key = yms_tobinary($key);

    22   if ( strlen($key) != 16 )

    23   {

    24     return false;

    25   }

    26   

    27   $cryptpart = yms_hex_encode(substr($otp, 6, 16));

    28   $publicid = substr($otp, 0, 6);

    29   

    30   $return['publicid'] = yms_hex_encode($publicid);

    31   $otp_decrypted = $aes->decrypt($cryptpart, $key, ENC_HEX);

    32   $crc_is_good = yms_validate_crc($otp_decrypted);

    33   $return['privateid'] = yms_hex_encode(substr($otp_decrypted, 0, 6));

    34   $return['session'] = yms_unpack_int(strrev(substr($otp_decrypted, 6, 2)));

    35   $return['timestamp'] = yms_unpack_int(strrev(substr($otp_decrypted, 8, 3)));

    36   $return['count'] = yms_unpack_int(substr($otp_decrypted, 11, 1));

    37   $return['random'] = yms_unpack_int(substr($otp_decrypted, 12, 2));

    38   $return['crc'] = yms_unpack_int(substr($otp_decrypted, 14, 2));

    39   $return['crc_good'] = $crc_is_good;

    40   

    41   return $return;

    42 }

    43 

    44 function yms_unpack_int($str)

    45 {

    46   $return = 0;

    47   for ( $i = 0; $i < strlen($str); $i++ )

    48   {

    49     $return = $return << 8;

    50     $return = $return | ord($str{$i});

    51   }

    52   return $return;

    53 }

    54 

    55 function yms_crc16($buffer)

    56 {

    57   $buffer = yms_tobinary($buffer);

    58   

    59   $m_crc=0x5af0;

    60   for($bpos=0; $bpos<strlen($buffer); $bpos++)

    61   {

    62     $m_crc ^= ord($buffer[$bpos]);

    63     for ($i=0; $i<8; $i++)

    64     {

    65       $j=$m_crc & 1;

    66       $m_crc >>= 1;

    67       if ($j) $m_crc ^= 0x8408;

    68     }

    69   }

    70   return $m_crc;

    71 }

    72 

    73 function yms_validate_crc($token)

    74 {

    75   $crc = yms_crc16($token);

    76   return $crc == 0;

    77 }

    78 

    79 function yms_within($test, $control, $fuzz)

    80 {

    81   $min = $control - $fuzz;

    82   $max = $control + $fuzz;

    83   return $test > $min && $test < $max;

    84 }