CryptLib/Encryption/PackingMode/PKCS7.php

   1 <?php
   2 /**
   3  * A packing mode implementation for PKCS7 padding
   4  *
   5  * PHP version 5.3
   6  *
   7  * @see        http://tools.ietf.org/html/rfc2315
   8  * @category   PHPCryptLib
   9  * @package    Encryption
  10  * @subpackage PackingMode
  11  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  12  * @copyright  2011 The Authors
  13  * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
  14  * @version    Build @@version@@
  15  */
  16
  17 namespace CryptLib\Encryption\PackingMode;
  18
  19 /**
  20  * A packing mode implementation for PKCS7 padding
  21  *
  22  * PHP version 5.3
  23  *
  24  * @see        http://tools.ietf.org/html/rfc2315
  25  * @category   PHPCryptLib
  26  * @package    Encryption
  27  * @subpackage PackingMode
  28  * @author     Anthony Ferrara <ircmaxell@ircmaxell.com>
  29  */
  30 class PKCS7 implements \CryptLib\Encryption\PackingMode {
  31
  32     /**
  33      * Pad the string to the specified size
  34      *
  35      * @param string $string    The string to pad
  36      * @param int    $blockSize The size to pad to
  37      *
  38      * @return string The padded string
  39      */
  40     public function pad($string, $blockSize = 32) {
  41         $pad = $blockSize - (strlen($string) % $blockSize);
  42         return $string . str_repeat(chr($pad), $pad);
  43     }
  44
  45     /**
  46      * Strip the padding from the supplied string
  47      *
  48      * @param string $string The string to trim
  49      *
  50      * @return string The unpadded string
  51      */
  52     public function strip($string) {
  53         $end  = substr($string, -1);
  54         $last = ord($end);
  55         $len  = strlen($string) - $last;
  56         if (substr($string, $len) == str_repeat($end, $last)) {
  57             return substr($string, 0, $len);
  58         }
  59         return false;
  60     }
  61
  62 }