<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_InfoCard
 * @subpackage Zend_InfoCard_Cipher
 * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: Aes256cbc.php 9094 2008-03-30 18:36:55Z thomas $
 */

/**
 * Zend_InfoCard_Cipher_Symmetric_Adapter_Abstract
 */
require_once 'Zend/InfoCard/Cipher/Symmetric/Adapter/Abstract.php';

/**
 * Zend_InfoCard_Cipher_Symmetric_Aes256cbc_Interface
 */
require_once 'Zend/InfoCard/Cipher/Symmetric/Aes256cbc/Interface.php';

/**
 * Zend_InfoCard_Cipher_Exception
 */
require_once 'Zend/InfoCard/Cipher/Exception.php';

/**
 * Implements AES256 with CBC encryption implemented using the mCrypt extension
 *
 * @category   Zend
 * @package    Zend_InfoCard
 * @subpackage Zend_InfoCard_Cipher
 * @copyright  Copyright (c) 2005-2008 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_InfoCard_Cipher_Symmetric_Adapter_Aes256cbc
    extends Zend_InfoCard_Cipher_Symmetric_Adapter_Abstract
    implements Zend_InfoCard_Cipher_Symmetric_Aes256cbc_Interface
{
    /**
     * The MCRYPT Cipher constant for this encryption
     */
    const MCRYPT_CIPHER = MCRYPT_RIJNDAEL_128;

    /**
     * The MCRYPT Mode constant for this encryption
     */
    const MCRYPT_MODE   = MCRYPT_MODE_CBC;

    /**
     * The default length of the IV to use
     */
    const IV_LENGTH     = 16;

    /**
     * The object constructor
     *
     * @throws Zend_InfoCard_Cipher_Exception
     */
    public function __construct()
    {
        // Can't test for this
        // @codeCoverageIgnoreStart
        if(!extension_loaded('mcrypt')) {
            throw new Zend_InfoCard_Cipher_Exception("Use of the AES256CBC Cipher requires the mcrypt extension");
        }
        // @codeCoveregIgnoreEnd
    }

    /**
     * Decrypts data using the AES Algorithm using the mCrypt extension
     *
     * @throws Zend_InfoCard_Cipher_Exception
     * @param string $encryptedData The encrypted data in binary format
     * @param string $decryptionKey The decryption key
     * @param integer $iv_length The IV length to use
     * @return string the decrypted data with any terminating nulls removed
     */
    public function decrypt($encryptedData, $decryptionKey, $iv_length = null)
    {

        $iv_length = is_null($iv_length) ? self::IV_LENGTH : $iv_length;

        $mcrypt_iv = null;

        if($iv_length > 0) {
             $mcrypt_iv = substr($encryptedData, 0, $iv_length);
            $encryptedData = substr($encryptedData, $iv_length);
        }

        $decrypted = mcrypt_decrypt(self::MCRYPT_CIPHER, $decryptionKey, $encryptedData, self::MCRYPT_MODE, $mcrypt_iv);

        if(!$decrypted) {
            throw new Zend_InfoCard_Cipher_Exception("Failed to decrypt data using AES256CBC Algorithm");
        }

        $decryptedLength = strlen($decrypted);
        $paddingLength = substr($decrypted, $decryptedLength -1, 1);
        $decrypted = substr($decrypted, 0, $decryptedLength - ord($paddingLength));

        return rtrim($decrypted, "\0");
    }
}