tgseclib/phpseclib/Crypt/AES.php

<?php
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/**
 * Pure-PHP implementation of AES.
 *
 * Uses mcrypt, if available, and an internal implementation, otherwise.
 *
 * PHP versions 4 and 5
 *
 * If {@link Crypt_AES::setKeyLength() setKeyLength()} isn't called, it'll be calculated from
 * {@link Crypt_AES::setKey() setKey()}.  ie. if the key is 128-bits, the key length will be 128-bits.  If it's 136-bits
 * it'll be null-padded to 160-bits and 160 bits will be the key length until {@link Crypt_Rijndael::setKey() setKey()}
 * is called, again, at which point, it'll be recalculated.
 *
 * Since Crypt_AES extends Crypt_Rijndael, some functions are available to be called that, in the context of AES, don't
 * make a whole lot of sense.  {@link Crypt_AES::setBlockLength() setBlockLength()}, for instance.  Calling that function,
 * however possible, won't do anything (AES has a fixed block length whereas Rijndael has a variable one).
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include('Crypt/AES.php');
 *
 *    $aes = new Crypt_AES();
 *
 *    $aes->setKey('abcdefghijklmnop');
 *
 *    $size = 10 * 1024;
 *    $plaintext = '';
 *    for ($i = 0; $i < $size; $i++) {
 *        $plaintext.= 'a';
 *    }
 *
 *    echo $aes->decrypt($aes->encrypt($plaintext));
 * ?>
 * </code>
 *
 * LICENSE: Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @category   Crypt
 * @package    Crypt_AES
 * @author     Jim Wigginton <terrafrost@php.net>
 * @copyright  MMVIII Jim Wigginton
 * @license    http://www.opensource.org/licenses/mit-license.html  MIT License
 * @version    $Id: AES.php,v 1.7 2010/02/09 06:10:25 terrafrost Exp $
 * @link       http://phpseclib.sourceforge.net
 */

/**
 * Include Crypt_Rijndael
 */
if (!class_exists('Crypt_Rijndael')) {
    require_once 'Rijndael.php';
}

/**#@+
 * @access public
 * @see Crypt_AES::encrypt()
 * @see Crypt_AES::decrypt()
 */
/**
 * Encrypt / decrypt using the Counter mode.
 *
 * Set to -1 since that's what Crypt/Random.php uses to index the CTR mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Counter_.28CTR.29
 */
define('CRYPT_AES_MODE_CTR', CRYPT_MODE_CTR);
/**
 * Encrypt / decrypt using the Electronic Code Book mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29
 */
define('CRYPT_AES_MODE_ECB', CRYPT_MODE_ECB);
/**
 * Encrypt / decrypt using the Code Book Chaining mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher-block_chaining_.28CBC.29
 */
define('CRYPT_AES_MODE_CBC', CRYPT_MODE_CBC);
/**
 * Encrypt / decrypt using the Cipher Feedback mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher_feedback_.28CFB.29
 */
define('CRYPT_AES_MODE_CFB', CRYPT_MODE_CFB);
/**
 * Encrypt / decrypt using the Cipher Feedback mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Output_feedback_.28OFB.29
 */
define('CRYPT_AES_MODE_OFB', CRYPT_MODE_OFB);
/**#@-*/

/**#@+
 * @access private
 * @see Crypt_AES::Crypt_AES()
 */
/**
 * Toggles the internal implementation
 */
define('CRYPT_AES_MODE_INTERNAL', CRYPT_MODE_INTERNAL);
/**
 * Toggles the mcrypt implementation
 */
define('CRYPT_AES_MODE_MCRYPT', CRYPT_MODE_MCRYPT);
/**#@-*/

/**
 * Pure-PHP implementation of AES.
 *
 * @author  Jim Wigginton <terrafrost@php.net>
 * @version 0.1.0
 * @access  public
 * @package Crypt_AES
 */
class Crypt_AES extends Crypt_Rijndael {
    /**
     * The namespace used by the cipher for its constants.
     *
     * @see Crypt_Base::const_namespace
     * @var String
     * @access private
     */
    var $const_namespace = 'AES';

    /**
     * The mcrypt specific name of the cipher
     *
     * @see Crypt_Base::cipher_name_mcrypt
     * @var String
     * @access private
     */
    var $cipher_name_mcrypt = 'rijndael-128';

    /**
     * Default Constructor.
     *
     * Determines whether or not the mcrypt extension should be used.
     *
     * $mode could be:
     *
     * - CRYPT_AES_MODE_ECB
     *
     * - CRYPT_AES_MODE_CBC
     *
     * - CRYPT_AES_MODE_CTR
     *
     * - CRYPT_AES_MODE_CFB
     *
     * - CRYPT_AES_MODE_OFB
     *
     * If not explictly set, CRYPT_AES_MODE_CBC will be used.
     *
     * @see Crypt_Rijndael::Crypt_Rijndael()
     * @see Crypt_Base::Crypt_Base()
     * @param optional Integer $mode
     * @access public
     */
    function Crypt_AES($mode = CRYPT_AES_MODE_CBC)
    {
        parent::Crypt_Rijndael($mode);
    }

    /**
     * Dummy function
     *
     * Since Crypt_AES extends Crypt_Rijndael, this function is, technically, available, but it doesn't do anything.
     *
     * @see Crypt_Rijndael::setBlockLength()
     * @access public
     * @param Integer $length
     */
    function setBlockLength($length)
    {
        return;
    }

    /**
     * Sets the key length
     *
     * Valid key lengths are 128, 160, 192, 224, and 256.  If the length is less than 128, it will be rounded up to
     * 128.  If the length is greater than 128 and invalid, it will be rounded down to the closest valid amount.
     *
     * Note: phpseclib extends AES for using 160- and 224-bit keys but they are officially not defined in AES 
     *       and the most (if not all) implementations of AES are not able using 160/224-bit keys but round/pad 
     *       them up to 192/256 bits as, for example, mcrypt will do.
     *
     *       That said, if you want be compatible with other AES implementations, 
     *       you should not setKeyLength(160) or setKeyLength(224).
     *
     *       Additional: In case of 160- and 224-bit keys, phpseclib will/can, for that reason, not use
     *                   the mcrypt php extention, even if available. This results then in slower encryption.
     *
     * @access public
     * @param Integer $length
     */
    function setKeyLength($length)
    {
        parent::setKeyLength($length);

        switch ($this->key_size) {
            case 20: // 160-bits
            case 28: // 224-bits
                $this->engine = CRYPT_AES_MODE_INTERNAL; // because mcrypt is not able to use (real) 160/224-bit keys 
                break;                                   // we force using our internal AES engine instead of mcrypt.
            default:
                $this->engine = CRYPT_AES_MODE;
        }
    }

    /**
     * Setup the CRYPT_MODE_MCRYPT $engine
     *
     * Validates all the variables.
     *
     * @see Crypt_Base::_setupMcrypt()
     * @access private
     */
    function _setupMcrypt()
    {
        if (!$this->explicit_key_length) {
            $length = strlen($this->key);
            switch (true) {
                case $length <= 16:
                    $this->key_size = 16;
                    break;
                case $length <= 24:
                    $this->key_size = 24;
                    break;
                default:
                    $this->key_size = 32;
            }
        }

        $this->key = str_pad(substr($this->key, 0, $this->key_size), $this->key_size, "\0");
        parent::_setupMcrypt();
    }
}

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