343 lines
8.6 KiB
PHP
343 lines
8.6 KiB
PHP
<?php
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/**
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* Pure-PHP implementation of RC4.
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*
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* Uses mcrypt, if available, and an internal implementation, otherwise.
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*
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* PHP version 5
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*
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* Useful resources are as follows:
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*
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* - {@link http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt ARCFOUR Algorithm}
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* - {@link http://en.wikipedia.org/wiki/RC4 - Wikipedia: RC4}
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*
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* RC4 is also known as ARCFOUR or ARC4. The reason is elaborated upon at Wikipedia. This class is named RC4 and not
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* ARCFOUR or ARC4 because RC4 is how it is referred to in the SSH1 specification.
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*
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* Here's a short example of how to use this library:
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* <code>
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* <?php
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* include 'vendor/autoload.php';
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*
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* $rc4 = new \phpseclib\Crypt\RC4();
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*
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* $rc4->setKey('abcdefgh');
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*
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* $size = 10 * 1024;
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* $plaintext = '';
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* for ($i = 0; $i < $size; $i++) {
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* $plaintext.= 'a';
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* }
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*
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* echo $rc4->decrypt($rc4->encrypt($plaintext));
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* ?>
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* </code>
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*
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* @category Crypt
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* @package RC4
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* @author Jim Wigginton <terrafrost@php.net>
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* @copyright 2007 Jim Wigginton
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* @license http://www.opensource.org/licenses/mit-license.html MIT License
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* @link http://phpseclib.sourceforge.net
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*/
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namespace phpseclib\Crypt;
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/**
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* Pure-PHP implementation of RC4.
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*
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* @package RC4
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* @author Jim Wigginton <terrafrost@php.net>
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* @access public
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*/
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class RC4 extends Base
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{
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/**#@+
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* @access private
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* @see \phpseclib\Crypt\RC4::_crypt()
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*/
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const ENCRYPT = 0;
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const DECRYPT = 1;
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/**#@-*/
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/**
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* Block Length of the cipher
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*
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* RC4 is a stream cipher
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* so we the block_size to 0
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*
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* @see \phpseclib\Crypt\Base::block_size
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* @var int
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* @access private
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*/
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var $block_size = 0;
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/**
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* Key Length (in bytes)
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*
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* @see \phpseclib\Crypt\RC4::setKeyLength()
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* @var int
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* @access private
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*/
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var $key_length = 128; // = 1024 bits
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/**
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* The mcrypt specific name of the cipher
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*
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* @see \phpseclib\Crypt\Base::cipher_name_mcrypt
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* @var string
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* @access private
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*/
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var $cipher_name_mcrypt = 'arcfour';
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/**
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* Holds whether performance-optimized $inline_crypt() can/should be used.
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*
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* @see \phpseclib\Crypt\Base::inline_crypt
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* @var mixed
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* @access private
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*/
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var $use_inline_crypt = false; // currently not available
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/**
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* The Key
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*
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* @see self::setKey()
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* @var string
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* @access private
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*/
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var $key = "\0";
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/**
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* The Key Stream for decryption and encryption
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*
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* @see self::setKey()
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* @var array
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* @access private
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*/
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var $stream;
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/**
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* Default Constructor.
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*
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* Determines whether or not the mcrypt extension should be used.
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*
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* @see \phpseclib\Crypt\Base::__construct()
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* @return \phpseclib\Crypt\RC4
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* @access public
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*/
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function __construct()
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{
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parent::__construct(Base::MODE_STREAM);
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}
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/**
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* Test for engine validity
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*
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* This is mainly just a wrapper to set things up for \phpseclib\Crypt\Base::isValidEngine()
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*
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* @see \phpseclib\Crypt\Base::__construct()
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* @param int $engine
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* @access public
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* @return bool
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*/
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function isValidEngine($engine)
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{
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if ($engine == Base::ENGINE_OPENSSL) {
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if (version_compare(PHP_VERSION, '5.3.7') >= 0) {
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$this->cipher_name_openssl = 'rc4-40';
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} else {
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switch (strlen($this->key)) {
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case 5:
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$this->cipher_name_openssl = 'rc4-40';
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break;
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case 8:
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$this->cipher_name_openssl = 'rc4-64';
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break;
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case 16:
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$this->cipher_name_openssl = 'rc4';
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break;
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default:
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return false;
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}
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}
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}
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return parent::isValidEngine($engine);
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}
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/**
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* Dummy function.
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*
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* Some protocols, such as WEP, prepend an "initialization vector" to the key, effectively creating a new key [1].
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* If you need to use an initialization vector in this manner, feel free to prepend it to the key, yourself, before
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* calling setKey().
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*
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* [1] WEP's initialization vectors (IV's) are used in a somewhat insecure way. Since, in that protocol,
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* the IV's are relatively easy to predict, an attack described by
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* {@link http://www.drizzle.com/~aboba/IEEE/rc4_ksaproc.pdf Scott Fluhrer, Itsik Mantin, and Adi Shamir}
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* can be used to quickly guess at the rest of the key. The following links elaborate:
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*
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* {@link http://www.rsa.com/rsalabs/node.asp?id=2009 http://www.rsa.com/rsalabs/node.asp?id=2009}
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* {@link http://en.wikipedia.org/wiki/Related_key_attack http://en.wikipedia.org/wiki/Related_key_attack}
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*
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* @param string $iv
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* @see self::setKey()
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* @access public
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*/
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function setIV($iv)
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{
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}
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/**
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* Sets the key length
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*
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* Keys can be between 1 and 256 bytes long.
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*
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* @access public
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* @param int $length
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*/
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function setKeyLength($length)
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{
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if ($length < 8) {
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$this->key_length = 1;
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} elseif ($length > 2048) {
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$this->key_length = 256;
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} else {
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$this->key_length = $length >> 3;
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}
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parent::setKeyLength($length);
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}
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/**
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* Encrypts a message.
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*
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* @see \phpseclib\Crypt\Base::decrypt()
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* @see self::_crypt()
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* @access public
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* @param string $plaintext
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* @return string $ciphertext
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*/
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function encrypt($plaintext)
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{
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if ($this->engine != Base::ENGINE_INTERNAL) {
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return parent::encrypt($plaintext);
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}
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return $this->_crypt($plaintext, self::ENCRYPT);
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}
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/**
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* Decrypts a message.
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*
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* $this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)).
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* At least if the continuous buffer is disabled.
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*
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* @see \phpseclib\Crypt\Base::encrypt()
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* @see self::_crypt()
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* @access public
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* @param string $ciphertext
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* @return string $plaintext
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*/
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function decrypt($ciphertext)
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{
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if ($this->engine != Base::ENGINE_INTERNAL) {
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return parent::decrypt($ciphertext);
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}
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return $this->_crypt($ciphertext, self::DECRYPT);
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}
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/**
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* Encrypts a block
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*
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* @access private
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* @param string $in
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*/
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function _encryptBlock($in)
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{
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// RC4 does not utilize this method
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}
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/**
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* Decrypts a block
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*
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* @access private
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* @param string $in
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*/
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function _decryptBlock($in)
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{
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// RC4 does not utilize this method
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}
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/**
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* Setup the key (expansion)
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*
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* @see \phpseclib\Crypt\Base::_setupKey()
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* @access private
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*/
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function _setupKey()
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{
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$key = $this->key;
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$keyLength = strlen($key);
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$keyStream = range(0, 255);
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$j = 0;
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for ($i = 0; $i < 256; $i++) {
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$j = ($j + $keyStream[$i] + ord($key[$i % $keyLength])) & 255;
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$temp = $keyStream[$i];
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$keyStream[$i] = $keyStream[$j];
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$keyStream[$j] = $temp;
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}
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$this->stream = array();
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$this->stream[self::DECRYPT] = $this->stream[self::ENCRYPT] = array(
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0, // index $i
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0, // index $j
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$keyStream
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);
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}
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/**
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* Encrypts or decrypts a message.
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*
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* @see self::encrypt()
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* @see self::decrypt()
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* @access private
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* @param string $text
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* @param int $mode
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* @return string $text
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*/
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function _crypt($text, $mode)
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{
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if ($this->changed) {
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$this->_setup();
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$this->changed = false;
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}
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$stream = &$this->stream[$mode];
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if ($this->continuousBuffer) {
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$i = &$stream[0];
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$j = &$stream[1];
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$keyStream = &$stream[2];
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} else {
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$i = $stream[0];
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$j = $stream[1];
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$keyStream = $stream[2];
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}
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$len = strlen($text);
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for ($k = 0; $k < $len; ++$k) {
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$i = ($i + 1) & 255;
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$ksi = $keyStream[$i];
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$j = ($j + $ksi) & 255;
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$ksj = $keyStream[$j];
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$keyStream[$i] = $ksj;
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$keyStream[$j] = $ksi;
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$text[$k] = $text[$k] ^ chr($keyStream[($ksj + $ksi) & 255]);
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}
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return $text;
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}
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}
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