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+<?php
+/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */
+
+/**
+ * Pure-PHP implementation of RC4.
+ *
+ * Uses mcrypt, if available, and an internal implementation, otherwise.
+ *
+ * PHP versions 4 and 5
+ *
+ * Useful resources are as follows:
+ *
+ * - {@link http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt ARCFOUR Algorithm}
+ * - {@link http://en.wikipedia.org/wiki/RC4 - Wikipedia: RC4}
+ *
+ * RC4 is also known as ARCFOUR or ARC4. The reason is elaborated upon at Wikipedia. This class is named RC4 and not
+ * ARCFOUR or ARC4 because RC4 is how it is refered to in the SSH1 specification.
+ *
+ * Here's a short example of how to use this library:
+ * <code>
+ * <?php
+ * include('Crypt/RC4.php');
+ *
+ * $rc4 = new Crypt_RC4();
+ *
+ * $rc4->setKey('abcdefgh');
+ *
+ * $size = 10 * 1024;
+ * $plaintext = '';
+ * for ($i = 0; $i < $size; $i++) {
+ * $plaintext.= 'a';
+ * }
+ *
+ * echo $rc4->decrypt($rc4->encrypt($plaintext));
+ * ?>
+ * </code>
+ *
+ * LICENSE: This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ *
+ * @category Crypt
+ * @package Crypt_RC4
+ * @author Jim Wigginton <terrafrost@php.net>
+ * @copyright MMVII Jim Wigginton
+ * @license http://www.gnu.org/licenses/lgpl.txt
+ * @version $Id: RC4.php,v 1.8 2009/06/09 04:00:38 terrafrost Exp $
+ * @link http://phpseclib.sourceforge.net
+ */
+
+/**#@+
+ * @access private
+ * @see Crypt_RC4::Crypt_RC4()
+ */
+/**
+ * Toggles the internal implementation
+ */
+define('CRYPT_RC4_MODE_INTERNAL', 1);
+/**
+ * Toggles the mcrypt implementation
+ */
+define('CRYPT_RC4_MODE_MCRYPT', 2);
+/**#@-*/
+
+/**#@+
+ * @access private
+ * @see Crypt_RC4::_crypt()
+ */
+define('CRYPT_RC4_ENCRYPT', 0);
+define('CRYPT_RC4_DECRYPT', 1);
+/**#@-*/
+
+/**
+ * Pure-PHP implementation of RC4.
+ *
+ * @author Jim Wigginton <terrafrost@php.net>
+ * @version 0.1.0
+ * @access public
+ * @package Crypt_RC4
+ */
+class Crypt_RC4 {
+ /**
+ * The Key
+ *
+ * @see Crypt_RC4::setKey()
+ * @var String
+ * @access private
+ */
+ var $key = "\0";
+
+ /**
+ * The Key Stream for encryption
+ *
+ * If CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT, this will be equal to the mcrypt object
+ *
+ * @see Crypt_RC4::setKey()
+ * @var Array
+ * @access private
+ */
+ var $encryptStream = false;
+
+ /**
+ * The Key Stream for decryption
+ *
+ * If CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT, this will be equal to the mcrypt object
+ *
+ * @see Crypt_RC4::setKey()
+ * @var Array
+ * @access private
+ */
+ var $decryptStream = false;
+
+ /**
+ * The $i and $j indexes for encryption
+ *
+ * @see Crypt_RC4::_crypt()
+ * @var Integer
+ * @access private
+ */
+ var $encryptIndex = 0;
+
+ /**
+ * The $i and $j indexes for decryption
+ *
+ * @see Crypt_RC4::_crypt()
+ * @var Integer
+ * @access private
+ */
+ var $decryptIndex = 0;
+
+ /**
+ * MCrypt parameters
+ *
+ * @see Crypt_RC4::setMCrypt()
+ * @var Array
+ * @access private
+ */
+ var $mcrypt = array('', '');
+
+ /**
+ * The Encryption Algorithm
+ *
+ * Only used if CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT. Only possible values are MCRYPT_RC4 or MCRYPT_ARCFOUR.
+ *
+ * @see Crypt_RC4::Crypt_RC4()
+ * @var Integer
+ * @access private
+ */
+ var $mode;
+
+ /**
+ * Default Constructor.
+ *
+ * Determines whether or not the mcrypt extension should be used.
+ *
+ * @param optional Integer $mode
+ * @return Crypt_RC4
+ * @access public
+ */
+ function Crypt_RC4()
+ {
+ if ( !defined('CRYPT_RC4_MODE') ) {
+ switch (true) {
+ case extension_loaded('mcrypt') && (defined('MCRYPT_ARCFOUR') || defined('MCRYPT_RC4')):
+ // i'd check to see if rc4 was supported, by doing in_array('arcfour', mcrypt_list_algorithms('')),
+ // but since that can be changed after the object has been created, there doesn't seem to be
+ // a lot of point...
+ define('CRYPT_RC4_MODE', CRYPT_RC4_MODE_MCRYPT);
+ break;
+ default:
+ define('CRYPT_RC4_MODE', CRYPT_RC4_MODE_INTERNAL);
+ }
+ }
+
+ switch ( CRYPT_RC4_MODE ) {
+ case CRYPT_RC4_MODE_MCRYPT:
+ switch (true) {
+ case defined('MCRYPT_ARCFOUR'):
+ $this->mode = MCRYPT_ARCFOUR;
+ break;
+ case defined('MCRYPT_RC4');
+ $this->mode = MCRYPT_RC4;
+ }
+ }
+ }
+
+ /**
+ * Sets the key.
+ *
+ * Keys can be between 1 and 256 bytes long. If they are longer then 256 bytes, the first 256 bytes will
+ * be used. If no key is explicitly set, it'll be assumed to be a single null byte.
+ *
+ * @access public
+ * @param String $key
+ */
+ function setKey($key)
+ {
+ $this->key = $key;
+
+ if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
+ return;
+ }
+
+ $keyLength = strlen($key);
+ $keyStream = array();
+ for ($i = 0; $i < 256; $i++) {
+ $keyStream[$i] = $i;
+ }
+ $j = 0;
+ for ($i = 0; $i < 256; $i++) {
+ $j = ($j + $keyStream[$i] + ord($key[$i % $keyLength])) & 255;
+ $temp = $keyStream[$i];
+ $keyStream[$i] = $keyStream[$j];
+ $keyStream[$j] = $temp;
+ }
+
+ $this->encryptIndex = $this->decryptIndex = array(0, 0);
+ $this->encryptStream = $this->decryptStream = $keyStream;
+ }
+
+ /**
+ * Dummy function.
+ *
+ * Some protocols, such as WEP, prepend an "initialization vector" to the key, effectively creating a new key [1].
+ * If you need to use an initialization vector in this manner, feel free to prepend it to the key, yourself, before
+ * calling setKey().
+ *
+ * [1] WEP's initialization vectors (IV's) are used in a somewhat insecure way. Since, in that protocol,
+ * the IV's are relatively easy to predict, an attack described by
+ * {@link http://www.drizzle.com/~aboba/IEEE/rc4_ksaproc.pdf Scott Fluhrer, Itsik Mantin, and Adi Shamir}
+ * can be used to quickly guess at the rest of the key. The following links elaborate:
+ *
+ * {@link http://www.rsa.com/rsalabs/node.asp?id=2009 http://www.rsa.com/rsalabs/node.asp?id=2009}
+ * {@link http://en.wikipedia.org/wiki/Related_key_attack http://en.wikipedia.org/wiki/Related_key_attack}
+ *
+ * @param String $iv
+ * @see Crypt_RC4::setKey()
+ * @access public
+ */
+ function setIV($iv)
+ {
+ }
+
+ /**
+ * Sets MCrypt parameters. (optional)
+ *
+ * If MCrypt is being used, empty strings will be used, unless otherwise specified.
+ *
+ * @link http://php.net/function.mcrypt-module-open#function.mcrypt-module-open
+ * @access public
+ * @param optional Integer $algorithm_directory
+ * @param optional Integer $mode_directory
+ */
+ function setMCrypt($algorithm_directory = '', $mode_directory = '')
+ {
+ if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
+ $this->mcrypt = array($algorithm_directory, $mode_directory);
+ $this->_closeMCrypt();
+ }
+ }
+
+ /**
+ * Encrypts a message.
+ *
+ * @see Crypt_RC4::_crypt()
+ * @access public
+ * @param String $plaintext
+ */
+ function encrypt($plaintext)
+ {
+ return $this->_crypt($plaintext, CRYPT_RC4_ENCRYPT);
+ }
+
+ /**
+ * Decrypts a message.
+ *
+ * $this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)).
+ * Atleast if the continuous buffer is disabled.
+ *
+ * @see Crypt_RC4::_crypt()
+ * @access public
+ * @param String $ciphertext
+ */
+ function decrypt($ciphertext)
+ {
+ return $this->_crypt($ciphertext, CRYPT_RC4_DECRYPT);
+ }
+
+ /**
+ * Encrypts or decrypts a message.
+ *
+ * @see Crypt_RC4::encrypt()
+ * @see Crypt_RC4::decrypt()
+ * @access private
+ * @param String $text
+ * @param Integer $mode
+ */
+ function _crypt($text, $mode)
+ {
+ if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
+ $keyStream = $mode == CRYPT_RC4_ENCRYPT ? 'encryptStream' : 'decryptStream';
+
+ if ($this->$keyStream === false) {
+ $this->$keyStream = mcrypt_module_open($this->mode, $this->mcrypt[0], MCRYPT_MODE_STREAM, $this->mcrypt[1]);
+ mcrypt_generic_init($this->$keyStream, $this->key, '');
+ } else if (!$this->continuousBuffer) {
+ mcrypt_generic_init($this->$keyStream, $this->key, '');
+ }
+ $newText = mcrypt_generic($this->$keyStream, $text);
+ if (!$this->continuousBuffer) {
+ mcrypt_generic_deinit($this->$keyStream);
+ }
+
+ return $newText;
+ }
+
+ if ($this->encryptStream === false) {
+ $this->setKey($this->key);
+ }
+
+ switch ($mode) {
+ case CRYPT_RC4_ENCRYPT:
+ $keyStream = $this->encryptStream;
+ list($i, $j) = $this->encryptIndex;
+ break;
+ case CRYPT_RC4_DECRYPT:
+ $keyStream = $this->decryptStream;
+ list($i, $j) = $this->decryptIndex;
+ }
+
+ $newText = '';
+ for ($k = 0; $k < strlen($text); $k++) {
+ $i = ($i + 1) & 255;
+ $j = ($j + $keyStream[$i]) & 255;
+ $temp = $keyStream[$i];
+ $keyStream[$i] = $keyStream[$j];
+ $keyStream[$j] = $temp;
+ $temp = $keyStream[($keyStream[$i] + $keyStream[$j]) & 255];
+ $newText.= chr(ord($text[$k]) ^ $temp);
+ }
+
+ if ($this->continuousBuffer) {
+ switch ($mode) {
+ case CRYPT_RC4_ENCRYPT:
+ $this->encryptStream = $keyStream;
+ $this->encryptIndex = array($i, $j);
+ break;
+ case CRYPT_RC4_DECRYPT:
+ $this->decryptStream = $keyStream;
+ $this->decryptIndex = array($i, $j);
+ }
+ }
+
+ return $newText;
+ }
+
+ /**
+ * Treat consecutive "packets" as if they are a continuous buffer.
+ *
+ * Say you have a 16-byte plaintext $plaintext. Using the default behavior, the two following code snippets
+ * will yield different outputs:
+ *
+ * <code>
+ * echo $rc4->encrypt(substr($plaintext, 0, 8));
+ * echo $rc4->encrypt(substr($plaintext, 8, 8));
+ * </code>
+ * <code>
+ * echo $rc4->encrypt($plaintext);
+ * </code>
+ *
+ * The solution is to enable the continuous buffer. Although this will resolve the above discrepancy, it creates
+ * another, as demonstrated with the following:
+ *
+ * <code>
+ * $rc4->encrypt(substr($plaintext, 0, 8));
+ * echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
+ * </code>
+ * <code>
+ * echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
+ * </code>
+ *
+ * With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different
+ * outputs. The reason is due to the fact that the initialization vector's change after every encryption /
+ * decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
+ *
+ * Put another way, when the continuous buffer is enabled, the state of the Crypt_DES() object changes after each
+ * encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that
+ * continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them),
+ * however, they are also less intuitive and more likely to cause you problems.
+ *
+ * @see Crypt_RC4::disableContinuousBuffer()
+ * @access public
+ */
+ function enableContinuousBuffer()
+ {
+ $this->continuousBuffer = true;
+ }
+
+ /**
+ * Treat consecutive packets as if they are a discontinuous buffer.
+ *
+ * The default behavior.
+ *
+ * @see Crypt_RC4::enableContinuousBuffer()
+ * @access public
+ */
+ function disableContinuousBuffer()
+ {
+ if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_INTERNAL ) {
+ $this->encryptIndex = $this->decryptIndex = array(0, 0);
+ $this->setKey($this->key);
+ }
+
+ $this->continuousBuffer = false;
+ }
+
+ /**
+ * Dummy function.
+ *
+ * Since RC4 is a stream cipher and not a block cipher, no padding is necessary. The only reason this function is
+ * included is so that you can switch between a block cipher and a stream cipher transparently.
+ *
+ * @see Crypt_RC4::disablePadding()
+ * @access public
+ */
+ function enablePadding()
+ {
+ }
+
+ /**
+ * Dummy function.
+ *
+ * @see Crypt_RC4::enablePadding()
+ * @access public
+ */
+ function disablePadding()
+ {
+ }
+
+ /**
+ * Class destructor.
+ *
+ * Will be called, automatically, if you're using PHP5. If you're using PHP4, call it yourself. Only really
+ * needs to be called if mcrypt is being used.
+ *
+ * @access public
+ */
+ function __destruct()
+ {
+ if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
+ $this->_closeMCrypt();
+ }
+ }
+
+ /**
+ * Properly close the MCrypt objects.
+ *
+ * @access prviate
+ */
+ function _closeMCrypt()
+ {
+ if ( $this->encryptStream !== false ) {
+ if ( $this->continuousBuffer ) {
+ mcrypt_generic_deinit($this->encryptStream);
+ }
+
+ mcrypt_module_close($this->encryptStream);
+
+ $this->encryptStream = false;
+ }
+
+ if ( $this->decryptStream !== false ) {
+ if ( $this->continuousBuffer ) {
+ mcrypt_generic_deinit($this->decryptStream);
+ }
+
+ mcrypt_module_close($this->decryptStream);
+
+ $this->decryptStream = false;
+ }
+ }
+} \ No newline at end of file
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