Git-Center/Crypt/RC4.php

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2013-10-02 12:28:09 +00:00
<?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 referred 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: 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_RC4
* @author Jim Wigginton <terrafrost@php.net>
* @copyright MMVII Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @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;
/**
* 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;
/**
* Continuous Buffer status
*
* @see Crypt_RC4::enableContinuousBuffer()
* @var Boolean
* @access private
*/
var $continuousBuffer = false;
/**
* Default Constructor.
*
* Determines whether or not the mcrypt extension should be used.
*
* @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')) && in_array('arcfour', mcrypt_list_algorithms()):
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;
}
$this->encryptStream = mcrypt_module_open($this->mode, '', MCRYPT_MODE_STREAM, '');
$this->decryptStream = mcrypt_module_open($this->mode, '', MCRYPT_MODE_STREAM, '');
}
}
/**
* 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 = $key;
if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
mcrypt_generic_init($this->encryptStream, $this->key, '');
mcrypt_generic_init($this->decryptStream, $this->key, '');
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;
}
/**
* Sets the password.
*
* Depending on what $method is set to, setPassword()'s (optional) parameters are as follows:
* {@link http://en.wikipedia.org/wiki/PBKDF2 pbkdf2}:
* $hash, $salt, $count, $dkLen
*
* @param String $password
* @param optional String $method
* @access public
*/
function setPassword($password, $method = 'pbkdf2')
{
$key = '';
switch ($method) {
default: // 'pbkdf2'
list(, , $hash, $salt, $count) = func_get_args();
if (!isset($hash)) {
$hash = 'sha1';
}
// WPA and WPA2 use the SSID as the salt
if (!isset($salt)) {
$salt = 'phpseclib/salt';
}
// RFC2898#section-4.2 uses 1,000 iterations by default
// WPA and WPA2 use 4,096.
if (!isset($count)) {
$count = 1000;
}
if (!isset($dkLen)) {
$dkLen = 128;
}
if (!class_exists('Crypt_Hash')) {
require_once('Crypt/Hash.php');
}
$i = 1;
while (strlen($key) < $dkLen) {
//$dk.= $this->_pbkdf($password, $salt, $count, $i++);
$hmac = new Crypt_Hash();
$hmac->setHash($hash);
$hmac->setKey($password);
$f = $u = $hmac->hash($salt . pack('N', $i++));
for ($j = 2; $j <= $count; $j++) {
$u = $hmac->hash($u);
$f^= $u;
}
$key.= $f;
}
}
$this->setKey(substr($key, 0, $dkLen));
}
/**
* 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)
{
}
/**
* 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->continuousBuffer) {
mcrypt_generic_init($this->$keyStream, $this->key, '');
}
return mcrypt_generic($this->$keyStream, $text);
}
if ($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($plaintext, 8, 8)));
* </code>
*
* With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different
* outputs. The reason is due to the fact that the initialization vector's change after every encryption /
* decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
*
* Put another way, when the continuous buffer is enabled, the state of the Crypt_DES() object changes after each
* encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that
* continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them),
* however, they are also less intuitive and more likely to cause you problems.
*
* @see Crypt_RC4::disableContinuousBuffer()
* @access public
*/
function enableContinuousBuffer()
{
if ( CRYPT_RC4_MODE == CRYPT_RC4_MODE_MCRYPT ) {
mcrypt_generic_init($this->encryptStream, $this->key, '');
mcrypt_generic_init($this->decryptStream, $this->key, '');
}
$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->encryptStream = $this->decryptStream = false;
}
$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()
{
}
}
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