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<?php
/**
* Pure-PHP implementation of Triple DES.
*
* Uses mcrypt, if available, and an internal implementation, otherwise. Operates in the EDE3 mode (encrypt-decrypt-encrypt).
*
* PHP version 5
*
* Here's a short example of how to use this library:
* <code>
* <?php
* include 'vendor/autoload.php';
*
* $des = new \phpseclib3\Crypt\TripleDES('ctr');
*
* $des->setKey('abcdefghijklmnopqrstuvwx');
*
* $size = 10 * 1024;
* $plaintext = '';
* for ($i = 0; $i < $size; $i++) {
* $plaintext.= 'a';
* }
*
* echo $des->decrypt($des->encrypt($plaintext));
* ?>
* </code>
*
* @author Jim Wigginton <terrafrost@php.net>
* @copyright 2007 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://phpseclib.sourceforge.net
*/
namespace phpseclib3\Crypt;
/**
* Pure-PHP implementation of Triple DES.
*
* @author Jim Wigginton <terrafrost@php.net>
*/
class TripleDES extends DES
{
/**
* Encrypt / decrypt using inner chaining
*
* Inner chaining is used by SSH-1 and is generally considered to be less secure then outer chaining (self::MODE_CBC3).
*/
const MODE_3CBC = -2;
/**
* Encrypt / decrypt using outer chaining
*
* Outer chaining is used by SSH-2 and when the mode is set to \phpseclib3\Crypt\Common\BlockCipher::MODE_CBC.
*/
const MODE_CBC3 = self::MODE_CBC;
/**
* Key Length (in bytes)
*
* @see \phpseclib3\Crypt\TripleDES::setKeyLength()
* @var int
*/
protected $key_length = 24;
/**
* The mcrypt specific name of the cipher
*
* @see \phpseclib3\Crypt\DES::cipher_name_mcrypt
* @see \phpseclib3\Crypt\Common\SymmetricKey::cipher_name_mcrypt
* @var string
*/
protected $cipher_name_mcrypt = 'tripledes';
/**
* Optimizing value while CFB-encrypting
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::cfb_init_len
* @var int
*/
protected $cfb_init_len = 750;
/**
* max possible size of $key
*
* @see self::setKey()
* @see \phpseclib3\Crypt\DES::setKey()
* @var string
*/
protected $key_length_max = 24;
/**
* Internal flag whether using self::MODE_3CBC or not
*
* @var bool
*/
private $mode_3cbc;
/**
* The \phpseclib3\Crypt\DES objects
*
* Used only if $mode_3cbc === true
*
* @var array
*/
private $des;
/**
* Default Constructor.
*
* Determines whether or not the mcrypt or OpenSSL extensions should be used.
*
* $mode could be:
*
* - ecb
*
* - cbc
*
* - ctr
*
* - cfb
*
* - ofb
*
* - 3cbc
*
* - cbc3 (same as cbc)
*
* @see \phpseclib3\Crypt\DES::__construct()
* @see \phpseclib3\Crypt\Common\SymmetricKey::__construct()
* @param string $mode
*/
public function __construct($mode)
{
switch (strtolower($mode)) {
// In case of self::MODE_3CBC, we init as CRYPT_DES_MODE_CBC
// and additional flag us internally as 3CBC
case '3cbc':
parent::__construct('cbc');
$this->mode_3cbc = true;
// This three $des'es will do the 3CBC work (if $key > 64bits)
$this->des = [
new DES('cbc'),
new DES('cbc'),
new DES('cbc'),
];
// we're going to be doing the padding, ourselves, so disable it in the \phpseclib3\Crypt\DES objects
$this->des[0]->disablePadding();
$this->des[1]->disablePadding();
$this->des[2]->disablePadding();
break;
case 'cbc3':
$mode = 'cbc';
// fall-through
// If not 3CBC, we init as usual
default:
parent::__construct($mode);
if ($this->mode == self::MODE_STREAM) {
throw new BadModeException('Block ciphers cannot be ran in stream mode');
}
}
}
/**
* Test for engine validity
*
* This is mainly just a wrapper to set things up for \phpseclib3\Crypt\Common\SymmetricKey::isValidEngine()
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::__construct()
* @param int $engine
* @return bool
*/
protected function isValidEngineHelper($engine)
{
if ($engine == self::ENGINE_OPENSSL) {
$this->cipher_name_openssl_ecb = 'des-ede3';
$mode = $this->openssl_translate_mode();
$this->cipher_name_openssl = $mode == 'ecb' ? 'des-ede3' : 'des-ede3-' . $mode;
}
return parent::isValidEngineHelper($engine);
}
/**
* Sets the initialization vector.
*
* SetIV is not required when \phpseclib3\Crypt\Common\SymmetricKey::MODE_ECB is being used.
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::setIV()
* @param string $iv
*/
public function setIV($iv)
{
parent::setIV($iv);
if ($this->mode_3cbc) {
$this->des[0]->setIV($iv);
$this->des[1]->setIV($iv);
$this->des[2]->setIV($iv);
}
}
/**
* Sets the key length.
*
* Valid key lengths are 128 and 192 bits.
*
* If you want to use a 64-bit key use DES.php
*
* @see \phpseclib3\Crypt\Common\SymmetricKey:setKeyLength()
* @throws \LengthException if the key length is invalid
* @param int $length
*/
public function setKeyLength($length)
{
switch ($length) {
case 128:
case 192:
break;
default:
throw new \LengthException('Key size of ' . $length . ' bits is not supported by this algorithm. Only keys of sizes 128 or 192 bits are supported');
}
parent::setKeyLength($length);
}
/**
* Sets the key.
*
* Triple DES can use 128-bit (eg. strlen($key) == 16) or 192-bit (eg. strlen($key) == 24) keys.
*
* DES also requires that every eighth bit be a parity bit, however, we'll ignore that.
*
* @see \phpseclib3\Crypt\DES::setKey()
* @see \phpseclib3\Crypt\Common\SymmetricKey::setKey()
* @throws \LengthException if the key length is invalid
* @param string $key
*/
public function setKey($key)
{
if ($this->explicit_key_length !== false && strlen($key) != $this->explicit_key_length) {
throw new \LengthException('Key length has already been set to ' . $this->explicit_key_length . ' bytes and this key is ' . strlen($key) . ' bytes');
}
switch (strlen($key)) {
case 16:
$key .= substr($key, 0, 8);
break;
case 24:
break;
default:
throw new \LengthException('Key of size ' . strlen($key) . ' not supported by this algorithm. Only keys of sizes 16 or 24 are supported');
}
// copied from self::setKey()
$this->key = $key;
$this->key_length = strlen($key);
$this->changed = $this->nonIVChanged = true;
$this->setEngine();
if ($this->mode_3cbc) {
$this->des[0]->setKey(substr($key, 0, 8));
$this->des[1]->setKey(substr($key, 8, 8));
$this->des[2]->setKey(substr($key, 16, 8));
}
}
/**
* Encrypts a message.
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::encrypt()
* @param string $plaintext
* @return string $cipertext
*/
public function encrypt($plaintext)
{
// parent::en/decrypt() is able to do all the work for all modes and keylengths,
// except for: self::MODE_3CBC (inner chaining CBC) with a key > 64bits
// if the key is smaller then 8, do what we'd normally do
if ($this->mode_3cbc && strlen($this->key) > 8) {
return $this->des[2]->encrypt(
$this->des[1]->decrypt(
$this->des[0]->encrypt(
$this->pad($plaintext)
)
)
);
}
return parent::encrypt($plaintext);
}
/**
* Decrypts a message.
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::decrypt()
* @param string $ciphertext
* @return string $plaintext
*/
public function decrypt($ciphertext)
{
if ($this->mode_3cbc && strlen($this->key) > 8) {
return $this->unpad(
$this->des[0]->decrypt(
$this->des[1]->encrypt(
$this->des[2]->decrypt(
str_pad($ciphertext, (strlen($ciphertext) + 7) & 0xFFFFFFF8, "\0")
)
)
)
);
}
return parent::decrypt($ciphertext);
}
/**
* 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 $des->encrypt(substr($plaintext, 0, 8));
* echo $des->encrypt(substr($plaintext, 8, 8));
* </code>
* <code>
* echo $des->encrypt($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>
* $des->encrypt(substr($plaintext, 0, 8));
* echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
* </code>
* <code>
* echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
* </code>
*
* With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different
* outputs. The reason is due to the fact that the initialization vector's change after every encryption /
* decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
*
* Put another way, when the continuous buffer is enabled, the state of the \phpseclib3\Crypt\DES() object changes after each
* encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that
* continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them),
* however, they are also less intuitive and more likely to cause you problems.
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::enableContinuousBuffer()
* @see self::disableContinuousBuffer()
*/
public function enableContinuousBuffer()
{
parent::enableContinuousBuffer();
if ($this->mode_3cbc) {
$this->des[0]->enableContinuousBuffer();
$this->des[1]->enableContinuousBuffer();
$this->des[2]->enableContinuousBuffer();
}
}
/**
* Treat consecutive packets as if they are a discontinuous buffer.
*
* The default behavior.
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::disableContinuousBuffer()
* @see self::enableContinuousBuffer()
*/
public function disableContinuousBuffer()
{
parent::disableContinuousBuffer();
if ($this->mode_3cbc) {
$this->des[0]->disableContinuousBuffer();
$this->des[1]->disableContinuousBuffer();
$this->des[2]->disableContinuousBuffer();
}
}
/**
* Creates the key schedule
*
* @see \phpseclib3\Crypt\DES::setupKey()
* @see \phpseclib3\Crypt\Common\SymmetricKey::setupKey()
*/
protected function setupKey()
{
switch (true) {
// if $key <= 64bits we configure our internal pure-php cipher engine
// to act as regular [1]DES, not as 3DES. mcrypt.so::tripledes does the same.
case strlen($this->key) <= 8:
$this->des_rounds = 1;
break;
// otherwise, if $key > 64bits, we configure our engine to work as 3DES.
default:
$this->des_rounds = 3;
// (only) if 3CBC is used we have, of course, to setup the $des[0-2] keys also separately.
if ($this->mode_3cbc) {
$this->des[0]->setupKey();
$this->des[1]->setupKey();
$this->des[2]->setupKey();
// because $des[0-2] will, now, do all the work we can return here
// not need unnecessary stress parent::setupKey() with our, now unused, $key.
return;
}
}
// setup our key
parent::setupKey();
}
/**
* Sets the internal crypt engine
*
* @see \phpseclib3\Crypt\Common\SymmetricKey::__construct()
* @see \phpseclib3\Crypt\Common\SymmetricKey::setPreferredEngine()
* @param int $engine
*/
public function setPreferredEngine($engine)
{
if ($this->mode_3cbc) {
$this->des[0]->setPreferredEngine($engine);
$this->des[1]->setPreferredEngine($engine);
$this->des[2]->setPreferredEngine($engine);
}
parent::setPreferredEngine($engine);
}
}
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