TripleDES.php

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<?php

namespace phpseclib\Crypt;

use phpseclib\Crypt\Base;
use phpseclib\Crypt\DES;

class TripleDES extends DES
{
    const MODE_3CBC = -2;

    const MODE_CBC3 = Base::MODE_CBC;

    var $key_length = 24;

    var $password_default_salt = 'phpseclib';

    var $cipher_name_mcrypt = 'tripledes';

    var $cfb_init_len = 750;

    var $key_length_max = 24;

    var $mode_3cbc;

    var $des;

    function __construct($mode = Base::MODE_CBC)
    {
        switch ($mode) {
            // In case of self::MODE_3CBC, we init as CRYPT_DES_MODE_CBC
            // and additional flag us internally as 3CBC
            case self::MODE_3CBC:
                parent::__construct(Base::MODE_CBC);
                $this->mode_3cbc = true;

                // This three $des'es will do the 3CBC work (if $key > 64bits)
                $this->des = array(
                    new DES(Base::MODE_CBC),
                    new DES(Base::MODE_CBC),
                    new DES(Base::MODE_CBC),
                );

                // we're going to be doing the padding, ourselves, so disable it in the \phpseclib\Crypt\DES objects
                $this->des[0]->disablePadding();
                $this->des[1]->disablePadding();
                $this->des[2]->disablePadding();
                break;
            // If not 3CBC, we init as usual
            default:
                parent::__construct($mode);
        }
    }

    function isValidEngine($engine)
    {
        if ($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::isValidEngine($engine);
    }

    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);
        }
    }

    function setKeyLength($length)
    {
        $length >>= 3;
        switch (true) {
            case $length <= 8:
                $this->key_length = 8;
                break;
            case $length <= 16:
                $this->key_length = 16;
                break;
            default:
                $this->key_length = 24;
        }

        parent::setKeyLength($length);
    }

    function setKey($key)
    {
        $length = $this->explicit_key_length ? $this->key_length : strlen($key);
        if ($length > 8) {
            $key = str_pad(substr($key, 0, 24), 24, chr(0));
            // if $key is between 64 and 128-bits, use the first 64-bits as the last, per this:
            // http://php.net/function.mcrypt-encrypt#47973
            $key = $length <= 16 ? substr_replace($key, substr($key, 0, 8), 16) : substr($key, 0, 24);
        } else {
            $key = str_pad($key, 8, chr(0));
        }
        parent::setKey($key);

        // And in case of self::MODE_3CBC:
        // if key <= 64bits we not need the 3 $des to work,
        // because we will then act as regular DES-CBC with just a <= 64bit key.
        // So only if the key > 64bits (> 8 bytes) we will call setKey() for the 3 $des.
        if ($this->mode_3cbc && $length > 8) {
            $this->des[0]->setKey(substr($key,  0, 8));
            $this->des[1]->setKey(substr($key,  8, 8));
            $this->des[2]->setKey(substr($key, 16, 8));
        }
    }

    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);
    }

    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);
    }

    function enableContinuousBuffer()
    {
        parent::enableContinuousBuffer();
        if ($this->mode_3cbc) {
            $this->des[0]->enableContinuousBuffer();
            $this->des[1]->enableContinuousBuffer();
            $this->des[2]->enableContinuousBuffer();
        }
    }

    function disableContinuousBuffer()
    {
        parent::disableContinuousBuffer();
        if ($this->mode_3cbc) {
            $this->des[0]->disableContinuousBuffer();
            $this->des[1]->disableContinuousBuffer();
            $this->des[2]->disableContinuousBuffer();
        }
    }

    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();
    }

    function setPreferredEngine($engine)
    {
        if ($this->mode_3cbc) {
            $this->des[0]->setPreferredEngine($engine);
            $this->des[1]->setPreferredEngine($engine);
            $this->des[2]->setPreferredEngine($engine);
        }

        return parent::setPreferredEngine($engine);
    }
}