将此Encrypt - Decrypt PHP类转换为完整的静态PHP类

Question

这是一个很棒的php类,可以在php中进行安全的双向加密.我在一个项目中使用它,需要对它的方法进行数千次调用,

我想将它转换为一个完整的静态类及其所有方法,以提高性能并避免在每次新方法调用时使用新实例

/**
 * A class to handle secure encryption and decryption of arbitrary data
 *
 * Note that this is not just straight encryption.  It also has a few other
 *  features in it to make the encrypted data far more secure.  Note that any
 *  other implementations used to decrypt data will have to do the same exact
 *  operations.  
 *
 * Security Benefits:
 *
 * - Uses Key stretching
 * - Hides the Initialization Vector
 * - Does HMAC verification of source data
 *
 */
class Encryption {

    /**
     * @var string $cipher The mcrypt cipher to use for this instance
     */
    protected $cipher = '';

    /**
     * @var int $mode The mcrypt cipher mode to use
     */
    protected $mode = '';

    /**
     * @var int $rounds The number of rounds to feed into PBKDF2 for key generation
     */
    protected $rounds = 100;

    /**
     * Constructor!
     *
     * @param string $cipher The MCRYPT_* cypher to use for this instance
     * @param int    $mode   The MCRYPT_MODE_* mode to use for this instance
     * @param int    $rounds The number of PBKDF2 rounds to do on the key
     */
    public function __construct($cipher, $mode, $rounds = 100) {
        $this->cipher = $cipher;
        $this->mode = $mode;
        $this->rounds = (int) $rounds;
    }

    /**
     * Decrypt the data with the provided key
     *
     * @param string $data The encrypted datat to decrypt
     * @param string $key  The key to use for decryption
     * 
     * @returns string|false The returned string if decryption is successful
     *                           false if it is not
     */
    public function decrypt($data, $key) {
        $salt = substr($data, 0, 128);
        $enc = substr($data, 128, -64);
        $mac = substr($data, -64);

        list ($cipherKey, $macKey, $iv) = $this->getKeys($salt, $key);

        if ($mac !== hash_hmac('sha512', $enc, $macKey, true)) {
             return false;
        }

        $dec = mcrypt_decrypt($this->cipher, $cipherKey, $enc, $this->mode, $iv);

        $data = $this->unpad($dec);

        return $data;
    }

    /**
     * Encrypt the supplied data using the supplied key
     * 
     * @param string $data The data to encrypt
     * @param string $key  The key to encrypt with
     *
     * @returns string The encrypted data
     */
    public function encrypt($data, $key) {
        $salt = mcrypt_create_iv(128, MCRYPT_DEV_URANDOM);
        list ($cipherKey, $macKey, $iv) = $this->getKeys($salt, $key);

        $data = $this->pad($data);

        $enc = mcrypt_encrypt($this->cipher, $cipherKey, $data, $this->mode, $iv);

        $mac = hash_hmac('sha512', $enc, $macKey, true);
        return $salt . $enc . $mac;
    }

    /**
     * Generates a set of keys given a random salt and a master key
     *
     * @param string $salt A random string to change the keys each encryption
     * @param string $key  The supplied key to encrypt with
     *
     * @returns array An array of keys (a cipher key, a mac key, and a IV)
     */
    protected function getKeys($salt, $key) {
        $ivSize = mcrypt_get_iv_size($this->cipher, $this->mode);
        $keySize = mcrypt_get_key_size($this->cipher, $this->mode);
        $length = 2 * $keySize + $ivSize;

        $key = $this->pbkdf2('sha512', $key, $salt, $this->rounds, $length);

        $cipherKey = substr($key, 0, $keySize);
        $macKey = substr($key, $keySize, $keySize);
        $iv = substr($key, 2 * $keySize);
        return array($cipherKey, $macKey, $iv);
    }

    /**
     * Stretch the key using the PBKDF2 algorithm
     *
     * @see http://en.wikipedia.org/wiki/PBKDF2
     *
     * @param string $algo   The algorithm to use
     * @param string $key    The key to stretch
     * @param string $salt   A random salt
     * @param int    $rounds The number of rounds to derive
     * @param int    $length The length of the output key
     *
     * @returns string The derived key.
     */
    protected function pbkdf2($algo, $key, $salt, $rounds, $length) {
        $size   = strlen(hash($algo, '', true));
        $len    = ceil($length / $size);
        $result = '';
        for ($i = 1; $i <= $len; $i++) {
            $tmp = hash_hmac($algo, $salt . pack('N', $i), $key, true);
            $res = $tmp;
            for ($j = 1; $j < $rounds; $j++) {
                 $tmp  = hash_hmac($algo, $tmp, $key, true);
                 $res ^= $tmp;
            }
            $result .= $res;
        }
        return substr($result, 0, $length);
    }

    protected function pad($data) {
        $length = mcrypt_get_block_size($this->cipher, $this->mode);
        $padAmount = $length - strlen($data) % $length;
        if ($padAmount == 0) {
            $padAmount = $length;
        }
        return $data . str_repeat(chr($padAmount), $padAmount);
    }

    protected function unpad($data) {
        $length = mcrypt_get_block_size($this->cipher, $this->mode);
        $last = ord($data[strlen($data) - 1]);
        if ($last > $length) return false;
        if (substr($data, -1 * $last) !== str_repeat(chr($last), $last)) {
            return false;
        }
        return substr($data, 0, -1 * $last);
    }
}

它的用法是

$e = new Encryption(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC);
$encryptedData = $e->encrypt($data, $key);

$e2 = new Encryption(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC);
$data = $e2->decrypt($encryptedData, $key);

我想要的东西

Encryption::encrypt($data, $key);
Encryption::decrypt($encryptedData, $key);

谢谢.

Answer 1

我将提出一些解决方案和想法,以帮助您朝着正确的方向前进.但是,我对您的代码有严重的担忧,必须首先要求您不要在实时环境中使用此代码.

与许多密码学研究人员不同,他们会告诉你"不要编写加密代码"并将其留在那里,我采用写加密代码,不发布或使用它的路径.

您向Stack Overflow询问有关将类转换为使用静态方法的事实告诉我您可能还没有资格在PHP中编写加密.即使你对语言比较熟悉,我也会强烈提醒你远离你的方向.

请改用此PHP库.我已经回顾过了.别人也有.它尚未经过正式审核,但更多的原因是作者没有花费数千美元投入正式审核而不是缺乏对安全和高质量代码的奉献精神.

以下是我发现的一些对加密库来说很危险的事情.这并不意味着攻击; 我只是想告诉你这个领域的一些危险.

在构造函数中没有健全性检查

你怎么知道$this->cipher和$this->mode有效mcrypt的常量？

浪费的熵

$salt = mcrypt_create_iv(128, MCRYPT_DEV_URANDOM);

128字节的熵是1024位的熵; 远远超过您对AES的需求.

使用substr()被认为对加密有害

PHP具有这个功能mbstring.func_overload,它可以完全改变函数等行为substr(),strlen(),以便使用多字节(Unicode)逻辑而不是二进制字符串逻辑.此行为的典型结果是它导致生成的子字符串中的字节数不正确.这很糟糕.有多糟糕取决于攻击者的创造力.

在启用此功能的系统中,您必须显式调用mb_substr($string, '8bit')以获取原始二进制字符串中的字节数.但是,此功能并非在所有系统上都可用.

使用substr()疯狂放弃切割原始二进制字符串是危险的.

定时攻击MAC验证

if ($mac !== hash_hmac('sha512', $enc, $macKey, true))

Anthony Ferrara已经详细介绍了这个话题.

综上所述

我真诚地希望,这篇文章能够得到建设性批评的预期基调,并且你对加密工程中疯狂细节的数量有所启发.

此外,我希望这不会让你远离对该领域的更多了解.请详细了解它!这是一个令人兴奋的领域,每个人都有更多的手在甲板上更好!你甚至有一天可能会让我知道一个我无法想象的复杂攻击.

但是今天,现在,在生产系统中使用业余加密来保护敏感数据是危险的.您应该自己(或您的客户/雇主,如果适用)来决定更重要的事情:实验,或保护他们的信息不受损害.我不会为你做出那个选择.