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<?php |
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/** |
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* Encryption and Decryption Class |
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* |
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*/ |
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class Encryption |
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{ |
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/** |
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* Cipher algorithm |
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* |
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* @var string |
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*/ |
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const CIPHER = 'aes-256-cbc'; |
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/** |
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* Hash function |
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* |
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* @var string |
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*/ |
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const HASH_FUNCTION = 'sha256'; |
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/** |
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* constructor for Encryption object. |
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* |
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* @access private |
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*/ |
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private function __construct() |
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{ |
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} |
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/** |
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* Encrypt a string. |
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* |
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* @access public |
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* @static static method |
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* @param string $plain |
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* @return string |
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* @throws Exception If functions don't exists |
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*/ |
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public static function encrypt($plain) |
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{ |
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if (!function_exists('openssl_cipher_iv_length') || |
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!function_exists('openssl_random_pseudo_bytes') || |
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!function_exists('openssl_encrypt')) { |
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throw new Exception('Encryption function doesn\'t exist'); |
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} |
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// generate initialization vector, |
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// this will make $iv different every time, |
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// so, encrypted string will be also different. |
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$iv_size = openssl_cipher_iv_length(self::CIPHER); |
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$iv = openssl_random_pseudo_bytes($iv_size); |
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// generate key for authentication using ENCRYPTION_KEY & HMAC_SALT |
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$key = mb_substr(hash(self::HASH_FUNCTION, Config::get('ENCRYPTION_KEY') . Config::get('HMAC_SALT')), 0, 32, '8bit'); |
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// append initialization vector |
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$encrypted_string = openssl_encrypt($plain, self::CIPHER, $key, OPENSSL_RAW_DATA, $iv); |
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$ciphertext = $iv . $encrypted_string; |
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// apply the HMAC |
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$hmac = hash_hmac('sha256', $ciphertext, $key); |
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return $hmac . $ciphertext; |
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} |
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/** |
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* Decrypted a string. |
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* |
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* @access public |
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* @static static method |
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* @param string $ciphertext |
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* @return string |
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* @throws Exception If $ciphertext is empty, or If functions don't exists |
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*/ |
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public static function decrypt($ciphertext) |
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{ |
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if (empty($ciphertext)) { |
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throw new Exception('The String to decrypt can\'t be empty'); |
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} |
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if (!function_exists('openssl_cipher_iv_length') || |
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!function_exists('openssl_decrypt')) { |
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throw new Exception('Encryption function doesn\'t exist'); |
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} |
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// generate key used for authentication using ENCRYPTION_KEY & HMAC_SALT |
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$key = mb_substr(hash(self::HASH_FUNCTION, Config::get('ENCRYPTION_KEY') . Config::get('HMAC_SALT')), 0, 32, '8bit'); |
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// split cipher into: hmac, cipher & iv |
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$macSize = 64; |
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$hmac = mb_substr($ciphertext, 0, $macSize, '8bit'); |
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$iv_cipher = mb_substr($ciphertext, $macSize, null, '8bit'); |
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// generate original hmac & compare it with the one in $ciphertext |
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$originalHmac = hash_hmac('sha256', $iv_cipher, $key); |
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if (!self::hashEquals($hmac, $originalHmac)) { |
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return false; |
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} |
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// split out the initialization vector and cipher |
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$iv_size = openssl_cipher_iv_length(self::CIPHER); |
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$iv = mb_substr($iv_cipher, 0, $iv_size, '8bit'); |
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$cipher = mb_substr($iv_cipher, $iv_size, null, '8bit'); |
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return openssl_decrypt($cipher, self::CIPHER, $key, OPENSSL_RAW_DATA, $iv); |
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} |
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/** |
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* A timing attack resistant comparison. |
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* |
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* @access private |
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* @static static method |
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* @param string $hmac The hmac from the ciphertext being decrypted. |
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* @param string $compare The comparison hmac. |
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* @return bool |
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* @see https://github.com/sarciszewski/php-future/blob/bd6c91fb924b2b35a3e4f4074a642868bd051baf/src/Security.php#L36 |
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*/ |
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private static function hashEquals($hmac, $compare) |
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{ |
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if (function_exists('hash_equals')) { |
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return hash_equals($hmac, $compare); |
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} |
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// if hash_equals() is not available, |
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// then use the following snippet. |
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// It's equivalent to hash_equals() in PHP 5.6. |
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$hashLength = mb_strlen($hmac, '8bit'); |
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$compareLength = mb_strlen($compare, '8bit'); |
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if ($hashLength !== $compareLength) { |
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return false; |
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} |
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$result = 0; |
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for ($i = 0; $i < $hashLength; $i++) { |
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$result |= (ord($hmac[$i]) ^ ord($compare[$i])); |
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} |
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return $result === 0; |
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} |
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} |
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panique /
huge
