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<?php |
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declare(strict_types=1); |
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/** |
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* Str.php. |
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* |
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* PHP version 7 |
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* |
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* @category Dcrypt |
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* |
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* @author Michael Meyer (mmeyer2k) <[email protected]> |
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* @license http://opensource.org/licenses/MIT The MIT License (MIT) |
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* |
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* @link https://github.com/mmeyer2k/dcrypt |
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*/ |
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namespace Dcrypt; |
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use Exception; |
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/** |
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* Provides time-safe string comparison facilities, and safe string operations |
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* on systems that have mb_* function overloading enabled. |
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* |
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* The functions in this class were inspired by the symfony's StringUtils class. |
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* |
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* @category Dcrypt |
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* |
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* @author Michael Meyer (mmeyer2k) <[email protected]> |
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* @license http://opensource.org/licenses/MIT The MIT License (MIT) |
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* |
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* @link https://github.com/mmeyer2k/dcrypt |
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* @link https://github.com/symfony/Security/blob/master/Core/Util/StringUtils.php |
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* @link https://php.net/manual/en/mbstring.overload.php |
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*/ |
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final class Str |
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{ |
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/** |
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* Compares two strings in constant time. Strings are hashed before |
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* comparison so information is not leaked when strings are not of |
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* equal length. |
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* |
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* @param string $known The string of known length to compare against |
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* @param string $given The string that the user can control |
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* |
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* @throws Exception |
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* |
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* @return bool |
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*/ |
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public static function equal(string $known, string $given): bool |
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{ |
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// Create some entropy |
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$nonce = random_bytes(16); |
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// Prehash the input strings with the nonce |
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$known = hash_hmac('sha256', $known, $nonce, true); |
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$given = hash_hmac('sha256', $given, $nonce, true); |
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return hash_equals($known, $given); |
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} |
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/** |
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* Determine the length of the output of a given hash algorithm in bytes. |
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* |
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* @param string $algo Name of algorithm to look up |
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* |
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* @return int |
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*/ |
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public static function hashSize(string $algo): int |
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{ |
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return self::strlen(hash($algo, 'hash me', true)); |
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} |
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/** |
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* Returns the number of bytes in a string. |
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* |
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* @param string $string The string whose length we wish to obtain |
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* |
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* @return int |
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*/ |
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public static function strlen(string $string): int |
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{ |
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return mb_strlen($string, '8bit'); |
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} |
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/** |
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* Returns part of a string. |
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* |
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* @param string $string The string whose length we wish to obtain |
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* @param int $start Offset to start gathering output |
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* @param int|null $length Distance from starting offset to gather |
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* |
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* @return string |
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*/ |
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public static function substr(string $string, int $start, int $length = null): string |
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{ |
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return mb_substr($string, $start, $length, '8bit'); |
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} |
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/** |
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* Shifts bytes off of the front of a string and return. Input string is modified. |
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* |
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* @param string $input |
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* @param int $bytes |
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* |
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* @return string |
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*/ |
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public static function shift(string &$input, int $bytes): string |
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{ |
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$shift = self::substr($input, 0, $bytes); |
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$input = self::substr($input, $bytes); |
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return $shift; |
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} |
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} |
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mmeyer2k /
dcrypt
