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<?php |
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/** |
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* Str.php |
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* |
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* PHP version 5 |
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* |
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* @category Dcrypt |
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* @package Dcrypt |
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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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* @link https://github.com/mmeyer2k/dcrypt |
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*/ |
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namespace Dcrypt; |
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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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* @package Dcrypt |
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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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* @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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* @link https://apigen.ci/github/mmeyer2k/dcrypt/namespace-Dcrypt.html |
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*/ |
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final class Str |
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{ |
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/** |
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* Private constant-time strcmp method to use when hash_equals is unavailable. |
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* |
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* @param string $knownHash Hash of the known string |
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* @param string $givenHash Hash of the given string |
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* |
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* @return bool true if the two strings are the same, false otherwise |
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*/ |
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private static function strcmp($knownHash, $givenHash) |
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{ |
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$result = 0; |
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// XOR the bytes of the 2 input hashes and loop over them. |
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// Each byte value is then added to a running total... |
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foreach (\str_split($knownHash ^ $givenHash) as $xbyte) { |
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$result += \ord($xbyte); |
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} |
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// Strings are equal if the final result is exactly zero |
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return 0 === $result; |
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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 $given The string that the user can control |
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* |
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* @return bool |
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*/ |
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public static function equal($known, $given) |
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{ |
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// We hash the 2 inputs at this point because hash_equals is still |
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// vulnerable to timing attacks when the inputs have different sizes. |
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// Inputs are also cast to string like in symfony stringutils. |
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$nonce = Random::bytes(32); |
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$known = \hash_hmac('sha256', (string) $known, $nonce, true); |
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$given = \hash_hmac('sha256', (string) $given, $nonce, true); |
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if (\function_exists('hash_equals')) { |
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return \hash_equals($known, $given); // @codeCoverageIgnore |
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} |
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return self::strcmp($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 $algo Name of algorithm to look up |
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* |
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* @return int |
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*/ |
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public static function hashSize($algo) |
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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) |
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{ |
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if (\function_exists('mb_strlen')) { |
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return \mb_strlen($string, '8bit'); |
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} |
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return \strlen($string); // @codeCoverageIgnore |
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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 |
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* @param int $length |
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* |
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* @return string the extracted part of string; or FALSE on failure, or an empty string. |
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*/ |
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public static function substr($string, $start, $length = null) |
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{ |
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if (\function_exists('mb_substr')) { |
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// Fix a weird quirk in PHP versions prior to 5.4.8 |
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if ($length === null && \version_compare('5.4.8', PHP_VERSION)) { |
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$length = self::strlen($string); |
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} |
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return \mb_substr($string, $start, $length, '8bit'); |
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} |
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return \substr($string, $start, $length); // @codeCoverageIgnore |
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} |
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} |
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mmeyer2k /
dcrypt
