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<?php
/**
* Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
* This file is licensed under the Affero General Public License version 3 or
* later.
* See the COPYING-README file.
*/
namespace OC\Security;
class StringUtils {
/**
* Compares whether two strings are equal. To prevent guessing of the string
* length this is done by comparing two hashes against each other and afterwards
* a comparison of the real string to prevent against the unlikely chance of
* collisions.
*
* Be aware that this function may leak whether the string to compare have a different
* length.
*
* @param string $expected The expected value
* @param string $input The input to compare against
* @return bool True if the two strings are equal, otherwise false.
*/
public static function equals($expected, $input) {
if(!is_string($expected) || !is_string($input)) {
return false;
}
if(function_exists('hash_equals')) {
return hash_equals($expected, $input);
}
$randomString = \OC::$server->getSecureRandom()->getLowStrengthGenerator()->generate(10);
if(hash('sha512', $expected.$randomString) === hash('sha512', $input.$randomString)) {
if($expected === $input) {
return true;
}
}
return false;
}
}
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