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[Security] Use hash_equals when available for constant-time string comparison #11797

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[Security] Use hash_equals when available for constant-time string comparison #11797

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6 changes: 6 additions & 0 deletions src/Symfony/Component/Security/Core/Util/StringUtils.php
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
* String utility functions.
*
* @author Fabien Potencier <fabien@symfony.com>
* @author Kévin Dunglas <dunglas@gmail.com>
*/
class StringUtils
{
Expand All @@ -35,6 +36,11 @@ private function __construct() {}
*/
public static function equals($knownString, $userInput)
{
// Use hash_equals if applicable
if (function_exists('hash_equals') && strlen($knownString) === strlen($userInput)) {
return hash_equals($knownString, $userInput);
}

// Prevent issues if string length is 0
$knownString .= chr(0);
$userInput .= chr(0);
Expand Down