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<?php |
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namespace Emarref\Jwt\Encryption; |
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use Emarref\Jwt\Algorithm; |
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/** |
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* @property Algorithm\SymmetricInterface $algorithm |
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*/ |
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class Symmetric extends AbstractEncryption implements EncryptionInterface |
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{ |
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/** |
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* @var string |
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*/ |
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private $secret; |
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/** |
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* @param Algorithm\SymmetricInterface $algorithm |
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*/ |
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public function __construct(Algorithm\SymmetricInterface $algorithm) |
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{ |
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parent::__construct($algorithm); |
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} |
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/** |
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* @return string |
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*/ |
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public function getSecret() |
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{ |
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return $this->secret; |
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} |
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/** |
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* @param string $secret |
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* @return $this |
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*/ |
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public function setSecret($secret) |
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{ |
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$this->secret = $secret; |
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return $this; |
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} |
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/** |
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* @param string $value |
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* @return string |
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*/ |
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public function encrypt($value) |
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{ |
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return $this->algorithm->compute($value); |
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} |
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/** |
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* @param string $value |
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* @param string $signature |
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* @return boolean |
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*/ |
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public function verify($value, $signature) |
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{ |
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$computedValue = $this->algorithm->compute($value); |
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return $this->timingSafeEquals($signature, $computedValue); |
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} |
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/** |
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* A timing safe equals comparison. |
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* |
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* @see http://blog.ircmaxell.com/2014/11/its-all-about-time.html |
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* |
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* @param string $safe The internal (safe) value to be checked |
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* @param string $user The user submitted (unsafe) value |
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* |
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* @return boolean True if the two strings are identical. |
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*/ |
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public function timingSafeEquals($safe, $user) |
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{ |
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if (function_exists('hash_equals')) { |
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return hash_equals($user, $safe); |
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} |
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$safeLen = strlen($safe); |
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$userLen = strlen($user); |
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/* |
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* In general, it's not possible to prevent length leaks. So it's OK to leak the length. |
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* @see http://security.stackexchange.com/questions/49849/timing-safe-string-comparison-avoiding-length-leak |
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*/ |
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if ($userLen != $safeLen) { |
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return false; |
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} |
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$result = 0; |
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for ($i = 0; $i < $userLen; $i++) { |
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$result |= (ord($safe[$i]) ^ ord($user[$i])); |
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} |
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return $result === 0; |
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} |
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} |
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emarref /
jwt
