/**
  * @param Assertion $assertion
  * @param int       $now
  * @param int       $allowedSecondsSkew
  */
 protected function validateAuthnStatements(Assertion $assertion, $now, $allowedSecondsSkew)
 {
     if (false == $assertion->getAllAuthnStatements()) {
         return;
     }
     foreach ($assertion->getAllAuthnStatements() as $authnStatement) {
         if (false == Helper::validateNotOnOrAfter($authnStatement->getSessionNotOnOrAfterTimestamp(), $now, $allowedSecondsSkew)) {
             throw new LightSamlValidationException('AuthnStatement attribute SessionNotOnOrAfter MUST be in the future');
         }
         // TODO: Consider validating that authnStatement.AuthnInstant is in the past
     }
 }