/**
* @param Message $message
* @return \AerialShip\LightSaml\Model\XmlDSig\SignatureCreator|null
* @throws \RuntimeException
*/
private function getMessageSignature(Message $message)
{
$signature = $message->getSignature();
if ($signature && !$signature instanceof SignatureCreator) {
throw new \RuntimeException('Signature must be SignatureCreator');
}
return $signature;
}
