ExternalLink::checkUserReadAccess

static function checkUserReadAccess(array $params, $userId)
{
	if(!BitrixDiskExternalLink::isValidValueForField('HASH', $params['hash']))
	{
		//bad hash
		return false;
	}
	$externalLink = BitrixDiskExternalLink::load(array('=HASH' => $params['hash']), array('OBJECT'));
	if(!$externalLink || $externalLink->isExpired() || $externalLink->hasPassword())
	{
		//could not make preview
		return false;
	}
	return true;
}