parse host from url for webauthn library

data/web/inc/prerequisites.inc.php

@@ -66,8 +66,9 @@ $qrprovider = new RobThree\Auth\Providers\Qr\QRServerProvider();
 $tfa = new RobThree\Auth\TwoFactorAuth($OTP_LABEL, 6, 30, 'sha1', $qrprovider);
 
 // FIDO2
+$server_name = parse_url('https://' . $_SERVER['HTTP_HOST'], PHP_URL_HOST);
 $formats = $GLOBALS['FIDO2_FORMATS'];
-$WebAuthn = new lbuchs\WebAuthn\WebAuthn('WebAuthn Library', $_SERVER['SERVER_NAME'], $formats);
+$WebAuthn = new lbuchs\WebAuthn\WebAuthn('WebAuthn Library', $server_name, $formats);
 // only include root ca's when needed
 if (getenv('WEBAUTHN_ONLY_TRUSTED_VENDORS') == 'y') $WebAuthn->addRootCertificates($_SERVER['DOCUMENT_ROOT'] . '/inc/lib/WebAuthn/rootCertificates');