// Check if there is sso id as well as sessionkey
if (username == null || password == null) {
log.trace("Username is null or password(sessionkey) is null:fallback to form auth");
return super.authenticate(request, response, config);
}
principal = realm.authenticate(username, password);
if (principal == null) {
forwardToErrorPage(request, response, config);
return false;
}