private Optional<MultifactorAuthenticationProvider> unmatchedMultifactorAuthenticationTrigger(final Principal principal,
                                                                                                  final RegisteredService registeredService) {
        if (casProperties.getAuthn().getMfa().getTriggers().getPrincipal().isDenyIfUnmatched()) {
            throw new AuthenticationException(new MultifactorAuthenticationRequiredException(registeredService, principal));
        }
        return Optional.empty();
    }
This is {@link RegisteredServicePrincipalAttributeMultifactorAuthenticationTrigger}.

@author Misagh Moayyed
@since 6.0.0
core/cas-server-core-authentication-mfa-api/src/main/java/org/apereo/cas/authentication/mfa/trigger/RegisteredServicePrincipalAttributeMultifactorAuthenticationTrigger.java