Disabled `mfa-duo` if your CAS doesn't have MFA enabled

[NgSekLong]

Since this project seems to be abundant, at least want to leave this here so help somebody if they come across this:

If you receive this error:

org.jasig.cas.client.validation.TicketValidationException: No principal was found in the response from the CAS server.

Try comment out the following line in web.xml

        <init-param>
            <param-name>authn_method</param-name>
            <param-value>mfa-duo</param-value>
        </init-param>

This happened because your CAS server does not support MFA authentication

[dooblem]

Got the same. Thanks a lot.

In cas server 6.2 logs:

2020-09-18 11:59:59,440 ERROR [org.apereo.cas.authentication.mfa.trigger.HttpRequestMultifactorAuthenticationTrigger] - <No multifactor authentication providers are available in the application context to satisfy [[mfa-duo]]>