for the benefit of the archives...
I came up with three examples of Kerberos authentication with Tomcat and
JAASRealm:
http://wiki.wsmoak.net/cgi-bin/wiki.pl?TomcatJspExamples
The first one is converting the 'jsp-examples' webapp to use Kerberos by
adding/changing config files, no Java code
authentication with Kerberos) yet, but Google just isn't turning up
anything.
I started at the Realm HowTo [0] and found the JAASRealm section.
From here it looks like I need to write my own LoginModule. Except... there
is com.sun.security.auth.module.Krb5LoginModule [1]. Can I just use
