I am trying to do the exact same thing and having the exact same problem. Not only is the exception completely useless, but there's no other logging taking place. Even putting system.err.println() tombstones in the code for my custom login module doesn't work. It's as if it can't find the class and decides that the 'principal=null' error is a helpful message to provide. Not. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4197014#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...