There is no out-of-the-box JAAS login modules that will allow you to do that (at least not with JBoss).
You might be able to extract and reuse the UnixLoginModule of the dwarf server framework: http://220.127.116.11/doc/dwarf/api/SK/gnome/dwarf/auth/login/UnixLoginModule.html
Actually, forget what I said, dwarf is not open source. You just have a free binary distribution.....
The sun jdk for a given platform has an os specific login module. See the javadoc:
Also, see if this has anything iteresting:
I tried to use these a little while ago, but they are pretty useless in a client/server context like in JBoss.
The NT and Unix module are just populated a JAAS subject with some data coming from the currently authenticated user (the user running the Java code).
You cannot provide an arbitrary user name and password to them so they can actually perform the authentication.
But the jaas-pam stuff looks promissing :-)