I was looking for the current JAAS integration that exists in JBossESB and google search pointed me to the following:
http://anonsvn.labs.jboss.com/labs/jbossesb/workspace/platform/soa_tags/SOA-4.3.0.IR3/product/rosetta/src/org/jboss/internal/soa/esb/services/security/

Primarily, the file that I looked at was JaasSecurityService.java
http://anonsvn.labs.jboss.com/labs/jbossesb/workspace/platform/soa_tags/SOA-4.3.0.IR3/product/rosetta/src/org/jboss/internal/soa/esb/services/security/JaasSecurityService.java

Is this the correct file?

I see that there is a direct reference to a Sun JDK class. :) This may be an issue with different JDKs.

import com.sun.security.auth.login.ConfigFile;