How do I get the Hibernate caller principal inside established from within an auditing interceptor?

Issue

• I need to get the "caller principal" from within Hibernate in a "Stateless Session Bean/Hibernate architecture" that uses different ways to establish user identity.
• Once inside the EJB layer, I have Hibernate saving entities.  Hibernate uses an auditing Entity Interceptor which must get the caller principal and set audit field in the database. 

• How do I get the caller principal inside established from either one of these login techniques from within this auditing interceptor?

  Subject caller = (Subject) PolicyContext.getContext("javax.security.auth.Subject.container");