How to search nested authorities?

I'm using OpenLDAP 2.3.x, Spring LDAP 1.3.0.RELEASE and Spring Security 3.0.4.RELEASE.

I have the following Group->member structure:

A->(user1)
B->(A)

When I get the authorities of user1, Spring returns only Group A.

I need to get all the groups that has A as member.

What I'm doing is modifying the userContextMapper bean in mapUserFromContext method and searching manually in LDAP all the nested groups.

The problem I'm having with my solution is that I can't find a way to create a GrantedAuthority.

So, I have 2 questions:

1) Is there a better way to find the nested Authorities?
2) How can I create a new GrantedAuthority object?

Thanks in advance,
Neuquino

Did you ever find a solution to this problem?