Enterprise Manager

I'm running GC 10.2.0.3.0 on Oracle Linux, and I'd like to be able to open up GridControl to other users without setting up accounts/passwords for them. Accounts I can handle, passwords, I don't want to handle.

I see that if I create a new GC user via enterprise manager, a new database accout is also created in the EMREP database. I've configured our EMREP database to use radius authentication and it works when I connect via sqlplus to the EMREP database. The user is set to authenticate "externally" and os_authent_prefix is set to ''.

However, after I set up external authentication for a given user, they are no longer able to login to enterprise manager using their radius authenticated password. So something about EM is not capable of radius authentication with the local EMREP database?

Questions for all:
Is it possible to authenticate users of enterprise manager GridControl against an external password store? I have at my disposal: radius (works great for several of our databases), ActiveDirectory (without oracle schema extensions), LDAP (active directory), proxying the EM server with another Apache server.

I do not have a license for OID and the "free use" license for OID does not allow for user management. We cannot we purchase OID for this purpose.

Our GC environment is Linux so Windows OS authentication against AD isn't going to work and we need to support Firefox/IE/Other browsers on various OS's.

I've seen hints that "external authentication" is possible with "generic" sources, but nothing concrete. Anyone doing this?