Database access using LDAP Authentication

All:

Jr. DBA here looking for a little help on a project she's been given. Any thoughts & ideas you have are greatly appreciated.

THE SITUATION:
After Collaborate06, I suggested to our managers that we use Profiles on our 40+ databases for added security. After some hemming & hawing, security group agreed, and we began to put Profile Plans into motion. At this time the department realized that if they had a direct Database account, they would have to change their password, which meant in some circumstances, on all 40 databases. This caused some grumbling, but it wasn't too bad.

At this time the head of Systems said 1 word to the head DBA that would simultaneously make all the profile research instantly trash and my life hell: LDAP.

Yes, he wants us to have oracle use LDAP for it's user/schema authentication.

SYSTEMS:
Oracle 9.2.0.6
LDAP v3 (not Oracle's LDAP)
All 40+ databases & 2 LDAPs are on different Unix boxes.

EXAMPLE OF WANTED RESULTS:
To make sure I am not being difficult, here's the prime example: 1) I open SQLPLUS and type in my Oracle Userid & password (scott/tiger).

2) Oracle then somehow takes the userid & password to a centralized LDAP.
3) LDAP replies with either: "Yep, that's right" or "No, reject session".
4) Oracle then allows access (depending on LDAP's response), and uses it's the users role/sys/tab privs to say what that user has access to.

RESEARCH:
I have seen where you can authenticate through an htmldb app using the DBMS_LDAP package, but we're not going through a 3rd party app, nor do I think a login server is quite what we're looking for here, but maybe this is how it has to be done?

I saw the wonderful "LDAP_AUTHENTICATE procedure for Active Directory" from this list, and tried it as a great jumping-off point, but can't figure out quite how to use it in relation to how Oracle logs in its users.

Metalink seems to take you into stray paths, and the SSO books around have to do with 10g, if it's even SSO I'm quite looking for. And Google seems to think I'm insane.

QUESTIONS:
1) Is it even possible to use LDAP to authenticate Oracle users directly from Oracle? How would I go about doing this?

2) If this is possible, via some sort of login trigger or something, then is it possible to exclude specific users? We obviously don't want SYS or OP$ORACLE going through LDAP due to LDAP Failure making the database useless.

Thank you in advance for all of your help, and thanks for all the ideas that this list has given me!

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