[cifs-protocol] How to get the expanded group memberships for a user

Edgar Olougouna edgaro at microsoft.com
Thu Nov 12 12:53:12 MST 2009

Hi Stefan,

I am looking into this and will update you on my progress.

Best regards,

Edgar A. Olougouna
Sr. SEE, Microsoft DSC Protocol Team

-----Original Message-----
From: Stefan (metze) Metzmacher [mailto:metze at samba.org] 
Sent: Thursday, November 12, 2009 7:47 AM
To: Interoperability Documentation Help; cifs-protocol at samba.org; pfif at tridgell.net
Subject: How to get the expanded group memberships for a user


I'm trying to solve the following problem:

COMPUTERS-DOM has an outgoing forest trust to USERS-DOM.

Samba as a member server in COMPUTERS-DOM want to get fully expanded group memberships of user USERS-DOM\Administrator without knowing the password of USERS-DOM\Administrator.
(The best would be to get the whole PAC structure,  which we're getting if the user is authenticated via KRB5  of netr_LogonSamLogon).

With a 2-way forest trust that's no problem.
Samba can ask a DC of COMPUTER-DOM via LookupNames about the SID of USERS-DOM\Administrator.
Then Samba can use it's machine account and ask a DC of USERS-DOM via LDAP about the tokenGroups of the user (That's how Samba currently work).
The second way would be to use S4U2Self to get the PAC via a Krb5 Ticket.

But with a one-way trust only the LookupNames works, as the DC of COMPUTER-DOM will proxy the request to a DC of USERS-DOM using the trust account.

But Samba can't directly talk to a DC of USERS-DOM using it's machine account. So both LDAP and S4U2Self won't work.

I just found that DRSGetMemberships can also get the users groups. I hoped that it would behave like LookupNames and would be proxied by the DC of COMPUTER-DOM to a DC of USERS-DOM. But I'm unable to trigger this.
Is that by design or am I doing something wrong (DRSGetMemberships works fine for the SID of COMPUTER-DOM\Administrator)?

Is there any other way to solve this Problem?


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