[cifs-protocol] [REG:112021212002899] encryption key for NetrLogonSamLogonEx

Obaid Farooqi obaidf at microsoft.com
Wed Feb 15 10:11:23 MST 2012

Hi Matthieu:
Yes, please send me the ttt traces and more details about the problem. Your email did not give me a good grasp of the issue.

Obaid Farooqi
Escalation Engineer | Microsoft

Exceeding your expectations is my highest priority.  If you would like to provide feedback on your case you may contact my manager at nkang at Microsoft dot com

From: Matthieu Patou
Sent: 2/11/2012 5:40 PM
To: Interoperability Documentation Help; pfif at tridgell.net; cifs-protocol at samba.org
Subject: [cifs-protocol] encryption key for NetrLogonSamLogonEx
Hello Dochelp,

A bug report concerning user's session key was reported in samba when
using level 3 validation for NetrLogonSamLogonEx.

I did a bit of investigation and witnessed the corruption if we use
level 3 validation for NetrLogonSamLogonEx and if samba opens more than
1 schannel connection with one DC and is not using the session key of
the latest connection for decrypting the user's session key (and other
encrypted fields) in the Validation 3 response.

I checked that samba is using the same key for encrypting and decrypting
schannel and sensitive fields in the validation 3 response of the
NetrLogonSamLogonEx call.

MS-NRPC seems to indicate that the session key should be the same and I
didn't find a trace in the documentation saying that only the latest
session key exchanged during a NetrAuthenticateX and what seems even
more puzzeling is that using the "old" session key for schannel
encryption and decryption works.

Can you explain us the problem ?

I can do TTTrace as the problem is highly reproducible.


Matthieu Patou
Samba Team

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