[cifs-protocol] [REG: 112082371227089] SMB3 encryption and Oplock/Lease break notifications

[Edgar Olougouna]

Metze,

We confirm that Oplock break notifications/acknowledgments/responses must be encrypted when encryption is active. For an Oplock, the FileID is used to derive the SessionId which is set in the notification/acknowledgement/response. See details in Sections 3.2.5.19.1   Receiving an Oplock Break Notification, 3.3.5.22.1   Processing an Oplock Acknowledgment.

Lease break notifications - sent by the server - do not have a SessionId, and as a result, are neither signed nor encrypted.  Lease keys are not tied to a particular session from the client.
However, Lease break acknowledgements sent by the client - and their responses sent by the server - must be encrypted when encryption is active. The client is responsible for selecting a session associated with one of the existing opens associated with that Lease Key, as per 3.2.5.19.2 Receiving a Lease Break Notification. The response is sent on the session that receives the acknowledgment, as documented in 3.3.5.22.2   Processing a Lease Acknowledgment.

A future MS-SMB2 update will clarify that Lease break notifications are not encrypted.

Regards,
Edgar


From: Edgar Olougouna 
Sent: Friday, August 24, 2012 12:06 AM
To: 'Stefan (metze) Metzmacher'
Cc: 'pfif at tridgell.net'; 'cifs-protocol at cifs.org'
Subject: [REG: 112082371227089] SMB3 encryption and Oplock/Lease break notifications

Metze,

Your observation is correct. For Oplock, we use the FileID - set in the Oplock break notification - and derive the SessionId which is set in the notification/acknowledgement. Per source code review, this should be encrypted as expected.

Lease break notifications don’t have a SessionId, so they won’t be signed. From what I am observing they should not be encrypted as well.  

A document bug has been opened to clarify these behaviors in MS-SMB2. I will confirm you when updates are available.

Regards,
Edgar

-----Original Message-----
From: Edgar Olougouna 
Sent: Thursday, August 23, 2012 3:06 PM
To: Stefan (metze) Metzmacher
Cc: pfif at tridgell.net; cifs-protocol at cifs.org
Subject: RE: [REG:112080864018345] SMB3 encryption over multiple requests

Metze,

In order to track document bugs properly, I will be following up on these new questions in two separate cases. I will start a new thread for each case:
112082370902333 SMB3 encryption of SESSION_SETUP (for reauth/or channel binding) and TREE_CONNECT
112082371227089 SMB3 encryption and Oplock/Lease break notifications

Thanks,
Edgar

-----Original Message-----
From: Stefan (metze) Metzmacher [mailto:metze at samba.org] 
Sent: Wednesday, August 22, 2012 9:19 AM
To: Edgar Olougouna
Cc: pfif at tridgell.net; cifs-protocol at cifs.org
Subject: Re: [REG:112080864018345] SMB3 encryption over multiple requests

Hi Edgar,

thanks for the answers, I have some more questions inline.

> What about async responses with STATUS_PENDING, are they also encrypted?
> 
> [Answer] 
> Yes. The exceptions that are not encrypted are SMB2 NEGOTIATE, SMB2 SESSION_SETUP or SMB2 TREE_CONNECT as documented in 3.2.4.1.8   Encrypting the Message, 3.3.4.1.4   Encrypting the Message.

Windows doesn't complain if the client encrypt SESSION_SETUP (for reauth/or channel bind) and TREE_CONNECTS.

> How does it work, when the last request in a compound chain goes async?
> 
> [Answer]
> There is no change of processing rules for the encryption due to the last request in a compounded chain going async. 
>  
> Are Oplock/Lease Break Notifications encrypted?
> 
> [Answer] Yes, see previous answer and references.

For Oplocks the server known the session from the file_id, but what session is used for leases?

To my understanding a lease key can be shared between sessions, is that correct?

metze