[cifs-protocol] How to determine if an account should use AES?

Matthieu Patou mat at matws.net
Mon Aug 24 16:14:13 MDT 2009

Hello Sebastian,

I'm coming back to you on this subject.
Last week I made tests with one of the newsest version of samba4 which 
tries to pretend to be have a windows 2008 forest/domain and dc 
compatibility level.

And I didn't noticed any request from a windows 2008 acting as a client 
of my S4 domain.

It raise a few possibilities but two are most probable:

1) S4 is not behaving like windows 2008 enough so that client thinks 
that it is not a real windows 2008 and so it don't send this attibute.
2) This attribute is not sent by the client it's just the server that 
based on some algorithm (ie. if os.version >=6.0 and os.name contains 
"Windows" then set msDS-SupportedEncryptionType)

Can you indicate us if one of the two possibilities are the right one. 
If not please indicate the correct one.
If yes please do not forget for the case 1 to indicate what exactly 
trigger the sending of this attribute (or what block the transmission)
or if it's case 2 then give us the good algorithm.

In any case I can only reiterate the request of Andrew about pcap 
formatted  network  trace with packets which are significant (ie those 
holding this attribute).

Best regards.
Matthieu Patou.

On 08/20/2009 02:16 AM, Andrew Bartlett wrote:
> On Wed, 2009-08-19 at 09:41 -0700, Sebastian Canevari wrote:
>> Hi Andrew,
>> The msDS-SupportedEncryptionTypes attribute is populated at object creation time by the subjects that support the property.
> So it is modified over LDAP by the Windows Vista (for example) domain
> member?
>> It is also updated whenever there's a change on the object's
>> configuration that require an update of the property.
> So if the domain member upgrades, it is expected to reach out and update
> this property using LDAP?
> Are there any ACL considerations to be aware of here?  Are there any
> other restrictions on the values clients might populate here?
>> Meaning that when a subject changes the type of encryption it
>> supports, it modifies this attribute to reflect the change.
> Any chance you can provide an annotated (ie, with a separate document
> mentioning frame numbers) PCAP-formatted example network trace and
> documentation references to support this?  I would really like to pin
> this down firmly before the next alpha, now that I've turned on the
> Windows 2008 functional level and therefore AES encryption in our DC.
> Thanks,
> Andrew Bartlett
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