[Pfif] [cifs-protocol] Clarify AEAD behaviour for GSSAPIwith AES

[Hongwei Sun]

Stefan,

   I like to give you an update on the issues and suggestion in your e-mail.

>It would be nice if this example would use ec != 0, as that was exactly
>not match RFC 4121 and the reason our (heimdal) krb5 code was not able to
>handle network traffix from windows.

   We are in the process of incorporating  your suggestion into the diagram.  It is in the review stage of document update.

>You should unify the naming of the resulting overhead, in the diagram
>you use 'checksum' and in the test you use 'signature', maybe 'token'
>would be the better word here, as 'checksum' is a non unique in the diagram.

   Thanks for pointing out the inconsistency.  We will fix it in the update we are working on.

>An example with arcfour-hmac-md5 would also be very useful,
>as there the pseudo ASN.1 wrapping arround the token is very tricky.
>As it's only arround the 'token' instead of 'token' + 'message' +
>'padding' as it is for the standard GSS_Wrap function.

   I filed a formal request for the documentation team to consider your suggestion.  I will let you know once I hear back from them.

>Also it would be nice to have a specific example how the RPC layer
>calls GSS_WrapEx.

    There is an  example in 4.1 [MS-RPCE] that describes how various GSS-API calls, including GSS_WrapEx and GSS_unWrapEx, are called in  a secure and connection-oriented RPC call using Kerberos as security provider.  Please review the section and let us know if it is what you are looking for.

>It would also be very helpfull to know how the mapping to the SSPI
>function parameters works.

   MSDN has all the information about SSPI , including EncryptMessage() and DecryptMessage(), on  http://msdn.microsoft.com/en-us/library/aa375378(VS.85).aspx    There is also a MSDN article for SSPI Interoperability with GssAPI (http://msdn.microsoft.com/en-us/library/ms995352.aspx).  This document is about how the protocol works and the description of SSPI should not be a normative reference for the protocol documentation.

Thanks !

Hongwei

-----Original Message-----
From: Stefan (metze) Metzmacher [mailto:metze at samba.org]
Sent: Sunday, October 19, 2008 10:03 AM
To: Hongwei Sun
Cc: Andrew Bartlett; pfif at tridgell.net; cifs-protocol at samba.org
Subject: Re: [Pfif] [cifs-protocol] Clarify AEAD behaviour for GSSAPIwith AES

Hi Hongwei,

>   We finished adding an example for GSS_WrapEx with
> AES128-CTS-HMAC-SHA1-96 in [MS-KILE]. The attached PDF document is the
> newly added section(4.3) of the [MS-KILE] document.
>
>   We really appreciate your suggestion.   Please let us know if you have
> further questions regarding this subject.

It would be nice if this example would use ec != 0, as that was exactly
not match RFC 4121 and the reason our (heimdal) krb5 code was not able to
handle network traffix from windows.

You should unify the naming of the resulting overhead, in the diagramm
you use 'checksum' and in the test you use 'signature', maybe 'token'
would be the better word here, as 'checksum' is a non unique in the diagramm.

An example with arcfour-hmac-md5 would also be very useful,
as there the pseudo ASN.1 wrapping arround the token is very tricky.
As it's only arround the 'token' instead of 'token' + 'message' +
'padding' as it is for the standard GSS_Wrap function.

Also it would be nice to have a specific example how the RPC layer
calls GSS_WrapEx.

It would also be very helpfull to know how the mapping to the SSPI
function parameters works.

metze

>
> ----------------------------------------------------------
> Hongwei  Sun - Sr. Support Escalation Engineer
> DSC Protocol  Team, Microsoft
> hongweis at microsoft.com
> Tel:  469-7757027 x 57027
> -----------------------------------------------------------
>
>
>
> -----Original Message-----
> From: Andrew Bartlett [mailto:abartlet at samba.org]
> Sent: Wednesday, August 27, 2008 6:24 AM
> To: Hongwei Sun
> Cc: pfif at tridgell.net; cifs-protocol at samba.org
> Subject: RE: [Pfif] [cifs-protocol] Clarify AEAD behaviour for GSSAPI with
> AES
>
> On Tue, 2008-08-26 at 08:50 -0700, Hongwei Sun wrote:
>> Andrew,
>>
>> In this case, you provided a diagram for us to add to the  document and
>> metze added some comments.  Thanks for your contribution to our
>> documentation and continued feedback.
>>
>> The product team reviewed the diagram and comments provided.  We believe
>> that the diagrams imply interaction between elements and without
>> detailed notes they are subject to multiple interpretation and hence
>> confusion.    We believe that as a matter of providing deterministic
>> documentation, we would prefer to provide specific examples.
>>
>> We'll be happy to get your  feedback on creating examples and  send them
>> for your review  once they are ready.
>
> A visual description of how the RRC interacts with the AEAD behaviour and
> the subsequent placement of the trailer in the header will be critical.
>
> Andrew Bartlett
>
> --
> Andrew Bartlett
> http://samba.org/~abartlet/
> Authentication Developer, Samba Team           http://samba.org
> Samba Developer, Red Hat Inc.
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