s3 member server to s4 kerberos trouble

Andrew Bartlett abartlet at samba.org
Sat Jun 12 21:21:23 MDT 2010

On Sat, 2010-06-12 at 00:02 +0400, Matthieu Patou wrote:
> Hello Lukaz,
> To my mind according to your log the pb is that w7 present an AES 
> encrypted ticket, and s3, didn't support for this version, AES.
> In order for s4 to provide AES ticket, you should have raised to level 
> 2008 your domain, because by default we do provision with a 2003 
> functional level.
> Is it the case ?
> Even win this case we should be able to sort out differences in capacity.
> If I trust your log it _seems_ that your s3 pretend to support encoding 
> that it in fact didn't support :
> ipv4: for 
> Kerberos: No preauth found, returning PREAUTH-REQUIRED -- 
> ipv4: for 
> Kerberos: Client sent patypes: encrypted-timestamp
> Kerberos: Looking for PKINIT pa-data -- ORINOCO$@STUDENT.EECS.QMUL.AC.UK
> Kerberos: Looking for ENC-TS pa-data -- ORINOCO$@STUDENT.EECS.QMUL.AC.UK
> Kerberos: ENC-TS Pre-authentication succeeded -- 
> ORINOCO$@STUDENT.EECS.QMUL.AC.UK using aes256-cts-hmac-sha1-96
> Kerberos: AS-REQ authtime: 2010-06-11T09:59:30 starttime: unset endtime: 
> 2010-06-12T09:59:33 renew till: unset
> Kerberos: Client supported enctypes: aes256-cts-hmac-sha1-96, 
> arcfour-hmac-md5, des3-cbc-sha1, des-cbc-crc, des-cbc-md5, using 
> aes256-cts-hmac-sha1-96/aes256-cts-hmac-sha1-96
> Can you confirm that ORINOCO is your s3 server and that is 
> its ip.
> Andrew: if it is so I have the impression that something wrong: either 
> from s4 side because it thinks that the client support that it is not 
> announcing as supported, either it's s3 which announce encoding that it 
> fact it didn't support.
> In any case even in  if s3 announce wrong encoding when requesting 
> ticket

Samba3 isn't able to influence this (nor should it, for security and man
in the middle attack reasons).  It just finds out at the end that it
can't decrypt. 

> , we should use msDS-SupportedEncryptionTypes when requested for a 
> ticket for a given principal (ie. cifs/server at REALM) to decide in which 
> encoding we return the ticket to the requester so that it can be 
> understood by requester and and requested principal. 

Yes.  The requester is handled by the KDC already, but the requested
principal is what needs work. 

> Looking at the code 
> I didn't saw much lookup to this attribute so I wonder how do we decide 
> which encoding the requested principal support.

Correct, we need to use msDS-SupportedEncryptionTypes in kdc/db-glue.c
near where we look at UF_USE_DES_KEY_ONLY.  

The trickier part is that we need to have Samba4's domain join call the
netlogon 'GetDomainInfo' call to set it's use of the full set of
encryption types (and the DNS name). 

Attached is my proposed solution. 

Andrew Bartlett

Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org
Samba Developer, Cisco Inc.

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