[Samba] Remote Desktop problem on samba 4.17.2

Tue Nov 1 02:20:06 UTC 2022

On Tue, 2022-11-01 at 12:31 +1300, Andrew Bartlett wrote:
> On Mon, 2022-10-31 at 17:53 +1300, Andrew Bartlett wrote:
> > On Fri, 2022-10-28 at 09:59 -0700, Matthew Schumacher via samba
> > wrote:
> > > On 10/27/22 4:36 PM, Matthew Schumacher via samba wrote:
> > > > I'm also having problems with RDP sessions not authenticating
> > > > against samba heimdal kdc.  What is odd is that the initial RDP
> > > > connection (network level connection) works fine and
> > > > authenticates me, but when I get to the desktop, I get access
> > > > denied and that my password is wrong as if I used a wrong
> > > > password at the console. If I put in the wrong password into
> > > > the initial rdp session for network level connection, it
> > > > immediately rejects me without letting me see the desktop.
> > > > Looking at wireshark under the covers, I suspect it's a
> > > > kerberos issue, however all of my hosts have dns settings of
> > > > samba domain controllers and my samba servers do appear to get
> > > > AD updates.
> > > > I was running 4.16.4 but now I'm on 4.17.2 with no change.
> > > > I wonder if something changed on the windows side.   I see
> > > > Jakob posted about a 22H2 update breaking this.  Anyone know
> > > > the specific fix and how to roll it back?
> > > 
> > > Looking at this more, the 22H2 issue doesn't seem to be the same
> > > issue I'm dealing with as Ralph and others mentioned that it goes
> > > away when they upgrade to latest (which I'm on), also I'm not
> > > seeing the KRB5KDC_ERR_TGT_REVOKED error.
> > > Here is what I found in regard to my issue:
> > > If I have a windows host with RDP authenticate against samba AD
> > > it starts an RDP session, but then rejects the password when we
> > > get the desktop.  Looking at the packet captures I see:
> > > This part looks identical other than keys between the captures
> > > that work against a real windows dc and captures that don't work
> > > against a SAMBA DC:
> > >  From client: as-req From server: KRB5KDC_ERR_PREAUTH_REQUIRED
> > > From client: as-req
> > > Now that we get to the as-rep we start to see differences:
> > >  From Windows: as-rep->ticket->enc-part->etype eTYPE-ARCFOUR-
> > > HMAC-MD5(23)    and    ap-rep->enc-part->etype eTYPE-AES256-CTS-
> > > HMAC-SHA1-96(18) From Samba: as-rep->ticket->enc-part-
> > > >etype eTYPE-AES256-CTS-HMAC-SHA1-96(18)   and    ap-rep->enc-
> > > part->etype eTYPE-AES256-CTS-HMAC-SHA1-96(18)
> > > Then we see the TGS-REQ and the client asks for a eTYPE-AES256-
> > > CTS-HMAC-SHA1-96(18) from the samba AD and eTYPE-ARCFOUR-HMAC-
> > > MD5(23) from the windows server otherwise identical.
> > > Now the TGS-REP
> > >  From Windows: tgs-rep->ticket->enc-part->etype eTYPE-ARCFOUR-
> > > HMAC-MD5(23)    and    tgs-rep->enc-part->etype eTYPE-ARCFOUR-
> > > HMAC-MD5(23) From Samba: tgs-rep->ticket->enc-part->etype eTYPE-
> > > AES256-CTS-HMAC-SHA1-96(18)   and    tgs-rep->enc-part->etype
> > > eTYPE-AES256-CTS-HMAC-SHA1-96(18)
> > > Basically, it appears that windows is using MD5 hashing and samba
> > > SHA1.
> > > A this point there aren't any further kerberos interactions from
> > > the client when authenticating to samba and the desktop shows
> > > password failed.  When using the windows AD server we get another
> > > TGS-REQ/TGS-REP for sname kRB5-NT-SRV-INST where it appears to
> > > authenticate for LDAP.
> > > So, where to go from here?  Create a Heimdal bug?  Create a Samba
> > > bug?  Not having RDP is really causing issues for me.
> > 
> > I'm actively looking into this, as that doesn't seem right.  What
> > is the value of msDS-SupportedEncryptionTypes for the server
> > account involved?
> > 
> > Are both DCs for this comparison in the same domain?
> > 
> > Andrew Bartlett
> 
> If you could create a Samba bug that would be great, and if you can
> send me privately that network trace I'll try and reproduce with our
> test harness. 
> I also need that msDS-SupportedEncryptionTypes value and any other
> context you are able to share, in particular the target server
> version.
> Andrew Bartlett

I'm going to need a lot more information about the Windows servers and
Windows DCs, in particular the versions, if they are in the same Samba
domain, and exactly which domain and forest functional level they are
in.

So far what I'm seeing is behaviour I would expect if the Windows
server was in Functional Level 2003, for example.

Did this work with Samba 4.15 and does it work again with 4.15 after
you apply the patch from 
https://bugzilla.samba.org/show_bug.cgi?id=15197 ?

Andrew Bartlett

-- 
Andrew Bartlett (he/him)       https://samba.org/~abartlet/
Samba Team Member (since 2001) https://samba.org
Samba Team Lead, Catalyst IT   https://catalyst.net.nz/services/samba

Samba Development and Support, Catalyst IT - Expert Open Source
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