[linux-cifs-client] Linux CIFS NTLMSSP mount failing against win2k8

Jeff Layton jlayton at samba.org
Wed Apr 21 14:19:50 MDT 2010

On Wed, 21 Apr 2010 09:29:33 -0500
Shirish Pargaonkar <shirishpargaonkar at gmail.com> wrote:

> On Sat, Apr 17, 2010 at 5:29 AM, Jeff Layton <jlayton at samba.org> wrote:
> > On Sat, 17 Apr 2010 15:58:23 +1000
> > Andrew Bartlett <abartlet at samba.org> wrote:
> >
> >> On Fri, 2010-04-16 at 22:44 -0400, Jeff Layton wrote:
> >> >
> >> > - then I read the spec more carefully. The problem is that the existing
> >> >   (aka NTLM2 -- not to be confused with NTLMv2).
> >> >
> >> > Without that, the server expects signatures done using rc4, but cifs
> >> > universally uses md5 signatures.
> >>
> >> This isn't the case.  SMB signing is always MD5.  NTLM2 simply changes
> >> the 'effective' challenge and the session key, by providing a value in
> >> the 'LM hash' to include with the Negotiate-provided challenge.
> >>
> >
> > Interesting. That seems to be contradictory to what the MS-NLMP
> > document says. If you have a look at section, you'll see that
> > the algorithm for computing the signature does not use md5. However if
> > you negotiate extended session security (aka NTLM2) or use NTLMv2, then
> > you're supposed to use md5. Perhaps we should bring that up on the
> > dochelp list?
> >
> > In any case, I think the right solution is just to have CIFS always use
> > extended session security and NTLMv2.
> If by extended session security you mean NTLM2, are not NTLMv2 and
> NTLM2 both authentication mechanisms and orthogonal to each other?

I'd probably call them "mutually exclusive" rather than "orthogonal".
The NTLM2 flag is always supposed to be set if you're using NTLMv2, but
its presence doesn't mean you're using NTLMv2.

> In which case, I think cifs/smb2 clients should at least make NTLMv2 auth mech
> within NTLMSSP (Raw or SPNEGO) work against a Windows server
> like Windows7/Vista/2008 server, with and without SMB signing.

Agreed, though we need to have some sort of way to automatically fall
back to NTLM2 if that doesn't work against the server.

> NTLMv.2 in NTLMSSP will work with LMCompatibililtyLevel settings of
> 0 through 5.  I am not whether NTLM2 will work with with settings (eg. 4, 5)
> and I am not sure whether NTLM2 needs/works_with SMB signing i.e.
> how to calculate session key, mac key, signature etc.

I'll take your word for it. I've walked away from all of this for the
time being. I will say however that if you're doing some work for this
for SMB2, then please consider doing this in a fashion that will allow
the code to be shared with CIFS as well.

Jeff Layton <jlayton at samba.org>

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