[Samba] 'LDAP_PROTOCOL_ERROR' when NTLMSSP_NEGOTIATE bind request

[Peter]

Which version of EMS are you on? I have 7.2 and 7.4 in my lab.

On Fri, Oct 24, 2025 at 5:43 AM Nicolas Martinussen via samba <
samba at lists.samba.org> wrote:

> > > I've found a way to reproduce the issue I have with a small C# code
> > > executed on Windows. It gets me almost the same packets when I do a
> > > capture, I also get the 'LDAP_PROTOCOL_ERROR' in the Samba logs, and
> > > when I try it against a Windows DC, it works.
> > >
> > > Here is the code:
> > >
> > > using System.DirectoryServices.Protocols;
> > > using System.Net;
> > >
> > > class Program
> > > {
> > >     static void Main()
> > >     {
> > >         string ldapServer = "dc-01.ad.mydomain.com";
> > >
> > >         LdapConnection ldap = new LdapConnection(ldapServer);
> > >         ldap.AuthType = AuthType.Ntlm;
> > >         ldap.Credential = new NetworkCredential("ldap", "PASSWORD",
> > > "MYDOMAIN");
> > >
> > >         ldap.Bind();
> > >     }
> > > }
> > >
> > > It seems like AuthType.Ntlm isn't supported by the Samba code. When I
> > > try the same code with AuthType.Basic, in that case, it works (I get
> > > the "Strong authentication is required for this operation.", but
> > > that's normal as I use LDAP and not LDAPS).
> > >
> >
> > I am also fairly certain it is supported, but I am also running out of
> > ideas. My last idea is, you are using 'ldap at ad.mydomain.com' for the
> > username, what if it expects the samaccountname ? try it with just
> > 'ldap' (which I presume is an AD username).
> >
> > Rowland
>
> Yes, 'ldap' is in fact the username I try. I've already tried
> 'CN=LDAP,CN=Users,CN=AD,CN=MYDOMAIN,CN=com', 'ldap at ad.mydomain.com',
> 'MYDOMAIN\ldap' and just 'ldap'.
>
> When I check the packet trace, I don't even see the username in the packet
> that result in a TCP RESET from the DC. The username is sent later when I
> check the same traffic with a Windows DC. So, what I'm guessing is that for
> some reason, this specific bind packet isn't correctly recognized by Samba.
> I'm willing to try to do a code debugging to see exactly where there is an
> issue, but I didn't find any info about how to debug the Samba code in the
> wiki and I have never really used GDB, so I have no idea where to start.
>
> Nicolas
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