Bug 10708 - ntlm_auth --helper-protocol=gss-spnego does not fall back to NTLMSSP
Summary: ntlm_auth --helper-protocol=gss-spnego does not fall back to NTLMSSP
Alias: None
Product: Samba 4.1 and newer
Classification: Unclassified
Component: Winbind (show other bugs)
Version: 4.1.9
Hardware: All All
: P5 normal (vote)
Target Milestone: ---
Assignee: Samba QA Contact
QA Contact: Samba QA Contact
Depends on:
Reported: 2014-07-11 12:31 UTC by David Woodhouse
Modified: 2017-01-03 02:58 UTC (History)
2 users (show)

See Also:


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Description David Woodhouse 2014-07-11 12:31:13 UTC
I'm using squid configured thus:

auth_param negotiate program /usr/bin/ntlm_auth --helper-protocol=gss-spnego 

Due to reverse DNS issues, a client sometimes presents a Kerberos ticket for the *wrong* SPN. When this happens, I see:

write(2, "GENSEC login failed: NT_STATUS_LOGON_FAILURE\n", 45) = 45
write(1, "NA * NT_STATUS_LOGON_FAILURE\n", 29) = 29

Surely it shouldn't just abort? I would expect it to give me a SPNEGO response telling me to try NTLMSSP next?

Yes, my client's negTokenInit *did* offer that:

        GSS-API Generic Security Service Application Program Interface
            OID: (SPNEGO - Simple Protected Negotiation)
            Simple Protected Negotiation
                    mechTypes: 5 items
                        MechType: 1.2.840.113554.1.2.2 (KRB5 - Kerberos 5)
                        MechType: (iso.
                        MechType: 1.2.840.48018.1.2.2 (MS KRB5 - Microsoft Kerberos 5)
                        MechType: (iso.
                        MechType: (NTLMSSP - Microsoft NTLM Security Support Provider)
                    mechToken: 60820e3e06092a864886f71201020201006e820e2d30820e...
                    krb5_blob: 60820e3e06092a864886f71201020201006e820e2d30820e...
Comment 1 Andrew Bartlett 2017-01-03 02:58:14 UTC
We don't check the service principal name, we just compare it with what we can find in a keytab.  If we can't decrypt it with anything in our keytab, we report logon failure.  

It isn't for the server to offer a downgrade in this situation, as I understand it.  It would be a different matter if the KDC hadn't issued a ticket, as then the client could choose to downgrade.