tsig-gss dynamic DNS updates

tridge at samba.org tridge at samba.org
Sun Oct 13 07:41:00 GMT 2002

Those of you with win2000 based DNS servers might be interested to
know that I have just successfully sent a TSIG-GSS dynamic DNS update
to a win2000 server from a Linux box, using a kerberos ticket from MIT
kerberos. This is an important piece of the netbiosless support that
is being added to Samba.

Thus far I have only sent successful updates using des-cbc-crc
tickets. I would prefer to be able to use hmac-md5 tickets as that is
what win2000 uses, but I haven't been able to get that to work
yet. I'm guessing there may be a bug in the MIT hmac-md5
implementation, or at least a difference between the MIT and Microsoft
implementations. The MIT library can certainly generate and use
hmac-md5 tickets for other things (we use them in Samba ADS support
all the time) so I suspect the problem is in using them for signing
(like in calls to gss_get_mic()).

My current test implementation is a mish-mash of perl and C, using the
Net::DNS perl module for DNS packet construction and C to interface to
the MIT kerberos GSSAPI library. I'm still thinking about how I will
put this into a more palatable form, the choices seem to be to either
cleanup my perl code a bit or try to modify the bind-9 nsupdate
utility to handle the necessary TKEY requests. I originally started
on this project with the aim of updating the bind-9 code but I've
found it fairly hard to work out how to extend it, which is why I
switched to the Net::DNS module.

If anyone out there knows the bind-9 code really well and wants to
help me produce a patch to that then please let me know.

Cheers, Tridge

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