Re: [kitten] Kerberos Service Discovery using DNS
Petr Spacek <pspacek@redhat.com> Thu, 02 April 2015 17:21 UTC
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Date: Thu, 02 Apr 2015 19:21:32 +0200
From: Petr Spacek <pspacek@redhat.com>
Organization: Red Hat
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To: Greg Hudson <ghudson@mit.edu>, Nathaniel McCallum <npmccallum@redhat.com>
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Subject: Re: [kitten] Kerberos Service Discovery using DNS
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On 24.3.2015 15:20, Greg Hudson wrote: > On 03/24/2015 08:36 AM, Nathaniel McCallum wrote: >> On Tue, 2015-03-24 at 09:35 +0100, Petr Spacek wrote: >>> It seems like a good idea to standardize _kerberos-master URI record >>> too (with >>> semantics equal to the one described on >>> http://web.mit.edu/Kerberos/krb5-1.12/doc/admin/realm_config.html). > >> I *think* this might be MIT specific. Maybe Greg can answer that? > > It does look like only MIT krb5 implements it. > > The semantics of _kerberos-master are "these addresses represent KDCs > (usually just one) which are more up to date than the other KDCs in the > realm, so retry with one of these if your first try fails for most > reasons." In some realms the master KDC isn't one of the regular KDCs, > in order to shed the majority of the load from the KDC which is also > running kadmind. > > These semantics are not generally needed for a realm with fast > replication (iprop with low polling delay, LDAP, etc.), but there are > enough realms with slow replication that we're not about to discard > those semantics. > > It might be good if master KDC entries could be obtained in the same DNS > lookup as regular KDC entries, but none of the ways I can think of to do > it are particularly elegant. We would need to be able to annotate each > URI with "this is also a master KDC" or "this is only a master KDC". > Shoving that tri-state into each URI scheme wouldn't be very elegant; > designating magic priority values for the URI record would be a layering > violation. It's not really a big deal if a second DNS lookup is needed > for the fallback. > > I have no strong opinion on whether the discovery standard needs to talk > about this. MIT krb5 can always continue to implement it as a > non-standardized feature, using the same lookup behavior as the > _kerberos URI record but with the label changed to _kerberos-master. IMHO: I would not optimize for fallback when it means obfuscating the original idea. I.e. a separate DNS name like _kerberos_master with URIs of masters sounds fine to me. Also, I do not see a reason not to standardize it because it is deadly simple/cheap and allows Heimdal and others to be interoperable if they decide to support this feature in future. -- Petr^2 Spacek
- Re: [kitten] Kerberos Service Discovery using DNS Petr Spacek
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Greg Hudson
- Re: [kitten] Kerberos Service Discovery using DNS Petr Spacek
- [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Greg Hudson
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Simo Sorce
- Re: [kitten] Kerberos Service Discovery using DNS Nico Williams
- Re: [kitten] Kerberos Service Discovery using DNS Rick van Rein
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Rick van Rein
- Re: [kitten] Kerberos Service Discovery using DNS Greg Hudson
- Re: [kitten] Kerberos Service Discovery using DNS Rick van Rein
- Re: [kitten] Kerberos Service Discovery using DNS Viktor Dukhovni
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Benjamin Kaduk
- Re: [kitten] Kerberos Service Discovery using DNS Benjamin Kaduk
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Greg Hudson
- Re: [kitten] Kerberos Service Discovery using DNS Benjamin Kaduk
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Nathaniel McCallum
- Re: [kitten] Kerberos Service Discovery using DNS Jeffrey Altman