Subject: Re: [extensibility 3] details of negotiation and guidelines

From: Jeffrey Altman <[email-masked]>
Date: Mon, 17 Dec 2001 10:25:16 EST

Nico wrote:
> Yes, but, AS-REQ w/ PA-AS-REQ is to be used for PROBING KDC support for
> new Kerberos. If the KDC lacks that support then the outer AS-REQ has to
> be somewhat meaningful. At the very least there must be a cname/crealm
> and sname/srealm, which brings up the question of what to use for those
> when the intended names are non-ASCII.

RFC 1510 cannot safely be used for non-ASCII principal names in any
manner that provides interoperability.  If you are using RFC 1510
Kerberos, you must stick to ASCII names.

If there was a way to do otherwise, we wouldn't be having this
conversation.  

 Jeffrey Altman * Sr.Software Designer      C-Kermit 8.0 Beta available
 The Kermit Project @ Columbia University   includes Secure Telnet and FTP
 http://www.kermit-project.org/             using Kerberos, SRP, and 
 [email-masked]          OpenSSL.  SSH soon to follow.

---

From: Nicolas Williams <[email-masked]>
Date: Mon, 17 Dec 2001 13:14:53 -0500

> If there was a way to do otherwise, we wouldn't be having this

Right. But isn't a key to this extensibility proposal that you can
*probe* KDCs in AS exchanges to determine whether they support new
Kerberos or not?

Mind you, I don't think it's very likely that we'll see KDC probing when
the client needs the KDC to support new Kerberos and UTF-8... well, of
course, MS clients would because from their pov it's ok to use UTF-8
with old Kerberos.

This is a minor point anyways.

>  [email-masked]          OpenSSL.  SSH soon to follow.

Nico
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---

From: Sam Hartman <[email-masked]>
Date: 18 Dec 2001 10:30:01 -0500

>>>>> "Jeffrey" == Jeffrey Altman <[email-masked]> writes:

    Jeffrey> Nico wrote:
    >> Yes, but, AS-REQ w/ PA-AS-REQ is to be used for PROBING KDC
    >> support for new Kerberos. If the KDC lacks that support then
    >> the outer AS-REQ has to be somewhat meaningful. At the very
    >> least there must be a cname/crealm and sname/srealm, which
    >> brings up the question of what to use for those when the
    >> intended names are non-ASCII.

    Jeffrey> RFC 1510 cannot safely be used for non-ASCII principal
    Jeffrey> names in any manner that provides interoperability.  If
    Jeffrey> you are using RFC 1510 Kerberos, you must stick to ASCII
    Jeffrey> names.

I think the situation Nico is describing is as follows:

I have a principal name that includes non-ASCII characters.  I am an
implementation that never sent non-ASCII names with RFC 1510 so I
don't have clear behavior for what to do.  I don't care about RFC 1510 interop, I just want a KDC error not a timeout.  So I can't just send a new message from the start.  What name do I include in the AS-REQ?

Possible options include:

* Constant string 

* Same UTF8 I'm including in the  new message.