Subject: Re: [kitten] User-to-user Kerberos in GSS-API

From: Rick van Rein <[email-masked]>
Date: Fri, 02 Nov 2018 11:12:03 +0100

Hi,

>> 1. The service may declare its realm; in other Kerberos
>> protocols that is considered to be a no-go area.
> 
> I don't follow.

Usually, when a service can declare a realm, it is given an opportunity
to sidetrack credentials to that choice of realm.  Other Kerberos
applications choose to infer the realm on the client or in his KDC,
which can be a nuisance, but a secure nuisance.

> StartTLS is a feature of protocols like SMTP, SUBMIT, IMAP, and so on --
> generally SASL apps.  (HTTP has a StartTLS that is not implemented and
> nobody uses.)  Where would you use StartGSS?

Not completely sure yet, I want to experiment with it.  Possible places
could be (1) as an alternative to StartTLS and (2) as an end-to-end
facility within a client-server connection.

I like the model of SASL-within-TLS, but only from the perspective of
authentication; it leaves things to be desired concerning end-to-end
encryption, which TLS tries very hard to avoid.

I'm also wondering what Quantum Crypto would change; for instance,
OpenSSH looses its secure status but could benefit from mixing the
Kerberos session key with the (EC)DH shared key.  (That's what we did in
TLS-KDH too.)

-Rick