Re: [kitten] The Hashed-Token SASL Mechanism (SASL-HT)

[Simo Sorce <[e-mail]>]

On Sun, 2017-10-15 at 21:51 -0500, Benjamin Kaduk wrote:
> On Fri, Sep 29, 2017 at 11:08:10AM +0200, Florian Schmaus wrote:
> > I would like to note the existence of draft-schmaus-kitten-sasl-ht-
> > 01:
> > 
> > https://tools.ietf.org/html/draft-schmaus-kitten-sasl-ht-01
> 
> Thanks, I just got a chance to look it over.
> 
> [...]
> 
> > Thus we initially authenticate an XMPP session using a strong
> > mechanism
> > like SCRAM, but at resumption-time we want a single round trip
> > mechanism. The basic idea of such a mechanism is that the client
> > requests a short-lived, exclusively ephemeral token after being
> > authenticated, which can be used to authenticate the resumption in
> > an
> > efficient manner.
> 
> [...]
> > The SASL HT-* mechanism outlined is attempting to provide a
> > reasonably
> > secure authentication based around a token obtained over the
> > application
> > protocol, in a single round-trip. This single-round-trip is a key
> > requirement. The proposal uses a single-use token as a shared
> > secret,
> > provides channel binding and mutual authentication.
> 
> There does seem to be some value in having a fast "session
> resumption" SASL mechanism to avoid repeated reauthentication (though
> presumably there should be some guidance to periodically require a
> full authentication; various flows elsewhere do this on a month
> timescale, roughly).
> It's a little unfortunate that this ends up requiring TLS for
> confidentiality (as there is some desire to have standalone
> mechanisms), but that seems to be an acceptable tradeoff for this
> sort of application.

I think this draft has many goals in common with this one:
https://tools.ietf.org/html/draft-wibrown-ldapssotoken-02

I wonder if we can end up having a solution that will work well to
cover it all ?

The main issue here would be the requirement to bind it to TLS as LDAP
(as well as other connection-oriented protocols) can use other means to
encrypt the channel (namely GSSAPI, although GSSAPI doe not have a
session resumption mechanism ...).

Simo.

-- 
Simo Sorce
Sr. Principal Software Engineer
Red Hat, Inc