Re: [SECMECH] Framework Bindings Vs. Mechanism Bridges

Nicolas Williams <Nicolas.Williams@sun.com> Fri, 19 August 2005 21:03 UTC

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Date: Fri, 19 Aug 2005 16:03:08 -0500
From: Nicolas Williams <Nicolas.Williams@sun.com>
To: Charles Clancy <clancy@cs.umd.edu>
Subject: Re: [SECMECH] Framework Bindings Vs. Mechanism Bridges
Message-ID: <20050819210308.GI6659@binky.Central.Sun.COM>
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On Fri, Aug 19, 2005 at 02:52:22PM -0400, Charles Clancy wrote:
> On Fri, 19 Aug 2005, Salowey, Joe wrote:
> 
> >>From: Nicolas Williams [mailto:Nicolas.Williams@sun.com]
> >>
> >>On Wed, Aug 17, 2005 at 06:14:07PM -0400, Charles Clancy wrote:
> >>>
> >>>IMHO, Framework Bindings sounds like the way to go.  It gives you more 
> >>>control over which mechanisms are used in which frameworks.  Each 
> >>>framework has a different threat model, and not all mechanisms from 
> >>>one framework may be good in another.  For example, using basic krb5 
> >>>in 802.11i-EAP is a bad idea because of dictionary attacks.
> >>
> >>Sure, but you could always do 
> >>krb5-over-TLS-with-cryptographic-bindings.
> >>
> >
> >[Joe] How would this be instantiated?  Currently EAP does not run over a 
> >specific security layer.  There are EAP mechanisms that provide a secure 
> >tunnel for running other mechanisms.  Would an EAP to GSS bridge have to 
> >be a tunneling method?
> 
> Whatever happened to EAP-GSS?

Dunno, but as I recall some of the KITTEN WG work is, in part, aimed at
making EAP-GSS possible, specifically the GSS_Pseudo_random() extension.

> http://www.drizzle.com/~aboba/IEEE/draft-aboba-pppext-eapgss-12.txt
> 
> "krb5->GSS-API->EAP-GSS->EAP-TTLS->EAP" would work.  Of course, the length 
> of that string should be a motivator for bindings over bridges.

Yes, but replace 'krb5' with 'IAKERB' or soemthing like it.

Using slightly different (clearer?) notation, w/o PKINIT we have these
options (and maybe more):

EAP{EAP-TLS{EAP-GSS{GSS-API{GSS-IAKERB}}}}

or

EAP{EAP-GSS{GSS-API{GSS-TUNNEL{GSS-TLS,GSS-IAKERB}}}}

Where "GSS-IAKERB" is a GSS-API mechanism that does Kerberos V KDC
exchange proxying as necessary in order to establish service tickets for
Kerberos AP exchanges.  And where GSS-API channel bindings are used in
both cases to bind the Kerberos V AP exchanges to the TLS (or whatever)
tunnel.

Of course, with PKINIT no tunnelling would be necessary:

EAP{EAP-GSS{GSS-API{GSS-IAKERB}}}

Nico
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