Re: [SPKM] Re: [TLS] DTLS and GSS-API

On Sun, Nov 05, 2006 at 02:41:53PM -0500, Sam Hartman wrote:
>     Martin> With TLS, on the other hand, each of the communication
>     Martin> peers may request a renegotiation of context parameters at
>     Martin> (almost) any time during the communication.
> 
> I talked to Eric about this in another context.  He claimed that as a
> practical matter it does not work if animplementation does a new
> handshake without the cooperation of the upper-layer application.  You
> are correct though that a DTLS GSS-API mechanism could only be
> specified on the standards track if this issue were dealt with in some
> manner that preserved the GSS-API model.

I would expect that a GSS-TLS mechanism wouldn't renegotiate anything
after initial security context establishment.  If there is a hard need
to (e.g., for re-keying), then expire the security context[*].

Alternatively, one of the things we've discussed is using TLS for
security context establishment, but the Kerberos V mechanism's
per-message tokens for per-message tokens, using the TLS PRF and master
secret to derive keys for them.  That would hand wave TLS re-negotiation
issues away as well, and would deal with re-key crypto needs no better
nor worse than the Kerberos V mechanisms.

IOW, this is not an issue (and if it is, then it's an issue for GSS-API
applications, and, maybe, for the GSS-APIv3 and v3 apps).

[*]  GSS apps have to be prepared to deal with this; the SASL GSS
     bridges, admittedly, don't.

Nico
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