Re: [TLS] Asking the browser for a different certificate

Martin Rex <mrex@sap.com> Sat, 27 March 2010 01:14 UTC

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From: Martin Rex <mrex@sap.com>
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To: pgut001@cs.auckland.ac.nz (Peter Gutmann)
Date: Sat, 27 Mar 2010 02:14:10 +0100 (MET)
In-Reply-To: <E1NuIsa-0003Nf-HC@wintermute02.cs.auckland.ac.nz> from "Peter Gutmann" at Mar 24, 10 06:11:44 pm
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Cc: tls@ietf.org
Subject: Re: [TLS] Asking the browser for a different certificate
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Peter Gutmann wrote:
> 
> Martin Rex <mrex@sap.com> writes:
> > 
> >IMHO there are a number of defects in the TLS protocol related to client
> >certificate authentication, and some of them should probably be fixed at the
> >TLS protocol level.  But fixes at the TLS protocol level may take a huge
> >amount of time before they become a useful feature in the installed base...
> 
> Yeah, because this is going to affect the vast numbers of users of
> SSL client certs :-).

The non-users of SSL client certs are much more affected.

Currently, if you enable a Web Server to request a client cert
in the initial handshake, the users without SSL client cert suffer
the worst user experience of all.  Would the browser be able to
tell the server in a ClientHelloExtension "Don't bother sending
me a CertificateRequest, because I don't have one", then
the server could skip the CertificateRequest message if the
application/configuration allows the handshake to complete without
client certificate.

> 
> >[Issues]
> 
> Couldn't a lof of this be handled via TLS extensions?

Sure.  Preferably with one single TLS extension that carries all the
necessary signals.


-Martin