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Re: [TLS] draft-rescorla-tls-renegotiate and MITM resistance

Martin Rex <mrex@sap.com> Mon, 09 November 2009 20:07 UTC

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From: Martin Rex <mrex@sap.com>
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To: david-sarah@jacaranda.org
Date: Mon, 09 Nov 2009 21:07:58 +0100
In-Reply-To: <4AF86F8A.7090505@jacaranda.org> from "David-Sarah Hopwood" at Nov 9, 9 07:37:46 pm
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Cc: tls@ietf.org
Subject: Re: [TLS] draft-rescorla-tls-renegotiate and MITM resistance
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David-Sarah Hopwood wrote:
> 
> Martin Rex wrote:
> > There may be SSLv3 servers out there that choke on extension data
> > in the ClientHello.  But that doesn't mean that one could not
> > upgrade SSLv3 servers to support TLS extensions.  The more interesting
> > question is IMHO -- which TLS clients will choke when an SSLv3 server
> > returns a ServerHello extension?  spec-wise, a ServerHello extension
> > is as unusual to SSLv3 as it is to TLSv1.0.
> 
> Why would that situation arise? For that to happen, an SSL server
> library would have to be upgraded to support extensions but not to
> support TLS. Are there any SSL-only libraries being actively
> maintained?

Yes, there are.

But the issues do also affect TLS-capable servers and clients that
talk to peers which are limited to SSLv3 only (through either
configuration or implementation constraints).

-Martin

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