Re: [TLS] Rizzo claims implementation attach, should be interesting

Martin Rex <mrex@sap.com> Thu, 29 September 2011 14:10 UTC

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From: Martin Rex <mrex@sap.com>
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To: yngve@opera.com (Yngve N. Pettersen)
Date: Thu, 29 Sep 2011 16:13:03 +0200 (MEST)
In-Reply-To: <op.v2kozbgwkvaitl@lessa-ii.oslo.os> from "Yngve N. Pettersen" at Sep 29, 11 03:55:49 pm
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Cc: asteingruebl@paypal-inc.com, tls@ietf.org
Subject: Re: [TLS] Rizzo claims implementation attach, should be interesting
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Yngve N. Pettersen wrote:
> 
> Martin Rex wrote:
> 
> > Marsh Ray wrote:
> > >
> > > I believe there was a mitigation put in place by OpenSSL: sending an
> > > empty (just padding) message before each app data message.
> > >
> > > I read somewhere that this mitigation was off by default in OpenSSL
> > > because it [breaks] some software (an old MSIE IIRC).
> >
> > Why using a EMPTY (just padding) SSL record?  That looks like an
> > obvious untested border case.
> >
> > How about using an initial SSL record with one byte of real data
> > for SSLv3 and TLSv1.0 SSL with CBC cipher suites?
> 
> According to my testing, this breaks about as many websites,  
> unfortunately, approximately 0.15% of tested websites.

What exactly did you do?  did you fragment the client's
finished handshake message as well (which is the first protected
message on a TLS connnection) ?  As previously mentioned, I would
expect this to cause interop problems, whereas I have a slight
hope that fragmenting only application data might work.

-Martin