Re: [TLS] ALPN concerns

Dr Stephen Henson <lists@drh-consultancy.co.uk> Wed, 06 November 2013 20:56 UTC

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Date: Wed, 06 Nov 2013 20:56:12 +0000
From: Dr Stephen Henson <lists@drh-consultancy.co.uk>
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Subject: Re: [TLS] ALPN concerns
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On 06/11/2013 18:12, Dr Stephen Henson wrote:
> On 06/11/2013 18:03, Adam Langley wrote:
>> On Wed, Nov 6, 2013 at 1:00 PM, Xiaoyong Wu <X.Wu@f5.com> wrote:
>>> As I am explaining this in detail, I would say that another work around on this would be making a client hello that exceeds 512 in length.
>>
>> ^^^ Holy crap. I wish I had known that sooner. That might solve the issue.
>>
> 
> Just did a quick test with OpenSSL on a couple of known "hang" machines. Seems
> to work.
> 

I added this to the OpenSSL master branch in case anyone wants to test it.

If enabled it uses a dummy extension[1] to pad the ClientHello with enough
zeroes to make it long enough.

Steve.
1. Provisional name Workaround TLS Filler aka WTF ;-)
-- 
Dr Stephen N. Henson.
Core developer of the   OpenSSL project: http://www.openssl.org/
Freelance consultant see: http://www.drh-consultancy.co.uk/
Email: shenson@drh-consultancy.co.uk, PGP key: via homepage.