[TLS] Empty extensions don't go last

Martin Thomson <martin.thomson@gmail.com> Thu, 24 March 2016 05:30 UTC

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Date: Thu, 24 Mar 2016 16:30:29 +1100
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From: Martin Thomson <martin.thomson@gmail.com>
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Subject: [TLS] Empty extensions don't go last
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(This is probably already known to a bunch of people, but it's
probably a good idea to put out there.)

When deploying EMS, we recently discovered, with the help of our
friends at Google (who discovered this long before that) a quirk in
some implementations.

Short story:  Don't place an empty extension at the end of your
ClientHello.  You will find that a small number of servers choke.