Re: [TLS] Warning alert before TLS 1.3 ServerHello

Martin Thomson <martin.thomson@gmail.com> Thu, 10 May 2018 06:05 UTC

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From: Martin Thomson <martin.thomson@gmail.com>
Date: Thu, 10 May 2018 06:05:18 +0000
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Subject: Re: [TLS] Warning alert before TLS 1.3 ServerHello
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On Thu, May 10, 2018 at 1:48 PM Viktor Dukhovni <ietf-dane@dukhovni.org>
wrote:
> I may be misreading the code, but it sure looks like the alert is only
> sent if the application callback for the server name extension  asks
> OpenSSL to do that.  The application can just decline the extension
> and let the handshake continue with a default certificate...  Is
> the surprise that the alert is sent, or that it is a warning, or
> something else?

It's risking a failed connection.  Though perhaps not that much more than
providing the client with a certificate it might not like.