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Re: [Acme] Alternative proposal for fixing TLS-SNI / revisiting HTTPS-01 authorization

Ilari Liusvaara <ilariliusvaara@welho.com> Fri, 12 January 2018 16:46 UTC

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Date: Fri, 12 Jan 2018 18:46:39 +0200
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: "Matthew D. Hardeman" <mhardeman@ipifony.com>
Cc: "Gerd v. Egidy" <gerd.von.egidy@intra2net.com>, acme@ietf.org
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Subject: Re: [Acme] Alternative proposal for fixing TLS-SNI / revisiting HTTPS-01 authorization
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On Fri, Jan 12, 2018 at 10:28:31AM -0600, Matthew D. Hardeman wrote:
> 
> > On Jan 12, 2018, at 10:20 AM, Gerd v. Egidy <gerd.von.egidy@intra2net.com> wrote:
> > 
> I did want to say that if an acceptable mechanism is found in this
> manner, it does help with some but not all in-band TLS validation
> mechanisms.  It works for web server cases.  It does not fully
> replace the mechanisms of the TLS-SNI sort because it would not work
> for other protocols running over TLS (like SMTP/TLS).  The TLS-SNI
> mechanisms do facilitate that.  Still, if the risks are otherwise
> acceptable, such a challenge mechanism might be a path of least
> resistance for those impacted by the TLS-SNI-01 deprecation.

I had actually written code (but ripped it out after LE announced
they are dropping support for TLS-SNI) that supported TLS-SNI
challenges at TLS level. This code relied on being able to detect
validation attempts at ClientHello time and then handling those
connections specially.


-Ilari

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