> Am 17.01.2018 um 10:45 schrieb Yann Ylavic <ylavic....@gmail.com>:
> On Wed, Jan 17, 2018 at 10:30 AM, Stefan Eissing
> <stefan.eiss...@greenbytes.de> wrote:
>>> Am 16.01.2018 um 21:26 schrieb William A Rowe Jr <wr...@rowe-clan.net>:
>>> Color me very confused, but I can't distinguish a difference between vhost 
>>> based
>>> Host: header selection in the "http-01" case, and SNI identification
>>> in the case of
>>> "tls-sni-01". Am I missing something? Discussion pointers?
>> "http-01" makes a request against the dns name to be validated. It is
>> usually not (easily) possible to intercept that from the wrong user account.
>> "tls-sni-0[12]" just opens a TLS connection with SNI <challenge>.acme.invalid
>> Some shared hosters have allowed people to upload a certificate for that. So,
>> you sign up via ACME (from anywhere) for a shared hosted not-my-domain.com
>> where you are also customer. Wait for the challenge token, create the cert 
>> and
>> upload it to the hoster.
> I think what is missing is simply "https-01", just like "http-01" but
> on TLS and a self signed cert (SNI is irrelevant).
> It don't see how it's less (nor more) secure than "http-01", but
> admins that don't want to or can't use port 80 have their way...

Agreed. Maybe they do it that way. But since this security weakness affects
the IETF proposed "tls-sni-02" challenge in the ACMEv2 protocol also, any
fix will first go through the working group there. And then maybe
backported be LE to their ACMEv1 offering or not.

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