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Re: [Acme] ACME vulnerabilities in SimpleHTTP and DVSNI due to common webservers' default virtual host semantics

Michael Richardson <mcr@sandelman.ca> Thu, 24 September 2015 17:19 UTC

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From: Michael Richardson <mcr@sandelman.ca>
To: Peter Eckersley <pde@eff.org>
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References: <20150922215258.GJ17243@eff.org> <CAL02cgTaaaEtX1mcLrP6fxqMp_Q+9y+f+E0DYFedzMaJ5nXDRw@mail.gmail.com> <20150923211646.38db2ba94b986acac6caa431@andrewayer.name> <20150924045234.GL28925@eff.org> <30503.1443103383@sandelman.ca> <20150924165249.GP28925@eff.org>
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Date: Thu, 24 Sep 2015 13:19:38 -0400
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Cc: Richard Barnes <rlb@ipv.sx>, "acme@ietf.org" <acme@ietf.org>, Andrew Ayer <agwa@andrewayer.name>
Subject: Re: [Acme] ACME vulnerabilities in SimpleHTTP and DVSNI due to common webservers' default virtual host semantics
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Peter Eckersley <pde@eff.org> wrote:
    >> > Boulder does indeed follow redirects, so that's our current plan.
    >>
    >> So, if the verifier follows an HTTP redirect to an HTTPS site (does it
    >> even have to be same name?), which has a (at that point) bogus
    >> certificate, and Boulder can cope with that, when why bother having
    >> the SimpleHTTP check method at all?
    >>
    >> Why not just always use SimpleHTTPS?

    > Because it is common for webservers to be configured with HTTPS vhosts
    > that are a strict subset of the HTTP ones, plus a misallocted
    > default/wildcard HTTPS vhost that is controlled by the
    > tenant/hypothetical attacker.

Ah, so the attacker can control the wildcard HTTPS, and therefore get HTTPS
certificates for the vhosts that do not have their own HTTPS vhost.

I got it.

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