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Re: [Acme] kinds of proof

Christian Huitema <huitema@microsoft.com> Tue, 02 December 2014 01:18 UTC

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From: Christian Huitema <huitema@microsoft.com>
To: Peter Bowen <pzbowen@gmail.com>, Randy Bush <randy@psg.com>
Thread-Topic: [Acme] kinds of proof
Thread-Index: AQHQCzpQ0gc5ZtwH40O9AzCFhy8+6Zx2kIoAgAAFu4CAAUCrAIADmfIAgAASxACAAAB08A==
Date: Tue, 02 Dec 2014 01:18:20 +0000
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Cc: "acme@ietf.org" <acme@ietf.org>, Viktor Dukhovni <ietf-dane@dukhovni.org>
Subject: Re: [Acme] kinds of proof
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>> or dns
>
> Yes, several CAs allow DNS based validation of control.
> https://gist.github.com/pzb/3b57ddac91ccf0e4c814 lists several of the schemes I've seen used.  There is clearly no > standard or even quasi-standard for DNS based validation.

To belabor the obvious: if someone somehow controls the DNS entry for the domain, they can put up a MITM attack and "insert" whatever content is suitable for validation.

Consider the following attack: attacker engages an automated transaction with the CA, simultaneously manages to spoof the DNS entry, gets certificate. That should definitely be part of the threat model.

-- Christian Huitema

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