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Re: [Acme] Short term certificates - two options

Yaron Sheffer <yaronf.ietf@gmail.com> Wed, 20 July 2016 15:40 UTC

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To: Niklas Keller <me@kelunik.com>
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From: Yaron Sheffer <yaronf.ietf@gmail.com>
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Date: Wed, 20 Jul 2016 17:40:07 +0200
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Cc: ACME WG <acme@ietf.org>
Subject: Re: [Acme] Short term certificates - two options
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On 20/07/16 14:43, Niklas Keller wrote:
> 2016-07-20 11:51 GMT+02:00 Yaron Sheffer <yaronf.ietf@gmail.com
> <mailto:yaronf.ietf@gmail.com>>:
>
>     Hi,
>
>     At the LURK BoF this week there was some interest in having a solution
>     where a domain owner can delegate to some other entity (which we will
>     call "the TLS server") the authority to terminate TLS connections on its
>     behalf, using short-term certificates. These certificates allow the
>     domain owner to terminate the TLS server's authorization when necessary,
>     without requiring certificate revocation - which we know doesn't work
>     reliably. The certificates' validity is measured in days, e.g. 3 days.
>
>     First, I would like to request the working group to adopt short-term
>     certificates as a charter item.
>
>     Second, I would like the group's advice in choosing between two very
>     different approaches to this problem.
>
>
> You can already delegate HTTP-01 by redirecting
> `/.well-known/acme-challenge/*` (maybe even just for unknown tokens).
>
> Also, for short-lived certificates, there's already the `notAfter` field
> when filing applications for a certificate:
>
> https://ietf-wg-acme.github.io/acme/#rfc.section.6.1.3
>
> Regards, Niklas

In fact delegating HTTP-01 is a big security issue in the context of 
rogue CDNs (or CDN employees). Please see 
https://tools.ietf.org/html/draft-sheffer-lurk-cert-delegation-00#section-4.3

Thanks,
	Yaron

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