Re: Comments on draft-ietf-httpbis-http2-secondary-certs-04

Ryan Sleevi <ryan-ietf@sleevi.com> Fri, 09 August 2019 00:33 UTC

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From: Ryan Sleevi <ryan-ietf@sleevi.com>
Date: Thu, 8 Aug 2019 20:30:39 -0400
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Subject: Re: Comments on draft-ietf-httpbis-http2-secondary-certs-04
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On Thu, Aug 8, 2019 at 7:47 PM Ryan Sleevi <ryan-ietf@sleevi.com>; wrote:
<Snip for everyone's benefit>

> You might say this is news.example's fault, for not rejecting CDN 1's
> certificate when it transitioned authority. This is BygoneSSL - and why I
> mentioned revocation. I don't think we'd suggest that CDN 1 is necessarily
> behaving adversarial - after all, news.example previously authorized them.
> However, CDN 1 doesn't know that news.example now has a relationship with
> CDN 2 (again, c.f. BygoneSSL), and thus doesn't know it should stop
> advertising to serve news.example via CDN 1's connection.
>
> Does that resonate more?
>

I suppose it's worthwhile to highlight that the assumption about that 6.5 -
and explicitly stated in 6.1 - is the omission of a DNS check prior to
using the asserted identity. That's not something inherent to
secondary-certs, but something it inherits from Section 1.1 / RFC 8336. If
https://tools.ietf.org/html/draft-bishop-httpbis-origin-fed-up were to
progress - such that a DNS check existed - then arguably the security
concerns for 6.1 / 6.5 would disappear.

Put differently, the security risk is not in secondary-certs; it's in
secondary-certs + skipping DNS. The current draft indirectly depends on
skipping DNS, but that's something that can change, in which case, I think
some of the concerns highlighted would disappear. That's just not (yet?) in
the current draft.