[Trans] ***SPAM*** 7.971 (5) Re: ***SPAM*** 8.1 (5) Re: DNSSEC also needs CT

Ben Laurie <benl@google.com> Tue, 13 May 2014 14:59 UTC

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Date: Tue, 13 May 2014 15:58:51 +0100
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From: Ben Laurie <benl@google.com>
To: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
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Cc: Warren Kumari <warren@kumari.net>, Nico Williams <nico@cryptonector.com>, Joseph Bonneau <jbonneau@gmail.com>, "trans@ietf.org" <trans@ietf.org>, Paul Wouters <paul@nohats.ca>
Subject: [Trans] ***SPAM*** 7.971 (5) Re: ***SPAM*** 8.1 (5) Re: DNSSEC also needs CT
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On 13 May 2014 15:53, Daniel Kahn Gillmor <dkg@fifthhorseman.net> wrote:

> On 05/12/2014 02:01 PM, Nico Williams wrote:
> > On Mon, May 12, 2014 at 12:54 PM, Joseph Bonneau <jbonneau@gmail.com>
> wrote:
> >>> Clients (lazily perhaps).  The public.  Domain owners.  Registrars.
> >>
> >> Certainly possible, but I wonder how much this will happen in a world of
> >> thousands of DNSSEC-CT logs existing for various domains. Some of them
> >
> > The ones that matter most are the TLDs and the root.  Those get so
> > many users that they will be caught MITMing, if they do.
> I think technically what we care about is the public registries, not the
> TLDs.  This was my point about the public suffix list and DBOUND: that
> we care about .co.uk just as much as we care about .net.
> I know that some people use the term TLD to refer to the public
> registries instead of "top-level domains", but i think it's worthwhile
> to be precise in this discussion.
> > If evilhosting.com has lots of customers, then they'll help audit it,
> > else they might not.
> If evilhosting.com is handing out subdomains to its customers and
> expecting them to act as different administrative sub-zones, then
> evilhosting.com effectively *is* a public registry, and as such it needs
> to be auditable as well.  (it also needs to be considered a public
> registry for the sake of cookies and other same-origin policy things on
> the web, for example, so that jbonneau.evilhosting.com can't set cookies
> that would apply to dkg.evilhosting.com).
> > At any rate, the first-order problem in a
> > hierarchical public key system is keeping the roots and intermediates
> > closest to the roots honest.
> agreed that the primary concern is transparency, monitoring, and
> auditability of accumulated centralized control.
> Who is actually doing the monitoring and auditing is a separate
> question, though.
> note that CT appears to differentiate between monitoring (RFC 6962
> section 5.3) and auditing (RFC 6962 section 5.4) in this way:
>   Auditors make sure that SCTs are cryptographically valid against an
> STH, and that one STH chains properly to another;
>   Monitors make sure that the whole log itself is cryptographically
> valid, looking at all the data.
> Neither of these activities describes the actual checks that would need
> to happen for misissuance to be detected.  As noted in section 7.2,
> "interested parties" need to think about how to monitor to ensure that
> items with their administrative domains are not logged by other parties.

I think in effect these are monitors - i.e. they see the whole log, and may
as well cryptographically verify it while they do whatever-else-they-do. I
didn't want to specify what you might look for in logged certificates
because I think the answer is "whatever interests you".

> If this is neither "Monitoring" nor "Auditing" maybe we need a name for
> this kind of activity, so we can discuss it more directly?  how about
> "misissuance review"?
> So if Alice registers example.co.uk, she wants to do misissuance review
> for that zone.  But in a DNSSEC context, she needs to do misissuance
> review of the parent zones as well.  That is, she wants to ensure that
> .uk is not publishing spoofed records about the .co.uk nameservers and
> zone signing keys (how does she know if a change in DNSSEC records at
> this layer is a legitimate change?).

I don't get why Alice would want to do this - all Alice cares is that
example.co.uk is correctly issued, right?

>  And she also wants to ensure that
> .co.uk is not publishing spoofed records about the example.co.uk zone.

> How does she know what logs to look in for this misissuance review?  Is
> there a way she can do this review efficiently?  I think these questions
> are relevant for regular CT as well, but a DNSSEC-focused CT adds the
> wrinkle of delegated zones.  (maybe this isn't actually worse than X.509
> PKI with its fully-delegated intermediate CAs though?)

My naive first crack at this question was: each parent designates where its
children are logged (which may be the same log as the parent, of course,
but allows the parent to delegate for big/spammy users).

>         --dkg
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