Re: [Trans] DNSSEC also needs CT

Paul Wouters <paul@nohats.ca> Tue, 13 May 2014 13:55 UTC

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Date: Tue, 13 May 2014 09:55:05 -0400 (EDT)
From: Paul Wouters <paul@nohats.ca>
To: Ben Laurie <benl@google.com>
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Subject: Re: [Trans] DNSSEC also needs CT
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On Tue, 13 May 2014, Ben Laurie wrote:

[DNSSEC CT]

> Is it necessary to log anything other than keys? My base assumption was no: if the keys are as expected, then all records signed by those keys
> can be trusted. If someone wants to publish RRsets that are other than the one the true domain owner wants to publish, they necessarily have
> to inject a key they control, which becomes apparent from the logs.

That would not allow us to detect coercion, that is a custom RRset signed
to be used only for a targetted attack (by say, .com or the root)

But I'm not sure how we _could_ detect that. Let's say they get an A
record for www.victim.com that bypasses the NS RRset completely, that
is, signed by the .com key. To notice this case, you would also need to log
the change of zone cut.

The other case is injection of a custom DS RRset. How would we tell the
difference between the legitimate zone owner adding a DS record or an
attacker/parent zone owner adding one? One defense would be to ignore
any new DS record for a certain amount of time, but that runs into
similar issues as pinning and TACK.

Paul