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Re: [Trans] DNSSEC also needs CT

Ben Laurie <benl@google.com> Tue, 13 May 2014 15:02 UTC

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Date: Tue, 13 May 2014 16:02:11 +0100
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From: Ben Laurie <benl@google.com>
To: Paul Wouters <paul@nohats.ca>
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Subject: Re: [Trans] DNSSEC also needs CT
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On 13 May 2014 14:55, Paul Wouters <paul@nohats.ca> wrote:
>
> 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.


OK, good point: zone cuts need to also be verified.

> 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?

The legitimate owner can tell - that's the point, right?

> 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




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