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Re: [DNSOP] [Ext] About key tags and sensible limits

John Levine <johnl@taugh.com> Wed, 28 February 2024 02:37 UTC

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From: John Levine <johnl@taugh.com>
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Subject: Re: [DNSOP] [Ext] About key tags and sensible limits
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It appears that Mark Andrews  <marka@isc.org> said:
>It’s not the complexity of the validator we are worried about.  The number of crypto verifications per second is really low on all
>hardware.  Being able to stop validating on the first failure rather than having to continue because the attacker has constructed a
>colliding key tag rrset is beneficial to getting good put trough in the presence of a DoS attack.

Why do you have to try to validate everything rather than do some
sensible number and stop? When I look at RFC 4035 sec 5.3.3 I don't
see any MUSTs.

I could set up a 100 link CNAME chain that would resolve if you
followed the whole thing, but every cache will stop long before that.
Why is this different?

R's,
John

PS: I wouldn't be opposed to something like RFC 9276 that offered some
advice for things to limit in practical DNS resolution, but that's not
a protocol change, more like a BCP.

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