On Mon, Mar 25, 2024 at 09:27:06AM +0100, Haya Shulman wrote:
> Our evaluations demonstrate that the two attack vectors are fundamentally
> different from the perspective of their practical impact: KeyTrap
> introduces a realistic immediate threat for exploitation by hackers. In
> contrast, with NSEC3-encloser attack a comparable load on resolvers is not
> possible, not only that with a single NSEC3-encloser attack no packet is
> lost, but also no latency is introduced to the resolvers. The high volume
> of NSEC3-encloser attack traffic, of more than hundreds of packets per
> second, makes the NSEC3-encloser attack visible. Therefore, the high attack
> volume in tandem with the meager benefit for adversaries (only a small
> fraction of benign packets dropped) implies that such attacks do not pose a
> practical threat.
Reading the paper, I get an impression that the described attack isn't
nearly as stressful on the resolver CPU as it could be. If I understood
the measured attack correctly, a more "malicious" approach could
substantially (~100x) increase the per-query-response CPU cost. Perhaps
qualitatively changing the relative impact assessment?
I do hope that, as a community, we'll continue to steadily streamline
acceptable NSEC3 parameters (per RFC9276) down to 0 additional
iterations and short enough salt values (that don't result in additional
SHA-1 input blocks).
--
Viktor.
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