[dns-operations] Downgrade attack readiness Re: DNSSEC issue - why?

[Edward Lewis]

On 6/9/15, 10:24, "Casey Deccio" <casey at deccio.net> wrote:

> But when you consider a downgrade attack, the attacker only needs the lowest
> hanging fruit.  That means that *any* DS (regardless of DNSKEY) with the
> weaker digest type could potentially be used for falsifying a DNSKEY.

I'm just going to throw this on the mat - perhaps we've (and I mean the
loose collective of folks involved with DNSSEC over the decades) had a poor
understanding of downgrade attacks (how they happen, etc.) and have poorly
addressed them. Given that I've never seen one (downgrade attack) work (in
practice/in the field), I've never been able to reverse engineer it.  Having
an academic/theoretic understanding is often times not sufficient.

Like learning to take down a spinnaker on a sailboat on a calm day in the
dock and then expecting to execute the steps heeled over in a gale.  Or
learning to change a diaper on a doll and then expecting to do the same for
the first time in the back seat of a car. ;)  Those are two areas where
cleanroom experience didn't translate to real world experience so much.

In general - has anyone seen an actual attack thwarted by DNSSEC?  Or an
attack beat a DNSSEC defense?  Not looking to justify the investment,
looking for the opportunity to reverse engineer.


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