Re: [dnsext] DS digest downgrade

In message <sjmipvbcnt7.fsf@pgpdev.ihtfp.org>, Derek Atkins writes:
> Francis Dupont <Francis.Dupont@fdupont.fr> writes:
> 
> >  In your previous mail you wrote:
> >
> >    i.e. the zone is using SHA1 DS records, admin generates new KSK,
> >    publishes SHA256 DS for the new KSK but doesn't publish SHA256 DS
> >    for the old KSK, leading to validat ion failures.
> >    
> > => this should never happen as the rule is in fact for the
> > replacement of SHA1 by SHA256 as the DS digest algorithm.
> >  But don't believe we are saved: there are other DS digest algos
> > (and even more to come) and the mixed algo case is dangerously
> > under-specified...
> 
> It also doesn't help protect against an active man-in-the-middle who can
> make sure that the validator never receives the SHA256 DS RR.
> Unfortunately the validator can only validate what it receives; there's
> often not a way for it to know what it should expect to receive.

This attack is not possible.

> > Regards
> >
> > Francis.Dupont@fdupont.fr
> 
> -derek
> 
> -- 
>        Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
>        Member, MIT Student Information Processing Board  (SIPB)
>        URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
>        warlord@MIT.EDU                        PGP key available
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Mark Andrews, ISC
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