Re: [Doh] Mozilla's plans re: DoH

[Petr Špaček <[e-mail]>]

On 01. 04. 19 22:45, Eric Rescorla wrote:
> 
> 
> On Mon, Apr 1, 2019 at 1:32 PM Brian Dickson
> <[e-mail] <mailto:[e-mail]>>
> wrote:
> 
> 
> 
>     On Wed, Mar 27, 2019 at 2:18 AM Eric Rescorla <[e-mail]
>     <mailto:[e-mail]>> wrote:
> 
>         I’ve heard a number of questions about Mozilla’s plans around
>         DoH. We’ve made a number of public statements, but it might be
>         useful
>         to try to put this all in one place.
> 
>         In context, the problem we are attempting to solve here is attack on
>         the user’s name resolution from an attacker with full or partial
>         control of the network, as contemplated by Section 3 of BCP 72
>         as well
>         as BCP 188. There’s ample evidence of monitoring/manipulation of
>         user
>         traffic via this vector [0][1][2].
> 
> 
>         [1]
>         https://www.usenix.org/system/files/conference/usenixsecurity17/sec17-pearce.pdf
> 
> 
>     Looking specifically at the problem statement and evidence, I have a
>     question about this (or any other) investigative work:
>     Has there been any related/follow-up work, or other similarly scoped
>     work, to examine the use of DNSSEC in the domains tested, that
>     you're aware of or can point folks at?
> 
> 
>     I.e. Were any of the manipulated domains signed DNSSEC domains,
>     where validation might have prevented the manipulated responses from
>     being accepted from the resolver?
> 
>     Clearly there would still be the issue of being able to find/reach a
>     resolver that does not manipulate results, but at least the
>     manipulation would be detected/blocked.
> 
> 
> I don't have much more information than is in the paper (you'll note I'm
> not an author), but generally DNSSEC doesn't help that much here. You
> can't safely do DNSSEC validation on user-facing clients because of a
> combination of tampering by middleboxes (typically record stripping,
> etc,. not really "attacks") and errors in the published DNSSEC records.

Tampering by middleboxes is solved by DoH, isn't it?

Statement "can't safely do DNSSEC validation on user-facing clients
because of ... errors in the published DNSSEC records" requires some
evidence to show it is still valid in 2019.

According to APNIC's data [1] ~ 17 % of web population is behind DNSSEC
validating resolver today, so anyone who screws up DNSSEC will notice
and fix it quite quickly.

Second data point is that we (as CZ.NIC company) provide support to
telcos operating DNSSEC-validating resolvers, and do not see any
significant breakage caused by misconfigured DNSSEC. To give some weight
to this statenemt please note that CZ has ~ 65 % users behind validating
resolvers, CZ.NIC doing support also for local telcos, and we simply do
not see the rummored breakage caused by DNSSEC misconfiguration.

[1] https://stats.labs.apnic.net/dnssec

-- 
Petr Špaček  @  CZ.NIC