Re: [DNSOP] [perpass] draft-hzhwm-start-tls-for-dns-00: Starting TLS over DNS

Paul Vixie <paul@redbarn.org> Sat, 15 February 2014 18:08 UTC

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Subject: Re: [DNSOP] [perpass] draft-hzhwm-start-tls-for-dns-00: Starting TLS over DNS
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Watson Ladd wrote:
> Dear all,
> This proposal has multiple shortcomings compared to DNSCurve.
>
> First off, it says that the rationale for TLS over DNSCurve is simply
> to "take advantage of TLS". I would respectfully submit that DJB can
> do a better job than the TLS committee, and did. Merely adding bolts
> and nuts onto a design is not improving it.

has mr. bernstein's Curve25519 (see
http://en.wikipedia.org/wiki/Curve25519) been explicitly validated by
other crypto experts? last i knew he was the only one claiming it was
correct and strong enough for production use. this matters, because no
one person ought to be trusted to get something like this right sans
review. mr. bernstein's competence isn't being questioned, it's just the
"second set of eyes" requirement for technology at scale. i'm speaking
as an x.509-hater, which means, i tend to agree with what you said about
committees.

as a bolter-onner of many of dns's nuts including EDNS, i'm ready to
quibble with anyone who says DNS has not been improved by the post-1987
work that's been done to it. i won't claim it's gotten prettier, but
that's not the only metric for "improvement".

> Secondly, this proposal only works on TCP. This imposes latency and
> state requirements that most people would rather avoid. The use of
> keepalive only addresses computational burden, not state burden, and
> with the DH speed records we have today unnecessary.

my understanding is that this is a hop-by-hop cover protocol for adding
confidentiality when needed, and that something like dnssec will still
be needed for end-to-end content authenticity. in that sense the tcp
requirement isn't itself burdensome, though i will certainly recommend a
block-cipher mode so that udp can also be supported. this is not
something we can fix with DTLS or SCTP because of the all-pervasive
"middlebox problem". even getting EDNS options through has proved
difficult, a completely new transport is unthinkable.

> Thirdly, this proposal ignores entirely how to validate the server
> over the TLS connection. Does it need a certificate? Who should be
> allowed to sign it? How should it be validated? DNSSEC provides a PKI,
> and this proposal provides another one. Their interactions will not be
> fun.

see above; i don't think this proposal offers or intends to offer a PKI,
merely a hop-by-hop confidentiality option. DNSSEC will still be required.

> Fourthly, there is substantial operational knowledge and deployed,
> working, code implementing DNSCurve. This does not hold for this
> proposal.

dnscurve was offered to the ietf community but it didn't stick for
reasons unrelated to this newer proposal. i don't see any sense in
comparing their installed bases.

> Sincerely,
> Watson Ladd

warmly,

vixie