Subject: Re: dictionary attack on nameservers

From: Roy Badami <[email-masked]>
Date: Tue, 7 Sep 2004 22:57:30 +0100

I hadn't been intending to respond to the chairs' call for 20-line
summaries, since I regard myself as an intersted bystander rather than
an active WG member...  However Olaf contacted me privately requesting
I do so, so here goes...

--------

I regard it as highly desirably to reach some sort of consensus that
includes those ccTLDs that have concerns about enumeration, and
realistically I think that means addressing their requirements, rather
than convincing them to change their requirements.  I'm pleased that
the co-chairs seem to concur that this is worth persuing...

I don't have any strong feelings as to the shape that the technical
solution should take though I note that Bloom filters have been
completely neglected in recent discussions, and I think they may still
be of possible value -- see for example Steve Bellovin's ID
http://www.research.att.com/~smb/papers/draft-bellovin-dnsext-bloomfilt-00.txt

I would argue that authenticated denial is important in a TLD, and
that provably-insecure delegations are vital, as without them the
level of security offered to customers of that TLD is diminished.

I note also that if some TLDs choose not to offer these security
guarantees, then there will be no incentive for their customers to
migrate away from transitional mechanisms such as Paul Vixie's DLV
(which does offer those guarantees, at least to participating resolvers).

       -roy

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From: Roy Arends <[email-masked]>
Date: Thu, 9 Sep 2004 09:23:35 +0200 (CEST)

Hi,

I'd like to fix NSEC name leakage in order to make zone enumeration with
DNSSEC not easier then without DNSSEC.

Not at any cost though, it would be nice if we can satisfy most/all of the
following requirements (stolen from Ed's mail, thanks Ed)

Prove non-existence of name/type without

 - leaking names
 - introducing fake names
 - on-demand cryptographic operations
 - being vulnerable to replay attacks
 - incompatible changes with current DNSSEC

Satisfying all requirements seems hard. If we can prioritise them, we've
come a long way.

Roy

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From: Mark Andrews <[email-masked]>
Date: Fri, 10 Sep 2004 07:58:10 +1000

I doubt there is a perfect solution that will solve everyones
	problems.  There may need to be a suite of solutions that
	the zone administrator can choose between.

	DNSSEC and DNS itself is a set of engineering tradeoffs.
	DNSSECbis just changes the the current set of tradeoffs.
	Spoofing (DNS) vs enumeration (DNSSEC/DNSSECbis)

	I dislike the hashing solutions as it introduces namespace
	pollution and doesn't allow all existing DNS zones to be signed.

	I can live with online signing though I don't believe that
	NSEC white lies is the best way to do this.  If we have to
	have online signing then we should look for a better way
	to do this than NSEC white lies.  I believe we can introduce
	a new type of zone signing and have no impact on DNSSECbis
	servers.  The zones would be treated as unsigned by DNSSECbis.

	This would give the zone operator the choice of spoofable
	results, enumeration or online signing.  I don't believe
	that the other tradeoffs are the way to go.  We already
	have online signing for secure updatable zones.

	Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: [email-masked]

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From: Alex Bligh <[email-masked]>
Date: Fri, 10 Sep 2004 11:17:54 +0100

> 	pollution and doesn't allow all existing DNS zones to be signed.
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

At the risk of annoying Olaf, but for the purposes of getting a common
understanding of all our position, could you elaborate on the bit
underlined by carrets? (i.e. either it's a new point or I've completely
missed something).

Alex

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From: Marcos Sanz/Denic <[email-masked]>
Date: Fri, 10 Sep 2004 13:22:56 +0200

On 01 September 2004 11:14 +0200 "Olaf M. Kolkman" <[email-masked]> wrote:

> I want to close this thread by giving every participant the
> opportunity to state their concluding argument in not more than 20
> lines of text.

Overcoming my original reluctance to give a summary of my position, 
because the chairs did not privately contact me to do so *lol*, here it 
goes:

The current list of requirements (
http://www.links.org/dnssec/requirements.txt) reflects my expectations for 
a signed proof of non-existence (modulo my remarks sent privately to the 
authors 3 weeks ago: ICMP_ECHO_REQUEST), so I won't list the requirements 
here again. IMHO some of them are less and some are more relevant, but it 
has repeatedly been said that we are still in the phase of outspeaking 
requirements, and we all know that a solution will probably imply a 
trade-off among them.

Best,
Marcos

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From: Mark Andrews <[email-masked]>
Date: Fri, 10 Sep 2004 23:25:42 +1000

> > 	pollution and doesn't allow all existing DNS zones to be signed.

	If I have a zone with domainnames/zonename that are almost
	maximal length the addition of the hash causes the resulting
	domainnames to exceed maximimal length.