Subject: RE: dictionary attack on nameservers

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Tue, 17 Aug 2004 10:23:24 -0700

> That's certainly true. Not that I could contribute much anyway. But
> this is beside the point. We have a DNS infrastructure that's not
> secure. The longer we delay the deployment of DNSSEC (for some
> definition of "deployment" and "DNSSEC"), the more likely it is
> Something Very Bad will happen. It's only a question of time before
> the script kiddies start to attack the DNS.

Then the sooner we have a DNSSEC specification that is ready for
deployment the better.

That means fixing security issues, not burrying your head in the
sand claiming that they do not exist.

The sooner the enumeration issue is fixed, the sooner we can start
on deployment. Until the enumeration issue is fixed to the satisfaction
of security specialists the spec is not going to be ready for 
deployment.

We have a security need, we have a simple solution, the only thing
that stops deployment is the fact that some people claim that the
problem does not exist according to a failled 20 year old dogma that
they do not understand.

Every argument raised on this list was raised fifteen years ago when
I was arguing the need for shaddow passwords in UNIX. It was several
years before crack came out and made it impossible for folk to hide
their heads in the sand.

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From: Greg Hudson <[email-masked]>
Date: Tue, 17 Aug 2004 13:54:24 -0400

On Tue, 2004-08-17 at 13:23, Hallam-Baker, Phillip wrote:
> We have a security need, we have a simple solution,

We do?  It seems like hashed nsec records aren't going to stop organized
crime families.  Only online signing of negative responses would really
prevent someone from enumerating a zone, and online signing is a vector
for DOSing DNS itself.

> I was arguing the need for shaddow passwords in UNIX.

Really?  People said passwords are supposed to be public?  People said
there were other easy ways of figuring out most users' passwords? 
Fascinating.

---

From: [email-masked]
Date: Tue, 17 Aug 2004 18:12:11 +0000

> of security specialists the spec is not going to be ready for 

	the enumeration issue? I am confused here.  are you asserting
	that enumeration is not currently possible or that it should
	be made impossible?  For me, enumeration is a fact of life in the
	DNS.  Normal queries give me effective enumeration.  The debate 
	here seems to revolve around the "degree" of enumeration that
	is considered an acceptable risk.

	now not to pick on the security specialists, but the last time
	they controlled the development of the DNSSEC protocol, we ended
	up with something that was emperically proven to be a non-starter.
	
	Operationally flawed.  Unworkable in the real world.  So, like
	most security issues, this is a series of tradeoffs.  I dont expect
	your arguments about DNSSEC deployment not being ready until 
	the unnamed cadre of "security specialists" agree, will hold much
	credability.  (ask 3 security folks a question and get 7 answers)

	what is of interest/importance to some of us is the ability to 
	mitigate known problems in a timely fashion.  we recognise that 
	evolution is an iterative process and that waiting for the one true
	pedultimate solution is counter productive.  The specs - as written -
	are "good enough" for many of the concerns that are out there.  

> problem does not exist according to a failled 20 year old dogma that

	what is the "need"?   and what is the solution to this "need"?
	(I find it tangentially interesting that "a failled 20 year old
	dogma" has made many companies profitable, pays the salaries of
	good engineers, security specialists, and operators, and allows
	us to have the debate.  Clearly your definition of failure is
	radically distinct from mine. :)

--bill

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From: "Eric A. Hall" <[email-masked]>
Date: Tue, 17 Aug 2004 15:26:40 -0400

On 8/17/2004 1:23 PM, Hallam-Baker, Phillip wrote:

> on deployment.

If dictionary attacks are a problem in general, then a generalized fix is
as easy as defining an RCODE for "refused due to policy"

-- 
Eric A. Hall                                        http://www.ehsco.com/
Internet Core Protocols          http://www.oreilly.com/catalog/coreprot/

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From: Ben Laurie <[email-masked]>
Date: Sun, 22 Aug 2004 12:55:24 +0100

> prevent someone from enumerating a zone, and online signing is a vector

Surely online signing is no more effective than hashing (i.e. they are 
both susceptible to dictionary attacks)?

-- 
http://www.apache-ssl.org/ben.html       http://www.thebunker.net/

"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff

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From: Greg Hudson <[email-masked]>
Date: Sun, 22 Aug 2004 10:20:24 -0400

> both susceptible to dictionary attacks)?

Well, an offline dictionary attack is much, muhc faster than an online
one.  (Particularly if the server has to perform online signing for each
iteration of the online one.)

It's possible that I've overestimated how effective an offline
dictionary attack can be, in which case perhaps hashed nsec records
really do raise the bar high enough.

---

From: Ben Laurie <[email-masked]>
Date: Sun, 22 Aug 2004 16:35:55 +0100

> really do raise the bar high enough.

The idea was to make the cost similar to an online attack - this is why 
there is an iterations field.

Cheers,

Ben.