Re: https at ietf.org

On 12/10/2013 06:00 AM, John C Klensin wrote:
> --On Monday, December 09, 2013 22:39 -0500 Phillip Hallam-Baker
> <hallam(_at_)gmail(_dot_)com> wrote:
>
> > ...
> > > For a similar reason removal of TLD's can't happen as people
> > > can still graft on namespace and establish TA's for the
> > > grafted on namespace.
> >
> > It is trivial to fix when the validation is taking place in a
> > service in the cloud (aka a resolver).
> >
> > Rather less easy to do if people drink the DANE cool-aid and
> > do the job at the end point.
> >
> > Now you can take this point as either arguing against doing
> > DANE or considering the risk and deploying the appropriate
> > control. But you do have to consider it.
> >
> >
> > What you are in effect asserting is that the resolver
> > providers are the apex of the trust chain and so there is a
> > diffuse trust surface rather than a sharp point. Which is true
> > when the validation takes place in the resolver.
> I am probably going to regret getting involved in this thread,
GMTA :)

> but I would draw two rather different conclusions from the above
> and a number of other comments:
>
> (1) We have seriously oversold DNSSEC as a data quality and
> reliability mechanism when it is merely a transmission integrity
> mechanism.  The former is about the DNS and associated
> registration database (e.g., "whois") records being accurate,
> secure, and maybe even information-containing.  The latter is
> merely about an assurance that the data one receives hasn't been
> altered in transit in the DNS.
>
> Now most of the people who have been involved in the design and
> implementation of DNSSEC have been quite careful about the
> above, at least most of the time.  But sometimes they are sloppy
> about their language, sometimes they say "DNNSEC" and people
> hear "DNS Security" and make inferences to data quality.  More
> important, there is an (illogical) chain of reasoning from
> "DNSSEC is in use" to "[now] the DNS is secure" to "all of the
> data provided by the DNS or its supplemental databases are of
> high quality".
>
> While the integrity checks of DNSSEC provide some protection
> against some types of attacks on the "data quality" part of the
> DNS environment, the attacks they protect against are very
> difficult.
John,

IMO you're spot on with all of the above. Especially about being careful 
with our language about what DNSSEC is designed to do. I try very hard 
to be precise, but it's good to have this reminder periodically.
> An attacker with the resources to apply them would
> almost certainly find it easier, less resource-expensive, and
> harder to detect to attack registry databases (before data are
> entered into DNS zones and signed), registrar practices, or
> post-validation servers.  Non-technical attacks, such as the
> oft-cited hypothetical NSL, are easily applied at those points
> as well -- much more easily than tampering with keys or
> signatures.
As previously mentioned, these attacks are theoretically possible, but 
they are trivially detectable since all of the critical data is visible 
in the DNS. They may not be _immediately_ detectable, and in fact likely 
would not be detected immediately; where "immediate" is going to vary 
widely depending on the value/profile of the target. But we have plenty 
of experience with people noticing DNS problems for critical resources. 
Even in the DNSSEC case we have major players doing DNSSEC validation 
now (Comcast and Google leap to mind) so shenanigans involving DNSSEC 
are going to be noticed.
The point I'm trying to get across here is that any sort of manipulation 
of the DNS by a 3rd party (such as a malicious hack, NSL, etc.) is 
valuable only to the extent that it can go unnoticed, and therefore 
cause innocent end users to depend on the 3rd party's resources instead 
of the valid ones _without their knowledge_.
We don't need DNSSEC to see that this sort of thing only works for a 
limited time. We have had lots of events where high profile sites have 
had their registrar data changed, and there is a huge public hue and 
cry. Of course a skillful attacker could create a phishing page that 
looks enough like the real site to gather a non-trivial number of user 
passwords, but again, we don't need DNSSEC for that. In fact, if the 
sophisticated attacker manages to socially engineer the registrar 
credentials (the most popular form of this type of attack) then they can 
update the DS record in addition to the NS records, and have a fake site 
that validates perfectly.
But even that sort of attack would only work for a short period of time. 
More importantly, the ability to slide the malicious data into the DNS 
at all is going to be proportional to the location of the resource in 
the tree. We already know that individual zones are vulnerable to 
registrar attacks. However new TLD DS records in the root are greeted 
with fanfare (at least amongst a fairly substantial number of DNS 
wonks), so the ability to slip stuff in at that level is minimal at 
best. This is more true at the root itself.
So to be concise (yeah, I know, too late) claiming that DNSSEC is 
vulnerable to external manipulation at the root or TLD level is almost 
certainly wrong. There are theoretical attacks that could be launched, 
but their practical value is nil. If someone has a valid attack that 
uses a method I haven't taken into account, they should find a trusted 
channel to make that known.
> (2) In a different version of some of the comments on the
> thread, the "where to validate" question is important.  If one
> tries to validate at the endpoints, endpoint systems, including
> embedded ones, should have the code and resources needed to
> validate certs and handle rollovers, even under hostile
> conditions, and that isn't easy.  If one relies on intermediate,
> especially third-party, servers to validate, than much of the
> expected integrity protection is gone... and the number of times
> such servers have been compromised would make this a
> non-theoretical problem even without concerns about
> governmental-type attacks (NSL and otherwise) on those servers.
> No easy solutions here.
Again, spot on. I've been saying for many years now that the most 
interesting part of DNSSEC is going to be local on the end user side. 
Pushing validation all the way down is critical.
> I don't know where that combination of situations leaves
> initiatives like DANE, but I suspect we should be looking at
> trust conditions and relationships a lot more carefully than the
> discussions and claims I've seen suggest we have been doing.
I like DANE a lot, and I think it has a critical role going forward. The 
problem is that it is only as valid as the registrar data for the zone. 
So it's not clear that DANE is going to be a complete replacement for a 
CA-provided cert.
Doug