[dns-operations] summary of recent vulnerabilities in DNS security.

[Haya Shulman]

>
> In that case, on what should an organization spend time or money

first, on DNSSEC or the recommendations in the mail message?  Would
it be better if each of the recommendations in the mail message
started with something like this?

    Deploy DNSSEC, and consider the follow to help protect cached

    data not yet protected with DNSSEC.
>


It's a good point, thanks. I will rewrite the recommendations according to
what is essential and also against which type of attack and to what network
configuration it applies.


That sounds like a more significant bug than port obscurity or

randomization.  If it is a bug, which should be addressed first in
that software or those installations, this DNSSEC bug or the
recommendations in the mail message?  It it is a significant DNSSEC
bug, it would be good if a future version of the mail message

mentioned it.
>

It is not always a bug imho. Some resolvers, e.g., unbound, explicitly
allow such permissive modes of DNSSEC validation, others support this
implicitly and the rest may simply be not configured properly.
Permissive modes are typically used during the incremental deployment
phases prior to full adoption, e.g., to see that DNSSEC works ok, and does
not break anything.
Permissive mode introduces a security vulnerability - since a resolver
signals support of DNSSEC, it receives large (often fragmented) responses,
and thus may be vulnerable to our cache poisoning attack. On the other
hand, network operators, may be concerned (often justly) with enforcing
strict DNSSEC validation, due to interoperability (or other) problems (we
discuss this in more detail in `Availability and Security Challenges
Towards Adoption of DNSSEC`).

>
>
>

On Sat, Oct 19, 2013 at 7:14 PM, Haya Shulman <haya.shulman at gmail.com>wrote:

> IMHO, DNSSEC is simply the natural defense against the attacks, which is why I did not explicitly mention it, but I definitely had it in mind :-)
>
> Regarding the proxy-behind-upstream: to prevent the attacks DNSSEC has to be deployed(and validated) on the proxy. Currently it seems that there are proxies that signal support of DNSSEC (via the DO bit), but do not validate responses, and validation is typically performed by the upstream forwarder.
>
> ---
>
> The complete absense of any mention of DNSSEC among those recommendations
>
>
>
>
>
> (or elsewhere) reads like an implicit claim that DNSSEC would not
> help.  Even if that claim was not intended, would it be accurate?
>
> Would DNSSEC make any of recommendations less necessary or perhaps
> even moot?  If DNSSEC by itself would be effective against cache
> poisoning, then isn't it among the recommendations, especially for
> "Resolver-behind-Upstream"?  Why aren't efforts to protect port
> randomization, hide hidden servers and so forth like trying to make
> it safe to use .rhosts and /etc/hosts.equiv files by filtering ICMP
> dedirects and IP source routing, and strengthening TCP initial sequence
>>
>> numbers?
>
>
>
> On Sat, Oct 19, 2013 at 6:53 PM, Haya Shulman <haya.shulman at gmail.com>wrote:
>
>> This is correct, the conclusion from our results (and mentioned in all
>> our papers on DNS security) is to deploy DNSSEC (fully and correctly). We
>> are proponents of cryptographic defenses, and I think that DNSSEC is the
>> most suitable (proposed and standardised) mechanism to protect DNS against
>> cache poisoning. Deployment of new Internet mechanisms is always
>> challenging (and the same applies to DNSSEC). Therefore, we recommend short
>> term countermeasures (against vulnerabilities that we found) and also
>> investigate mechanisms to facilitate deployment of DNSSEC.
>>
>>
>> On Sat, Oct 19, 2013 at 6:05 PM, Phil Regnauld <regnauld at nsrc.org> wrote:
>>
>>> P Vixie (paul) writes:
>>> > M. Shulman, your summary does not list dnssec as a solution to any of
>>> these vulnerabilities, can you explain why not? Vixie
>>>
>>>         I was wondering about that, and went to look at the abstracts:
>>>
>>> http://link.springer.com/chapter/10.1007/978-3-642-33167-1_16
>>>
>>> "Security of Patched DNS"
>>>
>>> [...]
>>>
>>> We present countermeasures preventing our attacks; however, we believe
>>> that our attacks provide additional motivation for adoption of DNSSEC
>>> (or other MitM-secure defenses).
>>>
>>>         So at least this seems to be mentioned in the papers themselves
>>> (Id
>>>         didn't pay to find out).
>>>
>>>         But I agree that the summary would benefit from stating this, as
>>> it's
>>>         currently only way to to avoid poisoning. Not stating it could
>>> lead
>>>         some to believe that these attacks are immune to DNSSEC
>>> protection of
>>>         the cache.
>>>
>>>         Cheers,
>>>         Phil
>>>
>>
>>
>>
>> --
>>
>> Haya Shulman
>>
>> Technische Universität Darmstadt****
>>
>> FB Informatik/EC SPRIDE****
>>
>> Morewegstr. 30****
>>
>> 64293 Darmstadt****
>>
>> Tel. +49 6151 16-75540****
>>
>> www.ec-spride.de
>>
>
>
>
> --
>
> Haya Shulman
>
> Technische Universität Darmstadt****
>
> FB Informatik/EC SPRIDE****
>
> Morewegstr. 30****
>
> 64293 Darmstadt****
>
> Tel. +49 6151 16-75540****
>
> www.ec-spride.de
>



-- 

Haya Shulman

Technische Universität Darmstadt****

FB Informatik/EC SPRIDE****

Morewegstr. 30****

64293 Darmstadt****

Tel. +49 6151 16-75540****

www.ec-spride.de
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