<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
My problem with your findings is that your are grossly overstating<br>their significance. None of them will ever be seen in the wild. As<br>As <a href="http://link.springer.com/chapter/10.1007/978-3-642-33167-1_16" target="_blank">http://link.springer.com/chapter/10.1007/978-3-642-33167-1_16</a> and<br>
as I've said, showing the inevitiable weakness of port randomization<br>is good.</blockquote><div><br></div><div>We found and described the vulnerability and showed how to apply it against standard and patched resolvers. Can you please clarify in what way our results `grossly overstate` significance?</div>
<div>Your second argument is not precise, we, and recently others, showed these attacks to be practical. Could you please explain why you are certain that the attacks do not pose a practical risk?</div>
<div><br></div><div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">I'm sorry, but I think the mention of DNSSEC in your paper exists only<br>
because others forced it. I'm forced to that belief by various things<br>including your refusal admit the obvious about relative priorities and<br>by statements like that sentence above that suggests that fixing port<br>
randomization could be easier than deploying DNSSEC in any except quite<br>exceptional cases.</blockquote></div><div><br></div><div>This conspiracy theory is intriguing...</div><div> </div></div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Sat, Oct 19, 2013 at 7:14 PM, Haya Shulman <span dir="ltr"><<a href="mailto:haya.shulman@gmail.com" target="_blank">haya.shulman@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif"><pre><pre>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 :-)</pre>
<pre>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.</pre>
<pre>---</pre></pre><pre><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">The complete absense of any mention of DNSSEC among those recommendations</blockquote>
(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
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">numbers?</blockquote></pre></div><div><div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Sat, Oct 19, 2013 at 6:53 PM, Haya Shulman <span dir="ltr"><<a href="mailto:haya.shulman@gmail.com" target="_blank">haya.shulman@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif">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.</div>
<div class="gmail_extra"><div><div><br><br><div class="gmail_quote">On Sat, Oct 19, 2013 at 6:05 PM, Phil Regnauld <span dir="ltr"><<a href="mailto:regnauld@nsrc.org" target="_blank">regnauld@nsrc.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>P Vixie (paul) writes:<br>
> M. Shulman, your summary does not list dnssec as a solution to any of these vulnerabilities, can you explain why not? Vixie<br>
<br>
</div> I was wondering about that, and went to look at the abstracts:<br>
<br>
<a href="http://link.springer.com/chapter/10.1007/978-3-642-33167-1_16" target="_blank">http://link.springer.com/chapter/10.1007/978-3-642-33167-1_16</a><br>
<br>
"Security of Patched DNS"<br>
<br>
[...]<br>
<br>
We present countermeasures preventing our attacks; however, we believe<br>
that our attacks provide additional motivation for adoption of DNSSEC<br>
(or other MitM-secure defenses).<br>
<br>
So at least this seems to be mentioned in the papers themselves (Id<br>
didn't pay to find out).<br>
<br>
But I agree that the summary would benefit from stating this, as it's<br>
currently only way to to avoid poisoning. Not stating it could lead<br>
some to believe that these attacks are immune to DNSSEC protection of<br>
the cache.<br>
<br>
Cheers,<br>
Phil<br>
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