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Date:      Wed, 9 Jul 2008 21:59:33 -0700 (PDT)
From:      Jason Stone <freebsd-security@dfmm.org>
To:        Chris Palmer <chris@noncombatant.org>
Cc:        Mark Boolootian <booloo@ucsc.edu>, freebsd-security@freebsd.org
Subject:   Re: BIND update?
Message-ID:  <alpine.BSF.1.00.0807092136120.34772@treehorn.dfmm.org>
In-Reply-To: <20080710002749.GK55473@noncombatant.org>
References:  <17cd1fbe0807090819o2aa28250h13c58dbe262abb7c@mail.gmail.com> <3a558cb8f79e923db0c6945830834ba2.squirrel@galain.elvandar.org> <17cd1fbe0807090909i566e1789s6b7b61bf82dd333e@mail.gmail.com> <4874ECDA.60202@elvandar.org> <4874F149.1040101@FreeBSD.org> <17cd1fbe0807091027n6af312cbwab3d3277f2b5e081@mail.gmail.com> <20080709182340.GD55473@noncombatant.org> <4875481E.4000100@kernel32.de> <20080709235204.GB72293@root.ucsc.edu> <20080710002749.GK55473@noncombatant.org>

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>> Everyone that uses the Internet depends on the security of DNS.

> That's too bad, because DNS never made any security guarantees. When you 
> ask to resolve www.google.com, the answer does not mean "www.google.com 
> is on the network at 74.125.19.104." It means "As far as we can tell at 
> the moment, www.google.com might be on the network at 74.125.19.104, or 
> that might be a total lie. Good luck! P.S.: Lying is very easy."
>
> There are no guarantees of authentication, authorization, or integrity.

Yes, yes, DNS makes no security guarantees, it's always been vulnerable, 
this is old old news.

But answer truthfully: have you never launched a browser and typed 
"www.google.com" into it?  I suspect that you have.  So this affects you 
too.

So you say, "But I don't send important information over that connection, 
nor do I trust the information I get back?"  Maybe.  I think that the AOL 
data leak fiasco proved that, while people don't generally think of search 
queries as sensitive, they really kind of are.  And you almost certainly 
place _some_ trust in the results you get back; I mean, you're not reading 
them purely as fiction.

But let's leave that aside for a second and assume it's true: you 
genuinely don't care about privacy or tampering while you're just casually 
surfing.  That's not what's at issue; what's at issue is that you're 
choosing to let unknown and untrusted sites inject arbitrary data into 
your web browser.  And your browser has more exploitable bugs in it than 
you can shake a stick at.  It doesn't matter which browser you use -- IE, 
Firefox, Safari, Opera, Lynx, w3m -- I guarantee you, it has more holes 
than you can shake a stick at.  You could run it in a chroot, or with a 
different UID from your normal user... but you don't.

So, if your DNS resolver is vulnerable to cache poisoning, then every time 
you casually surf the web, you're allowing for the possibility that you 
will get spoofed, surf to some malware site, get served a browser exploit, 
and get 0wned.  This is not just theoretical; check old CERT advisories, 
attackers have been exploiting DNS cache vulnerabilities in home/soho 
routers/WAPs/firewalls for a while now.

So a DNS vulnerability that would make it easy to poison the resolvers of 
very large numbers of clients is a huge deal.


I agree that DNSSEC is the real solution.  I also think that making it 
easy (or even possible) to sandbox the browsers is a real solution.  I 
think that using strong crypto everywhere and making fine-grained 
capabilities and MAC systems ubiquitous is also a real solution.

But that's just not the reality we have today.  And having the reality we 
have today, it's absolutely critical to make the existing, insecure DNS 
system as secure as it can be.


  -Jason

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