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Kaminsky's DNS Attack Disclosed, Then Pulled
An anonymous reader writes "Reverse engineering expert Halver Flake has recently mused on Dan Kaminsky's DNS vulnerability. Apparently his musings were close enough to the mark to cause one of the Matasano team, who apparently already knew of the attack, to publish the details on the Matasano blog in a post entitled 'Reliable DNS Forgery in 2008.' The blog post has since been pulled, but evidence of it exists on Google and elsewhere. It appears only a matter of time now before the full details leak."
Reader Time out contributes a link to coverage on ZDNet as well.
http://demosthen.es/post/43048623/matasano-briefly-had-a-post-up-about-the-dns-flaw
Doxpara.com, the blog of Dan Kaminsky who first discovered the vulnerability, has also been updated.
In case of Slashdotting, here's the full update;
Patch. Today. Now. Yes, stay late. Yes, forward to OpenDNS if you have to. (Theyâ(TM)re ready for your traffic.) Thank you to the many of you who already have.
I got this much and am working on extracting more but hitting a roadblock.
Matasano Chargen  Blog Archive  Reliable DNS Forgery in 2008: Kaminskyâ(TM)s Discovery. Well the cat is finally out of the bag. I suspected this was how the
the cat is out of the bag. Yes, Halvar Flake figured out the flaw Dan ... One of them involves mucking about with the QID in DNS packets and
and the other requires you to know the Deep Magic. First, QIDs
Bobâ(TM)s a resolver and Alice is a content DNS server. Bob asks Alice for the address of WWW.VICTIM.COM. The answer is 1.2.3.4.
Mallory would like the answer to be 6.6.6.0. It is a (now not) secret shame of mine
that for a great deal of my career, creating and sending packets was, to me, Deep Magic. Then it became part of my
job, and I learned that it is surprisingly trivial. So put aside the idea that forging IP packets is the hard part
of poisoning DNS. If Iâ(TM)m Mallory and Iâ(TM)m attacking Bob, how can he distinguish my packets
from Aliceâ(TM)s? Because I canâ(TM)t see the QID in his request, and the QID in my response
wonâ(TM)t match. The QID is the only thing protecting the DNS from
Mallory (me). QID attacks began in the olden days, when BIND simply incremented the QID
with every query response. If you can remember 1995,
hereâ(TM)s a workable DNS attack. Think fast: 9372 + 1. Did you get 9372, or even miss and get 9373?
You win, Alice loses. Mallory sends a constant stream of DNS responses for WWW.VICTIM.COM.
All are quietly discarded â"- until Mallory gets Bob to query for
WWW.VICTIM.COM. If Malloryâ(TM)s response gets to your computer before the
legitimate response arrives from your ISPâ(TM)s name server, you will be redirected where
where Mallory tells you youâ(TM)re going
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I still have it in my RSS reader. I sent the others in my security group the link referenced in the feed, but it ended up with a 404 page. I thought it was a blip on their server, but now I see they retracted the post. It's a bit late for that, as I'm sure I'm not the only one who subscribes to their blog.
Just another example of how you can't erase knowledge once it's been disseminated.
BTW, the method of attack really is quite clever. And pretty trivial.
"This calls for a very special blend of psychology and extreme violence" - Vyvyan "The Young Ones"
and running around the room screaming that the sky is falling.
An article over at the Register, states that this 'vulnerability' was discovered three years ago by Ian Green and published in a paper he wrote for the SANS Institute. While Kaminsky does deserve some credit for his organizational skills in getting people to act on this, that's about as far as his role goes. Since this has been known about for three years and we haven't seen anything 'in the wild' -until now that the media bandwagon is careening downhill on fire- just goes to show how hard this is to exploit.
Sig this!
...is not just that you can race legit DNS servers for legit queries, is that you can request recursive resolution for bullshit DNS servers, while submitting fake answers WITH malicious informational records that let you poison second-level domains. So by requesting xxjk3j.google.com while submitting your own coolly crafted answer, you can make the victim DNS use YOUR DNS as authoritative for the future google.com replies.
THAT is the significance of the attack. THAT is what matasano pulled.
Rudd-O - http://rudd-o.com/
That is not it. What you describe would have worked a decade ago, but not today.
Mod parent down for not understanding the vulnerability.
That is different - that's just advertising and silliness off the way the wildcard matching works for WHOIS.
The issue is when you can force the target to resolve blah.google.com to poison www.google.com and then include a glue response for www. in with the blah. response which is then accepted because the domains match at to the right of that level.
For those who want to read this here is the url. http://blogs.buanzo.com.ar/2008/07/matasano-kaminsky-dns-forgery.html
Alright, so I'm not even someone who does DNS/networking stuff even for a hobby (just a math grad who skimmed the RFCs once or twice) so if I can figure this out from what's up now then any competent bad guy can as well.
Anyway my guess is that it involves a combination of the birthday attack and the request for multiple nonexistant nameservers. That is as the attacker you trick poisontarget.com into trying to resolve the following locations.
AAA.google.com ....
AAB.google.com
XXX.google.com
Now you forge a single response packet that works for all of these requests and send many different copies with different TXIDs. Thus to succeed you need only hit ONE of the TXIDs used in the real requests.
In these forged responses you also have a forged glue record (as suggested in some of the links) which gives you control of lookups for all of google.com at poisiontarget.com after a single success.
Then again maybe I missed something basic which means this doesn't work.
If you liked this thought maybe you would find my blog nice too:
Sorry for the threadjack (thank you for ensuring that 99% of the slashdot crowd is looking intently upon the thread), but here's soem relevant info that should be near the top.
As of the time of my post, the original text of the article (at least I -THINK- it's the original text) is available here
Slashdotters may resume the lesbian thread now, thank you for your time (hope I didn't kill anyones chubber).
y ecopeland
0.
The cat is out of the bag. Yes, Halvar Flake figured out the flaw Dan Kaminsky will announce at Black Hat.
1.
Pretend for the moment that you know only the basic function of DNS -- that it translates WWW.VICTIM.COM into 1.2.3.4. The code that does this is called a resolver. Each time the resolver contacts the DNS to translate names to addresses, it creates a packet called a query. The exchange of packets is called a transaction. Since the number of packets flying about on the internet requires scientific notation to express, you can imagine there has to be some way of not mixing them up.
Bob goes to to a deli, to get a sandwich. Bob walks up to the counter, takes a pointy ticket from a round red dispenser. The ticket has a number on it. This will be Bob's unique identifier for his sandwich acquisition transaction. Note that the number will probably be used twice -- once when he is called to the counter to place his order and again when he's called back to get his sandwich. If you're wondering, Bob likes ham on rye with no onions.
If you've got this, you have the concept of transaction IDs, which are numbers assigned to keep different transactions in order. Conveniently, the first sixteen bits of a DNS packet is just such a unique identifier. It's called a query id (QID). And with the efficiency of the deli, the QID is used for multiple transactions.
2.
Until very recently, there were two basic classes of DNS vulnerabilities. One of them involves mucking about with the QID in DNS packets and the other requires you to know the Deep Magic.
First, QIDs.
Bob's a resolver and Alice is a content DNS server. Bob asks Alice for the address of WWW.VICTIM.COM. The answer is 1.2.3.4. Mallory would like the answer to be 6.6.6.0.
It is a (now not) secret shame of mine that for a great deal of my career, creating and sending packets was, to me, Deep Magic. Then it became part of my job, and I learned that it is surprisingly trivial. So put aside the idea that forging IP packets is the hard part of poisoning DNS. If I'm Mallory and I'm attacking Bob, how can he distinguish my packets from Alice's? Because I can't see the QID in his request, and the QID in my response won't match. The QID is the only thing protecting the DNS from Mallory (me).
QID attacks began in the olden days, when BIND simply incremented the QID with every query response. If you can remember 1995, here's a workable DNS attack. Think fast: 9372 + 1. Did you get 9372, or even miss and get 9373? You win, Alice loses. Mallory sends a constant stream of DNS responses for WWW.VICTIM.COM. All are quietly discarded --- until Mallory gets Bob to query for WWW.VICTIM.COM. If Mallory's response gets to your computer before the legitimate response arrives from your ISP's name server, you will be redirected where Mallory tells you you're going.
Obvious fix: you want the QID be randomly generated. Now Alice and Mallory are in a race. Alice sees Bob's request and knows the QID. Mallory has to guess it. The first one to land a packet with the correct QID wins. Randomized QIDs give Alice a big advantage in this race.
But there's a bunch more problems here:
*
If you convince Bob to ask Alice the same question 1000 times all at once, and Bob uses a different QID for each packet, you made the race 1000 times easier for Mallory to win.
*
If Bob uses a crappy random number generator, Mallory can get Bob to ask for names she controls, like WWW.EVIL.COM, and watch how the QIDs bounce around; eventually, she'll break the RNG and be able to predict its outputs.
*
16 bits just isn't big enough to provide real security at the traffic rates we deal with in 2008.
Your computer's resolver is probably a stub. Which means it won't really save the response. You
See http://thefrozenfire.com/data/dnspoisoning.html for the whole deal, without the pastebin RAW formatting ;)
I've posted up the full text of the article, and it'll stay up, assuming lighty doesn't fail miserably on me. http://www.jbip.net/content/text-mantasanos-article-detais-kaminskys-dns-attack
Well that would work, although since VeriSign's "SiteFinder" stunt some DNS servers (including bind) have an option to denote a zone as being "delegation only" zone, which would stop this attack from working. I don't know how widespread use of this option would be, though.
Assuming it's not, than poisoning .com would make it much easier: with one successful attack you could poison dozens of popular domains.
What could be interesting is combining this attack with zombies -- that way you don't need to trick a user into visiting a site with your links on it, you can just spam the ISPs name servers from one (or several) of their clients until you finally get lucky. Even better, the larger the ISP the more likely one of your randomly infected zombies will be within their network.
You could also have the ISP name server do some queries against a DNS server you control so you can look for any patterns in the query IDs and source ports, and use that information to narrow the search space for your actual attack.
I'm not really seeing any solutions to these attacks that don't simply turn it into an easy DoS. Fun times are ahead!
It's a hard call in some cases. There's an argument that most (any?) multihomed customers should be able to send packets asymmetrically. That said, nobody with even half a brain should be running a NAS/LNS with single-homed customers WITHOUT RPF, although the (admittedly, in .au) number of people i've crossed paths with who are doing it wrong is staggering.
Conversely, if i'm peering with you and six other guys, and happen to be carrying traffic to your network (but not advertising a route back to some of MY peers, for e.g. traffic engineering reasons) across a given link, you have no business dropping that traffic.
RPF is a good idea, but it kind of breaks one of the more fundamental paradigms of the Internets.
You're doing it wrong.
BIND supports DNSSec; DNSSec is about cryptographically signing your DNS entries so resolvers know that the response they got was from the legitimate authoritative server for the domain.
This means that it's not something you can "just patch" - it actually requires people to do some work, which means it'll take a very long time to actually be widely deployed (by "people" I mean "every single person who administers one or more DNS zones"). You also have the usual problems with crypto, i.e. establishing a "web of trust" (it's all very well if records under google.com are signed, but how do you know they're signed by Google?).
Solvable problems, but inertia is a powerful force.
And here's tptacek's grovelling retraction (which followed his drunken rant on DD at the weekend which firmly argued the public have the right to know and trying to stop public discussion is Wrong). I fear the Matasanto crew and Halvar are about to discover what happens when geeks allow their 'satiable curtiosity to run away with their sense of ethics. Halvar in particular posted a long self-justification (with mathematical functions!) trying to prove that public dissemination before BlackHat would be a good thing.
=== BEGIN PTACEK ===
"Earlier today, a security researcher posted their hypothesis regarding Dan Kaminskyâ(TM)s DNS finding. Shortly afterwards, when the story began getting traction, a post appeared on our blog about that hypothesis. It was posted in error. We regret that it ran. We removed it from the blog as soon as we saw it. Unfortunately, it takes only seconds for Internet publications to spread.
We dropped the ball here.
Since alerting the Internet earlier in July about the upcoming announcement of his finding, Dan has consistently urged DNS operators to patch their servers. We confirmed the severity of the problem then and, by inadvertantly verifying another researcherâ(TM)s results today, reconfirm it today. This is a serious problem, it merits immediate attention, and the extra attention itâ(TM)s receiving today may increase the threat. The Internet needs to patch this problem ASAP.
Dan told me about his finding personally, in order to help ensure widespread patching before further details were announced at the upcoming Black Hat conference. We chose to have a story locked and loaded for that presentation, or for any other confirmed public disclosure. On a personal level, I regret this as well.
Dan did phenomenal work on this research. It was impossible to talk to him today and not know that he was sincere about coordinating a graceful disclosure and fix for the problem. That I helped detract from that work is painful both personally and professionally, and I apologize to Dan for the way this played out.
Thomas Ptacek
Principal, Matasano Security
Jul 21, 2008
Nope, apparently it has to be a subdomain of the domain you're attacking, due to bailwick filtering - see, for example this post. If it wasn't for bailwick filtering, an attacker could just launch a request to a DNS server they controlled and avoid having to guess anything. (Supposedly, this used to work, though.)