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Massive, Coordinated Patch To the DNS Released
tkrabec alerts us to a CERT advisory announcing a massive, multi-vendor DNS patch released today. Early this year, researcher Dan Kaminsky discovered a basic flaw in the DNS that could allow attackers easily to compromise any name server; it also affects clients. Kaminsky has been working in secret with a large group of vendors on a coordinated patch. Eighty-one vendors are listed in the CERT advisory (DOC). Here is the executive overview (PDF) to the CERT advisory — text reproduced at the link above. There's a podcast interview with Dan Kaminsky too. His site has a DNS checker tool on the top page. "The issue is extremely serious, and all name servers should be patched as soon as possible. Updates are also being released for a variety of other platforms since this is a problem with the DNS protocol itself, not a specific implementation. The good news is this is a really strange situation where the fix does not [immediately] reveal the vulnerability and reverse engineering isn't directly possible."
http://www.doxpara.com/
Your name server, at 65.24.7.3, appears vulnerable to DNS Cache Poisoning.
Sweet!
If you don't understand that, you don't need to care.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
Here everyone, install this patch to your Unix/Linux DNS servers that was conceived of on the Microsoft campus.
While if true, one should be expedient to fix it, one should also be careful to verify that this is true.
I used to run a DNS hosting company. Fortunately, this error only affects caching resolvers, since it is yet another example of cache poisoning. There have been (and continue to be) hundreds of cache poisoning exploits over the years. This one is fairly technical and would require significant expertise to execute in a timeframe (ie: before everyone patches up) to cause harm. I don't know about you,but if someone started flooding my servers with thousands of response regords in hopes of guessing a transaction ID, my iptables config would block them in a heartbeat.
this is not the kind of security problem that should cause people's heart to skip a beat. your average malware worm is much worse.
dan has written an article on a javascript attack that can compromise a home router.... that's probably far worse - in terms of real damage (ie: bot creation, personal data stolen)
in sum... run yum update.... then don't worry about it.
Note that DJBDNS (and derivatives) are not affected, since it uses randmoized source ports for DNS resolving.
My blog
FTA Update: Dan just released a "DNS Checker" on his site Doxpara.com to see if you are vulnerable to the issue.
in other news
Sooooooo, Im supposed to run a random file on my network to check an unknown DNS issue...this just reminds me all too much of those "download our program to fix all your antispyware issues" alerts.
And finally the obligatory profit usage:
1. Find a vulerability
2. Dont tell anyone what said vulnerability is.
3. Release malware in the form of a "Patch" to "Fix" the issue exploiting thousands of servers.
4. ???
5. PROFIT!
CS: It is all sink or swim...oh and did I mention there are sharks in that water?
"An attacker with the ability to conduct a successful cache poisoning attack can cause a nameserver's clients to contact the incorrect, and possibly malicious, hosts for particular services. Consequently, web traffic, email, and other important network data can be redirected to systems under the attacker's control." Too bad the fix doesn't 'Cure' the problem. It only makes it more difficult. "ISC is providing patches for BIND 9.3, 9.4 and 9.5" - Thank the Internet gods.
This is utterly serious! And only a matter of time before attackers compromise DNS on servers and/or clients.
The good news is this is a really strange situation where the fix does not immediate reveal the vulnerability and reverse engineering isn't directly possible.
And wow! Great news! There's a very critical flaw over the entire Internet name-to-IP infrastructure. But don't bother, it will take time before the bad guys find what we fixed...
From the summary-
His DNS tester is submitting a DNS check that it knows will be relayed, and then monitoring if the upstream check (it is intentionally doing lookups against a DNS server it controls) consistently uses the same source port. If it does, hypothetically an attacker could send "response" packets in concert with the original request, poisoning the cache.
I would guess that the patch makes the DNS server randomize the nonce when relaying DNS requests.
I know nothing about this, but that's my super-l33t-hacker assumption from looking at it for 10 seconds.
Because it isn't 1912, and we aren't on the Titanic. They can say with reasonable confidence that it's difficult to find the underlying issue, but nothing is hackproof, or sinkproof, or lameproof.
- oZ
// i am here.
I'm (sort of) a native German speaker, in which "DNA" is abbreviated "DNS" ("DesoxyribonukleinsÃure" with "sÃure" being "acid").
Needless to say, my first impression of the headline was way more futuristic than what is there.
Power corrupts the few, while weakness corrupts the many.
Here is the CERT advisory in a readable format.
http://www.kb.cert.org/vuls/id/800113
BTW, did they hold this for a Microsoft patch Tuesday?
-molo
Using your sig line to advertise for friends is lame.
It's reasonably obvious from the CERT advisory how an attack would work. The CERT advisory tells us that the vulnerable systems are ones where the 16-bit DNS transaction ID and the 16-bit port number for a transaction are not randomly chosen. The CERT advisory also tells us that the attacker must be able to spoof IP addresses, that is, they must not be behind some ISP with egress filtering. CERT also tells us that it's a DNS poisoning attack.
So it looks like a form of this attack documented in 2003 at "Cache Poisoning using DNS Transaction ID Prediction". Back in 2003, it took a large number of packets to make this attack work, and even then it wasn't reliable. But there may be a more cost-effective attack strategy if you know how the DNS server assigns transaction numbers and ports.
The fundamental problem comes from 1) the fact that source IP addresses can be forged, and 2) the DNS transaction ID, at 16 bits, is far too short to be considered a useful random key. Any key with security implications should be at least 64 bits and be generated by a crypto-grade random number generator.
Debian released 3 advisories:
bind9:
http://www.debian.org/security/2008/dsa-1603
bind8:
http://www.debian.org/security/2008/dsa-1604
glibc:
http://www.debian.org/security/2008/dsa-1605
Bind9 now contains a port randomization, which can require firewall rule changes.
Bind8 is now considered deprecated and the advisory recommends upgrading to bind9. There is no patch for bind8.
The glibc stub resolver is also vulnerable, and there is no patch yet. The recommended workaround is to install bind9 as a caching resolver and point /etc/resolv.conf at localhost.
In short, this is a big mess.
-molo
Using your sig line to advertise for friends is lame.
Attention all DJB software fans, here's another chance to champion the superiority of DJB's software. Don't forget to include positive commentary on the licensing and patch status.
Thanks!
...is to sign the root and deploy DNSSEC.
Unfortunately that's politically non-expedient. But now that this vulnerability is out there, maybe the political will can at last materialize.
The second-best solution is to deploy DNSSEC using DNSSEC Lookaside Validation (which means you get trust anchors from some other known site, not from the root zone). And that's available now.
The worst thing about DNSSEC is it's too damn complicated at present; there needs to be the equivalent of "one-click" zone signing. ISC (and others) are working on getting us closer to that.
The third-best solution is what's been done today. We just made it a lot harder to exploit the vulnerability--typically about 16000 times harder, depending on your configuration. There's a difference between "harder" and "impossible" though.
Recommendation is more CERTS, as they will help with the sand breath.
Get thee glass eyes, and, like a scurvy politician, seem to see things thou dost not.--King Lear
This is from the advisory.
Filter traffic at network perimeters
Because the ability to spoof IP addresses is necessary to conduct
these attacks, administrators should take care to filter spoofedaddresses at the network perimeter. IETF Request for Comments(RFC)
documents RFC 2827, RFC 3704, and RFC 3013 describe best currentpractices (BCPs) for implementing this defense. It is important to
understand your network's configuration and service requirements
before deciding what changes are appropriate.
So...is this REALLY that serious? Is anyone NOT already doing this? I'm incredibly skeptical of big, sensational security alerts like this.
... because djb recognized the vulnerability. it's even documented as such: http://cr.yp.to/djbdns/dns_random.html
djbdns consists of a separate server (tinydns) and resolver (dnscache).
Don't piss off The Angry Economist
What a terrible summary. What would be really useful and news worthy would be a link to a web page with some information about the vulnerability. The links in the summary included: 1) a WORD DOCUMENT? WTF? 2) a PDF, 3) a podcast?? WTF? and 4) a link to a slashdotted DNS checker. How about a link to the CERT vulnerability web page which describes the problem?
http://www.kb.cert.org/vuls/id/800113
Now THAT would have been much more useful. Do people who work as sysadmins actually have time to sit around listening to a podcast? Especially when there are DNS servers to patch?
Google Dan Kaminsky and come back and talk.
"I'd rather be a lightning rod than a seismometer." -Ken Kesey
Its a problem in the protocol. So the only systems that would not be vulnerable are those that did -not- follow the specs. Guess Windows is safe, since Microsoft never follows the specs :)
I help admin one of the larger DNS systems (90,000+ zones) and our initial testing of the patched BIND showed it having half the performance of prior versions. That prompted us to very quickly replace all BIND caching servers with something else. We had already replaced authoritative services with something else because of BIND's lackluster performance. 3+ hours to load zones on reboot is quite frankly ridiculous. We really had no choice. Microsoft said they were going to open their mouths on a certain date, and we had a massive time crunch. We can't be the only company that simply had to ditch BIND. And I can't say I'm sorry to see it go. I'm sure mister Vixie is a great guy, but his domain name service is, and always has been complete garbage.
For every annoying gentoo user, are three even more annoying anti-gentoo crybabies. Take Yosh from #Gimp for example.
Everybody else is being patched to the level of security that we djbdns users have always had. Not to be *too* smug, of course.
Don't piss off The Angry Economist
Do I trust it? I don't know. Tell me the facts. The sheer quantity of internet shenanigans going on of late makes me suspicious. This sounds like they're patching for a remote root exploit, but a protocol issue won't do that. DNS poisons? What is it then?
They're making us patch everything, and aren't telling us what it does. These are my systems, and you're going to tell me precisely what's going on before any of your code gets to run.
from http://www.kb.cert.org/vuls/id/800113: "The DNS protocol specification includes a transaction ID field of 16 bits. If the specification is correctly implemented and the transaction ID is randomly selected with a strong random number generator, an attacker will require, on average, 32,768 attempts to successfully predict the ID."
Just put the real seed back into the code.
obrant: and who the frak releases advisories in DOC format in the 21st century?
The reason girls and Windows users don't understand UNIX is because all the documentation is in Man files.
Read the diffs to BIND and work it out. They're only hiding things from the bad guys to give you a few more hours window to implement the patches.. :)
...an Englishman in London.
The advisory indicated two different scenarios and discussed specifically that section 2.2 (the advisory did not call it out by name). the flaw Kaminsky found he claims, is still possible even while addressing transaction ID guessing.
It is known for years that it's less secure, if you don't use proper randomization. Now it turns out, it's _really_ insecure. Duh.
New things are always on the horizon
The exploit is trivial to figure out - if a caching DNS server has recursion enabled, and also sends the outgoing DNS queries to the authoritative servers over a fixed (or predictable) UDP port, you can just send forged UDP responses together with your recursive DNS query.
The bogus response will be cached and will affect other users of the DNS server.
The attacker also needs to also guess the transaction ID (16-bit value), but they can send multiple bogus UDP responses with different transaction IDs.
Also, vulnerable implementations may generate transaction IDs in a predictable way, so the attacker can obtain the current state of the PRNG by generating a recursive DNS query to DNS zone under attacker's control.
Such an attack cannot be performed from a typical home broadband connection, as most ISPs will not route packets originating from IP addresses not allocated by the ISP.
The attacker needs to be in control over the routing/egress filtering within his AS (e.g. an enterprise-level Internet service).
throw new SuccessException("Sig read successfully");
" Everybody else is being patched to the level of security that we djbdns users have always had. Not to be *too* smug, of course."
Bingo.
If we were being smug we'd say something like "what do you expect when cert advisories are published as doc files?".
Need Mercedes parts ?
A good way to find out is to go directly to the CERT web site and have a look at the vulnerability note they're talking about. Link here, if you trust me =) http://www.kb.cert.org/vuls/id/484649/
Do not mock my vision of impractical footwear
If you don't understand that, you don't need to care.
What's funny is that the CERT advisory gives Dan Bernstein credit for the work around, which he came up with over 7 years ago.
1. DNS (well, UDP protocols in general) problems have been known for ages. This is nothing new, it's just new because so much drama has been created. There is a reason why certain counter-measures have already been implemented in DNS software. Never mind that noone is using them because it requires effort.
2. So much focus has been put on "phishing". I'd like someone to explain me how phishers are going to forge certificates and get sensitive info? Sure, I'll get bogus IP for the website I want to visit, but unless phishers manage to create valid certificate for gmail.com (for example), I'll get a nice warning box. Which is the same shit as what is happening now, when you go to a phishing website. Those who click "Ok" on every prompt will still get fucked, those who check errors will still not be tricked. Nothing changes.
3. Security became a joke when advisories like "Man in the middle attack allows attackers to steal Myspace passwords" started showing up on first pages of various news outlets.
From this posting: "DJB was right. All those years ago, Dan J. Bernstein was right: Source Port Randomization should be standard on every name server in production use."
But I'm sure his acting like a jerk still means that nobody should ever take his criticisms of software design seriously. Heck, the BIND folks didn't, and it's not like people are going to stop using BIND.
Laws do not persuade just because they threaten. --Seneca
Reportedly, djb wears all black, not all-aluminum. If I were you, I'd start wearing all black also.
Don't piss off The Angry Economist
These are my systems, and you're going to tell me precisely what's going on before any of your code gets to run.
So don't trust it. You're already running their code and you seemed quite happy to do so without them telling you precisely what potential bugs could exist. Why get so demanding now?
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
I understand that djb draws a lot of flack for being a legendarily caustic personality; I'm just a little bitter that the sensible parts of his advice get ignored as well. DNSSEC is an implausible mess with a single point of failure, IPv6 migration is a joke, and DNS without source port randomization is vulnerable to spoofing. Despite his other, wackier beliefs (a new format for FTP listings! a new format for mail transfer! blasting mail across parallel connections instead of one connection per server just because I like it that way!), there's some important stuff in there.
Laws do not persuade just because they threaten. --Seneca