Paul Vixie Responds To DNS Hole Skeptics 147
syncro writes "The recent massive, multi-vendor DNS patch advisory related to DNS cache poisoning vulnerability, discovered by Dan Kaminsky, has made headline news. However, the secretive preparation prior to the July 8th announcement and hype around a promised full disclosure of the flaw by Dan on August 7 at the Black Hat conference has generated a fair amount of backlash and skepticism among hackers and the security research community. In a post on CircleID, Paul Vixie offers his usual straightforward response to these allegations. The conclusion: 'Please do the following. First, take the advisory seriously — we're not just a bunch of n00b alarmists, if we tell you your DNS house is on fire, and we hand you a fire hose, take it. Second, take Secure DNS seriously, even though there are intractable problems in its business and governance model — deploy it locally and push on your vendors for the tools and services you need. Third, stop complaining, we've all got a lot of work to do by August 7 and it's a little silly to spend any time arguing when we need to be patching.'"
Re:I'm not worried (Score:3, Informative)
216.34.181.48
Re:What is Secure DNS (Score:5, Informative)
"The Domain Name System Security Extensions (DNSSEC) are a suite of IETF specifications for securing certain kinds of information provided by the Domain Name System (DNS) as used on Internet Protocol (IP) networks. It is a set of extensions to DNS which provide to DNS clients (resolvers):
* Origin authentication of DNS data.
* Data integrity.
* Authenticated denial of existence."
http://en.wikipedia.org/wiki/DNSSEC
Re:What is Secure DNS (Score:1, Informative)
Secure DNS is a protocol which uses cryptographic signatures on DNS records to prevent DNS spoofing and other unauthorized manipulations. It has some problems which are mostly a result of DNS being a UDP protocol, which, for performance reasons, can't have long handshakes or cryptographic calculations on the server side.
Re:Unfortunately, what else is new? (Score:4, Informative)
Randomizing UDP source ports does not solve the problem, it only makes it more difficult to impersonate the responding DNS server. Secure DNS makes this kind of impersonation impossible, or at least allows us to bask in the warm glow of impossible.
The DJB vs BIND thing is an illusion. Whatever everyone agrees is the best implementation should win and I doubt that Paul Vixie or anyone else at ISC thinks differently.
But it has become abundantly clear to me that DJB and his minions (of which I assume you are one) have failed to matter in most ways, not because of your ideas, but because of the brusque, immature manner in which those ideas are submitted for consideration, outside the standards committees which have served the Internet well for 30 years.
So its not the same flaw? (Score:4, Informative)
Q: "This is the same attack as described way back in
A: No, it's not.
When Dan Kaminsky states in his blog. [doxpara.com]
"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."
and
" 1) It's a bug in many platforms 2) It's the exact same bug in many platforms (design bugs, they are a pain) " How is this not the same flaw DJB described?
Re:So its not the same flaw? (Score:5, Informative)
You are looking at two separate issues. The flaw Kaminsky found is apparently a newly discovered design flaw that makes DNS forging easy even with todays, unpatched DNS servers. In the advisory, they discussed previous problems with generating the transactionID to explain the problem and point out that what Dan found is not something already known (alot of people missed that very obvious point).
The second seperate, issue is UDP source port randomization. That is what Kaminsky was referring to DJB's solution. Kaminsky's assertion is that UDP source port is a good development practice which DJB incorporated into his DNS server.
Bear in mind that UDP source port generation doesn't solve the underlying problem, it simply makes blind DNS forging more difficult because now an attacker has to guess both a pseudo random transaction ID and a pseudo random UDP source port number. Alot of DNS servers and OS, simply picked source port numbers incrementally or in the case of a DNS server, re-used the some one over and over.
I don't know hom much more difficult DNS forging will be by randomizing the UDP source port numbers. The additional keyspace is (2^16-1023) and you can probably divide that in half again. But it's better then nothing and probably provides enough time (the time it would take an attacker to blindly guess the transactionID and UDP source port number) for the actual response to hit the DNS server. In DNS, the first response wins.
Re:So its not the same flaw? (Score:4, Informative)
Re:The back-biting is shameful (Score:4, Informative)
It was because of forethought of one man, DJB (Bernstein).
A simple test to run (Score:5, Informative)
In a comment to a question I posted for the CircleID article, Paul Vixie posted a nice and simple test that people can run to see how vulnerable they are:
FAIR or GOOD means you're ok, but POOR (which is the result I got) means you should be worried.
Diffusion of Responsibility (Score:4, Informative)
You're looking for Diffusion of Responsibility [wikipedia.org], made famous by the incident in which Kitty Genovese was murdered within earshot of a whole bunch of people, all of whom thought "damnit, someone should do something about this!"
Re:A simple test to run (Score:4, Informative)
Many older named.conf configs have "query-source port 53;". While this is nice for firewalls to open up DNS traffic (assuming replies from source udp/53 to destination udp/53 (your query port) are always safe), it makes it easy to exploit.
This must be removed and those nameserver restarted. I had to do this with all of my servers, otherwise all queries come from the same port (53). Complain to your ISP if you find this to be the case with their DNS servers and in the meantime use some other DNS servers.
My two local Comcast resolves show "Poor" as the ports they use only have a standard deviation of 130-150, which I guess is assumed to be far too obvious and easy to keep bombarding.
Second, your NAT router may be de-randomizing your DNS queries if you run a resolver at home, and taking your random ports and putting them in order starting at 1024 (or something similar).
My own local/internal DNS servers shows as a std dev of 9 since my PAT router is de-randomizing the external ports. I'll be replacing my PAT router.
Third, your NAT router may be your DNS resolver and may not be using random source ports.
Re:Why is Vixie recommending it? (Score:2, Informative)
However, we're past the point of flag days in Secure DNS. A valid configuration today will remain valid in the future. And this time we're finally seeing investment by CCTLDs, and some interest from banks. But we're not going to convince ICANN and/or USG to take the risks and reach for these rewards unless there's a significant installed base. This makes Secure DNS a bit like IPv6 in that there's a significant last-mover advantage. That's why I'm singing this song on slashdot rather than businessweek. New stuff with rough edges and not a lot of immediate benefit has to come to the technical community to get born.
Re:Why is Vixie recommending it? (Score:2, Informative)
you can't be serious. i resigned as chairman of nominum's board back in 2002 or so. i have no position there. they stopped working on BIND9 at about that same time. let the record show that i am grateful to nominum's then-shareholders for their significant donation of code and effort to BIND9 9.0.0, which went well beyond what ISC paid them for.
it's an educated bet. the restarts to the Secure DNS protocol development effort over the last 13 years have been because we could not find a backward compatible way out of some mess we'd painted ourselves into. in that time EDNS has matured, providing a negotiation framework. in that time, NSEC3 was added, without invalidating any existing endpoint or implementation or data pattern. i really think we're going to be ok.
show me what you're investing your time and effort in that solves the same set of problems better, or solves the truer more underlying problems better, and we'll talk.