The Internet engineering community is grappling with what to do about a serious flaw in the DNS discovered mid-year, and the ongoing debate brings to mind a famous quotation from Voltaire: "The perfect is the enemy of the good."
At issue is whether the group should use its resources to encourage DNS registries, ISPs and enterprises to upgrade to the ultimate DNS security solution known as DNSSEC; or whether it should tweak the DNS protocols to address the so-called Kaminsky bug as an interim step. The issue is being debated at a meeting of the IETF, the Internet's leading standards body, being held here this week.
In July, security researcher Dan Kaminsky discovered a DNS bug that allows for cache poisoning attacks, where a hacker redirects traffic from a legitimate Web site to a fake one without the user knowing. With DNSSEC, the IETF already has a solution to the Kaminsky problem and other known DNS vulnerabilities. However, DNSSEC hasn't been widely deployed, although it has been under development for more than a decade.
DNSSEC prevents hackers from hijacking Web traffic and redirecting it to bogus sites. The Internet standard prevents spoofing attacks by allowing Web sites to verify their domain names and corresponding IP addresses using digital signatures and public-key encryption.
The problem is that DNSSEC prevents Kaminsky attacks only when it is fully deployed across the Internet -- from the DNS root zone at the top of the DNS heirarchy down to individual top-level domains, such as .com and .net. Until then, Web sites remain vulnerable to Kaminsky-style attacks.
That's why some IETF participants are urging immediate action to address the Kaminsky bug, while others are hoping to use the publicity surrounding the discovery of the Kaminsky bug to promote DNSSEC deployment. "The open question is whether there are other measures we can take as operators of the DNS to improve forgery resilience, or are there changes to the DNS protocols that we should be making that are an interim step that aren't all the way to DNSSEC," explains Andrew Sullivan, co-chair of the IETF's DNS Extensions working group, which is discussing the matter. The working group is split on which direction to take. "We can't tell yet which way it will go," says Olafur Gudmundsson, the other co-chair of the group.
In recent weeks, IETF participants have submitted five documents to the DNS Extensions working group with proposed changes to DNS that would prevent Kaminsky-style attacks. "We've been trying to condense the proposals down to the working group to show what each of the changes would be, how they would help the situation, what the operational costs would be and what would break as a result of the changes," Gudmundsson says. "It's too early to tell if the group is going to coalesce around one of these proposals."