Vendors form alliance to fix DNS poisoning flaw
Giving the good guys a headstart
An alliance of software makers and network-hardware vendors announced on Tuesday that they had banded together to fix a fundamental flaw in the design of the internet's address system.
The vulnerability in the domain name system (DNS) - the distributed database that matches a host and domain name with the numerical address of a computer server - could give an attacker the ability to replace the addresses of popular websites with that of a malicious server, said Dan Kaminsky, director of penetration testing for security firm IOActive. Kaminsky found the flaw when he was doing non-security research on the domain name system (DNS) more than six months ago.
"It is a fundamental issue affecting the design," Kaminsky said. "Because the system is behaving exactly like it is supposed to behave, the same bug will show up in vendor after vendor after vendor. This one bug affected not just Microsoft ... not just Cisco, but everyone."
On Tuesday, a number of software and network-hardware vendors released patches for their products. On its regularly scheduled patch day, Microsoft released updates for Windows 2000, Windows XP and Windows Server 2003 to mitigate the issue, which the company ranked an important vulnerability, its second highest grade of severity. Internet Software Consortium, the group responsible for the development of the popular Berkeley Internet Name Domain (BIND) server, also released a patch, confirming that its software contained the vulnerability. Both Cisco and Juniper also acknowledged flawed systems.
Vendors have also provided the fix to certain large clients. Yahoo will be upgrading its name servers from BIND 8 to the latest version of BIND 9, the Internet Software Consortium stated during the conference call. Internet service provider Comcast has already patched its servers for the issue, according to internet infrastructure firm Nominum. Finally, the Computer Emergency Response Team (CERT) Coordination Center has contacted some other nation's response groups to inform them of the problem.
For the most part, however, internet service providers and companies each received the fix on Tuesday, said Sandy Wilbourn, vice president of engineering at Nominum. The goal: To have every major service provider and company apply their software patches in 30 days.
For that reason, don't expect immediate action, Wilbourn said.
"For key customers on our network, we have made a special effort to get them an early release to help solve this problem, and a number of them have finished deployment," he said. "But the nature of this patch is that we wanted to get the vendor side covered and then have deployment over the next 30 days. Anyone that is not patched by today or tomorrow is not doing anything wrong."
The domain-name system (DNS) has been a popular way to attack the internet in the past - it's an ill-kept secret that the DNS system is insecure. The way that many software applications, such as browsers, handle DNS requests has opened up users to attack. Microsoft has fixed a few vulnerabilities in the way Windows handles domain names - issues that could have lead to easier eavesdropping or simpler phishing attacks.
While Kaminsky and other internet protocol experts who discussed the issue on Tuesday would not give specific details of the flaw, a CERT vulnerability note described the issue as a combination of DNS weaknesses. While the CERT note referred to the issue with a single Common Vulnerabilities and Exposures (CVE) identifier, Microsoft, in its security bulletin, referred to the issue as two flaws: a DNS socket entropy vulnerability and a DNS cache poisoning vulnerability.
The CERT vulnerability note describing the issue lists more than 90 software developers and network equipment vendors that may be affected by the issue.
The coordinated response was anything but assured six months ago.
Kaminsky began contacting a small group of domain-name system (DNS) experts and software vendors, resulting in a brainstorming session at the end of March.
On March 31, sixteen internet and security experts met on Microsoft's campus in Redmond, Washington. The agenda was simple, according to Kaminsky: Decide if they properly understood the problem, figure out how to fix the issue, and set a timetable for release.
"We decided that the only way to do this would be a simultaneous release - Microsoft patches, Sun patches, BIND patches" all at the same time, he said.
Another problem that vexed the response team was that in many cases, researchers can use a patch to figure out the underlying vulnerability. But because the security flaw was a design issue, the group had options that could fix the problem in a way that did not spotlight the issue, Kaminsky said.
"This is the fundamental balancing act between how do we notify the good guys without bringing on the bad guys," he said. "We tried to give the good guys as much of a nonlinear advantage as possible. We think we gave them a month."
The solution implemented in the patches is to inject additional randomization into the domain name system (DNS) by randomizing the source ports used in DNS queries. The only permanent solution is to add authentication using a security-enhanced version of the protocol, such as DNSSec, but that proposal is bogged down by worries over adding costs to the name-server system.
Kaminsky's efforts to keep the issue secret until a patch appeared garnered praise from Jerry Dixon, former director of the National Cyber Security Division at the Department of Homeland Security.
"This really shows the value add of independent researchers and the research community helping to make the internet more secure," said Dixon, who is now working with Team Cymru.
Kaminsky asked for the other researchers to show good judgement and not to release additional details of the flaws, if they find them.
"I'm making a request of the open-research community," he said. "Let's see if we can get the good guys fixed (first)."
For those researchers who believe they have pinpointed the problem: Kaminsky says to send him a note, and he will buy you a beer.
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This article originally appeared in Security Focus.
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