Microsoft still certifying leaky drivers

Months after promising to tighten up its procedures for certifying third-party software drivers, Microsoft Corp. is still giving the green light to network interface card (NIC) drivers that leak sensitive user information from machines running Windows Server 2003, according to a prominent security company.

The allegations were made in an alert posted Monday by Next Generation Security Software Ltd. (NGSSoftware) of Sutton, England.

Microsoft was unable to respond in time for this report.

At least two NIC drivers that shipped with Windows Server 2003 contain a security hole that leaks information stored on a system in Ethernet "frames" or streams of data sent over a network, according to the alert.

The alert identified the vulnerability in drivers for the VIA Technologies Inc. Rhine II ethernet controller and the Advanced Micro Devices Inc. (AMD) PCNet family of drivers, according to Chris Paget, the NGSSoftware researcher who wrote the alert.

The Rhine II and PCNet drivers were the only two tested by NGSSoftware. Many other Windows Server 2003 NIC drivers could also be affected, Paget said.

The problem reported by NGSSoftware is just a new variation on a vulnerability discovered by @stake Inc., a security consulting company based in Cambridge, Massachusetts, almost a year ago and revealed in January. [See "Vendors mum on Ethernet driver warnings," January 10.]

Institute of Electrical and Electronics Engineers Inc. (IEEE) standards specify that streams of information sent over an Ethernet network should be organized into "frames" that are at least 46 bytes long.

In cases where higher layer protocols such as IP (Internet Protocol) provide packet data that is less than 46 bytes long, the software device drivers are supposed to fill in the empty space in the Ethernet frame with unusable data such as strings of "0's" in a process known as "padding" the frame.

Researchers at @stake found that the software drivers written by many leading NIC manufacturers instead use real data pulled at random from a machine to pad the frames.

At the time, @stake researchers demonstrated the problem with messages assembled using ICMP (Internet Control Message Protocol), an extension of IP. Researchers captured passwords and Web browser session information from the filler information.

NGSSoftware found leaked data in padding for TCP (Transmission Control Protocol) exchanges. Other protocols may exhibit the same flaw as well, Paget said.

While the vulnerability does not affect information sent over the Internet, it could allow attackers on the same network as a machine that is vulnerable to sniff out passwords, account numbers or other information from that system, he said.

The problem is a "low risk" for most organizations, but could be a big problem for companies or organizations with secure servers running the Windows platform.

"If you're a government with top secret information or you have a security-sensitive server, it could allow someone on the same network as the server to get information out of it," Paget said.

Microsoft does not produce NIC drivers for its operating systems, relying on the NIC hardware manufacturer and other third party companies to do that using specifications provided by the Redmond, Washington, company.

However, Microsoft certifies all NIC drivers for use with Windows prior to their inclusion on Windows CDs.

Following revelations about the ethernet driver leak problem, Microsoft said in a statement on the CERT Coordination Center Web site that it would be including tests for the information leak problem in its driver certification program.

The presence of vulnerable drivers on the recent Windows Server 2003 release suggests that may have been an empty promise, according to Paget.

The sheer breadth of the problem may have played a role in Microsoft's failure to crack down on faulty drivers, Paget said.

Microsoft must rely on third party vendors to fix the problem in their software and submit that software for certification. Unable to force those companies to update their software, Microsoft may have had to choose between looking the other way when certifying the drivers and the even less palatable option of shipping a Windows 2003 CD without support for many common network drivers, according to Paget.

That dilemma may not be resolved anytime soon.

Almost a year after the discovery of the vulnerability, CERT's list of affected hardware and software vendors shows that the vast majority have not indicated whether their products are vulnerable to the problem or not. (See http://www.kb.cert.org/vuls/id/412115.)

Paget recommends that organizations concerned about the problem consult the CERT list to see if the drivers they use are vulnerable to the information leak problem.

Companies that have not responded to CERT should be encouraged to do so and, if necessary, issue patched drivers to their customers, Paget said.

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Paul Roberts

IDG News Service
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