Feeds

MS patch system poses 'significant risk', say researchers

The fix could automate production of the attack

Choosing a cloud hosting partner with confidence

The automatic patch-based exploit generation (APEG) requires that the differences in patched and unpatched binaries be found first. The researchers used eEye's Binary Diffing Suite (EBDS), but others - such as the well-known bindiff - could be used as well. The researchers then tested a number of heuristics for determining which of the changes actually fixed the flaw and discovered that, frequently, the smallest changes typically acted as a reliable marker for the location of a new sanity check.

Using principles from automated test-case generation processes, the four researchers modeled the flow of the program and used an intermediate language, known as Vine, to express the sequence of instructions that lead to the vulnerable code being executed. Knowing the execution path allows the researchers to place constraints on the inputs that could trigger the exploitation of the vulnerability, significantly reducing the number of possible variables through which the APEG has to search. The researchers used a combination of static analysis, where a single execution of the program is used to determine program flow, and dynamic analysis, where an abstract graph represents all the control-flow possibilities.

The result is a constraint formula, the solution to which are candidate exploits. The possible exploits can then be tested to determine which ones are true exploits for the vulnerability.

Brumley and his colleagues used the automatic patch-based exploit generation (APEG) system to create exploits from five recent Microsoft patches. After the differences between patched and unpatched binaries were found, the system took as little as six seconds to, at most, about three minutes to find an exploit.

"Specific types of attacks, such as control hijack, are just an extra condition on the set of all possible exploits for a single bug," Brumley said. "We can include such conditions in our approach."

Even though the system does not create fully weaponize exploits and may not work for all types of vulnerabilities, it does show that developing exploits from patches could be done in minutes. Yet, Microsoft has not taken adequate steps to make such attempts more difficult, Brumley said. The researchers suggested possible avenues that Microsoft could pursue to increase the likelihood that customers received patches before attackers could reverse engineer them, including obfuscating the code, encrypting the patches and waiting to distribute the key simultaneously, and using peer-to-peer distribution to push out patches faster.

"There are ways that Microsoft could distribute patches and not tip off the attackers," Brumley said.

Microsoft declined to comment for this article, except to say that the company is reviewing the research.

Some security experts doubt whether the APEG process could result in weaponized exploits quickly enough to pose a threat.

"Every patch from Microsoft has differences," Errata Security's Graham said. "There is nothing that can really generalize across Microsoft patches. There are a lot of possibilities for diagnostic tools that will shorten the time (to create an exploit), but that time will never go to zero."

Yet, even with his doubts, Graham stressed that the trend is clear and agreed that Microsoft should be thinking about making patches more difficult to exploit.

"You (developers) should generally be thinking about this," he said. "As reverse engineering gets more prevalent in the industry, you should be generally thinking about how to change your code to make it harder to do."

Brumley and his colleagues will present the paper at the annual IEEE Symposium on Security and Privacy in May. The co-authors of the paper are Pongsin Poosankam of Carnegie Mellon University, Dawn Song of University of California at Berkeley, and Jiang Zheng of University of Pittsburgh.

This article originally appeared in Security Focus.

Copyright © 2008, SecurityFocus

Beginner's guide to SSL certificates

More from The Register

next story
Russian hackers exploit 'Sandworm' bug 'to spy on NATO, EU PCs'
Fix imminent from Microsoft for Vista, Server 2008, other stuff
Microsoft pulls another dodgy patch
Redmond makes a hash of hashing add-on
FYI: OS X Yosemite's Spotlight tells Apple EVERYTHING you're looking for
It's on by default – didn't you read the small print?
'LulzSec leader Aush0k' found to be naughty boy not worthy of jail
15 months home detention leaves egg on feds' faces as they grab for more power
Forget passwords, let's use SELFIES, says Obama's cyber tsar
Michael Daniel wants to kill passwords dead
FBI boss: We don't want a backdoor, we want the front door to phones
Claims it's what the Founding Fathers would have wanted – catching killers and pedos
Kill off SSL 3.0 NOW: HTTPS savaged by vicious POODLE
Pull it out ASAP, it is SWISS CHEESE
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Cloud and hybrid-cloud data protection for VMware
Learn how quick and easy it is to configure backups and perform restores for VMware environments.
Three 1TB solid state scorchers up for grabs
Big SSDs can be expensive but think big and think free because you could be the lucky winner of one of three 1TB Samsung SSD 840 EVO drives that we’re giving away worth over £300 apiece.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.