A British security researcher today said it took him six weeks to craft a three-exploit package that brought Microsoft's Internet Explorer 8 (IE8) to its knees at Pwn2Own Wednesday.
Independent researcher Stephen Fewer walked off with $15,000 and a Sony notebook yesterday after hacking IE8 on Windows 7 by exploiting three unpatched vulnerabilities in the operating system and browser.
"It was a challenge, especially engineering the exploit that escaped Protected Mode," said Fewer today, referring to the "sandbox" that isolates IE8 from the rest of the computer.
The sandbox, like the one baked into Google's Chrome, is designed to hold malicious code within the browser so that it can't leak into the operating system or system as a whole.
"I spent about six weeks finding the vulnerabilities and engineering the exploits," Fewer said. "Then I decided to give [Pwn2Own] a go and bought a plane ticket."
Fewer is a first-time Pwn2Own contestant and winner. He has a one-man consulting firm called Harmony Security and is a long-time contributor to both the Metasploit open-source penetration testing toolkit project as well as HP TippingPoint's Zero Day Initiative (ZDI) bug bounty program, which pays researchers for finding and reporting vulnerabilities. TippingPoint is the sponsor of Pwn2Own.
Fewer chained three exploits together to bring down IE8, a feat that Aaron Portnoy, manager of TippingPoint's security research team and Pwn2Own's organiser, called "impressive" yesterday.
Two of the three were necessary to craft a reliable attack that sidestepped for Address Space Layout Randomisation (ASLR) and Data Execution Prevention (DEP) on Windows 7. ASLR and DEP are technologies baked into Microsoft's operating system designed to make it more difficult for exploits to reliably execute.
The third exploit leveraged yet another bug to jump out of the Protected Mode sandbox.
"That was pretty difficult," said Fewer, talking about the sandbox-escape exploit. "It took quite a while to engineer that and then there was the time pressure of the contest."
By escaping Protected Mode, Fewer was able to gain complete control over the Sony laptop running Windows 7, a point he proved by adding a file to the machine, mimicking a cybercriminal's insertion of additional malware.
Fewer's hack of IE was the first ever at Pwn2Own to bust out of a browser sandbox. Although Chrome also boasts an anti-exploit sandbox, that browser has never been breached at Pwn2Own.
Yesterday, one expected Chrome contestant was a no-show, while a team slated to go second decided to focus instead on an attack against RIM's BlackBerry OS later today.
Although Fewer acknowledged he hasn't poked around Chrome, he didn't seem surprised that no one took on Google's browser yesterday. "Chrome's sandbox is fundamentally quite solid," he said.
Fewer made use of the work by Peter Vreugdenhil, last year's IE Pwn2Own winner, to build his multi-part package. "Peter's work was great and I applied a few of his techniques," said Fewer.
Vreugdenhil, who now works for TippingPoint, chained two exploits last year to bypass Windows 7's ASLR and DEP.
The only other browser to fall Wednesday was Apple 's Safari 5, which dropped to a team from French security company Vupen minutes before Fewer took his shot at IE8.
Not surprisingly, Fewer felt great about winning the $15,000. "I feel fantastic," he said today. "Everything here went very smoothly."
He plans to spend the cash prize to pay for his trip from the UK and on some home improvements.
Today's Pwn2Own schedule will pit researchers against Mozilla's Firefox - that browser's turn was postponed to today after Wednesday's round started late - and four smartphones running Apple's iOS, Google's Android, Microsoft's Windows Phone 7 and RIM's BlackBerry OS.