Thunderbolt: A new way to hack Macs
Blind trust turned on by default
The 10Gbit/s interconnect Apple introduced Thursday in a new line of Macbook Pros may or may not change the way the world connects external hard drives and other peripherals to their computers. But it's safe to say the newfangled copper link likely contains the same security weakness that for years has accompanied another Mac innovation: the Firewire port.
Like Firewire, the Intel-designed Thunderbolt is based on a peer-to-peer design that assigns blind trust to any device that connects through the bi-directional, dual channel interface. According to security expert Robert Graham, that gives attackers yet another chink to exploit when targeting machines that offer the interconnect.
“Imagine that you are at a conference,” Graham, the CEO of security consultancy Errata Security, writes. “You innocently attach your DisplayPort to a projector to show your presentation on the big screen. Unknown to you, while giving your presentation, the projector is downloading the entire contents of your hard disk.”
Such attacks rarely work on USB ports because they are based on a “master-slave” design. That means the computer has full access to the attached device but the attached device has limited access to the computer. Firewire and now Thunderbolt, by contrast, have full access to a Mac's entire memory.
Lest this sound like so much theoretical mumbo jumbo, Graham offers this real-world anecdote from a recent penetration testing outing:
A company gave employees laptops that were secured using all the latest technology, such as encrypted boot disks and disabled USB ports. Users weren't given admin privileges. But the Firewire ports were open. We connected a device to the Firewire port on a laptop, and broke in with administrator access. Once in, we grabbed the encrypted administrator password (the one the owner of the laptop didn't know). We cracked it using L0phtcrack. That password was the same for all notebooks handed out by the company, so we now could log onto anybody's notebook. Worse -- that administrator account was also on their servers, so we could simply log into their domain controllers using that account and take control of the entire enterprise.
Because Thunderbolt has the same unrestricted access to the computer, Graham speculates it is vulnerable to the same types of attacks.
Intel processors offer the means to significantly rein in Thunderbolt by restricting a device's access to memory locations of the computer it's attached to. But as of now, there are no indications Mac OS X makes use of this.
“With the newer Intel processors, I think it would be pretty easy” to restrict Thunderbolt's memory access, Graham tells The Reg. “I don't see any problem why they can't do it.” ®