Researchers have extracted the secret key that encrypts updates to an assortment of Intel CPUs, a feat that could have wide-ranging consequences for the way the chips are used and, possibly, the way they’re secured.
The key makes it possible to decrypt the microcode updates Intel provides to fix security vulnerabilities and other types of bugs. Having a decrypted copy of an update may allow hackers to reverse engineer it and learn precisely how to exploit the hole it’s patching. The key may also allow parties other than Intel—say a malicious hacker or a hobbyist—to update chips with their own microcode, although that customized version wouldn’t survive a reboot.
“At the moment, it is quite difficult to assess the security impact,” independent researcher Maxim Goryachy said in a direct message. “But in any case, this is the first time in the history of Intel processors when you can execute your microcode inside and analyze the updates.” Goryachy and two other researchers—Dmitry Sklyarov and Mark Ermolov, both with security firm Positive Technologies—worked jointly on the project.
The key can be extracted for any chip—be it a Celeron, Pentium, or Atom—that’s based on Intel’s Goldmont architecture.
attackers can’t use Chip Red Pill and the decryption key it exposes to remotely hack vulnerable CPUs, at least not without chaining it to other vulnerabilities that are currently unknown. Similarly, attackers can’t use these techniques to infect the supply chain of Goldmont-based devices.
In theory, it might also be possible to use Chip Red Pill in an evil maid attack, in which someone with fleeting access to a device hacks it. But in either of these cases, the hack would be tethered, meaning it would last only as long as the device was turned on. Once restarted, the chip would return to its normal state. In some cases, the ability to execute arbitrary microcode inside the CPU may also be useful for attacks on cryptography keys, such as those used in trusted platform modules.
“For now, there’s only one but very important consequence: independent analysis of a microcode patch that was impossible until now,” Positive Technologies researcher Mark Ermolov said. “Now, researchers can see how Intel fixes one or another bug/vulnerability. And this is great. The encryption of microcode patches is a kind of security through obscurity.”