Intel introduced at Black Hat USA, the Tuning Clone Chip to help protect against certain types of physical failure attacks without requiring any interaction with the computer owner.
The security community is so focused on software-based attacks that they often forget that physical attack maybe. A physical attack is also generally thought of as an attacker who has the ability to physically gain access to the targeted computer and then use some hardware to infiltrate the computer. Such hardware could be a Bash Bunny or one Ducky Rubber, For example. However, it is still software that damages the computer.
There is another, less well known but still possible possibility: messing with the computer chip pins that provide the clock and voltage. This is where the Adjustable Clone Circuit (TRC) comes in, introduced by Intel in its hardware divisions at BlackHat USA 2022.
What is TRC?
TRC uses hardware-based sensors to explicitly detect circuit-based timing errors that occur as a result of an attack, the attack is a non-invasive physical glitch on the clock supply pins, and voltage. Intel’s TRC is also capable of detecting inject electromagnetic error (EMFI).
Faulty attacks allow an attacker to cause a latched NOP (Inactive) instruction instead of a JMP (Jump) condition, altering the flow of execution. It can also help to replace real keys in cryptographic tools with fixed functionality.
Intel shown that TRC is distributed in the 12th generation Intel Core processor family, adding injection detection technology to Intel Converged Security and Management Tools (Intel CSME) (Figure A).
Picture A
It is enabled by default in CSME and does not require any interaction with the computer owner.
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Intel CSME is an embedded subsystem in the Platform Control Center (PCH) designed to serve as the platform silicon initiator, providing operating system-independent remote management, and providing security Add-ons such as Intel Boot Guard or integrated TPM (Trusted-Platform Module) enable secure boot, disk encryption, secure storage, virtual smartcards.
In the release paper from Intel Principal Engineer Daniel Nemiroff and Principal Engineer Carlos Tokunaga, they warn that “with the proliferation of software vulnerabilities through the use of virtualization, stack encryption, pre-authentication tokens, exam, etc., the attackers have turned their attention to physical attacks on the platform computer. A favorite tool of these attackers is the attack that inserts errors through transient voltages, clock pins, to cause circuits to time out, leading to the execution of malicious instructions, stealing secrets. , etc.”
How does TRC work?
The way TRC works is that it monitors the delay of specific types of digital circuits. It is calibrated to signal an error at voltage levels beyond the CSME’s rated operating range. Any error conditions originating from the TRC indicate the possibility of data corruption and trigger mitigation techniques to ensure data integrity. To avoid false positives, Intel has also developed a feedback-based calibration procedure.
Tested and proven security scenarios that TRC can be calibrated to a point where timing breaches can only be the result of an attack. Those tests were performed by Intel Labs, the iSTARE (Intel Security Threat Analysis and Reverse Engineering) team, a group dedicated to hacking Intel chips. The company also mentioned the external inspection. To gain more confidence in TRC and gain more insight into error testing, Intel contracted with Risk to test clock, voltage and EMFI. The company was unable to successfully execute an injection attack, concluding that “in all cases, successful glitches were detected by the countermeasures implemented”.
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Inject wrong in the real world
One might wonder how likely it is that an attacker is actually trying to do real-world error injection. The answer to that question is difficult because there is no real documentation on the subject yet Researchers have shown that such attacks are possible and often use injection devices below the thousand dollar mark.
From an attacker’s point of view, the biggest concern of actually doing error injection is skip secure boot. Embedded systems are also more vulnerable to this type of attack than regular desktop or laptop computers.
Disclosure: I work for Trend Micro, but the views expressed in this article are mine.
