Practical Analysis of Embedded Microcontrollers against Clock Glitching Attacks

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Presented at Hacker2HackerCon 2014 by

Ricardo Silva

Clock glitching attacks are one of the different types of hardware fault injections studied nowadays. By glitching the clock, it is possible to change the target’s hardware behavior, either by corrupting or simply skipping CPU instructions. Since the software is not prepared to handle a device that has been tampered with, an attacker can exploit such vulnerability and take over the control flow of the program. Multiple attacks can then be performed, such as forcing the device to exiting loops or dump its own memory. This work applies such technique against AVR microcontrollers by implementing a modular glitcher environment. Such environment allows not only for fine-tuning of at- tacks, but also a brute-force algorithm for finding the glitching range to be implemented. By executing multiple repeatable experiments, both on handcrafted and compiled code, it demonstrates that such architecture is vulnerable against these attacks by introducing faults that were not expected and cannot be handled by the software. The implications of this regarding the security of the program are discussed in this work. Additionally, a critical analysis of the disadvantages and issues of the approach used and how it can be further improved is provided. Estudante de Ciência da Computação pela UFRGS realizando dupla-diplomação na TU Berlin. Atualmbolsista no SecT (Security in Telecommunications) no Telekom Innovation Laboratories, onde realiza pesquisas em injeção de falhas em hardware, mais precisamente em Clock Glitching.