WHERE THERE’S A JTAG, THERE’S A WAY: OBTAINING FULL SYSTEM ACCESS VIA USB
Maxim Goryachy and Mark Ermolov
Everyone makes mistakes. These words are certainly true for developers involved in low-level coding, where such common tools as print debugging and software debuggers run into limits. To solve this problem, hardware developers use in-circuit emulators or, if available on the target platform, the JTAG debugging interface (IEEE1149.1 [1]). Such debugging mechanisms first appeared in the 1980s [2]. Over time, microchip vendors extended the functionality of these interfaces. This allowed developers to obtain detailed information on power consumption, find bottlenecks in high-performance algorithms, and perform many other useful tasks. Hardware debugging tools are also of interest to security researchers. These tools grant low-level system access and bypass important security protections, making it easier for researchers to study a platform’s behavior and undocumented features. Unsurprisingly, these abilities have attracted the attention of intelligence services as well.[…]
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