September 2024
Intermediate to advanced
408 pages
7h 29m
English
The GD32F103 clone of the STM32F103 inherits its ancestor’s security model, in which RDP Level 1 allows for a JTAG connection but disconnects flash memory. Obermaier, Schink, and Moczek (2020) describes a clever exploit for this.
The authors noticed that flash memory restrictions apply when the C_DEBUGEN bit of the DHSR register is set, which occurs when the CPU debug module is enabled to halt the CPU or access the processor’s registers. The restrictions do not apply when system components such as the peripherals are accessed through JTAG. The challenge is to trigger code execution without touching the CPU registers, only the peripherals.
One of their exploits works like this: first a JTAG debugger takes ...
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