Anti debugging tips for Cortex-M devices

This repository contains the source code and slides from my GreHack presentation

The project is a simple STM32CubeMX project built for a STM32F103 (like the blue pill)

Building

Simply clone the repo, cd source and run make. This will build all the examples.

Examples

DHCSR detection

Detects a debugger by looking at the C_DEBUGEN bit in DHCSR

Source is in source/Core/Src/main.dhcsr.c and compiles into source/build/main.dhcsr.elf

FPB enable

Detects if the FPB is enabled, meaning that a hardware breakpoint might be set.

Source is in source/Core/Src/main.fpb.c and compiles into source/build/main.fpb.elf

FPB remap

This shows how to use the FPB remap capabilities by switching called function at runtime.

Source is in source/Core/Src/main.remap.c and compiles into source/build/main.remap.elf

Hardfault handler

This example shows how to use a custom hardfault handler to detect a bkpt instruction with no debugger attached.

Source is in source/Core/Src/main.hardfault.c and compiles into source/build/main.hardfault.elf