DSi system flaws

From DSiBrew
Jump to navigation Jump to search

Undefined instruction/abort exception handler backed by RAM not cleared on reset

Much like the 3DS boot0, some of the DSi's exception handlers are backed by RAM which isn't immediately cleared on a reset. Using fault injection, it is possible to cause an undefined instruction exception before the clearing happens, making the CPU jump to code remaining in RAM from the previous boot cycle. This only works on the ARM7, as on the ARM9, it is backed by main memory, which is only initialized by boot1.

Discovered in June 2016 by Nocash, Normmatt, dark_samus, ApacheThunder (first successful exploit: PoroCYon, March 2021)

Poor System Menu TMD size check

boot1 loads the System Menu's TMD for verification and loading, and it attempts to check the size. However, instead of checking if size > capacity, it checks if size > size, which is always false, resulting in a buffer overflow.

Discovered in August 2017 by Nocash

DS games are not patched to verify overlays

While the System Menu checks all cartridge overlays to prevent unauthorized software, no such check exists when the overlays are actually loaded, despite an MIOS-like patcher being possible to implement. By changing the overlay after it is checked, it is possible to run arbitrary code.

Discovered in January 2010 by Datel, and blasty by reverse engineering Datel's Action Replay