Jailbreaking my car's navigation system just so I can change the time

A 2014 Renault Latitude’s clock could not be adjusted because its TomTom Carminat LIVE navigation unit hid the relevant settings menu unless it had a legitimate map SD card. The owner had discarded the outdated card, and replacing it would cost about €60, despite needing no maps. Reverse engineering showed that the menu definition itself came from the card, which was protected by checks tying its files to the card’s unique hardware ID. The unit runs a Linux-based operating system on a Samsung processor, and its update image exposed much of the system’s filesystem.

The investigation turns into a search for a way to gain control of the device rather than buy a card. Attempts to modify and install a firmware image ran into an unknown verification step, so the author built a QEMU emulator to study boot behavior and test ideas. The system’s restrictive mounts thwarted several promising leads: a boot-time automation script could launch commands but not pass arguments, while a logging command had a path-traversal flaw but could only write printable text and could not alter executable system files. Fuzzing image decoders found out-of-bounds reads but no useful memory corruption. The account details these dead ends and the unit’s defenses before introducing a kernel-exploit-inspired approach to the remaining problem.