A suitable audience for reviewing this topic would be Embedded Systems Security Researchers, Hardware Reverse Engineers, and IoT Platform Developers.
Abstract:
This analysis details the hardware reverse engineering and exploitation of a commercial IoT-enabled pressure cooker (Krups), which utilizes Wi-Fi connectivity and a full touchscreen display. Physical teardown revealed a complex, multi-microcontroller architecture designed for high-end consumer appliance functionality. Key components identified include a Renesas R7S721031VZ system-on-chip (SoC) serving as the main processor and display driver, complemented by an ESP32 module for AWS cloud-based (MQTT) Wi-Fi connectivity, and an STM microcontroller for basic appliance functions (heating element control, temperature monitoring) with exposed SWD debug pins. Despite flash encryption on the ESP32, the older chip revision allows for potential glitching for key extraction. The firmware of the main Renesas SoC was successfully dumped and reverse-engineered via SWD. This allowed for the development and installation of a custom firmware wrapper, culminating in the successful porting and execution of the classic game Doom on the appliance’s touchscreen interface at a functional frame rate, demonstrating significant exploitability of the proprietary platform.
Embedded Systems Reverse Engineering Report: Krups IoT Cooking Pot
0:04 Device Context: The appliance is a smart pressure cooking pot featuring Wi-Fi connectivity and a full touchscreen display, lacking internal mechanical components (e.g., slicing, chopping). The retail price point is noted at approximately €400.
1:17 Initial Analysis: The Wi-Fi module’s MAC address Organizationally Unique Identifier (OUI) suggests the presence of an Espressif chip, confirmed later as an ESP32.
2:17 Main Appliance PCB: Internal inspection reveals essential cooking hardware, including a heating element, a temperature sensor, and a fire hazard safety switch for relay fallback. A primary control board featuring an STM microcontroller and exposed SWD pins is identified, likely handling low-level I/O and safety functions.
3:59 Wi-Fi Module Identification: The Wi-Fi component is confirmed as an ESP32 (not an S3 variant). The flash memory is reported as encrypted, but the use of a first-revision chip suggests feasibility for exploit via voltage or clock glitching to facilitate readout. Logging indicates connectivity utilizes the AWS cloud via MQTT protocols requiring a private key.
4:45 Main Processor/Display Driver: The core computational unit is identified as a high-performance Renesas R7S721031VZ SoC (ARM core). It is paired with 128 MB of flash memory and an estimated 128 MB of RAM.
5:16 Secondary Control Chip: A Microchip PIC microcontroller is located beneath the Wi-Fi module, dedicated to managing the capacitive touchscreen interface and handling wake-up events for the main Renesas processor.
6:27 Firmware Extraction: The flash of the Renesas SoC was successfully dumped using an SWD flasher, achieved through reverse engineering the pinout. The extracted bootloader featured detailed logging that aided in subsequent analysis.
6:50 Display Initialization RE: Reverse engineering efforts successfully mapped the LCD initialization routine, crucial for driving the 45-pin LCD cable interface.
7:39 Custom Firmware and Demonstration: A wrapper was written for the Doom engine and ported to run on the Renesas SoC architecture. The custom firmware successfully executes Doom at a satisfactory frame rate, utilizing the physical touchscreen for input controls (mapped to "select" and "start" regions).
9:13 Conclusion: The Renesas SoC is praised for its power and capability, confirming the success of porting the legacy software despite the required deep-level reverse engineering for SDK and development environment setup.