CHERIoT RTOS: An OS for Fine-Grained Memory-Safe Compartments on Low-Cost Embedded Devices

Embedded systems do not benefit from strong memory protection, because they are designed to minimize cost. At the same time, there is increasing pressure to connect embedded devices to the internet, where their vulnerable nature makes them routinely subject to compromise. This fundamental tension leads to the current status-quo where exploitable devices put individuals and critical infrastructure at risk.

We present the design of a dependable embedded OS where compartmentalization and memory safety are first-class citizens. We co-design the OS with an embedded hardware platform that implements CHERI capabilities at a similar cost profile to existing chips with minimal security. We demonstrate key design benefits: fine-grained fault-tolerant compartments, OS-level support for compartment-interface hardening, and auditing facilities to thwart supply-chain attacks, among others, and show that they come at a memory usage and performance cost that allows their widespread deployment in cheap, resource-constrained devices.