Secure Task Isolation in RTOS for Embedded Systems

Overview

This project implements a multi-layered secure embedded architecture on the ESP32 platform using FreeRTOS. The system is designed as a hardened IoT gateway capable of resisting both internal software attacks and external wireless attacks while maintaining deterministic real-time operation.

Unlike conventional IoT security architectures that rely heavily on TLS, BLE pairing, or cloud-side trust enforcement, this implementation demonstrates a lightweight but extremely structured defense-in-depth design directly inside the embedded firmware stack.

Architecture

The system integrates:

• Secure Boot V2 and eFuse-backed hardware trust
• Software-enforced MPU-style task isolation
• Secure IPC with fault containment
• Authenticated ESP-NOW wireless communication
• PSA Crypto based HMAC verification
• Replay prevention and freshness validation
• Attack simulation and live mitigation
• Deterministic fault handling under FreeRTOS

The architecture is divided into four independent but interconnected security layers:

• Layer 1: Hardware Root of Trust + Secure Boot
• Layer 2: Task Isolation + Software MPU
• Layer 3: Secure IPC + Internal Attack Containment
• Layer 4: Wireless Authentication + Replay Protection

System Objectives

• Firmware Integrity: Ensure only authenticated firmware images execute.
• Runtime Task Isolation: Prevent rogue tasks from reading or modifying privileged memory regions.
• Secure Inter-Task Communication: Prevent internal attacks such as queue flooding, buffer corruption, race conditions, shared resource abuse, and IPC-based denial of service.
• Secure Wireless Communication: Secure ESP-NOW communication providing authentication, integrity, replay prevention, and freshness guarantees without TLS, BLE pairing, or Wi-Fi overhead.
• Fault Isolation: Ensure attacks do not collapse the RTOS kernel (Detect → Isolate → Contain → Continue Operation).

Project Structure

• main/main.c: Primary firmware entry point, initializes NVS, starts IPC layer, creates all FreeRTOS tasks.
• main/comms_layer.c & .h: Implements the secure IPC backbone (static queues, static mutex).
• main/task_sensor.c: Simulates an embedded sensor node generating telemetry.
• main/task_comms.c: Security-critical task performing IPC validation, threat detection, HMAC generation, and ESP-NOW transmission.
• main/task_attacker.c: Simulates malicious firmware behavior (buffer corruption, queue flooding, unauthorized memory access).
• main/mpu_fault.c: Implements a software-based MPU.
• main/ipc_fault.c: Centralized IPC threat response engine.
• main/task_logger.c: Dedicated audit logging subsystem.
• main/task_admin.c: Highest privilege supervisory task generating heartbeat logs.

Getting Started

To compile and flash this project onto an ESP32:

1. Ensure you have the ESP-IDF installed.
2. Clone this repository.
3. Run idf.py build to compile the firmware.
4. Run idf.py -p (PORT) flash monitor to flash the ESP32 and view the logs.

Documentation

For a detailed analysis of the architecture, simulated attack vectors, and security principles, please refer to Report.md.