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Lazarus: Healing Compromised Devices in the Internet of Small Things

This project is not maintained. It has been published as part of the following AsiaCCS '20 conference paper:

Huber, M., Hristozov, S., Ott, S., Sarafov, V., & Peinado, M. (2020, October). The Lazarus Effect: Healing Compromised Devices in the Internet of Small Things. In Proceedings of the 15th ACM Asia Conference on Computer and Communications Security (pp. 6-19). https://doi.org/10.1145/3320269.3384723, https://arxiv.org/pdf/2005.09714.pdf

Note that this repository presents a prototype implementation and is not to be used in production.

Introduction

This repository contains the code for Lazarus, a system that enables the remote recovery of compromised IoT devices. With Lazarus, an IoT administrator can remotely control the code running on IoT devices unconditionally and within a guaranteed time bound. This makes recovery possible even in case of severe corruption of the devices’ software stack. We impose only minimal hardware requirements, making Lazarus applicable even for low-end constrained off-the-shelf IoT devices. We isolate Lazarus’s minimal recovery trusted computing base from untrusted software both in time and by using a Trusted Execution Environment (TEE). The temporal isolation prevents secrets from being leaked through side-channels to untrusted software. Inside the TEE, we place minimal functionality that constrains untrusted software at runtime.

This PoC implements Lazarus on the ARM Cortex-M33-based microcontroller LPC55S69 from NXP. Accompanying is a simple IoT hub for device provisioning, secure updates and to show the recovery functionality. The prototype can recover compromised embedded OSs and applications and prevents attackers from bricking devices, for example, through flash wear out.

The remainder of this readme shows how to install, test and further develop the Lazarus project.

Prerequisites

The project was built and tested on Ubuntu 20.04. Other distributions might require adjustments

  1. Install the GNU Arm Embedded Toolchain
sudo apt install gcc-arm-none-eabi

Or install the newest version from here,

  1. Install pip
sudo apt install python3-pip
  1. Install the necessary python libraries:
pip3 install ecdsa
pip3 install pyOpenSSL
pip3 install cbor2
  1. Install a serial terminal of your choice
sudo apt-get install cutecom lrzsz
  1. Flashing the software on the board, requires the crt_emu_cm_redlink flashing utility. This requires installing the MCUXpresso IDE

Build

The projects lz_dicepp, lz_core, lz_cpatcher, lz_udownloader, and lz_demo_app can be built via:

make -r -j$(nproc)

All projects are also built and flashed directly onto the device via the provisioning-script (see Provisioning).

Hardware Setup

The PoC requies an LPC55S69-EVK board, an ESP8266 WiFi-Shield and a Bosch BME280 temperature and humidity sensor.

The demonstrator works with an ESP8266 board and AT-Commands for the TCP connection to the backend. Of course, the network driver can be replaced with any other hardware. For the demonstrator, connect an ESP8266 board to the LPC55S69 evaluation board. It should be a board with a firmware that supports at least 115200k baud rate supports hardware RTS and CTS flow control.

Connect the WiFi-Shield to the Board:

  • 3V3 / 5V and GND can be found on Connector P16 on the LPC55S69
  • ESP8266 RX must be connected to LPC55S69 D1 on P18
  • ESP8266 TX must be connected to LPC55S69 D0 on P18
  • ESP8266 GPIO 13: MTCK / HSPI_MOSI / UART0_CTS must be connected to LPC55S69 D7 on P18
  • EXP8266 GPIO 15: HSPI_CS /*UART0_RTS must be connected to LPC55S69 D10 on P18

Make sure, that the ESP is configured for Lazarus or change the configuration in the source code accordingly. The default setup is:

AT+UART_DEF=115200,8,1,0,3

Connect a micro-USB cable to the Debug Link Port P6. Make sure there is no jumper set at DFU or J10. For more information you can visit the LPC55S69-EVK tutorial: https://www.nxp.com/document/guide/get-started-with-the-lpc55s69-evk:GS-LPC55S69-EVK

Network Setup

The Lazarus-Device communicates with a demo server via TCP/IP. The network credentials have to be provided during provisioning. Create a file wifi_credentials in the folder lz_hub. The file must have the following contents adjusted to your network parameters:

ssid="your-wifi-network-id"
ip="192.168.1.0"
pwd="mypassword123$"
port="65433"

ip and port must be configured to the server where the Lazarus backend runs.

Provisioning

After the board is connected, launch your serial-terminal and select the correct port (e.g. /dev/ttyACM1). Then launch the provisioning script lz_provision_device.sh:

./lz_provision_device.sh

Server Start

Run the Lazarus hub:

python3 ./lz_hub.py ./certificates ./wifi_credentials

Certificate Creation

The repository contains demo certificates in lz_hub/certificates. New certificates can be reated via the following commands.

mkdir -p lz_hub/certificates
cd lz_hub/certificates
openssl req -x509 -nodes -days 3650 -newkey ec:<(openssl ecparam -name prime256v1) -keyout code_auth_sk.pem -out code_auth_cert.pem
openssl req -x509 -nodes -days 3650 -newkey ec:<(openssl ecparam -name prime256v1) -keyout hub_sk.pem -out hub_cert.pem