eecs 388: embedded systems - ku ittcheechul/courses/eecs388/w11.security.pdf · simplex...

EECS 388: Embedded Systems

11. Safety and Security

Heechul Yun

Agenda

• Safety and security challenges

• Safety and fault tolerance

• Security basics

Safety

• Many CPS are safety-critical systems

– Can harm people or things

Remote Attack on Jeep (2015)

https://www.wired.com/2015/07/hackers-remotely-kill-jeep-highway/

• Able to remotely (via cellular network) control steering, brake, and other critical functions via the car’s infotainment system

5C. Miller and C. Valasek, “A Survey of Remote Automotive Attack Surfaces”

Remote Attack Surfaces

“…As cars move into the future, they are being more connected with features normally found in desktop computers like apps and even web browsers. The 2014 Jeep Cherokee even has a Wi-Fi hotspot with open ports (when not using encryption)…”

C. Miller and C. Valasek, “A Survey of Remote Automotive Attack Surfaces”

Ukraine Power Grid Attack (2016)

• Attack on SCADA control network of a power grid in Ukraine, causing blackout on 80K users.

https://www.antiy.net/p/comprehensive-analysis-report-on-ukraine-power-system-attacks/

Pacemaker Hack (2017,2018)

https://www.wired.com/story/pacemaker-hack-malware-black-hat/

https://www.theguardian.com/technology/2017/aug/31/hacking-risk-recall-pacemakers-patient-death-fears-fda-firmware-update

Internet of Things (IoT)

• IoT ~= Internet connected embedded systems

• “Internet is evil and wants to kill you”

Mirai Bot DDoS Attack (2016)

10https://www.nytimes.com/2016/10/22/business/internet-problems-attack.html

The Mirai IoT Botnet

https://www.corero.com/resources/ddos-attack-types/mirai-botnet-ddos-attack

IoT WiFi Attacks (2019)

12https://hackaday.com/2019/09/05/esp8266-and-esp32-wifi-hacked/

“… These EAP hacks are more

troubling, and not just because

session hijacking is more

dangerous than a crash-DOS

scenario. The ESP32 codebase

has already been patched

against them, but the older

ESP8266 SDK has not yet. So

as of now, if you’re running an

ESP8266 on EAP, you’re

vulnerable. We have no idea how

many ESP8266 devices are out

there in EAP networks, but we’d

really like to see Espressif patch

up this hole anyway. “

13https://techcrunch.com/2019/11/07/amazon-ring-doorbells-wifi-hackers/

Challenges

• Predictability

• Complexity

• Reliability

• Security

Real-Time Predictability

Michael G. Bechtel and Heechul Yun. “Denial-of-Service Attacks on Shared Cache in Multicore: Analysis and Prevention.” In RTAS, 2019 (Outstanding Paper Award)

Core1 Core2 Core3 Core4

victim attackers

• Observed worst-case: >300X (times) slowdown

– On simple in-order multicores (Raspberry Pi3, Odroid C2)Difficult to guarantee predictable timing

Complexity

• Software complexity increases

More bugs, unintended side-effects

Ibe et al., “Scaling Effects on Neutron-Induced Soft Error in SRAMs Down to 22nm Process” (Hitachi)

Reliability

• Transient hardware faults (soft errors)

– Due to environment factors (ex: alpha particle, cosmic radiation)

– Manifested as software failures

– Bigger problem in advanced CPU• Increased density higher soft error rate (SER) per chip

http://www.cotsjournalonline.com/articles/view/102279

Hardware can fail

Security

• Insecure software in CPS safety hazards

• Stuxnet: first reported cyber warfare, targeted for Iranian nuclear plants (destroying centrifuges)

• Vermont power grid hack by Russia

• Remote hack into cars (Zeep)

• Police drone hacking

CPS software can be attacked

Security

https://meltdownattack.com/

CPS hardware can be attacked

How to Improve Safety of CPS?

• Correct by design

– Model based design, verification and validation

• Deal with failures

– Run-time monitoring

– Redundancy

Redundancy

• Triple Modular Redundancy (TMR)

Module #1

Module #2

Module #3

Voting

Majority outcome

Automotive Industry Approaches

• Hardware redundancy is needed– A well known solution: 2oo3 (2 out of three with

voting, a.k.a. TMR)

• But the automotive industry is cost sensitive– 2oo3 is too expensive (3 redundant ECUs)

• Alternative approach– 1oo2d: Dual redundancy with diagnostics

22Robert Leibinger, “Software Architectures for Advanced Driver Assistance Systems (ADAS)”, OSPERT 2015

1oo2D Approach

• Runtime diagnostics system detects node failures• Continue to operate while disabling the failed node• What to do after one node failed?

ECU #1

ECU #2

Inputdata

Diagnostics

enable

Outputdata

Robert Leibinger, “Software Architectures for Advanced Driver Assistance Systems (ADAS)”, OSPERT 2015

1oo2D with Reconfiguration

Diagnostics

Normal operation

ECU #1 ECU #2 ECU #3

Diagnostics

1 node failedECU #1 ECU #2 ECU #3

• ECU#3 is not necessarily identical to ECU#1 and #2

• Some (non critical) functions in ECU#3 may be disabled

Diagnostics

Critical functions are migrated to a different nodeECU #1 ECU #2 ECU #3

Func2 Func1

Tesla FSD Chip

• Dual redundant architecture (1oo2D)

27https://www.youtube.com/watch?time_continue=4988&v=Ucp0TTmvqOE

Simplex Architecture

• Protect an untrusted complex controller with a trusted backup controller– General architectural principal (*)

– Called Run-Time Assurance (RTA) in Airforce (**)

28(*) L. Sha, Using Simplicity to Control Complexity, IEEE Software, 2001(**) M. Clark et al., A study on run time assurance for complex cyber physical systems, Airforce Research Lab, 2013

Safety Controller

PerformanceController

UAVPlant

Decision Logic Plant

UAV Simplex Architecture

• Idea: use two hardware/software platforms with distinct performance and reliability characteristics to realize Simplex

High Performance (HP) Platform

High Assurance (HA) Platform

Safety controller

Performance controller

UAVPlant

Decision Logic

GPS,IMU

Radar, Camera

HA Platform(Arduino)

HP Platform:(Tegra TK1)

Rich OS (Linux), Middleware (ROS)

Prasanth Vivekanandan, Gonzalo Garcia, Heechul Yun, Shawn Keshmiri. A Simplex Architecture for Intelligent and Safe Unmanned Aerial Vehicles. IEEE RTCSA, IEEE, 2016. (Best Student Paper Nominee)

Two Platforms

• High Assurance (HA) Platform– Simple hardware and software for verification and reliability– Hardware: low frequency and density to reduce SEUs– Software: certifiable, simple, low SLOC

• High Performance (HP) Platform– Complex hardware and software for performance– Hardware: performance oriented multicore, multi-gigahz, gpu– Software: productivity oriented software framework, millions SLOC

Performance Controller

• HW: Nvidia Tegra TK1, 4 x Cortex-A15 @ 2.3GHz, 192 core GPU• SW: Use Linux (Ubuntu), Robot Operating System (ROS)

ROS node/topic architecture

Safety Controller

• HW: Arduino Due, a single ARM Cortex-M3 @ 80MHz

• SW: Matlab Simulink coder + Arduino sketch, no OS

Safety controller (Simulink model)

Decision Logic

• Assumption– HA (safety controller, decision logic) is trusted– HP is not trusted

• Fault detection and recovery– Detect crash, connect failure, timing violation, invalid outputs

(e.g., NaN)– Recovery: reboot the HP platform– Limitation: Currently don’t know “unsafe” states

Detectable faults

Execution Flow

HA platform(Arduino)

HP platform(Tegra TK1)

Prototype Avionics #1

• HA: Arduino based custom DAQ

– Basic sensors: IMU, GPS

• HP: Nvidia Tegra TK1

– 4 x ARM cores + 192 GPU cores

12-15 knots wind and 18 knots gust

Prototype Avionics #2

Avionics: Pixhawk (HA) + Odroid XU4 (HP)Airplane: Skyhunter

Your Project

Raspberry Pi 4 (Linux)

HiFive1 rev B Microcontroller

Camera

Intelligent controller(Vision based steering using DNN)

Safety controller(Basic control + emergency breaking)

Self-Driving Car

Limitations of Simplex

• Assume HA is trusted.– Both software and hardware of HA must be trusted– HA is a single point of failure

• Doesn’t deal with physical system faults– Faults on sensors, actuators– Damaged fuselage, wings, ..

• Doesn’t deal with security issues– What if an attacker re-programs the HA controller?

Agenda

• Security attributes

• Threat model

• Encryption

• Digital signature and hashing

• SSL/TLS

Security

• What are the attributes of security?

Security Attributes

• Confidentiality

– Can secret data be leaked?

• Integrity

– Can the system be modified?

• Availability

– Can the system function when needed?

• Authenticity

– Am I interacting with the right person/thing?

System Security

• A system is secure if it is used and accessed as intended under all circumstances

– Unachievable

• A system security can be determined only in the context of a clear threat model

Threat Model

• Attacker’s capabilities– What we assume the attacker can do

• Examples– Has a physical access to the system

– Has a remote (network) access to the system

– Can reprogram the software

– Can eavesdrop the communication

– …

Example: Pacemaker Security Analysis

44Halperin et al. “Pacemakers and Implantable Cardiac Defibrillators: Software Radio Attacks and Zero-Power Defenses,” IEEE S&P, 2008 https://www.secure-medicine.org/hubfs/public/publications/icd-study.pdf

Example: Pacemaker Security Analysis

• Threat model: 3 classes of attackers– Attacker possessing an ICD programmer.

– Attacker who simply eavesdrops on communications between an ICD and the programmer, using commodity software-defined radio.

– Attacker who eavesdrops as well as generates arbitrary RF traffic to the ICD, possibly spoofing an ICD programmer.

• Demonstrated successful attacks on all cases

Basic Cryptography

• Symmetric (shared key) crypto

– XOR encryption (one-time pad)

– DES (56 bit key)

– AES (up to 256bit key)

• Asymmetric (public-key) crypto

– RSA

• Digital signature and secure hashing

– SHA-256

NPUT OUTPUT

A B A XOR B

XOR Encryption

Slide source: Edward A. Lee and Prabal Dutta (UCB)

XOR Encryption

Example

• Encryption

• Decryption

01010111 01101001 01101011 01101001 M: message (“Wiki”)XOR 11110011 11110011 11110011 11110011 K: repeat key (11110011)-------------------------------------------= 10100100 10011010 10011000 10011010 C: encrypted message

10100100 10011010 10011000 10011010 C: encrypted messageXOR 11110011 11110011 11110011 11110011 K: repeat key-------------------------------------------= 01010111 01101001 01101011 01101001 M: message (“Wiki”)

https://en.wikipedia.org/wiki/XOR_cipher

XOR Encryption

Example

• Recovering the key from M and C

• Pros and Cons of XOR Encryption

– Inexpensive

– Insecure when key is used repeatedly and/or part of the message is known

01010111 01101001 01101011 01101001 M: message (“Wiki”)XOR 10100100 10011010 10011000 10011010 C: encrypted message -------------------------------------------= 11110011 11110011 11110011 11110011 K: repeat key (11110011)

Symmetric (Shared Key) Cryptography

• Block cipher uses more elaborate algorithms so that key size and message size don’t need to be the same.

• Data Encryption Standard (DES) – mid 1970s.

• Advanced Encryption Standard (AES) – 2001Based on a cryptographic scheme called Rijndaelproposed by Joan Daemen and Vincent Rijmen, two researchers from Belgium. AES uses a message block length of 128 bits and three different key lengths of 128, 192, and 256 bits.

Asymmetric (Public Key) Cryptography• Each participant has two keys, a public and a private one.

• A message is encrypted with the public key.

• The message can only be decrypted with the private key.

• Public and private keys match via clever algorithms.

• Relies on a one-way function, easy to compute, hard to reverse without knowing a (private) key.

Widely Used Asymmetric Cryptography:SSL/TLS

• Secure Socket Layer/Transport Layer Security

– Widely used for web serverson the Internet

– Provides:• Authentication

• Confidentiality and integrity of communication

HTTPS = HTTP over SSL/TLS

Slide source: Hokeun Kim and E. A. Lee (UCB)

Intro to SSL/TLS Based on Certificates

Account balance

Make wire transfer

Internet

Eavesdropper

ID/PasswordBrowser (client)

Your bank (server)Message Encryption

Shared secret: Cryptographic key for encryption

• Public key cryptography (e.g., RSA)

Browser (client)

Secret to be sharedEncrypted With Bank's

Public Key

Bank'sPublic Key

Bank'sPrivate Key

Your bank (server)

Decrypted WithBank's Private Key

• However, even with public key cryptography…Browser (client) Your bank (server)

Bank'sPublic Key

Bank'sPrivate Key

Fake website &Malory's Public Key

Encrypted With Malory's Public Key

Malory"Man In The Middle"

Decrypted WithMalory's Private Key

Encrypted With Bank's Public Key

Malory'sPublic Key

Malory'sPrivate Key

Spoof network address to redirect client to fake website(e.g. DNS cache poisoning)

www.bankofamerica.com=> Malory's IP address

Signing a Message• Each participant has two keys, a public and a

private one.

• A message is encrypted with the private key and both the message and its encryption are sent.

• The encrypted part can be decrypted with the public key. If it matches the plaintext message, the signature is valid.

Intro to SSL/TLS Based on CertificatesA (Digital) Certificate (Proof of Public Key's Authenticity)

Signed (encrypted)* with issuer (CA)'s Private key

Can only be decrypted (verified) with issuer (CA)'s matching public key!

• www.bankofamerica.com

• Additional Information: validity period, etc.

• Bank's public key

Actually the hash of data is encrypted (signed), and the result of decryption is also hash

• Digital Signature

• Name of certificate authority (CA)

Browser (client) Your bank (server)

CAs Issues a certificate for Bank

Connects to www.bankofamerica.com

CA Certificates(embedded in browser)

Bank's certificate issued by CA

Verify Bank's certificatewith CA's certificate

Malory's (invalid)certificateinsisting ownership of domain

Can't be verified!

Issues with Using SSL/TLS for IoT

• Overhead for resource-constrained devices

– Energy/computation overhead for public key crypto, communication bandwidth, memory, etc.

• Limited support one-to-many communication

– Connections are 1-to-1 (server/client model)

Thermostat

Sensors

Garage door

Vehicle

Fridge

Microwave

Washing Machine

Roomba

Mobile phoneRemote doorcontrol

Certificates

Issues with Using SSL/TLS for IoT

• Company Validation… First, we will verify that the company requesting a certificate is in good standing …

• Domain Validation… can include emails or phone calls to the contact listed in a domain's whois record …

• Management overhead of certificates

– If you use commercial certificate authorities (CAs)

– Alternative: free & automated CA• Overhead for managing domains to get certificates

Quotes from www.digicert.com

Is Your Project Secure?

Camera

Self-Driving Car

Can’t be answered until you define the threat model.

Threat Model(What Attacker Can Do)

• Have remote access to the same WiFi network?

• Have remote login capability to the Pi 4?

• Have physical access to the hardware?

Camera

Self-Driving Car

Design Your Defenses

• Have remote access to the same WiFi network?

• Have remote login capability to the Pi 4?

• Have physical access to the hardware?

Camera

Self-Driving Car

Example Defenses

• Have remote access to the same WiFi network?– Encrypt all communications over WiFi (e.g., ssh)

• Have remote login capability to the Pi 4?– Don’t give the sudo permission, patch OS, …

• Have physical access to the hardware?– Secure boot, remote attestation, encrypt serial communication, …

Camera

Self-Driving Car

Agenda

• Software security

• Information flow

Memory Safety Vulnerabilities

• Stack overflow

• Heap overflow

• Use after free

• Double free

• Null pointer

• Uninitialized use

• …

Memory Safety Vulnerabilities

• Account for 70% percent of all Microsoft patches over the past 12 years

Image source: Matt Miller, Microsoft

https://www.youtube.com/watch?v=PjbGojjnBZQ

Stack/Buffer Overflow

• Overflow either the stack or memory buffers

• Failure to check bounds on inputs, arguments

Stack Overflow

Not this

Stack Overflow

Stack Frame Layout

Stack pointer

Stack Overflow

return address

saved frame pointer

sensor_data[15]

sensor_data[1]

sensor_data[0]

What would happen when more than 16 bytes are received?

Buffer Overflow

What would happen when more than 16 bytes are received?

Use after Free

• Freed but uninitialized pointers can be exploited77

#include <stdlib.h>#include <stdio.h>struct auth{

char name[32];int priv;

int main() {struct auth *auth_ptr;char *service;auth_ptr = malloc(sizeof(struct auth));free(auth_ptr);service = malloc(36);printf("[auth = %p, service = %p]\n",

auth_ptr, service);free(service);return 0;

$ ./use_after_free[auth = 0x716010, service = 0x716010]

Linux Kernel: Buffer Overflow

78http://www.cvedetails.com/vulnerability-list/vendor_id-33/product_id-47/cvssscoremin-9/cvssscoremax-/Linux-Linux-Kernel.html

Linux Kernel: Use-after-free

Linus Torvalds: "Nothing better than C"

https://www.youtube.com/watch?v=CYvJPra7Ebk

Recall: C is popular but …

• Why popular?– Fast, efficient, and portable

– Close to machine (assembly-like control)

– Pointer, minimal type checking

• Problems– Pointer, minimal type checking

– Require manual control of dynamic memory

– Unsafe (memory leak, undefined behavior, ..)

– Difficult to write correct, safe, secure code

“C is assembly, Rust is future”

Intel and Rust: the Future of Systems Programming: Josh Triplett

Information Flow

• Many security properties concern the FLOW of information between different principals in a system.– Confidentiality: preventing secret attacker

– Integrity: preventing attacker system

• Information flow security is the study of how such flows affect the security and privacy properties of a system.

Example 1: Illegal Information Flow?

The fact that you failed to loginLeak some information about Your password

Limiting Password Attempts

• To limit information leakage, most today’s devices disable them after a few failed attempts.

Invasive Attack

What if the attacker is capable of directly reading from the memory?

Secure Storage and Hashing

(hash(input_pwd) == patient_pwd_hash)

patient_pwd_hash = read_from_secure_storage(…)

Invasive Attack

What if the attacker is capable of directly reading from the memory?

Summary

• Security used to be an after thought (if any)

• In networked embedded systems (a.k.a. IoT) security is a first-class concern

• Embedded systems security are even harder than desktop/server security because of:– Diversity (no standard os, hardware, runtime, …)

– Resource constraints (performance, energy, memory space, …)

– The prevalent use of C (insecure language)

• Read chapter 17, take security courses…

Acknowledgements

• Security slides draw heavily on materials developed by

– Edward A. Lee and Prabal Dutta (UCB) for EECS149/249A

eecs 388: embedded systems - ku ittcheechul/courses/eecs388/w11.security.pdf · simplex...

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