Temporal Consistency of Integrity-Ensuring Computations and - - PowerPoint PPT Presentation

▶
temporal consistency of integrity ensuring computations
SMART_READER_LITE
LIVE PREVIEW

Temporal Consistency of Integrity-Ensuring Computations and - - PowerPoint PPT Presentation

Dec 14, 2023 29 likes •412 views

Temporal Consistency of Integrity-Ensuring Computations and Applications to Embedded Systems Security Karim Eldefrawy Xavier Carpent Norrathep (Oak) Rattanavipanon Gene Tsudik University of California, Irvine SRI International Agenda

slide-1
SLIDE 1

Temporal Consistency of Integrity-Ensuring Computations and Applications to Embedded Systems Security

Xavier Carpent Norrathep (Oak) Rattanavipanon Gene Tsudik

University of California, Irvine SRI International

Karim Eldefrawy

slide-2
SLIDE 2

Agenda

  • Problem Statement
  • Remote Attestation
  • Temporal Consistency: Definition & Motivation
  • Temporal Consistency Methods
  • Implementation and Experiments
  • Conclusions + Future Work

2 June 5, 2018 AsiaCCS'18

slide-3
SLIDE 3

Problem Statement

3 June 5, 2018 AsiaCCS'18

slide-4
SLIDE 4

Integrity-Ensuring Computation

  • Output can be used to validate integrity of input data
  • Examples of F : cryptographic hash functions, message authentication codes

(MAC)

4

Integrity-ensurin g function (F)

Input

Output

June 5, 2018 AsiaCCS'18

slide-5
SLIDE 5

Integrity-Ensuring Computation

5

Output must be temporally consistent: ❖Must faithfully reflect exact state of all of input data at some point (or interval) in time Computation on large input data: ❖Not instantaneous; input may change while computation takes place

June 5, 2018 AsiaCCS'18

slide-6
SLIDE 6

Integrity-Ensuring Computation

6

Sender

F F

=? =? (1) (2)

✓

Receiver

F

✘

F

June 5, 2018 AsiaCCS'18

Changes (red dots) in input happen in middle

  • f F
slide-7
SLIDE 7

Integrity-Ensuring Computation

7

Sender

F F

=? (1) (2)

✓

Receiver

F

=

F

Never existed as a whole and might be non-sensical

June 5, 2018 AsiaCCS'18

slide-8
SLIDE 8

Integrity-Ensuring Computation

8 Especially, when performed on simple embedded (IoT) devices with safety-critical applications. Use-case: Remote Attestation Output must be temporally consistent: ❖ Must faithfully reflect exact state of all

  • f input data at some point (or

interval) in time ฀ Atomicity of computation of F guarantees temporal consistency (assume singe CPU) Computation on large input data: ❖ Not instantaneous; input may change while computation takes place ฀ Atomic computation of F might be impractical and/or unsafe

June 5, 2018 AsiaCCS'18

slide-9
SLIDE 9

Overview of Remote Attestation

9 June 5, 2018 AsiaCCS'18

slide-10
SLIDE 10

Remote Attestation (RA)

  • Security service for remotely assessing integrity of firmware/software

in embedded devices

  • Verifier – trusted entity
  • Prover – potentially infected remote embedded device

10

(1) Challenge (3) Response (4) Verify response and determine presence of malware

  • n Prover

Verifier Prover

(2) Measure memory

Integrity-ensuring function: (H)MAC

  • r signature

June 5, 2018 AsiaCCS'18

slide-11
SLIDE 11

Example of RA for Embedded Devices

SMART [NDSS’12,DATE’14]

  • HW/SW co-design for RA targeting

micro-controller unit (MCU)

  • Minimal change in MCU

Property HW/SW Immutability ROM Exclusive Access to K MCU Access Control No Leak Static Analysis

Controlled Invocation

MCU Access Control Uninterruptibility Disabled Interrupts

11 June 5, 2018 AsiaCCS'18

slide-12
SLIDE 12

Example of RA for Embedded Devices

SMART [NDSS’12,DATE’14]

  • HW/SW co-design for RA targeting

micro-controller unit (MCU)

  • Minimal change in MCU

Property HW/SW Immutability ROM Exclusive Access to K MCU Access Control No Leak Static Analysis

Atomicity

MCU Access Control Disabled Interrupts

12

Temporal consistency is achieved via atomicity but … … Atomicity makes SMART impractical for safety-critical devices

June 5, 2018 AsiaCCS'18

slide-13
SLIDE 13

Property HW/SW Immutability ROM Exclusive Access to K MCU Access Control No Leak Static Analysis

Atomicity

MCU Access Control Disabled Interrupts

Example of RA for Embedded Devices

SMART [NDSS’12,DATE’14]

  • HW/SW co-design for RA targeting

micro-controller unit (MCU)

  • Minimal change in MCU

TrustLite [EuroSys’14]

13

Property HW/SW Immutability ROM Exclusive Access to K MPU No Leak CPU Exception Engine Controlled Invocation CPU Exception Engine + OS Secure Interrupts CPU Exception Engine

  • Allow secure interrupt during

attestation

  • Use execution-aware memory

protection unit to enforce access control Temporal consistency is achieved via atomicity but … … Atomicity makes SMART impractical for safety-critical devices

June 5, 2018 AsiaCCS'18

slide-14
SLIDE 14

Property HW/SW Immutability ROM Exclusive Access to K MCU Access Control No Leak Static Analysis

Atomicity

MCU Access Control Disabled Interrupts

Example of RA for Embedded Devices

SMART [NDSS’12,DATE’14]

  • HW/SW co-design for RA targeting

micro-controller unit (MCU)

  • Minimal change in MCU

TrustLite [EuroSys’14]

14

Property HW/SW Immutability ROM Exclusive Access to K MPU No Leak CPU Exception Engine Controlled Invocation CPU Exception Engine + OS Secure Interrupts CPU Exception Engine

  • Allow secure interrupt during

attestation

  • Use execution-aware memory

protection unit to enforce access control Temporal consistency is achieved via atomicity but … … Atomicity makes SMART impractical for safety-critical devices Allowing attestation to be interruptible helps with safety-critical devices but … … Temporal consistency may not be achieved in TrustLite

Our goal: resolve this conflict

June 5, 2018 AsiaCCS'18

slide-15
SLIDE 15

Modeling Temporal Consistency in Remote Attestation

slide-16
SLIDE 16

Modeling Temporal Consistency in Remote Attestation

16

F

June 5, 2018 AsiaCCS'18

slide-17
SLIDE 17

Modeling Temporal Consistency in Remote Attestation

  • Block size of F = memory block size, e.g., 512 bits for HMAC-SHA256
  • F is a sequential function: process each block once and in order
  • Content of blocks may change during execution of F

17

F

June 5, 2018 AsiaCCS'18

slide-18
SLIDE 18

Attestation Task

Modeling Temporal Consistency in Remote Attestation

  • 18

write

Task A

F

June 5, 2018 AsiaCCS'18

slide-19
SLIDE 19

Types of Malware

Migratory Malware

  • Transient Malware
  • Ability: erase itself at any point during

computation of F

  • Goal: escape detection
  • Detection: R is consistent at start of

computation

19

R is consistent at time t and R corresponds to benign state → no malware was present at time t

  • Detection: R is consistent at any time

throughout computation

June 5, 2018 AsiaCCS'18

slide-20
SLIDE 20

Mechanisms for Ensuring Temporal Consistency

20 June 5, 2018 AsiaCCS'18

slide-21
SLIDE 21

Strawman Approach

  • 21

June 5, 2018 AsiaCCS'18

slide-22
SLIDE 22

Mechanism 1: All-Lock

  • 22

Timelin e

June 5, 2018 AsiaCCS'18

slide-23
SLIDE 23

Mechanism 2: Dec-Lock

  • 23

Timelin e

June 5, 2018 AsiaCCS'18

slide-24
SLIDE 24

Mechanism 3: Inc-Lock

  • 24

Timelin e

June 5, 2018 AsiaCCS'18

slide-25
SLIDE 25

Mechanism 4: Cpy-Lock

  • 25

June 5, 2018 AsiaCCS'18

slide-26
SLIDE 26

Malware Detection Summary

26

Mechanism Migratory Malware Transient Malware No-Lock No No All-Lock Yes Yes Dec-Lock Yes Yes Inc-Lock Yes No Cpy-Lock Yes Yes

June 5, 2018 AsiaCCS'18

slide-27
SLIDE 27

Inconsistency Detection

  • Alternative to enforce consistency
  • Memory is not locked during computation of F …
  • …But attestation task is alerted when memory is modified during computation of F
  • Pro:
  • No need to handle memory access violations
  • No interference with execution of other tasks
  • Con:
  • Inconsistency may always happen (even by benign task) → consistency is never achieved

27 June 5, 2018 AsiaCCS'18

slide-28
SLIDE 28

Implementation and Evaluation

slide-29
SLIDE 29

Implementation

  • Memory locking requires hardware support
  • Dynamically configurable memory protection unit (MPU) → TyTan [DAC’15]
  • Memory management unit (MMU) → HYDRA [WiSec’17]
  • Implement mechanisms on HYDRA
  • Evaluate run-time on I.MX6-SabreLite and ODROID-XU4

29

I.MX6-SabreLite ODROID-XU4

June 5, 2018 AsiaCCS'18

slide-30
SLIDE 30

Primitive Operations on 16MB Memory Size

30

Lock, unlock and copy are at least 10 times faster than MAC

June 5, 2018 AsiaCCS'18

slide-31
SLIDE 31

Primitive Operations on 16MB Memory Size

31

Larger block size → faster lock and unlock process

June 5, 2018 AsiaCCS'18

slide-32
SLIDE 32

Mechanisms Ensuring Temporal Consistency

32

Block size = 4KB Block size = 64KB

Overhead is at most 8% Overhead becomes < 0.1%

June 5, 2018 AsiaCCS'18

slide-33
SLIDE 33

Conclusions & Future Work

  • Discrepancy between theoretical assumptions and implementations of

cryptographic integrity-ensuring function

  • Input may change during computation
  • Output is not temporally consistent with input
  • Model consistency in context of remote attestation
  • Propose various mechanisms based on memory locking to ensure

consistency

  • Implement and evaluate them on two commodity platforms
  • Future work includes:
  • Implementation of our mechanisms on different RA architecture (e.g., TyTan)
  • Software-based (or minimal hardware-based) mechanisms ensuring consistency

33 June 5, 2018 AsiaCCS'18

slide-34
SLIDE 34

Questions?

Contact: nrattana@uci.edu Our lab: sprout.ics.uci.edu

34 June 5, 2018 AsiaCCS'18

slide-35
SLIDE 35

Uninterruptability vs Memory Locking

  • 35

June 5, 2018 AsiaCCS'18

slide-36
SLIDE 36

Memory Access Violations

  • 36

June 5, 2018 AsiaCCS'18

slide-37
SLIDE 37

HYDRA Architecture

37

seL4 Microkernel Attestation Process (PAttest) Task 1 Task 2 Task 3 Task 4 Hardware-Enforced Secure Boot

Initialize Check for integrity and then initialize

User-space

▪ Has highest priority ▪ Has access to all memory blocks ▪ Distribute memory access capabilities (caps) during init ▪ Can change/revoke caps at run-time

June 5, 2018 AsiaCCS'18

slide-38
SLIDE 38

Integrity-Ensuring Computation

38

Sender

F F

=? =? (1): (2):

✓

Receiver

F

✘

F

June 5, 2018 AsiaCCS'18

Changes (red dots) in input happen in middle

  • f F