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© 2011 Underwriters Laboratories Inc. Securing Embedded Systems Timothy Sherlock Transaction Security Underwriters Laboratories [email protected]
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Timothy Sherlock Witham Laboratories: Close the door! Securing embedded systems

Jun 10, 2015

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Timothy Sherlock, Security Engineer, UL Transaction Security (formerly Witham Laboratories) delivered this presentation at the 2013 Corporate Cyber Security Summit. The event examined cyber threats to Australia’s private sector and focussed on solutions and counter cyber-attacks. For more information about the event, please visit the conference website http://www.informa.com.au/cybersecurityconference
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Page 1: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

© 2011 Underwriters Laboratories Inc.

Securing Embedded Systems

Timothy Sherlock Transaction Security Underwriters Laboratories

[email protected]

Page 2: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Hardware Security Modules Network Device Security Approval Schemes Summary

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Page 3: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

The Expanding Data Envelope

The way we store and move data around is changing

• Paper ! Computer ! Portable Storage ! Portable Electronic Devices – The ways in which data is secured needs to keep pace – Changes are making data easier to lose

• How do we secure different types of data storage and transmission? – Traditional methods may not be practical, or even effective – Different types of technology have different security requirements

• Attacks on systems are getting easier – Required equipment reducing in price

– Increased availability of attack ‘know-how’

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Page 4: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Hardware Security Modules Network Device Security Approval Schemes Summary

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Page 5: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Portable Storage Security

Flash media has become the ubiquitous method for fast, mobile storage

•  ‘Flash drive’ is now synonymous with USB storage – Defacto way for carrying data on the move

• Also increasingly used as OS and boot media – Solid State Drives (SSDs) becoming cheaper and more popular – Considered functionally equivalent, but faster and quieter

• But operational equivalence != functional equivalence – How do flash drives really work?

– Do traditional erasure methods work on flash drives? – What is the best way to secure data on flash media?

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Page 6: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Why is Flash Different?

Manipulation of written data requires ‘intelligence’ in the Flash media

• Flash memory chips do not have this intelligence themselves – Therefore a ‘flash controller’ is required within the media – This controller manages the USB ! memory interface, and ‘flash transfer layer’ – Maps external access to internal flash memory locations

– This mapping changes as new data is written, modified and erased – Usually an ASIC with embedded general purpose micro-controller (eg 8051)

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USB ASIC

Flash Memory

Chip

Page 7: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Why is Flash Different?

Over-provisioning

• Solid State Drives (SSDs) often include additional flash memory to compensate for slow erasure times ! Increase write performance

– This is called ‘over-provisioning’ – Usually between 15% - 25% of the advertised capacity

• Provides another method for data to be retained after deletion – Disk controller will perform ‘clean-up’ functions when idle, erasing previously used areas of memory which have been re-mapped – Has implications for forensic recovery of data – The ‘trim’ command can be used to initiate this ‘garbage collection’

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Page 8: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Securing Flash Media

So how do you secure your Flash Media?

• Flash media is portable, robust, and ubiquitous – ‘Portable’ + ‘robust’ + ‘ubiquitous’ – Lost media is at best embarrassing, and at worst business destroying … and remember, it’s not just the data you think is there It may be data you have previously erased (even ‘securely’)

• When in doubt, encrypt – Fortunately, numerous options exist for removable media – Can be partitioned into three types: – Software encryption on PC, password/passphrase entered on PC – Hardware encryption on flash disk, password/passphrase entered on PC – Hardware encryption on flash disk, password/PIN entered on flash disk

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│ │ ≡ ‘Losable’

Page 9: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Securing Flash Media

Hardware encryption, password/passphrase entered on USB host (PC)

• Flash controller integrates HW encryption core – Encryption keys may be stored on Flash disk, not be exposed on PC, OR – Encryption keys may be derived from password, and sent to Flash disk – Password always exposed on host platform – Additional software probably required to allow for password transfer – IEEE 1667 specification allows for password interface to USB drives – Not popularly supported, and does not require encryption

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ASIC w HW

Crypto

Encrypted data

Plaintext data (containing driver)

Page 10: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Securing Flash Media

Hardware encryption, password/PIN entered on flash disk

• Flash controller integrates HW encryption core – Encryption keys / password not exposed on PC, no software install on USB host

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Battery

ASIC w HW

Crypto

Flash chip only contains

encrypted data

1

2

3

4

5

6

7

8

9

0

L

U

Page 11: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Securing Flash Media

Software encryption, password/passphrase entered on USB host (PC)

• Standard flash controller, no integrated encryption functions – Encryption keys and password used / exposed on PC – Data stored in encrypted ‘container’ on USB disk – May be whole volume, sub-volume (encrypted container), or file only – Encrypted by software on the PC before transfer to the USB

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Standard USB ASIC

Plaintext data

Encrypted data

Page 12: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Hardware Security Modules Network Device Security Approval Schemes Summary

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Page 13: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

What is a Hardware Security Module?

Hardware Security Modules (HSM) are used for secure storage and use of cryptographic keys

• Traditionally found in banks, telecom providers, and government – Increasingly used by private industry to secure sensitive data

• Generally found in one of two form factors – Separate device that is attached to the company network – Add-on device (PCI-e, USB, etc) that is attached to a computer

• Often thought of as providing ‘absolute’ security – Just how secure are they? – Just how secure do you need them to be?

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Page 14: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Hardware Security Module Use

What does a HSM do?

• Very simply, a HSM encrypts or decrypts data – Using cryptographic keys it stores in some secure manner – Will store at least one key internally – Other keys may be stored externally, but encrypted under this one ‘master’ key

• HSMs also provide an interface for ‘key management’ – Cryptography is only secure if no-one knows the decryption key – Key management encompasses the methods used to generate, distribute, control use and inject the keys into the HSM – Most real-world exploits with cryptography are caused by poor key management

• But HSMs are secure, right?

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Page 15: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Hardware Security Module Use

Cryptographic keys in a HSM are often the ‘keys to the kingdom’

• Exposure of these keys could lead to rapid, total compromise – They’re a small collection of numbers that protect your most sensitive data – There is lots of research into how to extract keys from ‘secure’ devices – An on-going ‘battle’ between attackers and HSM vendors – How do you know if your HSM is ahead of the game?

• FIPS140-2, Common Criteria, PCI HSM, ISO13491 – We’ll talk more about these standards soon – Approval does not mean ‘completely secure’ – But is better than nothing – a HSM without approval is not worth much

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Page 16: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Portable Electronic Device Security Network Device Security Approval Schemes Summary

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Page 17: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Network Devices

Modern devices are now more connected than ever before

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Page 18: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Exploitation of these platforms is nothing new

Security of embedded network devices is receiving more attention

Recent attacks have demonstrated practical attacks against these systems.

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. . . And devices have access to a lot of information

Page 19: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Device Back Doors

A ‘Back Door’ is literally a way to easily penetrate into a system or device

• May be installed by a malicious agent, or a deliberate interface by the manufacturer (to make things ‘easier’!)

• How do you know if your systems have ‘back doors’ or not? -  You don’t! :D

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Page 20: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Surely the big players are getting this right?

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Remote code execution vulnerabilities found in cisco and HP switches within the last year

The patches are out there, but does your corporate patching strategy cover these devices?

Issues around the patching of vulnerable devices complicated by access methods and availability requirements

The big players are sorting this out, small players are catching up as these issues mature

Page 21: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Poor Entropy in Random Data Generation

Entropy is the randomness gathered by the operating system.

• General purpose operating systems gather entropy from many sources.

• Where do embedded systems gather their random data from? -  Limited time to gather entropy -  Limited sources of entropy

What does this mean for the operational embedded device? -  Weak keys generated for cryptographic operations -  Researched has detected many vulnerable products in this space

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Page 22: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Portable Electronic Device Security Network Device Security Approval Schemes Summary

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Page 23: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

Lots of internationally recognised approval schemes for secure systems

• FIPS 140-2

• Common Criteria

• PCI Standards

What do they provide? •  If a device is ‘approved’ to one of these schemes, is it secure?

• What are the boundaries of these programs in regards to device security? -  Do they all test for the security features we have discussed?

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Page 24: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

FIPS 140-2

• Provides confirmation of correct operation of cryptographic primitives

• Four levels of approval (L1 ! L4)

• L1 and L2 provide little to no requirements for physical protection -  Can be applied to software only systems

• L3 systems require some tamper detection for covers and doors -  Requirements do not allow for cutting of casing to access switches

• L4 systems require a ‘tamper envelope’ that encloses all sensitive circuitry -  Also requires environmental detection for extreme temperature / voltage -  No formalised feasibility criteria for attacks

• None of the levels require side channel protections -  May be part of FIPS 140-3

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Page 25: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

FIPS 140-2: Know what you are getting

• Approved devices on the FIPS Validated Module List

• All devices must be provided with a ‘security policy’ document -  Details the scope of approval -  May be different from what the device is being marketed and used for -  Also provides information on assumptions made during evaluation on tamper

evidence checks and installed environment

• Approval certificate details individual levels for each area of standard -  May be approved to L3 in some area (eg, EMI) but only L1 in some others (eg,

physical security)

• Essentially, FIPS is not a security standard -  Is a validation standard for cryptographic operations -  Relies on correct installation and use ! validated through Common Criteria

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Page 26: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

Common Criteria

• Open framework for evaluations

• Evaluations based on set of criteria -  Generally developed between lab, vendor, and Certification Body -  Pre-generated criteria exist in form of ‘Protection Profiles’ -  Can be extended or supplanted entirely with additional criteria to form a

‘Security Target’

• Different levels of validation (Evaluation Assurance Levels – EAL) -  L1 ! L7 -  L1 very light weight, L7 very involved -  Mutual cross-country recognition of L4 and below

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Page 27: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

Common Criteria

• Standardised attack feasibility costing used for some PP/ST evaluations -  Based on Common Evaluation Methodology (CEM) document -  Provides points based costing for different types of attack -  Highest level required by AVA_VAN.5 requirement

• Side channel and invasive attack methods required for some PP/ST -  Most common in chip level evaluations

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Page 28: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

Common Criteria: Know what you are getting

• Without knowledge of PP/ST used, CC approval itself means nothing -  All testing requirements are scoped in ST -  Ensure that these mitigate against your risk profile

• Standardised attack costing is valuable -  But not used in all evaluations

• Side channel requirements are valuable -  But not standardised (difficult to do, FIPS working on this)

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Page 29: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Approval Schemes

PCI Standards

• PCI DSS audits system/people/processes to ensure the minimum controls required to protect cardholder data are in place

• Must -  Run a holistic information security program -  Protect cardholder data (stored, processed or transmitted)

• Common practice is to segment the network to reduce the scope of evaluation.

• Compliant organisation find utility in applying PCI DSS requires to other parts of their network. This makes sense as PCI DSS is just “basic information security”.

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Page 30: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Agenda

The Expanding Data Envelope Portable Storage Security Portable Electronic Device Security Data Extraction and Recovery Approval Schemes Summary

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Page 31: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

Summary

Nothing is secure

• Security is a level, not an absolute -  Understand the level you require your security to be at -  Ensure that any systems you use meet this

• All attacks are easier than you think -  And generally only getting easier

• Understand what approval schemes are providing -  Not all approvals indicate security -  Even those that do may indicate security in different areas to those you require

•  Don’t worry about the cryptography failing -  Worry about the implementation failing

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Page 32: Timothy Sherlock  Witham Laboratories: Close the door! Securing embedded systems

THANK YOU.