1. Securing IoT with the ARM mbed ecosystem
Xiao Sun / Senior Applications Engineer / ARM
ARM mbed Connect / Shenzhen, China
December 5, 2016

2. Lots of interest in IoT security
Researchers are looking into security of IoT systems
Vulnerabilities are recognized in deployed IoT systems
Fixes are deployed where possible
IoT security is evolving in a positive way as a consequence

3. You can’t do big data unless you trust the little data
IoT will not scale without
trust and
security
Enabling trust and security in IoT devices is an opportunity to create value
With large deployments you must secure all devices
IoT deployments will not scale without trust
Low priority and dynamic
Very few developers have strong security experience
Even if there is no secure data/privacy issues
and must not be made an option
Updates become the malware infection vector
DDOS flatten battery
In the wall This is not the PC world, no reset, no reinstall
Even simple sensors

4. IoT projects need a platform OS
Historically, embedded microcontroller design has had little code or design commonality between systems that enables widespread re-use
The communication, device management and security demands of IoT devices are a disruptive jump in complexity that drives the need to use a platform OS
RTOS
Bespoke middleware integration and application
History of engineering closed systems
Somewhat secure thanks to isolation (SW, communication and physical) and obscurity (low volume)
Very little code reuse and design commonality between systems
These “Embedded” norms can’t survive in a successful connected IoT world
When you add networking everything changes
Exposed systems connected to the internet
Managing high complexity in networking stacks requires code reuse and modern dev approach
MCUs need to become accessible to a larger audience of developers
Few developers have security experience
mbed IoT Device Platform is the best starting point
Development time
Platform OS and modular component middleware
Application
Development time

5. mbed OS security mbed Client mbed TLS mbed uVisor
Covers three main types of threat
Security of system, including ability to provision, manage and update devices (e.g. security fix)
Security of communications between device and cloud services
Security and integrity of device itself from untrusted or malicious code
mbed OS security
mbed Client
Lifecycle security
mbed TLS
Communication security
mbed uVisor
Device security

6. Proportional security
Threat-models should be informed by business requirements
Technology applied and cost expended varies according to application needs
For Example
Risk environment of application
Value of assets to be protected
Trust and control over firmware
Supply chain structure
Lifetime of the device
Application
Security
Disposable
mbed TLS + mbed Connect
Long life node
+ mbed uVisor + active lifecycle management
Critical infrastructure
+ Anti-tamper hardware (ARM SecurCore)
Security is not a black and white thing. It is not either on or off. It must be deployed in proportion to the need for security.
Before security thread-models are defined it is important to have a holistic view of business requirements.
Then appropriate security choices can be made (the cost and effort to be expended on a security solution is a factor here).
Even the most basic application which has static service session information determined at the time of manufacture (e.g. a fixed symmetric key) need fairly sophisticated security functionality. Communication security (as implemented by mbed TLS) enables the device to have basic authentication, confidentiality and integrity for data sent to and from it over the internet. The mbed Cloud Connect service is also provides the security required to use a specific device with a particular cloud application. Many IoT platforms don’t provide much more security than this but at this level it is impossible to securely provision new keys/certificates onto the device or update its firmware. This severely limits the useful lifetime of the device (or risks relying on a device deployment investment with little security protection). Also this limited device security means that valuable secrets can’t safely be stored on the device. As a result this level of security is best suited to disposable devices where the value of device deployment does not need to be maintained and the secrets on the device are low value.
Many applications will demand a larger investment in security. Adding mbed OS uVisor capability enables greater protection of secrets scored on the device and provides greater trust for device identity, integrity. This in combination with mbed Cloud Provision and mbed Cloud Update allows deployed device to flexibly connect to new services and form new secure relationships over its lifetime while keeping pace with changes to security standards and newly discovered protocol vulnrabilites. This protects business investment in large device deployments. At this stage the device can be trusted to implement most common IoT applications and to store important secrets with adequate protection.
Beyond this some specialist applications may require higher levels of security such as resistance to LAB attacks while storing very valluable secrets. This would required the addition of more expensive hardware counter measures and anti-tamper features. This can be supported alongside mbed OS security features.

7. mbed TLS

8. mbed TLS
mbed TLS enables cryptographic and SSL/TLS capabilities for use in embedded software
mbed TLS is tightly integrated into mbed OS
Combined with the mbed uVisor, this provides comprehensive device and communication security for IoT products

9. mbed TLS – Code quality

10. mbed TLS – Code testing Protocol interoperability tests
Behavioural RFC tests
Vulnerability tracking and fixes
Mention mbed TLS website with list of vulnerabilities

11. (pronounced “embed microVisor”)
mbed uVisor
(pronounced “embed microVisor”)

12. mbed uVisor A tiny, hypervisor/microkernel-like security kernel
Creates and enforces secure isolation boundaries within the OS, between different parts of the system
Enables secrets to be strongly protected against software and network-bourn attackers
Efficient hardware enforcement through the memory protection unit (MPU) and ARM TrustZone for v8-M

13. The device security problem
Server
Even simple IoT products have complex components
Secure server communication over complex protocols
Secure firmware updates over the air
Secure device identities
Cryptography APIs and random number generation
Existing IoT solutions use flat address spaces with little privilege separation
Especially on microcontrollers
Application protocol
BLE stack
TLS library
Diagnostics
Secure storage
WiFi stack
Device management
Secure ID
Crypto keys
Crypto API
PRNG
Firmware update

14. The device security problem - Attacker view
Server
Attacker
Flat security models allow attackers to break device security by breaking any system component
Common attack entry points:
Complex protocols like TLS, Wi-Fi or USB device configuration
Firmware update functions (USB, network, CAN…)
Impossible to recover from attacks as firmware update functions can be compromised by the attacker
Application protocol
Third party stacks
BLE stack
TLS library
Diagnostics
Secure storage
WiFi stack
Device management
Secure ID
Crypto keys
Crypto API
PRNG
Firmware update

15. The device security problem - Mitigation strategies
Split security domains into:
Public uncritical code
Protected critical code
Protect key material and system integrity
Use ARMv7-M MPU or TrustZone for v8-M
Keep footprint of critical code small
Public code operates on cryptographic secrets via defined private API
No access to raw keys
Exposed
Critical
Application protocol
TLS library
Diagnose
WiFi stack
BLE stack
Device management
Secure storage
Crypto keys
Secure ID
Firmware update
Crypto API
PRNG

16. The device security problem – Mitigation benefits
Server
Attacker
Attackers can compromise the exposed side without affecting critical code
Cryptographic hashes can be used to verify the integrity of the exposed side
Triggered on server request
Protected security watchdog allows remote control
Protected side can reliably reset exposed side to a clean state
The device attack surface is massively reduced as a result
Exposed
Critical
Application protocol
TLS library
Diagnose
WiFi stack
BLE stack
Device management x
Secure storage
Crypto keys
Secure ID
Firmware update
Crypto API
PRNG x x x x

17. Pulling it together

18. mbed OS
mbed uVisor is part of mbed OS, but is optionally enabled depending on the underlying hardware support
If present, mbed uVisor boots the mbed OS image, and configures secure boxes using the provided access control lists
TLS stack

19. mbed OS security Cloud applications platforms Management security
Data flow management
Deployment management
mbed TLS
Connectivity
service
Provisioning
service
Update
service
The future mbed roadmap will deliver pervasive security across all of our device services (mbed Cloud) and device software (mbed OS; mbed TLS; mbed for X). This security covers many different aspects and exists in may different layers of our mbed IoT Device Platform. Broadly speaking we can categorize all these security aspects into three distinct areas:
Device Security: This comprises of all security aspects implemented in mbed Device Sofware running on IoT end nodes. Our roadmap for this includes SW functionality to implement security related to connectivity, provisioning and device update. These higher level rich protocol/functionality modules will be supported by basic security components that include secure boot; secure storage primitives; low level key management; device identity and cryptographic libraries supporting both full SW implementations and secure interfaces to hardware crypto accelerators. These basic security components can, optionally, reside within and be protected by Trusted Execution Environments (TEE) or secure supervisory kernels such as the mbed OS uVisor when this is supported by the device hardware. This adds additional protection by providing secure isolation of system resources for each software component.
Communication Security: Based on widely deployed and most thoroughly tested security available for internet communication today. mbed Communication Security is implemented by the mbed TLS library which provides all the functionality required to implement the full TLS and DTLS protocols. The mbed TLS library is use in the device software and within the mbed Cloud services. This provide end-to-end communication security from each end node into mbed Cloud across the internet.
Management Security: Implemented within our mbed Cloud services this enables secure lifecycle management for large deployments of end nodes. This will encompass secure device connectivity; secure device provisioning and secure device update services. This is vital to enable IoT deployments to scale. Critically our update service will enable agile security to be implemented across the entire mbed IoT Device Platform. This protects investment in large deployments and enables our IoT security to evolve alongside state of the art internet security. It will also provide secure links into Cloud Application Platforms so that entire IoT applications can be fully secured.
Communication security
mbed TLS
Connectivity client
Provisioning client
Update client
uVisor or TEE
Device security
Crypto
Identity
Keys
Storage
Device hardware

20. Summary IoT deployments will not scale without trust
Very few developers have strong security experience
mbed IoT Device Platform provides a comprehensive security foundation
Device security
Communications security
Lifecycle security