1. Designing a Secure OTA Update Implementation
August, 2018
Nick Lethaby, IoT Ecosystem Manager, Texas Instruments
Richard Barry, Principal Engineer, AWS

2. In this webinar, we will examine
Introduction
An OTA (Over-The-Air) update is a method of distributing and installing new firmware software updates via wireless connections
The ability to perform OTA updates is critical to IoT applications as it allows low-cost patching of bugs and security vulnerabilities, as well as addition of new features
In this webinar, we will examine
The potential for OTA updates to impact security and reliability
An OTA update solution based on an integration of Amazon FreeRTOS with the Texas instruments SimpleLink Wi-Fi microcontrollers and how this addresses security and reliability concerns via:
Cloud-based services
Embedded software
Hardware architecture 1 2

3. OTA Updates: Understanding the risks
IoT Device Vendor
User
IoT Service
Internet
Reliability Risks:
Flawed update crashes IoT device
Power loss during update leaves non-functional image
Remote Network Attack:
Send earlier version of IoT device image as OTA update
Remote Network Attack:
Man-in-the-middle
Remote Network Attack:
Sniff packets
Unauthorized device asking for the update
Local Network Attack:
Sniff packets
22°
Smart Home Device
To deliver a more secure OTA update solution, it’s important to understand the potential attack vectors:
An attacker may obtain the device to acquire physical access in the hope of reading security credentials in storage, analyzing the run-time image for flaws, or copying the run-time image for cloning.
By accessing either via the local network or via the internet, an attacker can use a variety of techniques to trick the IoT device into installing malware rather than a legitimate update.
If an attacker can gain access to the device management service of the IoT device vendor, it would then be possible to send “malware” as an legitimate update.
Remote Network Attack:
Unauthorized OTA operator
Physical Attack:
Extract image or keys from memory
Physical Attack:
Boot malicious image
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

4. AWS Cloud Computing
Cloud computing is the on-demand delivery of compute power, database storage, applications, and other IT resources via the internet with pay-as-you-go pricing.

5. AWS Cloud Computing - OTA

6. AWS IoT Architecture Things Sense & Act Cloud Storage & Compute
Secure local
triggers, actions, and data sync
Secure device connectivity and messaging
Fleet onboarding, management and SW updates
Fleet
audit and protection
IoT data analytics and intelligence
Endpoints
The AWS IoT Core services and AWS Greengrass are the backbone for IoT deployments to securely connect all your devices and handle their data…
But there is more to it.
Once our customers are at scale, they also have to
Maintain their fleet health
Keep their fleets secure
An naturally, they want to easily analyze their IoT data
Gateway
Intelligence Insights & Logic → Action

7. FreeRTOS Kernel

8. Amazon FreeRTOS
Augments FreeRTOS kernel with functionality that enables MCUs to securely connect to cloud services
Completely free to use for any application
Open source MIT license

9. OTA on Amazon FreeRTOS: User Actions
Developer authors update
Upload to cloud and sign image
Schedule an update job
Notify device update is available
Update process is split into three phases
First actions taken by operator
Upload new image to cloud file system called S3.
Sign image
Schedule the OTA at which point the OTA agent is notified

10. OTA on Amazon FreeRTOS: Agent Actions
Developer authors update
Upload to cloud and sign image
Schedule an update job
Notify device update is available
Device downloads image (or streams over MQTT)
Write image to flash
Close file and verify signature
Notify application that new image is ready
Application activates when it is ready (set boot flags and reset)
Second actions taken by agent running on the device
Download and validate signature
Let the application know

11. OTA on Amazon FreeRTOS: Reboot Actions
Developer authors update
Upload to cloud and sign image
Schedule an update job
Notify device update is available
Device downloads image (or streams over MQTT)
Write image to flash
Close file and verify signature
Notify application that new image is ready
Application activates when it is ready (set boot flags and reset)
Verify image at boot
Initialize OTA agent and confirm current image is latest
Hand control to application for self test
On passing self test, commit new image
Update cloud status to completed.
Finally the reboot
Checks the image again
Allows for a self test before committing.

12. OTA on Amazon FreeRTOS: An Overview
AWS Signer Service
AWS IoT Jobs Service
Developer authors update
Upload to cloud and sign image
Schedule an update job
Notify device update is available
Device downloads image (or streams over MQTT)
Write image to flash
Close file and verify signature
Notify application that new image is ready
Application activates when it is ready (set boot flags and reset)
Verify image at boot
Initialize OTA agent and confirm current image is latest
Hand control to application for self test
On passing self test, commit new image
Update cloud status to completed.
AWS IoT
Streaming
Service
Cloud services that interact to perform the OTA.
Now look at these services

13. Code Signing Service
Amazon FreeRTOS OTA updates require a signed image
The IoT device can authenticate the source of the OTA image
The signing service is integrated with the Amazon Certificate Manager (ACM)
Device providers register their code signing certificate with the ACM
Code signing service
Allows device to authenticate the source and integrity of received image
Also uses the Amazon Certificate Manager, with which you register the signing certificate

14. Job Service (Scheduling Updates)
OTA uses the AWS IoT Job Service
The Job Service is used to define a set of remote operations (OTA is the operation in this case)
You specify a list of targets to perform that job (a device group in this case)
Not specific to OTA
Defines remote operations for subsets of devices

15. Thing Groups
Manage several devices/things at once by categorizing them into groups.
Send OTA images to individual devices, or all devices in a group
{ "thingGroups": [ {
"groupName": "LightBulbs",
"groupArn": "arn:aws:iot:us-west-2:thinggroup/LightBulbs" },
"groupName": "RedLights",
"groupArn": "arn:aws:iot:us-west-2:thinggroup/RedLights" ]}
Demonstrate (screen shot) how IoT devices are grouped by whatever attributes are chosen.

16. Device Side OTA Agent
Uses MQTT Streaming Service and all communications through a single TLS connection
Minimizes resource usage by downloading OTA via the existing TLS connection used for MQTT communication with AWS IoT
Simply API
Just start agent on start up
Subscribes to topic
Downloads in background

17. Cloud Operator Security Starts with IAM
Identity and Access Management (IAM) lets you manage access to AWS services and resources securely
Create and manage AWS users and groups
Use permissions to allow and deny their access to AWS resources
Need to protect access to these services
Fine grained control
Same security mechanism as used through AWS access controls.
Every API call made through the control plane API undergoes standard IAM Signature Version 4 authentication and authorization.
Must have permissions to invoke the CreateDeployment, CreateJob, and CreateStream APIs.
[In addition, in your Amazon S3 bucket policy or ACL, you must give read permissions to the AWS IoT service principal so that the firmware update stored in Amazon S3 can be accessed during streaming.]

18. IAM Users, Roles and Policies
SAMPLE POLICY {
"Version": " ",
"Statement": [
"Sid": "FullAccess",
"Effect": "Allow",
"Action": ["s3:*"],
"Resource": ["*"] },
"Sid": "DenyCustomerBucket",
"Effect": "Deny",
"Resource": ["arn:aws:s3:::customer",
"arn:aws:s3:::customer/*" ] } ]
IAM Users allow you to define specific users of an AWS account with different permissions
IAM Roles allow applications to access AWS services programmatically with specified permissions
IAM Policies are documents that define the fine-grained permissions for each IAM User and Role

19. Preventing Unauthorized Job Operators
An OTA User Policy grants your IAM user access to a number of job-related and OTA services.
The following actions are performed during the FreeRTOS OTA workflow, and the following policies are therefore needed the IAM user.
"s3:ListBucket", "s3:ListAllMyBuckets", "s3:CreateBucket", "s3:PutBucketVersioning", "s3:GetBucketLocation", "s3:GetObjectVersion",
"acm:ImportCertificate", "acm:ListCertificates",
"iot:ListThings", "iot:ListThingGroups", "iot:CreateStream",
"iot:CreateOTAUpdate", "iot:GetOTAUpdate", "iot:ListJobs", "iot:ListJobExecutionsForJob", "iot:DescribeJob", "iot:GetJobDocument", "iam:ListRoles",
"signer:ListSigningJobs", "signer:StartSigningJob", "signer:DescribeSigningJob"
All the items an IoT deployment needs access to or permission to perform

20. Managed (Pre-Configured) Access Policies
The OTA Service Role is a role that AWS IoT takes on to perform OTA actions on your behalf
An AWS managed policy is a standalone policy that is created and administered by AWS, making it easier for you to assign appropriate permissions.
Create a role, and add permissions to it using the managed policy called AWSIoTOTAUpdate, which contains the permissions needed for AWS IoT to create jobs and use signed images.
Help is at hand through managed policies
Pre-canned
Groups all the required permissions allowing a single permission to AWSIoTOTAUpdate
Hand over
Nick will show how the CC3220 architecture minimizes overhead, non intrusive

21. SimpleLink Wi-Fi: Architected for better security
Single chip enclosed architecture for reduced attack surface
2 Separate execution environments: MCU + NWP for enhanced assets isolation and easy application integration
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Embedded security features reduce need for external secure components
HW crypto engines enable fast TLS secure connection establishment within 200msec
Cryptographic utilities simplify
sign & verify operations to validate any new image
Encrypted File System for Customer IP/data and end user’s data security
The unique architecture of this device, and its wide range of built-in security features, empower designers to implement a variety of security measures to protect their product from unauthorized theft and malicious control.
The Single Chip enclosed architecture reduces the number of possible attack surfaces commonly observed in systems which have the User-Application MCU externally attached to the wi-fi network processor via an interface such as UART or SPI. In this particular architecture the MCU is integrated within the Silicon
The two on-chip, yet physically separate, execution environments of the user-applications MCU and the Wi-Fi network Processor, allow for enhanced assets isolation between the developers’ IP and the network processor activities.
This device supports personal and enterprise security protocols for the local segment of the network (between the AP and the STA). It supports 16 sockets, out of which 6 can be secured (SSL/TLS protocols).
The Internal HTTPS server runs on top of a TLS socket, with support for client authentication
The Device Identity is an Unmodifiable unique 128-bit number that TI stores in the device during production. It may serve as a unique device identity (UDID).
The trusted Root Certificate catalog is a built-in file, provided and signed by TI, which contains a list of known and trusted root certificate authorities (CAs). It is used to ensure that a CA is trusted as root of certificate chain for the purpose of TLS and for file signing.
The TI root of trust public key is a hardware-based mechanism that allows authenticating TI as the genuine origin of a given content (such as software service pack, trusted root-certificate catalog) using asymmetric keys.
One of the most important embedded HW security features are the Hardware crypto engines. These engines offload the ARM® Cortex®-M4 MCU from the complex and time-consuming arithmetic involved in cryptographic algorithms. The HW crypto engines enable fast secure TLS/SSL connection establishment within 200mSec. These Cryptographic utilities also simplify sign & verify operations to validate the authenticity of any new image. Some of the hardware crypto engine are accessible at the application level. Those crypto engines are: AES, DES, SHA/MD5, and (Cyclic redundancy) CRC.
The device unique-key is a hardware based, readable only by the NWP. IT is used for cloning protection mechanism.
The Debug security enables blocking access to debug capabilities such as JTAG interface and file-by-file access from external tools.
There are numerous built-in software security features that aim to reduce the need for additional external secure components – such as secure MCU or secure elements. File system security features encompasses file encryption, authentication, bundle protection, access control and more. [CLICK] All of the encrypted files for the customer’s IP/data and the consumer’s data can be securely stored on the sFlash. The secure files/data are accessible only by the NWP with the correct access control.
We even enable initial secure programming, which is referring to the fact that an image can be encrypted with a secure key before it is loaded on the board. Then a trusted person can activate the image that is loaded on the device by using Uniflash. … This is Very useful for factory code protection.
Secure boot is used to validate the authenticity of any image before its initial runtime.
Serial Flash
File system security: Encryption, Access control, Authentication, Bundle protection, Software tamper detection, Cloning protection
Initial secure programming
Secure Boot
Software
Hardware Crypto Engine for advanced fast security, including: AES, DES, SHA/MD5, and CRC.
Device-Unique Key
Debug Security: JTAG and Debug Ports can be Locked
Embedded HW
Personal and enterprise security: WPA/WPA2 PSK, WPA2 Enterprise
Full TCP/IP stack with TLS
Embedded HTTPS Server
Unique Device Identity
Trusted Root-Certificate Catalog
Networking

22. Amazon FreeRTOS integration with SimpleLink SDK
SimpleLink connected MCUs have a standard SDK across all devices
The SimpleLink SDK feature extensive run-time libraries that Amazon FreeRTOS leverages in its secure OTA solution
SimpleLink W-Fi Device
Device Drivers
FreeRTOS Kernel
User Applications
Secure Wi-Fi Stack
TLS
TCP/IP
Secure Bootloader (ROM’d)
MQTT Client
OTA Agent
Crypto Utilities
Manage Keys
Accelerators, RNG
Secure Filesystem
Images
Keys
Wi-Fi
Manager

23. OTA reliability: SimpleLink Bundle Protection
Create failsafe files
Amazon FreeRTOS uses the SimpleLink Bundle protection mechanism to avoid OTA updates bricking a device
Amazon FreeRTOS tests the image can connect and communicate with AWS/IoT
Amazon FreeRTOS also provides a hook for developers to add their own testing
Add files to bundle
Write image files to bundle
Restart processor & set watchdog timer
Watchdog timeout
Test
image
Power failure
fail
Rollback back to the previous version
pass
Commit bundle as the new boot image

24. OTA Reliability: Factory Image Recovery
As an additional recovery mechanism to use for malfunctioning or bricked devices, SimpleLink Wi-Fi devices include a capability to restore to a device to a factory image
End Product PCB
If the application MCU is still running and the IoT device has an UI, it can provide an option to reset the network processor to a factory image combined with the most recent service pack downloaded
Serial Flash UI
Factory
Image
SimpleLink Wi-Fi
Current working image
SOP
If the IoT Device is totally unresponsive, both the application MCU and network processor can be reset to a factory image via the SOP (Sense-On-Power) pins.
Slot for next OTA image

25. Hardware Crypto Engines Personal and Enterprise
OTA Update Security Measures
Hardware Crypto Engines
Local network with WPA/WPA2 encryption by the HW crypto engines, offloading the host
Personal and Enterprise
Wi-Fi Security
OTA Security
The SimpleLink device opens a secured Wi-Fi connection to the Access-Point
Local Network Attack:
Sniff packets
Application
Servers
End Product PCB
It is important to first establish a secure local area network connection. This can be done by leveraging the NWP embedded personal and enterprise security features.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT Device Vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

26. Hardware Crypto Engines Secure Sockets (TLS\SSL)
OTA Update Security Measures
Hardware Crypto Engines
HW encryption engines establish a fast TLS/SSL internet connection within <200mSec
Secure Sockets (TLS\SSL)
TLS/SSL are in the NWP, within the BSD Socket layer
OTA Security
The SimpleLink device has a secured TLS connection to the AWS IoT service.
Remote Attack:
Sniff packets
Application
Servers
End Product PCB
To prevent remote packet sniffing, the connection through the internet to the application server will leverage the built-in TLS protocol with hardware crypto engines to quickly establish a secure connection within 200mSec.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT Device Vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

27. OTA Update Security Measures
Hardware Crypto Engines
Trusted Root-Certificate Catalog
Built-in secure mechanism to ensure a CA is trusted as root of certificate chain for TLS purpose and file signing.
TI Root of Trust Public Key
OTA Security
During the TLS connection the server is authenticated to the SimpleLink’s trusted root certificate catalog.
HW-based mechanism that allows authenticating TI as the
genuine origin of a given content, using asymmetric keys.
Application
Servers
Remote Attack:
MITM
End Product PCB
In order to prevent any potential MITM attack, the application server has to be authenticated as a genuine server, against CC3220 trusted certificate catalog, which contains the list of known and trusted root Certificate Authorities (CA)
The CC3220 must also authenticate itself as the genuine origin of any given content, such as the trusted root certificate catalog.
All of this is handled by the NWP.
The signed image generated by AWS and authenticated by the OTA agent (using the CC3220 HW crypto engine) offers further protection against a MITM trying to substitute malware in place of the actual OTA update.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT Device Vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

28. Hardware Crypto Engines
OTA Update Security Measures
Hardware Crypto Engines
Device Identity
Unmodifiable unique 128-bit number that TI burns into the
device during production
OTA Security
The simplelink device uses its unique device identity in order to be validated and approved to continue with a SW update
Application
Servers
Unauthorized device asking for the update
End Product PCB
Although not supported currently by Amazon FreeRTOS OTA at this time, each CC3220 has a unique device identity that can be validated and approved by the application servers, before the application server can authorize the release of the latest software . This unmodifiable 128bit is burned into each device during production. It cannot be modified.
This prevent any unauthorized device from accessing the application server and getting the software update.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT Device Vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

29. OTA Update Security Measures
Hardware Crypto Engines
Unique Key - Cloning Protection
The file system is readable only by the device which first booted the image
File system is encrypted so image cannot be read without the key
File Encryption
File System Security
OTA Security
The updated files access control and authenticity are validated and then stored on the Simplelink’s secured file system
Physical Access Attack:
Read App Code or keys
Physical Access Attack: Copy and run binary on counterfeit HW
IoT Application
Servers
End Product PCB
The new bundle files from the server are decrypted by the NWP, and stored on the sFlash.
It is recommended to store them as encrypted image to prevent any physical access attack to read the app code.
The Device unique-key is leverage by the intrinsic cloning protection mechanism, which ensures that the file system is readable only by the NWP, which first wrote that image to the sFlash. In other words, an encrypted image on the sFlash is only readable by the NWP, it was first attached to.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT device
vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

30. Hardware Crypto Engines Attempt to hijack device by running
OTA Update Security Measures
STORAGE
Hardware Crypto Engines
Validate the integrity and authenticity of the run-time binary
during boot
OTA Security
At boot the application code is
loaded and run on the MCU
Secure Boot
Attempt to hijack device by running
malicious SW
Application
Servers
End Product PCB
The over ther air transfer of the new software image is complete.
The CC3220 will restart with the new image.
First the secure boot will validate the integrity and authenticity of the binary.
If the image is not valid, the device will default to the previously known good image. This is done in order to protect against attempts to hijack the device with malicious SW.
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
Internet
IoT Device Vendor
User
Access Point
RUN-TIME
STORAGE
Local Network Access
Physical Access
Remote Access
TRANSFER

31. SimpleLink Wi-Fi: Multi Layer Security Measures
Secure Content Delivery
Trusted Root-Certificate Catalog
Initial Secure Programming
Secure Sockets (TLS\SSL)
Personal and Enterprise
Wi-Fi Security
Secure Boot
File Encryption
Unique Key - Cloning Protection
Software Tamper Detection
TI Root of Trust Public Key
Device Identity
HTTPS Service
Debug Security
Hardware Crypto Engines
Secure Key Storage
File Authentication
File Access Control
Factory Image Recovery
File Bundle Protection
File System Security
CC3220S, and CC3220SF have several built-in features that will enable you to design products with a variety of security measures to fit the needs for that product’s application. Amazon FreeRTOS uses many of these to deliver its secure OTA update solution.
Application
Servers
End Product PCB
Internet
CC32xx Wireless-MCU
Network Processor
SPI
Power Management
Wi-Fi
Baseband
Radio
MAC
Internet
TLS/SSL
TCP/IP
HTTPS
Applications MCU
ARM Cortex M4 80MHz
256KB RAM +
Opt. 1MB XIP Flash
User
Application
HW Crypto Engine
Serial Flash
IoT Device Vendor
User
Access Point

32. For more information Resources SimpleLink Wi-Fi devices and tools
Getting started with a CC3220SF Launchpad
Review CC3220 technical documents
Amazon FreeRTOS and Secure OTA
AWS IoT

33. Summary
OTA Updates are a critical capability for an IoT device but introduce the potential for security and reliability risks
Amazon offers an end-to-end secure OTA solution based on AWS IoT cloud services and Amazon FreeRTOS embedded software
Amazon FreeRTOS is integrated with the SimpleLink SDK, enabling it to leverage SimpleLink Wi-Fi’s built-in OTA security and reliability features
DATA
CODE