SFI Step-by-step on B-U585I-IOT02A

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SFI Step-by-step on B-U585I-IOT02AClock.png75min

Target description

This tutorial shows how to use SFI for installing a simple LED Blink example to B-U585I-IOT02A.

The process goes through three 'steps' at the Original Equipment Manufacturer (OEM) and the Contract Manufacturer (CM) sites.

  • Development @ OEM  : the application code that will run on STM32 is generated.
  • Secure Room @ OEM  : code prepared during the development is encrypted and packaged to be sent for manufacturing. The Secure Room is isolated and its resources are not visible outside of it.
  • Manufacturing @ CM : the encrypted code received by the OEM Secure Room is installed using SFI tools.


Prerequisites

Hardware

  • B-U585I-IOT02A[1] Discovery kit for IoT node with STM32U5 series
  • STM32-HSM[2] SAM for Secure Firmware Installation
  • SmartCard Reader
    • Laptop Built-in
    • External
  • STLINK-V3[3] modular in-circuit debugger and programmer for STM32/STM8
  • 2 x USB cable Type-A to Micro-B
  • Jump wires

Software

  • STM32CubeProgrammer[4] Software programming tool for STM32 (v2.90 min)
    • Including STM32TrustedPackageCreator
  • STM32CubeU5[5] STM32Cube MCU Package for STM32U5 series
  • STM32CubeIDE[6] Integrated Development Environment for STM32

Literature

  • AN4992 STM32 MCUs secure firmware install (SFI) overview
  • UM2237 STM32CubeProgrammer software description
  • UM2238 STM32 Trusted Package Creator tool software description
  • AN5054 Secure programming using STM32CubeProgrammer
  • AN2606 STM32 microcontroller system memory boot mode
  • RM0456 STM32U575/585 Arm®-based 32-bit MCUs
  • UM2839 Discovery kit for IoT node with STM32U5 Serie
  • UM2448 STLINK-V3SET debugger/programmer for STM8 and STM32



1. Environment setup

Before starting, the first step is to prepare the environment to go through the SFI process.

Info white.png Information
For the sake of this demonstration, we are considering the same machine will act as both OEM Development, OEM Secure Room, and CM Manufacturing tool. In a real scenario, these agents will most probably be separated entities.
Info white.png Information
This page describes how to use SFI on B-U585I-IOT02A. It can be easily tailored to any other supported device and development board


1.1. Install STM32CubeProgrammer and STM32TrustedPackageCreator

Clock.png5min

STM32CubeProgrammer (STM32CubeProg) is an all-in-one multi-OS software tool for programming STM32 products. STM32CubeProgrammer provides an easy-to-use and efficient environment for reading, writing and verifying device memory through both the debug interface (JTAG and SWD) and the bootloader interface (UART, USB DFU, I2C, SPI, and CAN).

STM32TrustedPackageCreator is part of the STM32CubeProgrammer tool set, and allows the generation of secure firmware and modules to be used for STM32 secure programming solutions.

  1. Download the latest version of STM32CubeProg[4]
    Security Download STM32CubePROG.png
  2. Unzip the downloaded file and launch the SetupSTM32CubeProgrammer-xxx.exe corresponding to your OS, and follow the instructions.

Make to sure to select STM32TrustedPackageCreator add-on during the installation of STM32CubeProgrammer

Security TrustedPackageCreator.png


STM32CubeProgrammer and STM32TrustedPackageCreator are now installed on your computer.

Warning white.png Warning
Make sure to have the folder including 'STM32_Programmer_CLI.exe' and 'STM32TrustedPackageCreator_CLI.exe' in your PATH.
  • Typical path in Windows : C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin

1.2. Install STM32CubeMX

Clock.png 10min
STM32CubeMX is a graphical tool that allows an easy configuration of STM32 microcontrollers and the generation of the corresponding initialization C code through a step-by-step process.
Please refer to the STM32CubeMX install on the Step1 Tools installation
STM32CubeMX is now installed on your computer.


1.3. Install STM32CubeIDE

Clock.png 10min
STM32CubeIDE is an Integrated Development Environment for STM32

Please refer to the STM32CubeIDE install on the article: Step1 Tools installation

2. Development @ OEM

The first step of the process is to create a demo LED Blink application for B-U585I-IOT02A.

Info white.png Information
In this page we will use STM32CubeIDE, but the process is valid for any other compatible toolchain
Info white.png Information
You could use your own working application binary for B-U585I-IOT02A instead.
Warning white.png Warning
Please note: the STM32 SFI process can only perform secure programming in user Flash memory

firmware using Arm® TrustZone® - the application code must be TrustZone compatible.


3. Download STM32CubeU5 Firmware package

Clock.png 10min
For this step we will use the GPIO_IOToggle_TrustZone project example included in STM32CubeU5 [5] MCU package. STM32CubeU5 MCU Package includes the STM32Cube hardware abstraction layer (HAL) and the low-layer (LL) APIs, plus a consistent set of middleware components (Azure RTOS USBX, FileX/LevelX,ThreadX, NetX Duo, USB Power Delivery, TF‑M, mbed-crypto, Touch library, Network library, and OpenBootloader). All embedded software utilities are delivered with a full set of examples running on STMicroelectronics boards.

  • Open STM32CubeMX
  • Click Manage embedded software packages in Help
  • In the STM32Cube MCU Packages tab, check the last STM32CubeU5 release version
  • Click Install (it may take a long time)
Download STM32CubeU5.png


STM32CubeU5 MCU package is now installed on your computer (typical location C:\Users\myname\STM32Cube\Repository\STM32Cube_FW_U5_Vx.xx.x).

3.1. Configure the GPIO_IOToggle_TrustZone Project included in STM32CubeU5

Clock.png 5min
Open the .project included in <STM32CubeU5 FOLDER>\Projects\B-U585I-IOT02A\Examples\GPIO\GPIO_IOToggle_TrustZone\STM32CubeIDE\ wiht STM32CubeIDE.

  • From Project explorer, click on GPIO_IOToggle_TrustZone_NonSecure , then right click and select Properties
  • Navigate to C/C++ Build > Settings > Tool Settings > MCU Post build output
  • Make sure Convert to binary file (-O binary) is checked
  • Click Apply and Close
cubeIDE convert to binary

3.2. Build the project

Clock.png 2min
From Project explorer, click on GPIO_IOToggle_TrustZone_NonSecure , then right click and select Build Project This will trigger the compilation of both GPIO_IOToggle_TrustZone_Secure and GPIO_IOToggle_TrustZone_NonSecure projects (in this order).

Copy the Secure and NonSecure binaries to the 'ROOT_FOLDER' - in this example the binaries are available in:

  • Projects\B-U585I-IOT02A\Examples\GPIO\GPIO_IOToggle_TrustZone\STM32CubeIDE\NonSecure\Debug\GPIO_IOToggle_TrustZone_NonSecure.bin
  • Projects\B-U585I-IOT02A\Examples\GPIO\GPIO_IOToggle_TrustZone\STM32CubeIDE\Secure\Debug\GPIO_IOToggle_TrustZone_Secure.bin

4. Secure Room @ OEM

In the Secure Room the following two steps are performed:

  • SFI package generation: the code prepared during the development is encrypted and packaged to be sent for manufacturing.
  • HSM Provisioning: the HSM is provisioned with the keys used for encryption and with the max license counter.
Warning white.png Warning
The assumption is that the Secure Room is isolated and its resources are not accessible from the outside world.


4.1. SFI package generation

Clock.png10min

In this step, the application binary file (including S and NS application) and the option byte configuration are encrypted in an SFI package.

The following inputs are needed:

  • Secure and Non-Secure Application Binary files (created in the previous step) and dowload addresses in FLASH.
  • AES Key
  • Nonce
  • Option bytes

4.1.1. Download address

Each binary composing the OEM application is designed to be executed from a specific address in FLASH. The SFI process ensures that each binary is downloaded at the address specified as input parameter.

  • For this example we will use:
    • 0x0C000000 for GPIO_IOToggle_TrustZone_Secure
    • 0x08100000 for GPIO_IOToggle_TrustZone_NonSecure

4.1.2. Key generation

First step is to create secret keys and the nonce that will be used by STM32TrustedPackageCreator to encrypt the firmware image in the SFI package and will be programmed in the STM32-HSM.

Info white.png Information
In this page we will use dummy values, the OEM can create its own keys with arbitrary values
4.1.2.1. AES Key
  1. Create a new text file
  2. Paste the following text
    3. AES_KEY_TEST_001
    The corresponding hex values are: 41 45 53 5F 4B 45 59 5F 54 45 53 54 5F 30 30 31
  3. Save it as aeskey.bin
Warning white.png Warning
The OEM is responsible for keeping this key SECRET - the confidentiality of the solution relies on this.
4.1.2.2. AES Nonce
  1. Create a new text file
  2. Paste the following text
    3. NONCE_TEST01
    The corresponding hex values are: 4E 4F 4E 43 45 5F 54 45 53 54 30 31
  3. Save it as nonce.bin

4.1.3. Option bytes

Together with installing the application binary, SFI process can be used to specify the OB values to be configured at the end of the installation process.

  1. Create a new text file
  2. Paste the following text
    3. OPTR,0x9FEFF8DC
NSBOOTADD0R,0x0800007F
NSBOOTADD1R,0x0BF9007F
SECBOOTADD0R,0x0C00007C
SECWM1R1,0xFFFFFF80
SECWM1R2,0x7F807F80
WRP1AR,0xFF80FFFF
WRP1BR,0xFF80FFFF
SECWM2R1,0xFF80FF81
SECWM2R2,0x7F807F80
WRP2AR,0xFF80FFFF
WRP2BR,0xFF80FFFF
  3. Save it as ob.csv.

In the following a description of the values

  • FOPTSR_PRG,0x9FEFF8DC
    • TZEN  : 0x1 (Global TrustZone security enabled)
    • IO_VDDIO2_HSLV : 0x0 (High-speed IO at low VDDIO2 voltage feature disabled (VDDIO2 can exceed 2.5 V))
    • IO_VDD_HSLV  : 0x0 (High-speed IO at low VDD voltage feature disabled (VDD can exceed 2.5 V))
    • PA15_PUPEN  : 0x1 (USB power delivery dead-battery disabled/ TDI pull-up activated)
    • nBOOT0  : 0x1 (nBOOT0 = 1)
    • nSWBOOT0  : 0x1 (BOOT0 taken from PH3/BOOT0 pin)
    • SRAM2_RST  : 0x1 (SRAM2 is not erased when a system reset occurs)
    • SRAM2_ECC  : 0x1 (SRAM2 ECC check disabled)
    • SRAM3_ECC  : 0x1 (SRAM3 ECC check disabled)
    • BKPRAM_ECC  : 0x1 (Backup RAM ECC check disabled)
    • DBANK  : 0x1 (Dual bank mode with 64 bits data)
    • SWAP_BANK  : 0x0 (Bank 1 and bank 2 address are not swapped)
    • WWDG_SW  : 0x1 (Software window watchdog)
    • IWDG_STDBY  : 0x1 (IWDG counter active in standby mode)
    • IWDG_STOP  : 0x1 (IWDG counter active in stop mode)
    • IWDG_SW  : 0x1 (Software independant watchdog)
    • SRAM134_RST  : 0x1 (SRAM1, SRAM3 and SRAM4 not erased when a system reset occurs)
    • nRST_SHDW  : 0x1 (No reset generated when entering the Shutdown mode)
    • nRST_STDBY  : 0x1 (No reset generated when entering Standby mode)
    • nRST_STOP  : 0x1 (No reset generated when entering Stop mode)
    • SRAM2_PE  : 0x1 (SRAM2 parity check disable)
    • BOR_LEV  : 0x0 (BOR Level 0, reset level threshold is around 1.7 V)
    • RDP  : 0xDC (Level 1)


  • NSBOOTADD0R,0x0800007F
    • NSBOOTADD0  : 0x100000(0x8000000)
  • NSBOOTADD1R,0x0BF9007F
    • NSBOOTADD1  : 0x17F200(0xBF90000)
  • SECBOOTADD0R,0x0C00007C
    • SECBOOTADD0  : 0x1800C0 (0xC006000)
    • BOOT_LOCK  : 0x0 (Boot based on the pad/option bit configuration)
  • SECWM1R1,0xFFFFFF80
    • SECWM1_PSTRT : 0x0 (0x8000000)
    • SECWM1_PEND  : 0xFF (0x81FE000)
  • SECWM1R2,0x7F807F80
    • HDP1_PEND  : 0x0 (0xC001FFF)
    • HDP1EN  : 0x0 (No HDP area 1)
  • WRP1AR,0xFF80FFFF
    • WRP1A_PSTRT  : 0x7F (0x80FE000)
    • WRP1A_PEND  : 0x0 (0x8000000)
    • UNLOCK_1A  : 0x1 (WRP1A start and end pages unlocked)
  • WRP1BR,0xFF80FFFF
    • WRP1B_PSTRT  : 0x7F (0x80FE000)
    • WRP1B_PEND  : 0x0 (0x8000000)
    • UNLOCK_1B  : 0x1 (WRP1B start and end pages unlocked)
  • SECWM2R1,0xFF80FF81
    • SECWM2_PSTRT : 0x1 (0x8102000)
    • SECWM2_PEND  : 0x0 (0x8100000)
  • SECWM2R2,0x7F807F80
    • HDP2_PEND  : 0x0 (0xC101FFF)
    • HDP2EN  : 0x0 (No HDP area 2)
  • WRP2AR,0xFF80FFFF
    • WRP2A_PSTRT  : 0x7F (0x81FE000)
    • WRP2A_PEND  : 0x0 (0x8100000)
    • UNLOCK_2A  : 0x1 (WRP2A start and end pages unlocked)
  • WRP2BR,0xFF80FFFF
    • WRP2B_PSTRT  : 0x7F (0x81FE000)
    • WRP2B_PEND  : 0x0 (0x8100000)
    • UNLOCK_2B  : 0x1 (WRP2B start and end pages unlocked)


Info white.png Information
You can refer to RM0456 for details on OB register values.

4.1.4. Output generation

Now we have all the parameters needed for the creation of the SFI package with the following command 

STM32TrustedPackageCreator_CLI.exe -sfi -fir GPIO_IOToggle_TrustZone_Secure.bin 0x0C000000 -fir GPIO_IOToggle_TrustZone_NonSecure.bin 0x08100000 -k aeskey.bin -n nonce.bin -ob ob.csv -v 1 --ramsize 0x8000 --token 0x0C080000 -o U585_LedBlink.sfi

The command will create the U585_LedBlink.sfi package (you can change the verbose level of the command with the parameter -v 1,2,3)

SFI cmd generation U585


4.2. HSM programming

Clock.png10min

The programming step consists in the provisioning to the HSM of the following parameters:

  • AES Key
  • Nonce
  • Personalization data
  • ID
  • License counter

4.2.1. Preparation

AES Key and Nonce have been generated in the previous step - in this section we will focus on the remaining parameters.

4.2.1.1. Personalization data

The first step for HSM programming is to retrieve the personalization data for the smartcard: with this step, the specific STM32-HSM will allow the installation of SFI images to a specific STM32 family of products. This allows the OEM to add an additional control on the STM32 parts that will be manufactured by the CM.

To perform this operation the user first needs to know the product ID of the device.

  1. Connect the B-U585I-IOT02A board with the micro USB cable through CN1
  2. Retrieve the STM32 device certificate 
    STM32_Programmer_CLI.exe -c port=SWD mode=UR -gc U585_certificate.bin
    File:SFI cmd get certificate U585.png

  3. Open the U585_certificate.bin file with a hex editor and read the first 8 bytes (i.e. the product ID) - for U585 it will be 48202000
    4. SFI U585 certificate

  4. Browse now to the folder C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin\PersoPackages and look for the binary file with the corresponding name - in this case the parameter for the command will be
    C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin\PersoPackages\48202000_SFI._01000000_00000000.enc.bin
4.2.1.2. ID

The ID is a tag name for the HSM card (i.e. for the secret key) that could be useful to the CM when multiple cards are being used in manufacturing.

  • For this example we will use: U585_test_id
4.2.1.3. License counter

License counter is the max number of devices that can be programmed with this HSM.

  • For this example we will use: 300
Info white.png Information
Please note that the max value of the counter depends on the specific STM32-HSM you are using - you can refer to the documentation for additional information

4.2.2. Provisioning

Now that we have defined the parameters, we can proceed with the provisioning of the STM32-HSM.

Warning white.png Warning
The HSM can be programmed just once and this operation is irreversible.

The HSM must be in OEM STATE. If the HSM is already programmed and there is a new attempt to reprogram it, an error message being displayed to indicate that the operation failed and the HSM is locked.

  1. Plug the HSM into the smart card reader
  2. We can get the state of the HSM with the command: 
    STM32TrustedPackageCreator_CLI.exe -hsm -i 1 -info
    Security SFI cmd HSM get info OEM STATE.png

  3. Provision the HSM : 
     STM32TrustedPackageCreator_CLI.exe -hsm -i 1 -k aeskey.bin -n nonce.bin -id "U585_test_id" -mc 300 -pd 'C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin\PersoPackages\48202000_SFI._01000000_00000000.enc.bin'
    SFI cmd HSM perso U585

Warning white.png Warning
At this step the HSM is programmed and in OPERATIONAL_STATE.

You can get the state of the HSM with the command: 

STM32TrustedPackageCreator_CLI.exe -hsm -i 1 -info
SFI cmd HSM get info OPERATIONAL STATE U585


The HSM is ready to be shipped to the CM together with the U585_LedBlink.sfi package created before.

5. Manufacturing @ CM

Clock.png6min

In this step, the CM receives from the OEM the HSM card provisioned with the secret key and initialized with a max counter of licenses, and the .sfi package to be installed (including the firmware in encrypted form and the option bytes configuration).

The SFI process could be performed through a regular JTAG/SWD interface or through the system bootloader interface (you can refer to AN2606 for details on the supported interface for each microcontroller). The following section will cover JTAG/SWD, USART, and SPI interfaces - each section will include the following sections :

  • Hardware connection
  • Option Bytes regression (optional)
  • Secure Firmware Install
Info white.png Information
The Option Bytes regression step configures the OB to their default state ( this operation may not be needed if the CM will run the SFI process on a virgin part).


5.1. Hardware connection

Plug a micro USB cable to CN1 and make sure that JP2 is in the STLINK position.

5.2. Option bytes regression

The following steps will configure the device to regress the option bytes configuration to a default state: 

STM32_Programmer_CLI.exe -c port=SWD mode=HOTPLUG -ob RDP=0xAA TZEN=1 nSWBOOT0=1 nBOOT0=1 SECBOOTADD0=0x180000 SECWM1_PSTRT=0x0 SECWM1_PEND=0x7F SECWM2_PSTRT=0x1 SECWM2_PEND=0x0 DBANK=0x01 -e all -ob displ

After this step the device is ready for the SFI process.

5.3. Firmware install

This command will start the SFI process and proceed with the installation. 

STM32_Programmer_CLI.exe -vb 1 -log U585_LedBlink.log -c port=SWD mode=HOTPLUG -sfi protocol=static U585_LedBlink.sfi hsm=1 slot=1 -rsse C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin\RSSe\U5\enc_signed_RSSe_sfi.bin
Info white.png Information
You can refer to AN5054 for details on hsm and slot parameters.
SFI cmd installation U585

After the installation of the multiple chunks of the code, the SFI process completes successfully

SFI cmd installationU585 - 2.png

After this step the device is programmed with the OEM application code.

Info white.png Information
You can check the log of the process saved in the file U585_LedBlink.log.


6. References

  1. ↑ B-U585I-IOT02A
  2. ↑ STM32-HSM
  3. ↑ 4.0 4.1 STM32CubeProgrammer
  4. ↑ 5.0 5.1 STM32CubeU5
  5. ↑ STM32CubeIDE
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