Hardware-based downgrade protection in nRF5340

[a.da]

Hello.

This ticket was derived from another ticket.

I have a few questions about hardware-based downgrade protection.

• About the Downgrade Protection of the Network Core
  Even with Downgrade Protection enabled, the Network Core is still downgradeable.
  However, version mismatches between the App Core and the Network Core should be avoided.
  If you have any ideas on how to resolve this, please let me know.
• About the monotonic counter
  Is there a way to retrieve the current value?
  I am assuming it will be displayed on a PC serial terminal or a smartphone app.
• About Image Swap
  It seems that when the update count reaches the value of SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_SLOTS, the Image Swap of the App Core is performed every time the software is rebooted.
  Is this the expected behavior?

The logs during the update and reboot are as follows:

monotonic counter < SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_SLOTS

Update

[00:00:18.749,969] <err> mcumgr_img_grp: Failed to open flash area ID 1: -2
[00:00:19.052,307] <inf> mcuboot_util: Image index: 0, Swap type: none
[00:00:41.610,382] <inf> mcuboot_util: Image index: 1, Swap type: none
*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: perm
I: Image index: 1, Swap type: perm
I: Image 0 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 0 copying the secondary slot to the primary slot: 0x44784 bytes
D: writing magic; fa_id=4 off=0xebff0 (0xf7ff0)
D: erasing secondary header
D: erasing secondary trailer
I: Image 1 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 1 copying the secondary slot to the primary slot: 0x2a3c0 bytes
D: writing magic; fa_id=1 off=0x3fff0 (0x3fff0)
D: erasing secondary header
D: erasing secondary trailer
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

Reboot

*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: none
I: Image index: 1, Swap type: none
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

monotonic counter = SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_SLOTS

Update

[00:00:30.237,457] <err> mcumgr_img_grp: Failed to open flash area ID 1: -2
[00:00:30.538,299] <inf> mcuboot_util: Image index: 0, Swap type: none
[00:00:53.067,932] <inf> mcuboot_util: Image index: 1, Swap type: none
*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: perm
I: Image index: 1, Swap type: perm
I: Image 0 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 0 copying the secondary slot to the primary slot: 0x44784 bytes
D: writing magic; fa_id=4 off=0xebff0 (0xf7ff0)
E: Security counter update failed after image upgrade.
I: Image 1 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 1 copying the secondary slot to the primary slot: 0x2a3c0 bytes
D: writing magic; fa_id=1 off=0x3fff0 (0x3fff0)
D: erasing secondary header
D: erasing secondary trailer
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

Reboot

*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: perm
I: Image index: 1, Swap type: none
I: Image 0 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 0 copying the secondary slot to the primary slot: 0x44784 bytes
D: writing magic; fa_id=4 off=0xebff0 (0xf7ff0)
E: Security counter update failed after image upgrade.
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

Thanks for reading.

a.da

[a.da]

Hi Andreas,

AHaug said:

Does this still resonate with your understanding?

Sorry, I’m a bit confused. Meaning, which two numbers should I make the same?

This is configurations and result I tried.
I made the values of SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_VALUE and CONFIG_FW_INFO_FIRMWARE_VERSION the same.
After upgrading to '2' via the nRF Device Manager App, I tried to downgrade to '1'.
Net Core's Downgrade Protection has failed.

Result:

[00:00:37.332,916] <inf> mcuboot_util: Image index: 0, Swap type: none
[00:00:59.952,514] <inf> mcuboot_util: Image index: 1, Swap type: none
*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: perm
E: Image in the secondary slot is not valid!
I: Image index: 1, Swap type: perm
I: Image 1 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 1 copying the secondary slot to the primary slot: 0x2a3c0 bytes
D: writing magic; fa_id=1 off=0x3fff0 (0x3fff0)
D: erasing secondary header
D: erasing secondary trailer
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

./sysbuild.conf

# STEP 2.1 Enable MCUboot
SB_CONFIG_BOOTLOADER_MCUBOOT=y

# STEP 6.3 - Configure project to use external flash for DFU
SB_CONFIG_PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY=y

 # STEP 7.2 - Add b0n image
SB_CONFIG_SECURE_BOOT_NETCORE=y

# STEP 7.3 - Set up multiple partitions
SB_CONFIG_MCUBOOT_UPDATEABLE_IMAGES=2

# STEP 7.4 - Add support to netcore for DFU
SB_CONFIG_NETCORE_APP_UPDATE=y

# STEP 7.5 - Add support to mcuboot for updating
# two cores simultaneously
SB_CONFIG_MCUBOOT_NRF53_MULTI_IMAGE_UPDATE=y

# STEP 7.6 - Simultaneous FOTA does not support rollback
SB_CONFIG_MCUBOOT_MODE_OVERWRITE_ONLY=y

# Enable Hardware-based downgrade protection using MCUboot
SB_CONFIG_MCUBOOT_HARDWARE_DOWNGRADE_PREVENTION=y
SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_SLOTS=4
SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_VALUE=2

./prj.conf

CONFIG_NCS_SAMPLES_DEFAULTS=y

# Deferred logging helps improve LPN power consumption
# when friendship is established.
CONFIG_LOG_MODE_DEFERRED=y

# General configuration
CONFIG_NCS_APPLICATION_BOOT_BANNER_STRING="Mesh Light Fixture"
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
CONFIG_FLASH=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_NVS_LOOKUP_CACHE=y
CONFIG_SETTINGS=y
CONFIG_SETTINGS_NVS_NAME_CACHE=y
CONFIG_HWINFO=y
CONFIG_DK_LIBRARY=y
CONFIG_PWM=y
CONFIG_PM_SINGLE_IMAGE=y
CONFIG_PM_PARTITION_SIZE_SETTINGS_STORAGE=0x8000
CONFIG_SOC_FLASH_NRF_PARTIAL_ERASE=y

# Bluetooth configuration
CONFIG_BT=y
CONFIG_BT_DEVICE_NAME="Mesh Light Fixture"
CONFIG_BT_L2CAP_TX_BUF_COUNT=8
CONFIG_BT_OBSERVER=y
CONFIG_BT_PERIPHERAL=y

# Disable unused Bluetooth features
CONFIG_BT_CTLR_LE_ENC=n
CONFIG_BT_PHY_UPDATE=n
CONFIG_BT_CTLR_CHAN_SEL_2=n
CONFIG_BT_CTLR_MIN_USED_CHAN=n
CONFIG_BT_CTLR_PRIVACY=n

# Bluetooth Mesh configuration
CONFIG_BT_MESH=y
CONFIG_BT_MESH_RELAY=y
CONFIG_BT_MESH_FRIEND=y
CONFIG_BT_MESH_TX_SEG_MAX=10
CONFIG_BT_MESH_PB_GATT=y
CONFIG_BT_MESH_PROXY_USE_DEVICE_NAME=y
CONFIG_BT_MESH_GATT_PROXY=y
CONFIG_BT_MESH_ADV_EXT_GATT_SEPARATE=y
CONFIG_BT_MESH_DK_PROV=y
CONFIG_BT_MESH_NLC_PERF_CONF=y
CONFIG_BT_MESH_NLC_PERF_LIGHTNESS_CTRL=y
CONFIG_BT_MESH_MODEL_EXTENSIONS=y
CONFIG_BT_MESH_MODEL_EXTENSION_LIST_SIZE=18
# Enabling BT_MESH_NLC_PERF_CONF enables support for 3 application keys by
# default. Therefore, allow up to 3 application key bindings per model instance.
CONFIG_BT_MESH_MODEL_KEY_COUNT=3

# Bluetooth Mesh models
CONFIG_BT_MESH_LIGHT_CTRL_SRV=y
CONFIG_BT_MESH_LIGHT_CTRL_SRV_TIME_ON=3
CONFIG_BT_MESH_LIGHT_CTRL_SRV_TIME_PROLONG=3
CONFIG_BT_MESH_LIGHT_CTRL_SRV_RESUME_DELAY=30
CONFIG_BT_MESH_SCENE_SRV=y
CONFIG_BT_MESH_SENSOR_SRV=y

# STEP 2.2 - Enable FOTA over Bluetooth LE
CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU=y

# Enable updates for the network core
CONFIG_NRF53_UPGRADE_NETWORK_CORE=y

./sysbuild/mcuboot.conf

# STEP 6.2 - MCUboot should use external flash
CONFIG_NORDIC_QSPI_NOR=y
CONFIG_BOOT_MAX_IMG_SECTORS=256

# Enable PCD command to read network core application version
CONFIG_FW_INFO=y
CONFIG_PCD_READ_NETCORE_APP_VERSION=y

# Enable Debug Log
CONFIG_MCUBOOT_LOG_LEVEL_DBG=y

./sysbuild/b0n.conf

# Enable PCD command to read network core application version
CONFIG_PCD_READ_NETCORE_APP_VERSION=y

./sysbuild/ipc_radio/prj.conf

CONFIG_HEAP_MEM_POOL_SIZE=8192
CONFIG_MAIN_STACK_SIZE=2048
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

CONFIG_MBOX=y
CONFIG_IPC_SERVICE=y

CONFIG_BT=y
CONFIG_BT_HCI_RAW=y
CONFIG_BT_MAX_CONN=16

# Copy controller configuration from prj.conf
CONFIG_BT_CTLR_LE_ENC=n
CONFIG_BT_CTLR_CHAN_SEL_2=n
CONFIG_BT_CTLR_MIN_USED_CHAN=n
CONFIG_BT_CTLR_PRIVACY=n

# Enables the extended advertising API support and the necessary amount of advertising sets
# in the Bluetooth controller on the network core required by the Bluetooth Mesh.
CONFIG_BT_EXT_ADV=y
CONFIG_BT_EXT_ADV_MAX_ADV_SET=5

CONFIG_IPC_RADIO_BT=y
CONFIG_IPC_RADIO_BT_HCI_IPC=y

# Step 9.2 - Enable logs in netcore so we can verify the update
CONFIG_SERIAL=y
CONFIG_UART_CONSOLE=y
CONFIG_LOG=y

# Enable version number of the firmware
CONFIG_FW_INFO_FIRMWARE_VERSION=2

# Enable logs in netcore
CONFIG_IPC_RADIO_LOG_LEVEL_WRN=y

Kind regards,

a.da

[AHaug]

Hi a.da,

You also need to enable multi-image-update, i.e https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/device_guides/nrf53/simultaneous_multi_image_dfu_nrf5340.html, so that https://github.com/nrfconnect/sdk-mcuboot/blob/148712e7b4618aadbedd04e8d3ce5c3847d3be4f/boot/bootutil/src/loader.c#L1063 can recognize that it should compare the netcore image as well.

If you still see that it doesn't work when enabling this, then there might be a bug in the implementation. Let me know and I'll file a report if that's the case

Kind regards,
Andreas

[a.da]

Hi Andreas,

AHaug said:

You also need to enable multi-image-update

The following files seem to indicate that multi-image-update is enabled. Is that correct?

./build/mcuboot/zephyr/include/generated/zephyr/autoconf.h

Excerpt:

#define CONFIG_BOOT_UPGRADE_ONLY 1
#define CONFIG_BOOT_ENCRYPTION_SUPPORT 1
#define CONFIG_BOOT_MAX_IMG_SECTORS 256
#define CONFIG_BOOT_SHARE_BACKEND_DISABLED 1
#define CONFIG_BOOT_FIH_PROFILE_OFF 1
#define CONFIG_BOOT_USB_DFU_NO 1
#define CONFIG_MCUBOOT_LOG_LEVEL_DBG 1
#define CONFIG_MCUBOOT_LOG_LEVEL 4
#define CONFIG_MCUBOOT_LOG_THREAD_STACK_SIZE 768
#define CONFIG_UPDATEABLE_IMAGE_NUMBER 2
..
#define CONFIG_PCD_APP 1

Full:

3107.autoconf.h

./partitions.yml

Full:

app:
  address: 0xc200
  end_address: 0xf8000
  region: flash_primary
  size: 0xebe00
external_flash:
  address: 0x12c000
  end_address: 0x800000
  region: external_flash
  size: 0x6d4000
mcuboot:
  address: 0x0
  end_address: 0xc000
  placement:
    align:
      end: 0x1000
    before:
    - mcuboot_primary
  region: flash_primary
  size: 0xc000
mcuboot_pad:
  address: 0xc000
  end_address: 0xc200
  placement:
    align:
      start: 0x4000
    before:
    - mcuboot_primary_app
  region: flash_primary
  size: 0x200
mcuboot_primary:
  address: 0xc000
  end_address: 0xf8000
  orig_span: &id001
  - mcuboot_pad
  - app
  region: flash_primary
  size: 0xec000
  span: *id001
mcuboot_primary_1:
  address: 0x0
  device: nordic_ram_flash_controller
  end_address: 0x40000
  region: ram_flash
  size: 0x40000
mcuboot_primary_app:
  address: 0xc200
  end_address: 0xf8000
  orig_span: &id002
  - app
  region: flash_primary
  size: 0xebe00
  span: *id002
mcuboot_secondary:
  address: 0x0
  device: DT_CHOSEN(nordic_pm_ext_flash)
  end_address: 0xec000
  placement:
    align:
      start: 0x4
  region: external_flash
  share_size:
  - mcuboot_primary
  size: 0xec000
mcuboot_secondary_1:
  address: 0xec000
  device: DT_CHOSEN(nordic_pm_ext_flash)
  end_address: 0x12c000
  region: external_flash
  size: 0x40000
otp:
  address: 0xff8380
  end_address: 0xff83fc
  region: otp
  size: 0x7c
pcd_sram:
  address: 0x20000000
  end_address: 0x20002000
  placement:
    after:
    - start
  region: sram_primary
  size: 0x2000
provision:
  address: 0xff8100
  end_address: 0xff8380
  region: otp
  size: 0x280
ram_flash:
  address: 0x40000
  end_address: 0x40000
  region: ram_flash
  size: 0x0
rpmsg_nrf53_sram:
  address: 0x20070000
  end_address: 0x20080000
  placement:
    before:
    - end
  region: sram_primary
  size: 0x10000
settings_storage:
  address: 0xf8000
  end_address: 0x100000
  placement:
    align:
      start: 0x4000
    before:
    - end
  region: flash_primary
  size: 0x8000
sram_primary:
  address: 0x20002000
  end_address: 0x20070000
  region: sram_primary
  size: 0x6e000

Is there anything else that needs to be confirmed?

Kind regards,

a.da

[AHaug]

Hi,

This looks to be correct according to the multi_image dfu guide, and is what I would've expected to see in my generated .config atleast. Are you able to compile it and perform a DFU with hw protection?

Kind regards,
Andreas

[a.da]

Hi Andreas,

AHaug said:

Are you able to compile it and perform a DFU with hw protection?

It seems that hw protection was enabled for the App Core, but not for the Net Core.

The result is the same as the one I posted earlier.

a.da said:

After upgrading to '2' via the nRF Device Manager App, I tried to downgrade to '1'.
Net Core's Downgrade Protection has failed.

Result:

[00:00:37.332,916] <inf> mcuboot_util: Image index: 0, Swap type: none
[00:00:59.952,514] <inf> mcuboot_util: Image index: 1, Swap type: none
*** Booting MCUboot v2.1.0-dev-12e5ee106034 ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***
I: Starting bootloader
I: Image index: 0, Swap type: perm
E: Image in the secondary slot is not valid!
I: Image index: 1, Swap type: perm
I: Image 1 upgrade secondary slot -> primary slot
I: Erasing the primary slot
I: Image 1 copying the secondary slot to the primary slot: 0x2a3c0 bytes
D: writing magic; fa_id=1 off=0x3fff0 (0x3fff0)
D: erasing secondary header
D: erasing secondary trailer
I: Bootloader chainload address offset: 0xc000
*** Booting Mesh Light Fixture v2.9.0-d54b9798c66e ***
*** Using nRF Connect SDK v2.9.0-7787b2649840 ***
*** Using Zephyr OS v3.7.99-1f8f3dc29142 ***

Kind regards,

a.da