Secure DFU on Thing52

[Jared]

Hey all,

I'm trying to roll our "own version" of the bootloader for the Thing52. I have followed the instructions to create the PEM file and the public key. I'm able to compile both the application code and the bootloader code. I've been merging the files with the following lines in my Makefile.

settings: nrf52832_xxaa_s132
@echo Generating settings...
nrfutil settings generate --family NRF52 --application $(OUTPUT_BINARY_DIRECTORY)/$<.hex --application-version 0 --bootloader-version 0 --bl-settings-version 1 settings.hex
mergehex -m settings.hex ../../bootloader_secure/pca20020/armgcc/_build/$<.hex -o bootloader.hex

image: nrf52832_xxaa_s132 settings
@echo Creating combo Bootloader + App + Softdevice package
mergehex -m ../../../sdk_components/softdevice/s132/hex/s132_nrf52_4.0.2_softdevice.hex bootloader.hex -o softdevice.hex
mergehex -m softdevice.hex nrf52832_xxaa_s132.hex -o ts.hex

Once the unified hex file is created and programmed I can connect to the newly programmed Thingy. I create a DFU package with the following:

package: nrf52832_xxaa_s132
@echo Creating DFU package:
nrfutil pkg generate --application $(OUTPUT_BINARY_DIRECTORY)/$<.bin --application-version 0 --hw-version 52 --sd-req 0x98 --key-file ../../bootloader_secure/private-key.pem dfu-app.zip

I then have tried uploading to my phone and using NRF connect on my computer to initiate a DFU. According to the logs I get this far and it never returns:

:INFO:Received indication state 1, notification state 0

m_ble         :INFO:Indication for BLE_DFU is enabled

:INFO:on_ctrlpt_write: execute enter

:DEBUG:on_ctrlpt_write: execuing!!

m_ble         :INFO:Device is entering bootloader mode!

Is there anything glaring that I'm missing here?

Thanks!

[Vidar Berg]

Hi,

The new application FW needs to have a higher version number. Otherwise the bootloader will reject the update. Please try to set --application-version to '1' and see if you get the same result. 

dfu_req_handling.c

static nrf_dfu_res_code_t dfu_handle_prevalidate(dfu_signed_command_t const * p_command, pb_istream_t * p_stream, uint8_t * p_init_cmd, uint32_t init_cmd_len)
{ 
   ...
   switch (p_init->type)
    {
        case DFU_FW_TYPE_APPLICATION:
            if (p_init->fw_version < fw_version)
            {
                NRF_LOG_ERROR("FW version too low\r\n");
                return ext_error_set(NRF_DFU_EXT_ERROR_FW_VERSION_FAILURE);
            }
        break;
        ...

[Jared]

I did give that a try as well. No dice. I ended up leaning towards just converting the existing code to SDK14 as the bootloader/DFU setup is in a better state there.

[Vidar Berg]

Ok, thanks for the update. It looks like you did everything correctly apart from the wrong version number. Since you are already migrating to SDK 14, recommend to use v14.1.0 as it includes a fix for a bug the prevented DFU of larger softdevices, see this thread for more details. 

[Jared]

Important to know. Thanks Vidar Berg