Writing .obk file into OBK flash area using C source code

CSmallwood · ‎2025-11-21

I have a password obk file:
$ xxd PasswordObkFile.obk
00000000: 0001 fd0f 6000 0000 0000 0000 5e9b d65f ....`.......^.._
00000010: e48e a17e 40ae 126f 76e7 c101 3a73 bf35 ...~@..ov...:s.5
00000020: c95d 4897 5c5d 1575 a719 8442 184a a46d .]H.\].u...B.J.m
00000030: 8134 1172 7da0 dc9e 6418 6bb9 9072 89b5 .4.r}...d.k..r..
00000040: aab4 b320 d26f ff5e a45d 8e3d 7750 0000 ... .o.^.].=wP..
00000050: 0000 0000 0000 0000 0000 0000 0000 0000 ................
00000060: 0000 0000 0000 0000 0000 0000 ............

I am running my application with Trustzone disabled (TZEN=C3).

I have a C array:

static uint32_t obk_data[] = {
    0x60000000, 0x00000000, 0x5e9bd65f, 0xe48ea17e,
    0x40ae126f, 0x76e7c101, 0x3a73bf35, 0xc95d4897,
    0x5c5d1575, 0xa7198442, 0x184aa46d, 0x81341172,
    0x7da0dc9e, 0x64186bb9, 0x907289b5, 0xaab4b320,
    0xd26fff5e, 0xa45d8e3d, 0x77500000, 0x00000000,
    0x00000000, 0x00000000, 0x00000000, 0x00000000
};

Using a function like this I am writing the contents to the OBK area using functions like this (it happens within a loop to get all the obk_data into the FLASH starting at the HDPL1 base address).

HAL_FLASH_Program(FLASH_TYPEPROGRAM_QUADWORD_OBK_ALT, FLASH_OBK_HDPL1_BASE_NS, Data); // FLASH_OBK_HDPL1_BASE_NS is 0x0BFD0000UL.
HAL_FLASHEx_OBK_Swap(FLASH_OBK_SWAP_OFFSET_HDPL1);

I am then transition the product lifecycle state to PROVISIONING in the code but my debug authentication fails. I always have to use the STM32_Programmer_CLI tool to download the .obk file manually before I am able to successfully perform a regression.

What am I doing wrong?

I have tried:

Little and big endian byte ordering for the obk_data variable
Using a wireshark to look at the bytes that the STM32_Programmer_CLI tool sends across, they seem to be the same bytes but I can't know exactly where the ST-Link firmware is placing them.