5 years, 8 months ago.

NRF52840 mbedtls + Cryptocell310

Hi, I am currently porting my application from an NRF52832 to NRF52840. my Problem is that the programm is crashing (looping) when I try to initialize my ctr_drbg module.

the function 'mbedtls_ctr_drbg_seed' never returns.

I traced the problem down to

'ctx->f_entropy( ctx->p_entropy, seed,ctx->entropy_len )' ++ 'mbedtls_hardware_poll' ++ 'trng_get_bytes' ++

then the code jumps into LLF_RND_StartTrngHw.dbgasm and loops between

'0x00059322: c3 f8 c4 e1 str.w lr, [r3, #452] ; 0x1c4' and '0x00059338: f3 d1 bne.n 0x59322 <LLF_RND_StartTrngHW+106>'

my guess is, that it has something todo with the Cryptocell310 hardware acceleration, because the NRF52832 did not support this feature and the 840 does. However, I am clueless in regards of what is failing.

I tried building a small application to showcase the problem, but somehow a new application wont compile because: 'fatal error: objects_cryptocell.h: No such file or directory'

I dont know why my main programm seems to find this header and my new one doesnt.

EDIT: I was able to make a minimal showcase program. I had to add -DPIO_FRAMEWORK_MBED_RTOS_PRESENT to the platformio.ini, then I could compile.

#include <mbed.h>
#include "RTT/SEGGER_RTT.h"
#include "mbedtls/entropy.h"
#include "mbedtls/error.h"
#include "mbedtls/pk.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"


mbedtls_entropy_context *entropy = NULL;
mbedtls_ctr_drbg_context *ctr_drbg = NULL;

int main() {
SEGGER_RTT_Init();
entropy = new mbedtls_entropy_context();
ctr_drbg = new mbedtls_ctr_drbg_context();
mbedtls_entropy_init(entropy);
mbedtls_ctr_drbg_init(ctr_drbg);
const unsigned char personalization[] = "test123";

SEGGER_RTT_WriteString(0,"STARTED\n");

///
SEGGER_RTT_WriteString(0,"test1\n");
mbedtls_ctr_drbg_seed(ctr_drbg, mbedtls_entropy_func, entropy, personalization, strlen((char *)personalization));
SEGGER_RTT_WriteString(0,"test2");
///

return 0;
}

programm is running on an NRF52840-DK

thanks, Jonas