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M467: Seed PRNG with TRNG for SCAP 

According to TRM, it is suggested PRNG be seeded by TRNG on every Crypto H/W reset.
pull/15337/head
Chun-Chieh Li 2022-04-28 15:31:49 +08:00
parent d92d75e9ac
commit 21970e30f1
1 changed files with 27 additions and 1 deletions
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28
targets/TARGET_NUVOTON/TARGET_M460/crypto/crypto-misc.cpp
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@ -28,6 +28,7 @@
#include "crypto-misc.h"
#include "platform/SingletonPtr.h"
#include "platform/PlatformMutex.h"
#include "hal/trng_api.h"
/* Consideration for choosing proper synchronization mechanism
*
@ -93,8 +94,33 @@ void crypto_init(void)
CLK_EnableModuleClock(CRPT_MODULE);
SYS_ResetModule(CRPT_RST);
SYS_LockReg(); // Lock protected register
NVIC_EnableIRQ(CRPT_IRQn);
/* Seed PRNG with TRNG to enable SCAP
*
* According to TRM, it is suggested PRNG be seeded by TRNG on
* every Crypto H/W reset.
*
* To serialize access to TRNG, we invoke Mbed OS TRNG HAL API whose
* implementations are thread-safe, instead of BSP RNG driver.
*/
trng_t trng_ctx;
trng_init(&trng_ctx);
/* Wait for PRNG free */
while (CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk);
/* Reload seed from TRNG for the first time */
CRPT->PRNG_CTL = (PRNG_KEY_SIZE_256 << CRPT_PRNG_CTL_KEYSZ_Pos) | CRPT_PRNG_CTL_START_Msk | CRPT_PRNG_CTL_SEEDRLD_Msk | PRNG_CTL_SEEDSRC_TRNG;
/* Wait for PRNG done */
while (CRPT->PRNG_CTL & CRPT_PRNG_CTL_BUSY_Msk);
/* No reload seed for following times */
CRPT->PRNG_CTL = 0;
trng_free(&trng_ctx);
}
core_util_critical_section_exit();
}