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Sleep for a random number of cycles before reading out UDS to FW RAM

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To protect against warm boot attacks.

Signed-off-by: Daniel Lublin <daniel@lublin.se>
This commit is contained in:
Daniel Lublin 2022-12-12 15:58:46 +01:00 committed by Michael Cardell Widerkrantz
parent abdcd3af0e
commit c573155ba1
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GPG Key ID: D3DB3DDF57E704E5
1 changed files with 19 additions and 0 deletions
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19
hw/application_fpga/fw/tk1/main.c
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@ -22,6 +22,12 @@ static volatile uint32_t *app_size = (volatile uint32_t *)TK1_MMIO_TK1_AP
static volatile uint8_t *fw_ram = (volatile uint8_t *)TK1_MMIO_FW_RAM_BASE;
static volatile uint32_t *led = (volatile uint32_t *)TK1_MMIO_TK1_LED;
static volatile uint32_t *fw_blake2s_addr = (volatile uint32_t *)TK1_MMIO_TK1_BLAKE2S;
static volatile uint32_t *trng_status = (volatile uint32_t *)TK1_MMIO_TRNG_STATUS;
static volatile uint32_t *trng_entropy = (volatile uint32_t *)TK1_MMIO_TRNG_ENTROPY;
static volatile uint32_t *timer = (volatile uint32_t *)TK1_MMIO_TIMER_TIMER;
static volatile uint32_t *timer_prescaler = (volatile uint32_t *)TK1_MMIO_TIMER_PRESCALER;
static volatile uint32_t *timer_status = (volatile uint32_t *)TK1_MMIO_TIMER_STATUS;
static volatile uint32_t *timer_ctrl = (volatile uint32_t *)TK1_MMIO_TIMER_CTRL;
#define LED_RED (1 << TK1_MMIO_TK1_LED_R_BIT)
#define LED_GREEN (1 << TK1_MMIO_TK1_LED_G_BIT)
@ -98,6 +104,19 @@ static void compute_cdi(uint8_t digest[32], uint8_t use_uss, uint8_t uss[32])
// To protect UDS we use a special firmware-only RAM for both
// the in parameter to blake2s and the blake2s context.
// Prepare to sleep a random number of cycles before reading out UDS to
// FW RAM
*timer_prescaler = 1;
while ((*trng_status & (1 << TK1_MMIO_TRNG_STATUS_READY_BIT)) == 0) {
}
uint32_t rnd = *trng_entropy;
// Up to 65536 cycles
rnd &= 0xffff;
*timer = (rnd == 0 ? 1 : rnd);
*timer_ctrl = 1;
while ((*timer_status & (1 << TK1_MMIO_TIMER_STATUS_READY_BIT)) == 0) {
}
// Only word aligned access to UDS
wordcpy((void *)fw_ram, (void *)uds, 8);
memcpy((void *)fw_ram + 32, digest, 32);