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Merge pull request #3336 from piotr-now/baremetal_flowmon

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Increasing resistance to fault injection attacks related with memory operations.
This commit is contained in:
Piotr Nowicki 2020-06-01 08:09:26 +02:00 committed by GitHub
parent fc7c69df25 f0ab6d62ac
commit e071e42480
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 27 additions and 9 deletions
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12
library/platform_util.c
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@ -111,6 +111,9 @@ void *mbedtls_platform_memcpy( void *dst, const void *src, size_t num )
/* Randomize initial data to prevent leakage while copying */
uint32_t data = mbedtls_platform_random_in_range( 256 );
/* Use memset with random value at first to increase security - memset is
not normally part of the memcpy function and here can be useed
with regular, unsecured implementation */
memset( (void *) dst, data, num );
memcpy( (void *) ( (unsigned char *) dst + start_offset ),
(void *) ( (unsigned char *) src + start_offset ),
@ -124,23 +127,26 @@ int mbedtls_platform_memcmp( const void *buf1, const void *buf2, size_t num )
volatile const unsigned char *B = (volatile const unsigned char *) buf2;
volatile unsigned char diff = 0;
size_t i = num;
/* Start from a random location and check the correct number of iterations */
size_t i, flow_counter = 0;
size_t start_offset = (size_t) mbedtls_platform_random_in_range( num );
for( i = start_offset; i < num; i++ )
{
unsigned char x = A[i], y = B[i];
flow_counter++;
diff |= x ^ y;
}
for( i = 0; i < start_offset; i++ )
{
unsigned char x = A[i], y = B[i];
flow_counter++;
diff |= x ^ y;
}
return( diff );
/* Return 0 only when diff is 0 and flow_counter is equal to num */
return( (int) diff | (int) ( flow_counter ^ num ) );
}
uint32_t mbedtls_platform_random_in_range( size_t num )

24
tinycrypt/ecc.c
View file

@ -286,20 +286,32 @@ uECC_word_t uECC_vli_equal(const uECC_word_t *left, const uECC_word_t *right)
{
uECC_word_t diff = 0;
uECC_word_t flow_monitor = 0;
uECC_word_t tmp1, tmp2;
volatile int i;
for (i = NUM_ECC_WORDS - 1; i >= 0; --i) {
/* Start from a random location and check the correct number of iterations */
int start_offset = mbedtls_platform_random_in_range(NUM_ECC_WORDS);
for (i = start_offset; i < NUM_ECC_WORDS; ++i) {
tmp1 = left[i];
tmp2 = right[i];
flow_monitor++;
diff |= (tmp1 ^ tmp2);
}
/* i should be -1 now */
mbedtls_platform_random_delay();
diff |= i ^ -1;
for (i = 0; i < start_offset; ++i) {
tmp1 = left[i];
tmp2 = right[i];
flow_monitor++;
diff |= (tmp1 ^ tmp2);
}
return diff;
/* Random delay to increase security */
mbedtls_platform_random_delay();
/* Return 0 only when diff is 0 and flow_counter is equal to NUM_ECC_WORDS */
return (diff | (flow_monitor ^ NUM_ECC_WORDS));
}
uECC_word_t cond_set(uECC_word_t p_true, uECC_word_t p_false, unsigned int cond)
@ -848,7 +860,7 @@ void vli_mmod_fast_secp256r1(unsigned int *result, unsigned int*product)
}
while (carry < 0);
} else {
while (carry ||
while (carry ||
uECC_vli_cmp_unsafe(curve_p, result) != 1) {
carry -= uECC_vli_sub(result, result, curve_p);
}