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Added some descriptions of functions

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Signed-off-by: Piotr Nowicki <piotr.nowicki@arm.com>
This commit is contained in:
Piotr Nowicki 2020-05-25 12:48:30 +02:00
parent 1a9d33e8c8
commit f0ab6d62ac
2 changed files with 7 additions and 2 deletions
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7
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 */ /* Randomize initial data to prevent leakage while copying */
uint32_t data = mbedtls_platform_random_in_range( 256 ); 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 ); memset( (void *) dst, data, num );
memcpy( (void *) ( (unsigned char *) dst + start_offset ), memcpy( (void *) ( (unsigned char *) dst + start_offset ),
(void *) ( (unsigned char *) src + start_offset ), (void *) ( (unsigned char *) src + start_offset ),
@ -124,8 +127,8 @@ int mbedtls_platform_memcmp( const void *buf1, const void *buf2, size_t num )
volatile const unsigned char *B = (volatile const unsigned char *) buf2; volatile const unsigned char *B = (volatile const unsigned char *) buf2;
volatile unsigned char diff = 0; volatile unsigned char diff = 0;
size_t i = num; /* Start from a random location and check the correct number of iterations */
size_t flow_counter = 0; size_t i, flow_counter = 0;
size_t start_offset = (size_t) mbedtls_platform_random_in_range( num ); size_t start_offset = (size_t) mbedtls_platform_random_in_range( num );
for( i = start_offset; i < num; i++ ) for( i = start_offset; i < num; i++ )

2
tinycrypt/ecc.c
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@ -290,6 +290,7 @@ uECC_word_t uECC_vli_equal(const uECC_word_t *left, const uECC_word_t *right)
uECC_word_t tmp1, tmp2; uECC_word_t tmp1, tmp2;
volatile int i; volatile int i;
/* Start from a random location and check the correct number of iterations */
int start_offset = mbedtls_platform_random_in_range(NUM_ECC_WORDS); int start_offset = mbedtls_platform_random_in_range(NUM_ECC_WORDS);
for (i = start_offset; i < NUM_ECC_WORDS; ++i) { for (i = start_offset; i < NUM_ECC_WORDS; ++i) {
@ -306,6 +307,7 @@ uECC_word_t uECC_vli_equal(const uECC_word_t *left, const uECC_word_t *right)
diff |= (tmp1 ^ tmp2); diff |= (tmp1 ^ tmp2);
} }
/* Random delay to increase security */
mbedtls_platform_random_delay(); mbedtls_platform_random_delay();
/* Return 0 only when diff is 0 and flow_counter is equal to NUM_ECC_WORDS */ /* Return 0 only when diff is 0 and flow_counter is equal to NUM_ECC_WORDS */