eden-emu/mbedtls
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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.
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Piotr Nowicki 2020-06-01 08:09:26 +02:00 • committed by GitHub
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 )