yuzu/mbedtls
1
0
Fork 0
mirror of https://github.com/yuzu-emu/mbedtls.git synced 2025-02-02 07:41:03 +00:00
Code Issues Packages Projects Releases Wiki Activity

Update AES SCA random number function

Browse source 
-Replace usage of rand() with mbedtls_platform_random_in_range()
-Prevent for-ever loop by hardcoding SCA countermeasure position in
 case of used random function is always returning constant number.
This commit is contained in:
Arto Kinnunen 2019-12-05 10:10:31 +02:00
parent f44f7d465a
commit 76deef9fca
1 changed files with 13 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
library/aes.c
View file

@ -544,24 +544,31 @@ static void aes_sca_cm_data_randomize( uint8_t *tbl, uint8_t tbl_len )
// Randomize SCA CM positions to tbl
for( i = 0; i < AES_SCA_CM_ROUNDS; i++ )
{
is_unique_number = 0;
do
{
is_unique_number = 1;
/* TODO - Use proper random. This is now ONLY FOR TESTING as mbedtls_platform_random_in_range is alwyays returning 0 */
num = /* mbedtls_platform_random_in_range( tbl_len - 4 ) */rand() % (tbl_len - 4);
is_unique_number++;
num = mbedtls_platform_random_in_range( tbl_len - 4 );
if( is_unique_number > 10 )
{
// prevent forever loop if random returns constant
is_unique_number = 0;
tbl[i] = 0x10; // fake data
}
if( tbl[num] == 0 )
{
is_unique_number = 0;
tbl[num] = 0x10;
tbl[num] = 0x10; // fake data
}
} while( is_unique_number == 1 );
} while( is_unique_number != 0 );
}
// randomize control data for start and final round
for( i = 1; i <= 2; i++ )
{
num = /* mbedtls_platform_random_in_range( 0xff ) */rand() % 0xff;
num = mbedtls_platform_random_in_range( 0xff );
if( ( num % 2 ) == 0 )
{
tbl[tbl_len - ( i * 2 - 0 )] = 0x10; // fake data