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Add random delays to sha256 to protect against fault injection

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Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
This commit is contained in:
Andrzej Kurek 2020-11-13 11:29:14 +01:00
parent 5eba1d82a2
commit 9bc6119bb9
1 changed files with 10 additions and 3 deletions
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13
library/sha256.c
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@ -281,7 +281,9 @@ int mbedtls_internal_sha256_process( mbedtls_sha256_context *ctx,
if( flow_ctrl == 8 )
{
return( 0 );
mbedtls_platform_random_delay();
if( flow_ctrl == 8 )
return( 0 );
}
/* Free the ctx upon suspected FI */
mbedtls_sha256_free( ctx );
@ -355,6 +357,7 @@ int mbedtls_sha256_update_ret( mbedtls_sha256_context *ctx,
/* Re-check ilen_dup to protect from a FI attack */
if( ilen_dup < 64 )
{
mbedtls_platform_random_delay();
/* Re-check that the calculated offsets are correct */
ilen_change = ilen - ilen_dup;
if( ( input_dup + ilen_change ) == input )
@ -458,7 +461,9 @@ int mbedtls_sha256_finish_ret( mbedtls_sha256_context *ctx,
/* flow ctrl was incremented twice and then 7 times in two loops */
if( flow_ctrl == 9 )
{
return( 0 );
mbedtls_platform_random_delay();
if( flow_ctrl == 9 )
return( 0 );
}
/* Free the ctx and clear output upon suspected FI */
mbedtls_sha256_free( ctx );
@ -509,7 +514,9 @@ exit:
if( input_dup == input && ilen_dup == ilen )
{
return( ret );
mbedtls_platform_random_delay();
if( input_dup == input && ilen_dup == ilen )
return( ret );
}
mbedtls_platform_memset( output, 0, 32 );
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );