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Merge pull request #3880 from AndrzejKurek/fi-random-delays

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Add random delays to sha256 to protect against fault injection
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Andrzej Kurek 2020-11-25 13:38:52 -05:00 committed by GitHub
commit 8265f5cc4f
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GPG Key ID: 4AEE18F83AFDEB23
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 ) if( flow_ctrl == 8 )
{ {
return( 0 ); mbedtls_platform_random_delay();
if( flow_ctrl == 8 )
return( 0 );
} }
/* Free the ctx upon suspected FI */ /* Free the ctx upon suspected FI */
mbedtls_sha256_free( ctx ); 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 */ /* Re-check ilen_dup to protect from a FI attack */
if( ilen_dup < 64 ) if( ilen_dup < 64 )
{ {
mbedtls_platform_random_delay();
/* Re-check that the calculated offsets are correct */ /* Re-check that the calculated offsets are correct */
ilen_change = ilen - ilen_dup; ilen_change = ilen - ilen_dup;
if( ( input_dup + ilen_change ) == input ) 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 */ /* flow ctrl was incremented twice and then 7 times in two loops */
if( flow_ctrl == 9 ) 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 */ /* Free the ctx and clear output upon suspected FI */
mbedtls_sha256_free( ctx ); mbedtls_sha256_free( ctx );
@ -509,7 +514,9 @@ exit:
if( input_dup == input && ilen_dup == ilen ) 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 ); mbedtls_platform_memset( output, 0, 32 );
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED ); return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );