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Update HMAC and MD FI countermeasures

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-Return error value by default.
-Success is returned only after checking internal states.
-Append flow_control to cover also last function call.
This commit is contained in:
Arto Kinnunen 2019-11-25 16:19:25 +02:00
parent 5b36693774
commit 5299a42f25
2 changed files with 46 additions and 43 deletions
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71
library/hmac_drbg.c
View file

@ -123,30 +123,30 @@ int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx,
flow_counter++; flow_counter++;
if( ( ret = mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ) ) != 0 ) if( ( ret = mbedtls_md_hmac_finish( &ctx->md_ctx, ctx->V ) ) != 0 )
goto exit; goto exit;
flow_counter++;
} }
exit: exit:
if( ret == 0 ) mbedtls_platform_zeroize( K, sizeof( K ) );
/* Check for possible attack.
* Counters needs to have correct values when returning success
*/
if ( ret != 0 )
return( ret ); // error case, return immediately
if ( ( ( flow_counter == 8 ) && ( sep[0] == 1 ) ) ||
( ( flow_counter == 18 ) && ( sep[0] == 2 ) ) )
{ {
ret = MBEDTLS_ERR_PLATFORM_FAULT_DETECTED; flow_counter = flow_counter - sep[0];
/* Check for possible attack. // Double check flow_counter
* Counters needs to have correct values when returning success if ( ( flow_counter == 7 ) || ( flow_counter == 16 ) )
*/
if ( ( ( flow_counter == 7 ) && ( sep[0] == 1 ) ) ||
( ( flow_counter == 16 ) && ( sep[0] == 2 ) ) )
{ {
flow_counter = flow_counter - sep[0]; return ret; // success, return 0 from ret
// Double check flow_counter
if ( ( flow_counter == 6 ) || ( flow_counter == 14 ) )
{
ret = 0;
}
} }
} }
mbedtls_platform_zeroize( K, sizeof( K ) ); return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
return( ret );
} }
#if !defined(MBEDTLS_DEPRECATED_REMOVED) #if !defined(MBEDTLS_DEPRECATED_REMOVED)
@ -259,14 +259,20 @@ static int hmac_drbg_reseed_core( mbedtls_hmac_drbg_context *ctx,
ctx->reseed_counter = 1; ctx->reseed_counter = 1;
exit: exit:
if (ret == 0 && ctx->reseed_counter != 1)
{
/* Illegal condition, possible attack detected */
ret = MBEDTLS_ERR_PLATFORM_FAULT_DETECTED;
}
/* 4. Done */ /* 4. Done */
mbedtls_platform_zeroize( seed, seedlen ); mbedtls_platform_zeroize( seed, seedlen );
return( ret );
if ( ret != 0 )
return ret;
if ( ret == 0 && ctx->reseed_counter == 1 )
{
/* All ok, return 0 from ret */
return ret;
}
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
} }
/* /*
@ -430,21 +436,20 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng,
exit: exit:
/* 8. Done */ /* 8. Done */
if (ret == 0) if ( ret != 0 )
return ret;
/*
* Check doubled variables and illegal conditions in case of possible
* attack.
*/
if ( ( out_len_fi == out_len ) && ( output_fi == output) &&
( left == 0 ) )
{ {
/* return ret; // Success, return 0
* Check doubled variables and illegal conditions in case of possible
* attack.
*/
ret = MBEDTLS_ERR_PLATFORM_FAULT_DETECTED;
if ( ( out_len_fi == out_len ) && ( output_fi == output) &&
( left == 0 ) )
{
ret = 0;
}
} }
return( ret ); return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
} }
/* /*

18
library/md.c
View file

@ -525,7 +525,7 @@ int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key,
int ret; int ret;
unsigned char sum[MBEDTLS_MD_MAX_SIZE]; unsigned char sum[MBEDTLS_MD_MAX_SIZE];
unsigned char *ipad, *opad; unsigned char *ipad, *opad;
size_t i; size_t i = 0;
mbedtls_md_handle_t md_info; mbedtls_md_handle_t md_info;
@ -588,16 +588,14 @@ int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key,
cleanup: cleanup:
mbedtls_platform_zeroize( sum, sizeof( sum ) ); mbedtls_platform_zeroize( sum, sizeof( sum ) );
if ( ret == 0 ) if ( ret != 0 )
{ return ret;
ret = MBEDTLS_ERR_PLATFORM_FAULT_DETECTED;
/* Check possible fault injection */
if ( ( i - 2 ) == keylen ) {
ret = 0;
}
}
return( ret ); /* Check possible fault injection */
if ( ( i - 2 ) == keylen )
return ret; // success, return 0 from ret
return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED );
} }
int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx, int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx,