diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h index 0f651339c..347a8fa81 100644 --- a/include/mbedtls/config.h +++ b/include/mbedtls/config.h @@ -640,10 +640,13 @@ * Add countermeasures against possible side-channel-attack to AES calculation. * * Uncommenting this macro adds additional calculation rounds to AES - * calculation. Additional rounds are using random data and can occur in any - * AES calculation round. + * calculation. Additional rounds are using random data for calculation. The + * additional rounds are added to: + * -initial key addition phase + * -before the first AES calculation round + * -after the last AES calculation round * - * Tradeoff: Uncommenting this increases ROM footprint by ~100 bytes. + * Tradeoff: Uncommenting this macro does not increase codesize. * The performance loss is ~50% with 128 bit AES. * * This option is dependent of \c MBEDTLS_ENTROPY_HARDWARE_ALT. diff --git a/library/aes.c b/library/aes.c index c96f29e31..9098d4795 100644 --- a/library/aes.c +++ b/library/aes.c @@ -94,10 +94,8 @@ typedef struct { } aes_r_data_t; #if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) -/* Number of additional AES calculation rounds added for SCA CM */ -#define AES_SCA_CM_ROUNDS 3 -#else /* MBEDTLS_AES_SCA_COUNTERMEASURES */ -#define AES_SCA_CM_ROUNDS 0 +/* Number of additional AES dummy rounds added for SCA countermeasures */ +#define AES_SCA_CM_ROUNDS 5 #endif /* MBEDTLS_AES_SCA_COUNTERMEASURES */ #if defined(MBEDTLS_PADLOCK_C) && \ @@ -513,99 +511,105 @@ static void aes_gen_tables( void ) #endif /* MBEDTLS_AES_ROM_TABLES */ /** - * Randomize positions when to use AES SCA countermeasures. - * Each byte indicates one AES round as follows: - * first ( tbl_len - 4 ) bytes are reserved for middle AES rounds: - * -4 high bit = table to use 0x10 for SCA CM data, 0 otherwise - * -4 low bits = offset based on order, 4 for even position, 0 otherwise - * Last 4 bytes for first(2) and final(2) round calculation - * -4 high bit = table to use, 0x10 for SCA CM data, otherwise real data - * -4 low bits = not used + * Randomize positions for AES SCA countermeasures if AES countermeasures are + * enabled. If the countermeasures are not enabled then we fill the given table + * with only real AES rounds to be executed. + * + * Dummy rounds are added as follows: + * 1. One dummy round added to the initial round key addition (executed in + * random order). + * 2. Random number of dummy rounds added as first and/or last AES calculation + * round. Total number of dummy rounds is AES_SCA_CM_ROUNDS. + * + * Description of the bytes in the table are as follows: + * - 2 bytes for initial round key addition + * - remaining bytes for AES calculation with real or dummy data + * + * Each byte indicates one AES calculation round: + * -4 high bit = table to use 0x10 for dummy data, 0x00 real data + * -bit 2 = offset for even/odd rounds + * -bit 0-1: stop mark (0x03) to indicate calculation end * * Return Number of additional AES rounds * * Example of the control bytes: - * Control data when only real data (R) is used: - * | R | R | R | R | R | R | R | R | Start | Final | - * |0x04|0x00|0x00|0x04|0x00|0x04|0x00|0x04|0x00|0x00|0x00|0x00| + * R = real data in actual AES calculation round + * Ri = Real data in initial round key addition phase + * F = fake data in actual AES calculation round + * Fi = fake data in initial round key addition phase * - * Control data with 5 (F) dummy rounds and randomized start and final round: - * | R | F | R | F | F | R | R | R | R | R | R | START RF| FINAL FR| - * |0x04|0x10|0x04|0x10|0x10|0x00|0x04|0x00|0x04|0x00|0x04|0x00|0x10|0x10|0x00| + * 1. No countermeasures enabled and AES-128, only real data (R) used: + * | Ri | R | R | R | R | R | R | R | R | R | R | + * |0x03|0x04|0x00|0x04|0x00|0x04|0x00|0x04|0x00|0x07|0x03| + * + * 2. Countermeasures enabled, 3 (F) dummy rounds in start and 1 at end: + * | Fi | Ri | F | F | F | R | R | ... | R | R | R | R | F | + * |0x10|0x03|0x10|0x10|0x10|0x04|0x00| ... |0x04|0x00|0x04|0x03|0x07| */ +#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) static int aes_sca_cm_data_randomize( uint8_t *tbl, uint8_t tbl_len ) { - int i, is_even_pos; -#if AES_SCA_CM_ROUNDS != 0 - int is_unique_number; - int num; -#endif + int i = 0, j, is_even_pos, dummy_rounds, num; mbedtls_platform_memset( tbl, 0, tbl_len ); + // get random from 0x0fff (each f will be used separately) + num = mbedtls_platform_random_in_range( 0x1000 ); -#if AES_SCA_CM_ROUNDS != 0 - // Randomize SCA CM positions to tbl - for( i = 0; i < AES_SCA_CM_ROUNDS; i++ ) + // Randomize execution order of initial round key addition + if ( ( num & 0x0100 ) == 0 ) { - is_unique_number = 0; - do - { - 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; // fake data - } - } while( is_unique_number != 0 ); + tbl[i++] = 0x10; // dummy data + tbl[i++] = 0x00 | 0x03; // real data + stop marker + } else { + tbl[i++] = 0x00; // real data + tbl[i++] = 0x10 | 0x03; // dummy data + stop marker } - // randomize control data for start and final round - for( i = 1; i <= 2; i++ ) - { - num = mbedtls_platform_random_in_range( 0xff ); - if( ( num % 2 ) == 0 ) - { - tbl[tbl_len - ( i * 2 - 0 )] = 0x10; // fake data - tbl[tbl_len - ( i * 2 - 1 )] = 0x00; // real data - } - else - { - tbl[tbl_len - ( i * 2 - 0 )] = 0x00; // real data - tbl[tbl_len - ( i * 2 - 1 )] = 0x10; // fake data - } - } -#endif /* AES_SCA_CM_ROUNDS != 0 */ + // Randomize number of dummy AES rounds + dummy_rounds = AES_SCA_CM_ROUNDS - ( ( num & 0x0010 ) >> 4 ); + tbl_len = tbl_len - (AES_SCA_CM_ROUNDS - dummy_rounds); - // Fill real AES round data to the remaining places + // randomize positions for the dummy rounds + num = ( num & 0x000f ) % ( dummy_rounds + 1 ); + + // add dummy rounds after initial round key addition (if needed) + for ( ; i < num + 2; i++ ) + { + tbl[i] = 0x10; // dummy data + } + + // add dummy rounds to the end, (AES_SCA_CM_ROUNDS - num) rounds if needed + for ( j = tbl_len - dummy_rounds + num; j < tbl_len; j++ ) + { + tbl[j] = 0x10; // dummy data + } + + // Fill real AES data to the remaining places is_even_pos = 1; - for( i = 0; i < tbl_len - 4; i++ ) + for( ; i < tbl_len; i++ ) { if( tbl[i] == 0 ) { if( is_even_pos == 1 ) { - tbl[i] = 0x04; // real data, offset 4 + tbl[i] = 0x04; // real data, offset for rounds 1,3,5, etc... is_even_pos = 0; } else { - tbl[i] = 0x00; // real data, offset 0 + tbl[i] = 0x00; // real data, offset for rounds 2,4,6,... is_even_pos = 1; } + j = i; // remember the final round position in table } } - return( AES_SCA_CM_ROUNDS ); + tbl[( tbl_len - 1)] |= 0x03; // Stop marker for the last item in tbl + tbl[( j - 1 )] |= 0x03; // stop marker for final - 1 real data + + return( dummy_rounds ); } +#endif /* MBEDTLS_AES_SCA_COUNTERMEASURES */ #if defined(MBEDTLS_AES_FEWER_TABLES) @@ -995,6 +999,7 @@ int mbedtls_aes_xts_setkey_dec( mbedtls_aes_xts_context *ctx, */ #if !defined(MBEDTLS_AES_ENCRYPT_ALT) +#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) static uint32_t *aes_fround( uint32_t *R, uint32_t *X0, uint32_t *X1, uint32_t *X2, uint32_t *X3, uint32_t Y0, uint32_t Y1, uint32_t Y2, uint32_t Y3 ) @@ -1051,62 +1056,65 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx, const unsigned char input[16], unsigned char output[16] ) { - int i, j, offset, start_fin_loops = 1; + int i, tindex, offset, stop_mark, dummy_rounds; aes_r_data_t aes_data_real; // real data -#if AES_SCA_CM_ROUNDS != 0 aes_r_data_t aes_data_fake; // fake data -#endif /* AES_SCA_CM_ROUNDS != 0 */ - aes_r_data_t *aes_data_ptr; // pointer to aes_data_real or aes_data_fake + aes_r_data_t *aes_data_ptr; // pointer to real or fake data aes_r_data_t *aes_data_table[2]; // pointers to real and fake data - int round_ctrl_table_len = ctx->nr - 1 + AES_SCA_CM_ROUNDS + 2 + 2; + int round_ctrl_table_len = ctx->nr + 2 + AES_SCA_CM_ROUNDS; volatile int flow_control; - // control bytes for AES rounds, reserve based on max ctx->nr - uint8_t round_ctrl_table[ 14 - 1 + AES_SCA_CM_ROUNDS + 2 + 2]; + // control bytes for AES calculation rounds, + // reserve based on max rounds + dummy rounds + 2 (for initial key addition) + uint8_t round_ctrl_table[( 14 + AES_SCA_CM_ROUNDS + 2 )]; aes_data_real.rk_ptr = ctx->rk; - aes_data_table[0] = &aes_data_real; - -#if AES_SCA_CM_ROUNDS != 0 - aes_data_table[1] = &aes_data_fake; aes_data_fake.rk_ptr = ctx->rk; - start_fin_loops = 2; - for( i = 0; i < 4; i++ ) - aes_data_fake.xy_values[i] = mbedtls_platform_random_in_range( 0xffffffff ); -#endif + aes_data_table[0] = &aes_data_real; + aes_data_table[1] = &aes_data_fake; - // Get randomized AES calculation control bytes - flow_control = aes_sca_cm_data_randomize( round_ctrl_table, - round_ctrl_table_len ); + // Get AES calculation control bytes + dummy_rounds = aes_sca_cm_data_randomize( round_ctrl_table, + round_ctrl_table_len ); + flow_control = dummy_rounds; + // SCA countermeasure, safely clear the aes_data_real.xy_values mbedtls_platform_memset( aes_data_real.xy_values, 0, 16 ); + + // SCA countermeasure, randomize secret data location by initializing it in + // a random order and writing randomized fake data between the real data + // writes. offset = mbedtls_platform_random_in_range( 4 ); - - for( i = offset; i < 4; i++ ) + i = offset; + do { GET_UINT32_LE( aes_data_real.xy_values[i], input, ( i * 4 ) ); - } + aes_data_fake.xy_values[i] = mbedtls_platform_random_in_range( 0xffffffff ); + flow_control++; + } while( ( i = ( i + 1 ) % 4 ) != offset ); - for( i = 0; i < offset; i++ ) + tindex = 0; + do { - GET_UINT32_LE( aes_data_real.xy_values[i], input, ( i * 4 ) ); - } + // Get pointer to the real or fake data + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + stop_mark = round_ctrl_table[tindex] & 0x03; - for( i = 0; i < 4; i++ ) - { - for( j = 0; j < start_fin_loops; j++ ) + // initial round key addition + for( i = 0; i < 4; i++ ) { - aes_data_ptr = - aes_data_table[round_ctrl_table[ round_ctrl_table_len - 2 + j ] >> 4]; aes_data_ptr->xy_values[i] ^= *aes_data_ptr->rk_ptr++; - flow_control++; } - } + tindex++; + flow_control++; + } while( stop_mark == 0 ); - for( i = 0; i < ( ctx->nr - 1 + AES_SCA_CM_ROUNDS ); i++ ) + // Calculate AES rounds (9, 11 or 13 rounds) + dummy rounds + do { - // Read AES control data - aes_data_ptr = aes_data_table[round_ctrl_table[i] >> 4]; - offset = round_ctrl_table[i] & 0x0f; + // Get pointer to the real or fake data + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + offset = round_ctrl_table[tindex] & 0x04; + stop_mark = round_ctrl_table[tindex] & 0x03; aes_data_ptr->rk_ptr = aes_fround( aes_data_ptr->rk_ptr, &aes_data_ptr->xy_values[0 + offset], @@ -1117,12 +1125,15 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx, aes_data_ptr->xy_values[5 - offset], aes_data_ptr->xy_values[6 - offset], aes_data_ptr->xy_values[7 - offset] ); + tindex++; flow_control++; - } + } while( stop_mark == 0 ); - for( j = 0; j < start_fin_loops; j++ ) + // Calculate final AES round + dummy rounds + do { - aes_data_ptr = aes_data_table[round_ctrl_table[ i + j ] >> 4]; + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + stop_mark = round_ctrl_table[tindex] & 0x03; aes_fround_final( aes_data_ptr->rk_ptr, &aes_data_ptr->xy_values[0], &aes_data_ptr->xy_values[1], @@ -1133,25 +1144,23 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx, aes_data_ptr->xy_values[6], aes_data_ptr->xy_values[7] ); flow_control++; - } + tindex++; + } while( stop_mark == 0 ); + // SCA countermeasure, safely clear the output mbedtls_platform_memset( output, 0, 16 ); + + // SCA countermeasure, randomize secret data location by writing to it in + // a random order. offset = mbedtls_platform_random_in_range( 4 ); - - for( i = offset; i < 4; i++ ) + i = offset; + do { PUT_UINT32_LE( aes_data_real.xy_values[i], output, ( i * 4 ) ); flow_control++; - } + } while( ( i = ( i + 1 ) % 4 ) != offset ); - for( i = 0; i < offset; i++ ) - { - PUT_UINT32_LE( aes_data_real.xy_values[i], output, ( i * 4 ) ); - flow_control++; - } - - if( flow_control == ( AES_SCA_CM_ROUNDS + ( 4 * start_fin_loops ) + - ctx->nr - 1 + AES_SCA_CM_ROUNDS + start_fin_loops + 4 ) ) + if( flow_control == tindex + dummy_rounds + 8 ) { /* Validate control path due possible fault injection */ return 0; @@ -1159,6 +1168,87 @@ int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx, return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED ); } + +#else /* MBEDTLS_AES_SCA_COUNTERMEASURES */ + +#define AES_FROUND(X0,X1,X2,X3,Y0,Y1,Y2,Y3) \ + do \ + { \ + (X0) = *RK++ ^ AES_FT0( ( (Y0) ) & 0xFF ) ^ \ + AES_FT1( ( (Y1) >> 8 ) & 0xFF ) ^ \ + AES_FT2( ( (Y2) >> 16 ) & 0xFF ) ^ \ + AES_FT3( ( (Y3) >> 24 ) & 0xFF ); \ + \ + (X1) = *RK++ ^ AES_FT0( ( (Y1) ) & 0xFF ) ^ \ + AES_FT1( ( (Y2) >> 8 ) & 0xFF ) ^ \ + AES_FT2( ( (Y3) >> 16 ) & 0xFF ) ^ \ + AES_FT3( ( (Y0) >> 24 ) & 0xFF ); \ + \ + (X2) = *RK++ ^ AES_FT0( ( (Y2) ) & 0xFF ) ^ \ + AES_FT1( ( (Y3) >> 8 ) & 0xFF ) ^ \ + AES_FT2( ( (Y0) >> 16 ) & 0xFF ) ^ \ + AES_FT3( ( (Y1) >> 24 ) & 0xFF ); \ + \ + (X3) = *RK++ ^ AES_FT0( ( (Y3) ) & 0xFF ) ^ \ + AES_FT1( ( (Y0) >> 8 ) & 0xFF ) ^ \ + AES_FT2( ( (Y1) >> 16 ) & 0xFF ) ^ \ + AES_FT3( ( (Y2) >> 24 ) & 0xFF ); \ + } while( 0 ) + +int mbedtls_internal_aes_encrypt( mbedtls_aes_context *ctx, + const unsigned char input[16], + unsigned char output[16] ) +{ + int i; + uint32_t *RK, X0, X1, X2, X3, Y0, Y1, Y2, Y3; + + RK = ctx->rk; + + GET_UINT32_LE( X0, input, 0 ); X0 ^= *RK++; + GET_UINT32_LE( X1, input, 4 ); X1 ^= *RK++; + GET_UINT32_LE( X2, input, 8 ); X2 ^= *RK++; + GET_UINT32_LE( X3, input, 12 ); X3 ^= *RK++; + + for( i = ( ctx->nr >> 1 ) - 1; i > 0; i-- ) + { + AES_FROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 ); + AES_FROUND( X0, X1, X2, X3, Y0, Y1, Y2, Y3 ); + } + + AES_FROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 ); + + X0 = *RK++ ^ \ + ( (uint32_t) FSb[ ( Y0 ) & 0xFF ] ) ^ + ( (uint32_t) FSb[ ( Y1 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) FSb[ ( Y2 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) FSb[ ( Y3 >> 24 ) & 0xFF ] << 24 ); + + X1 = *RK++ ^ \ + ( (uint32_t) FSb[ ( Y1 ) & 0xFF ] ) ^ + ( (uint32_t) FSb[ ( Y2 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) FSb[ ( Y3 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) FSb[ ( Y0 >> 24 ) & 0xFF ] << 24 ); + + X2 = *RK++ ^ \ + ( (uint32_t) FSb[ ( Y2 ) & 0xFF ] ) ^ + ( (uint32_t) FSb[ ( Y3 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) FSb[ ( Y0 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) FSb[ ( Y1 >> 24 ) & 0xFF ] << 24 ); + + X3 = *RK++ ^ \ + ( (uint32_t) FSb[ ( Y3 ) & 0xFF ] ) ^ + ( (uint32_t) FSb[ ( Y0 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) FSb[ ( Y1 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) FSb[ ( Y2 >> 24 ) & 0xFF ] << 24 ); + + PUT_UINT32_LE( X0, output, 0 ); + PUT_UINT32_LE( X1, output, 4 ); + PUT_UINT32_LE( X2, output, 8 ); + PUT_UINT32_LE( X3, output, 12 ); + + return( 0 ); +} +#endif /* MBEDTLS_AES_SCA_COUNTERMEASURES */ #endif /* !MBEDTLS_AES_ENCRYPT_ALT */ #if !defined(MBEDTLS_DEPRECATED_REMOVED) @@ -1177,6 +1267,7 @@ void mbedtls_aes_encrypt( mbedtls_aes_context *ctx, #if !defined(MBEDTLS_AES_DECRYPT_ALT) #if !defined(MBEDTLS_AES_ONLY_ENCRYPT) +#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) static uint32_t *aes_rround( uint32_t *R, uint32_t *X0, uint32_t *X1, uint32_t *X2, uint32_t *X3, uint32_t Y0, uint32_t Y1, uint32_t Y2, uint32_t Y3 ) @@ -1232,50 +1323,65 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx, const unsigned char input[16], unsigned char output[16] ) { - int i, j, offset, start_fin_loops = 1; + int i, tindex, offset, stop_mark, dummy_rounds; aes_r_data_t aes_data_real; // real data -#if AES_SCA_CM_ROUNDS != 0 aes_r_data_t aes_data_fake; // fake data -#endif /* AES_SCA_CM_ROUNDS != 0 */ - aes_r_data_t *aes_data_ptr; // pointer to aes_data_real or aes_data_fake + aes_r_data_t *aes_data_ptr; // pointer to real or fake data aes_r_data_t *aes_data_table[2]; // pointers to real and fake data - int round_ctrl_table_len = ctx->nr - 1 + AES_SCA_CM_ROUNDS + 2 + 2; - // control bytes for AES rounds, reserve based on max ctx->nr + int round_ctrl_table_len = ctx->nr + 2 + AES_SCA_CM_ROUNDS; volatile int flow_control; - uint8_t round_ctrl_table[ 14 - 1 + AES_SCA_CM_ROUNDS + 2 + 2 ]; + // control bytes for AES calculation rounds, + // reserve based on max rounds + dummy rounds + 2 (for initial key addition) + uint8_t round_ctrl_table[( 14 + AES_SCA_CM_ROUNDS + 2 )]; aes_data_real.rk_ptr = ctx->rk; - aes_data_table[0] = &aes_data_real; - -#if AES_SCA_CM_ROUNDS != 0 - aes_data_table[1] = &aes_data_fake; aes_data_fake.rk_ptr = ctx->rk; - start_fin_loops = 2; - for( i = 0; i < 4; i++ ) - aes_data_fake.xy_values[i] = mbedtls_platform_random_in_range( 0xffffffff ); -#endif + aes_data_table[0] = &aes_data_real; + aes_data_table[1] = &aes_data_fake; - // Get randomized AES calculation control bytes - flow_control = aes_sca_cm_data_randomize( round_ctrl_table, - round_ctrl_table_len ); + // Get AES calculation control bytes + dummy_rounds = aes_sca_cm_data_randomize( round_ctrl_table, + round_ctrl_table_len ); + flow_control = dummy_rounds; - for( i = 0; i < 4; i++ ) + // SCA countermeasure, safely clear the aes_data_real.xy_values + mbedtls_platform_memset( aes_data_real.xy_values, 0, 16 ); + + // SCA countermeasure, randomize secret data location by initializing it in + // a random order and writing randomized fake data between the real data + // writes. + offset = mbedtls_platform_random_in_range( 4 ); + i = offset; + do { GET_UINT32_LE( aes_data_real.xy_values[i], input, ( i * 4 ) ); - for( j = 0; j < start_fin_loops; j++ ) - { - aes_data_ptr = - aes_data_table[round_ctrl_table[ round_ctrl_table_len - 4 + j ] >> 4]; - aes_data_ptr->xy_values[i] ^= *aes_data_ptr->rk_ptr++; - flow_control++; - } - } + aes_data_fake.xy_values[i] = mbedtls_platform_random_in_range( 0xffffffff ); + flow_control++; + } while( ( i = ( i + 1 ) % 4 ) != offset ); - for( i = 0; i < ( ctx->nr - 1 + AES_SCA_CM_ROUNDS ); i++ ) + tindex = 0; + do { - // Read AES control data - aes_data_ptr = aes_data_table[round_ctrl_table[i] >> 4]; - offset = round_ctrl_table[i] & 0x0f; + // Get pointer to the real or fake data + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + stop_mark = round_ctrl_table[tindex] & 0x03; + + // initial round key addition + for( i = 0; i < 4; i++ ) + { + aes_data_ptr->xy_values[i] ^= *aes_data_ptr->rk_ptr++; + } + tindex++; + flow_control++; + } while( stop_mark == 0 ); + + // Calculate AES rounds (9, 11 or 13 rounds) + dummy rounds + do + { + // Get pointer to the real or fake data + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + offset = round_ctrl_table[tindex] & 0x04; + stop_mark = round_ctrl_table[tindex] & 0x03; aes_data_ptr->rk_ptr = aes_rround( aes_data_ptr->rk_ptr, &aes_data_ptr->xy_values[0 + offset], @@ -1286,12 +1392,15 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx, aes_data_ptr->xy_values[5 - offset], aes_data_ptr->xy_values[6 - offset], aes_data_ptr->xy_values[7 - offset] ); + tindex++; flow_control++; - } + } while( stop_mark == 0 ); - for( j = 0; j < start_fin_loops; j++ ) + // Calculate final AES round + dummy rounds + do { - aes_data_ptr = aes_data_table[round_ctrl_table[ i + j ] >> 4]; + aes_data_ptr = aes_data_table[round_ctrl_table[tindex] >> 4]; + stop_mark = round_ctrl_table[tindex] & 0x03; aes_rround_final( aes_data_ptr->rk_ptr, &aes_data_ptr->xy_values[0], &aes_data_ptr->xy_values[1], @@ -1302,16 +1411,23 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx, aes_data_ptr->xy_values[6], aes_data_ptr->xy_values[7] ); flow_control++; - } + tindex++; + } while( stop_mark == 0 ); - for( i = 0; i < 4; i++ ) + // SCA countermeasure, safely clear the output + mbedtls_platform_memset( output, 0, 16 ); + + // SCA countermeasure, randomize secret data location by writing to it in + // a random order. + offset = mbedtls_platform_random_in_range( 4 ); + i = offset; + do { PUT_UINT32_LE( aes_data_real.xy_values[i], output, ( i * 4 ) ); flow_control++; - } + } while( ( i = ( i + 1 ) % 4 ) != offset ); - if( flow_control == ( AES_SCA_CM_ROUNDS + ( 4 * start_fin_loops ) + - ctx->nr - 1 + AES_SCA_CM_ROUNDS + start_fin_loops + 4 ) ) + if( flow_control == tindex + dummy_rounds + 8 ) { /* Validate control path due possible fault injection */ return 0; @@ -1319,6 +1435,88 @@ int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx, return( MBEDTLS_ERR_PLATFORM_FAULT_DETECTED ); } + +#else /* MBEDTLS_AES_SCA_COUNTERMEASURES */ + +#define AES_RROUND(X0,X1,X2,X3,Y0,Y1,Y2,Y3) \ + do \ + { \ + (X0) = *RK++ ^ AES_RT0( ( (Y0) ) & 0xFF ) ^ \ + AES_RT1( ( (Y3) >> 8 ) & 0xFF ) ^ \ + AES_RT2( ( (Y2) >> 16 ) & 0xFF ) ^ \ + AES_RT3( ( (Y1) >> 24 ) & 0xFF ); \ + \ + (X1) = *RK++ ^ AES_RT0( ( (Y1) ) & 0xFF ) ^ \ + AES_RT1( ( (Y0) >> 8 ) & 0xFF ) ^ \ + AES_RT2( ( (Y3) >> 16 ) & 0xFF ) ^ \ + AES_RT3( ( (Y2) >> 24 ) & 0xFF ); \ + \ + (X2) = *RK++ ^ AES_RT0( ( (Y2) ) & 0xFF ) ^ \ + AES_RT1( ( (Y1) >> 8 ) & 0xFF ) ^ \ + AES_RT2( ( (Y0) >> 16 ) & 0xFF ) ^ \ + AES_RT3( ( (Y3) >> 24 ) & 0xFF ); \ + \ + (X3) = *RK++ ^ AES_RT0( ( (Y3) ) & 0xFF ) ^ \ + AES_RT1( ( (Y2) >> 8 ) & 0xFF ) ^ \ + AES_RT2( ( (Y1) >> 16 ) & 0xFF ) ^ \ + AES_RT3( ( (Y0) >> 24 ) & 0xFF ); \ + } while( 0 ) + +int mbedtls_internal_aes_decrypt( mbedtls_aes_context *ctx, + const unsigned char input[16], + unsigned char output[16] ) +{ + int i; + uint32_t *RK, X0, X1, X2, X3, Y0, Y1, Y2, Y3; + + RK = ctx->rk; + + GET_UINT32_LE( X0, input, 0 ); X0 ^= *RK++; + GET_UINT32_LE( X1, input, 4 ); X1 ^= *RK++; + GET_UINT32_LE( X2, input, 8 ); X2 ^= *RK++; + GET_UINT32_LE( X3, input, 12 ); X3 ^= *RK++; + + for( i = ( ctx->nr >> 1 ) - 1; i > 0; i-- ) + { + AES_RROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 ); + AES_RROUND( X0, X1, X2, X3, Y0, Y1, Y2, Y3 ); + } + + AES_RROUND( Y0, Y1, Y2, Y3, X0, X1, X2, X3 ); + + X0 = *RK++ ^ \ + ( (uint32_t) RSb[ ( Y0 ) & 0xFF ] ) ^ + ( (uint32_t) RSb[ ( Y3 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) RSb[ ( Y2 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) RSb[ ( Y1 >> 24 ) & 0xFF ] << 24 ); + + X1 = *RK++ ^ \ + ( (uint32_t) RSb[ ( Y1 ) & 0xFF ] ) ^ + ( (uint32_t) RSb[ ( Y0 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) RSb[ ( Y3 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) RSb[ ( Y2 >> 24 ) & 0xFF ] << 24 ); + + X2 = *RK++ ^ \ + ( (uint32_t) RSb[ ( Y2 ) & 0xFF ] ) ^ + ( (uint32_t) RSb[ ( Y1 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) RSb[ ( Y0 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) RSb[ ( Y3 >> 24 ) & 0xFF ] << 24 ); + + X3 = *RK++ ^ \ + ( (uint32_t) RSb[ ( Y3 ) & 0xFF ] ) ^ + ( (uint32_t) RSb[ ( Y2 >> 8 ) & 0xFF ] << 8 ) ^ + ( (uint32_t) RSb[ ( Y1 >> 16 ) & 0xFF ] << 16 ) ^ + ( (uint32_t) RSb[ ( Y0 >> 24 ) & 0xFF ] << 24 ); + + PUT_UINT32_LE( X0, output, 0 ); + PUT_UINT32_LE( X1, output, 4 ); + PUT_UINT32_LE( X2, output, 8 ); + PUT_UINT32_LE( X3, output, 12 ); + + return( 0 ); +} +#endif /* MBEDTLS_AES_SCA_COUNTERMEASURES */ + #endif /* !MBEDTLS_AES_ONLY_ENCRYPT */ #endif /* !MBEDTLS_AES_DECRYPT_ALT */