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sm: use micro-ecc for p256r1 calculation
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@mringwal
mringwal committed Apr 13, 2017
1 parent af03003 commit c692d77
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Showing 2 changed files with 68 additions and 27 deletions.
7 changes: 6 additions & 1 deletion example/Makefile.inc
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Expand Up @@ -5,6 +5,7 @@ VPATH += ${BTSTACK_ROOT}/src/ble/gatt-service
VPATH += ${BTSTACK_ROOT}/src/classic
VPATH += ${BTSTACK_ROOT}/example
VPATH += ${BTSTACK_ROOT}/3rd-party/mbedtls/library
VPATH += ${BTSTACK_ROOT}/3rd-party/micro-ecc
VPATH += ${BTSTACK_ROOT}/3rd-party/bluedroid/decoder/srce
VPATH += ${BTSTACK_ROOT}/3rd-party/bluedroid/encoder//srce

Expand All @@ -13,6 +14,7 @@ CFLAGS += -I${BTSTACK_ROOT}/src/ble
CFLAGS += -I${BTSTACK_ROOT}/src/classic
CFLAGS += -I${BTSTACK_ROOT}/src
CFLAGS += -I${BTSTACK_ROOT}/3rd-party/mbedtls/include
CFLAGS += -I${BTSTACK_ROOT}/3rd-party/micro-ecc
CFLAGS += -I${BTSTACK_ROOT}/3rd-party/bluedroid/decoder/include
CFLAGS += -I${BTSTACK_ROOT}/3rd-party/bluedroid/encoder/include

Expand Down Expand Up @@ -73,6 +75,9 @@ MBEDTLS = \
memory_buffer_alloc.c \
platform.c \

MICROECC = \
uECC.c

# List of files for Bluedroid SBC codec
include ${BTSTACK_ROOT}/3rd-party/bluedroid/decoder/Makefile.inc
include ${BTSTACK_ROOT}/3rd-party/bluedroid/encoder/Makefile.inc
Expand Down Expand Up @@ -130,7 +135,7 @@ EXAMPLES_USING_LE = \
CORE_OBJ = $(CORE:.c=.o)
COMMON_OBJ = $(COMMON:.c=.o)
CLASSIC_OBJ = $(CLASSIC:.c=.o)
SM_OBJ = $(SM:.c=.o) $(MBEDTLS:.c=.o)
SM_OBJ = $(SM:.c=.o) $(MICROECC:.c=.o)
ATT_OBJ = $(ATT:.c=.o)
GATT_CLIENT_OBJ = $(GATT_CLIENT:.c=.o)
GATT_SERVER_OBJ = $(GATT_SERVER:.c=.o)
Expand Down
88 changes: 62 additions & 26 deletions src/ble/sm.c
View file
Expand Up @@ -74,7 +74,8 @@
#ifdef HAVE_HCI_CONTROLLER_DHKEY_SUPPORT
#error "Support for DHKEY Support in HCI Controller not implemented yet. Please use software implementation"
#else
#define USE_MBEDTLS_FOR_ECDH
// #define USE_MBEDTLS_FOR_ECDH
#define USE_MICROECC_FOR_ECDH
#endif
#endif

Expand All @@ -86,6 +87,11 @@
#include "sm_mbedtls_allocator.h"
#endif

// Software ECDH implementation provided by micro-ecc
#ifdef USE_MICROECC_FOR_ECDH
#include "uECC.h"
#endif

#if defined(ENABLE_LE_SIGNED_WRITE) || defined(ENABLE_LE_SECURE_CONNECTIONS)
#define ENABLE_CMAC_ENGINE
#endif
Expand Down Expand Up @@ -1560,6 +1566,9 @@ static void sm_sc_calculate_dhkey(sm_key256_t dhkey){
mbedtls_ecp_point_free(&DH);
mbedtls_mpi_free(&d);
mbedtls_ecp_point_free(&Q);
#endif
#ifdef USE_MICROECC_FOR_ECDH
uECC_shared_secret(setup->sm_peer_q, ec_d, dhkey);
#endif
log_info("dhkey");
log_info_hexdump(dhkey, 32);
Expand Down Expand Up @@ -1861,7 +1870,7 @@ static void sm_run(void){

#ifdef ENABLE_LE_SECURE_CONNECTIONS
if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
#ifdef USE_MBEDTLS_FOR_ECDH
#ifndef HAVE_HCI_CONTROLLER_DHKEY_SUPPORT
sm_random_start(NULL);
#else
ec_key_generation_state = EC_KEY_GENERATION_W4_KEY;
Expand Down Expand Up @@ -2767,11 +2776,8 @@ static void sm_handle_encryption_result(uint8_t * data){
}
}

#ifdef USE_MBEDTLS_FOR_ECDH

static int sm_generate_f_rng(void * context, unsigned char * buffer, size_t size){
UNUSED(context);

#ifndef HAVE_HCI_CONTROLLER_DHKEY_SUPPORT
static int sm_generate_f_rng(unsigned char * buffer, unsigned size){
int offset = setup->sm_passkey_bit;
log_info("sm_generate_f_rng: size %u - offset %u", (int) size, offset);
while (size) {
Expand All @@ -2781,12 +2787,19 @@ static int sm_generate_f_rng(void * context, unsigned char * buffer, size_t size
setup->sm_passkey_bit = offset;
return 0;
}
#ifdef USE_MBEDTLS_FOR_ECDH
static int sm_generate_f_rng_mbedtls(void * context, unsigned char * buffer, size_t size){
UNUSED(context);
return sm_generate_f_rng(buffer, size);
}
#endif
#endif

// note: random generator is ready. this doesn NOT imply that aes engine is unused!
static void sm_handle_random_result(uint8_t * data){

#ifdef USE_MBEDTLS_FOR_ECDH
#ifndef HAVE_HCI_CONTROLLER_DHKEY_SUPPORT

if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
int num_bytes = setup->sm_passkey_bit;
memcpy(&setup->sm_peer_q[num_bytes], data, 8);
Expand All @@ -2795,19 +2808,28 @@ static void sm_handle_random_result(uint8_t * data){

if (num_bytes >= 64){

// generate EC key
// init pre-generated random data from sm_peer_q
setup->sm_passkey_bit = 0;

// generate EC key
#ifdef USE_MBEDTLS_FOR_ECDH
mbedtls_mpi d;
mbedtls_ecp_point P;
mbedtls_mpi_init(&d);
mbedtls_ecp_point_init(&P);
int res = mbedtls_ecp_gen_keypair(&mbedtls_ec_group, &d, &P, &sm_generate_f_rng, NULL);
int res = mbedtls_ecp_gen_keypair(&mbedtls_ec_group, &d, &P, &sm_generate_f_rng_mbedtls, NULL);
log_info("gen keypair %x", res);
mbedtls_mpi_write_binary(&P.X, &ec_q[0], 32);
mbedtls_mpi_write_binary(&P.Y, &ec_q[32], 32);
mbedtls_mpi_write_binary(&d, ec_d, 32);
mbedtls_ecp_point_free(&P);
mbedtls_mpi_free(&d);
#endif
#ifdef USE_MICROECC_FOR_ECDH
uECC_set_rng(&sm_generate_f_rng);
uECC_make_key(ec_q, ec_d);
#endif

ec_key_generation_state = EC_KEY_GENERATION_DONE;
log_info("Elliptic curve: d");
log_info_hexdump(ec_d,32);
Expand Down Expand Up @@ -3387,23 +3409,29 @@ static void sm_pdu_handler(uint8_t packet_type, hci_con_handle_t con_handle, uin
reverse_256(&packet[01], &setup->sm_peer_q[0]);
reverse_256(&packet[33], &setup->sm_peer_q[32]);

#ifdef USE_MBEDTLS_FOR_ECDH
// validate public key
err = 0;

#ifdef USE_MBEDTLS_FOR_ECDH
mbedtls_ecp_point Q;
mbedtls_ecp_point_init( &Q );
mbedtls_mpi_read_binary(&Q.X, &setup->sm_peer_q[0], 32);
mbedtls_mpi_read_binary(&Q.Y, &setup->sm_peer_q[32], 32);
mbedtls_mpi_lset(&Q.Z, 1);
err = mbedtls_ecp_check_pubkey(&mbedtls_ec_group, &Q);
mbedtls_ecp_point_free( & Q);
#endif
#ifdef USE_MICROECC_FOR_ECDH
err = uECC_valid_public_key(setup->sm_peer_q) == 0;
#endif

if (err){
log_error("sm: peer public key invalid %x", err);
// uses "unspecified reason", there is no "public key invalid" error code
sm_pdu_received_in_wrong_state(sm_conn);
break;
}

#endif
if (IS_RESPONDER(sm_conn->sm_role)){
// responder
sm_conn->sm_engine_state = SM_SC_SEND_PUBLIC_KEY_COMMAND;
Expand Down Expand Up @@ -3712,22 +3740,11 @@ void sm_init(void){
#endif

#ifdef USE_MBEDTLS_FOR_ECDH

#ifndef HAVE_MALLOC
sm_mbedtls_allocator_init(mbedtls_memory_buffer, sizeof(mbedtls_memory_buffer));
#endif
mbedtls_ecp_group_init(&mbedtls_ec_group);
mbedtls_ecp_group_load(&mbedtls_ec_group, MBEDTLS_ECP_DP_SECP256R1);
#if 0
// test
sm_test_use_fixed_ec_keypair();
if (sm_have_ec_keypair){
printf("test dhkey check\n");
sm_key256_t dhkey;
memcpy(setup->sm_peer_q, ec_q, 64);
sm_sc_calculate_dhkey(dhkey);
}
#endif
#endif
}

Expand All @@ -3745,19 +3762,38 @@ void sm_use_fixed_ec_keypair(uint8_t * qx, uint8_t * qy, uint8_t * d){
#endif
}

#ifdef ENABLE_LE_SECURE_CONNECTIONS
#ifndef USE_MBEDTLS_FOR_ECDH
static void parse_hex(uint8_t * buffer, const char * hex_string){
while (*hex_string){
int high_nibble = nibble_for_char(*hex_string++);
int low_nibble = nibble_for_char(*hex_string++);
*buffer++ = (high_nibble << 4) | low_nibble;
}
}
#endif
#endif

void sm_test_use_fixed_ec_keypair(void){
#ifdef ENABLE_LE_SECURE_CONNECTIONS
const char * ec_d_string = "3f49f6d4a3c55f3874c9b3e3d2103f504aff607beb40b7995899b8a6cd3c1abd";
const char * ec_qx_string = "20b003d2f297be2c5e2c83a7e9f9a5b9eff49111acf4fddbcc0301480e359de6";
const char * ec_qy_string = "dc809c49652aeb6d63329abf5a52155c766345c28fed3024741c8ed01589d28b";
#ifdef USE_MBEDTLS_FOR_ECDH
// use test keypair from spec
mbedtls_mpi x;
mbedtls_mpi_init(&x);
mbedtls_mpi_read_string( &x, 16, "3f49f6d4a3c55f3874c9b3e3d2103f504aff607beb40b7995899b8a6cd3c1abd");
mbedtls_mpi_read_string( &x, 16, ec_d_string);
mbedtls_mpi_write_binary(&x, ec_d, 32);
mbedtls_mpi_read_string( &x, 16, "20b003d2f297be2c5e2c83a7e9f9a5b9eff49111acf4fddbcc0301480e359de6");
mbedtls_mpi_read_string( &x, 16, ec_qx_string);
mbedtls_mpi_write_binary(&x, &ec_q[0], 32);
mbedtls_mpi_read_string( &x, 16, "dc809c49652aeb6d63329abf5a52155c766345c28fed3024741c8ed01589d28b");
mbedtls_mpi_read_string( &x, 16, ec_qy_string);
mbedtls_mpi_write_binary(&x, &ec_q[32], 32);
mbedtls_mpi_free(&x);
#else
parse_hex(ec_d, ec_d_string);
parse_hex(&ec_q[0], ec_qx_string);
parse_hex(&ec_q[32], ec_qy_string);
#endif
sm_have_ec_keypair = 1;
ec_key_generation_state = EC_KEY_GENERATION_DONE;
Expand Down

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