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sm: allow to use mbedTLS for ECDH by HAVE_MBEDTLS_ECC_P256

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This commit is contained in:
Matthias Ringwald 2017-09-20 16:00:23 +02:00
parent dbbeec25e8
commit 51fa0b282f
2 changed files with 110 additions and 18 deletions
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1
doc/manual/docs/how_to.md
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@ -42,6 +42,7 @@ System properties:
HAVE_MALLOC | Use dynamic memory
HAVE_AES128 | Use platform AES128 engine - not needed usually
HAVE_BTSTACK_STDIN | STDIN is available for CLI interface
HAVE_MBEDTLS_ECC_P256 | mbedTLS provides NIST P-256 operations e.g. for LE Secure Connections
Embedded platform properties:

127
src/ble/sm.c
View File

@ -76,12 +76,34 @@
#error "HCI_ACL_PAYLOAD_SIZE must be at least 69 bytes when using LE Secure Conection. Please increase HCI_ACL_PAYLOAD_SIZE or disable ENABLE_LE_SECURE_CONNECTIONS"
#endif
// Software ECDH implementation provided by micro-ecc
// configure ECC implementations
#ifdef ENABLE_LE_SECURE_CONNECTIONS
#if defined(ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS) && defined(HAVE_MBEDTLS_ECC_P256)
#error "If you already have mbedTLS (HAVE_MBEDTLS_ECC_P256), please disable uECC (USE_MICRO_ECC_FOR_ECDH) in bstack_config.h"
#endif
#ifdef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#define USE_SOFTWARE_ECDH_IMPLEMENTATION
#define USE_MICRO_ECC_FOR_ECDH
#endif
#ifdef HAVE_MBEDTLS_ECC_P256
#define USE_SOFTWARE_ECDH_IMPLEMENTATION
#define USE_MBEDTLS_FOR_ECDH
#endif
#endif /* ENABLE_LE_SECURE_CONNECTIONS */
// Software ECDH implementation provided by micro-ecc
#ifdef USE_MICRO_ECC_FOR_ECDH
#include "uECC.h"
#endif
#endif
// Software ECDH implementation provided by mbedTLS
#ifdef USE_MBEDTLS_FOR_ECDH
#include "mbedtls/config.h"
#include "mbedtls/platform.h"
#include "mbedtls/ecp.h"
#endif
#if defined(ENABLE_LE_SIGNED_WRITE) || defined(ENABLE_LE_SECURE_CONNECTIONS)
#define ENABLE_CMAC_ENGINE
#endif
@ -263,6 +285,11 @@ static uint8_t ec_d[32];
static uint8_t ec_q[64];
#endif
// Software ECDH implementation provided by mbedtls
#ifdef USE_MBEDTLS_FOR_ECDH
static mbedtls_ecp_group mbedtls_ec_group;
#endif
//
// Volume 3, Part H, Chapter 24
// "Security shall be initiated by the Security Manager in the device in the master role.
@ -1581,9 +1608,12 @@ static const sm_key_t f5_salt = { 0x6C ,0x88, 0x83, 0x91, 0xAA, 0xF5, 0xA5, 0x38
static const uint8_t f5_key_id[] = { 0x62, 0x74, 0x6c, 0x65 };
static const uint8_t f5_length[] = { 0x01, 0x00};
#ifdef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#ifdef USE_SOFTWARE_ECDH_IMPLEMENTATION
static void sm_sc_calculate_dhkey(sm_key256_t dhkey){
memset(dhkey, 0, 32);
#ifdef USE_MICRO_ECC_FOR_ECDH
#if uECC_SUPPORTS_secp256r1
// standard version
uECC_shared_secret(setup->sm_peer_q, ec_d, dhkey, uECC_secp256r1());
@ -1591,6 +1621,27 @@ static void sm_sc_calculate_dhkey(sm_key256_t dhkey){
// static version
uECC_shared_secret(setup->sm_peer_q, ec_d, dhkey);
#endif
#endif
#ifdef USE_MBEDTLS_FOR_ECDH
// da * Pb
mbedtls_mpi d;
mbedtls_ecp_point Q;
mbedtls_ecp_point DH;
mbedtls_mpi_init(&d);
mbedtls_ecp_point_init(&Q);
mbedtls_ecp_point_init(&DH);
mbedtls_mpi_read_binary(&d, ec_d, 32);
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);
mbedtls_ecp_mul(&mbedtls_ec_group, &DH, &d, &Q, NULL, NULL);
mbedtls_mpi_write_binary(&DH.X, dhkey, 32);
mbedtls_ecp_point_free(&DH);
mbedtls_mpi_free(&d);
mbedtls_ecp_point_free(&Q);
#endif
log_info("dhkey");
log_info_hexdump(dhkey, 32);
}
@ -1724,7 +1775,7 @@ static void sm_sc_calculate_remote_confirm(sm_connection_t * sm_conn){
static void sm_sc_prepare_dhkey_check(sm_connection_t * sm_conn){
#ifdef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#ifdef USE_SOFTWARE_ECDH_IMPLEMENTATION
// calculate DHKEY
sm_sc_calculate_dhkey(setup->sm_dhkey);
setup->sm_state_vars |= SM_STATE_VAR_DHKEY_CALCULATED;
@ -1904,7 +1955,7 @@ static void sm_run(void){
#ifdef ENABLE_LE_SECURE_CONNECTIONS
if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
#ifdef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#ifdef USE_SOFTWARE_ECDH_IMPLEMENTATION
sm_random_start(NULL);
#else
ec_key_generation_state = EC_KEY_GENERATION_W4_KEY;
@ -2164,7 +2215,7 @@ static void sm_run(void){
return;
}
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS)
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(USE_SOFTWARE_ECDH_IMPLEMENTATION)
if (setup->sm_state_vars & SM_STATE_VAR_DHKEY_NEEDED){
setup->sm_state_vars &= ~SM_STATE_VAR_DHKEY_NEEDED;
hci_send_cmd(&hci_le_generate_dhkey, &setup->sm_peer_q[0], &setup->sm_peer_q[32]);
@ -2835,8 +2886,8 @@ static void sm_handle_encryption_result(uint8_t * data){
}
#ifdef ENABLE_LE_SECURE_CONNECTIONS
#ifdef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#if !defined(WICED_VERSION)
#if (defined(USE_MICRO_ECC_FOR_ECDH) && !defined(WICED_VERSION)) || defined(USE_MBEDTLS_FOR_ECDH)
// @return OK
static int sm_generate_f_rng(unsigned char * buffer, unsigned size){
if (ec_key_generation_state != EC_KEY_GENERATION_ACTIVE) return 0;
@ -2850,13 +2901,19 @@ static int sm_generate_f_rng(unsigned char * buffer, unsigned size){
return 1;
}
#endif
#endif
#endif
#ifdef USE_MBEDTLS_FOR_ECDH
// @return error - just wrap sm_generate_f_rng
static int sm_generate_f_rng_mbedtls(void * context, unsigned char * buffer, size_t size){
UNUSED(context);
return sm_generate_f_rng(buffer, size) == 1;
}
#endif /* USE_MBEDTLS_FOR_ECDH */
#endif /* ENABLE_LE_SECURE_CONNECTIONS */
// note: random generator is ready. this doesn NOT imply that aes engine is unused!
static void sm_handle_random_result(uint8_t * data){
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && defined(ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS)
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && defined(USE_SOFTWARE_ECDH_IMPLEMENTATION)
if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
int num_bytes = setup->sm_passkey_bit;
@ -2870,6 +2927,8 @@ static void sm_handle_random_result(uint8_t * data){
setup->sm_passkey_bit = 0;
// generate EC key
#ifdef USE_MICRO_ECC_FOR_ECDH
#ifndef WICED_VERSION
log_info("set uECC RNG for initial key generation with 64 random bytes");
// micro-ecc from WICED SDK uses its wiced_crypto_get_random by default - no need to set it
@ -2886,7 +2945,22 @@ static void sm_handle_random_result(uint8_t * data){
#else
// static version
uECC_make_key(ec_q, ec_d);
#endif /* ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS */
#endif
#endif /* USE_MICRO_ECC_FOR_ECDH */
#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_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 /* USE_MBEDTLS_FOR_ECDH */
ec_key_generation_state = EC_KEY_GENERATION_DONE;
log_info("Elliptic curve: d");
@ -3142,7 +3216,7 @@ static void sm_event_packet_handler (uint8_t packet_type, uint16_t channel, uint
#endif
break;
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS)
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(USE_MICRO_ECC_FOR_ECDH)
case HCI_SUBEVENT_LE_READ_LOCAL_P256_PUBLIC_KEY_COMPLETE:
if (hci_subevent_le_read_local_p256_public_key_complete_get_status(packet)){
log_error("Read Local P256 Public Key failed");
@ -3281,9 +3355,9 @@ static void sm_event_packet_handler (uint8_t packet_type, uint16_t channel, uint
le_device_db_set_local_bd_addr(addr);
}
if (HCI_EVENT_IS_COMMAND_COMPLETE(packet, hci_read_local_supported_commands)){
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS)
#if defined(ENABLE_LE_SECURE_CONNECTIONS) && !defined(USE_MICRO_ECC_FOR_ECDH)
if ((packet[OFFSET_OF_DATA_IN_COMMAND_COMPLETE+1+34] & 0x06) != 0x06){
log_error("LE Secure Connections enabled, but HCI Controller doesn't support it. Please add ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS to btstack_config.h");
log_error("LE Secure Connections enabled, but HCI Controller doesn't support it. Please add USE_MICRO_ECC_FOR_ECDH to btstack_config.h");
}
#endif
}
@ -3533,9 +3607,10 @@ 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 ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
// validate public key
// validate public key using micro-ecc
err = 0;
#ifdef USE_MICRO_ECC_FOR_ECDH
#if uECC_SUPPORTS_secp256r1
// standard version
err = uECC_valid_public_key(setup->sm_peer_q, uECC_secp256r1()) == 0;
@ -3543,15 +3618,26 @@ static void sm_pdu_handler(uint8_t packet_type, hci_con_handle_t con_handle, uin
// static version
err = uECC_valid_public_key(setup->sm_peer_q) == 0;
#endif
#endif
#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
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
#ifndef ENABLE_MICRO_ECC_FOR_LE_SECURE_CONNECTIONS
#ifndef USE_MICRO_ECC_FOR_ECDH
// start calculating dhkey
setup->sm_state_vars |= SM_STATE_VAR_DHKEY_NEEDED;
#endif
@ -3866,6 +3952,11 @@ void sm_init(void){
#ifdef ENABLE_LE_SECURE_CONNECTIONS
ec_key_generation_state = EC_KEY_GENERATION_IDLE;
#endif
#ifdef USE_MBEDTLS_FOR_ECDH
mbedtls_ecp_group_init(&mbedtls_ec_group);
mbedtls_ecp_group_load(&mbedtls_ec_group, MBEDTLS_ECP_DP_SECP256R1);
#endif
}
void sm_use_fixed_ec_keypair(uint8_t * qx, uint8_t * qy, uint8_t * d){