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sm: use LE Random command to generate EC keypair

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This commit is contained in:
Matthias Ringwald 2016-05-29 16:21:14 +02:00
parent 901c000fcc
commit 7df18c15c3
2 changed files with 94 additions and 15 deletions
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108
src/ble/sm.c
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@ -59,6 +59,15 @@
#define USE_MBEDTLS_FOR_ECDH
#endif
#ifdef ENABLE_LE_SECURE_CONNECTIONS
#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
#endif
#endif
// Software ECDH implementation provided by mbedtls
#ifdef USE_MBEDTLS_FOR_ECDH
#if !defined(MBEDTLS_CONFIG_FILE)
@ -141,6 +150,12 @@ typedef enum {
ADDRESS_RESOLUTION_FAILED,
} address_resolution_event_t;
typedef enum {
EC_KEY_GENERATION_IDLE,
EC_KEY_GENERATION_ACTIVE,
EC_KEY_GENERATION_DONE,
} ec_key_generation_state_t;
typedef enum {
SM_STATE_VAR_DHKEY_COMMAND_RECEIVED = 1 << 0
} sm_state_var_t;
@ -150,6 +165,7 @@ typedef enum {
//
static uint8_t test_use_fixed_local_csrk;
static uint8_t test_use_fixed_ec_keypair;
// configuration
static uint8_t sm_accepted_stk_generation_methods;
@ -222,7 +238,8 @@ static btstack_linked_list_t sm_event_handlers;
// Software ECDH implementation provided by mbedtls
#ifdef USE_MBEDTLS_FOR_ECDH
mbedtls_ecp_keypair le_keypair;
static mbedtls_ecp_keypair le_keypair;
static ec_key_generation_state_t ec_key_generation_state;
#endif
//
@ -266,8 +283,8 @@ typedef struct sm_setup_context {
sm_key_t sm_ltk;
#ifdef ENABLE_LE_SECURE_CONNECTIONS
uint8_t sm_peer_qx[32];
uint8_t sm_peer_qy[32];
uint8_t sm_peer_qx[32]; // also stores random for EC key generation during init
uint8_t sm_peer_qy[32]; // ''
sm_key_t sm_peer_nonce; // might be combined with sm_peer_random
sm_key_t sm_local_nonce; // might be combined with sm_local_random
sm_key_t sm_peer_dhkey_check;
@ -276,7 +293,7 @@ typedef struct sm_setup_context {
sm_key_t sm_rb;
sm_key_t sm_t; // used for f5
sm_key_t sm_mackey;
uint8_t sm_passkey_bit;
uint8_t sm_passkey_bit; // also stores number of generated random bytes for EC key generation
uint8_t sm_state_vars;
#endif
@ -1677,6 +1694,13 @@ static void sm_run(void){
break;
}
#ifdef USE_MBEDTLS_FOR_ECDH
if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
sm_random_start(NULL);
return;
}
#endif
// random address updates
switch (rau_state){
case RAU_GET_RANDOM:
@ -2487,9 +2511,60 @@ static void sm_handle_encryption_result(uint8_t * data){
}
}
#ifdef USE_MBEDTLS_FOR_ECDH
static void sm_log_ec_keypair(void){
// print keypair
char buffer[100];
size_t len;
mbedtls_mpi_write_string( &le_keypair.d, 16, buffer, sizeof(buffer), &len);
log_info("d: %s", buffer);
mbedtls_mpi_write_string( &le_keypair.Q.X, 16, buffer, sizeof(buffer), &len);
log_info("X: %s", buffer);
mbedtls_mpi_write_string( &le_keypair.Q.Y, 16, buffer, sizeof(buffer), &len);
log_info("Y: %s", buffer);
}
static int sm_generate_f_rng(void * context, unsigned char * buffer, size_t size){
int offset = setup->sm_passkey_bit;
log_info("sm_generate_f_rng: size %u - offset %u", (int) size, offset);
while (size) {
if (offset < 32){
*buffer++ = setup->sm_peer_qx[offset++];
} else {
*buffer++ = setup->sm_peer_qx[offset++ - 32];
}
size--;
}
setup->sm_passkey_bit = offset;
return 0;
}
#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
if (ec_key_generation_state == EC_KEY_GENERATION_ACTIVE){
int num_bytes = setup->sm_passkey_bit;
if (num_bytes < 32){
memcpy(&setup->sm_peer_qx[num_bytes], data, 8);
} else {
memcpy(&setup->sm_peer_qx[num_bytes-32], data, 8);
}
num_bytes += 8;
setup->sm_passkey_bit = num_bytes;
if (num_bytes >= 64){
// generate EC key
setup->sm_passkey_bit = 0;
mbedtls_ecp_gen_key(MBEDTLS_ECP_DP_SECP256R1, &le_keypair, &sm_generate_f_rng, NULL);
sm_log_ec_keypair();
ec_key_generation_state = EC_KEY_GENERATION_DONE;
}
}
#endif
switch (rau_state){
case RAU_W4_RANDOM:
// non-resolvable vs. resolvable
@ -2584,6 +2659,12 @@ static void sm_event_packet_handler (uint8_t packet_type, uint16_t channel, uint
log_info("HCI Working!");
dkg_state = sm_persistent_irk_ready ? DKG_CALC_DHK : DKG_CALC_IRK;
rau_state = RAU_IDLE;
#ifdef USE_MBEDTLS_FOR_ECDH
if (!test_use_fixed_ec_keypair){
setup->sm_passkey_bit = 0;
ec_key_generation_state = EC_KEY_GENERATION_ACTIVE;
}
#endif
sm_run();
}
break;
@ -3248,23 +3329,20 @@ void sm_init(void){
l2cap_register_fixed_channel(sm_pdu_handler, L2CAP_CID_SECURITY_MANAGER_PROTOCOL);
#ifdef USE_MBEDTLS_FOR_ECDH
// TODO: calculate keypair using LE Random Number Generator
// use test keypair from spec initially
ec_key_generation_state = EC_KEY_GENERATION_IDLE;
#endif
}
void sm_test_use_fixed_ec_keypair(void){
test_use_fixed_ec_keypair = 1;
#ifdef USE_MBEDTLS_FOR_ECDH
// use test keypair from spec
mbedtls_ecp_keypair_init(&le_keypair);
mbedtls_ecp_group_load(&le_keypair.grp, MBEDTLS_ECP_DP_SECP256R1);
mbedtls_mpi_read_string( &le_keypair.d, 16, "3f49f6d4a3c55f3874c9b3e3d2103f504aff607beb40b7995899b8a6cd3c1abd");
mbedtls_mpi_read_string( &le_keypair.Q.X, 16, "20b003d2f297be2c5e2c83a7e9f9a5b9eff49111acf4fddbcc0301480e359de6");
mbedtls_mpi_read_string( &le_keypair.Q.Y, 16, "dc809c49652aeb6d63329abf5a52155c766345c28fed3024741c8ed01589d28b");
mbedtls_mpi_read_string( &le_keypair.Q.Z, 16, "1");
// print keypair
char buffer[100];
size_t len;
mbedtls_mpi_write_string( &le_keypair.d, 16, buffer, sizeof(buffer), &len);
log_info("d: %s", buffer);
mbedtls_mpi_write_string( &le_keypair.Q.X, 16, buffer, sizeof(buffer), &len);
log_info("X: %s", buffer);
mbedtls_mpi_write_string( &le_keypair.Q.Y, 16, buffer, sizeof(buffer), &len);
log_info("Y: %s", buffer);
#endif
}

1
src/ble/sm.h
View File

@ -272,6 +272,7 @@ int sm_le_device_index(hci_con_handle_t con_handle );
// PTS testing
void sm_test_set_irk(sm_key_t irk);
void sm_test_use_fixed_local_csrk(void);
void sm_test_use_fixed_ec_keypair(void);
#if defined __cplusplus
}