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sm: verify peer Q lies on elliptic curve

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This commit is contained in:
Matthias Ringwald 2016-05-13 14:22:13 +02:00
parent c8c46d5108
commit bccf5e67f5
1 changed files with 24 additions and 7 deletions
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31
src/ble/sm.c
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@ -1754,11 +1754,7 @@ static void sm_run(void){
// calculate DHKEY
mbedtls_ecp_group grp;
mbedtls_ecp_group_init( &grp );
int res = mbedtls_ecp_group_load(&grp, MBEDTLS_ECP_DP_SECP256R1);
if (res) {
log_error("dhkey: error loading curve %d", res);
break;
}
mbedtls_ecp_group_load(&grp, MBEDTLS_ECP_DP_SECP256R1);
mbedtls_ecp_point Q;
mbedtls_ecp_point_init( &Q );
mbedtls_mpi_read_binary(&Q.X, setup->sm_peer_qx, 32);
@ -1768,9 +1764,9 @@ static void sm_run(void){
// da * Pb
mbedtls_ecp_point DH;
mbedtls_ecp_point_init( &DH );
res = mbedtls_ecp_mul(&grp, &DH, &le_keypair.d, &Q, NULL, NULL);
mbedtls_ecp_mul(&grp, &DH, &le_keypair.d, &Q, NULL, NULL);
sm_key256_t dhkey;
res = mbedtls_mpi_write_binary(&DH.X, dhkey, 32);
mbedtls_mpi_write_binary(&DH.X, dhkey, 32);
log_info("dhkey");
log_info_hexdump(dhkey, 32);
@ -2670,9 +2666,30 @@ static void sm_pdu_handler(uint8_t packet_type, hci_con_handle_t con_handle, uin
sm_pdu_received_in_wrong_state(sm_conn);
break;
}
// store public key for DH Key calculation
reverse_256(&packet[01], setup->sm_peer_qx);
reverse_256(&packet[33], setup->sm_peer_qy);
#ifdef USE_MBEDTLS_FOR_ECDH
// validate public key
mbedtls_ecp_group grp;
mbedtls_ecp_group_init( &grp );
mbedtls_ecp_group_load(&grp, MBEDTLS_ECP_DP_SECP256R1);
mbedtls_ecp_point Q;
mbedtls_ecp_point_init( &Q );
mbedtls_mpi_read_binary(&Q.X, setup->sm_peer_qx, 32);
mbedtls_mpi_read_binary(&Q.Y, setup->sm_peer_qy, 32);
mbedtls_mpi_read_string(&Q.Z, 16, "1" );
err = mbedtls_ecp_check_pubkey(&grp, &Q);
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
sm_conn->sm_engine_state = SM_PH2_SEND_PUBLIC_KEY_COMMAND;
break;