int dslink_handshake_read_key_pair(mbedtls_ecdh_context *ctx, char *buf) {
mbedtls_ecdh_init(ctx);
dslink_handshake_get_group(&ctx->grp);
char *q = strchr(buf, ' ');
if (!q || *(q + 1) == '\0') {
errno = 0;
return DSLINK_CRYPT_KEY_DECODE_ERR;
}
size_t len = (q - buf);
unsigned char dec[90];
size_t decLen = 0;
if (dslink_base64_url_decode(dec, sizeof(dec), &decLen,
(unsigned char *) buf, len) != 0) {
return DSLINK_CRYPT_BASE64_URL_DECODE_ERR;
}
if ((errno = mbedtls_mpi_read_binary(&ctx->d, dec, decLen)) != 0) {
return DSLINK_CRYPT_KEY_DECODE_ERR;
}
len = strlen(buf) - len - 1;
if (dslink_base64_url_decode(dec, sizeof(dec), &decLen,
(unsigned char *) (q + 1), len) != 0) {
return DSLINK_CRYPT_BASE64_URL_DECODE_ERR;
}
if ((errno = mbedtls_ecp_point_read_binary(&ctx->grp, &ctx->Q,
dec, decLen)) != 0) {
return DSLINK_CRYPT_KEY_DECODE_ERR;
}
return 0;
}
TEE_Result crypto_acipher_ecc_shared_secret(struct ecc_keypair *private_key,
struct ecc_public_key *public_key,
void *secret,
unsigned long *secret_len)
{
TEE_Result res = TEE_SUCCESS;
int lmd_res = 0;
uint8_t one[1] = { 1 };
mbedtls_ecdh_context ecdh;
size_t out_len = 0;
memset(&ecdh, 0, sizeof(ecdh));
mbedtls_ecdh_init(&ecdh);
lmd_res = mbedtls_ecp_group_load(&ecdh.grp, private_key->curve);
if (lmd_res != 0) {
res = TEE_ERROR_NOT_SUPPORTED;
goto out;
}
ecdh.d = *(mbedtls_mpi *)private_key->d;
ecdh.Qp.X = *(mbedtls_mpi *)public_key->x;
ecdh.Qp.Y = *(mbedtls_mpi *)public_key->y;
mbedtls_mpi_read_binary(&ecdh.Qp.Z, one, sizeof(one));
lmd_res = mbedtls_ecdh_calc_secret(&ecdh, &out_len, secret,
*secret_len, mbd_rand, NULL);
if (lmd_res != 0) {
res = get_tee_result(lmd_res);
goto out;
}
*secret_len = out_len;
out:
/* Reset mpi to skip freeing here, those mpis will be freed with key */
mbedtls_mpi_init(&ecdh.d);
mbedtls_mpi_init(&ecdh.Qp.X);
mbedtls_mpi_init(&ecdh.Qp.Y);
mbedtls_ecdh_free(&ecdh);
return res;
}
int dslink_handshake_generate_key_pair(mbedtls_ecdh_context *ctx) {
mbedtls_entropy_context ent;
mbedtls_entropy_init(&ent);
mbedtls_ecdh_init(ctx);
int ret = 0;
if ((ret = dslink_handshake_get_group(&ctx->grp)) != 0) {
goto exit;
}
if ((errno = mbedtls_ecp_gen_keypair(&ctx->grp,
&ctx->d,
&ctx->Q,
mbedtls_entropy_func, &ent)) != 0) {
ret = DSLINK_CRYPT_KEY_PAIR_GEN_ERR;
goto exit;
}
exit:
mbedtls_entropy_free(&ent);
return ret;
}
int main( int argc, char *argv[] )
{
int ret;
mbedtls_ecdh_context ctx_cli, ctx_srv;
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
unsigned char cli_to_srv[32], srv_to_cli[32];
const char pers[] = "ecdh";
((void) argc);
((void) argv);
mbedtls_ecdh_init( &ctx_cli );
mbedtls_ecdh_init( &ctx_srv );
mbedtls_ctr_drbg_init( &ctr_drbg );
/*
* Initialize random number generation
*/
mbedtls_printf( " . Seeding the random number generator..." );
fflush( stdout );
mbedtls_entropy_init( &entropy );
if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
(const unsigned char *) pers,
sizeof pers ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
/*
* Client: inialize context and generate keypair
*/
mbedtls_printf( " . Setting up client context..." );
fflush( stdout );
ret = mbedtls_ecp_group_load( &ctx_cli.grp, MBEDTLS_ECP_DP_CURVE25519 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret );
goto exit;
}
ret = mbedtls_ecdh_gen_public( &ctx_cli.grp, &ctx_cli.d, &ctx_cli.Q,
mbedtls_ctr_drbg_random, &ctr_drbg );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret );
goto exit;
}
ret = mbedtls_mpi_write_binary( &ctx_cli.Q.X, cli_to_srv, 32 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
/*
* Server: initialize context and generate keypair
*/
mbedtls_printf( " . Setting up server context..." );
fflush( stdout );
ret = mbedtls_ecp_group_load( &ctx_srv.grp, MBEDTLS_ECP_DP_CURVE25519 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecp_group_load returned %d\n", ret );
goto exit;
}
ret = mbedtls_ecdh_gen_public( &ctx_srv.grp, &ctx_srv.d, &ctx_srv.Q,
mbedtls_ctr_drbg_random, &ctr_drbg );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecdh_gen_public returned %d\n", ret );
goto exit;
}
ret = mbedtls_mpi_write_binary( &ctx_srv.Q.X, srv_to_cli, 32 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_write_binary returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
/*
* Server: read peer's key and generate shared secret
*/
mbedtls_printf( " . Server reading client key and computing secret..." );
fflush( stdout );
ret = mbedtls_mpi_lset( &ctx_srv.Qp.Z, 1 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret );
goto exit;
}
ret = mbedtls_mpi_read_binary( &ctx_srv.Qp.X, cli_to_srv, 32 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret );
goto exit;
}
ret = mbedtls_ecdh_compute_shared( &ctx_srv.grp, &ctx_srv.z,
&ctx_srv.Qp, &ctx_srv.d,
mbedtls_ctr_drbg_random, &ctr_drbg );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
/*
* Client: read peer's key and generate shared secret
*/
mbedtls_printf( " . Client reading server key and computing secret..." );
fflush( stdout );
ret = mbedtls_mpi_lset( &ctx_cli.Qp.Z, 1 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_lset returned %d\n", ret );
goto exit;
}
ret = mbedtls_mpi_read_binary( &ctx_cli.Qp.X, srv_to_cli, 32 );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_read_binary returned %d\n", ret );
goto exit;
}
ret = mbedtls_ecdh_compute_shared( &ctx_cli.grp, &ctx_cli.z,
&ctx_cli.Qp, &ctx_cli.d,
mbedtls_ctr_drbg_random, &ctr_drbg );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
/*
* Verification: are the computed secret equal?
*/
mbedtls_printf( " . Checking if both computed secrets are equal..." );
fflush( stdout );
ret = mbedtls_mpi_cmp_mpi( &ctx_cli.z, &ctx_srv.z );
if( ret != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ecdh_compute_shared returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n" );
exit:
#if defined(_WIN32)
mbedtls_printf( " + Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
mbedtls_ecdh_free( &ctx_srv );
mbedtls_ecdh_free( &ctx_cli );
mbedtls_ctr_drbg_free( &ctr_drbg );
mbedtls_entropy_free( &entropy );
return( ret != 0 );
}
