diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 6187eb0..e651f29 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -1653,6 +1653,111 @@
 #endif /* MBEDTLS_SHA512_C */
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
 
+int mbedtls_ssl_build_pms( mbedtls_ssl_context *ssl )
+{
+    int ret;
+
+    mbedtls_ssl_ciphersuite_handle_t ciphersuite_info =
+        mbedtls_ssl_handshake_get_ciphersuite( ssl->handshake );
+
+#if defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED)
+    if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_DHE_RSA )
+    {
+        if( ( ret = mbedtls_dhm_calc_secret( &ssl->handshake->dhm_ctx,
+                                      ssl->handshake->premaster,
+                                      MBEDTLS_PREMASTER_SIZE,
+                                     &ssl->handshake->pmslen,
+                                      mbedtls_ssl_conf_get_frng( ssl->conf ),
+                                      ssl->conf->p_rng ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_dhm_calc_secret", ret );
+            return( ret );
+        }
+
+        MBEDTLS_SSL_DEBUG_MPI( 3, "DHM: K ", &ssl->handshake->dhm_ctx.K  );
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED) ||                     \
+    defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED) ||                   \
+    defined(MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED) ||                      \
+    defined(MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED)
+    if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_ECDHE_RSA                       ||
+        mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA                     ||
+        mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_ECDH_RSA                        ||
+        mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA )
+    {
+        if( ( ret = mbedtls_ecdh_calc_secret( &ssl->handshake->ecdh_ctx,
+                                      &ssl->handshake->pmslen,
+                                       ssl->handshake->premaster,
+                                       MBEDTLS_MPI_MAX_SIZE,
+                                       mbedtls_ssl_conf_get_frng( ssl->conf ),
+                                       ssl->conf->p_rng ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_calc_secret", ret );
+            return( ret );
+        }
+
+        MBEDTLS_SSL_DEBUG_MPI( 3, "ECDH: z", &ssl->handshake->ecdh_ctx.z );
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED ||
+          MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED ||
+          MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED ||
+          MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
+    if( mbedtls_ssl_ciphersuite_uses_psk( ciphersuite_info ) )
+    {
+        if( ( ret = mbedtls_ssl_psk_derive_premaster( ssl,
+               mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) ) ) != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_psk_derive_premaster", ret );
+            return( ret );
+        }
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)
+    if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info ) ==
+        MBEDTLS_KEY_EXCHANGE_ECJPAKE )
+    {
+        ret = mbedtls_ecjpake_derive_secret( &ssl->handshake->ecjpake_ctx,
+                ssl->handshake->premaster, 32, &ssl->handshake->pmslen,
+                mbedtls_ssl_conf_get_frng( ssl->conf ),
+                ssl->conf->p_rng );
+        if( ret != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecjpake_derive_secret", ret );
+            return( ret );
+        }
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
+#if defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED)
+    if( mbedtls_ssl_suite_get_key_exchange( ciphersuite_info )
+        == MBEDTLS_KEY_EXCHANGE_RSA )
+    {
+        ((void) ret);
+        /* The premaster secret has already been by
+         * ssl_rsa_generate_partial_pms(). Only the
+         * PMS length needs to be set. */
+        ssl->handshake->pmslen = 48;
+    }
+    else
+#endif /* MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED */
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    return( 0 );
+}
+
 #if defined(MBEDTLS_KEY_EXCHANGE__SOME__PSK_ENABLED)
 int mbedtls_ssl_psk_derive_premaster( mbedtls_ssl_context *ssl, mbedtls_key_exchange_type_t key_ex )
 {