Diff: c-utility/adapters/tlsio_mbedtls.c

Revision:

0:f7f1f0d76dd6

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/c-utility/adapters/tlsio_mbedtls.c	Thu Aug 23 06:52:14 2018 +0000
@@ -0,0 +1,756 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+#include "azure_c_shared_utility/tlsio_mbedtls.h"
+
+// DEPRECATED: the USE_MBED_TLS #define is deprecated.
+#ifdef USE_MBED_TLS
+
+#include <stdlib.h>
+
+#ifdef TIZENRT
+#include "tls/config.h"
+#include "tls/debug.h"
+#include "tls/ssl.h"
+#include "tls/entropy.h"
+#include "tls/ctr_drbg.h"
+#include "tls/error.h"
+#include "tls/certs.h"
+#include "tls/entropy_poll.h"
+#else
+#include "mbedtls/config.h"
+#include "mbedtls/debug.h"
+#include "mbedtls/ssl.h"
+#include "mbedtls/entropy.h"
+#include "mbedtls/ctr_drbg.h"
+#include "mbedtls/error.h"
+#include "mbedtls/certs.h"
+#include "mbedtls/entropy_poll.h"
+#endif
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include "azure_c_shared_utility/optimize_size.h"
+#include "azure_c_shared_utility/tlsio.h"
+#include "azure_c_shared_utility/tlsio_mbedtls.h"
+#include "azure_c_shared_utility/socketio.h"
+#include "azure_c_shared_utility/crt_abstractions.h"
+#include "azure_c_shared_utility/shared_util_options.h"
+
+#define OPTION_UNDERLYING_IO_OPTIONS        "underlying_io_options"
+
+// DEPRECATED: debug functions do not belong in the tree.
+#define MBED_TLS_DEBUG_ENABLE
+
+typedef enum TLSIO_STATE_ENUM_TAG
+{
+    TLSIO_STATE_NOT_OPEN,
+    TLSIO_STATE_OPENING_UNDERLYING_IO,
+    TLSIO_STATE_IN_HANDSHAKE,
+    TLSIO_STATE_OPEN,
+    TLSIO_STATE_CLOSING,
+    TLSIO_STATE_ERROR
+} TLSIO_STATE_ENUM;
+
+typedef struct TLS_IO_INSTANCE_TAG
+{
+    XIO_HANDLE socket_io;
+    ON_BYTES_RECEIVED on_bytes_received;
+    ON_IO_OPEN_COMPLETE on_io_open_complete;
+    ON_IO_CLOSE_COMPLETE on_io_close_complete;
+    ON_IO_ERROR on_io_error;
+    void* on_bytes_received_context;
+    void* on_io_open_complete_context;
+    void* on_io_close_complete_context;
+    void* on_io_error_context;
+    TLSIO_STATE_ENUM tlsio_state;
+    unsigned char* socket_io_read_bytes;
+    size_t socket_io_read_byte_count;
+    ON_SEND_COMPLETE on_send_complete;
+    void* on_send_complete_callback_context;
+    mbedtls_entropy_context    entropy;
+    mbedtls_ctr_drbg_context   ctr_drbg;
+    mbedtls_ssl_context        ssl;
+    mbedtls_ssl_config         config;
+    mbedtls_x509_crt           trusted_certificates_parsed;
+    mbedtls_ssl_session        ssn;
+    char*                      trusted_certificates;
+} TLS_IO_INSTANCE;
+
+static const IO_INTERFACE_DESCRIPTION tlsio_mbedtls_interface_description =
+{
+    tlsio_mbedtls_retrieveoptions,
+    tlsio_mbedtls_create,
+    tlsio_mbedtls_destroy,
+    tlsio_mbedtls_open,
+    tlsio_mbedtls_close,
+    tlsio_mbedtls_send,
+    tlsio_mbedtls_dowork,
+    tlsio_mbedtls_setoption
+};
+
+// DEPRECATED: debug functions do not belong in the tree.
+#if defined (MBED_TLS_DEBUG_ENABLE)
+void mbedtls_debug(void *ctx, int level, const char *file, int line, const char *str)
+{
+    ((void)level);
+    printf("%s (%d): %s\r\n", file, line, str);
+}
+#endif
+
+static void indicate_error(TLS_IO_INSTANCE* tls_io_instance)
+{
+    if (tls_io_instance->on_io_error != NULL)
+    {
+        tls_io_instance->on_io_error(tls_io_instance->on_io_error_context);
+    }
+}
+
+static void indicate_open_complete(TLS_IO_INSTANCE* tls_io_instance, IO_OPEN_RESULT open_result)
+{
+    if (tls_io_instance->on_io_open_complete != NULL)
+    {
+        tls_io_instance->on_io_open_complete(tls_io_instance->on_io_open_complete_context, open_result);
+    }
+}
+
+static int decode_ssl_received_bytes(TLS_IO_INSTANCE* tls_io_instance)
+{
+    int result = 0;
+    unsigned char buffer[64];
+    int rcv_bytes = 1;
+
+    while (rcv_bytes > 0)
+    {
+        rcv_bytes = mbedtls_ssl_read(&tls_io_instance->ssl, buffer, sizeof(buffer));
+        if (rcv_bytes > 0)
+        {
+            if (tls_io_instance->on_bytes_received != NULL)
+            {
+                tls_io_instance->on_bytes_received(tls_io_instance->on_bytes_received_context, buffer, rcv_bytes);
+            }
+        }
+    }
+
+    return result;
+}
+
+static void on_underlying_io_open_complete(void* context, IO_OPEN_RESULT open_result)
+{
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+    int result = 0;
+
+    if (open_result != IO_OPEN_OK)
+    {
+        xio_close(tls_io_instance->socket_io, NULL, NULL);
+        tls_io_instance->tlsio_state = TLSIO_STATE_NOT_OPEN;
+        indicate_open_complete(tls_io_instance, IO_OPEN_ERROR);
+    }
+    else
+    {
+        tls_io_instance->tlsio_state = TLSIO_STATE_IN_HANDSHAKE;
+
+        do {
+            result = mbedtls_ssl_handshake(&tls_io_instance->ssl);
+        } while (result == MBEDTLS_ERR_SSL_WANT_READ || result == MBEDTLS_ERR_SSL_WANT_WRITE);
+
+        if (result == 0)
+        {
+            tls_io_instance->tlsio_state = TLSIO_STATE_OPEN;
+            indicate_open_complete(tls_io_instance, IO_OPEN_OK);
+        }
+        else
+        {
+            xio_close(tls_io_instance->socket_io, NULL, NULL);
+            tls_io_instance->tlsio_state = TLSIO_STATE_NOT_OPEN;
+            indicate_open_complete(tls_io_instance, IO_OPEN_ERROR);
+        }
+    }
+}
+
+static void on_underlying_io_bytes_received(void* context, const unsigned char* buffer, size_t size)
+{
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+
+    unsigned char* new_socket_io_read_bytes = (unsigned char*)realloc(tls_io_instance->socket_io_read_bytes, tls_io_instance->socket_io_read_byte_count + size);
+
+    if (new_socket_io_read_bytes == NULL)
+    {
+        tls_io_instance->tlsio_state = TLSIO_STATE_ERROR;
+        indicate_error(tls_io_instance);
+    }
+    else
+    {
+        tls_io_instance->socket_io_read_bytes = new_socket_io_read_bytes;
+        (void)memcpy(tls_io_instance->socket_io_read_bytes + tls_io_instance->socket_io_read_byte_count, buffer, size);
+        tls_io_instance->socket_io_read_byte_count += size;
+    }
+}
+
+static void on_underlying_io_error(void* context)
+{
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+
+    switch (tls_io_instance->tlsio_state)
+    {
+    default:
+    case TLSIO_STATE_NOT_OPEN:
+    case TLSIO_STATE_ERROR:
+        break;
+
+    case TLSIO_STATE_OPENING_UNDERLYING_IO:
+    case TLSIO_STATE_IN_HANDSHAKE:
+        // Existing socket impls are all synchronous close, and this 
+        // adapter does not yet support async close.
+        xio_close(tls_io_instance->socket_io, NULL, NULL);
+        tls_io_instance->tlsio_state = TLSIO_STATE_NOT_OPEN;
+        indicate_open_complete(tls_io_instance, IO_OPEN_ERROR);
+        break;
+
+    case TLSIO_STATE_OPEN:
+        tls_io_instance->tlsio_state = TLSIO_STATE_ERROR;
+        indicate_error(tls_io_instance);
+        break;
+    }
+}
+
+static void on_underlying_io_close_complete_during_close(void* context)
+{
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+
+    tls_io_instance->tlsio_state = TLSIO_STATE_NOT_OPEN;
+
+    if (tls_io_instance->on_io_close_complete != NULL)
+    {
+        tls_io_instance->on_io_close_complete(tls_io_instance->on_io_close_complete_context);
+    }
+}
+
+static int on_io_recv(void *context, unsigned char *buf, size_t sz)
+{
+    int result;
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+    unsigned char* new_socket_io_read_bytes;
+
+    while (tls_io_instance->socket_io_read_byte_count == 0)
+    {
+        xio_dowork(tls_io_instance->socket_io);
+        if (tls_io_instance->tlsio_state == TLSIO_STATE_OPEN)
+        {
+            break;
+        }
+    }
+
+    result = tls_io_instance->socket_io_read_byte_count;
+    if (result > sz)
+    {
+        result = sz;
+    }
+
+    if (result > 0)
+    {
+        (void)memcpy((void *)buf, tls_io_instance->socket_io_read_bytes, result);
+        (void)memmove(tls_io_instance->socket_io_read_bytes, tls_io_instance->socket_io_read_bytes + result, tls_io_instance->socket_io_read_byte_count - result);
+        tls_io_instance->socket_io_read_byte_count -= result;
+        if (tls_io_instance->socket_io_read_byte_count > 0)
+        {
+            new_socket_io_read_bytes = (unsigned char*)realloc(tls_io_instance->socket_io_read_bytes, tls_io_instance->socket_io_read_byte_count);
+            if (new_socket_io_read_bytes != NULL)
+            {
+                tls_io_instance->socket_io_read_bytes = new_socket_io_read_bytes;
+            }
+        }
+        else
+        {
+            free(tls_io_instance->socket_io_read_bytes);
+            tls_io_instance->socket_io_read_bytes = NULL;
+        }
+    }
+
+
+    if ((result == 0) && (tls_io_instance->tlsio_state == TLSIO_STATE_OPEN))
+    {
+        result = MBEDTLS_ERR_SSL_WANT_READ;
+    }
+
+    return result;
+}
+
+static int on_io_send(void *context, const unsigned char *buf, size_t sz)
+{
+    int result;
+    TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)context;
+
+    if (xio_send(tls_io_instance->socket_io, buf, sz, tls_io_instance->on_send_complete, tls_io_instance->on_send_complete_callback_context) != 0)
+    {
+        tls_io_instance->tlsio_state = TLSIO_STATE_ERROR;
+        indicate_error(tls_io_instance);
+        result = 0;
+    }
+    else
+    {
+        result = sz;
+    }
+
+    return result;
+}
+
+static int tlsio_entropy_poll(void *v, unsigned char *output, size_t len, size_t *olen)
+{
+    srand(time(NULL));
+    char *c = (char*)malloc(len);
+    memset(c, 0, len);
+    for (uint16_t i = 0; i < len; i++) {
+        c[i] = rand() % 256;
+    }
+    memmove(output, c, len);
+    *olen = len;
+
+    free(c);
+    return(0);
+}
+
+static void mbedtls_init(void *instance, const char *host) {
+    TLS_IO_INSTANCE *result = (TLS_IO_INSTANCE *)instance;
+    char *pers = "azure_iot_client";
+
+    // mbedTLS initialize...
+    mbedtls_entropy_init(&result->entropy);
+    mbedtls_ctr_drbg_init(&result->ctr_drbg);
+    mbedtls_ssl_init(&result->ssl);
+    mbedtls_ssl_session_init(&result->ssn);
+    mbedtls_ssl_config_init(&result->config);
+    mbedtls_x509_crt_init(&result->trusted_certificates_parsed);
+    mbedtls_entropy_add_source(&result->entropy, tlsio_entropy_poll, NULL, 128, 0);
+    mbedtls_ctr_drbg_seed(&result->ctr_drbg, mbedtls_entropy_func, &result->entropy, (const unsigned char *)pers, strlen(pers));
+    mbedtls_ssl_config_defaults(&result->config, MBEDTLS_SSL_IS_CLIENT, MBEDTLS_SSL_TRANSPORT_STREAM, MBEDTLS_SSL_PRESET_DEFAULT);
+    mbedtls_ssl_conf_rng(&result->config, mbedtls_ctr_drbg_random, &result->ctr_drbg);
+    mbedtls_ssl_conf_authmode(&result->config, MBEDTLS_SSL_VERIFY_REQUIRED);
+    mbedtls_ssl_conf_min_version(&result->config, MBEDTLS_SSL_MAJOR_VERSION_3, MBEDTLS_SSL_MINOR_VERSION_3);          // v1.2
+    mbedtls_ssl_set_bio(&result->ssl, instance, on_io_send, on_io_recv, NULL);
+    mbedtls_ssl_set_hostname(&result->ssl, host);
+    mbedtls_ssl_set_session(&result->ssl, &result->ssn);
+
+    // DEPRECATED: debug functions do not belong in the tree.
+#if defined (MBED_TLS_DEBUG_ENABLE)
+    mbedtls_ssl_conf_dbg(&result->config, mbedtls_debug, stdout);
+    mbedtls_debug_set_threshold(1);
+#endif
+
+    mbedtls_ssl_setup(&result->ssl, &result->config);
+}
+
+CONCRETE_IO_HANDLE tlsio_mbedtls_create(void* io_create_parameters)
+{
+    TLSIO_CONFIG* tls_io_config = io_create_parameters;
+    TLS_IO_INSTANCE* result;
+
+    if (tls_io_config == NULL)
+    {
+        LogError("NULL tls_io_config");
+        result = NULL;
+    }
+    else
+    {
+        result = malloc(sizeof(TLS_IO_INSTANCE));
+        if (result != NULL)
+        {
+            SOCKETIO_CONFIG socketio_config;
+            const IO_INTERFACE_DESCRIPTION* underlying_io_interface;
+            void* io_interface_parameters;
+
+            if (tls_io_config->underlying_io_interface != NULL)
+            {
+                underlying_io_interface = tls_io_config->underlying_io_interface;
+                io_interface_parameters = tls_io_config->underlying_io_parameters;
+            }
+            else
+            {
+                socketio_config.hostname = tls_io_config->hostname;
+                socketio_config.port = tls_io_config->port;
+                socketio_config.accepted_socket = NULL;
+
+                underlying_io_interface = socketio_get_interface_description();
+                io_interface_parameters = &socketio_config;
+            }
+
+            if (underlying_io_interface == NULL)
+            {
+                free(result);
+                result = NULL;
+                LogError("Failed getting socket IO interface description.");
+            }
+            else
+            {
+                result->on_bytes_received = NULL;
+                result->on_bytes_received_context = NULL;
+
+                result->on_io_open_complete = NULL;
+                result->on_io_open_complete_context = NULL;
+
+                result->on_io_close_complete = NULL;
+                result->on_io_close_complete_context = NULL;
+
+                result->on_io_error = NULL;
+                result->on_io_error_context = NULL;
+
+                result->trusted_certificates = NULL;
+
+                result->socket_io = xio_create(underlying_io_interface, io_interface_parameters);
+                if (result->socket_io == NULL)
+                {
+                    LogError("socket xio create failed");
+                    free(result);
+                    result = NULL;
+                }
+                else
+                {
+                    result->socket_io_read_bytes = NULL;
+                    result->socket_io_read_byte_count = 0;
+                    result->on_send_complete = NULL;
+                    result->on_send_complete_callback_context = NULL;
+
+                    // mbeTLS initialize
+                    mbedtls_init((void *)result, tls_io_config->hostname);
+                    result->tlsio_state = TLSIO_STATE_NOT_OPEN;
+                }
+            }
+        }
+    }
+
+    return result;
+}
+
+void tlsio_mbedtls_destroy(CONCRETE_IO_HANDLE tls_io)
+{
+    if (tls_io != NULL)
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        // mbedTLS cleanup...
+        mbedtls_ssl_close_notify(&tls_io_instance->ssl);
+        mbedtls_ssl_free(&tls_io_instance->ssl);
+        mbedtls_ssl_config_free(&tls_io_instance->config);
+        mbedtls_x509_crt_free(&tls_io_instance->trusted_certificates_parsed);
+        mbedtls_ctr_drbg_free(&tls_io_instance->ctr_drbg);
+        mbedtls_entropy_free(&tls_io_instance->entropy);
+
+        xio_close(tls_io_instance->socket_io, NULL, NULL);
+
+        if (tls_io_instance->socket_io_read_bytes != NULL)
+        {
+            free(tls_io_instance->socket_io_read_bytes);
+        }
+
+        xio_destroy(tls_io_instance->socket_io);
+        if (tls_io_instance->trusted_certificates != NULL)
+        {
+            free(tls_io_instance->trusted_certificates);
+        }
+        free(tls_io);
+    }
+}
+
+int tlsio_mbedtls_open(CONCRETE_IO_HANDLE tls_io, ON_IO_OPEN_COMPLETE on_io_open_complete, void* on_io_open_complete_context, ON_BYTES_RECEIVED on_bytes_received, void* on_bytes_received_context, ON_IO_ERROR on_io_error, void* on_io_error_context)
+{
+    int result = 0;
+
+    if (tls_io == NULL)
+    {
+        LogError("NULL tls_io");
+        result = __FAILURE__;
+    }
+    else
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        if (tls_io_instance->tlsio_state != TLSIO_STATE_NOT_OPEN)
+        {
+            LogError("IO should not be open: %d\n", tls_io_instance->tlsio_state);
+            result = __FAILURE__;
+        }
+        else
+        {
+            tls_io_instance->on_bytes_received = on_bytes_received;
+            tls_io_instance->on_bytes_received_context = on_bytes_received_context;
+
+            tls_io_instance->on_io_open_complete = on_io_open_complete;
+            tls_io_instance->on_io_open_complete_context = on_io_open_complete_context;
+
+            tls_io_instance->on_io_error = on_io_error;
+            tls_io_instance->on_io_error_context = on_io_error_context;
+
+            tls_io_instance->tlsio_state = TLSIO_STATE_OPENING_UNDERLYING_IO;
+
+            if (xio_open(tls_io_instance->socket_io, on_underlying_io_open_complete, tls_io_instance, on_underlying_io_bytes_received, tls_io_instance, on_underlying_io_error, tls_io_instance) != 0)
+            {
+                LogError("Underlying IO open failed");
+                tls_io_instance->tlsio_state = TLSIO_STATE_NOT_OPEN;
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+    }
+
+    return result;
+}
+
+int tlsio_mbedtls_close(CONCRETE_IO_HANDLE tls_io, ON_IO_CLOSE_COMPLETE on_io_close_complete, void* callback_context)
+{
+    int result = 0;
+
+    if (tls_io == NULL)
+    {
+        result = __FAILURE__;
+    }
+    else
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        if ((tls_io_instance->tlsio_state == TLSIO_STATE_NOT_OPEN) ||
+            (tls_io_instance->tlsio_state == TLSIO_STATE_CLOSING))
+        {
+            result = __FAILURE__;
+        }
+        else
+        {
+            tls_io_instance->tlsio_state = TLSIO_STATE_CLOSING;
+            tls_io_instance->on_io_close_complete = on_io_close_complete;
+            tls_io_instance->on_io_close_complete_context = callback_context;
+
+            if (xio_close(tls_io_instance->socket_io,
+                on_underlying_io_close_complete_during_close, tls_io_instance) != 0)
+            {
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+    }
+
+    return result;
+}
+
+int tlsio_mbedtls_send(CONCRETE_IO_HANDLE tls_io, const void* buffer, size_t size, ON_SEND_COMPLETE on_send_complete, void* callback_context)
+{
+    int result;
+
+    if (tls_io == NULL)
+    {
+        result = __FAILURE__;
+    }
+    else
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        if (tls_io_instance->tlsio_state != TLSIO_STATE_OPEN)
+        {
+            result = __FAILURE__;
+        }
+        else
+        {
+            tls_io_instance->on_send_complete = on_send_complete;
+            tls_io_instance->on_send_complete_callback_context = callback_context;
+
+            int res = mbedtls_ssl_write(&tls_io_instance->ssl, buffer, size);
+            if (res != size)
+            {
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+    }
+
+    return result;
+}
+
+void tlsio_mbedtls_dowork(CONCRETE_IO_HANDLE tls_io)
+{
+    if (tls_io != NULL)
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        if ((tls_io_instance->tlsio_state != TLSIO_STATE_NOT_OPEN) &&
+            (tls_io_instance->tlsio_state != TLSIO_STATE_ERROR))
+        {
+            decode_ssl_received_bytes(tls_io_instance);
+            xio_dowork(tls_io_instance->socket_io);
+        }
+    }
+}
+
+const IO_INTERFACE_DESCRIPTION* tlsio_mbedtls_get_interface_description(void)
+{
+    return &tlsio_mbedtls_interface_description;
+}
+
+/*this function will clone an option given by name and value*/
+static void* tlsio_mbedtls_CloneOption(const char* name, const void* value)
+{
+    void* result;
+    if (
+        (name == NULL) || (value == NULL)
+        )
+    {
+        LogError("invalid parameter detected: const char* name=%p, const void* value=%p", name, value);
+        result = NULL;
+    }
+    else
+    {
+        if (strcmp(name, OPTION_UNDERLYING_IO_OPTIONS) == 0)
+        {
+            result = (void*)value;
+        }
+        else if (strcmp(name, OPTION_TRUSTED_CERT) == 0)
+        {
+            if (mallocAndStrcpy_s((char**)&result, value) != 0)
+            {
+                LogError("unable to mallocAndStrcpy_s TrustedCerts value");
+                result = NULL;
+            }
+            else
+            {
+                /*return as is*/
+            }
+        }
+        else
+        {
+            LogError("not handled option : %s", name);
+            result = NULL;
+        }
+    }
+    return result;
+}
+
+/*this function destroys an option previously created*/
+static void tlsio_mbedtls_DestroyOption(const char* name, const void* value)
+{
+    /*since all options for this layer are actually string copies., disposing of one is just calling free*/
+    if (name == NULL || value == NULL)
+    {
+        LogError("invalid parameter detected: const char* name=%p, const void* value=%p", name, value);
+    }
+    else
+    {
+        if (strcmp(name, OPTION_TRUSTED_CERT) == 0)
+        {
+            free((void*)value);
+        }
+        else if (strcmp(name, OPTION_UNDERLYING_IO_OPTIONS) == 0)
+        {
+            OptionHandler_Destroy((OPTIONHANDLER_HANDLE)value);
+        }
+        else
+        {
+            LogError("not handled option : %s", name);
+        }
+    }
+}
+
+OPTIONHANDLER_HANDLE tlsio_mbedtls_retrieveoptions(CONCRETE_IO_HANDLE handle)
+{
+    OPTIONHANDLER_HANDLE result;
+    if (handle == NULL)
+    {
+        LogError("invalid parameter detected: CONCRETE_IO_HANDLE handle=%p", handle);
+        result = NULL;
+    }
+    else
+    {
+        result = OptionHandler_Create(tlsio_mbedtls_CloneOption, tlsio_mbedtls_DestroyOption, tlsio_mbedtls_setoption);
+        if (result == NULL)
+        {
+            LogError("unable to OptionHandler_Create");
+            /*return as is*/
+        }
+        else
+        {
+            /*this layer cares about the certificates*/
+            TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)handle;
+            OPTIONHANDLER_HANDLE underlying_io_options;
+
+            if ((underlying_io_options = xio_retrieveoptions(tls_io_instance->socket_io)) == NULL ||
+                OptionHandler_AddOption(result, OPTION_UNDERLYING_IO_OPTIONS, underlying_io_options) != OPTIONHANDLER_OK)
+            {
+                LogError("unable to save underlying_io options");
+                OptionHandler_Destroy(underlying_io_options);
+                OptionHandler_Destroy(result);
+                result = NULL;
+            }
+            else if (tls_io_instance->trusted_certificates != NULL &&
+                OptionHandler_AddOption(result, OPTION_TRUSTED_CERT, tls_io_instance->trusted_certificates) != OPTIONHANDLER_OK)
+            {
+                LogError("unable to save TrustedCerts option");
+                OptionHandler_Destroy(result);
+                result = NULL;
+            }
+            else
+            {
+                /*all is fine, all interesting options have been saved*/
+                /*return as is*/
+            }
+        }
+    }
+    return result;
+}
+
+int tlsio_mbedtls_setoption(CONCRETE_IO_HANDLE tls_io, const char* optionName, const void* value)
+{
+    int result;
+
+    if (tls_io == NULL || optionName == NULL)
+    {
+        result = __FAILURE__;
+    }
+    else
+    {
+        TLS_IO_INSTANCE* tls_io_instance = (TLS_IO_INSTANCE*)tls_io;
+
+        if (strcmp(OPTION_TRUSTED_CERT, optionName) == 0)
+        {
+            if (tls_io_instance->trusted_certificates != NULL)
+            {
+                // Free the memory if it has been previously allocated
+                free(tls_io_instance->trusted_certificates);
+                tls_io_instance->trusted_certificates = NULL;
+            }
+            if (mallocAndStrcpy_s(&tls_io_instance->trusted_certificates, (const char*)value) != 0)
+            {
+                LogError("unable to mallocAndStrcpy_s");
+                result = __FAILURE__;
+            }
+            else
+            {
+                int parse_result = mbedtls_x509_crt_parse(&tls_io_instance->trusted_certificates_parsed, (const unsigned char *)value, (int)(strlen(value) + 1));
+                if (parse_result != 0)
+                {
+                    LogInfo("Malformed pem certificate");
+                    result = __FAILURE__;
+                }
+                else
+                {
+                    mbedtls_ssl_conf_ca_chain(&tls_io_instance->config, &tls_io_instance->trusted_certificates_parsed, NULL);
+                    result = 0;
+                }
+            }
+        }
+        else
+        {
+            // tls_io_instance->socket_io is never NULL
+            result = xio_setoption(tls_io_instance->socket_io, optionName, value);
+        }
+    }
+
+    return result;
+}
+
+// DEPRECATED: the USE_MBED_TLS #define is deprecated.
+#endif // USE_MBED_TLS