programs/ssl/dtls_client.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  *  Simple DTLS client demonstration program
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */

 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif

 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
 #define mbedtls_printf     printf
 #define mbedtls_fprintf    fprintf
 #endif

 #if !defined(MBEDTLS_SSL_CLI_C) || !defined(MBEDTLS_SSL_PROTO_DTLS) ||    \
     !defined(MBEDTLS_NET_C)  || !defined(MBEDTLS_TIMING_C) ||             \
     !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_CTR_DRBG_C) ||        \
     !defined(MBEDTLS_X509_CRT_PARSE_C) || !defined(MBEDTLS_RSA_C) ||      \
     !defined(MBEDTLS_CERTS_C) || !defined(MBEDTLS_PEM_PARSE_C)
 int main( void )
 {
     mbedtls_printf( "MBEDTLS_SSL_CLI_C and/or MBEDTLS_SSL_PROTO_DTLS and/or "
             "MBEDTLS_NET_C and/or MBEDTLS_TIMING_C and/or "
             "MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
             "MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
             "MBEDTLS_CERTS_C and/or MBEDTLS_PEM_PARSE_C not defined.\n" );
     return( 0 );
 }
 #else

 #include <string.h>

 #include "mbedtls/net_sockets.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/timing.h"

 /* Uncomment out the following line to default to IPv4 and disable IPv6 */
 //#define FORCE_IPV4

 #define SERVER_PORT "4433"
 #define SERVER_NAME "localhost"

 #ifdef FORCE_IPV4
 #define SERVER_ADDR "127.0.0.1"     /* Forces IPv4 */
 #else
 #define SERVER_ADDR "::1"
 #endif

 #define MESSAGE     "Echo this"

 #define READ_TIMEOUT_MS 1000
 #define MAX_RETRY       5

 #define DEBUG_LEVEL 0

 static void my_debug( void *ctx, int level,
                       const char *file, int line,
                       const char *str )
 {
     ((void) level);

     mbedtls_fprintf( (FILE *) ctx, "%s:%04d: %s", file, line, str );
     fflush(  (FILE *) ctx  );
 }

 int main( int argc, char *argv[] )
 {
     int ret, len;
     mbedtls_net_context server_fd;
     uint32_t flags;
     unsigned char buf[1024];
     const char *pers = "dtls_client";
     int retry_left = MAX_RETRY;

     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
     mbedtls_ssl_context ssl;
     mbedtls_ssl_config conf;
     mbedtls_x509_crt cacert;
     mbedtls_timing_delay_context timer;

     ((void) argc);
     ((void) argv);

 #if defined(MBEDTLS_DEBUG_C)
     mbedtls_debug_set_threshold( DEBUG_LEVEL );
 #endif

     /*
      * 0. Initialize the RNG and the session data
      */
     mbedtls_net_init( &server_fd );
     mbedtls_ssl_init( &ssl );
     mbedtls_ssl_config_init( &conf );
     mbedtls_x509_crt_init( &cacert );
     mbedtls_ctr_drbg_init( &ctr_drbg );

     mbedtls_printf( "\n  . 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,
                                strlen( pers ) ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret );
         goto exit;
     }

     mbedtls_printf( " ok\n" );

     /*
      * 0. Load certificates
      */
     mbedtls_printf( "  . Loading the CA root certificate ..." );
     fflush( stdout );

     ret = mbedtls_x509_crt_parse( &cacert, (const unsigned char *) mbedtls_test_cas_pem,
                           mbedtls_test_cas_pem_len );
     if( ret < 0 )
     {
         mbedtls_printf( " failed\n  !  mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
         goto exit;
     }

     mbedtls_printf( " ok (%d skipped)\n", ret );

     /*
      * 1. Start the connection
      */
     mbedtls_printf( "  . Connecting to udp/%s/%s...", SERVER_NAME, SERVER_PORT );
     fflush( stdout );

     if( ( ret = mbedtls_net_connect( &server_fd, SERVER_ADDR,
                                          SERVER_PORT, MBEDTLS_NET_PROTO_UDP ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_net_connect returned %d\n\n", ret );
         goto exit;
     }

     mbedtls_printf( " ok\n" );

     /*
      * 2. Setup stuff
      */
     mbedtls_printf( "  . Setting up the DTLS structure..." );
     fflush( stdout );

     if( ( ret = mbedtls_ssl_config_defaults( &conf,
                    MBEDTLS_SSL_IS_CLIENT,
                    MBEDTLS_SSL_TRANSPORT_DATAGRAM,
                    MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
         goto exit;
     }

     /* OPTIONAL is usually a bad choice for security, but makes interop easier
      * in this simplified example, in which the ca chain is hardcoded.
      * Production code should set a proper ca chain and use REQUIRED. */
     mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
     mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
     mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
     mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );

     if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_setup returned %d\n\n", ret );
         goto exit;
     }

     if( ( ret = mbedtls_ssl_set_hostname( &ssl, SERVER_NAME ) ) != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_set_hostname returned %d\n\n", ret );
         goto exit;
     }

     mbedtls_ssl_set_bio( &ssl, &server_fd,
                          mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );

     mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
                                             mbedtls_timing_get_delay );

     mbedtls_printf( " ok\n" );

     /*
      * 4. Handshake
      */
     mbedtls_printf( "  . Performing the DTLS handshake..." );
     fflush( stdout );

     do ret = mbedtls_ssl_handshake( &ssl );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret != 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
         goto exit;
     }

     mbedtls_printf( " ok\n" );

     /*
      * 5. Verify the server certificate
      */
     mbedtls_printf( "  . Verifying peer X.509 certificate..." );

     /* In real life, we would have used MBEDTLS_SSL_VERIFY_REQUIRED so that the
      * handshake would not succeed if the peer's cert is bad.  Even if we used
      * MBEDTLS_SSL_VERIFY_OPTIONAL, we would bail out here if ret != 0 */
     if( ( flags = mbedtls_ssl_get_verify_result( &ssl ) ) != 0 )
     {
         char vrfy_buf[512];

         mbedtls_printf( " failed\n" );

         mbedtls_x509_crt_verify_info( vrfy_buf, sizeof( vrfy_buf ), "  ! ", flags );

         mbedtls_printf( "%s\n", vrfy_buf );
     }
     else
         mbedtls_printf( " ok\n" );

     /*
      * 6. Write the echo request
      */
 send_request:
     mbedtls_printf( "  > Write to server:" );
     fflush( stdout );

     len = sizeof( MESSAGE ) - 1;

     do ret = mbedtls_ssl_write( &ssl, (unsigned char *) MESSAGE, len );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret < 0 )
     {
         mbedtls_printf( " failed\n  ! mbedtls_ssl_write returned %d\n\n", ret );
         goto exit;
     }

     len = ret;
     mbedtls_printf( " %d bytes written\n\n%s\n\n", len, MESSAGE );

     /*
      * 7. Read the echo response
      */
     mbedtls_printf( "  < Read from server:" );
     fflush( stdout );

     len = sizeof( buf ) - 1;
     memset( buf, 0, sizeof( buf ) );

     do ret = mbedtls_ssl_read( &ssl, buf, len );
     while( ret == MBEDTLS_ERR_SSL_WANT_READ ||
            ret == MBEDTLS_ERR_SSL_WANT_WRITE );

     if( ret <= 0 )
     {
         switch( ret )
         {
             case MBEDTLS_ERR_SSL_TIMEOUT:
                 mbedtls_printf( " timeout\n\n" );
                 if( retry_left-- > 0 )
                     goto send_request;
                 goto exit;

             case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
                 mbedtls_printf( " connection was closed gracefully\n" );
                 ret = 0;
                 goto close_notify;

             default:
                 mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", -ret );
                 goto exit;
         }
     }

     len = ret;
     mbedtls_printf( " %d bytes read\n\n%s\n\n", len, buf );

     /*
      * 8. Done, cleanly close the connection
      */
 close_notify:
     mbedtls_printf( "  . Closing the connection..." );

     /* No error checking, the connection might be closed already */
     do ret = mbedtls_ssl_close_notify( &ssl );
     while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
     ret = 0;

     mbedtls_printf( " done\n" );

     /*
      * 9. Final clean-ups and exit
      */
 exit:

 #ifdef MBEDTLS_ERROR_C
     if( ret != 0 )
     {
         char error_buf[100];
         mbedtls_strerror( ret, error_buf, 100 );
         mbedtls_printf( "Last error was: %d - %s\n\n", ret, error_buf );
     }
 #endif

     mbedtls_net_free( &server_fd );

     mbedtls_x509_crt_free( &cacert );
     mbedtls_ssl_free( &ssl );
     mbedtls_ssl_config_free( &conf );
     mbedtls_ctr_drbg_free( &ctr_drbg );
     mbedtls_entropy_free( &entropy );

 #if defined(_WIN32)
     mbedtls_printf( "  + Press Enter to exit this program.\n" );
     fflush( stdout ); getchar();
 #endif

     /* Shell can not handle large exit numbers -> 1 for errors */
     if( ret < 0 )
         ret = 1;

     return( ret );
 }
 #endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_DTLS && MBEDTLS_NET_C &&
           MBEDTLD_TIMING_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
           MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C && MBEDTLS_CERTS_C &&
           MBEDTLS_PEM_PARSE_C */
	/*
	* Simple DTLS client demonstration program
	*
	* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	* This file is part of mbed TLS (https://tls.mbed.org)
	*/

	#if !defined(MBEDTLS_CONFIG_FILE)
	#include "mbedtls/config.h"
	#else
	#include MBEDTLS_CONFIG_FILE
	#endif

	#if defined(MBEDTLS_PLATFORM_C)
	#include "mbedtls/platform.h"
	#else
	#include <stdio.h>
	#define mbedtls_printf printf
	#define mbedtls_fprintf fprintf
	#endif

	#if !defined(MBEDTLS_SSL_CLI_C) \|\| !defined(MBEDTLS_SSL_PROTO_DTLS) \|\| \
	!defined(MBEDTLS_NET_C) \|\| !defined(MBEDTLS_TIMING_C) \|\| \
	!defined(MBEDTLS_ENTROPY_C) \|\| !defined(MBEDTLS_CTR_DRBG_C) \|\| \
	!defined(MBEDTLS_X509_CRT_PARSE_C) \|\| !defined(MBEDTLS_RSA_C) \|\| \
	!defined(MBEDTLS_CERTS_C) \|\| !defined(MBEDTLS_PEM_PARSE_C)
	int main( void )
	{
	mbedtls_printf( "MBEDTLS_SSL_CLI_C and/or MBEDTLS_SSL_PROTO_DTLS and/or "
	"MBEDTLS_NET_C and/or MBEDTLS_TIMING_C and/or "
	"MBEDTLS_ENTROPY_C and/or MBEDTLS_CTR_DRBG_C and/or "
	"MBEDTLS_X509_CRT_PARSE_C and/or MBEDTLS_RSA_C and/or "
	"MBEDTLS_CERTS_C and/or MBEDTLS_PEM_PARSE_C not defined.\n" );
	return( 0 );
	}
	#else

	#include <string.h>

	#include "mbedtls/net_sockets.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/timing.h"

	/* Uncomment out the following line to default to IPv4 and disable IPv6 */
	//#define FORCE_IPV4

	#define SERVER_PORT "4433"
	#define SERVER_NAME "localhost"

	#ifdef FORCE_IPV4
	#define SERVER_ADDR "127.0.0.1" /* Forces IPv4 */
	#else
	#define SERVER_ADDR "::1"
	#endif

	#define MESSAGE "Echo this"

	#define READ_TIMEOUT_MS 1000
	#define MAX_RETRY 5

	#define DEBUG_LEVEL 0

	static void my_debug( void *ctx, int level,
	const char *file, int line,
	const char *str )
	{
	((void) level);

	mbedtls_fprintf( (FILE *) ctx, "%s:%04d: %s", file, line, str );
	fflush( (FILE *) ctx );
	}

	int main( int argc, char *argv[] )
	{
	int ret, len;
	mbedtls_net_context server_fd;
	uint32_t flags;
	unsigned char buf[1024];
	const char *pers = "dtls_client";
	int retry_left = MAX_RETRY;

	mbedtls_entropy_context entropy;
	mbedtls_ctr_drbg_context ctr_drbg;
	mbedtls_ssl_context ssl;
	mbedtls_ssl_config conf;
	mbedtls_x509_crt cacert;
	mbedtls_timing_delay_context timer;

	((void) argc);
	((void) argv);

	#if defined(MBEDTLS_DEBUG_C)
	mbedtls_debug_set_threshold( DEBUG_LEVEL );
	#endif

	/*
	* 0. Initialize the RNG and the session data
	*/
	mbedtls_net_init( &server_fd );
	mbedtls_ssl_init( &ssl );
	mbedtls_ssl_config_init( &conf );
	mbedtls_x509_crt_init( &cacert );
	mbedtls_ctr_drbg_init( &ctr_drbg );

	mbedtls_printf( "\n . 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,
	strlen( pers ) ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
	goto exit;
	}

	mbedtls_printf( " ok\n" );

	/*
	* 0. Load certificates
	*/
	mbedtls_printf( " . Loading the CA root certificate ..." );
	fflush( stdout );

	ret = mbedtls_x509_crt_parse( &cacert, (const unsigned char *) mbedtls_test_cas_pem,
	mbedtls_test_cas_pem_len );
	if( ret < 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_x509_crt_parse returned -0x%x\n\n", -ret );
	goto exit;
	}

	mbedtls_printf( " ok (%d skipped)\n", ret );

	/*
	* 1. Start the connection
	*/
	mbedtls_printf( " . Connecting to udp/%s/%s...", SERVER_NAME, SERVER_PORT );
	fflush( stdout );

	if( ( ret = mbedtls_net_connect( &server_fd, SERVER_ADDR,
	SERVER_PORT, MBEDTLS_NET_PROTO_UDP ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_net_connect returned %d\n\n", ret );
	goto exit;
	}

	mbedtls_printf( " ok\n" );

	/*
	* 2. Setup stuff
	*/
	mbedtls_printf( " . Setting up the DTLS structure..." );
	fflush( stdout );

	if( ( ret = mbedtls_ssl_config_defaults( &conf,
	MBEDTLS_SSL_IS_CLIENT,
	MBEDTLS_SSL_TRANSPORT_DATAGRAM,
	MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_config_defaults returned %d\n\n", ret );
	goto exit;
	}

	/* OPTIONAL is usually a bad choice for security, but makes interop easier
	* in this simplified example, in which the ca chain is hardcoded.
	* Production code should set a proper ca chain and use REQUIRED. */
	mbedtls_ssl_conf_authmode( &conf, MBEDTLS_SSL_VERIFY_OPTIONAL );
	mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );
	mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg );
	mbedtls_ssl_conf_dbg( &conf, my_debug, stdout );

	if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_setup returned %d\n\n", ret );
	goto exit;
	}

	if( ( ret = mbedtls_ssl_set_hostname( &ssl, SERVER_NAME ) ) != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_set_hostname returned %d\n\n", ret );
	goto exit;
	}

	mbedtls_ssl_set_bio( &ssl, &server_fd,
	mbedtls_net_send, mbedtls_net_recv, mbedtls_net_recv_timeout );

	mbedtls_ssl_set_timer_cb( &ssl, &timer, mbedtls_timing_set_delay,
	mbedtls_timing_get_delay );

	mbedtls_printf( " ok\n" );

	/*
	* 4. Handshake
	*/
	mbedtls_printf( " . Performing the DTLS handshake..." );
	fflush( stdout );

	do ret = mbedtls_ssl_handshake( &ssl );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret != 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_handshake returned -0x%x\n\n", -ret );
	goto exit;
	}

	mbedtls_printf( " ok\n" );

	/*
	* 5. Verify the server certificate
	*/
	mbedtls_printf( " . Verifying peer X.509 certificate..." );

	/* In real life, we would have used MBEDTLS_SSL_VERIFY_REQUIRED so that the
	* handshake would not succeed if the peer's cert is bad. Even if we used
	* MBEDTLS_SSL_VERIFY_OPTIONAL, we would bail out here if ret != 0 */
	if( ( flags = mbedtls_ssl_get_verify_result( &ssl ) ) != 0 )
	{
	char vrfy_buf[512];

	mbedtls_printf( " failed\n" );

	mbedtls_x509_crt_verify_info( vrfy_buf, sizeof( vrfy_buf ), " ! ", flags );

	mbedtls_printf( "%s\n", vrfy_buf );
	}
	else
	mbedtls_printf( " ok\n" );

	/*
	* 6. Write the echo request
	*/
	send_request:
	mbedtls_printf( " > Write to server:" );
	fflush( stdout );

	len = sizeof( MESSAGE ) - 1;

	do ret = mbedtls_ssl_write( &ssl, (unsigned char *) MESSAGE, len );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret < 0 )
	{
	mbedtls_printf( " failed\n ! mbedtls_ssl_write returned %d\n\n", ret );
	goto exit;
	}

	len = ret;
	mbedtls_printf( " %d bytes written\n\n%s\n\n", len, MESSAGE );

	/*
	* 7. Read the echo response
	*/
	mbedtls_printf( " < Read from server:" );
	fflush( stdout );

	len = sizeof( buf ) - 1;
	memset( buf, 0, sizeof( buf ) );

	do ret = mbedtls_ssl_read( &ssl, buf, len );
	while( ret == MBEDTLS_ERR_SSL_WANT_READ \|\|
	ret == MBEDTLS_ERR_SSL_WANT_WRITE );

	if( ret <= 0 )
	{
	switch( ret )
	{
	case MBEDTLS_ERR_SSL_TIMEOUT:
	mbedtls_printf( " timeout\n\n" );
	if( retry_left-- > 0 )
	goto send_request;
	goto exit;

	case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
	mbedtls_printf( " connection was closed gracefully\n" );
	ret = 0;
	goto close_notify;

	default:
	mbedtls_printf( " mbedtls_ssl_read returned -0x%x\n\n", -ret );
	goto exit;
	}
	}

	len = ret;
	mbedtls_printf( " %d bytes read\n\n%s\n\n", len, buf );

	/*
	* 8. Done, cleanly close the connection
	*/
	close_notify:
	mbedtls_printf( " . Closing the connection..." );

	/* No error checking, the connection might be closed already */
	do ret = mbedtls_ssl_close_notify( &ssl );
	while( ret == MBEDTLS_ERR_SSL_WANT_WRITE );
	ret = 0;

	mbedtls_printf( " done\n" );

	/*
	* 9. Final clean-ups and exit
	*/
	exit:

	#ifdef MBEDTLS_ERROR_C
	if( ret != 0 )
	{
	char error_buf[100];
	mbedtls_strerror( ret, error_buf, 100 );
	mbedtls_printf( "Last error was: %d - %s\n\n", ret, error_buf );
	}
	#endif

	mbedtls_net_free( &server_fd );

	mbedtls_x509_crt_free( &cacert );
	mbedtls_ssl_free( &ssl );
	mbedtls_ssl_config_free( &conf );
	mbedtls_ctr_drbg_free( &ctr_drbg );
	mbedtls_entropy_free( &entropy );

	#if defined(_WIN32)
	mbedtls_printf( " + Press Enter to exit this program.\n" );
	fflush( stdout ); getchar();
	#endif

	/* Shell can not handle large exit numbers -> 1 for errors */
	if( ret < 0 )
	ret = 1;

	return( ret );
	}
	#endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_DTLS && MBEDTLS_NET_C &&
	MBEDTLD_TIMING_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
	MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C && MBEDTLS_CERTS_C &&
	MBEDTLS_PEM_PARSE_C */