dtls_client.c

/*
 *  Simple DTLS client demonstration program
 *
 *  Copyright The Mbed TLS Contributors
 *  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.
 */

#include "mbedtls/build_info.h"

#include "mbedtls/platform.h"

#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_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_PEM_PARSE_C not defined.\n");
    mbedtls_exit(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/timing.h"
#include "test/certs.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",
                       (unsigned int) -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);
    mbedtls_ssl_conf_read_timeout(&conf, READ_TIMEOUT_MS);

    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",
                       (unsigned int) -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) {
#if !defined(MBEDTLS_X509_REMOVE_INFO)
        char vrfy_buf[512];
#endif

        mbedtls_printf(" failed\n");

#if !defined(MBEDTLS_X509_REMOVE_INFO)
        mbedtls_x509_crt_verify_info(vrfy_buf, sizeof(vrfy_buf), "  ! ", flags);

        mbedtls_printf("%s\n", vrfy_buf);
#endif
    } 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", (unsigned int) -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);

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

    mbedtls_exit(ret);
}
#endif /* MBEDTLS_SSL_CLI_C && MBEDTLS_SSL_PROTO_DTLS && MBEDTLS_NET_C &&
          MBEDTLS_TIMING_C && MBEDTLS_ENTROPY_C && MBEDTLS_CTR_DRBG_C &&
          MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C && MBEDTLS_PEM_PARSE_C */