I had to make some minor changes to get the mbedtls example working.
The example can be found on the github.
I commented out a couple of the includes, build_info and test/certs.h, and also changed the example to use my own self signed certificate rather than using the embedded test certificates.
The command to generate a self signed cert:
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout selfsigned.key -out selfsigned.crt
And to compile the program:
gcc ssl_server.c -o ssl_server -lmbedtls -lmbedx509 -lmbedcrypto
Once compiled, we can run the server:
./ssl_server
and finally test with curl:
curl -k https://127.0.0.1
The -k will let curl ignore the ssl validation.
The full modified example is below. The key lines that I changed are ones where we parse the certificate and the keyfile from paths rather than having them embeded.
/*
* SSL server demonstration program
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
//#include "mbedtls/build_info.h"
#include "mbedtls/platform.h"
#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_PEM_PARSE_C) || \
!defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_SSL_TLS_C) || \
!defined(MBEDTLS_SSL_SRV_C) || !defined(MBEDTLS_NET_C) || \
!defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_CTR_DRBG_C) || \
!defined(MBEDTLS_X509_CRT_PARSE_C) || !defined(MBEDTLS_FS_IO)
int main(void)
{
mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C "
"and/or MBEDTLS_SSL_TLS_C and/or MBEDTLS_SSL_SRV_C and/or "
"MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
"MBEDTLS_CTR_DRBG_C and/or MBEDTLS_X509_CRT_PARSE_C "
"and/or MBEDTLS_PEM_PARSE_C not defined.\n");
mbedtls_exit(0);
}
#else
#include <stdlib.h>
#include <string.h>
#if defined(_WIN32)
#include <windows.h>
#endif
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/x509.h"
#include "mbedtls/ssl.h"
#include "mbedtls/net_sockets.h"
#include "mbedtls/error.h"
#include "mbedtls/debug.h"
//#include "test/certs.h"
#if defined(MBEDTLS_SSL_CACHE_C)
#include "mbedtls/ssl_cache.h"
#endif
#define HTTP_RESPONSE \
"HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n" \
"<h2>Mbed TLS Test Server</h2>\r\n" \
"<p>Successful connection using: %s</p>\r\n"
#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(void)
{
int ret, len;
mbedtls_net_context listen_fd, client_fd;
unsigned char buf[1024];
const char *pers = "ssl_server";
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
mbedtls_ssl_context ssl;
mbedtls_ssl_config conf;
mbedtls_x509_crt srvcert;
mbedtls_pk_context pkey;
#if defined(MBEDTLS_SSL_CACHE_C)
mbedtls_ssl_cache_context cache;
#endif
mbedtls_net_init(&listen_fd);
mbedtls_net_init(&client_fd);
mbedtls_ssl_init(&ssl);
mbedtls_ssl_config_init(&conf);
#if defined(MBEDTLS_SSL_CACHE_C)
mbedtls_ssl_cache_init(&cache);
#endif
mbedtls_x509_crt_init(&srvcert);
mbedtls_pk_init(&pkey);
mbedtls_entropy_init(&entropy);
mbedtls_ctr_drbg_init(&ctr_drbg);
#if defined(MBEDTLS_USE_PSA_CRYPTO)
psa_status_t status = psa_crypto_init();
if (status != PSA_SUCCESS) {
mbedtls_fprintf(stderr, "Failed to initialize PSA Crypto implementation: %d\n",
(int) status);
ret = MBEDTLS_ERR_SSL_HW_ACCEL_FAILED;
goto exit;
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */
#if defined(MBEDTLS_DEBUG_C)
mbedtls_debug_set_threshold(DEBUG_LEVEL);
#endif
/*
* 1. Seed the RNG
*/
mbedtls_printf(" . Seeding the random number generator...");
fflush(stdout);
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");
/*
* 2. Load the certificates and private RSA key
*/
mbedtls_printf("\n . Loading the server cert. and key...");
fflush(stdout);
/*
* This demonstration program uses embedded test certificates.
* Instead, you may want to use mbedtls_x509_crt_parse_file() to read the
* server and CA certificates, as well as mbedtls_pk_parse_keyfile().
*/
char *mbedtls_test_srv_crt = "selfsigned.crt";
char *mbedtls_test_srv_key = "selfsigned.key";
ret = mbedtls_x509_crt_parse_file(&srvcert, (const unsigned char *) mbedtls_test_srv_crt);
if (ret != 0) {
mbedtls_printf(" failed\n ! mbedtls_x509_crt_parse returned %d\n\n", ret);
goto exit;
}
ret = mbedtls_pk_parse_keyfile(&pkey, (const unsigned char *) mbedtls_test_srv_key, NULL);
if (ret != 0) {
mbedtls_printf(" failed\n ! mbedtls_pk_parse_key returned %d\n\n", ret);
goto exit;
}
mbedtls_printf(" ok\n");
/*
* 3. Setup the listening TCP socket
*/
mbedtls_printf(" . Bind on https://localhost:4433/ ...");
fflush(stdout);
if ((ret = mbedtls_net_bind(&listen_fd, NULL, "4433", MBEDTLS_NET_PROTO_TCP)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_net_bind returned %d\n\n", ret);
goto exit;
}
mbedtls_printf(" ok\n");
/*
* 4. Setup stuff
*/
mbedtls_printf(" . Setting up the SSL data....");
fflush(stdout);
if ((ret = mbedtls_ssl_config_defaults(&conf,
MBEDTLS_SSL_IS_SERVER,
MBEDTLS_SSL_TRANSPORT_STREAM,
MBEDTLS_SSL_PRESET_DEFAULT)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_ssl_config_defaults returned %d\n\n", ret);
goto exit;
}
mbedtls_ssl_conf_rng(&conf, mbedtls_ctr_drbg_random, &ctr_drbg);
mbedtls_ssl_conf_dbg(&conf, my_debug, stdout);
#if defined(MBEDTLS_SSL_CACHE_C)
mbedtls_ssl_conf_session_cache(&conf, &cache,
mbedtls_ssl_cache_get,
mbedtls_ssl_cache_set);
#endif
mbedtls_ssl_conf_ca_chain(&conf, srvcert.next, NULL);
if ((ret = mbedtls_ssl_conf_own_cert(&conf, &srvcert, &pkey)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_ssl_conf_own_cert returned %d\n\n", ret);
goto exit;
}
if ((ret = mbedtls_ssl_setup(&ssl, &conf)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_ssl_setup returned %d\n\n", ret);
goto exit;
}
mbedtls_printf(" ok\n");
reset:
#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(&client_fd);
mbedtls_ssl_session_reset(&ssl);
/*
* 3. Wait until a client connects
*/
mbedtls_printf(" . Waiting for a remote connection ...");
fflush(stdout);
if ((ret = mbedtls_net_accept(&listen_fd, &client_fd,
NULL, 0, NULL)) != 0) {
mbedtls_printf(" failed\n ! mbedtls_net_accept returned %d\n\n", ret);
goto exit;
}
mbedtls_ssl_set_bio(&ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL);
mbedtls_printf(" ok\n");
/*
* 5. Handshake
*/
mbedtls_printf(" . Performing the SSL/TLS handshake...");
fflush(stdout);
while ((ret = mbedtls_ssl_handshake(&ssl)) != 0) {
if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
mbedtls_printf(" failed\n ! mbedtls_ssl_handshake returned %d\n\n", ret);
goto reset;
}
}
mbedtls_printf(" ok\n");
/*
* 6. Read the HTTP Request
*/
mbedtls_printf(" < Read from client:");
fflush(stdout);
do {
len = sizeof(buf) - 1;
memset(buf, 0, sizeof(buf));
ret = mbedtls_ssl_read(&ssl, buf, len);
if (ret == MBEDTLS_ERR_SSL_WANT_READ || ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
continue;
}
if (ret <= 0) {
switch (ret) {
case MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY:
mbedtls_printf(" connection was closed gracefully\n");
break;
case MBEDTLS_ERR_NET_CONN_RESET:
mbedtls_printf(" connection was reset by peer\n");
break;
default:
mbedtls_printf(" mbedtls_ssl_read returned -0x%x\n", (unsigned int) -ret);
break;
}
break;
}
len = ret;
mbedtls_printf(" %d bytes read\n\n%s", len, (char *) buf);
if (ret > 0) {
break;
}
} while (1);
/*
* 7. Write the 200 Response
*/
mbedtls_printf(" > Write to client:");
fflush(stdout);
len = sprintf((char *) buf, HTTP_RESPONSE,
mbedtls_ssl_get_ciphersuite(&ssl));
while ((ret = mbedtls_ssl_write(&ssl, buf, len)) <= 0) {
if (ret == MBEDTLS_ERR_NET_CONN_RESET) {
mbedtls_printf(" failed\n ! peer closed the connection\n\n");
goto reset;
}
if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
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", len, (char *) buf);
mbedtls_printf(" . Closing the connection...");
while ((ret = mbedtls_ssl_close_notify(&ssl)) < 0) {
if (ret != MBEDTLS_ERR_SSL_WANT_READ &&
ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
mbedtls_printf(" failed\n ! mbedtls_ssl_close_notify returned %d\n\n", ret);
goto reset;
}
}
mbedtls_printf(" ok\n");
ret = 0;
goto reset;
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(&client_fd);
mbedtls_net_free(&listen_fd);
mbedtls_x509_crt_free(&srvcert);
mbedtls_pk_free(&pkey);
mbedtls_ssl_free(&ssl);
mbedtls_ssl_config_free(&conf);
#if defined(MBEDTLS_SSL_CACHE_C)
mbedtls_ssl_cache_free(&cache);
#endif
mbedtls_ctr_drbg_free(&ctr_drbg);
mbedtls_entropy_free(&entropy);
#if defined(MBEDTLS_USE_PSA_CRYPTO)
mbedtls_psa_crypto_free();
#endif /* MBEDTLS_USE_PSA_CRYPTO */
mbedtls_exit(ret);
}
#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C &&
MBEDTLS_SSL_TLS_C && MBEDTLS_SSL_SRV_C && MBEDTLS_NET_C &&
MBEDTLS_RSA_C && MBEDTLS_CTR_DRBG_C && MBEDTLS_X509_CRT_PARSE_C
&& MBEDTLS_FS_IO && MBEDTLS_PEM_PARSE_C */