/*
 *  Simple DTLS server program that does the same thing as echo-server but
 *  over encrypted UDP link.
 *
 *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
 *  Copyright (C) 2017 Intel Corporation
 *  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 <stdbool.h>
#include <unistd.h>
#include <errno.h>

#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
#define mbedtls_time_t     time_t
#endif

#if !defined(MBEDTLS_SSL_SRV_C) || !defined(MBEDTLS_SSL_PROTO_DTLS) ||	\
	!defined(MBEDTLS_SSL_COOKIE_C) || !defined(MBEDTLS_NET_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) ||	\
	!defined(MBEDTLS_TIMING_C)

int main(void)
{
	printf("MBEDTLS_SSL_SRV_C and/or MBEDTLS_SSL_PROTO_DTLS and/or "
	       "MBEDTLS_SSL_COOKIE_C and/or MBEDTLS_NET_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 and/or "
	       "MBEDTLS_TIMING_C not defined.\n");
	return(0);
}
#else

#if defined(_WIN32)
#include <windows.h>
#endif

#include <string.h>
#include <stdlib.h>
#include <stdio.h>

#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/certs.h"
#include "mbedtls/x509.h"
#include "mbedtls/ssl.h"
#include "mbedtls/ssl_cookie.h"
#include "mbedtls/net_sockets.h"
#include "mbedtls/error.h"
#include "mbedtls/debug.h"
#include "mbedtls/timing.h"

#if defined(MBEDTLS_SSL_CACHE_C)
#include "mbedtls/ssl_cache.h"
#endif

#define READ_TIMEOUT_MS 10000   /* 5 seconds */
#define DEBUG_LEVEL 0

extern int optind, opterr, optopt;
extern char *optarg;

static bool debug;
static bool help;

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, c;
	mbedtls_net_context listen_fd, client_fd;
	unsigned char buf[1024];
	const char *pers = "dtls_server";
	unsigned char client_ip[16] = { 0 };
	size_t cliip_len;
	mbedtls_ssl_cookie_ctx cookie_ctx;

	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;
	mbedtls_timing_delay_context timer;
#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_cache_context cache;
#endif

#define LISTEN_PORT "4242"
	const char *listen_port = LISTEN_PORT;

#define SRV_CERT_FILE "echo-apps-cert.pem"
	const char *srv_cert_file = SRV_CERT_FILE;

#define SRV_KEY_FILE "echo-apps-key.pem"
	const char *srv_key_file = SRV_KEY_FILE;

	opterr = 0;

	while ((c = getopt(argc, argv, "c:k:p:Dh")) != -1) {
		switch (c) {
		case 'c':
			srv_cert_file = optarg;
			break;
		case 'k':
			srv_key_file = optarg;
			break;
		case 'p':
			listen_port = optarg;
			break;
		case 'D':
			debug = true;
			break;
		case 'h':
			help = true;
			break;
		}
	}

	if (help) {
		printf("usage: %s [-c <server cert file>] [-k <cert key file>] "
		       "[-p <port>] [-D]\n", argv[0]);
		printf("-c Server cert file (default is %s)\n", SRV_CERT_FILE);
		printf("-k Server key file (default is %s)\n", SRV_KEY_FILE);
		printf("-p Port number to use (default is %s)\n", LISTEN_PORT);
		printf("-D Activate debugging.\n");
		exit(-EINVAL);
	}

	mbedtls_net_init(&listen_fd);
	mbedtls_net_init(&client_fd);
	mbedtls_ssl_init(&ssl);
	mbedtls_ssl_config_init(&conf);
	mbedtls_ssl_cookie_init(&cookie_ctx);
#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_DEBUG_C)
	mbedtls_debug_set_threshold(DEBUG_LEVEL);
#endif

	/*
	 * 1. Load the certificates and private RSA key
	 */
	printf("\n  . Loading the server cert. and key...");
	fflush(stdout);

	ret = mbedtls_x509_crt_parse_file(&srvcert, srv_cert_file);
	if (ret != 0) {
		printf(" failed\n  !  mbedtls_x509_crt_parse returned %d\n\n",
		       ret);
		goto exit;
	}

	ret =  mbedtls_pk_parse_keyfile(&pkey, srv_key_file, NULL);
	if (ret != 0) {
		printf(" failed\n  !  mbedtls_pk_parse_keyfile returned %d\n\n",
		       ret);
		goto exit;
	}

	printf(" ok\n");

	/*
	 * 2. Setup the "listening" UDP socket
	 */
	printf("  . Bind on udp/*/%s ...", listen_port);
	fflush(stdout);

	if ((ret = mbedtls_net_bind(&listen_fd, NULL, listen_port,
				    MBEDTLS_NET_PROTO_UDP)) != 0) {
		printf(" failed\n  ! mbedtls_net_bind returned %d\n\n", ret);
		goto exit;
	}

	printf(" ok\n");

	/*
	 * 3. Seed the RNG
	 */
	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) {
		printf(" failed\n  ! mbedtls_ctr_drbg_seed returned %d\n", ret);
		goto exit;
	}

	printf(" ok\n");

	/*
	 * 4. Setup stuff
	 */
	printf("  . Setting up the DTLS data...");
	fflush(stdout);

	if ((ret = mbedtls_ssl_config_defaults(&conf,
					       MBEDTLS_SSL_IS_SERVER,
					       MBEDTLS_SSL_TRANSPORT_DATAGRAM,
					       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) {
		printf(" failed\n  ! mbedtls_ssl_conf_own_cert "
		       "returned %d\n\n", ret);
		goto exit;
	}

	if ((ret = mbedtls_ssl_cookie_setup(&cookie_ctx,
					    mbedtls_ctr_drbg_random,
					    &ctr_drbg)) != 0) {
		printf(" failed\n  ! mbedtls_ssl_cookie_setup returned %d\n\n",
		       ret);
		goto exit;
	}

	mbedtls_ssl_conf_dtls_cookies(&conf, mbedtls_ssl_cookie_write,
				      mbedtls_ssl_cookie_check, &cookie_ctx);

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

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

	printf(" ok\n");

reset:
#ifdef MBEDTLS_ERROR_C
	if (ret != 0) {
		char error_buf[100];
		mbedtls_strerror(ret, error_buf, 100);
		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
	 */
	printf("  . Waiting for a remote connection ...");
	fflush(stdout);

	if ((ret = mbedtls_net_accept(&listen_fd, &client_fd,
				      client_ip, sizeof(client_ip),
				      &cliip_len)) != 0) {
		printf(" failed\n  ! mbedtls_net_accept returned %d\n\n", ret);
		goto exit;
	}

	/* For HelloVerifyRequest cookies */
	if ((ret = mbedtls_ssl_set_client_transport_id(&ssl,
						       client_ip,
						       cliip_len)) != 0) {
		printf(" failed\n  ! "
		       "mbedtls_ssl_set_client_transport_id() "
		       "returned -0x%x\n\n", -ret);
		goto exit;
	}

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

	printf(" ok\n");

	/*
	 * 5. Handshake
	 */
	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 == MBEDTLS_ERR_SSL_HELLO_VERIFY_REQUIRED) {
		printf(" hello verification requested\n");
		ret = 0;
		goto reset;
	}
	else if (ret != 0)
	{
		printf(" failed\n  ! mbedtls_ssl_handshake returned -0x%x\n\n",
		       -ret);
		goto reset;
	}

	printf(" ok\n");

again:
	/*
	 * 6. Read the echo Request
	 */
	printf("  < Read from client:");
	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:
			printf(" timeout\n\n");
			goto reset;

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

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

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

	/*
	 * 7. Write the 200 Response
	 */
	printf("  > Write to client:");
	fflush(stdout);

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

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

	len = ret;
	printf(" %d bytes written\n\n%s\n\n", len, buf);

	goto again;

	/*
	 * 8. Done, cleanly close the connection
	 */
close_notify:
	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;

	printf(" done\n");

	goto reset;

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

#ifdef MBEDTLS_ERROR_C
	if (ret != 0) {
		char error_buf[100];
		mbedtls_strerror(ret, error_buf, 100);
		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);
	mbedtls_ssl_cookie_free(&cookie_ctx);
#if defined(MBEDTLS_SSL_CACHE_C)
	mbedtls_ssl_cache_free(&cache);
#endif
	mbedtls_ctr_drbg_free(&ctr_drbg);
	mbedtls_entropy_free(&entropy);

#if defined(_WIN32)
	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_SRV_C && MBEDTLS_SSL_PROTO_DTLS &&
          MBEDTLS_SSL_COOKIE_C && MBEDTLS_NET_C && MBEDTLS_ENTROPY_C &&
          MBEDTLS_CTR_DRBG_C && MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_RSA_C
          && MBEDTLS_CERTS_C && MBEDTLS_PEM_PARSE_C && MBEDTLS_TIMING_C */