/*	$OpenBSD: server.c,v 1.8 2019/03/21 17:52:26 bluhm Exp $	*/
/*
 * Copyright (c) 2018-2019 Alexander Bluhm <bluhm@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <sys/socket.h>

#include <err.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <openssl/err.h>
#include <openssl/ssl.h>

#include "util.h"

void __dead usage(void);

void __dead
usage(void)
{
	fprintf(stderr, "usage: server [-Lsvv] [-C CA] [-c crt -k key] "
	    "[-l ciphers] [-p dhparam] [host port]\n");
	exit(2);
}

int
main(int argc, char *argv[])
{
	const SSL_METHOD *method;
	SSL_CTX *ctx;
	SSL *ssl;
	BIO *abio, *cbio;
	SSL_SESSION *session;
	int ch, error, listciphers = 0, sessionreuse = 0, verify = 0;
	char buf[256], *dhparam = NULL;
	char *ca = NULL, *crt = NULL, *key = NULL, *ciphers = NULL;
	char *host_port, *host = "127.0.0.1", *port = "0";

	while ((ch = getopt(argc, argv, "C:c:k:Ll:p:sv")) != -1) {
		switch (ch) {
		case 'C':
			ca = optarg;
			break;
		case 'c':
			crt = optarg;
			break;
		case 'k':
			key = optarg;
			break;
		case 'L':
			listciphers = 1;
			break;
		case 'l':
			ciphers = optarg;
			break;
		case 'p':
			dhparam = optarg;
			break;
		case 's':
			/* multiple reueses are possible */
			sessionreuse++;
			break;
		case 'v':
			/* use twice to force client cert */
			verify++;
			break;
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;
	if (argc == 2) {
		host = argv[0];
		port = argv[1];
	} else if (argc != 0 && !listciphers) {
		usage();
	}
	if (asprintf(&host_port, strchr(host, ':') ? "[%s]:%s" : "%s:%s",
	    host, port) == -1)
		err(1, "asprintf host port");
	if ((crt == NULL && key != NULL) || (crt != NULL && key == NULL))
		errx(1, "certificate and private key must be used together");
	if (crt == NULL && asprintf(&crt, "%s.crt", host) == -1)
		err(1, "asprintf crt");
	if (key == NULL && asprintf(&key, "%s.key", host) == -1)
		err(1, "asprintf key");

	SSL_library_init();
	SSL_load_error_strings();
	print_version();

	/* setup method and context */
#if OPENSSL_VERSION_NUMBER >= 0x1010000f
	method = TLS_server_method();
	if (method == NULL)
		err_ssl(1, "TLS_server_method");
#else
	method = SSLv23_server_method();
	if (method == NULL)
		err_ssl(1, "SSLv23_server_method");
#endif
	ctx = SSL_CTX_new(method);
	if (ctx == NULL)
		err_ssl(1, "SSL_CTX_new");

#if OPENSSL_VERSION_NUMBER >= 0x10100000
	/* needed to use DHE cipher with libressl */
	if (SSL_CTX_set_dh_auto(ctx, 1) <= 0)
		err_ssl(1, "SSL_CTX_set_dh_auto");
#endif
	/* needed to use ADH, EDH, DHE cipher with openssl */
	if (dhparam != NULL) {
		DH *dh;
		FILE *file;

		file = fopen(dhparam, "r");
		if (file == NULL)
			err(1, "fopen %s", dhparam);
		dh = PEM_read_DHparams(file, NULL, NULL, NULL);
		if (dh == NULL)
			err_ssl(1, "PEM_read_DHparams");
		if (SSL_CTX_set_tmp_dh(ctx, dh) <= 0)
			err_ssl(1, "SSL_CTX_set_tmp_dh");
		fclose(file);
	}

	/* needed when linking with OpenSSL 1.0.2p */
	if (SSL_CTX_set_ecdh_auto(ctx, 1) <= 0)
		err_ssl(1, "SSL_CTX_set_ecdh_auto");

	/* load server certificate */
	if (SSL_CTX_use_certificate_file(ctx, crt, SSL_FILETYPE_PEM) <= 0)
		err_ssl(1, "SSL_CTX_use_certificate_file");
	if (SSL_CTX_use_PrivateKey_file(ctx, key, SSL_FILETYPE_PEM) <= 0)
		err_ssl(1, "SSL_CTX_use_PrivateKey_file");
	if (SSL_CTX_check_private_key(ctx) <= 0)
		err_ssl(1, "SSL_CTX_check_private_key");

	/* request client certificate and verify it */
	if (ca != NULL) {
		STACK_OF(X509_NAME) *x509stack;

		x509stack = SSL_load_client_CA_file(ca);
		if (x509stack == NULL)
			err_ssl(1, "SSL_load_client_CA_file");
		SSL_CTX_set_client_CA_list(ctx, x509stack);
		if (SSL_CTX_load_verify_locations(ctx, ca, NULL) <= 0)
			err_ssl(1, "SSL_CTX_load_verify_locations");
	}
	SSL_CTX_set_verify(ctx,
	    verify == 0 ?  SSL_VERIFY_NONE :
	    verify == 1 ?  SSL_VERIFY_PEER :
	    SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT,
	    verify_callback);

	if (sessionreuse) {
		uint32_t context;

		SSL_CTX_set_session_cache_mode(ctx, SSL_SESS_CACHE_SERVER);
		context = arc4random();
		if (SSL_CTX_set_session_id_context(ctx,
		    (unsigned char *)&context, sizeof(context)) <= 0)
			err_ssl(1, "SSL_CTX_set_session_id_context");
	}

	if (ciphers) {
		if (SSL_CTX_set_cipher_list(ctx, ciphers) <= 0)
			err_ssl(1, "SSL_CTX_set_cipher_list");
	}

	if (listciphers) {
		ssl = SSL_new(ctx);
		if (ssl == NULL)
			err_ssl(1, "SSL_new");
		print_ciphers(SSL_get_ciphers(ssl));
		return 0;
	}

	/* setup bio for socket operations */
	abio = BIO_new_accept(host_port);
	if (abio == NULL)
		err_ssl(1, "BIO_new_accept");

	/* bind, listen */
	if (BIO_do_accept(abio) <= 0)
		err_ssl(1, "BIO_do_accept setup");
	printf("listen ");
	print_sockname(abio);

	/* fork to background and set timeout */
	if (daemon(1, 1) == -1)
		err(1, "daemon");
	if ((int)alarm(10) == -1)
		err(1, "alarm");

	do {
		/* accept connection */
		if (BIO_do_accept(abio) <= 0)
			err_ssl(1, "BIO_do_accept wait");
		cbio = BIO_pop(abio);
		printf("accept ");
		print_sockname(cbio);
		printf("accept ");
		print_peername(cbio);

		/* do ssl server handshake */
		ssl = SSL_new(ctx);
		if (ssl == NULL)
			err_ssl(1, "SSL_new");
		SSL_set_bio(ssl, cbio, cbio);
		if ((error = SSL_accept(ssl)) <= 0)
			err_ssl(1, "SSL_accept %d", error);
		printf("session %d: %s\n", sessionreuse,
		    SSL_session_reused(ssl) ? "reuse" : "new");
		if (fflush(stdout) != 0)
			err(1, "fflush stdout");


		/* print session statistics */
		session = SSL_get_session(ssl);
		if (session == NULL)
			err_ssl(1, "SSL_get_session");
		if (SSL_SESSION_print_fp(stdout, session) <= 0)
			err_ssl(1, "SSL_SESSION_print_fp");

		/* write server greeting and read client hello over TLS */
		strlcpy(buf, "greeting\n", sizeof(buf));
		printf(">>> %s", buf);
		if (fflush(stdout) != 0)
			err(1, "fflush stdout");
		if ((error = SSL_write(ssl, buf, 9)) <= 0)
			err_ssl(1, "SSL_write %d", error);
		if (error != 9)
			errx(1, "write not 9 bytes greeting: %d", error);
		if ((error = SSL_read(ssl, buf, 6)) <= 0)
			err_ssl(1, "SSL_read %d", error);
		if (error != 6)
			errx(1, "read not 6 bytes hello: %d", error);
		buf[6] = '\0';
		printf("<<< %s", buf);
		if (fflush(stdout) != 0)
			err(1, "fflush stdout");

		/* shutdown connection */
		if ((error = SSL_shutdown(ssl)) < 0)
			err_ssl(1, "SSL_shutdown unidirectional %d", error);
		if (error <= 0) {
			if ((error = SSL_shutdown(ssl)) <= 0)
				err_ssl(1, "SSL_shutdown bidirectional %d",
				    error);
		}

		SSL_free(ssl);
	} while (sessionreuse--);

	SSL_CTX_free(ctx);

	printf("success\n");

	return 0;
}