/*
 * Copyright (C) 2013 Nikos Mavrogiannopoulos
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netdb.h>
#include <signal.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <cloexec.h>

#include <gnutls/x509.h>
#include <tlslib.h>
#include "ipc.h"

#include <main.h>
#include <vpn.h>
#include <cookies.h>
#include <tun.h>
#include <list.h>

int syslog_open = 0;
static unsigned int terminate = 0;
static unsigned int need_maintainance = 0;
static unsigned int need_children_cleanup = 0;

static void tls_log_func(int level, const char *str)
{
	syslog(LOG_DEBUG, "TLS[<%d>]: %s", level, str);
}

/* Returns 0 on success or negative value on error.
 */
static int
listen_ports(struct cfg_st* config, struct listen_list_st *list, const char *node,
	     int listen_port, int socktype)
{
	struct addrinfo hints, *res, *ptr;
	char portname[6];
	int s, y;
	char buf[512];
	struct listen_list_st *tmp;

	INIT_LIST_HEAD(&list->list);

	snprintf(portname, sizeof(portname), "%d", listen_port);

	memset(&hints, 0, sizeof(hints));
	hints.ai_socktype = socktype;
	hints.ai_flags = AI_PASSIVE
#ifdef AI_ADDRCONFIG
	    | AI_ADDRCONFIG
#endif
	    ;

	s = getaddrinfo(node, portname, &hints, &res);
	if (s != 0) {
		fprintf(stderr, "getaddrinfo() failed: %s\n",
			gai_strerror(s));
		return -1;
	}

	for (ptr = res; ptr != NULL; ptr = ptr->ai_next) {
#ifndef HAVE_IPV6
		if (ptr->ai_family != AF_INET)
			continue;
#endif
		if (config->foreground != 0)
			fprintf(stderr, "listening on %s...\n",
				human_addr(ptr->ai_addr, ptr->ai_addrlen,
					   buf, sizeof(buf)));

		s = socket(ptr->ai_family, ptr->ai_socktype,
			   ptr->ai_protocol);
		if (s < 0) {
			perror("socket() failed");
			continue;
		}
		

#if defined(HAVE_IPV6) && !defined(_WIN32)
		if (ptr->ai_family == AF_INET6) {
			y = 1;
			/* avoid listen on ipv6 addresses failing
			 * because already listening on ipv4 addresses: */
			setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY,
				   (const void *) &y, sizeof(y));
		}
#endif

		if (socktype == SOCK_STREAM) {
			y = 1;
			if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
				       (const void *) &y, sizeof(y)) < 0) {
				perror("setsockopt() failed");
				close(s);
				continue;
			}
		} else {
#if defined(IP_DONTFRAG)
			y = 1;
			if (setsockopt(s, IPPROTO_IP, IP_DONTFRAG,
				       (const void *) &y, sizeof(y)) < 0)
				perror("setsockopt(IP_DF) failed");
#elif defined(IP_MTU_DISCOVER)
			y = IP_PMTUDISC_DO;
			if (setsockopt(s, IPPROTO_IP, IP_MTU_DISCOVER,
				       (const void *) &y, sizeof(y)) < 0)
				perror("setsockopt(IP_DF) failed");
#endif
		}

		set_cloexec_flag (s, 1);

		if (bind(s, ptr->ai_addr, ptr->ai_addrlen) < 0) {
			perror("bind() failed");
			close(s);
			continue;
		}

		if (socktype == SOCK_STREAM) {
			if (listen(s, 10) < 0) {
				perror("listen() failed");
				exit(1);
			}
		}

		tmp = calloc(1, sizeof(struct listen_list_st));
		tmp->fd = s;
		list_add(&(tmp->list), &(list->list));
	}

	fflush(stderr);
	freeaddrinfo(res);

	return 0;
}

static void cleanup_children(main_server_st *s)
{
int status;
pid_t pid;

	while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
		if (WEXITSTATUS(status) != 0 ||
			(WIFSIGNALED(status) && WTERMSIG(status) == SIGSEGV)) {
			if (WIFSIGNALED(status))
				syslog(LOG_ERR, "Child %u died with sigsegv\n", (unsigned)pid);
		}
	}
	need_children_cleanup = 0;
}

static void handle_children(int signo)
{
	need_children_cleanup = 1;
}

static void handle_alarm(int signo)
{
	need_maintainance = 1;
}


static void tls_audit_log_func(gnutls_session_t session, const char *str)
{
worker_st * ws;

	if (session == NULL)
		syslog(LOG_AUTH, "Warning: %s", str);
	else {
		ws = gnutls_session_get_ptr(session);
		
		oclog(ws, LOG_ERR, "Warning: %s", str);
	}
}

static int verify_certificate_cb(gnutls_session_t session)
{
	unsigned int status;
	int ret;
	worker_st * ws;

	ws = gnutls_session_get_ptr(session);
	if (ws == NULL) {
		syslog(LOG_ERR, "%s:%d: Could not obtain worker state.", __func__, __LINE__);
		return -1;
	}

	/* This verification function uses the trusted CAs in the credentials
	 * structure. So you must have installed one or more CA certificates.
	 */
	ret = gnutls_certificate_verify_peers2(session, &status);
	if (ret < 0) {
		oclog(ws, LOG_ERR, "Error verifying client certificate");
		return GNUTLS_E_CERTIFICATE_ERROR;
	}

	if (status != 0) {
#if GNUTLS_VERSION_NUMBER > 0x030106
		type = gnutls_certificate_type_get(session);

		ret =
		    gnutls_certificate_verification_status_print(status, type,
							 &out, 0);
		if (ret < 0)
			return GNUTLS_E_CERTIFICATE_ERROR;

		oclog(ws, LOG_INFO, "Client certificate verification failed: %s", out.data);

		gnutls_free(out.data);
#else
		oclog(ws, LOG_INFO, "Client certificate verification failed.");
#endif

		return GNUTLS_E_CERTIFICATE_ERROR;
	} else {
		oclog(ws, LOG_INFO, "Client certificate verification succeeded");
	}

	/* notify gnutls to continue handshake normally */
	return 0;
}

static void drop_privileges(struct cfg_st *config)
{
	int ret, e;

	if (config->chroot_dir) {
		ret = chroot(config->chroot_dir);
		if (ret != 0) {
			e = errno;
			syslog(LOG_ERR, "Cannot chroot to %s: %s", config->chroot_dir, strerror(e));
			exit(1);
		}
	}

	if (config->gid != -1 && (getgid() == 0 || getegid() == 0)) {
		ret = setgid(config->gid);
		if (ret < 0) {
			e = errno;
			syslog(LOG_ERR, "Cannot set gid to %d: %s\n",
			       (int) config->gid, strerror(e));
			exit(1);

		}
	}

	if (config->uid != -1 && (getuid() == 0 || geteuid() == 0)) {
		ret = setuid(config->uid);
		if (ret < 0) {
			e = errno;
			syslog(LOG_ERR, "Cannot set uid to %d: %s\n",
			       (int) config->uid, strerror(e));
			exit(1);

		}
	}
}

/* clears the server llist and clist. To be used after fork() */
void clear_lists(main_server_st *s)
{
	struct list_head *cq;
	struct list_head *pos;
	struct listen_list_st *ltmp;
	struct proc_list_st *ctmp;

	list_for_each_safe(pos, cq, &s->llist->list) {
		ltmp = list_entry(pos, struct listen_list_st, list);
		close(ltmp->fd);
		list_del(&ltmp->list);
	}

	list_for_each_safe(pos, cq, &s->clist->list) {
		ctmp = list_entry(pos, struct proc_list_st, list);
		if (ctmp->fd >= 0)
			close(ctmp->fd);
		list_del(&ctmp->list);
	}
	
	tls_cache_deinit(s->tls_db);
}

static void kill_children(struct proc_list_st* clist)
{
	struct list_head *pos;
	struct proc_list_st *ctmp;

	list_for_each(pos, &clist->list) {
		ctmp = list_entry(pos, struct proc_list_st, list);
		if (ctmp->pid != -1)
			kill(ctmp->pid, SIGTERM);
	}
}

static void remove_proc(struct proc_list_st *ctmp)
{
	/* close the intercomm fd */
	if (ctmp->fd >= 0)
		close(ctmp->fd);
	ctmp->fd = -1;

	ctmp->pid = -1;
	if (ctmp->lease)
		ctmp->lease->in_use = 0;
	list_del(&ctmp->list);
}

static void handle_term(int signo)
{
	/* kill all children */
	terminate = 1;
}

int main(int argc, char** argv)
{
	int fd, pid, e;
	struct tls_st creds;
	struct listen_list_st llist;
	struct proc_list_st clist;
	struct listen_list_st *ltmp;
	struct proc_list_st *ctmp;
	struct list_head *cq;
	struct list_head *pos;
	struct tun_st tun;
	fd_set rd;
	int val, n = 0, ret;
	struct timeval tv;
	int cmd_fd[2];
	struct worker_st ws;
	struct cfg_st config;
	unsigned active_clients = 0;
	main_server_st s;
	tls_cache_db_st* tls_db;
	
	INIT_LIST_HEAD(&clist.list);
	tun_st_init(&tun);
	tls_cache_init(&config, &tls_db);

	signal(SIGINT, handle_term);
	signal(SIGTERM, handle_term);
	signal(SIGPIPE, SIG_IGN);
	signal(SIGHUP, SIG_IGN);
	signal(SIGCHLD, handle_children);
	signal(SIGALRM, handle_alarm);

	/* load configuration */
	ret = cmd_parser(argc, argv, &config);
	if (ret < 0) {
		fprintf(stderr, "Error in arguments\n");
		exit(1);
	}

	if (getuid() != 0) {
		fprintf(stderr, "This server requires root access to operate.\n");
		exit(1);
	}
	
	s.config = &config;
	s.tun = &tun;
	s.tls_db = tls_db;
	s.llist = &llist;
	s.clist = &clist;
	
	/* Listen to network ports */
	ret = listen_ports(&config, &llist, config.name, config.port, SOCK_STREAM);
	if (ret < 0) {
		fprintf(stderr, "Cannot listen to specified ports\n");
		exit(1);
	}

	/* Initialize GnuTLS */
	gnutls_global_set_audit_log_function(tls_audit_log_func);
	if (config.tls_debug) {
		gnutls_global_set_log_function(tls_log_func);
		gnutls_global_set_log_level(9);
	}

	ret = gnutls_global_init();
	GNUTLS_FATAL_ERR(ret);

	ret = gnutls_certificate_allocate_credentials(&creds.xcred);
	GNUTLS_FATAL_ERR(ret);

#warning Handle keys using the communication interface
	ret =
	    gnutls_certificate_set_x509_key_file(creds.xcred, config.cert,
						 config.key,
						 GNUTLS_X509_FMT_PEM);
	if (ret < 0) {
		fprintf(stderr, "Error setting the certificate (%s) or key (%s) files.\n",
			config.cert, config.key);
		exit(1);
	}

	if (config.ca != NULL) {
		ret =
		    gnutls_certificate_set_x509_trust_file(creds.xcred,
							   config.ca,
							   GNUTLS_X509_FMT_PEM);
		if (ret < 0) {
			fprintf(stderr, "Error setting the CA (%s) file.\n",
				config.ca);
			exit(1);
		}

		printf("Processed %d CA certificate(s).\n", ret);
	}

	if (config.crl != NULL) {
		ret =
		    gnutls_certificate_set_x509_crl_file(creds.xcred,
							 config.crl,
							 GNUTLS_X509_FMT_PEM);
		GNUTLS_FATAL_ERR(ret);
	}


	if (config.cert_req != GNUTLS_CERT_IGNORE) {
		gnutls_certificate_set_verify_function(creds.xcred,
						       verify_certificate_cb);
	}

	ret = gnutls_priority_init(&creds.cprio, config.priorities, NULL);
	GNUTLS_FATAL_ERR(ret);

	memset(&ws, 0, sizeof(ws));
	
	if (config.foreground == 0)
		daemon(0, 0);

#define MAINTAINANCE_TIME (config.cookie_validity + 300)
	alarm(MAINTAINANCE_TIME);
	openlog("ocserv", LOG_PID|LOG_NDELAY, LOG_LOCAL0);
	syslog_open = 1;

	for (;;) {
		if (terminate != 0) {
			kill_children(&clist);
			sleep(1);
			exit(0);
		}

		FD_ZERO(&rd);

		list_for_each(pos, &llist.list) {
			ltmp = list_entry(pos, struct listen_list_st, list);

			val = fcntl(ltmp->fd, F_GETFL, 0);
			if ((val == -1)
			    || (fcntl(ltmp->fd, F_SETFL, val | O_NONBLOCK) <
				0)) {
				perror("fcntl()");
				exit(1);
			}

			FD_SET(ltmp->fd, &rd);
			n = MAX(n, ltmp->fd);
		}

		list_for_each(pos, &clist.list) {
			ctmp = list_entry(pos, struct proc_list_st, list);

			FD_SET(ctmp->fd, &rd);
			n = MAX(n, ctmp->fd);
		}

		tv.tv_usec = 0;
		tv.tv_sec = 10;
		ret = select(n + 1, &rd, NULL, NULL, &tv);
		if (ret == -1 && errno == EINTR)
			continue;

		if (ret < 0) {
			e = errno;
			syslog(LOG_ERR, "Error in select(): %s",
			       strerror(e));
			exit(1);
		}

		/* Check for new connections to accept */
		list_for_each(pos, &llist.list) {
			ltmp = list_entry(pos, struct listen_list_st, list);
			if (FD_ISSET(ltmp->fd, &rd)) {
				ws.remote_addr_len = sizeof(ws.remote_addr);
				fd = accept(ltmp->fd, (void*)&ws.remote_addr, &ws.remote_addr_len);
				if (fd < 0) {
					syslog(LOG_ERR,
					       "Error in accept(): %s",
					       strerror(errno));
					continue;
				}
				set_cloexec_flag (fd, 1);
				
				if (config.max_clients > 0 && active_clients >= config.max_clients) {
					close(fd);
					syslog(LOG_INFO, "Reached maximum client limit (active: %u)", active_clients);
					break;
				}

				/* Create a command socket */
				ret = socketpair(AF_UNIX, SOCK_STREAM, 0, cmd_fd);
				if (ret < 0) {
					syslog(LOG_ERR, "Error creating command socket");
					close(fd);
					break;
				}

				pid = fork();
				if (pid == 0) {	/* child */
				
					/* Drop privileges after this point */
					drop_privileges(&config);

					/* close any open descriptors before
					 * running the server
					 */
					close(cmd_fd[0]);
					clear_lists(&s);
					
					ws.config = &config;
					ws.cmd_fd = cmd_fd[1];
					ws.tun_fd = -1;
					ws.conn_fd = fd;
					ws.creds = &creds;

					vpn_server(&ws);
					exit(0);
				} else if (pid == -1) {
fork_failed:
					close(cmd_fd[0]);
				} else { /* parent */
					ctmp = calloc(1, sizeof(struct proc_list_st));
					if (ctmp == NULL) {
						kill(pid, SIGTERM);
						goto fork_failed;
					}
					memcpy(&ctmp->remote_addr, &ws.remote_addr, ws.remote_addr_len);
					ctmp->remote_addr_len = ws.remote_addr_len;

					ctmp->pid = pid;
					ctmp->fd = cmd_fd[0];
					set_cloexec_flag (cmd_fd[0], 1);

					list_add(&(ctmp->list), &(clist.list));
					active_clients++;
				}
				close(cmd_fd[1]);
				close(fd);
			}
		}

		/* Check for any pending commands */
		list_for_each_safe(pos, cq, &clist.list) {
			ctmp = list_entry(pos, struct proc_list_st, list);
			
			if (FD_ISSET(ctmp->fd, &rd)) {
				ret = handle_commands(&s, ctmp);
				if (ret < 0) {
					if (ret == -2) {
						/* received a bad command from worker */
						kill(ctmp->pid, SIGTERM);
					}
					call_disconnect_script(&s, ctmp);
					remove_proc(ctmp);
					active_clients--;
				}
			}
		}

		/* Check if we need to expire any cookies */
		if (need_maintainance != 0) {
			need_maintainance = 0;
			pid = fork();
			if (pid == 0) {	/* child */
				syslog(LOG_INFO, "Performing maintainance");
				clear_lists(&s);

				expire_cookies(&s);
				expire_tls_sessions(&s);

				exit(0);
			}
			alarm(MAINTAINANCE_TIME);
		}
		
		if (need_children_cleanup != 0) {
			cleanup_children(&s);
		}

	}

	return 0;
}