/*

 * Copyright (c) 2014 Sunil Nimmagadda <sunil@nimmagadda.net>

 *

 * 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 <sys/time.h>

#include <sys/tree.h>

#include <err.h>

#include <errno.h>

#include <event.h>

#include <netdb.h>

#include <pwd.h>

#include <signal.h>

#include <stdlib.h>

#include <string.h>

#include <syslog.h>

#include <unistd.h>

#include "imsgev.h"

#include "pop3d.h"

#include "ssl.h"

#define BACKLOG		5

static void auth_response(struct session *, int);

static void pop3_accept(int, short, void *);

static void pop3_listen(const char *);

static void pop3_pause(int, short, void *);

static void pop3d_imsgev(struct imsgev *, int, struct imsg *);

static void needfd(struct imsgev *);

static void sig_handler(int, short, void *);

struct imsgev		iev_pop3d;

void			*ssl_ctx;

void

pop3_main(int pair[2], struct passwd *pw)

{

	extern struct session_tree	sessions;

	struct event			ev_sigint, ev_sigterm;

	pid_t				pid;

	pid = fork();

	if (pid < 0)

		fatal("pop3e: fork");

	if (pid > 0)

		return;

	close(pair[0]);

	setproctitle("pop3 engine");

	SPLAY_INIT(&sessions);

	event_init();

	signal_set(&ev_sigint, SIGINT, sig_handler, NULL);

	signal_set(&ev_sigterm, SIGTERM, sig_handler, NULL);

	signal_add(&ev_sigint, NULL);

	signal_add(&ev_sigterm, NULL);

	imsgev_init(&iev_pop3d, pair[1], NULL, pop3d_imsgev, needfd);

	pop3_listen("pop3");

	ssl_init();

	if ((ssl_ctx = ssl_setup()) == NULL)

		fatal("ssl_setup failed");

	pop3_listen("pop3s");

	if (chroot(pw->pw_dir) == -1 || chdir("/") == -1)

		fatal("chroot");

	if (setgroups(1, &pw->pw_gid) ||

	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||

	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))

		fatal("cannot drop privileges");

	if (event_dispatch() < 0)

		fatal("event_dispatch");

	logit(LOG_INFO, "pop3 engine exiting");

	_exit(0);

}

static void

pop3_listen(const char *port)

{

	struct listener	*l = NULL;

	struct addrinfo	hints, *res, *res0;

	int		error, opt, serrno, s;

	const char	*cause = NULL;

	memset(&hints, 0, sizeof(hints));

	hints.ai_family = PF_UNSPEC;

	hints.ai_socktype = SOCK_STREAM;

	hints.ai_flags = AI_PASSIVE;

	error = getaddrinfo(NULL, port, &hints, &res0);

	if (error)

		errx(1, "%s", gai_strerror(error));

	for (res = res0; res != NULL; res = res->ai_next) {

		s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);

		if (s == -1) {

			cause = "socket";

			continue;

		}

		opt = 1;

		if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,

		    &opt, sizeof(opt)) == -1)

			fatal("listener setsockopt(SO_REUSEADDR)");

		if (bind(s, res->ai_addr, res->ai_addrlen) == -1) {

			serrno = errno;

			cause = "bind";

			close(s);

			errno = serrno;

			continue;

		}

		set_nonblocking(s);

		if (listen(s, BACKLOG) == -1)

			fatal("listen");

		l = xcalloc(1, sizeof(*l), "pop3_listen");

		l->sock = s;

		if (strcmp(port, "pop3s") == 0)

			l->flags |= POP3S;

		event_set(&l->ev, s, EV_READ|EV_PERSIST, pop3_accept, l);

		event_add(&l->ev, NULL);

		evtimer_set(&l->pause, pop3_pause, l);

	}

	if (l == NULL)

		errx(1, "%s", cause);

	freeaddrinfo(res0);

}

static void

pop3_accept(int fd, short events, void *arg)

{

	struct sockaddr_storage ss;

	struct listener		*l = arg;

	struct timeval		timeout = {1, 0};

	socklen_t		len;

	int			s;

	len = sizeof(ss);

	s = accept(fd, (struct sockaddr *)&ss, &len);

	if (s == -1) {

		switch (errno) {

		case EINTR:

		case EWOULDBLOCK:

		case ECONNABORTED:

			return;

		case EMFILE:

		case ENFILE:

			event_del(&l->ev);

			evtimer_add(&l->pause, &timeout);

			return;

		default:

			fatalx("accept");

		}

	}

	set_nonblocking(s);

	l->ss = ss;

	session_init(l, s);

}

static void

pop3_pause(int fd, short events, void *arg)

{

	struct listener *l = arg;

	event_add(&l->ev, NULL);

}

static void

pop3d_imsgev(struct imsgev *iev, int code, struct imsg *imsg)

{

	extern struct session_tree	sessions;

	struct session			key, *r;

	switch (code) {

	case IMSGEV_IMSG:

		key.id = imsg->hdr.peerid;

		r = SPLAY_FIND(session_tree, &sessions, &key);

		if (r == NULL) {

			logit(LOG_INFO, "%u: session not found", key.id);

			fatalx("pop3e: session lost");

		}

		switch (imsg->hdr.type) {

		case IMSG_AUTH:

			auth_response(r, imsg->fd);

			break;

		default:

			logit(LOG_DEBUG, "%s: unexpected imsg %d",

			    __func__, imsg->hdr.type);

			break;

		}

		break;

	case IMSGEV_EREAD:

	case IMSGEV_EWRITE:

	case IMSGEV_EIMSG:

		fatal("pop3e: imsgev read/write error");

		break;

	case IMSGEV_DONE:

		event_loopexit(NULL);

		break;

	}

}

static void

auth_response(struct session *s, int fd)

{

	if (fd == -1) {

		session_reply(s, "%s", "-ERR auth failed");

		io_set_write(&s->io);

		session_close(s, 1);

		return;

	}

	session_imsgev_init(s, fd);

}

static void

needfd(struct imsgev *iev)

{

	/* XXX can anything be done to handle fd exhaustion? */

	fatalx("pop3e needs an fd");

}

static void

sig_handler(int sig, short event, void *arg)

{

	switch (sig) {

	case SIGINT:

	case SIGTERM:

		event_loopexit(NULL);

	}

}