/*

 * 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/param.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <sys/stat.h>

#include <event.h>

#include <fcntl.h>

#include <pwd.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <syslog.h>

#include <unistd.h>

#include "imsgev.h"

#include "pop3d.h"

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

static void update(struct imsgev *, struct imsg *, struct m_backend *);

static void retr(struct imsgev *, struct imsg *, struct m_backend *);

static void dele(struct imsgev *, struct imsg *, struct m_backend *);

static void rset(struct imsgev *, struct imsg *, struct m_backend *);

static void list(struct imsgev *, struct imsg *, struct m_backend *);

static void do_list(unsigned int, size_t *, char *, size_t);

static struct m_backend *m_backend_lookup(enum m_type);

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

static void needfd(struct imsgev *);

static size_t expand(char *, const char *, size_t, struct passwd *);

static struct mdrop m;

void

maildrop_init(uint32_t session_id, int pair[2], struct passwd *pw,

    int type, const char *path)

{

	struct imsgev		iev_session;

	struct event		ev_sigint, ev_sigterm;

	struct stats		stats;

	struct m_backend	*mb;

	char			buf[MAXPATHLEN];

	pid_t			pid;

	mode_t			old_mask;

	int			fd, flags, res = -1;

	if (seteuid(pw->pw_uid) < 0)

		fatal("cannot lower privileges");

	pid = fork();

	if (seteuid(0) < 0)

		fatal("cannot restore privileges");

	if (pid < 0)

		fatal("maildrop: fork");

	if (pid > 0)

		return;

	if (seteuid(pw->pw_uid) < 0)

		fatal("cannot lower privileges");

	close(pair[0]);

	setproctitle("maildrop");

	if ((mb = m_backend_lookup(type)) == NULL)

		fatalx("maildrop: invalid backend");

	if (expand(buf, path, sizeof(buf), pw) >= sizeof(buf))

		fatalx("maildrop: path truncation");

	flags = O_CREAT;

	if (type == M_MBOX)

		flags |= O_RDWR;

	else

		flags |= O_RDONLY;

	old_mask = umask(S_IXUSR|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH);

	if ((fd = open(buf, flags)) == -1)

		logit(LOG_CRIT, "%zu: failed to open %s", session_id , buf);

	if (fd != -1) {

		m.fd = fd;

		res = mb->init(&m, &stats.nmsgs, &stats.sz);

	}

	umask(old_mask);

	if (seteuid(0) < 0)

		fatal("cannot restore privileges");

	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");

	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_session, pair[1], mb, session_imsgev, needfd);

	if (res == 0) {

		imsgev_xcompose(&iev_session, IMSG_MAILDROP_INIT, session_id,

		    0, -1, &stats, sizeof(struct stats), "maildrop_init");

	} else {

		logit(LOG_CRIT, "%zu: maildrop init failed %s",

		    session_id, buf);

		imsgev_xcompose(&iev_session, IMSG_MAILDROP_INIT, session_id,

		    0, -1, NULL, 0, "maildrop_init");

	}

	if (event_dispatch() < 0)

		fatal("event_dispatch");

	logit(LOG_INFO, "maildrop process exiting");

	_exit(0);

}

/*

 * Build dst by substituting '~' with user's home dir and '%u' with user name

 * in src. Return the length of string built. If return value >= dst_sz then

 * dst is truncated. 

 */

static size_t

expand(char *dst, const char *src, size_t dst_sz, struct passwd *pw)

{

	size_t	i = 0, r;

	int	c;

	while ((c = *src++)) {

		if (i >= dst_sz)

			break;

		switch (c) {

		case '~':

			if ((r = strlcpy(&dst[i], pw->pw_dir,

			    (dst_sz - i))) >= (dst_sz - i)) {

				i += r;

				goto end;

			}

			i += r;

			break;

		case '%':

			if (*src == 'u') {

				if ((r = strlcpy(&dst[i], pw->pw_name,

				    (dst_sz - i))) >= (dst_sz - i)) {

					i += r;

					goto end;

				}

				i += r;

				src++;

			} else

				dst[i++] = c;

			break;

		default:

			dst[i++] = c;

			break;

		}

	}

end:

	if (c)

		while ((c = *src++))

			i++;

	dst[dst_sz - 1] = '\0';

	return (i);

}

static void

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

{

	struct m_backend	*mb = iev->data;

	switch (code) {

	case IMSGEV_IMSG:

		switch (imsg->hdr.type) {

		case IMSG_MAILDROP_UPDATE:

			update(iev, imsg, mb);

			break;

		case IMSG_MAILDROP_RETR:

			retr(iev, imsg, mb);

			break;

		case IMSG_MAILDROP_DELE:

			dele(iev, imsg, mb);

			break;

		case IMSG_MAILDROP_RSET:

			rset(iev, imsg, mb);

			break;

		case IMSG_MAILDROP_LIST:

			list(iev, imsg, mb);

			break;

		case IMSG_MAILDROP_LISTALL:

			break;

		default:

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

			    __func__, imsg->hdr.type);

			break;

		}

		break;

	case IMSGEV_EREAD:

	case IMSGEV_EWRITE:

	case IMSGEV_EIMSG:

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

		break;

	case IMSGEV_DONE:

		event_loopexit(NULL);

		break;

	}

}

static void

update(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)

{

	int		res;

	uint32_t	session_id = imsg->hdr.peerid;

	if ((res = mb->update(&m)) == 0)

		logit(LOG_INFO, "%zu: maildrop updated", session_id);

	else

		logit(LOG_CRIT, "%zu: maildrop updated failed", session_id);

	imsgev_xcompose(iev, IMSG_MAILDROP_UPDATE, session_id,  0,

	    -1, &res, sizeof(res), "maildrop_update");

}

static void

retr(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)

{

	struct retr_res	res;

	struct retr_req	*req = imsg->data;

	int		fd;

	fd = mb->retr(&m, req->idx, &res.nlines, &res.offset);

	/* pass on top arguments */

	res.top = req->top;

	res.ntop = req->ntop;

	imsgev_xcompose(iev, IMSG_MAILDROP_RETR, imsg->hdr.peerid, 0,

	    fd, &res, sizeof(res), "maildrop_retr");

}

static void

dele(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)

{

	unsigned int	*idx = imsg->data;

	int		res = 0;

	if (m.msgs_index[*idx]->flags & F_DELE) {

		res = -1;

		goto end;

	}

	m.msgs_index[*idx]->flags |= F_DELE;

end:

	imsgev_xcompose(iev, IMSG_MAILDROP_DELE, imsg->hdr.peerid, 0,

	    -1, &res, sizeof(res), "maildrop_dele");

}

static void

rset(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)

{

	size_t	i;

	for (i = 0; i < m.nmsgs; i++)

		m.msgs_index[i]->flags = 0;

	imsgev_xcompose(iev, IMSG_MAILDROP_RSET, imsg->hdr.peerid, 0,

	    -1, NULL, 0, "maildrop_rset");

}

static void

list(struct imsgev *iev, struct imsg *imsg, struct m_backend *mb)

{

	struct list_req	*req = imsg->data;

	struct list_res	res;

	char		hash[SHA1_DIGEST_STRING_LENGTH];

	size_t		sz;

	res.idx = req->idx;

	do_list(req->idx, &sz, hash, sizeof(hash));

	res.uidl = req->uidl;

	if (res.uidl)

		strlcpy(res.u.hash, hash, sizeof(res.u.hash));

	else

		res.u.sz = sz;

	imsgev_xcompose(iev, IMSG_MAILDROP_LIST, imsg->hdr.peerid, 0,

	    -1, &res, sizeof(res), "maildrop_list");

}

static void

{

}

static void

do_list(unsigned int idx, size_t *sz, char *hash, size_t hash_sz)

{

	if (m.msgs_index[idx]->flags & F_DELE) {

		*sz = 0;

		strlcpy(hash, "", hash_sz);

		return;

	}