/*      $OpenBSD: mailwrapper.c,v 1.23 2017/06/14 16:32:11 anton Exp $  */
/*      $NetBSD: mailwrapper.c,v 1.2 1999/02/20 22:10:07 thorpej Exp $  */

/*
 * Copyright (c) 1998
 *      Perry E. Metzger.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgment:
 *      This product includes software developed for the NetBSD Project
 *      by Perry E. Metzger.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <err.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <syslog.h>
#include <unistd.h>
#include <util.h>

#define _PATH_MAILERCONF        "/etc/mailer.conf"
#define _PATH_DEFAULTMTA        "/usr/sbin/smtpctl"

struct arglist {
        size_t argc, maxc;
        char **argv;
};

static void initarg(struct arglist *);
static void addarg(struct arglist *, const char *);

extern const char *__progname;  /* from crt0.o */

static void
initarg(struct arglist *al)
{
        al->argc = 0;
        al->maxc = 10;
        if ((al->argv = calloc(al->maxc, sizeof(char *))) == NULL)
                err(1, "malloc");
}

static void
addarg(struct arglist *al, const char *arg)
{
        if (al->argc == al->maxc) {
                al->maxc <<= 1;
                al->argv = reallocarray(al->argv, al->maxc, sizeof(char *));
                if (al->argv == NULL)
                        err(1, "realloc");
        }

        al->argv[al->argc++] = (char *)arg;
}

int
main(int argc, char *argv[])
{
        FILE *config;
        char *line, *cp, *from, *to, *ap;
        const char *progname;
        size_t len, lineno = 0;
        struct arglist al;

        if (pledge("stdio rpath exec", NULL) == -1)
                err(1, "pledge");

        /* change __progname to mailwrapper so we get sensible error messages */
        progname = __progname;
        __progname = "mailwrapper";

        initarg(&al);
        for (len = 0; len < argc; len++)
                addarg(&al, argv[len]);

        config = fopen(_PATH_MAILERCONF, "r");

        if (pledge("stdio exec", NULL) == -1)
                err(1, "pledge");

        if (config == NULL) {
                addarg(&al, NULL);
                openlog(__progname, LOG_PID, LOG_MAIL);
                syslog(LOG_INFO, "cannot open %s, using %s as default MTA",
                    _PATH_MAILERCONF, _PATH_DEFAULTMTA);
                closelog();
                execv(_PATH_DEFAULTMTA, al.argv);
                err(1, "cannot exec %s", _PATH_DEFAULTMTA);
                /*NOTREACHED*/
        }

        for (;;) {
                if ((line = fparseln(config, &len, &lineno, NULL, 0)) == NULL) {
                        if (feof(config))
                                errx(1, "no mapping in %s", _PATH_MAILERCONF);
                        err(1, "fparseln");
                }

#define WS      " \t\n"
                cp = line;

                cp += strspn(cp, WS);
                if (cp[0] == '\0') {
                        /* empty line */
                        free(line);
                        continue;
                }

                if ((from = strsep(&cp, WS)) == NULL || cp == NULL)
                        goto parse_error;

                cp += strspn(cp, WS);

                if ((to = strsep(&cp, WS)) == NULL)
                        goto parse_error;

                if (strcmp(from, progname) == 0) {
                        for (ap = strsep(&cp, WS); ap != NULL;
                            ap = strsep(&cp, WS))
                                if (*ap)
                                        addarg(&al, ap);
                        break;
                }

                free(line);
        }

        (void)fclose(config);

        addarg(&al, NULL);

        execv(to, al.argv);
        err(1, "cannot exec %s", to);
        /*NOTREACHED*/
parse_error:
        errx(1, "parse error in %s at line %lu",
            _PATH_MAILERCONF, (u_long)lineno);
        /*NOTREACHED*/
}