/*      $OpenBSD: mailwrapper.c,v 1.18 2007/11/06 14:39:19 otto Exp $   */
/*      $NetBSD: mailwrapper.c,v 1.9 2003/03/09 08:10:43 mjl Exp $      */

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * 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 <sys/param.h>

#include <err.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <libutil.h>
#include <sysexits.h>
#include <syslog.h>

#include "pathnames.h"

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

int main(int, char *[], char *[]);

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

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

static void
addarg(struct arglist *al, const char *arg)
{

        if (al->argc == al->maxc) {
                al->maxc <<= 1;
                al->argv = realloc(al->argv, al->maxc * sizeof(char *));
                if (al->argv == NULL)
                        err(EX_TEMPFAIL, "realloc");
        }
        if (arg == NULL)
                al->argv[al->argc++] = NULL;
        else if ((al->argv[al->argc++] = strdup(arg)) == NULL)
                err(EX_TEMPFAIL, "strdup");
}

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

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

        initarg(&al);
        addarg(&al, argv[0]);

        snprintf(localmailerconf, MAXPATHLEN, "%s/etc/mail/mailer.conf",
            getlocalbase());

        mailerconf = localmailerconf;
        if ((config = fopen(localmailerconf, "r")) == NULL)
                mailerconf = _PATH_MAILERCONF;

        if (config == NULL && ((config = fopen(mailerconf, "r")) == NULL)) {
                int serrno = errno;
                openlog(getprogname(), LOG_PID, LOG_MAIL);

                if (serrno == ENOENT) {
                        addarg(&al, NULL);
                        syslog(LOG_INFO, "%s does not exist, using %s as default MTA",
                            mailerconf, _PATH_DEFAULTMTA);
                        closelog();
                        execve(_PATH_DEFAULTMTA, al.argv, envp);
                        err(EX_OSERR, "cannot exec %s", _PATH_DEFAULTMTA);
                } else {
                        syslog(LOG_INFO, "cannot open %s: %s",
                            mailerconf, strerror(serrno));
                        closelog();
                        errno = serrno;
                        err(EX_OSERR, "cannot open %s", mailerconf);
                }
                /*NOTREACHED*/
        }

        for (;;) {
                if ((line = fparseln(config, &len, &lineno, NULL, 0)) == NULL) {
                        if (feof(config))
                                errx(EX_CONFIG, "no mapping in %s", mailerconf);
                        err(EX_CONFIG, "cannot parse line %lu", (u_long)lineno);
                }

#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);

        for (i = 1; i < argc; i++)
                addarg(&al, argv[i]);

        addarg(&al, NULL);
        execve(to, al.argv, envp);
        err(EX_OSERR, "cannot exec %s", to);
        /*NOTREACHED*/
parse_error:
        errx(EX_CONFIG, "parse error in %s at line %lu",
            mailerconf, (u_long)lineno);
        /*NOTREACHED*/
}