/*      $NetBSD: mailwrapper.c,v 1.11 2018/01/23 21:06:25 sevan 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 <unistd.h>

#define _PATH_MAILERCONF        "/etc/mailer.conf"

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

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

static void
initarg(struct arglist *al)
{
       al->argc = 0;
       al->maxc = 10;
       if ((al->argv = malloc(al->maxc * sizeof(char *))) == NULL)
               /*
                * This (using err("mailwrapper")) is intentional.
                * Mailwrapper plays ugly games with argv[0] and thus it
                * is often difficult for people to know that the error
                * isn't from "mailq" or "sendmail" but from mailwrapper
                * -- having mailwrapper add an indication that it was really
                * mailwrapper running was a requested feature.
                */
               err(1, "mailwrapper");
}

static void
addarg(struct arglist *al, const char *arg, int copy)
{
       if (al->argc == al->maxc) {
           al->maxc <<= 1;
           if ((al->argv = realloc(al->argv,
               al->maxc * sizeof(char *))) == NULL)
                   err(1, "mailwrapper");
       }
       if (copy) {
               if ((al->argv[al->argc++] = strdup(arg)) == NULL)
                       err(1, "mailwrapper:");
       } else
               al->argv[al->argc++] = arg;
}

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

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

       if ((config = fopen(_PATH_MAILERCONF, "r")) == NULL)
               err(1, "mailwrapper: can't open %s", _PATH_MAILERCONF);

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

#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)
                       goto parse_error;

               cp += strspn(cp, WS);

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

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

               free(line);
       }

       (void)fclose(config);

       for (i = 1; i < argc; i++)
               addarg(&al, argv[i], 0);

       addarg(&al, NULL, 0);
       execve(to, __UNCONST(al.argv), envp);
       err(1, "mailwrapper: execing %s", to);
       /*NOTREACHED*/
parse_error:
       errx(1, "mailwrapper: parse error in %s at line %lu",
           _PATH_MAILERCONF, (u_long)lineno);
       /*NOTREACHED*/
}