libexec/dma/dma-mbox-create.c

   1 /*
   2  * Copyright (c) 2010-2014, Simon Schubert <2@0x2c.org>.
   3  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to The DragonFly Project
   6  * by Simon Schubert <2@0x2c.org>.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in
  16  *    the documentation and/or other materials provided with the
  17  *    distribution.
  18  * 3. Neither the name of The DragonFly Project nor the names of its
  19  *    contributors may be used to endorse or promote products derived
  20  *    from this software without specific, prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  23  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  24  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  25  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  26  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  28  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  29  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  31  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  32  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 /*
  37  * This binary is setuid root.  Use extreme caution when touching
  38  * user-supplied information.  Keep the root window as small as possible.
  39  */
  40
  41 #include <sys/param.h>
  42 #include <sys/stat.h>
  43
  44 #include <errno.h>
  45 #include <fcntl.h>
  46 #include <grp.h>
  47 #include <paths.h>
  48 #include <pwd.h>
  49 #include <stdio.h>
  50 #include <syslog.h>
  51 #include <unistd.h>
  52
  53 #include "dma.h"
  54
  55
  56 static void
  57 logfail(const char *fmt, ...)
  58 {
  59         int oerrno = errno;
  60         va_list ap;
  61         char outs[1024];
  62
  63         outs[0] = 0;
  64         if (fmt != NULL) {
  65                 va_start(ap, fmt);
  66                 vsnprintf(outs, sizeof(outs), fmt, ap);
  67                 va_end(ap);
  68         }
  69
  70         errno = oerrno;
  71         if (*outs != 0)
  72                 syslog(LOG_ERR, errno ? "%s: %m" : "%s", outs);
  73         else
  74                 syslog(LOG_ERR, errno ? "%m" : "unknown error");
  75
  76         exit(1);
  77 }
  78
  79 /*
  80  * Create a mbox in /var/mail for a given user, or make sure
  81  * the permissions are correct for dma.
  82  */
  83
  84 int
  85 main(int argc, char **argv)
  86 {
  87         const char *user;
  88         struct passwd *pw;
  89         struct group *gr;
  90         uid_t user_uid;
  91         gid_t mail_gid;
  92         int error;
  93         char fn[PATH_MAX+1];
  94         int f;
  95
  96         openlog("dma-mbox-create", 0, LOG_MAIL);
  97
  98         errno = 0;
  99         gr = getgrnam(DMA_GROUP);
 100         if (!gr)
 101                 logfail("cannot find dma group `%s'", DMA_GROUP);
 102
 103         mail_gid = gr->gr_gid;
 104
 105         if (setgid(mail_gid) != 0)
 106                 logfail("cannot set gid to %d (%s)", mail_gid, DMA_GROUP);
 107         if (getegid() != mail_gid)
 108                 logfail("cannot set gid to %d (%s), still at %d", mail_gid, DMA_GROUP, getegid());
 109
 110         /*
 111          * We take exactly one argument: the username.
 112          */
 113         if (argc != 2) {
 114                 errno = 0;
 115                 logfail("no arguments");
 116         }
 117         user = argv[1];
 118
 119         syslog(LOG_NOTICE, "creating mbox for `%s'", user);
 120
 121         /* the username may not contain a pathname separator */
 122         if (strchr(user, '/')) {
 123                 errno = 0;
 124                 logfail("path separator in username `%s'", user);
 125                 exit(1);
 126         }
 127
 128         /* verify the user exists */
 129         errno = 0;
 130         pw = getpwnam(user);
 131         if (!pw)
 132                 logfail("cannot find user `%s'", user);
 133
 134         user_uid = pw->pw_uid;
 135
 136         error = snprintf(fn, sizeof(fn), "%s/%s", _PATH_MAILDIR, user);
 137         if (error < 0 || (size_t)error >= sizeof(fn)) {
 138                 if (error >= 0) {
 139                         errno = 0;
 140                         logfail("mbox path too long");
 141                 }
 142                 logfail("cannot build mbox path for `%s/%s'", _PATH_MAILDIR, user);
 143         }
 144
 145         f = open(fn, O_RDONLY|O_CREAT|O_NOFOLLOW, 0600);
 146         if (f < 0)
 147                 logfail("cannot open mbox `%s'", fn);
 148
 149         if (fchown(f, user_uid, mail_gid))
 150                 logfail("cannot change owner of mbox `%s'", fn);
 151
 152         if (fchmod(f, 0620))
 153                 logfail("cannot change permissions of mbox `%s'", fn);
 154
 155         /* file should be present with the right owner and permissions */
 156
 157         syslog(LOG_NOTICE, "successfully created mbox for `%s'", user);
 158
 159         return (0);
 160 }