usr.sbin/chroot/chroot.c

   1 /*      $NetBSD: chroot.c,v 1.19 2011/09/20 14:28:52 christos Exp $     */
   2
   3 /*
   4  * Copyright (c) 1988, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #ifndef lint
  34 __COPYRIGHT("@(#) Copyright (c) 1988, 1993\
  35  The Regents of the University of California.  All rights reserved.");
  36 #endif /* not lint */
  37
  38 #ifndef lint
  39 #if 0
  40 static char sccsid[] = "@(#)chroot.c    8.1 (Berkeley) 6/9/93";
  41 #else
  42 __RCSID("$NetBSD: chroot.c,v 1.19 2011/09/20 14:28:52 christos Exp $");
  43 #endif
  44 #endif /* not lint */
  45
  46 #include <sys/param.h>
  47
  48 #include <err.h>
  49 #include <errno.h>
  50 #include <grp.h>
  51 #include <paths.h>
  52 #include <pwd.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <inttypes.h>
  56 #include <string.h>
  57 #include <unistd.h>
  58
  59 static void     usage(void) __dead;
  60
  61 static int
  62 getnum(const char *str, uintmax_t *num)
  63 {
  64         char *ep;
  65
  66         errno = 0;
  67
  68         *num = strtoumax(str, &ep, 0);
  69         if (str[0] == '\0' || *ep != '\0') {
  70                 errno = EINVAL;
  71                 return -1;
  72         }
  73
  74         if (errno == ERANGE && *num == UINTMAX_MAX)
  75                 return -1;
  76
  77         return 0;
  78 }
  79
  80
  81 static gid_t
  82 getgroup(const char *group)
  83 {
  84         uintmax_t       num;
  85         struct group    *gp;
  86
  87         if ((gp = getgrnam(group)) != NULL)
  88                 return gp->gr_gid;
  89
  90         if (getnum(group, &num) == -1)
  91             errx(1, "no such group `%s'", group);
  92
  93         return (gid_t)num;
  94 }
  95
  96 static uid_t
  97 getuser(const char *user)
  98 {
  99         uintmax_t       num;
 100         struct passwd   *pw;
 101
 102         if ((pw = getpwnam(user)) != NULL)
 103                 return pw->pw_uid;
 104
 105         if (getnum(user, &num) == -1)
 106                 errx(1, "no such user `%s'", user);
 107
 108         return (uid_t)num;
 109 }
 110
 111 int
 112 main(int argc, char *argv[])
 113 {
 114         char    *user;          /* user to switch to before running program */
 115         char    *group;         /* group to switch to ... */
 116         char    *grouplist;     /* group list to switch to ... */
 117         char            *p;
 118         const char      *shell;
 119         gid_t           gid, gidlist[NGROUPS_MAX];
 120         uid_t           uid;
 121         int             ch, gids;
 122
 123         user = NULL;
 124         group = NULL;
 125         grouplist = NULL;
 126         gid = 0;
 127         uid = 0;
 128         gids = 0;
 129         while ((ch = getopt(argc, argv, "G:g:u:")) != -1) {
 130                 switch(ch) {
 131                 case 'u':
 132                         user = optarg;
 133                         if (*user == '\0')
 134                                 usage();
 135                         break;
 136                 case 'g':
 137                         group = optarg;
 138                         if (*group == '\0')
 139                                 usage();
 140                         break;
 141                 case 'G':
 142                         grouplist = optarg;
 143                         if (*grouplist == '\0')
 144                                 usage();
 145                         break;
 146                 case '?':
 147                 default:
 148                         usage();
 149                 }
 150         }
 151         argc -= optind;
 152         argv += optind;
 153
 154         if (argc < 1)
 155                 usage();
 156
 157         if (user != NULL)
 158                 uid = getuser(user);
 159
 160         if (group != NULL)
 161                 gid = getgroup(group);
 162
 163         if (grouplist != NULL) {
 164                 while ((p = strsep(&grouplist, ",")) != NULL) {
 165                         if (*p == '\0')
 166                                 continue;
 167
 168                         if (gids == NGROUPS_MAX)
 169                                 errx(1,
 170                                     "too many supplementary groups provided");
 171
 172                         gidlist[gids++] = getgroup(p);
 173                 }
 174         }
 175
 176         if (chdir(argv[0]) == -1 || chroot(".") == -1)
 177                 err(1, "%s", argv[0]);
 178
 179         if (gids && setgroups(gids, gidlist) == -1)
 180                 err(1, "setgroups");
 181         if (group && setgid(gid) == -1)
 182                 err(1, "setgid");
 183         if (user && setuid(uid) == -1)
 184                 err(1, "setuid");
 185
 186         if (argv[1]) {
 187                 execvp(argv[1], &argv[1]);
 188                 err(1, "%s", argv[1]);
 189         }
 190
 191         if ((shell = getenv("SHELL")) == NULL)
 192                 shell = _PATH_BSHELL;
 193         execlp(shell, shell, "-i", NULL);
 194         err(1, "%s", shell);
 195         /* NOTREACHED */
 196 }
 197
 198 static void
 199 usage(void)
 200 {
 201
 202         (void)fprintf(stderr, "Usage: %s [-G group,group,...] [-g group] "
 203             "[-u user] newroot [command]\n", getprogname());
 204         exit(1);
 205 }