src/chroot.c

   1 /* chroot -- run command or shell with special root directory
   2    Copyright (C) 95, 96, 1997, 1999-2004, 2007-2009
   3    Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Roland McGrath.  */
  19
  20 #include <config.h>
  21 #include <getopt.h>
  22 #include <stdio.h>
  23 #include <sys/types.h>
  24 #include <grp.h>
  25
  26 #include "system.h"
  27 #include "error.h"
  28 #include "long-options.h"
  29 #include "quote.h"
  30 #include "userspec.h"
  31 #include "xstrtol.h"
  32
  33 /* The official name of this program (e.g., no `g' prefix).  */
  34 #define PROGRAM_NAME "chroot"
  35
  36 #define AUTHORS proper_name ("Roland McGrath")
  37
  38 #ifndef MAXGID
  39 # define MAXGID GID_T_MAX
  40 #endif
  41
  42 enum
  43 {
  44   GROUPS = UCHAR_MAX + 1,
  45   USERSPEC
  46 };
  47
  48 static struct option const long_opts[] =
  49 {
  50   {"groups", required_argument, NULL, GROUPS},
  51   {"userspec", required_argument, NULL, USERSPEC},
  52   {GETOPT_HELP_OPTION_DECL},
  53   {GETOPT_VERSION_OPTION_DECL},
  54   {NULL, 0, NULL, 0}
  55 };
  56
  57 /* Groups is a comma separated list of additional groups.  */
  58 static int
  59 set_additional_groups (char const *groups)
  60 {
  61   GETGROUPS_T *gids = NULL;
  62   size_t n_gids_allocated = 0;
  63   size_t n_gids = 0;
  64   char *buffer = xstrdup (groups);
  65   char const *tmp;
  66   int ret;
  67
  68   for (tmp = strtok (buffer, ","); tmp; tmp = strtok (NULL, ","))
  69     {
  70       struct group *g;
  71       unsigned long int value;
  72
  73       if (xstrtoul (tmp, NULL, 10, &value, "") == LONGINT_OK && value <= MAXGID)
  74         {
  75           g = getgrgid (value);
  76         }
  77       else
  78         {
  79           g = getgrnam (tmp);
  80           if (g != NULL)
  81             value = g->gr_gid;
  82         }
  83
  84       if (g == NULL)
  85         {
  86           error (0, errno, _("cannot find group %s"), tmp);
  87           free (buffer);
  88           return 1;
  89         }
  90
  91       if (n_gids == n_gids_allocated)
  92         gids = x2nrealloc (gids, &n_gids_allocated, sizeof *gids);
  93       gids[n_gids++] = value;
  94     }
  95
  96   free (buffer);
  97
  98   ret = setgroups (n_gids, gids);
  99
 100   free (gids);
 101
 102   return ret;
 103 }
 104
 105
 106 void
 107 usage (int status)
 108 {
 109   if (status != EXIT_SUCCESS)
 110     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 111              program_name);
 112   else
 113     {
 114       printf (_("\
 115 Usage: %s [OPTION] NEWROOT [COMMAND [ARG]...]\n\
 116   or:  %s OPTION\n\
 117 "), program_name, program_name);
 118
 119       fputs (_("\
 120 Run COMMAND with root directory set to NEWROOT.\n\
 121 \n\
 122 "), stdout);
 123
 124       fputs (_("\
 125   --userspec=USER:GROUP  specify user and group (ID or name) to use\n\
 126   --groups=G_LIST        specify supplementary groups as g1,g2,..,gN\n\
 127 "), stdout);
 128
 129       fputs (HELP_OPTION_DESCRIPTION, stdout);
 130       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 131       fputs (_("\
 132 \n\
 133 If no command is given, run ``${SHELL} -i'' (default: /bin/sh).\n\
 134 "), stdout);
 135       emit_bug_reporting_address ();
 136     }
 137   exit (status);
 138 }
 139
 140 int
 141 main (int argc, char **argv)
 142 {
 143   int c;
 144   char const *userspec = NULL;
 145   char const *groups = NULL;
 146
 147   initialize_main (&argc, &argv);
 148   set_program_name (argv[0]);
 149   setlocale (LC_ALL, "");
 150   bindtextdomain (PACKAGE, LOCALEDIR);
 151   textdomain (PACKAGE);
 152
 153   initialize_exit_failure (EXIT_FAILURE);
 154   atexit (close_stdout);
 155
 156   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
 157                       usage, AUTHORS, (char const *) NULL);
 158
 159   while ((c = getopt_long (argc, argv, "+", long_opts, NULL)) != -1)
 160     {
 161       switch (c)
 162         {
 163         case USERSPEC:
 164           userspec = optarg;
 165           break;
 166         case GROUPS:
 167           groups = optarg;
 168           break;
 169         default:
 170           usage (EXIT_FAILURE);
 171         }
 172     }
 173
 174   if (argc <= optind)
 175     {
 176       error (0, 0, _("missing operand"));
 177       usage (EXIT_FAILURE);
 178     }
 179
 180   if (chroot (argv[optind]) != 0)
 181     error (EXIT_FAILURE, errno, _("cannot change root directory to %s"),
 182            argv[optind]);
 183
 184   if (chdir ("/"))
 185     error (EXIT_FAILURE, errno, _("cannot chdir to root directory"));
 186
 187   if (argc == optind + 1)
 188     {
 189       /* No command.  Run an interactive shell.  */
 190       char *shell = getenv ("SHELL");
 191       if (shell == NULL)
 192         shell = bad_cast ("/bin/sh");
 193       argv[0] = shell;
 194       argv[1] = bad_cast ("-i");
 195       argv[2] = NULL;
 196     }
 197   else
 198     {
 199       /* The following arguments give the command.  */
 200       argv += optind + 1;
 201     }
 202
 203   if (userspec)
 204     {
 205       uid_t uid = -1;
 206       gid_t gid = -1;
 207       char *user;
 208       char *group;
 209       char const *err = parse_user_spec (userspec, &uid, &gid, &user, &group);
 210       bool fail = false;
 211
 212       if (err)
 213         error (EXIT_FAILURE, errno, "%s", err);
 214
 215       free (user);
 216       free (group);
 217
 218       /* Attempt to set all three: supplementary groups, group ID, user ID.
 219          Diagnose any failures.  If any have failed, exit before execvp.  */
 220       if (groups && set_additional_groups (groups))
 221         {
 222           error (0, errno, _("failed to set additional groups"));
 223           fail = true;
 224         }
 225
 226       if (gid != (gid_t) -1 && setgid (gid))
 227         {
 228           error (0, errno, _("failed to set group-ID"));
 229           fail = true;
 230         }
 231
 232       if (uid != (uid_t) -1 && setuid (uid))
 233         {
 234           error (0, errno, _("failed to set user-ID"));
 235           fail = true;
 236         }
 237
 238       if (fail)
 239         exit (EXIT_FAILURE);
 240     }
 241
 242   /* Execute the given command.  */
 243   execvp (argv[0], argv);
 244
 245   {
 246     int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 247     error (0, errno, _("cannot run command %s"), quote (argv[0]));
 248     exit (exit_status);
 249   }
 250 }