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 /* Call setgroups to set the supplementary groups to those listed in GROUPS.
  58    GROUPS is a comma separated list of supplementary groups (names or numbers).
  59    Parse that list, converting any names to numbers, and call setgroups on the
  60    resulting numbers.  Upon any failure give a diagnostic and return nonzero.
  61    Otherwise return zero.  */
  62 static int
  63 set_additional_groups (char const *groups)
  64 {
  65   GETGROUPS_T *gids = NULL;
  66   size_t n_gids_allocated = 0;
  67   size_t n_gids = 0;
  68   char *buffer = xstrdup (groups);
  69   char const *tmp;
  70   int ret = 0;
  71
  72   for (tmp = strtok (buffer, ","); tmp; tmp = strtok (NULL, ","))
  73     {
  74       struct group *g;
  75       unsigned long int value;
  76
  77       if (xstrtoul (tmp, NULL, 10, &value, "") == LONGINT_OK && value <= MAXGID)
  78         g = getgrgid (value);
  79       else
  80         {
  81           g = getgrnam (tmp);
  82           if (g != NULL)
  83             value = g->gr_gid;
  84         }
  85
  86       if (g == NULL)
  87         {
  88           error (0, errno, _("invalid group %s"), quote (tmp));
  89           ret = -1;
  90           continue;
  91         }
  92
  93       if (n_gids == n_gids_allocated)
  94         gids = X2NREALLOC (gids, &n_gids_allocated);
  95       gids[n_gids++] = value;
  96     }
  97
  98   if (ret == 0 && n_gids == 0)
  99     {
 100       error (0, 0, _("invalid group list %s"), quote (groups));
 101       ret = -1;
 102     }
 103
 104   if (ret == 0)
 105     {
 106       ret = setgroups (n_gids, gids);
 107       if (ret)
 108         error (0, errno, _("failed to set additional groups"));
 109     }
 110
 111   free (buffer);
 112   free (gids);
 113   return ret;
 114 }
 115
 116 void
 117 usage (int status)
 118 {
 119   if (status != EXIT_SUCCESS)
 120     fprintf (stderr, _("Try `%s --help' for more information.\n"),
 121              program_name);
 122   else
 123     {
 124       printf (_("\
 125 Usage: %s [OPTION] NEWROOT [COMMAND [ARG]...]\n\
 126   or:  %s OPTION\n\
 127 "), program_name, program_name);
 128
 129       fputs (_("\
 130 Run COMMAND with root directory set to NEWROOT.\n\
 131 \n\
 132 "), stdout);
 133
 134       fputs (_("\
 135   --userspec=USER:GROUP  specify user and group (ID or name) to use\n\
 136   --groups=G_LIST        specify supplementary groups as g1,g2,..,gN\n\
 137 "), stdout);
 138
 139       fputs (HELP_OPTION_DESCRIPTION, stdout);
 140       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 141       fputs (_("\
 142 \n\
 143 If no command is given, run ``${SHELL} -i'' (default: /bin/sh).\n\
 144 "), stdout);
 145       emit_ancillary_info ();
 146     }
 147   exit (status);
 148 }
 149
 150 int
 151 main (int argc, char **argv)
 152 {
 153   int c;
 154   char const *userspec = NULL;
 155   char const *groups = NULL;
 156
 157   initialize_main (&argc, &argv);
 158   set_program_name (argv[0]);
 159   setlocale (LC_ALL, "");
 160   bindtextdomain (PACKAGE, LOCALEDIR);
 161   textdomain (PACKAGE);
 162
 163   initialize_exit_failure (EXIT_CANCELED);
 164   atexit (close_stdout);
 165
 166   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
 167                       usage, AUTHORS, (char const *) NULL);
 168
 169   while ((c = getopt_long (argc, argv, "+", long_opts, NULL)) != -1)
 170     {
 171       switch (c)
 172         {
 173         case USERSPEC:
 174           userspec = optarg;
 175           break;
 176         case GROUPS:
 177           groups = optarg;
 178           break;
 179         default:
 180           usage (EXIT_CANCELED);
 181         }
 182     }
 183
 184   if (argc <= optind)
 185     {
 186       error (0, 0, _("missing operand"));
 187       usage (EXIT_CANCELED);
 188     }
 189
 190   if (chroot (argv[optind]) != 0)
 191     error (EXIT_CANCELED, errno, _("cannot change root directory to %s"),
 192            argv[optind]);
 193
 194   if (chdir ("/"))
 195     error (EXIT_CANCELED, errno, _("cannot chdir to root directory"));
 196
 197   if (argc == optind + 1)
 198     {
 199       /* No command.  Run an interactive shell.  */
 200       char *shell = getenv ("SHELL");
 201       if (shell == NULL)
 202         shell = bad_cast ("/bin/sh");
 203       argv[0] = shell;
 204       argv[1] = bad_cast ("-i");
 205       argv[2] = NULL;
 206     }
 207   else
 208     {
 209       /* The following arguments give the command.  */
 210       argv += optind + 1;
 211     }
 212
 213   bool fail = false;
 214
 215   /* Attempt to set all three: supplementary groups, group ID, user ID.
 216      Diagnose any failures.  If any have failed, exit before execvp.  */
 217   if (userspec)
 218     {
 219       uid_t uid = -1;
 220       gid_t gid = -1;
 221       char *user;
 222       char *group;
 223       char const *err = parse_user_spec (userspec, &uid, &gid, &user, &group);
 224
 225       if (err)
 226         error (EXIT_CANCELED, errno, "%s", err);
 227
 228       free (user);
 229       free (group);
 230
 231       if (groups && set_additional_groups (groups))
 232         fail = true;
 233
 234       if (gid != (gid_t) -1 && setgid (gid))
 235         {
 236           error (0, errno, _("failed to set group-ID"));
 237           fail = true;
 238         }
 239
 240       if (uid != (uid_t) -1 && setuid (uid))
 241         {
 242           error (0, errno, _("failed to set user-ID"));
 243           fail = true;
 244         }
 245     }
 246   else
 247     {
 248       /* Yes, this call is identical to the one above.
 249          However, when --userspec and --groups groups are used together,
 250          we don't want to call this function until after parsing USER:GROUP,
 251          and it must be called before setuid.  */
 252       if (groups && set_additional_groups (groups))
 253         fail = true;
 254     }
 255
 256   if (fail)
 257     exit (EXIT_CANCELED);
 258
 259   /* Execute the given command.  */
 260   execvp (argv[0], argv);
 261
 262   {
 263     int exit_status = (errno == ENOENT ? EXIT_ENOENT : EXIT_CANNOT_INVOKE);
 264     error (0, errno, _("failed to run command %s"), quote (argv[0]));
 265     exit (exit_status);
 266   }
 267 }