src/id.c

   1 /* id -- print real and effective UIDs and GIDs
   2    Copyright (C) 1989-2012 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Arnold Robbins.
  18    Major rewrite by David MacKenzie, djm@gnu.ai.mit.edu. */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <sys/types.h>
  23 #include <pwd.h>
  24 #include <grp.h>
  25 #include <getopt.h>
  26 #include <selinux/selinux.h>
  27
  28 #include "system.h"
  29 #include "error.h"
  30 #include "mgetgroups.h"
  31 #include "quote.h"
  32 #include "group-list.h"
  33
  34 /* The official name of this program (e.g., no 'g' prefix).  */
  35 #define PROGRAM_NAME "id"
  36
  37 #define AUTHORS \
  38   proper_name ("Arnold Robbins"), \
  39   proper_name ("David MacKenzie")
  40
  41 /* If nonzero, output only the SELinux context. -Z */
  42 static int just_context = 0;
  43
  44 static void print_user (uid_t uid);
  45 static void print_full_info (const char *username);
  46
  47 /* If true, output user/group name instead of ID number. -n */
  48 static bool use_name = false;
  49
  50 /* The real and effective IDs of the user to print. */
  51 static uid_t ruid, euid;
  52 static gid_t rgid, egid;
  53
  54 /* True unless errors have been encountered.  */
  55 static bool ok = true;
  56
  57 /* The SELinux context.  Start with a known invalid value so print_full_info
  58    knows when 'context' has not been set to a meaningful value.  */
  59 static security_context_t context = NULL;
  60
  61 static struct option const longopts[] =
  62 {
  63   {"context", no_argument, NULL, 'Z'},
  64   {"group", no_argument, NULL, 'g'},
  65   {"groups", no_argument, NULL, 'G'},
  66   {"name", no_argument, NULL, 'n'},
  67   {"real", no_argument, NULL, 'r'},
  68   {"user", no_argument, NULL, 'u'},
  69   {GETOPT_HELP_OPTION_DECL},
  70   {GETOPT_VERSION_OPTION_DECL},
  71   {NULL, 0, NULL, 0}
  72 };
  73
  74 void
  75 usage (int status)
  76 {
  77   if (status != EXIT_SUCCESS)
  78     emit_try_help ();
  79   else
  80     {
  81       printf (_("Usage: %s [OPTION]... [USERNAME]\n"), program_name);
  82       fputs (_("\
  83 Print user and group information for the specified USERNAME,\n\
  84 or (when USERNAME omitted) for the current user.\n\
  85 \n\
  86   -a              ignore, for compatibility with other versions\n\
  87   -Z, --context   print only the security context of the current user\n\
  88   -g, --group     print only the effective group ID\n\
  89   -G, --groups    print all group IDs\n\
  90   -n, --name      print a name instead of a number, for -ugG\n\
  91   -r, --real      print the real ID instead of the effective ID, with -ugG\n\
  92   -u, --user      print only the effective user ID\n\
  93 "), stdout);
  94       fputs (HELP_OPTION_DESCRIPTION, stdout);
  95       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  96       fputs (_("\
  97 \n\
  98 Without any OPTION, print some useful set of identified information.\n\
  99 "), stdout);
 100       emit_ancillary_info ();
 101     }
 102   exit (status);
 103 }
 104
 105 int
 106 main (int argc, char **argv)
 107 {
 108   int optc;
 109   int selinux_enabled = (is_selinux_enabled () > 0);
 110
 111   /* If true, output the list of all group IDs. -G */
 112   bool just_group_list = false;
 113   /* If true, output only the group ID(s). -g */
 114   bool just_group = false;
 115   /* If true, output real UID/GID instead of default effective UID/GID. -r */
 116   bool use_real = false;
 117   /* If true, output only the user ID(s). -u */
 118   bool just_user = false;
 119
 120   initialize_main (&argc, &argv);
 121   set_program_name (argv[0]);
 122   setlocale (LC_ALL, "");
 123   bindtextdomain (PACKAGE, LOCALEDIR);
 124   textdomain (PACKAGE);
 125
 126   atexit (close_stdout);
 127
 128   while ((optc = getopt_long (argc, argv, "agnruGZ", longopts, NULL)) != -1)
 129     {
 130       switch (optc)
 131         {
 132         case 'a':
 133           /* Ignore -a, for compatibility with SVR4.  */
 134           break;
 135
 136         case 'Z':
 137           /* politely decline if we're not on a selinux-enabled kernel. */
 138           if (!selinux_enabled)
 139             error (EXIT_FAILURE, 0,
 140                    _("--context (-Z) works only on an SELinux-enabled kernel"));
 141           just_context = 1;
 142           break;
 143
 144         case 'g':
 145           just_group = true;
 146           break;
 147         case 'n':
 148           use_name = true;
 149           break;
 150         case 'r':
 151           use_real = true;
 152           break;
 153         case 'u':
 154           just_user = true;
 155           break;
 156         case 'G':
 157           just_group_list = true;
 158           break;
 159         case_GETOPT_HELP_CHAR;
 160         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 161         default:
 162           usage (EXIT_FAILURE);
 163         }
 164     }
 165
 166   size_t n_ids = argc - optind;
 167   if (1 < n_ids)
 168     {
 169       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 170       usage (EXIT_FAILURE);
 171     }
 172
 173   if (n_ids && just_context)
 174     error (EXIT_FAILURE, 0,
 175            _("cannot print security context when user specified"));
 176
 177   if (just_user + just_group + just_group_list + just_context > 1)
 178     error (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));
 179
 180   bool default_format = (just_user + just_group + just_group_list == 0);
 181
 182   if (default_format && (use_real || use_name))
 183     error (EXIT_FAILURE, 0,
 184            _("cannot print only names or real IDs in default format"));
 185
 186   /* If we are on a selinux-enabled kernel, no user is specified, and
 187      either --context is specified or none of (-u,-g,-G) is specified,
 188      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 189      leave the context variable alone - it has been initialized to an
 190      invalid value that will be not displayed in print_full_info().  */
 191   if (selinux_enabled
 192       && n_ids == 0
 193       && (just_context ||
 194           (default_format && ! getenv ("POSIXLY_CORRECT"))))
 195     {
 196       /* Report failure only if --context (-Z) was explicitly requested.  */
 197       if (getcon (&context) && just_context)
 198         error (EXIT_FAILURE, 0, _("can't get process context"));
 199     }
 200
 201   if (n_ids == 1)
 202     {
 203       struct passwd *pwd = getpwnam (argv[optind]);
 204       if (pwd == NULL)
 205         error (EXIT_FAILURE, 0, _("%s: no such user"), argv[optind]);
 206       ruid = euid = pwd->pw_uid;
 207       rgid = egid = pwd->pw_gid;
 208     }
 209   else
 210     {
 211       /* POSIX says identification functions (getuid, getgid, and
 212          others) cannot fail, but they can fail under GNU/Hurd and a
 213          few other systems.  Test for failure by checking errno.  */
 214       uid_t NO_UID = -1;
 215       gid_t NO_GID = -1;
 216
 217       if (just_user ? !use_real
 218           : !just_group && !just_group_list && !just_context)
 219         {
 220           errno = 0;
 221           euid = geteuid ();
 222           if (euid == NO_UID && errno)
 223             error (EXIT_FAILURE, errno, _("cannot get effective UID"));
 224         }
 225
 226       if (just_user ? use_real
 227           : !just_group && (just_group_list || !just_context))
 228         {
 229           errno = 0;
 230           ruid = getuid ();
 231           if (ruid == NO_UID && errno)
 232             error (EXIT_FAILURE, errno, _("cannot get real UID"));
 233         }
 234
 235       if (!just_user && (just_group || just_group_list || !just_context))
 236         {
 237           errno = 0;
 238           egid = getegid ();
 239           if (egid == NO_GID && errno)
 240             error (EXIT_FAILURE, errno, _("cannot get effective GID"));
 241
 242           errno = 0;
 243           rgid = getgid ();
 244           if (rgid == NO_GID && errno)
 245             error (EXIT_FAILURE, errno, _("cannot get real GID"));
 246         }
 247     }
 248
 249   if (just_user)
 250     {
 251       print_user (use_real ? ruid : euid);
 252     }
 253   else if (just_group)
 254     {
 255       if (!print_group (use_real ? rgid : egid, use_name))
 256         ok = false;
 257     }
 258   else if (just_group_list)
 259     {
 260       if (!print_group_list (argv[optind], ruid, rgid, egid, use_name))
 261         ok = false;
 262     }
 263   else if (just_context)
 264     {
 265       fputs (context, stdout);
 266     }
 267   else
 268     {
 269       print_full_info (argv[optind]);
 270     }
 271   putchar ('\n');
 272
 273   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 274 }
 275
 276 /* Print the name or value of user ID UID. */
 277
 278 static void
 279 print_user (uid_t uid)
 280 {
 281   struct passwd *pwd = NULL;
 282
 283   if (use_name)
 284     {
 285       pwd = getpwuid (uid);
 286       if (pwd == NULL)
 287         {
 288           error (0, 0, _("cannot find name for user ID %lu"),
 289                  (unsigned long int) uid);
 290           ok = false;
 291         }
 292     }
 293
 294   if (pwd == NULL)
 295     printf ("%lu", (unsigned long int) uid);
 296   else
 297     printf ("%s", pwd->pw_name);
 298 }
 299
 300 /* Print all of the info about the user's user and group IDs. */
 301
 302 static void
 303 print_full_info (const char *username)
 304 {
 305   struct passwd *pwd;
 306   struct group *grp;
 307
 308   printf (_("uid=%lu"), (unsigned long int) ruid);
 309   pwd = getpwuid (ruid);
 310   if (pwd)
 311     printf ("(%s)", pwd->pw_name);
 312
 313   printf (_(" gid=%lu"), (unsigned long int) rgid);
 314   grp = getgrgid (rgid);
 315   if (grp)
 316     printf ("(%s)", grp->gr_name);
 317
 318   if (euid != ruid)
 319     {
 320       printf (_(" euid=%lu"), (unsigned long int) euid);
 321       pwd = getpwuid (euid);
 322       if (pwd)
 323         printf ("(%s)", pwd->pw_name);
 324     }
 325
 326   if (egid != rgid)
 327     {
 328       printf (_(" egid=%lu"), (unsigned long int) egid);
 329       grp = getgrgid (egid);
 330       if (grp)
 331         printf ("(%s)", grp->gr_name);
 332     }
 333
 334   {
 335     gid_t *groups;
 336     int i;
 337
 338     int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
 339                                &groups);
 340     if (n_groups < 0)
 341       {
 342         if (username)
 343           {
 344             error (0, errno, _("failed to get groups for user %s"),
 345                    quote (username));
 346           }
 347         else
 348           {
 349             error (0, errno, _("failed to get groups for the current process"));
 350           }
 351         ok = false;
 352         return;
 353       }
 354
 355     if (n_groups > 0)
 356       fputs (_(" groups="), stdout);
 357     for (i = 0; i < n_groups; i++)
 358       {
 359         if (i > 0)
 360           putchar (',');
 361         printf ("%lu", (unsigned long int) groups[i]);
 362         grp = getgrgid (groups[i]);
 363         if (grp)
 364           printf ("(%s)", grp->gr_name);
 365       }
 366     free (groups);
 367   }
 368
 369   /* POSIX mandates the precise output format, and that it not include
 370      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 371   if (context)
 372     printf (_(" context=%s"), context);
 373 }