src/id.c

   1 /* id -- print real and effective UIDs and GIDs
   2    Copyright (C) 1989-2013 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
 181                          + just_context == 0);
 182
 183   if (default_format && (use_real || use_name))
 184     error (EXIT_FAILURE, 0,
 185            _("cannot print only names or real IDs in default format"));
 186
 187   /* If we are on a selinux-enabled kernel, no user is specified, and
 188      either --context is specified or none of (-u,-g,-G) is specified,
 189      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 190      leave the context variable alone - it has been initialized to an
 191      invalid value that will be not displayed in print_full_info().  */
 192   if (selinux_enabled
 193       && n_ids == 0
 194       && (just_context
 195           || (default_format && ! getenv ("POSIXLY_CORRECT"))))
 196     {
 197       /* Report failure only if --context (-Z) was explicitly requested.  */
 198       if (getcon (&context) && just_context)
 199         error (EXIT_FAILURE, 0, _("can't get process context"));
 200     }
 201
 202   if (n_ids == 1)
 203     {
 204       struct passwd *pwd = getpwnam (argv[optind]);
 205       if (pwd == NULL)
 206         error (EXIT_FAILURE, 0, _("%s: no such user"), argv[optind]);
 207       ruid = euid = pwd->pw_uid;
 208       rgid = egid = pwd->pw_gid;
 209     }
 210   else
 211     {
 212       /* POSIX says identification functions (getuid, getgid, and
 213          others) cannot fail, but they can fail under GNU/Hurd and a
 214          few other systems.  Test for failure by checking errno.  */
 215       uid_t NO_UID = -1;
 216       gid_t NO_GID = -1;
 217
 218       if (just_user ? !use_real
 219           : !just_group && !just_group_list && !just_context)
 220         {
 221           errno = 0;
 222           euid = geteuid ();
 223           if (euid == NO_UID && errno)
 224             error (EXIT_FAILURE, errno, _("cannot get effective UID"));
 225         }
 226
 227       if (just_user ? use_real
 228           : !just_group && (just_group_list || !just_context))
 229         {
 230           errno = 0;
 231           ruid = getuid ();
 232           if (ruid == NO_UID && errno)
 233             error (EXIT_FAILURE, errno, _("cannot get real UID"));
 234         }
 235
 236       if (!just_user && (just_group || just_group_list || !just_context))
 237         {
 238           errno = 0;
 239           egid = getegid ();
 240           if (egid == NO_GID && errno)
 241             error (EXIT_FAILURE, errno, _("cannot get effective GID"));
 242
 243           errno = 0;
 244           rgid = getgid ();
 245           if (rgid == NO_GID && errno)
 246             error (EXIT_FAILURE, errno, _("cannot get real GID"));
 247         }
 248     }
 249
 250   if (just_user)
 251     {
 252       print_user (use_real ? ruid : euid);
 253     }
 254   else if (just_group)
 255     {
 256       if (!print_group (use_real ? rgid : egid, use_name))
 257         ok = false;
 258     }
 259   else if (just_group_list)
 260     {
 261       if (!print_group_list (argv[optind], ruid, rgid, egid, use_name))
 262         ok = false;
 263     }
 264   else if (just_context)
 265     {
 266       fputs (context, stdout);
 267     }
 268   else
 269     {
 270       print_full_info (argv[optind]);
 271     }
 272   putchar ('\n');
 273
 274   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 275 }
 276
 277 /* Convert a gid_t to string.  Do not use this function directly.
 278    Instead, use it via the gidtostr macro.
 279    Beware that it returns a pointer to static storage.  */
 280 static char *
 281 gidtostr_ptr (gid_t const *gid)
 282 {
 283   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 284   return umaxtostr (*gid, buf);
 285 }
 286 #define gidtostr(g) gidtostr_ptr (&(g))
 287
 288 /* Convert a uid_t to string.  Do not use this function directly.
 289    Instead, use it via the uidtostr macro.
 290    Beware that it returns a pointer to static storage.  */
 291 static char *
 292 uidtostr_ptr (uid_t const *uid)
 293 {
 294   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 295   return umaxtostr (*uid, buf);
 296 }
 297 #define uidtostr(u) uidtostr_ptr (&(u))
 298
 299 /* Print the name or value of user ID UID. */
 300
 301 static void
 302 print_user (uid_t uid)
 303 {
 304   struct passwd *pwd = NULL;
 305
 306   if (use_name)
 307     {
 308       pwd = getpwuid (uid);
 309       if (pwd == NULL)
 310         {
 311           error (0, 0, _("cannot find name for user ID %s"),
 312                  uidtostr (uid));
 313           ok = false;
 314         }
 315     }
 316
 317   char *s = pwd ? pwd->pw_name : uidtostr (uid);
 318   fputs (s, stdout);
 319 }
 320
 321 /* Print all of the info about the user's user and group IDs. */
 322
 323 static void
 324 print_full_info (const char *username)
 325 {
 326   struct passwd *pwd;
 327   struct group *grp;
 328
 329   printf (_("uid=%s"), uidtostr (ruid));
 330   pwd = getpwuid (ruid);
 331   if (pwd)
 332     printf ("(%s)", pwd->pw_name);
 333
 334   printf (_(" gid=%s"), gidtostr (rgid));
 335   grp = getgrgid (rgid);
 336   if (grp)
 337     printf ("(%s)", grp->gr_name);
 338
 339   if (euid != ruid)
 340     {
 341       printf (_(" euid=%s"), uidtostr (euid));
 342       pwd = getpwuid (euid);
 343       if (pwd)
 344         printf ("(%s)", pwd->pw_name);
 345     }
 346
 347   if (egid != rgid)
 348     {
 349       printf (_(" egid=%s"), gidtostr (egid));
 350       grp = getgrgid (egid);
 351       if (grp)
 352         printf ("(%s)", grp->gr_name);
 353     }
 354
 355   {
 356     gid_t *groups;
 357     int i;
 358
 359     int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
 360                                &groups);
 361     if (n_groups < 0)
 362       {
 363         if (username)
 364           {
 365             error (0, errno, _("failed to get groups for user %s"),
 366                    quote (username));
 367           }
 368         else
 369           {
 370             error (0, errno, _("failed to get groups for the current process"));
 371           }
 372         ok = false;
 373         return;
 374       }
 375
 376     if (n_groups > 0)
 377       fputs (_(" groups="), stdout);
 378     for (i = 0; i < n_groups; i++)
 379       {
 380         if (i > 0)
 381           putchar (',');
 382         fputs (gidtostr (groups[i]), stdout);
 383         grp = getgrgid (groups[i]);
 384         if (grp)
 385           printf ("(%s)", grp->gr_name);
 386       }
 387     free (groups);
 388   }
 389
 390   /* POSIX mandates the precise output format, and that it not include
 391      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 392   if (context)
 393     printf (_(" context=%s"), context);
 394 }