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 #ifdef HAVE_SMACK
  28 # include <sys/smack.h>
  29 #endif
  30
  31 #include "system.h"
  32 #include "error.h"
  33 #include "mgetgroups.h"
  34 #include "quote.h"
  35 #include "group-list.h"
  36
  37 /* The official name of this program (e.g., no 'g' prefix).  */
  38 #define PROGRAM_NAME "id"
  39
  40 #define AUTHORS \
  41   proper_name ("Arnold Robbins"), \
  42   proper_name ("David MacKenzie")
  43
  44 /* If nonzero, output only the SELinux context. -Z */
  45 static int just_context = 0;
  46
  47 static void print_user (uid_t uid);
  48 static void print_full_info (const char *username);
  49
  50 /* If true, output user/group name instead of ID number. -n */
  51 static bool use_name = false;
  52
  53 /* The real and effective IDs of the user to print. */
  54 static uid_t ruid, euid;
  55 static gid_t rgid, egid;
  56
  57 /* True unless errors have been encountered.  */
  58 static bool ok = true;
  59
  60 /* The SELinux context.  Start with a known invalid value so print_full_info
  61    knows when 'context' has not been set to a meaningful value.  */
  62 static security_context_t context = NULL;
  63
  64 static struct option const longopts[] =
  65 {
  66   {"context", no_argument, NULL, 'Z'},
  67   {"group", no_argument, NULL, 'g'},
  68   {"groups", no_argument, NULL, 'G'},
  69   {"name", no_argument, NULL, 'n'},
  70   {"real", no_argument, NULL, 'r'},
  71   {"user", no_argument, NULL, 'u'},
  72   {GETOPT_HELP_OPTION_DECL},
  73   {GETOPT_VERSION_OPTION_DECL},
  74   {NULL, 0, NULL, 0}
  75 };
  76
  77 void
  78 usage (int status)
  79 {
  80   if (status != EXIT_SUCCESS)
  81     emit_try_help ();
  82   else
  83     {
  84       printf (_("Usage: %s [OPTION]... [USERNAME]\n"), program_name);
  85       fputs (_("\
  86 Print user and group information for the specified USERNAME,\n\
  87 or (when USERNAME omitted) for the current user.\n\
  88 \n\
  89   -a              ignore, for compatibility with other versions\n\
  90   -Z, --context   print only the security context of the current user\n\
  91   -g, --group     print only the effective group ID\n\
  92   -G, --groups    print all group IDs\n\
  93   -n, --name      print a name instead of a number, for -ugG\n\
  94   -r, --real      print the real ID instead of the effective ID, with -ugG\n\
  95   -u, --user      print only the effective user ID\n\
  96 "), stdout);
  97       fputs (HELP_OPTION_DESCRIPTION, stdout);
  98       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  99       fputs (_("\
 100 \n\
 101 Without any OPTION, print some useful set of identified information.\n\
 102 "), stdout);
 103       emit_ancillary_info ();
 104     }
 105   exit (status);
 106 }
 107
 108 int
 109 main (int argc, char **argv)
 110 {
 111   int optc;
 112   int selinux_enabled = (is_selinux_enabled () > 0);
 113 #ifdef HAVE_SMACK
 114   int smack_enabled = (smack_smackfs_path () != NULL);
 115 #endif
 116
 117   /* If true, output the list of all group IDs. -G */
 118   bool just_group_list = false;
 119   /* If true, output only the group ID(s). -g */
 120   bool just_group = false;
 121   /* If true, output real UID/GID instead of default effective UID/GID. -r */
 122   bool use_real = false;
 123   /* If true, output only the user ID(s). -u */
 124   bool just_user = false;
 125
 126   initialize_main (&argc, &argv);
 127   set_program_name (argv[0]);
 128   setlocale (LC_ALL, "");
 129   bindtextdomain (PACKAGE, LOCALEDIR);
 130   textdomain (PACKAGE);
 131
 132   atexit (close_stdout);
 133
 134   while ((optc = getopt_long (argc, argv, "agnruGZ", longopts, NULL)) != -1)
 135     {
 136       switch (optc)
 137         {
 138         case 'a':
 139           /* Ignore -a, for compatibility with SVR4.  */
 140           break;
 141
 142         case 'Z':
 143           /* politely decline if we're not on a SELinux/SMACK-enabled kernel. */
 144 #ifdef HAVE_SMACK
 145           if (!selinux_enabled && !smack_enabled)
 146             error (EXIT_FAILURE, 0,
 147                    _("--context (-Z) works only on "
 148                      "an SELinux/SMACK-enabled kernel"));
 149 #else
 150           if (!selinux_enabled)
 151             error (EXIT_FAILURE, 0,
 152                    _("--context (-Z) works only on an SELinux-enabled kernel"));
 153 #endif
 154           just_context = 1;
 155           break;
 156
 157         case 'g':
 158           just_group = true;
 159           break;
 160         case 'n':
 161           use_name = true;
 162           break;
 163         case 'r':
 164           use_real = true;
 165           break;
 166         case 'u':
 167           just_user = true;
 168           break;
 169         case 'G':
 170           just_group_list = true;
 171           break;
 172         case_GETOPT_HELP_CHAR;
 173         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 174         default:
 175           usage (EXIT_FAILURE);
 176         }
 177     }
 178
 179   size_t n_ids = argc - optind;
 180   if (1 < n_ids)
 181     {
 182       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 183       usage (EXIT_FAILURE);
 184     }
 185
 186   if (n_ids && just_context)
 187     error (EXIT_FAILURE, 0,
 188            _("cannot print security context when user specified"));
 189
 190   if (just_user + just_group + just_group_list + just_context > 1)
 191     error (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));
 192
 193   bool default_format = (just_user + just_group + just_group_list
 194                          + just_context == 0);
 195
 196   if (default_format && (use_real || use_name))
 197     error (EXIT_FAILURE, 0,
 198            _("cannot print only names or real IDs in default format"));
 199
 200   /* If we are on a selinux-enabled kernel, no user is specified, and
 201      either --context is specified or none of (-u,-g,-G) is specified,
 202      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 203      leave the context variable alone - it has been initialized to an
 204      invalid value that will be not displayed in print_full_info().  */
 205   if (n_ids == 0
 206       && (just_context
 207           || (default_format && ! getenv ("POSIXLY_CORRECT"))))
 208     {
 209       /* Report failure only if --context (-Z) was explicitly requested.  */
 210       if (selinux_enabled && getcon (&context) && just_context)
 211         error (EXIT_FAILURE, 0, _("can't get process context"));
 212 #ifdef HAVE_SMACK
 213       else if (smack_enabled
 214                && smack_new_label_from_self ((char **) &context) < 0)
 215         error (EXIT_FAILURE, 0, _("can't get process context"));
 216 #endif
 217     }
 218
 219   if (n_ids == 1)
 220     {
 221       struct passwd *pwd = getpwnam (argv[optind]);
 222       if (pwd == NULL)
 223         error (EXIT_FAILURE, 0, _("%s: no such user"), argv[optind]);
 224       ruid = euid = pwd->pw_uid;
 225       rgid = egid = pwd->pw_gid;
 226     }
 227   else
 228     {
 229       /* POSIX says identification functions (getuid, getgid, and
 230          others) cannot fail, but they can fail under GNU/Hurd and a
 231          few other systems.  Test for failure by checking errno.  */
 232       uid_t NO_UID = -1;
 233       gid_t NO_GID = -1;
 234
 235       if (just_user ? !use_real
 236           : !just_group && !just_group_list && !just_context)
 237         {
 238           errno = 0;
 239           euid = geteuid ();
 240           if (euid == NO_UID && errno)
 241             error (EXIT_FAILURE, errno, _("cannot get effective UID"));
 242         }
 243
 244       if (just_user ? use_real
 245           : !just_group && (just_group_list || !just_context))
 246         {
 247           errno = 0;
 248           ruid = getuid ();
 249           if (ruid == NO_UID && errno)
 250             error (EXIT_FAILURE, errno, _("cannot get real UID"));
 251         }
 252
 253       if (!just_user && (just_group || just_group_list || !just_context))
 254         {
 255           errno = 0;
 256           egid = getegid ();
 257           if (egid == NO_GID && errno)
 258             error (EXIT_FAILURE, errno, _("cannot get effective GID"));
 259
 260           errno = 0;
 261           rgid = getgid ();
 262           if (rgid == NO_GID && errno)
 263             error (EXIT_FAILURE, errno, _("cannot get real GID"));
 264         }
 265     }
 266
 267   if (just_user)
 268     {
 269       print_user (use_real ? ruid : euid);
 270     }
 271   else if (just_group)
 272     {
 273       if (!print_group (use_real ? rgid : egid, use_name))
 274         ok = false;
 275     }
 276   else if (just_group_list)
 277     {
 278       if (!print_group_list (argv[optind], ruid, rgid, egid, use_name))
 279         ok = false;
 280     }
 281   else if (just_context)
 282     {
 283       fputs (context, stdout);
 284     }
 285   else
 286     {
 287       print_full_info (argv[optind]);
 288     }
 289   putchar ('\n');
 290
 291   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 292 }
 293
 294 /* Convert a gid_t to string.  Do not use this function directly.
 295    Instead, use it via the gidtostr macro.
 296    Beware that it returns a pointer to static storage.  */
 297 static char *
 298 gidtostr_ptr (gid_t const *gid)
 299 {
 300   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 301   return umaxtostr (*gid, buf);
 302 }
 303 #define gidtostr(g) gidtostr_ptr (&(g))
 304
 305 /* Convert a uid_t to string.  Do not use this function directly.
 306    Instead, use it via the uidtostr macro.
 307    Beware that it returns a pointer to static storage.  */
 308 static char *
 309 uidtostr_ptr (uid_t const *uid)
 310 {
 311   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 312   return umaxtostr (*uid, buf);
 313 }
 314 #define uidtostr(u) uidtostr_ptr (&(u))
 315
 316 /* Print the name or value of user ID UID. */
 317
 318 static void
 319 print_user (uid_t uid)
 320 {
 321   struct passwd *pwd = NULL;
 322
 323   if (use_name)
 324     {
 325       pwd = getpwuid (uid);
 326       if (pwd == NULL)
 327         {
 328           error (0, 0, _("cannot find name for user ID %s"),
 329                  uidtostr (uid));
 330           ok = false;
 331         }
 332     }
 333
 334   char *s = pwd ? pwd->pw_name : uidtostr (uid);
 335   fputs (s, stdout);
 336 }
 337
 338 /* Print all of the info about the user's user and group IDs. */
 339
 340 static void
 341 print_full_info (const char *username)
 342 {
 343   struct passwd *pwd;
 344   struct group *grp;
 345
 346   printf (_("uid=%s"), uidtostr (ruid));
 347   pwd = getpwuid (ruid);
 348   if (pwd)
 349     printf ("(%s)", pwd->pw_name);
 350
 351   printf (_(" gid=%s"), gidtostr (rgid));
 352   grp = getgrgid (rgid);
 353   if (grp)
 354     printf ("(%s)", grp->gr_name);
 355
 356   if (euid != ruid)
 357     {
 358       printf (_(" euid=%s"), uidtostr (euid));
 359       pwd = getpwuid (euid);
 360       if (pwd)
 361         printf ("(%s)", pwd->pw_name);
 362     }
 363
 364   if (egid != rgid)
 365     {
 366       printf (_(" egid=%s"), gidtostr (egid));
 367       grp = getgrgid (egid);
 368       if (grp)
 369         printf ("(%s)", grp->gr_name);
 370     }
 371
 372   {
 373     gid_t *groups;
 374     int i;
 375
 376     int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
 377                                &groups);
 378     if (n_groups < 0)
 379       {
 380         if (username)
 381           {
 382             error (0, errno, _("failed to get groups for user %s"),
 383                    quote (username));
 384           }
 385         else
 386           {
 387             error (0, errno, _("failed to get groups for the current process"));
 388           }
 389         ok = false;
 390         return;
 391       }
 392
 393     if (n_groups > 0)
 394       fputs (_(" groups="), stdout);
 395     for (i = 0; i < n_groups; i++)
 396       {
 397         if (i > 0)
 398           putchar (',');
 399         fputs (gidtostr (groups[i]), stdout);
 400         grp = getgrgid (groups[i]);
 401         if (grp)
 402           printf ("(%s)", grp->gr_name);
 403       }
 404     free (groups);
 405   }
 406
 407   /* POSIX mandates the precise output format, and that it not include
 408      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 409   if (context)
 410     printf (_(" context=%s"), context);
 411 }