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