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   {"zero", no_argument, NULL, 'z'},
  71   {GETOPT_HELP_OPTION_DECL},
  72   {GETOPT_VERSION_OPTION_DECL},
  73   {NULL, 0, NULL, 0}
  74 };
  75
  76 void
  77 usage (int status)
  78 {
  79   if (status != EXIT_SUCCESS)
  80     emit_try_help ();
  81   else
  82     {
  83       printf (_("Usage: %s [OPTION]... [USERNAME]\n"), program_name);
  84       fputs (_("\
  85 Print user and group information for the specified USERNAME,\n\
  86 or (when USERNAME omitted) for the current user.\n\
  87 \n"),
  88              stdout);
  89       fputs (_("\
  90   -a             ignore, for compatibility with other versions\n\
  91   -Z, --context  print only the security context of the current user\n\
  92   -g, --group    print only the effective group ID\n\
  93   -G, --groups   print all group IDs\n\
  94   -n, --name     print a name instead of a number, for -ugG\n\
  95   -r, --real     print the real ID instead of the effective ID, with -ugG\n\
  96   -u, --user     print only the effective user ID\n\
  97   -z, --zero     delimit entries with NUL characters, not whitespace;\n\
  98                    not permitted in default format\n\
  99 "), stdout);
 100       fputs (HELP_OPTION_DESCRIPTION, stdout);
 101       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 102       fputs (_("\
 103 \n\
 104 Without any OPTION, print some useful set of identified information.\n\
 105 "), stdout);
 106       emit_ancillary_info ();
 107     }
 108   exit (status);
 109 }
 110
 111 int
 112 main (int argc, char **argv)
 113 {
 114   int optc;
 115   int selinux_enabled = (is_selinux_enabled () > 0);
 116   bool smack_enabled = is_smack_enabled ();
 117   bool opt_zero = false;
 118
 119   /* If true, output the list of all group IDs. -G */
 120   bool just_group_list = false;
 121   /* If true, output only the group ID(s). -g */
 122   bool just_group = false;
 123   /* If true, output real UID/GID instead of default effective UID/GID. -r */
 124   bool use_real = false;
 125   /* If true, output only the user ID(s). -u */
 126   bool just_user = false;
 127
 128   initialize_main (&argc, &argv);
 129   set_program_name (argv[0]);
 130   setlocale (LC_ALL, "");
 131   bindtextdomain (PACKAGE, LOCALEDIR);
 132   textdomain (PACKAGE);
 133
 134   atexit (close_stdout);
 135
 136   while ((optc = getopt_long (argc, argv, "agnruzGZ", longopts, NULL)) != -1)
 137     {
 138       switch (optc)
 139         {
 140         case 'a':
 141           /* Ignore -a, for compatibility with SVR4.  */
 142           break;
 143
 144         case 'Z':
 145           /* politely decline if we're not on a SELinux/SMACK-enabled kernel. */
 146 #ifdef HAVE_SMACK
 147           if (!selinux_enabled && !smack_enabled)
 148             error (EXIT_FAILURE, 0,
 149                    _("--context (-Z) works only on "
 150                      "an SELinux/SMACK-enabled kernel"));
 151 #else
 152           if (!selinux_enabled)
 153             error (EXIT_FAILURE, 0,
 154                    _("--context (-Z) works only on an SELinux-enabled kernel"));
 155 #endif
 156           just_context = 1;
 157           break;
 158
 159         case 'g':
 160           just_group = true;
 161           break;
 162         case 'n':
 163           use_name = true;
 164           break;
 165         case 'r':
 166           use_real = true;
 167           break;
 168         case 'u':
 169           just_user = true;
 170           break;
 171         case 'z':
 172           opt_zero = true;
 173           break;
 174         case 'G':
 175           just_group_list = true;
 176           break;
 177         case_GETOPT_HELP_CHAR;
 178         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 179         default:
 180           usage (EXIT_FAILURE);
 181         }
 182     }
 183
 184   size_t n_ids = argc - optind;
 185   if (1 < n_ids)
 186     {
 187       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 188       usage (EXIT_FAILURE);
 189     }
 190
 191   if (n_ids && just_context)
 192     error (EXIT_FAILURE, 0,
 193            _("cannot print security context when user specified"));
 194
 195   if (just_user + just_group + just_group_list + just_context > 1)
 196     error (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));
 197
 198   bool default_format = (just_user + just_group + just_group_list
 199                          + just_context == 0);
 200
 201   if (default_format && (use_real || use_name))
 202     error (EXIT_FAILURE, 0,
 203            _("cannot print only names or real IDs in default format"));
 204
 205   if (default_format && opt_zero)
 206     error (EXIT_FAILURE, 0,
 207            _("option --zero not permitted in default format"));
 208
 209   /* If we are on a SELinux/SMACK-enabled kernel, no user is specified, and
 210      either --context is specified or none of (-u,-g,-G) is specified,
 211      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 212      leave the context variable alone - it has been initialized to an
 213      invalid value that will be not displayed in print_full_info().  */
 214   if (n_ids == 0
 215       && (just_context
 216           || (default_format && ! getenv ("POSIXLY_CORRECT"))))
 217     {
 218       /* Report failure only if --context (-Z) was explicitly requested.  */
 219       if ((selinux_enabled && getcon (&context) && just_context)
 220           || (smack_enabled
 221               && smack_new_label_from_self ((char **) &context) < 0
 222               && just_context))
 223         error (EXIT_FAILURE, 0, _("can't get process context"));
 224     }
 225
 226   if (n_ids == 1)
 227     {
 228       struct passwd *pwd = getpwnam (argv[optind]);
 229       if (pwd == NULL)
 230         error (EXIT_FAILURE, 0, _("%s: no such user"), argv[optind]);
 231       ruid = euid = pwd->pw_uid;
 232       rgid = egid = pwd->pw_gid;
 233     }
 234   else
 235     {
 236       /* POSIX says identification functions (getuid, getgid, and
 237          others) cannot fail, but they can fail under GNU/Hurd and a
 238          few other systems.  Test for failure by checking errno.  */
 239       uid_t NO_UID = -1;
 240       gid_t NO_GID = -1;
 241
 242       if (just_user ? !use_real
 243           : !just_group && !just_group_list && !just_context)
 244         {
 245           errno = 0;
 246           euid = geteuid ();
 247           if (euid == NO_UID && errno)
 248             error (EXIT_FAILURE, errno, _("cannot get effective UID"));
 249         }
 250
 251       if (just_user ? use_real
 252           : !just_group && (just_group_list || !just_context))
 253         {
 254           errno = 0;
 255           ruid = getuid ();
 256           if (ruid == NO_UID && errno)
 257             error (EXIT_FAILURE, errno, _("cannot get real UID"));
 258         }
 259
 260       if (!just_user && (just_group || just_group_list || !just_context))
 261         {
 262           errno = 0;
 263           egid = getegid ();
 264           if (egid == NO_GID && errno)
 265             error (EXIT_FAILURE, errno, _("cannot get effective GID"));
 266
 267           errno = 0;
 268           rgid = getgid ();
 269           if (rgid == NO_GID && errno)
 270             error (EXIT_FAILURE, errno, _("cannot get real GID"));
 271         }
 272     }
 273
 274   if (just_user)
 275     {
 276       print_user (use_real ? ruid : euid);
 277     }
 278   else if (just_group)
 279     {
 280       if (!print_group (use_real ? rgid : egid, use_name))
 281         ok = false;
 282     }
 283   else if (just_group_list)
 284     {
 285       if (!print_group_list (argv[optind], ruid, rgid, egid, use_name,
 286                              opt_zero ? '\0' : ' '))
 287         ok = false;
 288     }
 289   else if (just_context)
 290     {
 291       fputs (context, stdout);
 292     }
 293   else
 294     {
 295       print_full_info (argv[optind]);
 296     }
 297   putchar (opt_zero ? '\0' : '\n');
 298
 299   exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
 300 }
 301
 302 /* Convert a gid_t to string.  Do not use this function directly.
 303    Instead, use it via the gidtostr macro.
 304    Beware that it returns a pointer to static storage.  */
 305 static char *
 306 gidtostr_ptr (gid_t const *gid)
 307 {
 308   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 309   return umaxtostr (*gid, buf);
 310 }
 311 #define gidtostr(g) gidtostr_ptr (&(g))
 312
 313 /* Convert a uid_t to string.  Do not use this function directly.
 314    Instead, use it via the uidtostr macro.
 315    Beware that it returns a pointer to static storage.  */
 316 static char *
 317 uidtostr_ptr (uid_t const *uid)
 318 {
 319   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 320   return umaxtostr (*uid, buf);
 321 }
 322 #define uidtostr(u) uidtostr_ptr (&(u))
 323
 324 /* Print the name or value of user ID UID. */
 325
 326 static void
 327 print_user (uid_t uid)
 328 {
 329   struct passwd *pwd = NULL;
 330
 331   if (use_name)
 332     {
 333       pwd = getpwuid (uid);
 334       if (pwd == NULL)
 335         {
 336           error (0, 0, _("cannot find name for user ID %s"),
 337                  uidtostr (uid));
 338           ok = false;
 339         }
 340     }
 341
 342   char *s = pwd ? pwd->pw_name : uidtostr (uid);
 343   fputs (s, stdout);
 344 }
 345
 346 /* Print all of the info about the user's user and group IDs. */
 347
 348 static void
 349 print_full_info (const char *username)
 350 {
 351   struct passwd *pwd;
 352   struct group *grp;
 353
 354   printf (_("uid=%s"), uidtostr (ruid));
 355   pwd = getpwuid (ruid);
 356   if (pwd)
 357     printf ("(%s)", pwd->pw_name);
 358
 359   printf (_(" gid=%s"), gidtostr (rgid));
 360   grp = getgrgid (rgid);
 361   if (grp)
 362     printf ("(%s)", grp->gr_name);
 363
 364   if (euid != ruid)
 365     {
 366       printf (_(" euid=%s"), uidtostr (euid));
 367       pwd = getpwuid (euid);
 368       if (pwd)
 369         printf ("(%s)", pwd->pw_name);
 370     }
 371
 372   if (egid != rgid)
 373     {
 374       printf (_(" egid=%s"), gidtostr (egid));
 375       grp = getgrgid (egid);
 376       if (grp)
 377         printf ("(%s)", grp->gr_name);
 378     }
 379
 380   {
 381     gid_t *groups;
 382     int i;
 383
 384     int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
 385                                &groups);
 386     if (n_groups < 0)
 387       {
 388         if (username)
 389           {
 390             error (0, errno, _("failed to get groups for user %s"),
 391                    quote (username));
 392           }
 393         else
 394           {
 395             error (0, errno, _("failed to get groups for the current process"));
 396           }
 397         ok = false;
 398         return;
 399       }
 400
 401     if (n_groups > 0)
 402       fputs (_(" groups="), stdout);
 403     for (i = 0; i < n_groups; i++)
 404       {
 405         if (i > 0)
 406           putchar (',');
 407         fputs (gidtostr (groups[i]), stdout);
 408         grp = getgrgid (groups[i]);
 409         if (grp)
 410           printf ("(%s)", grp->gr_name);
 411       }
 412     free (groups);
 413   }
 414
 415   /* POSIX mandates the precise output format, and that it not include
 416      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 417   if (context)
 418     printf (_(" context=%s"), context);
 419 }