src/id.c

   1 /* id -- print real and effective UIDs and GIDs
   2    Copyright (C) 1989-2017 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 "die.h"
  30 #include "error.h"
  31 #include "mgetgroups.h"
  32 #include "quote.h"
  33 #include "group-list.h"
  34 #include "smack.h"
  35 #include "userspec.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.  */
  45 static bool 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 char *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   {"zero", no_argument, NULL, 'z'},
  73   {GETOPT_HELP_OPTION_DECL},
  74   {GETOPT_VERSION_OPTION_DECL},
  75   {NULL, 0, NULL, 0}
  76 };
  77
  78 void
  79 usage (int status)
  80 {
  81   if (status != EXIT_SUCCESS)
  82     emit_try_help ();
  83   else
  84     {
  85       printf (_("Usage: %s [OPTION]... [USER]\n"), program_name);
  86       fputs (_("\
  87 Print user and group information for the specified USER,\n\
  88 or (when USER omitted) for the current user.\n\
  89 \n"),
  90              stdout);
  91       fputs (_("\
  92   -a             ignore, for compatibility with other versions\n\
  93   -Z, --context  print only the security context of the process\n\
  94   -g, --group    print only the effective group ID\n\
  95   -G, --groups   print all group IDs\n\
  96   -n, --name     print a name instead of a number, for -ugG\n\
  97   -r, --real     print the real ID instead of the effective ID, with -ugG\n\
  98   -u, --user     print only the effective user ID\n\
  99   -z, --zero     delimit entries with NUL characters, not whitespace;\n\
 100                    not permitted in default format\n\
 101 "), stdout);
 102       fputs (HELP_OPTION_DESCRIPTION, stdout);
 103       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 104       fputs (_("\
 105 \n\
 106 Without any OPTION, print some useful set of identified information.\n\
 107 "), stdout);
 108       emit_ancillary_info (PROGRAM_NAME);
 109     }
 110   exit (status);
 111 }
 112
 113 int
 114 main (int argc, char **argv)
 115 {
 116   int optc;
 117   int selinux_enabled = (is_selinux_enabled () > 0);
 118   bool smack_enabled = is_smack_enabled ();
 119   bool opt_zero = false;
 120   char *pw_name = NULL;
 121
 122   /* If true, output the list of all group IDs. -G */
 123   bool just_group_list = false;
 124   /* If true, output only the group ID(s). -g */
 125   bool just_group = false;
 126   /* If true, output real UID/GID instead of default effective UID/GID. -r */
 127   bool use_real = false;
 128   /* If true, output only the user ID(s). -u */
 129   bool just_user = false;
 130
 131   initialize_main (&argc, &argv);
 132   set_program_name (argv[0]);
 133   setlocale (LC_ALL, "");
 134   bindtextdomain (PACKAGE, LOCALEDIR);
 135   textdomain (PACKAGE);
 136
 137   atexit (close_stdout);
 138
 139   while ((optc = getopt_long (argc, argv, "agnruzGZ", longopts, NULL)) != -1)
 140     {
 141       switch (optc)
 142         {
 143         case 'a':
 144           /* Ignore -a, for compatibility with SVR4.  */
 145           break;
 146
 147         case 'Z':
 148           /* politely decline if we're not on a SELinux/SMACK-enabled kernel. */
 149 #ifdef HAVE_SMACK
 150           if (!selinux_enabled && !smack_enabled)
 151             die (EXIT_FAILURE, 0,
 152                  _("--context (-Z) works only on "
 153                    "an SELinux/SMACK-enabled kernel"));
 154 #else
 155           if (!selinux_enabled)
 156             die (EXIT_FAILURE, 0,
 157                  _("--context (-Z) works only on an SELinux-enabled kernel"));
 158 #endif
 159           just_context = true;
 160           break;
 161
 162         case 'g':
 163           just_group = true;
 164           break;
 165         case 'n':
 166           use_name = true;
 167           break;
 168         case 'r':
 169           use_real = true;
 170           break;
 171         case 'u':
 172           just_user = true;
 173           break;
 174         case 'z':
 175           opt_zero = true;
 176           break;
 177         case 'G':
 178           just_group_list = true;
 179           break;
 180         case_GETOPT_HELP_CHAR;
 181         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 182         default:
 183           usage (EXIT_FAILURE);
 184         }
 185     }
 186
 187   size_t n_ids = argc - optind;
 188   if (1 < n_ids)
 189     {
 190       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 191       usage (EXIT_FAILURE);
 192     }
 193
 194   if (n_ids && just_context)
 195     die (EXIT_FAILURE, 0,
 196          _("cannot print security context when user specified"));
 197
 198   if (just_user + just_group + just_group_list + just_context > 1)
 199     die (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));
 200
 201   bool default_format = ! (just_user
 202                            || just_group
 203                            || just_group_list
 204                            || just_context);
 205
 206   if (default_format && (use_real || use_name))
 207     die (EXIT_FAILURE, 0,
 208          _("cannot print only names or real IDs in default format"));
 209
 210   if (default_format && opt_zero)
 211     die (EXIT_FAILURE, 0,
 212          _("option --zero not permitted in default format"));
 213
 214   /* If we are on a SELinux/SMACK-enabled kernel, no user is specified, and
 215      either --context is specified or none of (-u,-g,-G) is specified,
 216      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 217      leave the context variable alone - it has been initialized to an
 218      invalid value that will be not displayed in print_full_info().  */
 219   if (n_ids == 0
 220       && (just_context
 221           || (default_format && ! getenv ("POSIXLY_CORRECT"))))
 222     {
 223       /* Report failure only if --context (-Z) was explicitly requested.  */
 224       if ((selinux_enabled && getcon (&context) && just_context)
 225           || (smack_enabled
 226               && smack_new_label_from_self (&context) < 0
 227               && just_context))
 228         die (EXIT_FAILURE, 0, _("can't get process context"));
 229     }
 230
 231   if (n_ids == 1)
 232     {
 233       struct passwd *pwd = NULL;
 234       const char *spec = argv[optind];
 235       /* Disallow an empty spec here as parse_user_spec() doesn't
 236          give an error for that as it seems it's a valid way to
 237          specify a noop or "reset special bits" depending on the system.  */
 238       if (*spec)
 239         {
 240           if (parse_user_spec (spec, &euid, NULL, NULL, NULL) == NULL)
 241             {
 242               /* parse_user_spec will only extract a numeric spec,
 243                  so we lookup that here to verify and also retrieve
 244                  the PW_NAME used subsequently in group lookup.  */
 245               pwd = getpwuid (euid);
 246             }
 247         }
 248       if (pwd == NULL)
 249         die (EXIT_FAILURE, 0, _("%s: no such user"), quote (spec));
 250       pw_name = xstrdup (pwd->pw_name);
 251       ruid = euid = pwd->pw_uid;
 252       rgid = egid = pwd->pw_gid;
 253     }
 254   else
 255     {
 256       /* POSIX says identification functions (getuid, getgid, and
 257          others) cannot fail, but they can fail under GNU/Hurd and a
 258          few other systems.  Test for failure by checking errno.  */
 259       uid_t NO_UID = -1;
 260       gid_t NO_GID = -1;
 261
 262       if (just_user ? !use_real
 263           : !just_group && !just_group_list && !just_context)
 264         {
 265           errno = 0;
 266           euid = geteuid ();
 267           if (euid == NO_UID && errno)
 268             die (EXIT_FAILURE, errno, _("cannot get effective UID"));
 269         }
 270
 271       if (just_user ? use_real
 272           : !just_group && (just_group_list || !just_context))
 273         {
 274           errno = 0;
 275           ruid = getuid ();
 276           if (ruid == NO_UID && errno)
 277             die (EXIT_FAILURE, errno, _("cannot get real UID"));
 278         }
 279
 280       if (!just_user && (just_group || just_group_list || !just_context))
 281         {
 282           errno = 0;
 283           egid = getegid ();
 284           if (egid == NO_GID && errno)
 285             die (EXIT_FAILURE, errno, _("cannot get effective GID"));
 286
 287           errno = 0;
 288           rgid = getgid ();
 289           if (rgid == NO_GID && errno)
 290             die (EXIT_FAILURE, errno, _("cannot get real GID"));
 291         }
 292     }
 293
 294   if (just_user)
 295     {
 296       print_user (use_real ? ruid : euid);
 297     }
 298   else if (just_group)
 299     {
 300       if (!print_group (use_real ? rgid : egid, use_name))
 301         ok = false;
 302     }
 303   else if (just_group_list)
 304     {
 305       if (!print_group_list (pw_name, ruid, rgid, egid, use_name,
 306                              opt_zero ? '\0' : ' '))
 307         ok = false;
 308     }
 309   else if (just_context)
 310     {
 311       fputs (context, stdout);
 312     }
 313   else
 314     {
 315       print_full_info (pw_name);
 316     }
 317   putchar (opt_zero ? '\0' : '\n');
 318
 319   IF_LINT (free (pw_name));
 320   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 321 }
 322
 323 /* Convert a gid_t to string.  Do not use this function directly.
 324    Instead, use it via the gidtostr macro.
 325    Beware that it returns a pointer to static storage.  */
 326 static char *
 327 gidtostr_ptr (gid_t const *gid)
 328 {
 329   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 330   return umaxtostr (*gid, buf);
 331 }
 332 #define gidtostr(g) gidtostr_ptr (&(g))
 333
 334 /* Convert a uid_t to string.  Do not use this function directly.
 335    Instead, use it via the uidtostr macro.
 336    Beware that it returns a pointer to static storage.  */
 337 static char *
 338 uidtostr_ptr (uid_t const *uid)
 339 {
 340   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 341   return umaxtostr (*uid, buf);
 342 }
 343 #define uidtostr(u) uidtostr_ptr (&(u))
 344
 345 /* Print the name or value of user ID UID. */
 346
 347 static void
 348 print_user (uid_t uid)
 349 {
 350   struct passwd *pwd = NULL;
 351
 352   if (use_name)
 353     {
 354       pwd = getpwuid (uid);
 355       if (pwd == NULL)
 356         {
 357           error (0, 0, _("cannot find name for user ID %s"),
 358                  uidtostr (uid));
 359           ok = false;
 360         }
 361     }
 362
 363   char *s = pwd ? pwd->pw_name : uidtostr (uid);
 364   fputs (s, stdout);
 365 }
 366
 367 /* Print all of the info about the user's user and group IDs. */
 368
 369 static void
 370 print_full_info (const char *username)
 371 {
 372   struct passwd *pwd;
 373   struct group *grp;
 374
 375   printf (_("uid=%s"), uidtostr (ruid));
 376   pwd = getpwuid (ruid);
 377   if (pwd)
 378     printf ("(%s)", pwd->pw_name);
 379
 380   printf (_(" gid=%s"), gidtostr (rgid));
 381   grp = getgrgid (rgid);
 382   if (grp)
 383     printf ("(%s)", grp->gr_name);
 384
 385   if (euid != ruid)
 386     {
 387       printf (_(" euid=%s"), uidtostr (euid));
 388       pwd = getpwuid (euid);
 389       if (pwd)
 390         printf ("(%s)", pwd->pw_name);
 391     }
 392
 393   if (egid != rgid)
 394     {
 395       printf (_(" egid=%s"), gidtostr (egid));
 396       grp = getgrgid (egid);
 397       if (grp)
 398         printf ("(%s)", grp->gr_name);
 399     }
 400
 401   {
 402     gid_t *groups;
 403
 404     gid_t primary_group;
 405     if (username)
 406       primary_group = pwd ? pwd->pw_gid : -1;
 407     else
 408       primary_group = egid;
 409
 410     int n_groups = xgetgroups (username, primary_group, &groups);
 411     if (n_groups < 0)
 412       {
 413         if (username)
 414           error (0, errno, _("failed to get groups for user %s"),
 415                  quote (username));
 416         else
 417           error (0, errno, _("failed to get groups for the current process"));
 418         ok = false;
 419         return;
 420       }
 421
 422     if (n_groups > 0)
 423       fputs (_(" groups="), stdout);
 424     for (int i = 0; i < n_groups; i++)
 425       {
 426         if (i > 0)
 427           putchar (',');
 428         fputs (gidtostr (groups[i]), stdout);
 429         grp = getgrgid (groups[i]);
 430         if (grp)
 431           printf ("(%s)", grp->gr_name);
 432       }
 433     free (groups);
 434   }
 435
 436   /* POSIX mandates the precise output format, and that it not include
 437      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 438   if (context)
 439     printf (_(" context=%s"), context);
 440 }