src/id.c

   1 /* id -- print real and effective UIDs and GIDs
   2    Copyright (C) 1989-2015 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 #include "userspec.h"
  35
  36 /* The official name of this program (e.g., no 'g' prefix).  */
  37 #define PROGRAM_NAME "id"
  38
  39 #define AUTHORS \
  40   proper_name ("Arnold Robbins"), \
  41   proper_name ("David MacKenzie")
  42
  43 /* If nonzero, output only the SELinux context.  */
  44 static bool just_context = 0;
  45
  46 static void print_user (uid_t uid);
  47 static void print_full_info (const char *username);
  48
  49 /* If true, output user/group name instead of ID number. -n */
  50 static bool use_name = false;
  51
  52 /* The real and effective IDs of the user to print. */
  53 static uid_t ruid, euid;
  54 static gid_t rgid, egid;
  55
  56 /* True unless errors have been encountered.  */
  57 static bool ok = true;
  58
  59 /* The SELinux context.  Start with a known invalid value so print_full_info
  60    knows when 'context' has not been set to a meaningful value.  */
  61 static char *context = NULL;
  62
  63 static struct option const longopts[] =
  64 {
  65   {"context", no_argument, NULL, 'Z'},
  66   {"group", no_argument, NULL, 'g'},
  67   {"groups", no_argument, NULL, 'G'},
  68   {"name", no_argument, NULL, 'n'},
  69   {"real", no_argument, NULL, 'r'},
  70   {"user", no_argument, NULL, 'u'},
  71   {"zero", no_argument, NULL, 'z'},
  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]... [USER]\n"), program_name);
  85       fputs (_("\
  86 Print user and group information for the specified USER,\n\
  87 or (when USER omitted) for the current user.\n\
  88 \n"),
  89              stdout);
  90       fputs (_("\
  91   -a             ignore, for compatibility with other versions\n\
  92   -Z, --context  print only the security context of the process\n\
  93   -g, --group    print only the effective group ID\n\
  94   -G, --groups   print all group IDs\n\
  95   -n, --name     print a name instead of a number, for -ugG\n\
  96   -r, --real     print the real ID instead of the effective ID, with -ugG\n\
  97   -u, --user     print only the effective user ID\n\
  98   -z, --zero     delimit entries with NUL characters, not whitespace;\n\
  99                    not permitted in default format\n\
 100 "), stdout);
 101       fputs (HELP_OPTION_DESCRIPTION, stdout);
 102       fputs (VERSION_OPTION_DESCRIPTION, stdout);
 103       fputs (_("\
 104 \n\
 105 Without any OPTION, print some useful set of identified information.\n\
 106 "), stdout);
 107       emit_ancillary_info (PROGRAM_NAME);
 108     }
 109   exit (status);
 110 }
 111
 112 int
 113 main (int argc, char **argv)
 114 {
 115   int optc;
 116   int selinux_enabled = (is_selinux_enabled () > 0);
 117   bool smack_enabled = is_smack_enabled ();
 118   bool opt_zero = false;
 119   char *pw_name = NULL;
 120
 121   /* If true, output the list of all group IDs. -G */
 122   bool just_group_list = false;
 123   /* If true, output only the group ID(s). -g */
 124   bool just_group = false;
 125   /* If true, output real UID/GID instead of default effective UID/GID. -r */
 126   bool use_real = false;
 127   /* If true, output only the user ID(s). -u */
 128   bool just_user = false;
 129
 130   initialize_main (&argc, &argv);
 131   set_program_name (argv[0]);
 132   setlocale (LC_ALL, "");
 133   bindtextdomain (PACKAGE, LOCALEDIR);
 134   textdomain (PACKAGE);
 135
 136   atexit (close_stdout);
 137
 138   while ((optc = getopt_long (argc, argv, "agnruzGZ", longopts, NULL)) != -1)
 139     {
 140       switch (optc)
 141         {
 142         case 'a':
 143           /* Ignore -a, for compatibility with SVR4.  */
 144           break;
 145
 146         case 'Z':
 147           /* politely decline if we're not on a SELinux/SMACK-enabled kernel. */
 148 #ifdef HAVE_SMACK
 149           if (!selinux_enabled && !smack_enabled)
 150             error (EXIT_FAILURE, 0,
 151                    _("--context (-Z) works only on "
 152                      "an SELinux/SMACK-enabled kernel"));
 153 #else
 154           if (!selinux_enabled)
 155             error (EXIT_FAILURE, 0,
 156                    _("--context (-Z) works only on an SELinux-enabled kernel"));
 157 #endif
 158           just_context = true;
 159           break;
 160
 161         case 'g':
 162           just_group = true;
 163           break;
 164         case 'n':
 165           use_name = true;
 166           break;
 167         case 'r':
 168           use_real = true;
 169           break;
 170         case 'u':
 171           just_user = true;
 172           break;
 173         case 'z':
 174           opt_zero = true;
 175           break;
 176         case 'G':
 177           just_group_list = true;
 178           break;
 179         case_GETOPT_HELP_CHAR;
 180         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
 181         default:
 182           usage (EXIT_FAILURE);
 183         }
 184     }
 185
 186   size_t n_ids = argc - optind;
 187   if (1 < n_ids)
 188     {
 189       error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
 190       usage (EXIT_FAILURE);
 191     }
 192
 193   if (n_ids && just_context)
 194     error (EXIT_FAILURE, 0,
 195            _("cannot print security context when user specified"));
 196
 197   if (just_user + just_group + just_group_list + just_context > 1)
 198     error (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));
 199
 200   bool default_format = (just_user + just_group + just_group_list
 201                          + just_context == 0);
 202
 203   if (default_format && (use_real || use_name))
 204     error (EXIT_FAILURE, 0,
 205            _("cannot print only names or real IDs in default format"));
 206
 207   if (default_format && opt_zero)
 208     error (EXIT_FAILURE, 0,
 209            _("option --zero not permitted in default format"));
 210
 211   /* If we are on a SELinux/SMACK-enabled kernel, no user is specified, and
 212      either --context is specified or none of (-u,-g,-G) is specified,
 213      and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
 214      leave the context variable alone - it has been initialized to an
 215      invalid value that will be not displayed in print_full_info().  */
 216   if (n_ids == 0
 217       && (just_context
 218           || (default_format && ! getenv ("POSIXLY_CORRECT"))))
 219     {
 220       /* Report failure only if --context (-Z) was explicitly requested.  */
 221       if ((selinux_enabled && getcon (&context) && just_context)
 222           || (smack_enabled
 223               && smack_new_label_from_self (&context) < 0
 224               && just_context))
 225         error (EXIT_FAILURE, 0, _("can't get process context"));
 226     }
 227
 228   if (n_ids == 1)
 229     {
 230       struct passwd *pwd = NULL;
 231       const char *spec = argv[optind];
 232       /* Disallow an empty spec here as parse_user_spec() doesn't
 233          give an error for that as it seems it's a valid way to
 234          specify a noop or "reset special bits" depending on the system.  */
 235       if (*spec)
 236         {
 237           if (parse_user_spec (spec, &euid, NULL, NULL, NULL) == NULL)
 238             {
 239               /* parse_user_spec will only extract a numeric spec,
 240                  so we lookup that here to verify and also retrieve
 241                  the PW_NAME used subsequently in group lookup.  */
 242               pwd = getpwuid (euid);
 243             }
 244         }
 245       if (pwd == NULL)
 246         error (EXIT_FAILURE, 0, _("%s: no such user"), quote (spec));
 247       pw_name = xstrdup (pwd->pw_name);
 248       ruid = euid = pwd->pw_uid;
 249       rgid = egid = pwd->pw_gid;
 250     }
 251   else
 252     {
 253       /* POSIX says identification functions (getuid, getgid, and
 254          others) cannot fail, but they can fail under GNU/Hurd and a
 255          few other systems.  Test for failure by checking errno.  */
 256       uid_t NO_UID = -1;
 257       gid_t NO_GID = -1;
 258
 259       if (just_user ? !use_real
 260           : !just_group && !just_group_list && !just_context)
 261         {
 262           errno = 0;
 263           euid = geteuid ();
 264           if (euid == NO_UID && errno)
 265             error (EXIT_FAILURE, errno, _("cannot get effective UID"));
 266         }
 267
 268       if (just_user ? use_real
 269           : !just_group && (just_group_list || !just_context))
 270         {
 271           errno = 0;
 272           ruid = getuid ();
 273           if (ruid == NO_UID && errno)
 274             error (EXIT_FAILURE, errno, _("cannot get real UID"));
 275         }
 276
 277       if (!just_user && (just_group || just_group_list || !just_context))
 278         {
 279           errno = 0;
 280           egid = getegid ();
 281           if (egid == NO_GID && errno)
 282             error (EXIT_FAILURE, errno, _("cannot get effective GID"));
 283
 284           errno = 0;
 285           rgid = getgid ();
 286           if (rgid == NO_GID && errno)
 287             error (EXIT_FAILURE, errno, _("cannot get real GID"));
 288         }
 289     }
 290
 291   if (just_user)
 292     {
 293       print_user (use_real ? ruid : euid);
 294     }
 295   else if (just_group)
 296     {
 297       if (!print_group (use_real ? rgid : egid, use_name))
 298         ok = false;
 299     }
 300   else if (just_group_list)
 301     {
 302       if (!print_group_list (pw_name, ruid, rgid, egid, use_name,
 303                              opt_zero ? '\0' : ' '))
 304         ok = false;
 305     }
 306   else if (just_context)
 307     {
 308       fputs (context, stdout);
 309     }
 310   else
 311     {
 312       print_full_info (pw_name);
 313     }
 314   putchar (opt_zero ? '\0' : '\n');
 315
 316   IF_LINT (free (pw_name));
 317   return ok ? EXIT_SUCCESS : EXIT_FAILURE;
 318 }
 319
 320 /* Convert a gid_t to string.  Do not use this function directly.
 321    Instead, use it via the gidtostr macro.
 322    Beware that it returns a pointer to static storage.  */
 323 static char *
 324 gidtostr_ptr (gid_t const *gid)
 325 {
 326   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 327   return umaxtostr (*gid, buf);
 328 }
 329 #define gidtostr(g) gidtostr_ptr (&(g))
 330
 331 /* Convert a uid_t to string.  Do not use this function directly.
 332    Instead, use it via the uidtostr macro.
 333    Beware that it returns a pointer to static storage.  */
 334 static char *
 335 uidtostr_ptr (uid_t const *uid)
 336 {
 337   static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
 338   return umaxtostr (*uid, buf);
 339 }
 340 #define uidtostr(u) uidtostr_ptr (&(u))
 341
 342 /* Print the name or value of user ID UID. */
 343
 344 static void
 345 print_user (uid_t uid)
 346 {
 347   struct passwd *pwd = NULL;
 348
 349   if (use_name)
 350     {
 351       pwd = getpwuid (uid);
 352       if (pwd == NULL)
 353         {
 354           error (0, 0, _("cannot find name for user ID %s"),
 355                  uidtostr (uid));
 356           ok = false;
 357         }
 358     }
 359
 360   char *s = pwd ? pwd->pw_name : uidtostr (uid);
 361   fputs (s, stdout);
 362 }
 363
 364 /* Print all of the info about the user's user and group IDs. */
 365
 366 static void
 367 print_full_info (const char *username)
 368 {
 369   struct passwd *pwd;
 370   struct group *grp;
 371
 372   printf (_("uid=%s"), uidtostr (ruid));
 373   pwd = getpwuid (ruid);
 374   if (pwd)
 375     printf ("(%s)", pwd->pw_name);
 376
 377   printf (_(" gid=%s"), gidtostr (rgid));
 378   grp = getgrgid (rgid);
 379   if (grp)
 380     printf ("(%s)", grp->gr_name);
 381
 382   if (euid != ruid)
 383     {
 384       printf (_(" euid=%s"), uidtostr (euid));
 385       pwd = getpwuid (euid);
 386       if (pwd)
 387         printf ("(%s)", pwd->pw_name);
 388     }
 389
 390   if (egid != rgid)
 391     {
 392       printf (_(" egid=%s"), gidtostr (egid));
 393       grp = getgrgid (egid);
 394       if (grp)
 395         printf ("(%s)", grp->gr_name);
 396     }
 397
 398   {
 399     gid_t *groups;
 400     int i;
 401
 402     gid_t primary_group;
 403     if (username)
 404       primary_group = pwd ? pwd->pw_gid : -1;
 405     else
 406       primary_group = egid;
 407
 408     int n_groups = xgetgroups (username, primary_group, &groups);
 409     if (n_groups < 0)
 410       {
 411         if (username)
 412           error (0, errno, _("failed to get groups for user %s"),
 413                  quote (username));
 414         else
 415           error (0, errno, _("failed to get groups for the current process"));
 416         ok = false;
 417         return;
 418       }
 419
 420     if (n_groups > 0)
 421       fputs (_(" groups="), stdout);
 422     for (i = 0; i < n_groups; i++)
 423       {
 424         if (i > 0)
 425           putchar (',');
 426         fputs (gidtostr (groups[i]), stdout);
 427         grp = getgrgid (groups[i]);
 428         if (grp)
 429           printf ("(%s)", grp->gr_name);
 430       }
 431     free (groups);
 432   }
 433
 434   /* POSIX mandates the precise output format, and that it not include
 435      any context=... part, so skip that if POSIXLY_CORRECT is set.  */
 436   if (context)
 437     printf (_(" context=%s"), context);
 438 }