summaryrefslogtreecommitdiff
path: root/src/id.c
blob: 435d9e8a9848428137a5efa96af9569c73212bb5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
/* id -- print real and effective UIDs and GIDs
   Copyright (C) 1989-2012 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Arnold Robbins.
   Major rewrite by David MacKenzie, djm@gnu.ai.mit.edu. */

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <getopt.h>
#include <selinux/selinux.h>

#include "system.h"
#include "error.h"
#include "mgetgroups.h"
#include "quote.h"
#include "group-list.h"

/* The official name of this program (e.g., no 'g' prefix).  */
#define PROGRAM_NAME "id"

#define AUTHORS \
  proper_name ("Arnold Robbins"), \
  proper_name ("David MacKenzie")

/* If nonzero, output only the SELinux context. -Z */
static int just_context = 0;

static void print_user (uid_t uid);
static void print_full_info (const char *username);

/* If true, output user/group name instead of ID number. -n */
static bool use_name = false;

/* The real and effective IDs of the user to print. */
static uid_t ruid, euid;
static gid_t rgid, egid;

/* True unless errors have been encountered.  */
static bool ok = true;

/* The SELinux context.  Start with a known invalid value so print_full_info
   knows when 'context' has not been set to a meaningful value.  */
static security_context_t context = NULL;

static struct option const longopts[] =
{
  {"context", no_argument, NULL, 'Z'},
  {"group", no_argument, NULL, 'g'},
  {"groups", no_argument, NULL, 'G'},
  {"name", no_argument, NULL, 'n'},
  {"real", no_argument, NULL, 'r'},
  {"user", no_argument, NULL, 'u'},
  {GETOPT_HELP_OPTION_DECL},
  {GETOPT_VERSION_OPTION_DECL},
  {NULL, 0, NULL, 0}
};

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    emit_try_help ();
  else
    {
      printf (_("Usage: %s [OPTION]... [USERNAME]\n"), program_name);
      fputs (_("\
Print user and group information for the specified USERNAME,\n\
or (when USERNAME omitted) for the current user.\n\
\n\
  -a              ignore, for compatibility with other versions\n\
  -Z, --context   print only the security context of the current user\n\
  -g, --group     print only the effective group ID\n\
  -G, --groups    print all group IDs\n\
  -n, --name      print a name instead of a number, for -ugG\n\
  -r, --real      print the real ID instead of the effective ID, with -ugG\n\
  -u, --user      print only the effective user ID\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      fputs (_("\
\n\
Without any OPTION, print some useful set of identified information.\n\
"), stdout);
      emit_ancillary_info ();
    }
  exit (status);
}

int
main (int argc, char **argv)
{
  int optc;
  int selinux_enabled = (is_selinux_enabled () > 0);

  /* If true, output the list of all group IDs. -G */
  bool just_group_list = false;
  /* If true, output only the group ID(s). -g */
  bool just_group = false;
  /* If true, output real UID/GID instead of default effective UID/GID. -r */
  bool use_real = false;
  /* If true, output only the user ID(s). -u */
  bool just_user = false;

  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  while ((optc = getopt_long (argc, argv, "agnruGZ", longopts, NULL)) != -1)
    {
      switch (optc)
        {
        case 'a':
          /* Ignore -a, for compatibility with SVR4.  */
          break;

        case 'Z':
          /* politely decline if we're not on a selinux-enabled kernel. */
          if (!selinux_enabled)
            error (EXIT_FAILURE, 0,
                   _("--context (-Z) works only on an SELinux-enabled kernel"));
          just_context = 1;
          break;

        case 'g':
          just_group = true;
          break;
        case 'n':
          use_name = true;
          break;
        case 'r':
          use_real = true;
          break;
        case 'u':
          just_user = true;
          break;
        case 'G':
          just_group_list = true;
          break;
        case_GETOPT_HELP_CHAR;
        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
        default:
          usage (EXIT_FAILURE);
        }
    }

  size_t n_ids = argc - optind;
  if (1 < n_ids)
    {
      error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
      usage (EXIT_FAILURE);
    }

  if (n_ids && just_context)
    error (EXIT_FAILURE, 0,
           _("cannot print security context when user specified"));

  if (just_user + just_group + just_group_list + just_context > 1)
    error (EXIT_FAILURE, 0, _("cannot print \"only\" of more than one choice"));

  bool default_format = (just_user + just_group + just_group_list
                         + just_context == 0);

  if (default_format && (use_real || use_name))
    error (EXIT_FAILURE, 0,
           _("cannot print only names or real IDs in default format"));

  /* If we are on a selinux-enabled kernel, no user is specified, and
     either --context is specified or none of (-u,-g,-G) is specified,
     and we're not in POSIXLY_CORRECT mode, get our context.  Otherwise,
     leave the context variable alone - it has been initialized to an
     invalid value that will be not displayed in print_full_info().  */
  if (selinux_enabled
      && n_ids == 0
      && (just_context
          || (default_format && ! getenv ("POSIXLY_CORRECT"))))
    {
      /* Report failure only if --context (-Z) was explicitly requested.  */
      if (getcon (&context) && just_context)
        error (EXIT_FAILURE, 0, _("can't get process context"));
    }

  if (n_ids == 1)
    {
      struct passwd *pwd = getpwnam (argv[optind]);
      if (pwd == NULL)
        error (EXIT_FAILURE, 0, _("%s: no such user"), argv[optind]);
      ruid = euid = pwd->pw_uid;
      rgid = egid = pwd->pw_gid;
    }
  else
    {
      /* POSIX says identification functions (getuid, getgid, and
         others) cannot fail, but they can fail under GNU/Hurd and a
         few other systems.  Test for failure by checking errno.  */
      uid_t NO_UID = -1;
      gid_t NO_GID = -1;

      if (just_user ? !use_real
          : !just_group && !just_group_list && !just_context)
        {
          errno = 0;
          euid = geteuid ();
          if (euid == NO_UID && errno)
            error (EXIT_FAILURE, errno, _("cannot get effective UID"));
        }

      if (just_user ? use_real
          : !just_group && (just_group_list || !just_context))
        {
          errno = 0;
          ruid = getuid ();
          if (ruid == NO_UID && errno)
            error (EXIT_FAILURE, errno, _("cannot get real UID"));
        }

      if (!just_user && (just_group || just_group_list || !just_context))
        {
          errno = 0;
          egid = getegid ();
          if (egid == NO_GID && errno)
            error (EXIT_FAILURE, errno, _("cannot get effective GID"));

          errno = 0;
          rgid = getgid ();
          if (rgid == NO_GID && errno)
            error (EXIT_FAILURE, errno, _("cannot get real GID"));
        }
    }

  if (just_user)
    {
      print_user (use_real ? ruid : euid);
    }
  else if (just_group)
    {
      if (!print_group (use_real ? rgid : egid, use_name))
        ok = false;
    }
  else if (just_group_list)
    {
      if (!print_group_list (argv[optind], ruid, rgid, egid, use_name))
        ok = false;
    }
  else if (just_context)
    {
      fputs (context, stdout);
    }
  else
    {
      print_full_info (argv[optind]);
    }
  putchar ('\n');

  exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
}

/* Convert a gid_t to string.  Do not use this function directly.
   Instead, use it via the gidtostr macro.
   Beware that it returns a pointer to static storage.  */
static char *
gidtostr_ptr (gid_t const *gid)
{
  static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
  return umaxtostr (*gid, buf);
}
#define gidtostr(g) gidtostr_ptr (&(g))

/* Convert a uid_t to string.  Do not use this function directly.
   Instead, use it via the uidtostr macro.
   Beware that it returns a pointer to static storage.  */
static char *
uidtostr_ptr (uid_t const *uid)
{
  static char buf[INT_BUFSIZE_BOUND (uintmax_t)];
  return umaxtostr (*uid, buf);
}
#define uidtostr(u) uidtostr_ptr (&(u))

/* Print the name or value of user ID UID. */

static void
print_user (uid_t uid)
{
  struct passwd *pwd = NULL;

  if (use_name)
    {
      pwd = getpwuid (uid);
      if (pwd == NULL)
        {
          error (0, 0, _("cannot find name for user ID %s"),
                 uidtostr (uid));
          ok = false;
        }
    }

  char *s = pwd ? pwd->pw_name : uidtostr (uid);
  fputs (s, stdout);
}

/* Print all of the info about the user's user and group IDs. */

static void
print_full_info (const char *username)
{
  struct passwd *pwd;
  struct group *grp;

  printf (_("uid=%s"), uidtostr (ruid));
  pwd = getpwuid (ruid);
  if (pwd)
    printf ("(%s)", pwd->pw_name);

  printf (_(" gid=%s"), gidtostr (rgid));
  grp = getgrgid (rgid);
  if (grp)
    printf ("(%s)", grp->gr_name);

  if (euid != ruid)
    {
      printf (_(" euid=%s"), uidtostr (euid));
      pwd = getpwuid (euid);
      if (pwd)
        printf ("(%s)", pwd->pw_name);
    }

  if (egid != rgid)
    {
      printf (_(" egid=%s"), gidtostr (egid));
      grp = getgrgid (egid);
      if (grp)
        printf ("(%s)", grp->gr_name);
    }

  {
    gid_t *groups;
    int i;

    int n_groups = xgetgroups (username, (pwd ? pwd->pw_gid : -1),
                               &groups);
    if (n_groups < 0)
      {
        if (username)
          {
            error (0, errno, _("failed to get groups for user %s"),
                   quote (username));
          }
        else
          {
            error (0, errno, _("failed to get groups for the current process"));
          }
        ok = false;
        return;
      }

    if (n_groups > 0)
      fputs (_(" groups="), stdout);
    for (i = 0; i < n_groups; i++)
      {
        if (i > 0)
          putchar (',');
        fputs (gidtostr (groups[i]), stdout);
        grp = getgrgid (groups[i]);
        if (grp)
          printf ("(%s)", grp->gr_name);
      }
    free (groups);
  }

  /* POSIX mandates the precise output format, and that it not include
     any context=... part, so skip that if POSIXLY_CORRECT is set.  */
  if (context)
    printf (_(" context=%s"), context);
}