about summary refs log tree commit diff
path: root/elf/tst-env-setuid.c
blob: 41dc79e83a85e082b6e131f1170b9f1e9b7b0a2a (plain) (blame)
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
/* Copyright (C) 2012-2020 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

/* Verify that tunables correctly filter out unsafe environment variables like
   MALLOC_CHECK_ and MALLOC_MMAP_THRESHOLD_ but also retain
   MALLOC_MMAP_THRESHOLD_ in an unprivileged child.  */

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>

#include <support/support.h>
#include <support/test-driver.h>

static char SETGID_CHILD[] = "setgid-child";
#define CHILD_STATUS 42

/* Return a GID which is not our current GID, but is present in the
   supplementary group list.  */
static gid_t
choose_gid (void)
{
  const int count = 64;
  gid_t groups[count];
  int ret = getgroups (count, groups);
  if (ret < 0)
    {
      printf ("getgroups: %m\n");
      exit (1);
    }
  gid_t current = getgid ();
  for (int i = 0; i < ret; ++i)
    {
      if (groups[i] != current)
	return groups[i];
    }
  return 0;
}

/* Spawn and execute a program and verify that it returns the CHILD_STATUS.  */
static pid_t
do_execve (char **args)
{
  pid_t kid = vfork ();

  if (kid < 0)
    {
      printf ("vfork: %m\n");
      return -1;
    }

  if (kid == 0)
    {
      /* Child process.  */
      execve (args[0], args, environ);
      _exit (-errno);
    }

  if (kid < 0)
    return 1;

  int status;

  if (waitpid (kid, &status, 0) < 0)
    {
      printf ("waitpid: %m\n");
      return 1;
    }

  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
    return EXIT_UNSUPPORTED;

  if (!WIFEXITED (status) || WEXITSTATUS (status) != CHILD_STATUS)
    {
      printf ("Unexpected exit status %d from child process\n",
	      WEXITSTATUS (status));
      return 1;
    }
  return 0;
}

/* Copies the executable into a restricted directory, so that we can
   safely make it SGID with the TARGET group ID.  Then runs the
   executable.  */
static int
run_executable_sgid (gid_t target)
{
  char *dirname = xasprintf ("%s/tst-tunables-setuid.%jd",
			     test_dir, (intmax_t) getpid ());
  char *execname = xasprintf ("%s/bin", dirname);
  int infd = -1;
  int outfd = -1;
  int ret = 0;
  if (mkdir (dirname, 0700) < 0)
    {
      printf ("mkdir: %m\n");
      goto err;
    }
  infd = open ("/proc/self/exe", O_RDONLY);
  if (infd < 0)
    {
      printf ("open (/proc/self/exe): %m\n");
      goto err;
    }
  outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
  if (outfd < 0)
    {
      printf ("open (%s): %m\n", execname);
      goto err;
    }
  char buf[4096];
  for (;;)
    {
      ssize_t rdcount = read (infd, buf, sizeof (buf));
      if (rdcount < 0)
	{
	  printf ("read: %m\n");
	  goto err;
	}
      if (rdcount == 0)
	break;
      char *p = buf;
      char *end = buf + rdcount;
      while (p != end)
	{
	  ssize_t wrcount = write (outfd, buf, end - p);
	  if (wrcount == 0)
	    errno = ENOSPC;
	  if (wrcount <= 0)
	    {
	      printf ("write: %m\n");
	      goto err;
	    }
	  p += wrcount;
	}
    }
  if (fchown (outfd, getuid (), target) < 0)
    {
      printf ("fchown (%s): %m\n", execname);
      goto err;
    }
  if (fchmod (outfd, 02750) < 0)
    {
      printf ("fchmod (%s): %m\n", execname);
      goto err;
    }
  if (close (outfd) < 0)
    {
      printf ("close (outfd): %m\n");
      goto err;
    }
  if (close (infd) < 0)
    {
      printf ("close (infd): %m\n");
      goto err;
    }

  char *args[] = {execname, SETGID_CHILD, NULL};

  ret = do_execve (args);

err:
  if (outfd >= 0)
    close (outfd);
  if (infd >= 0)
    close (infd);
  if (execname)
    {
      unlink (execname);
      free (execname);
    }
  if (dirname)
    {
      rmdir (dirname);
      free (dirname);
    }
  return ret;
}

#ifndef test_child
static int
test_child (void)
{
  if (getenv ("MALLOC_CHECK_") != NULL)
    {
      printf ("MALLOC_CHECK_ is still set\n");
      return 1;
    }

  if (getenv ("MALLOC_MMAP_THRESHOLD_") == NULL)
    {
      printf ("MALLOC_MMAP_THRESHOLD_ lost\n");
      return 1;
    }

  if (getenv ("LD_HWCAP_MASK") != NULL)
    {
      printf ("LD_HWCAP_MASK still set\n");
      return 1;
    }

  return 0;
}
#endif

#ifndef test_parent
static int
test_parent (void)
{
  if (getenv ("MALLOC_CHECK_") == NULL)
    {
      printf ("MALLOC_CHECK_ lost\n");
      return 1;
    }

  if (getenv ("MALLOC_MMAP_THRESHOLD_") == NULL)
    {
      printf ("MALLOC_MMAP_THRESHOLD_ lost\n");
      return 1;
    }

  if (getenv ("LD_HWCAP_MASK") == NULL)
    {
      printf ("LD_HWCAP_MASK lost\n");
      return 1;
    }

  return 0;
}
#endif

static int
do_test (int argc, char **argv)
{
  /* Setgid child process.  */
  if (argc == 2 && strcmp (argv[1], SETGID_CHILD) == 0)
    {
      if (getgid () == getegid ())
	{
	  /* This can happen if the file system is mounted nosuid.  */
	  fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
		   (intmax_t) getgid ());
	  exit (EXIT_UNSUPPORTED);
	}

      int ret = test_child ();

      if (ret != 0)
	exit (1);

      exit (CHILD_STATUS);
    }
  else
    {
      if (test_parent () != 0)
	exit (1);

      /* Try running a setgid program.  */
      gid_t target = choose_gid ();
      if (target == 0)
	{
	  fprintf (stderr,
		   "Could not find a suitable GID for user %jd, skipping test\n",
		   (intmax_t) getuid ());
	  exit (0);
	}

      return run_executable_sgid (target);
    }

  /* Something went wrong and our argv was corrupted.  */
  _exit (1);
}

#define TEST_FUNCTION_ARGV do_test
#include <support/test-driver.c>