stdlib/tst-secure-getenv.c

   1 /* Copyright (C) 2012-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 /* Test that secure_getenv works by invoking the test as a SGID
  19    program with a group ID from the supplementary group list.  This
  20    test can fail spuriously if the user is not a member of a suitable
  21    supplementary group.  */
  22
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <stdlib.h>
  26 #include <stdint.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <sys/stat.h>
  30 #include <sys/wait.h>
  31 #include <unistd.h>
  32
  33 static char MAGIC_ARGUMENT[] = "run-actual-test";
  34 #define MAGIC_STATUS 19
  35
  36 static const char *test_dir;
  37
  38 /* Return a GID which is not our current GID, but is present in the
  39    supplementary group list.  */
  40 static gid_t
  41 choose_gid (void)
  42 {
  43   const int count = 64;
  44   gid_t groups[count];
  45   int ret = getgroups (count, groups);
  46   if (ret < 0)
  47     {
  48       printf ("getgroups: %m\n");
  49       exit (1);
  50     }
  51   gid_t current = getgid ();
  52   for (int i = 0; i < ret; ++i)
  53     {
  54       if (groups[i] != current)
  55         return groups[i];
  56     }
  57   return 0;
  58 }
  59
  60
  61 /* Copies the executable into a restricted directory, so that we can
  62    safely make it SGID with the TARGET group ID.  Then runs the
  63    executable.  */
  64 static int
  65 run_executable_sgid (gid_t target)
  66 {
  67   char *dirname = 0;
  68   char *execname = 0;
  69   int infd = -1;
  70   int outfd = -1;
  71   int ret = -1;
  72   if (asprintf (&dirname, "%s/secure-getenv.%jd",
  73                 test_dir, (intmax_t) getpid ()) < 0)
  74     {
  75       printf ("asprintf: %m\n");
  76       goto err;
  77     }
  78   if (mkdir (dirname, 0700) < 0)
  79     {
  80       printf ("mkdir: %m\n");
  81       goto err;
  82     }
  83   if (asprintf (&execname, "%s/bin", dirname) < 0)
  84     {
  85       printf ("asprintf: %m\n");
  86       goto err;
  87     }
  88   infd = open ("/proc/self/exe", O_RDONLY);
  89   if (infd < 0)
  90     {
  91       printf ("open (/proc/self/exe): %m\n");
  92       goto err;
  93     }
  94   outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
  95   if (outfd < 0)
  96     {
  97       printf ("open (%s): %m\n", execname);
  98       goto err;
  99     }
 100   char buf[4096];
 101   for (;;)
 102     {
 103       ssize_t rdcount = read (infd, buf, sizeof (buf));
 104       if (rdcount < 0)
 105         {
 106           printf ("read: %m\n");
 107           goto err;
 108         }
 109       if (rdcount == 0)
 110         break;
 111       char *p = buf;
 112       char *end = buf + rdcount;
 113       while (p != end)
 114         {
 115           ssize_t wrcount = write (outfd, buf, end - p);
 116           if (wrcount == 0)
 117             errno = ENOSPC;
 118           if (wrcount <= 0)
 119             {
 120               printf ("write: %m\n");
 121               goto err;
 122             }
 123           p += wrcount;
 124         }
 125     }
 126   if (fchown (outfd, getuid (), target) < 0)
 127     {
 128       printf ("fchown (%s): %m\n", execname);
 129       goto err;
 130     }
 131   if (fchmod (outfd, 02750) < 0)
 132     {
 133       printf ("fchmod (%s): %m\n", execname);
 134       goto err;
 135     }
 136   if (close (outfd) < 0)
 137     {
 138       printf ("close (outfd): %m\n");
 139       goto err;
 140     }
 141   if (close (infd) < 0)
 142     {
 143       printf ("close (infd): %m\n");
 144       goto err;
 145     }
 146
 147   int kid = fork ();
 148   if (kid < 0)
 149     {
 150       printf ("fork: %m\n");
 151       goto err;
 152     }
 153   if (kid == 0)
 154     {
 155       /* Child process.  */
 156       char *args[] = { execname, MAGIC_ARGUMENT, NULL };
 157       execve (execname, args, environ);
 158       printf ("execve (%s): %m\n", execname);
 159       _exit (1);
 160     }
 161   int status;
 162   if (waitpid (kid, &status, 0) < 0)
 163     {
 164       printf ("waitpid: %m\n");
 165       goto err;
 166     }
 167   if (!WIFEXITED (status) || WEXITSTATUS (status) != MAGIC_STATUS)
 168     {
 169       printf ("Unexpected exit status %d from child process\n",
 170               status);
 171       goto err;
 172     }
 173   ret = 0;
 174
 175 err:
 176   if (outfd >= 0)
 177     close (outfd);
 178   if (infd >= 0)
 179     close (infd);
 180   if (execname)
 181     {
 182       unlink (execname);
 183       free (execname);
 184     }
 185   if (dirname)
 186     {
 187       rmdir (dirname);
 188       free (dirname);
 189     }
 190   return ret;
 191 }
 192
 193 static int
 194 do_test (void)
 195 {
 196   if (getenv ("PATH") == NULL)
 197     {
 198       printf ("PATH not set\n");
 199       exit (1);
 200     }
 201   if (secure_getenv ("PATH") == NULL)
 202     {
 203       printf ("PATH not set according to secure_getenv\n");
 204       exit (1);
 205     }
 206   if (strcmp (getenv ("PATH"), secure_getenv ("PATH")) != 0)
 207     {
 208       printf ("PATH mismatch (%s, %s)\n",
 209               getenv ("PATH"), secure_getenv ("PATH"));
 210       exit (1);
 211     }
 212
 213   gid_t target = choose_gid ();
 214   if (target == 0)
 215     {
 216       fprintf (stderr,
 217                "Could not find a suitable GID for user %jd, skipping test\n",
 218                (intmax_t) getuid ());
 219       exit (0);
 220     }
 221   return run_executable_sgid (target);
 222 }
 223
 224 static void
 225 alternative_main (int argc, char **argv)
 226 {
 227   if (argc == 2 && strcmp (argv[1], MAGIC_ARGUMENT) == 0)
 228     {
 229       if (getgid () == getegid ())
 230         {
 231           /* This can happen if the file system is mounted nosuid.  */
 232           fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
 233                   (intmax_t) getgid ());
 234           exit (MAGIC_STATUS);
 235         }
 236       if (getenv ("PATH") == NULL)
 237         {
 238           printf ("PATH variable not present\n");
 239           exit (3);
 240         }
 241       if (secure_getenv ("PATH") != NULL)
 242         {
 243           printf ("PATH variable not filtered out\n");
 244           exit (4);
 245         }
 246       exit (MAGIC_STATUS);
 247     }
 248 }
 249
 250 #define PREPARE(argc, argv) alternative_main(argc, argv)
 251 #define TEST_FUNCTION do_test ()
 252 #include "../test-skeleton.c"