stdlib/tst-secure-getenv.c

   1 /* Copyright (C) 2012-2019 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    <https://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 #include <support/support.h>
  34 #include <support/test-driver.h>
  35
  36 static char MAGIC_ARGUMENT[] = "run-actual-test";
  37 #define MAGIC_STATUS 19
  38
  39 /* Return a GID which is not our current GID, but is present in the
  40    supplementary group list.  */
  41 static gid_t
  42 choose_gid (void)
  43 {
  44   int count = getgroups (0, NULL);
  45   if (count < 0)
  46     {
  47       printf ("getgroups: %m\n");
  48       exit (1);
  49     }
  50   gid_t *groups;
  51   groups = xcalloc (count, sizeof (*groups));
  52   int ret = getgroups (count, groups);
  53   if (ret < 0)
  54     {
  55       printf ("getgroups: %m\n");
  56       exit (1);
  57     }
  58   gid_t current = getgid ();
  59   gid_t not_current = 0;
  60   for (int i = 0; i < ret; ++i)
  61     {
  62       if (groups[i] != current)
  63         {
  64           not_current = groups[i];
  65           break;
  66         }
  67     }
  68   free (groups);
  69   return not_current;
  70 }
  71
  72
  73 /* Copies the executable into a restricted directory, so that we can
  74    safely make it SGID with the TARGET group ID.  Then runs the
  75    executable.  */
  76 static int
  77 run_executable_sgid (gid_t target)
  78 {
  79   char *dirname = xasprintf ("%s/secure-getenv.%jd",
  80                              test_dir, (intmax_t) getpid ());
  81   char *execname = xasprintf ("%s/bin", dirname);
  82   int infd = -1;
  83   int outfd = -1;
  84   int ret = -1;
  85   if (mkdir (dirname, 0700) < 0)
  86     {
  87       printf ("mkdir: %m\n");
  88       goto err;
  89     }
  90   infd = open ("/proc/self/exe", O_RDONLY);
  91   if (infd < 0)
  92     {
  93       printf ("open (/proc/self/exe): %m\n");
  94       goto err;
  95     }
  96   outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
  97   if (outfd < 0)
  98     {
  99       printf ("open (%s): %m\n", execname);
 100       goto err;
 101     }
 102   char buf[4096];
 103   for (;;)
 104     {
 105       ssize_t rdcount = read (infd, buf, sizeof (buf));
 106       if (rdcount < 0)
 107         {
 108           printf ("read: %m\n");
 109           goto err;
 110         }
 111       if (rdcount == 0)
 112         break;
 113       char *p = buf;
 114       char *end = buf + rdcount;
 115       while (p != end)
 116         {
 117           ssize_t wrcount = write (outfd, buf, end - p);
 118           if (wrcount == 0)
 119             errno = ENOSPC;
 120           if (wrcount <= 0)
 121             {
 122               printf ("write: %m\n");
 123               goto err;
 124             }
 125           p += wrcount;
 126         }
 127     }
 128   if (fchown (outfd, getuid (), target) < 0)
 129     {
 130       printf ("fchown (%s): %m\n", execname);
 131       goto err;
 132     }
 133   if (fchmod (outfd, 02750) < 0)
 134     {
 135       printf ("fchmod (%s): %m\n", execname);
 136       goto err;
 137     }
 138   if (close (outfd) < 0)
 139     {
 140       printf ("close (outfd): %m\n");
 141       goto err;
 142     }
 143   if (close (infd) < 0)
 144     {
 145       printf ("close (infd): %m\n");
 146       goto err;
 147     }
 148
 149   int kid = fork ();
 150   if (kid < 0)
 151     {
 152       printf ("fork: %m\n");
 153       goto err;
 154     }
 155   if (kid == 0)
 156     {
 157       /* Child process.  */
 158       char *args[] = { execname, MAGIC_ARGUMENT, NULL };
 159       execve (execname, args, environ);
 160       printf ("execve (%s): %m\n", execname);
 161       _exit (1);
 162     }
 163   int status;
 164   if (waitpid (kid, &status, 0) < 0)
 165     {
 166       printf ("waitpid: %m\n");
 167       goto err;
 168     }
 169   if (!WIFEXITED (status) || WEXITSTATUS (status) != MAGIC_STATUS)
 170     {
 171       printf ("Unexpected exit status %d from child process\n",
 172               status);
 173       goto err;
 174     }
 175   ret = 0;
 176
 177 err:
 178   if (outfd >= 0)
 179     close (outfd);
 180   if (infd >= 0)
 181     close (infd);
 182   if (execname)
 183     {
 184       unlink (execname);
 185       free (execname);
 186     }
 187   if (dirname)
 188     {
 189       rmdir (dirname);
 190       free (dirname);
 191     }
 192   return ret;
 193 }
 194
 195 static int
 196 do_test (void)
 197 {
 198   if (getenv ("PATH") == NULL)
 199     {
 200       printf ("PATH not set\n");
 201       exit (1);
 202     }
 203   if (secure_getenv ("PATH") == NULL)
 204     {
 205       printf ("PATH not set according to secure_getenv\n");
 206       exit (1);
 207     }
 208   if (strcmp (getenv ("PATH"), secure_getenv ("PATH")) != 0)
 209     {
 210       printf ("PATH mismatch (%s, %s)\n",
 211               getenv ("PATH"), secure_getenv ("PATH"));
 212       exit (1);
 213     }
 214
 215   gid_t target = choose_gid ();
 216   if (target == 0)
 217     {
 218       fprintf (stderr,
 219                "Could not find a suitable GID for user %jd, skipping test\n",
 220                (intmax_t) getuid ());
 221       exit (0);
 222     }
 223   return run_executable_sgid (target);
 224 }
 225
 226 static void
 227 alternative_main (int argc, char **argv)
 228 {
 229   if (argc == 2 && strcmp (argv[1], MAGIC_ARGUMENT) == 0)
 230     {
 231       if (getgid () == getegid ())
 232         {
 233           /* This can happen if the file system is mounted nosuid.  */
 234           fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
 235                   (intmax_t) getgid ());
 236           exit (MAGIC_STATUS);
 237         }
 238       if (getenv ("PATH") == NULL)
 239         {
 240           printf ("PATH variable not present\n");
 241           exit (3);
 242         }
 243       if (secure_getenv ("PATH") != NULL)
 244         {
 245           printf ("PATH variable not filtered out\n");
 246           exit (4);
 247         }
 248       exit (MAGIC_STATUS);
 249     }
 250 }
 251
 252 #define PREPARE alternative_main
 253 #include <support/test-driver.c>