stdlib/tst-secure-getenv.c

   1 /* Copyright (C) 2012-2018 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 #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   const int count = 64;
  45   gid_t groups[count];
  46   int ret = getgroups (count, groups);
  47   if (ret < 0)
  48     {
  49       printf ("getgroups: %m\n");
  50       exit (1);
  51     }
  52   gid_t current = getgid ();
  53   for (int i = 0; i < ret; ++i)
  54     {
  55       if (groups[i] != current)
  56         return groups[i];
  57     }
  58   return 0;
  59 }
  60
  61
  62 /* Copies the executable into a restricted directory, so that we can
  63    safely make it SGID with the TARGET group ID.  Then runs the
  64    executable.  */
  65 static int
  66 run_executable_sgid (gid_t target)
  67 {
  68   char *dirname = xasprintf ("%s/secure-getenv.%jd",
  69                              test_dir, (intmax_t) getpid ());
  70   char *execname = xasprintf ("%s/bin", dirname);
  71   int infd = -1;
  72   int outfd = -1;
  73   int ret = -1;
  74   if (mkdir (dirname, 0700) < 0)
  75     {
  76       printf ("mkdir: %m\n");
  77       goto err;
  78     }
  79   infd = open ("/proc/self/exe", O_RDONLY);
  80   if (infd < 0)
  81     {
  82       printf ("open (/proc/self/exe): %m\n");
  83       goto err;
  84     }
  85   outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
  86   if (outfd < 0)
  87     {
  88       printf ("open (%s): %m\n", execname);
  89       goto err;
  90     }
  91   char buf[4096];
  92   for (;;)
  93     {
  94       ssize_t rdcount = read (infd, buf, sizeof (buf));
  95       if (rdcount < 0)
  96         {
  97           printf ("read: %m\n");
  98           goto err;
  99         }
 100       if (rdcount == 0)
 101         break;
 102       char *p = buf;
 103       char *end = buf + rdcount;
 104       while (p != end)
 105         {
 106           ssize_t wrcount = write (outfd, buf, end - p);
 107           if (wrcount == 0)
 108             errno = ENOSPC;
 109           if (wrcount <= 0)
 110             {
 111               printf ("write: %m\n");
 112               goto err;
 113             }
 114           p += wrcount;
 115         }
 116     }
 117   if (fchown (outfd, getuid (), target) < 0)
 118     {
 119       printf ("fchown (%s): %m\n", execname);
 120       goto err;
 121     }
 122   if (fchmod (outfd, 02750) < 0)
 123     {
 124       printf ("fchmod (%s): %m\n", execname);
 125       goto err;
 126     }
 127   if (close (outfd) < 0)
 128     {
 129       printf ("close (outfd): %m\n");
 130       goto err;
 131     }
 132   if (close (infd) < 0)
 133     {
 134       printf ("close (infd): %m\n");
 135       goto err;
 136     }
 137
 138   int kid = fork ();
 139   if (kid < 0)
 140     {
 141       printf ("fork: %m\n");
 142       goto err;
 143     }
 144   if (kid == 0)
 145     {
 146       /* Child process.  */
 147       char *args[] = { execname, MAGIC_ARGUMENT, NULL };
 148       execve (execname, args, environ);
 149       printf ("execve (%s): %m\n", execname);
 150       _exit (1);
 151     }
 152   int status;
 153   if (waitpid (kid, &status, 0) < 0)
 154     {
 155       printf ("waitpid: %m\n");
 156       goto err;
 157     }
 158   if (!WIFEXITED (status) || WEXITSTATUS (status) != MAGIC_STATUS)
 159     {
 160       printf ("Unexpected exit status %d from child process\n",
 161               status);
 162       goto err;
 163     }
 164   ret = 0;
 165
 166 err:
 167   if (outfd >= 0)
 168     close (outfd);
 169   if (infd >= 0)
 170     close (infd);
 171   if (execname)
 172     {
 173       unlink (execname);
 174       free (execname);
 175     }
 176   if (dirname)
 177     {
 178       rmdir (dirname);
 179       free (dirname);
 180     }
 181   return ret;
 182 }
 183
 184 static int
 185 do_test (void)
 186 {
 187   if (getenv ("PATH") == NULL)
 188     {
 189       printf ("PATH not set\n");
 190       exit (1);
 191     }
 192   if (secure_getenv ("PATH") == NULL)
 193     {
 194       printf ("PATH not set according to secure_getenv\n");
 195       exit (1);
 196     }
 197   if (strcmp (getenv ("PATH"), secure_getenv ("PATH")) != 0)
 198     {
 199       printf ("PATH mismatch (%s, %s)\n",
 200               getenv ("PATH"), secure_getenv ("PATH"));
 201       exit (1);
 202     }
 203
 204   gid_t target = choose_gid ();
 205   if (target == 0)
 206     {
 207       fprintf (stderr,
 208                "Could not find a suitable GID for user %jd, skipping test\n",
 209                (intmax_t) getuid ());
 210       exit (0);
 211     }
 212   return run_executable_sgid (target);
 213 }
 214
 215 static void
 216 alternative_main (int argc, char **argv)
 217 {
 218   if (argc == 2 && strcmp (argv[1], MAGIC_ARGUMENT) == 0)
 219     {
 220       if (getgid () == getegid ())
 221         {
 222           /* This can happen if the file system is mounted nosuid.  */
 223           fprintf (stderr, "SGID failed: GID and EGID match (%jd)\n",
 224                   (intmax_t) getgid ());
 225           exit (MAGIC_STATUS);
 226         }
 227       if (getenv ("PATH") == NULL)
 228         {
 229           printf ("PATH variable not present\n");
 230           exit (3);
 231         }
 232       if (secure_getenv ("PATH") != NULL)
 233         {
 234           printf ("PATH variable not filtered out\n");
 235           exit (4);
 236         }
 237       exit (MAGIC_STATUS);
 238     }
 239 }
 240
 241 #define PREPARE alternative_main
 242 #include <support/test-driver.c>