elf/tst-ptrguard1.c

   1 /* Copyright (C) 2013-2017 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 #include <errno.h>
  19 #include <stdbool.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/wait.h>
  24 #include <stackguard-macros.h>
  25 #include <tls.h>
  26 #include <unistd.h>
  27
  28 #ifndef POINTER_CHK_GUARD
  29 extern uintptr_t __pointer_chk_guard;
  30 # define POINTER_CHK_GUARD __pointer_chk_guard
  31 #endif
  32
  33 static const char *command;
  34 static bool child;
  35 static uintptr_t ptr_chk_guard_copy;
  36 static bool ptr_chk_guard_copy_set;
  37 static int fds[2];
  38
  39 static void __attribute__ ((constructor))
  40 con (void)
  41 {
  42   ptr_chk_guard_copy = POINTER_CHK_GUARD;
  43   ptr_chk_guard_copy_set = true;
  44 }
  45
  46 static int
  47 uintptr_t_cmp (const void *a, const void *b)
  48 {
  49   if (*(uintptr_t *) a < *(uintptr_t *) b)
  50     return 1;
  51   if (*(uintptr_t *) a > *(uintptr_t *) b)
  52     return -1;
  53   return 0;
  54 }
  55
  56 static int
  57 do_test (void)
  58 {
  59   if (!ptr_chk_guard_copy_set)
  60     {
  61       puts ("constructor has not been run");
  62       return 1;
  63     }
  64
  65   if (ptr_chk_guard_copy != POINTER_CHK_GUARD)
  66     {
  67       puts ("POINTER_CHK_GUARD changed between constructor and do_test");
  68       return 1;
  69     }
  70
  71   if (child)
  72     {
  73       write (2, &ptr_chk_guard_copy, sizeof (ptr_chk_guard_copy));
  74       return 0;
  75     }
  76
  77   if (command == NULL)
  78     {
  79       puts ("missing --command or --child argument");
  80       return 1;
  81     }
  82
  83 #define N 16
  84   uintptr_t child_ptr_chk_guards[N + 1];
  85   child_ptr_chk_guards[N] = ptr_chk_guard_copy;
  86   int i;
  87   for (i = 0; i < N; ++i)
  88     {
  89       if (pipe (fds) < 0)
  90         {
  91           printf ("couldn't create pipe: %m\n");
  92           return 1;
  93         }
  94
  95       pid_t pid = fork ();
  96       if (pid < 0)
  97         {
  98           printf ("fork failed: %m\n");
  99           return 1;
 100         }
 101
 102       if (!pid)
 103         {
 104           if (ptr_chk_guard_copy != POINTER_CHK_GUARD)
 105             {
 106               puts ("POINTER_CHK_GUARD changed after fork");
 107               exit (1);
 108             }
 109
 110           close (fds[0]);
 111           close (2);
 112           dup2 (fds[1], 2);
 113           close (fds[1]);
 114
 115           system (command);
 116           exit (0);
 117         }
 118
 119       close (fds[1]);
 120
 121       if (TEMP_FAILURE_RETRY (read (fds[0], &child_ptr_chk_guards[i],
 122                                     sizeof (uintptr_t))) != sizeof (uintptr_t))
 123         {
 124           puts ("could not read ptr_chk_guard value from child");
 125           return 1;
 126         }
 127
 128       close (fds[0]);
 129
 130       pid_t termpid;
 131       int status;
 132       termpid = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
 133       if (termpid == -1)
 134         {
 135           printf ("waitpid failed: %m\n");
 136           return 1;
 137         }
 138       else if (termpid != pid)
 139         {
 140           printf ("waitpid returned %ld != %ld\n",
 141                   (long int) termpid, (long int) pid);
 142           return 1;
 143         }
 144       else if (!WIFEXITED (status) || WEXITSTATUS (status))
 145         {
 146           puts ("child hasn't exited with exit status 0");
 147           return 1;
 148         }
 149     }
 150
 151   qsort (child_ptr_chk_guards, N + 1, sizeof (uintptr_t), uintptr_t_cmp);
 152
 153   /* The default pointer guard is the same as the default stack guard.
 154      They are only set to default if dl_random is NULL.  */
 155   uintptr_t default_guard = 0;
 156   unsigned char *p = (unsigned char *) &default_guard;
 157   p[sizeof (uintptr_t) - 1] = 255;
 158   p[sizeof (uintptr_t) - 2] = '\n';
 159   p[0] = 0;
 160
 161   /* Test if the pointer guard canaries are either randomized,
 162      or equal to the default pointer guard value.
 163      Even with randomized pointer guards it might happen
 164      that the random number generator generates the same
 165      values, but if that happens in more than half from
 166      the 16 runs, something is very wrong.  */
 167   int ndifferences = 0;
 168   int ndefaults = 0;
 169   for (i = 0; i < N; ++i)
 170     {
 171       if (child_ptr_chk_guards[i] != child_ptr_chk_guards[i+1])
 172         ndifferences++;
 173       else if (child_ptr_chk_guards[i] == default_guard)
 174         ndefaults++;
 175     }
 176
 177   printf ("differences %d defaults %d\n", ndifferences, ndefaults);
 178
 179   if (ndifferences < N / 2 && ndefaults < N / 2)
 180     {
 181       puts ("pointer guard values are not randomized enough");
 182       puts ("nor equal to the default value");
 183       return 1;
 184     }
 185
 186   return 0;
 187 }
 188
 189 #define OPT_COMMAND     10000
 190 #define OPT_CHILD       10001
 191 #define CMDLINE_OPTIONS \
 192   { "command", required_argument, NULL, OPT_COMMAND },  \
 193   { "child", no_argument, NULL, OPT_CHILD },
 194 #define CMDLINE_PROCESS \
 195   case OPT_COMMAND:     \
 196     command = optarg;   \
 197     break;              \
 198   case OPT_CHILD:       \
 199     child = true;       \
 200     break;
 201 #define TEST_FUNCTION do_test ()
 202 #include "../test-skeleton.c"