elf/tst-stackguard1.c

   1 /* Copyright (C) 2005-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Jakub Jelinek <jakub@redhat.com>, 2005.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <stdbool.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/wait.h>
  25 #include <stackguard-macros.h>
  26 #include <tls.h>
  27 #include <unistd.h>
  28
  29 static const char *command;
  30 static bool child;
  31 static uintptr_t stack_chk_guard_copy;
  32 static bool stack_chk_guard_copy_set;
  33 static int fds[2];
  34
  35 static void __attribute__ ((constructor))
  36 con (void)
  37 {
  38   stack_chk_guard_copy = STACK_CHK_GUARD;
  39   stack_chk_guard_copy_set = true;
  40 }
  41
  42 static int
  43 uintptr_t_cmp (const void *a, const void *b)
  44 {
  45   if (*(uintptr_t *) a < *(uintptr_t *) b)
  46     return 1;
  47   if (*(uintptr_t *) a > *(uintptr_t *) b)
  48     return -1;
  49   return 0;
  50 }
  51
  52 static int
  53 do_test (void)
  54 {
  55   if (!stack_chk_guard_copy_set)
  56     {
  57       puts ("constructor has not been run");
  58       return 1;
  59     }
  60
  61   if (stack_chk_guard_copy != STACK_CHK_GUARD)
  62     {
  63       puts ("STACK_CHK_GUARD changed between constructor and do_test");
  64       return 1;
  65     }
  66
  67   if (child)
  68     {
  69       write (2, &stack_chk_guard_copy, sizeof (stack_chk_guard_copy));
  70       return 0;
  71     }
  72
  73   if (command == NULL)
  74     {
  75       puts ("missing --command or --child argument");
  76       return 1;
  77     }
  78
  79 #define N 16
  80   uintptr_t child_stack_chk_guards[N + 1];
  81   child_stack_chk_guards[N] = stack_chk_guard_copy;
  82   int i;
  83   for (i = 0; i < N; ++i)
  84     {
  85       if (pipe (fds) < 0)
  86         {
  87           printf ("couldn't create pipe: %m\n");
  88           return 1;
  89         }
  90
  91       pid_t pid = fork ();
  92       if (pid < 0)
  93         {
  94           printf ("fork failed: %m\n");
  95           return 1;
  96         }
  97
  98       if (!pid)
  99         {
 100           if (stack_chk_guard_copy != STACK_CHK_GUARD)
 101             {
 102               puts ("STACK_CHK_GUARD changed after fork");
 103               exit (1);
 104             }
 105
 106           close (fds[0]);
 107           close (2);
 108           dup2 (fds[1], 2);
 109           close (fds[1]);
 110
 111           system (command);
 112           exit (0);
 113         }
 114
 115       close (fds[1]);
 116
 117       if (TEMP_FAILURE_RETRY (read (fds[0], &child_stack_chk_guards[i],
 118                                     sizeof (uintptr_t))) != sizeof (uintptr_t))
 119         {
 120           puts ("could not read stack_chk_guard value from child");
 121           return 1;
 122         }
 123
 124       close (fds[0]);
 125
 126       pid_t termpid;
 127       int status;
 128       termpid = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
 129       if (termpid == -1)
 130         {
 131           printf ("waitpid failed: %m\n");
 132           return 1;
 133         }
 134       else if (termpid != pid)
 135         {
 136           printf ("waitpid returned %ld != %ld\n",
 137                   (long int) termpid, (long int) pid);
 138           return 1;
 139         }
 140       else if (!WIFEXITED (status) || WEXITSTATUS (status))
 141         {
 142           puts ("child hasn't exited with exit status 0");
 143           return 1;
 144         }
 145     }
 146
 147   qsort (child_stack_chk_guards, N + 1, sizeof (uintptr_t), uintptr_t_cmp);
 148
 149   uintptr_t default_guard = 0;
 150   unsigned char *p = (unsigned char *) &default_guard;
 151   p[sizeof (uintptr_t) - 1] = 255;
 152   p[sizeof (uintptr_t) - 2] = '\n';
 153   p[0] = 0;
 154
 155   /* Test if the stack guard canaries are either randomized,
 156      or equal to the default stack guard canary value.
 157      Even with randomized stack guards it might happen
 158      that the random number generator generates the same
 159      values, but if that happens in more than half from
 160      the 16 runs, something is very wrong.  */
 161   int ndifferences = 0;
 162   int ndefaults = 0;
 163   for (i = 0; i < N; ++i)
 164     {
 165       if (child_stack_chk_guards[i] != child_stack_chk_guards[i+1])
 166         ndifferences++;
 167       else if (child_stack_chk_guards[i] == default_guard)
 168         ndefaults++;
 169     }
 170
 171   printf ("differences %d defaults %d\n", ndifferences, ndefaults);
 172
 173   if (ndifferences < N / 2 && ndefaults < N / 2)
 174     {
 175       puts ("stack guard canaries are not randomized enough");
 176       puts ("nor equal to the default canary value");
 177       return 1;
 178     }
 179
 180   return 0;
 181 }
 182
 183 #define OPT_COMMAND     10000
 184 #define OPT_CHILD       10001
 185 #define CMDLINE_OPTIONS \
 186   { "command", required_argument, NULL, OPT_COMMAND },  \
 187   { "child", no_argument, NULL, OPT_CHILD },
 188 #define CMDLINE_PROCESS \
 189   case OPT_COMMAND:     \
 190     command = optarg;   \
 191     break;              \
 192   case OPT_CHILD:       \
 193     child = true;       \
 194     break;
 195 #define TEST_FUNCTION do_test ()
 196 #include "../test-skeleton.c"