elf/tst-ptrguard1.c

   1 /* Copyright (C) 2013-2022 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 #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 _GNU_SOURCE
  29 #define _GNU_SOURCE
  30 #endif
  31 /* Requires _GNU_SOURCE  */
  32 #include <getopt.h>
  33
  34 #ifndef POINTER_CHK_GUARD
  35 extern uintptr_t __pointer_chk_guard;
  36 # define POINTER_CHK_GUARD __pointer_chk_guard
  37 #endif
  38
  39 static const char *command;
  40 static bool child;
  41 static uintptr_t ptr_chk_guard_copy;
  42 static bool ptr_chk_guard_copy_set;
  43 static int fds[2];
  44
  45 static void __attribute__ ((constructor))
  46 con (void)
  47 {
  48   ptr_chk_guard_copy = POINTER_CHK_GUARD;
  49   ptr_chk_guard_copy_set = true;
  50 }
  51
  52 static int
  53 uintptr_t_cmp (const void *a, const void *b)
  54 {
  55   if (*(uintptr_t *) a < *(uintptr_t *) b)
  56     return 1;
  57   if (*(uintptr_t *) a > *(uintptr_t *) b)
  58     return -1;
  59   return 0;
  60 }
  61
  62 static int
  63 do_test (void)
  64 {
  65   if (!ptr_chk_guard_copy_set)
  66     {
  67       puts ("constructor has not been run");
  68       return 1;
  69     }
  70
  71   if (ptr_chk_guard_copy != POINTER_CHK_GUARD)
  72     {
  73       puts ("POINTER_CHK_GUARD changed between constructor and do_test");
  74       return 1;
  75     }
  76
  77   if (child)
  78     {
  79       write (2, &ptr_chk_guard_copy, sizeof (ptr_chk_guard_copy));
  80       return 0;
  81     }
  82
  83   if (command == NULL)
  84     {
  85       puts ("missing --command or --child argument");
  86       return 1;
  87     }
  88
  89 #define N 16
  90   uintptr_t child_ptr_chk_guards[N + 1];
  91   child_ptr_chk_guards[N] = ptr_chk_guard_copy;
  92   int i;
  93   for (i = 0; i < N; ++i)
  94     {
  95       if (pipe (fds) < 0)
  96         {
  97           printf ("couldn't create pipe: %m\n");
  98           return 1;
  99         }
 100
 101       pid_t pid = fork ();
 102       if (pid < 0)
 103         {
 104           printf ("fork failed: %m\n");
 105           return 1;
 106         }
 107
 108       if (!pid)
 109         {
 110           if (ptr_chk_guard_copy != POINTER_CHK_GUARD)
 111             {
 112               puts ("POINTER_CHK_GUARD changed after fork");
 113               exit (1);
 114             }
 115
 116           close (fds[0]);
 117           close (2);
 118           dup2 (fds[1], 2);
 119           close (fds[1]);
 120
 121           system (command);
 122           exit (0);
 123         }
 124
 125       close (fds[1]);
 126
 127       if (TEMP_FAILURE_RETRY (read (fds[0], &child_ptr_chk_guards[i],
 128                                     sizeof (uintptr_t))) != sizeof (uintptr_t))
 129         {
 130           puts ("could not read ptr_chk_guard value from child");
 131           return 1;
 132         }
 133
 134       close (fds[0]);
 135
 136       pid_t termpid;
 137       int status;
 138       termpid = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
 139       if (termpid == -1)
 140         {
 141           printf ("waitpid failed: %m\n");
 142           return 1;
 143         }
 144       else if (termpid != pid)
 145         {
 146           printf ("waitpid returned %ld != %ld\n",
 147                   (long int) termpid, (long int) pid);
 148           return 1;
 149         }
 150       else if (!WIFEXITED (status) || WEXITSTATUS (status))
 151         {
 152           puts ("child hasn't exited with exit status 0");
 153           return 1;
 154         }
 155     }
 156
 157   qsort (child_ptr_chk_guards, N + 1, sizeof (uintptr_t), uintptr_t_cmp);
 158
 159   /* The default pointer guard is the same as the default stack guard.
 160      They are only set to default if dl_random is NULL.  */
 161   uintptr_t default_guard = 0;
 162   unsigned char *p = (unsigned char *) &default_guard;
 163   p[sizeof (uintptr_t) - 1] = 255;
 164   p[sizeof (uintptr_t) - 2] = '\n';
 165   p[0] = 0;
 166
 167   /* Test if the pointer guard canaries are either randomized,
 168      or equal to the default pointer guard value.
 169      Even with randomized pointer guards it might happen
 170      that the random number generator generates the same
 171      values, but if that happens in more than half from
 172      the 16 runs, something is very wrong.  */
 173   int ndifferences = 0;
 174   int ndefaults = 0;
 175   for (i = 0; i < N; ++i)
 176     {
 177       if (child_ptr_chk_guards[i] != child_ptr_chk_guards[i+1])
 178         ndifferences++;
 179       else if (child_ptr_chk_guards[i] == default_guard)
 180         ndefaults++;
 181     }
 182
 183   printf ("differences %d defaults %d\n", ndifferences, ndefaults);
 184
 185   if (ndifferences < N / 2 && ndefaults < N / 2)
 186     {
 187       puts ("pointer guard values are not randomized enough");
 188       puts ("nor equal to the default value");
 189       return 1;
 190     }
 191
 192   return 0;
 193 }
 194
 195 #define OPT_COMMAND     10000
 196 #define OPT_CHILD       10001
 197 #define CMDLINE_OPTIONS \
 198   { "command", required_argument, NULL, OPT_COMMAND },  \
 199   { "child", no_argument, NULL, OPT_CHILD },
 200
 201 static void __attribute((used))
 202 cmdline_process_function (int c)
 203 {
 204   switch (c)
 205     {
 206       case OPT_COMMAND:
 207         command = optarg;
 208         break;
 209       case OPT_CHILD:
 210         child = true;
 211         break;
 212     }
 213 }
 214
 215 #define CMDLINE_PROCESS cmdline_process_function
 216
 217 #include <support/test-driver.c>