contrib/gcc-5.0/libssp/ssp.c

   1 /* Stack protector support.
   2    Copyright (C) 2005-2013 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file into combinations with other programs,
  14 and to distribute those combinations without any restriction coming
  15 from the use of this file.  (The General Public License restrictions
  16 do apply in other respects; for example, they cover modification of
  17 the file, and distribution when not linked into a combine
  18 executable.)
  19
  20 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  21 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  22 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  23 for more details.
  24
  25 Under Section 7 of GPL version 3, you are granted additional
  26 permissions described in the GCC Runtime Library Exception, version
  27 3.1, as published by the Free Software Foundation.
  28
  29 You should have received a copy of the GNU General Public License and
  30 a copy of the GCC Runtime Library Exception along with this program;
  31 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  32 <http://www.gnu.org/licenses/>.  */
  33
  34
  35 #include "config.h"
  36 #ifdef HAVE_ALLOCA_H
  37 # include <alloca.h>
  38 #endif
  39 #ifdef HAVE_MALLOC_H
  40 # include <malloc.h>
  41 #else
  42 # include <stdlib.h>
  43 #endif
  44 #ifdef HAVE_STRING_H
  45 # include <string.h>
  46 #endif
  47 #ifdef HAVE_UNISTD_H
  48 # include <unistd.h>
  49 #endif
  50 #ifdef HAVE_FCNTL_H
  51 # include <fcntl.h>
  52 #endif
  53 #ifdef HAVE_PATHS_H
  54 # include <paths.h>
  55 #endif
  56 #ifndef _PATH_TTY
  57 /* Native win32 apps don't know about /dev/tty but can print directly
  58    to the console using  "CONOUT$"   */
  59 #if defined (_WIN32) && !defined (__CYGWIN__)
  60 #include <windows.h>
  61 # define _PATH_TTY "CONOUT$"
  62 #else
  63 # define _PATH_TTY "/dev/tty"
  64 #endif
  65 #endif
  66 #ifdef HAVE_SYSLOG_H
  67 # include <syslog.h>
  68 #endif
  69
  70 void *__stack_chk_guard = 0;
  71
  72 static void __attribute__ ((constructor))
  73 __guard_setup (void)
  74 {
  75   unsigned char *p;
  76   int fd;
  77
  78   if (__stack_chk_guard != 0)
  79     return;
  80
  81 #if defined (_WIN32) && !defined (__CYGWIN__)
  82   HCRYPTPROV hprovider = 0;
  83   if (CryptAcquireContext(&hprovider, NULL, NULL, PROV_RSA_FULL,
  84                           CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
  85     {
  86       if (CryptGenRandom(hprovider, sizeof (__stack_chk_guard),
  87           (BYTE *)&__stack_chk_guard) &&  __stack_chk_guard != 0)
  88         {
  89            CryptReleaseContext(hprovider, 0);
  90            return;
  91         }
  92       CryptReleaseContext(hprovider, 0);
  93     }
  94 #else
  95   fd = open ("/dev/urandom", O_RDONLY);
  96   if (fd != -1)
  97     {
  98       ssize_t size = read (fd, &__stack_chk_guard,
  99                            sizeof (__stack_chk_guard));
 100       close (fd);
 101       if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0)
 102         return;
 103     }
 104
 105 #endif
 106   /* If a random generator can't be used, the protector switches the guard
 107      to the "terminator canary".  */
 108   p = (unsigned char *) &__stack_chk_guard;
 109   p[sizeof(__stack_chk_guard)-1] = 255;
 110   p[sizeof(__stack_chk_guard)-2] = '\n';
 111   p[0] = 0;
 112 }
 113
 114 static void
 115 fail (const char *msg1, size_t msg1len, const char *msg3)
 116 {
 117 #ifdef __GNU_LIBRARY__
 118   extern char * __progname;
 119 #else
 120   static const char __progname[] = "";
 121 #endif
 122   int fd;
 123
 124   /* Print error message directly to the tty.  This avoids Bad Things
 125      happening if stderr is redirected.  */
 126   fd = open (_PATH_TTY, O_WRONLY);
 127   if (fd != -1)
 128     {
 129       static const char msg2[] = " terminated\n";
 130       size_t progname_len, len;
 131       char *buf, *p;
 132
 133       progname_len = strlen (__progname);
 134       len = msg1len + progname_len + sizeof(msg2)-1 + 1;
 135       p = buf = alloca (len);
 136
 137       memcpy (p, msg1, msg1len);
 138       p += msg1len;
 139       memcpy (p, __progname, progname_len);
 140       p += progname_len;
 141       memcpy (p, msg2, sizeof(msg2));
 142
 143       while (len > 0)
 144         {
 145           ssize_t wrote = write (fd, buf, len);
 146           if (wrote < 0)
 147             break;
 148           buf += wrote;
 149           len -= wrote;
 150         }
 151       close (fd);
 152     }
 153
 154 #ifdef HAVE_SYSLOG_H
 155   /* Only send the error to syslog if there was no tty available.  */
 156   else
 157     syslog (LOG_CRIT, "%s", msg3);
 158 #endif /* HAVE_SYSLOG_H */
 159
 160   /* Try very hard to exit.  Note that signals may be blocked preventing
 161      the first two options from working.  The use of volatile is here to
 162      prevent optimizers from "knowing" that __builtin_trap is called first,
 163      and that it doesn't return, and so "obviously" the rest of the code
 164      is dead.  */
 165   {
 166     volatile int state;
 167     for (state = 0; ; state++)
 168       switch (state)
 169         {
 170         case 0:
 171           __builtin_trap ();
 172           break;
 173         case 1:
 174           *(volatile int *)-1L = 0;
 175           break;
 176         case 2:
 177           _exit (127);
 178           break;
 179         }
 180   }
 181 }
 182
 183 void
 184 __stack_chk_fail (void)
 185 {
 186   const char *msg = "*** stack smashing detected ***: ";
 187   fail (msg, strlen (msg), "stack smashing detected: terminated");
 188 }
 189
 190 void
 191 __chk_fail (void)
 192 {
 193   const char *msg = "*** buffer overflow detected ***: ";
 194   fail (msg, strlen (msg), "buffer overflow detected: terminated");
 195 }
 196
 197 #ifdef HAVE_HIDDEN_VISIBILITY
 198 void
 199 __attribute__((visibility ("hidden")))
 200 __stack_chk_fail_local (void)
 201 {
 202   __stack_chk_fail ();
 203 }
 204 #endif