sys/stack_protector-obsd.c

   1 /*
   2  * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  17  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT,
  18  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  19  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  20  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  22  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  23  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  24  * POSSIBILITY OF SUCH DAMAGE.
  25  *
  26  */
  27
  28 #if defined(LIBC_SCCS) && !defined(list)
  29 static char rcsid[] = "$OpenBSD: stack_protector.c,v 1.3 2002/12/10 08:53:42 etoh Exp $";
  30 #endif
  31
  32 #include <sys/param.h>
  33 #include <sys/sysctl.h>
  34 #include <syslog.h>
  35 #include <sys/types.h>
  36 #include <unistd.h>
  37 #include <fcntl.h>
  38
  39 extern void __abort(void) __dead2;
  40 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  41 void __guard_setup(void) __attribute__ ((visibility ("hidden")));
  42 void __stack_chk_fail(void);
  43
  44 void
  45 __guard_setup(void)
  46 {
  47   int fd;
  48   if (__stack_chk_guard[0]!=0) return;
  49   fd = open ("/dev/urandom", 0);
  50   if (fd != -1) {
  51     ssize_t size = read (fd, (char*)&__stack_chk_guard,
  52                          sizeof(__stack_chk_guard));
  53     close (fd) ;
  54     if (size == sizeof(__stack_chk_guard)
  55         && *__stack_chk_guard != 0) return;
  56   }
  57   /* If a random generator can't be used, the protector switches the guard
  58      to the "terminator canary" */
  59   ((char*)__stack_chk_guard)[0] = 0; ((char*)__stack_chk_guard)[1] = 0;
  60   ((char*)__stack_chk_guard)[2] = '\n'; ((char*)__stack_chk_guard)[3] = 255;
  61 }
  62
  63 void
  64 __stack_chk_fail()
  65 {
  66   const char message[] = "[%d] stack overflow";
  67
  68   /* this may fail on a chroot jail, though luck */
  69   syslog(LOG_CRIT, message, getpid());
  70
  71   __abort();
  72 }