sys/OpenBSD/stack_protector.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
  36 long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  37 static void __guard_setup(void) __attribute__ ((constructor));
  38 void __stack_smash_handler(char func[], int damaged __attribute__((unused)));
  39
  40 static void
  41 __guard_setup(void)
  42 {
  43   int fd;
  44   if (__guard[0]!=0) return;
  45   fd = open ("/dev/urandom", 0);
  46   if (fd != -1) {
  47     ssize_t size = read (fd, (char*)&__guard, sizeof(__guard));
  48     close (fd) ;
  49     if (size == sizeof(__guard)) return;
  50   }
  51   /* If a random generator can't be used, the protector switches the guard
  52      to the "terminator canary" */
  53   ((char*)__guard)[0] = 0; ((char*)__guard)[1] = 0;
  54   ((char*)__guard)[2] = '\n'; ((char*)__guard)[3] = 255;
  55 }
  56
  57 void
  58 __stack_smash_handler(char func[], int damaged)
  59 {
  60   const char message[] = "stack overflow in function %s";
  61   struct sigaction sa;
  62
  63   /* this may fail on a chroot jail, though luck */
  64   syslog(LOG_CRIT, message, func);
  65
  66   bzero(&sa, sizeof(struct sigaction));
  67   sigemptyset(&sa.sa_mask);
  68   sa.sa_flags = 0;
  69   sa.sa_handler = SIG_DFL;
  70   sigaction(SIGABRT, &sa, NULL);
  71
  72   kill(getpid(), SIGABRT);
  73
  74   _exit(127);
  75 }