sys/OpenBSD/stack_protector.c

   1 /*      $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt Exp $    */
   2
   3 /*
   4  * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT,
  20  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  24  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  25  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  26  * POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  */
  29
  30 #include <sys/param.h>
  31 #include <sys/sysctl.h>
  32 #include <signal.h>
  33 #include <string.h>
  34 #include <syslog.h>
  35 #include <unistd.h>
  36
  37 extern int __sysctl(int *, u_int, void *, size_t *, void *, size_t);
  38
  39 long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  40 static void __guard_setup(void) __attribute__ ((constructor));
  41 void __stack_smash_handler(char func[], int damaged __attribute__((unused)));
  42
  43 static void
  44 __guard_setup(void)
  45 {
  46         int mib[2];
  47         size_t len;
  48
  49         if (__guard[0] != 0)
  50                 return;
  51
  52         mib[0] = CTL_KERN;
  53         mib[1] = KERN_ARND;
  54
  55         len = sizeof(__guard);
  56         if (__sysctl(mib, 2, __guard, &len, NULL, 0) == -1 ||
  57             len != sizeof(__guard)) {
  58                 /* If sysctl was unsuccessful, use the "terminator canary". */
  59                 ((unsigned char *)__guard)[0] = 0;
  60                 ((unsigned char *)__guard)[1] = 0;
  61                 ((unsigned char *)__guard)[2] = '\n';
  62                 ((unsigned char *)__guard)[3] = 255;
  63         }
  64 }
  65
  66 /*ARGSUSED*/
  67 void
  68 __stack_smash_handler(char func[], int damaged)
  69 {
  70         struct syslog_data sdata = SYSLOG_DATA_INIT;
  71         const char message[] = "stack overflow in function %s";
  72         struct sigaction sa;
  73         sigset_t mask;
  74
  75         /* Immediately block all signal handlers from running code */
  76         sigfillset(&mask);
  77         sigdelset(&mask, SIGABRT);
  78         sigprocmask(SIG_BLOCK, &mask, NULL);
  79
  80         /* This may fail on a chroot jail... */
  81         syslog_r(LOG_CRIT, &sdata, message, func);
  82
  83         bzero(&sa, sizeof(struct sigaction));
  84         sigemptyset(&sa.sa_mask);
  85         sa.sa_flags = 0;
  86         sa.sa_handler = SIG_DFL;
  87         sigaction(SIGABRT, &sa, NULL);
  88
  89         kill(getpid(), SIGABRT);
  90
  91         _exit(127);
  92 }