lib/libc/sys/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  * $OpenBSD: stack_protector.c,v 1.3 2002/12/10 08:53:42 etoh Exp $
  27  * $DragonFly: src/lib/libc/sys/stack_protector.c,v 1.3 2005/11/19 15:19:03 joerg Exp $
  28  */
  29
  30 #include "namespace.h"
  31 #include <sys/param.h>
  32 #include <sys/sysctl.h>
  33 #include <fcntl.h>
  34 #include <signal.h>
  35 #include <string.h>
  36 #include <syslog.h>
  37 #include <unistd.h>
  38 #include "un-namespace.h"
  39
  40 void __stack_smash_handler(char func[], int damaged);
  41 static void __guard_setup(void) __attribute__ ((constructor));
  42
  43 long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  44
  45 static void
  46 __guard_setup(void)
  47 {
  48     int fd;
  49     ssize_t size;
  50
  51     if (__guard[0] != 0)
  52         return;
  53     if ((fd = _open ("/dev/urandom", 0)) >= 0) {
  54         size = _read (fd, (char*)&__guard, sizeof(__guard));
  55         _close (fd);
  56         if (size == sizeof(__guard))
  57             return;
  58     }
  59
  60     /*
  61      * If a random generator can't be used, the protector switches the
  62      * guard to the "terminator canary"
  63      */
  64     ((char*)__guard)[0] = 0;
  65     ((char*)__guard)[1] = 0;
  66     ((char*)__guard)[2] = '\n';
  67     ((char*)__guard)[3] = 255;
  68 }
  69
  70 void
  71 __stack_smash_handler(char func[], int damaged  __unused)
  72 {
  73     static const char message[] = "stack overflow in function %s";
  74     struct sigaction sa;
  75
  76     /* this may fail on a chroot jail, though luck */
  77     syslog(LOG_CRIT, message, func);
  78
  79     bzero(&sa, sizeof(struct sigaction));
  80     sigemptyset(&sa.sa_mask);
  81     sa.sa_flags = 0;
  82     sa.sa_handler = SIG_DFL;
  83     __sys_sigaction(SIGABRT, &sa, NULL);
  84
  85     kill(getpid(), SIGABRT);
  86
  87     _exit(127);
  88 }