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/* $NetBSD: stack_protector.c,v 1.4 2006/11/22 17:23:25 christos Exp $ */
/* $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt Exp $ */
/*
* Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <sys/cdefs.h>
#include <sys/param.h>
#include <sys/sysctl.h>
#include <errno.h>
#include <link.h>
#include <signal.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "libc_private.h"
/*
* We give __guard_setup a defined priority early on so that statically linked
* applications have a defined priority at which __stack_chk_guard will be
* getting initialized. This will not matter to most applications, because
* they're either not usually statically linked or they simply don't do things
* in constructors that would be adversely affected by their positioning with
* respect to this initialization.
*/
static void __guard_setup(void)
__attribute__((__constructor__ (200), __used__));
extern long __stack_chk_guard[8];
extern int __sysctl(const int *name, u_int namelen, void *oldp,
size_t *oldlenp, void *newp, size_t newlen);
long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
static void __fail(const char *) __dead2;
void __stack_chk_fail(void) __dead2;
void __chk_fail(void) __dead2;
/*LINTED used*/
static void
__guard_setup(void)
{
static const int mib[2] = { CTL_KERN, KERN_ARND };
volatile long tmp_stack_chk_guard[nitems(__stack_chk_guard)];
size_t idx, len;
int error;
if (__stack_chk_guard[0] != 0)
return;
/*
* Avoid using functions which might have stack protection
* enabled, to update the __stack_chk_guard. First fetch the
* data into a temporal array, then do manual volatile copy to
* not allow optimizer to call memcpy() behind us.
*/
error = _elf_aux_info(AT_CANARY,
__DEQUALIFY(void *, tmp_stack_chk_guard),
sizeof(tmp_stack_chk_guard));
if (error == 0 && tmp_stack_chk_guard[0] != 0) {
for (idx = 0; idx < nitems(__stack_chk_guard); idx++) {
__stack_chk_guard[idx] = tmp_stack_chk_guard[idx];
tmp_stack_chk_guard[idx] = 0;
}
return;
}
len = sizeof(__stack_chk_guard);
if (__sysctl(mib, nitems(mib), __stack_chk_guard, &len, NULL, 0) ==
-1 || len != sizeof(__stack_chk_guard)) {
/* If sysctl was unsuccessful, use the "terminator canary". */
((unsigned char *)(void *)__stack_chk_guard)[0] = 0;
((unsigned char *)(void *)__stack_chk_guard)[1] = 0;
((unsigned char *)(void *)__stack_chk_guard)[2] = '\n';
((unsigned char *)(void *)__stack_chk_guard)[3] = 255;
}
}
/*ARGSUSED*/
static void
__fail(const char *msg)
{
struct sigaction sa;
sigset_t mask;
/* Immediately block all signal handlers from running code */
(void)sigfillset(&mask);
(void)sigdelset(&mask, SIGABRT);
(void)sigprocmask(SIG_BLOCK, &mask, NULL);
/* This may fail on a chroot jail... */
syslog(LOG_CRIT, "%s", msg);
(void)memset(&sa, 0, sizeof(sa));
(void)sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = SIG_DFL;
(void)sigaction(SIGABRT, &sa, NULL);
(void)kill(getpid(), SIGABRT);
_exit(127);
}
void
__stack_chk_fail(void)
{
__fail("stack overflow detected; terminated");
}
void
__chk_fail(void)
{
__fail("buffer overflow detected; terminated");
}
#ifndef PIC
__weak_reference(__stack_chk_fail, __stack_chk_fail_local);
#endif
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