freebsd-nq/lib/libc/secure/stack_protector.c
Konstantin Belousov 989b861f5c Carefully update stack guard bytes inside __guard_setup().
This is necessary to make sure that functions that can have stack
protection are not used to update the stack guard. If not, the stack
guard check would fail when it shouldn't.

guard_setup() calls elf_aux_info(), which, in turn, calls memcpy() to
update stack_chk_guard.  If either elf_aux_info() or memcpy() have
stack protection enabled, __stack_chk_guard will be modified before
returning from them, causing the stack protection check to fail.

This change uses a temporary buffer to delay changing
__stack_chk_guard until elf_aux_info() returns.

Submitted by:	Luis Pires
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D15173
2018-04-24 15:59:39 +00:00

129 lines
4.0 KiB
C

/* $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>
__FBSDID("$FreeBSD$");
#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"
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 __guard_setup(void) __attribute__((__constructor__, __used__));
static void __fail(const char *);
void __stack_chk_fail(void);
void __chk_fail(void);
/*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 len;
int error, idx;
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, (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