1/* $NetBSD: stack_protector.c,v 1.4 2006/11/22 17:23:25 christos Exp $	*/
2/* $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt Exp $	*/
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/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/param.h>
34#include <sys/sysctl.h>
35#include <sys/types.h>
36#include <errno.h>
37#include <link.h>
38#include <signal.h>
39#include <string.h>
40#include <syslog.h>
41#include <unistd.h>
42#include "libc_private.h"
43
44extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
45    void *newp, size_t newlen);
46
47long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
48static void __guard_setup(void) __attribute__((__constructor__, __used__));
49static void __fail(const char *);
50void __stack_chk_fail(void);
51void __chk_fail(void);
52
53/*LINTED used*/
54static void
55__guard_setup(void)
56{
57	int mib[2];
58	size_t len;
59	int error;
60
61	if (__stack_chk_guard[0] != 0)
62		return;
63	error = _elf_aux_info(AT_CANARY, __stack_chk_guard,
64	    sizeof(__stack_chk_guard));
65	if (error == 0 && __stack_chk_guard[0] != 0)
66		return;
67
68	mib[0] = CTL_KERN;
69	mib[1] = KERN_ARND;
70
71	len = sizeof(__stack_chk_guard);
72	if (__sysctl(mib, 2, __stack_chk_guard, &len, NULL, 0) == -1 ||
73	    len != sizeof(__stack_chk_guard)) {
74		/* If sysctl was unsuccessful, use the "terminator canary". */
75		((unsigned char *)(void *)__stack_chk_guard)[0] = 0;
76		((unsigned char *)(void *)__stack_chk_guard)[1] = 0;
77		((unsigned char *)(void *)__stack_chk_guard)[2] = '\n';
78		((unsigned char *)(void *)__stack_chk_guard)[3] = 255;
79	}
80}
81
82/*ARGSUSED*/
83static void
84__fail(const char *msg)
85{
86	struct sigaction sa;
87	sigset_t mask;
88
89	/* Immediately block all signal handlers from running code */
90	(void)sigfillset(&mask);
91	(void)sigdelset(&mask, SIGABRT);
92	(void)sigprocmask(SIG_BLOCK, &mask, NULL);
93
94	/* This may fail on a chroot jail... */
95	syslog(LOG_CRIT, "%s", msg);
96
97	(void)memset(&sa, 0, sizeof(sa));
98	(void)sigemptyset(&sa.sa_mask);
99	sa.sa_flags = 0;
100	sa.sa_handler = SIG_DFL;
101	(void)sigaction(SIGABRT, &sa, NULL);
102	(void)kill(getpid(), SIGABRT);
103	_exit(127);
104}
105
106void
107__stack_chk_fail(void)
108{
109	__fail("stack overflow detected; terminated");
110}
111
112void
113__chk_fail(void)
114{
115	__fail("buffer overflow detected; terminated");
116}
117
118#ifndef PIC
119__weak_reference(__stack_chk_fail, __stack_chk_fail_local);
120#endif
121