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
44 extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
45 void *newp, size_t newlen);
46
47 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
48 static void __guard_setup(void) __attribute__((__constructor__, __used__));
49 static void __fail(const char *);
50 void __stack_chk_fail(void);
51 void __chk_fail(void);
52
53 /*LINTED used*/
54 static void
__guard_setup(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*/
83 static void
__fail(const char * msg)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
106 void
__stack_chk_fail(void)107 __stack_chk_fail(void)
108 {
109 __fail("stack overflow detected; terminated");
110 }
111
112 void
__chk_fail(void)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