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 */
28
29 #include "namespace.h"
30 #include <sys/param.h>
31 #include <sys/sysctl.h>
32 #include <fcntl.h>
33 #include <signal.h>
34 #include <stdio.h>
35 #include <string.h>
36 #include <syslog.h>
37 #include <unistd.h>
38 #include "un-namespace.h"
39
40 extern int __sys_sigaction(int, const struct sigaction *, struct sigaction *);
41
42 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
43 static void __guard_setup(void) __attribute__ ((constructor));
44 static void __fail(const char *);
45 void __stack_chk_fail(void);
46 void __chk_fail(void);
47
48 static void
__guard_setup(void)49 __guard_setup(void)
50 {
51 int fd;
52 ssize_t size;
53
54 if (__stack_chk_guard[0] != 0)
55 return;
56 if ((fd = _open ("/dev/urandom", 0)) >= 0) {
57 size = _read (fd, (char*)&__stack_chk_guard, sizeof(__stack_chk_guard));
58 _close (fd);
59 if (size == sizeof(__stack_chk_guard))
60 return;
61 }
62
63 /*
64 * If a random generator can't be used, the protector switches the
65 * guard to the "terminator canary"
66 */
67 ((char*)__stack_chk_guard)[0] = 0;
68 ((char*)__stack_chk_guard)[1] = 0;
69 ((char*)__stack_chk_guard)[2] = '\n';
70 ((char*)__stack_chk_guard)[3] = 255;
71 }
72
73 static void
__fail(const char * msg)74 __fail(const char *msg)
75 {
76 struct sigaction sa;
77 sigset_t mask;
78
79 /* Immediately block all signal handlers from running code */
80 sigfillset(&mask);
81 sigdelset(&mask, SIGABRT);
82 _sigprocmask(SIG_BLOCK, &mask, NULL);
83
84 /* This may fail on a chroot jail... */
85 syslog(LOG_CRIT, "%s", msg);
86
87 bzero(&sa, sizeof(struct sigaction));
88 sigemptyset(&sa.sa_mask);
89 sa.sa_flags = 0;
90 sa.sa_handler = SIG_DFL;
91 __sys_sigaction(SIGABRT, &sa, NULL);
92 kill(getpid(), SIGABRT);
93 _exit(127);
94 }
95
96 void
__stack_chk_fail(void)97 __stack_chk_fail(void)
98 {
99 __fail("stack overflow detected; terminated");
100 }
101
102 void
__chk_fail(void)103 __chk_fail(void)
104 {
105 __fail("buffer overflow detected; terminated");
106 }
107
108 #ifndef PIC
109 __weak_reference(__stack_chk_fail, __stack_chk_fail_local);
110 #endif
111