2 * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
26 * $OpenBSD: stack_protector.c,v 1.3 2002/12/10 08:53:42 etoh Exp $
29 #include "namespace.h"
30 #include <sys/param.h>
31 #include <sys/sysctl.h>
38 #include "un-namespace.h"
40 extern int __sys_sigaction(int, const struct sigaction *, struct sigaction *);
42 static void __guard_setup(void) __attribute__ ((constructor));
43 static void __fail(const char *);
44 void __stack_chk_fail(void);
45 void __chk_fail(void);
46 void __stack_chk_fail_local(void);
48 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
50 /* For compatibility with propolice used by gcc34. */
51 void __stack_smash_handler(char func[], int damaged);
52 extern __typeof(__stack_chk_guard) __guard __attribute__ ((alias ("__stack_chk_guard")));
60 if (__stack_chk_guard[0] != 0)
62 if ((fd = _open ("/dev/urandom", 0)) >= 0) {
63 size = _read (fd, (char*)&__stack_chk_guard, sizeof(__stack_chk_guard));
65 if (size == sizeof(__stack_chk_guard))
70 * If a random generator can't be used, the protector switches the
71 * guard to the "terminator canary"
73 ((char*)__stack_chk_guard)[0] = 0;
74 ((char*)__stack_chk_guard)[1] = 0;
75 ((char*)__stack_chk_guard)[2] = '\n';
76 ((char*)__stack_chk_guard)[3] = 255;
80 __fail(const char *msg)
85 /* Immediately block all signal handlers from running code */
87 sigdelset(&mask, SIGABRT);
88 _sigprocmask(SIG_BLOCK, &mask, NULL);
90 /* This may fail on a chroot jail... */
91 syslog(LOG_CRIT, msg);
93 bzero(&sa, sizeof(struct sigaction));
94 sigemptyset(&sa.sa_mask);
96 sa.sa_handler = SIG_DFL;
97 __sys_sigaction(SIGABRT, &sa, NULL);
99 kill(getpid(), SIGABRT);
105 __stack_smash_handler(char func[], int damaged __unused)
107 static char buf[128];
109 vsnprintf(buf, sizeof(buf), "stack overflow in function %s", func);
114 __stack_chk_fail(void)
116 __fail("stack overflow detected; terminated");
122 __fail("buffer overflow detected; terminated");
126 __stack_chk_fail_local(void)