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(const int *name, u_int namelen, void *oldp, 45 size_t *oldlenp, 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 55 __guard_setup(void) 56 { 57 static const int mib[2] = { CTL_KERN, KERN_ARND }; 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 len = sizeof(__stack_chk_guard); 69 if (__sysctl(mib, nitems(mib), __stack_chk_guard, &len, NULL, 0) == 70 -1 || len != sizeof(__stack_chk_guard)) { 71 /* If sysctl was unsuccessful, use the "terminator canary". */ 72 ((unsigned char *)(void *)__stack_chk_guard)[0] = 0; 73 ((unsigned char *)(void *)__stack_chk_guard)[1] = 0; 74 ((unsigned char *)(void *)__stack_chk_guard)[2] = '\n'; 75 ((unsigned char *)(void *)__stack_chk_guard)[3] = 255; 76 } 77 } 78 79 /*ARGSUSED*/ 80 static void 81 __fail(const char *msg) 82 { 83 struct sigaction sa; 84 sigset_t mask; 85 86 /* Immediately block all signal handlers from running code */ 87 (void)sigfillset(&mask); 88 (void)sigdelset(&mask, SIGABRT); 89 (void)sigprocmask(SIG_BLOCK, &mask, NULL); 90 91 /* This may fail on a chroot jail... */ 92 syslog(LOG_CRIT, "%s", msg); 93 94 (void)memset(&sa, 0, sizeof(sa)); 95 (void)sigemptyset(&sa.sa_mask); 96 sa.sa_flags = 0; 97 sa.sa_handler = SIG_DFL; 98 (void)sigaction(SIGABRT, &sa, NULL); 99 (void)kill(getpid(), SIGABRT); 100 _exit(127); 101 } 102 103 void 104 __stack_chk_fail(void) 105 { 106 __fail("stack overflow detected; terminated"); 107 } 108 109 void 110 __chk_fail(void) 111 { 112 __fail("buffer overflow detected; terminated"); 113 } 114 115 #ifndef PIC 116 __weak_reference(__stack_chk_fail, __stack_chk_fail_local); 117 #endif 118