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