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 <errno.h> 36 #include <link.h> 37 #include <signal.h> 38 #include <string.h> 39 #include <syslog.h> 40 #include <unistd.h> 41 #include "libc_private.h" 42 43 extern int __sysctl(const int *name, u_int namelen, void *oldp, 44 size_t *oldlenp, void *newp, size_t newlen); 45 46 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0}; 47 static void __guard_setup(void) __attribute__((__constructor__, __used__)); 48 static void __fail(const char *); 49 void __stack_chk_fail(void); 50 void __chk_fail(void); 51 52 /*LINTED used*/ 53 static void 54 __guard_setup(void) 55 { 56 static const int mib[2] = { CTL_KERN, KERN_ARND }; 57 volatile long tmp_stack_chk_guard[nitems(__stack_chk_guard)]; 58 size_t len; 59 int error, idx; 60 61 if (__stack_chk_guard[0] != 0) 62 return; 63 /* 64 * Avoid using functions which might have stack protection 65 * enabled, to update the __stack_chk_guard. First fetch the 66 * data into a temporal array, then do manual volatile copy to 67 * not allow optimizer to call memcpy() behind us. 68 */ 69 error = _elf_aux_info(AT_CANARY, (void *)tmp_stack_chk_guard, 70 sizeof(tmp_stack_chk_guard)); 71 if (error == 0 && tmp_stack_chk_guard[0] != 0) { 72 for (idx = 0; idx < nitems(__stack_chk_guard); idx++) { 73 __stack_chk_guard[idx] = tmp_stack_chk_guard[idx]; 74 tmp_stack_chk_guard[idx] = 0; 75 } 76 return; 77 } 78 79 len = sizeof(__stack_chk_guard); 80 if (__sysctl(mib, nitems(mib), __stack_chk_guard, &len, NULL, 0) == 81 -1 || len != sizeof(__stack_chk_guard)) { 82 /* If sysctl was unsuccessful, use the "terminator canary". */ 83 ((unsigned char *)(void *)__stack_chk_guard)[0] = 0; 84 ((unsigned char *)(void *)__stack_chk_guard)[1] = 0; 85 ((unsigned char *)(void *)__stack_chk_guard)[2] = '\n'; 86 ((unsigned char *)(void *)__stack_chk_guard)[3] = 255; 87 } 88 } 89 90 /*ARGSUSED*/ 91 static void 92 __fail(const char *msg) 93 { 94 struct sigaction sa; 95 sigset_t mask; 96 97 /* Immediately block all signal handlers from running code */ 98 (void)sigfillset(&mask); 99 (void)sigdelset(&mask, SIGABRT); 100 (void)sigprocmask(SIG_BLOCK, &mask, NULL); 101 102 /* This may fail on a chroot jail... */ 103 syslog(LOG_CRIT, "%s", msg); 104 105 (void)memset(&sa, 0, sizeof(sa)); 106 (void)sigemptyset(&sa.sa_mask); 107 sa.sa_flags = 0; 108 sa.sa_handler = SIG_DFL; 109 (void)sigaction(SIGABRT, &sa, NULL); 110 (void)kill(getpid(), SIGABRT); 111 _exit(127); 112 } 113 114 void 115 __stack_chk_fail(void) 116 { 117 __fail("stack overflow detected; terminated"); 118 } 119 120 void 121 __chk_fail(void) 122 { 123 __fail("buffer overflow detected; terminated"); 124 } 125 126 #ifndef PIC 127 __weak_reference(__stack_chk_fail, __stack_chk_fail_local); 128 #endif 129