1 /* $OpenBSD: stack_protector.c,v 1.6 2003/10/01 18:19:08 miod Exp $ */ 2 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 #if defined(LIBC_SCCS) && !defined(list) 31 static char rcsid[] = "$OpenBSD: stack_protector.c,v 1.6 2003/10/01 18:19:08 miod Exp $"; 32 #endif 33 34 #include <sys/param.h> 35 #include <sys/sysctl.h> 36 #include <signal.h> 37 #include <string.h> 38 #include <syslog.h> 39 #include <unistd.h> 40 41 extern int __sysctl(int *, u_int, void *, size_t *, void *, size_t); 42 43 long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0}; 44 static void __guard_setup(void) __attribute__ ((constructor)); 45 void __stack_smash_handler(char func[], int damaged __attribute__((unused))); 46 47 static void 48 __guard_setup(void) 49 { 50 int i, mib[2]; 51 size_t len; 52 53 if (__guard[0] != 0) 54 return; 55 56 mib[0] = CTL_KERN; 57 mib[1] = KERN_ARND; 58 59 len = 4; 60 for (i = 0; i < sizeof(__guard) / 4; i++) { 61 if (__sysctl(mib, 2, (char *)&((int *)__guard)[i], 62 &len, NULL, 0) == -1) 63 break; 64 } 65 66 if (i < sizeof(__guard) / 4) { 67 /* If sysctl was unsuccessful, use the "terminator canary". */ 68 ((char *)__guard)[0] = 0; ((char*)__guard)[1] = 0; 69 ((char *)__guard)[2] = '\n'; ((char *)__guard)[3] = 255; 70 } 71 } 72 73 void 74 __stack_smash_handler(char func[], int damaged) 75 { 76 struct syslog_data sdata = SYSLOG_DATA_INIT; 77 const char message[] = "stack overflow in function %s"; 78 struct sigaction sa; 79 sigset_t mask; 80 81 /* Immediately block all signal handlers from running code */ 82 sigfillset(&mask); 83 sigdelset(&mask, SIGABRT); 84 sigprocmask(SIG_BLOCK, &mask, NULL); 85 86 /* This may fail on a chroot jail... */ 87 syslog_r(LOG_CRIT, &sdata, message, func); 88 89 bzero(&sa, sizeof(struct sigaction)); 90 sigemptyset(&sa.sa_mask); 91 sa.sa_flags = 0; 92 sa.sa_handler = SIG_DFL; 93 sigaction(SIGABRT, &sa, NULL); 94 95 kill(getpid(), SIGABRT); 96 97 _exit(127); 98 } 99