1 /* $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt 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 #include <sys/param.h> 31 #include <sys/sysctl.h> 32 #include <signal.h> 33 #include <string.h> 34 #include <syslog.h> 35 #include <unistd.h> 36 37 extern int __sysctl(int *, u_int, void *, size_t *, void *, size_t); 38 39 long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0}; 40 static void __guard_setup(void) __attribute__ ((constructor)); 41 void __stack_smash_handler(char func[], int damaged __attribute__((unused))); 42 43 static void 44 __guard_setup(void) 45 { 46 int mib[2]; 47 size_t len; 48 49 if (__guard[0] != 0) 50 return; 51 52 mib[0] = CTL_KERN; 53 mib[1] = KERN_ARND; 54 55 len = sizeof(__guard); 56 if (__sysctl(mib, 2, __guard, &len, NULL, 0) == -1 || 57 len != sizeof(__guard)) { 58 /* If sysctl was unsuccessful, use the "terminator canary". */ 59 ((unsigned char *)__guard)[0] = 0; 60 ((unsigned char *)__guard)[1] = 0; 61 ((unsigned char *)__guard)[2] = '\n'; 62 ((unsigned char *)__guard)[3] = 255; 63 } 64 } 65 66 /*ARGSUSED*/ 67 void 68 __stack_smash_handler(char func[], int damaged) 69 { 70 struct syslog_data sdata = SYSLOG_DATA_INIT; 71 const char message[] = "stack overflow in function %s"; 72 struct sigaction sa; 73 sigset_t mask; 74 75 /* Immediately block all signal handlers from running code */ 76 sigfillset(&mask); 77 sigdelset(&mask, SIGABRT); 78 sigprocmask(SIG_BLOCK, &mask, NULL); 79 80 /* This may fail on a chroot jail... */ 81 syslog_r(LOG_CRIT, &sdata, message, func); 82 83 bzero(&sa, sizeof(struct sigaction)); 84 sigemptyset(&sa.sa_mask); 85 sa.sa_flags = 0; 86 sa.sa_handler = SIG_DFL; 87 sigaction(SIGABRT, &sa, NULL); 88 89 kill(getpid(), SIGABRT); 90 91 _exit(127); 92 } 93