1 /* 2 * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 16 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 17 * DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, 18 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 19 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 20 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 22 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 23 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 24 * POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $OpenBSD: stack_protector.c,v 1.3 2002/12/10 08:53:42 etoh Exp $ 27 */ 28 29 #include "namespace.h" 30 #include <sys/param.h> 31 #include <sys/sysctl.h> 32 #include <fcntl.h> 33 #include <signal.h> 34 #include <stdio.h> 35 #include <string.h> 36 #include <syslog.h> 37 #include <unistd.h> 38 #include "un-namespace.h" 39 40 extern int __sys_sigaction(int, const struct sigaction *, struct sigaction *); 41 42 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0}; 43 static void __guard_setup(void) __attribute__ ((constructor)); 44 static void __fail(const char *); 45 void __stack_chk_fail(void); 46 void __chk_fail(void); 47 48 static void 49 __guard_setup(void) 50 { 51 int fd; 52 ssize_t size; 53 54 if (__stack_chk_guard[0] != 0) 55 return; 56 if ((fd = _open ("/dev/urandom", 0)) >= 0) { 57 size = _read (fd, (char*)&__stack_chk_guard, sizeof(__stack_chk_guard)); 58 _close (fd); 59 if (size == sizeof(__stack_chk_guard)) 60 return; 61 } 62 63 /* 64 * If a random generator can't be used, the protector switches the 65 * guard to the "terminator canary" 66 */ 67 ((char*)__stack_chk_guard)[0] = 0; 68 ((char*)__stack_chk_guard)[1] = 0; 69 ((char*)__stack_chk_guard)[2] = '\n'; 70 ((char*)__stack_chk_guard)[3] = 255; 71 } 72 73 static void 74 __fail(const char *msg) 75 { 76 struct sigaction sa; 77 sigset_t mask; 78 79 /* Immediately block all signal handlers from running code */ 80 sigfillset(&mask); 81 sigdelset(&mask, SIGABRT); 82 _sigprocmask(SIG_BLOCK, &mask, NULL); 83 84 /* This may fail on a chroot jail... */ 85 syslog(LOG_CRIT, "%s", msg); 86 87 bzero(&sa, sizeof(struct sigaction)); 88 sigemptyset(&sa.sa_mask); 89 sa.sa_flags = 0; 90 sa.sa_handler = SIG_DFL; 91 __sys_sigaction(SIGABRT, &sa, NULL); 92 kill(getpid(), SIGABRT); 93 _exit(127); 94 } 95 96 void 97 __stack_chk_fail(void) 98 { 99 __fail("stack overflow detected; terminated"); 100 } 101 102 void 103 __chk_fail(void) 104 { 105 __fail("buffer overflow detected; terminated"); 106 } 107 108 #ifndef PIC 109 __weak_reference(__stack_chk_fail, __stack_chk_fail_local); 110 #endif 111