/* * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * */ #if defined(LIBC_SCCS) && !defined(list) static char rcsid[] = "$OpenBSD: stack_protector.c,v 1.3 2002/12/10 08:53:42 etoh Exp $"; #endif #include <sys/param.h> #include <sys/sysctl.h> #include <syslog.h> #include <sys/types.h> #include <unistd.h> #include <fcntl.h> extern void __abort(void) __dead2; long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0}; void __guard_setup(void) __attribute__ ((visibility ("hidden"))); void __stack_chk_fail(void); void __guard_setup(void) { int fd; if (__stack_chk_guard[0]!=0) return; fd = open ("/dev/urandom", 0); if (fd != -1) { ssize_t size = read (fd, (char*)&__stack_chk_guard, sizeof(__stack_chk_guard)); close (fd) ; if (size == sizeof(__stack_chk_guard) && *__stack_chk_guard != 0) return; } /* If a random generator can't be used, the protector switches the guard to the "terminator canary" */ ((char*)__stack_chk_guard)[0] = 0; ((char*)__stack_chk_guard)[1] = 0; ((char*)__stack_chk_guard)[2] = '\n'; ((char*)__stack_chk_guard)[3] = 255; } void __stack_chk_fail() { const char message[] = "[%d] stack overflow"; /* this may fail on a chroot jail, though luck */ syslog(LOG_CRIT, message, getpid()); __abort(); }