lib/libc/sys/stack_protector.c

   1 /* $FreeBSD$ */
   2 /* $NetBSD: stack_protector.c,v 1.4 2006/11/22 17:23:25 christos Exp $  */
   3 /* $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt Exp $ */
   4 /*
   5  * Copyright (c) 2002 Hiroaki Etoh, Federico G. Schwindt, and Miodrag Vallat.
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
  18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  20  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT,
  21  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  23  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  25  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  26  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  27  * POSSIBILITY OF SUCH DAMAGE.
  28  *
  29  */
  30
  31 #include <sys/cdefs.h>
  32 __FBSDID("$FreeBSD$");
  33
  34 #include <sys/param.h>
  35 #include <sys/sysctl.h>
  36 #include <sys/types.h>
  37 #include <signal.h>
  38 #include <string.h>
  39 #include <syslog.h>
  40 #include <unistd.h>
  41
  42 extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
  43     void *newp, size_t newlen);
  44
  45 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  46 static void __guard_setup(void) __attribute__((__constructor__, __used__));
  47 static void __fail(const char *);
  48 void __stack_chk_fail(void);
  49 void __chk_fail(void);
  50 void __stack_chk_fail_local(void);
  51
  52 /*LINTED used*/
  53 static void
  54 __guard_setup(void)
  55 {
  56         int mib[2];
  57         size_t len;
  58
  59         if (__stack_chk_guard[0] != 0)
  60                 return;
  61
  62         mib[0] = CTL_KERN;
  63         mib[1] = KERN_ARND;
  64
  65         len = sizeof(__stack_chk_guard);
  66         if (__sysctl(mib, 2, __stack_chk_guard, &len, NULL, 0) == -1 ||
  67             len != sizeof(__stack_chk_guard)) {
  68                 /* If sysctl was unsuccessful, use the "terminator canary". */
  69                 ((unsigned char *)(void *)__stack_chk_guard)[0] = 0;
  70                 ((unsigned char *)(void *)__stack_chk_guard)[1] = 0;
  71                 ((unsigned char *)(void *)__stack_chk_guard)[2] = '\n';
  72                 ((unsigned char *)(void *)__stack_chk_guard)[3] = 255;
  73         }
  74 }
  75
  76 /*ARGSUSED*/
  77 static void
  78 __fail(const char *msg)
  79 {
  80         struct sigaction sa;
  81         sigset_t mask;
  82
  83         /* Immediately block all signal handlers from running code */
  84         (void)sigfillset(&mask);
  85         (void)sigdelset(&mask, SIGABRT);
  86         (void)sigprocmask(SIG_BLOCK, &mask, NULL);
  87
  88         /* This may fail on a chroot jail... */
  89         syslog(LOG_CRIT, msg);
  90
  91         (void)memset(&sa, 0, sizeof(sa));
  92         (void)sigemptyset(&sa.sa_mask);
  93         sa.sa_flags = 0;
  94         sa.sa_handler = SIG_DFL;
  95         (void)sigaction(SIGABRT, &sa, NULL);
  96         (void)kill(getpid(), SIGABRT);
  97         _exit(127);
  98 }
  99
 100 void
 101 __stack_chk_fail(void)
 102 {
 103         __fail("stack overflow detected; terminated");
 104 }
 105
 106 void
 107 __chk_fail(void)
 108 {
 109         __fail("buffer overflow detected; terminated");
 110 }
 111
 112 void
 113 __stack_chk_fail_local(void)
 114 {
 115         __stack_chk_fail();
 116 }