lib/libc/misc/stack_protector.c

   1 /*      $NetBSD: stack_protector.c,v 1.3 2009/01/30 23:21:02 ad Exp $   */
   2 /*      $OpenBSD: stack_protector.c,v 1.10 2006/03/31 05:34:44 deraadt Exp $    */
   3
   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 #include <sys/cdefs.h>
  31 __RCSID("$NetBSD: stack_protector.c,v 1.3 2009/01/30 23:21:02 ad Exp $");
  32
  33 #ifdef _LIBC
  34 #include "namespace.h"
  35 #endif
  36 #include <sys/param.h>
  37 #include <sys/sysctl.h>
  38 #include <ssp/ssp.h>
  39 #include <signal.h>
  40 #include <string.h>
  41 #include <unistd.h>
  42 #ifdef _LIBC
  43 #include <syslog.h>
  44 #include "extern.h"
  45 #else
  46 #define __sysctl sysctl
  47 void xprintf(const char *fmt, ...);
  48 #include <stdlib.h>
  49 #endif
  50
  51 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
  52 static void __fail(const char *) __attribute__((__noreturn__));
  53 void __stack_chk_fail_local(void);
  54 void __guard_setup(void);
  55
  56 void
  57 __guard_setup(void)
  58 {
  59         int mib[2];
  60         size_t len;
  61
  62         if (__stack_chk_guard[0] != 0)
  63                 return;
  64
  65         mib[0] = CTL_KERN;
  66         mib[1] = KERN_ARND;
  67
  68         len = sizeof(__stack_chk_guard);
  69         if (__sysctl(mib, 2, __stack_chk_guard, &len, NULL, 0) == -1 ||
  70             len != sizeof(__stack_chk_guard)) {
  71                 /* If sysctl was unsuccessful, use the "terminator canary". */
  72                 ((unsigned char *)(void *)__stack_chk_guard)[0] = 0;
  73                 ((unsigned char *)(void *)__stack_chk_guard)[1] = 0;
  74                 ((unsigned char *)(void *)__stack_chk_guard)[2] = '\n';
  75                 ((unsigned char *)(void *)__stack_chk_guard)[3] = 255;
  76         }
  77 }
  78
  79 /*ARGSUSED*/
  80 static void
  81 __fail(const char *msg)
  82 {
  83 #ifdef _LIBC
  84         struct syslog_data sdata = SYSLOG_DATA_INIT;
  85 #endif
  86         struct sigaction sa;
  87         sigset_t mask;
  88
  89         /* Immediately block all signal handlers from running code */
  90         (void)sigfillset(&mask);
  91         (void)sigdelset(&mask, SIGABRT);
  92         (void)sigprocmask(SIG_BLOCK, &mask, NULL);
  93
  94 #ifdef _LIBC
  95         /* This may fail on a chroot jail... */
  96         syslog_ss(LOG_CRIT, &sdata, msg);
  97 #else
  98         xprintf("%s: %s\n", getprogname(), msg);
  99 #endif
 100
 101         (void)memset(&sa, 0, sizeof(sa));
 102         (void)sigemptyset(&sa.sa_mask);
 103         sa.sa_flags = 0;
 104         sa.sa_handler = SIG_DFL;
 105         (void)sigaction(SIGABRT, &sa, NULL);
 106         (void)raise(SIGABRT);
 107         _exit(127);
 108 }
 109
 110 void
 111 __stack_chk_fail(void)
 112 {
 113         __fail("stack overflow detected; terminated");
 114 }
 115
 116 void
 117 __chk_fail(void)
 118 {
 119         __fail("buffer overflow detected; terminated");
 120 }
 121
 122 void
 123 __stack_chk_fail_local(void)
 124 {
 125         __stack_chk_fail();
 126 }