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      1 /*	$NetBSD: stack_protector.c,v 1.10 2025/05/02 23:04:56 riastradh 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 1.10 2025/05/02 23:04:56 riastradh 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 void xprintf(const char *fmt, ...);
     47 #include <stdlib.h>
     48 #endif
     49 
     50 #include "../include/__sysctl.h"
     51 
     52 long __stack_chk_guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
     53 static void __fail(const char *) __attribute__((__noreturn__));
     54 __dead void __stack_chk_fail_local(void);
     55 void __guard_setup(void);
     56 
     57 void __section(".text.startup")
     58 __guard_setup(void)
     59 {
     60 	static const int mib[2] = { CTL_KERN, KERN_ARND };
     61 	size_t len;
     62 
     63 	if (__stack_chk_guard[0] != 0)
     64 		return;
     65 
     66 	len = sizeof(__stack_chk_guard);
     67 	if (__sysctl(mib, (u_int)__arraycount(mib), __stack_chk_guard, &len,
     68 	    NULL, 0) == -1 || len != sizeof(__stack_chk_guard)) {
     69 		/* If sysctl was unsuccessful, use the "terminator canary". */
     70 		((unsigned char *)(void *)__stack_chk_guard)[0] = 0;
     71 		((unsigned char *)(void *)__stack_chk_guard)[1] = 0;
     72 		((unsigned char *)(void *)__stack_chk_guard)[2] = '\n';
     73 		((unsigned char *)(void *)__stack_chk_guard)[3] = 255;
     74 	}
     75 }
     76 
     77 /*ARGSUSED*/
     78 static void
     79 __fail(const char *msg)
     80 {
     81 #ifdef _LIBC
     82 	struct syslog_data sdata = SYSLOG_DATA_INIT;
     83 #endif
     84 	struct sigaction sa;
     85 	sigset_t mask;
     86 
     87 	/* Immediately block all signal handlers from running code */
     88 	(void)sigfillset(&mask);
     89 	(void)sigdelset(&mask, SIGABRT);
     90 	(void)sigprocmask(SIG_BLOCK, &mask, NULL);
     91 
     92 #ifdef _LIBC
     93 	/* This may fail on a chroot jail... */
     94 	syslog_ss(LOG_CRIT, &sdata, "%s", msg);
     95 #else
     96 	xprintf("%s: %s\n", getprogname(), msg);
     97 #endif
     98 
     99 	(void)memset(&sa, 0, sizeof(sa));
    100 	(void)sigemptyset(&sa.sa_mask);
    101 	sa.sa_flags = 0;
    102 	sa.sa_handler = SIG_DFL;
    103 	(void)sigaction(SIGABRT, &sa, NULL);
    104 	(void)raise(SIGABRT);
    105 	_exit(127);
    106 }
    107 
    108 void
    109 __stack_chk_fail(void)
    110 {
    111 	__fail("stack overflow detected; terminated");
    112 }
    113 
    114 void
    115 __chk_fail(void)
    116 {
    117 	__fail("buffer overflow detected; terminated");
    118 }
    119 
    120 void
    121 __stack_chk_fail_local(void)
    122 {
    123 	__stack_chk_fail();
    124 }
    125