1/* Stack protector support.
2 Copyright (C) 2005-2017 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11In addition to the permissions in the GNU General Public License, the
12Free Software Foundation gives you unlimited permission to link the
13compiled version of this file into combinations with other programs,
14and to distribute those combinations without any restriction coming
15from the use of this file. (The General Public License restrictions
16do apply in other respects; for example, they cover modification of
17the file, and distribution when not linked into a combine
18executable.)
19
20GCC is distributed in the hope that it will be useful, but WITHOUT ANY
21WARRANTY; without even the implied warranty of MERCHANTABILITY or
22FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
23for more details.
24
25Under Section 7 of GPL version 3, you are granted additional
26permissions described in the GCC Runtime Library Exception, version
273.1, as published by the Free Software Foundation.
28
29You should have received a copy of the GNU General Public License and
30a copy of the GCC Runtime Library Exception along with this program;
31see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
32<http://www.gnu.org/licenses/>. */
33
34
35#include "config.h"
36#ifdef HAVE_ALLOCA_H
37# include <alloca.h>
38#endif
39#ifdef HAVE_MALLOC_H
40# include <malloc.h>
41#endif
42#ifdef HAVE_STRING_H
43# include <string.h>
44#endif
45#ifdef HAVE_UNISTD_H
46# include <unistd.h>
47#endif
48#ifdef HAVE_FCNTL_H
49# include <fcntl.h>
50#endif
51#ifdef HAVE_PATHS_H
52# include <paths.h>
53#endif
54#ifndef _PATH_TTY
55/* Native win32 apps don't know about /dev/tty but can print directly
56 to the console using "CONOUT$" */
57#if defined (_WIN32) && !defined (__CYGWIN__)
58#include <windows.h>
59#include <wincrypt.h>
60# define _PATH_TTY "CONOUT$"
61#else
62# define _PATH_TTY "/dev/tty"
63#endif
64#endif
65#ifdef HAVE_SYSLOG_H
66# include <syslog.h>
67#endif
68
69void *__stack_chk_guard = 0;
70
71static void __attribute__ ((constructor))
72__guard_setup (void)
73{
74 unsigned char *p;
75
76 if (__stack_chk_guard != 0)
77 return;
78
79#if defined (_WIN32) && !defined (__CYGWIN__)
80 HCRYPTPROV hprovider = 0;
81 if (CryptAcquireContext(&hprovider, NULL, NULL, PROV_RSA_FULL,
82 CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
83 {
84 if (CryptGenRandom(hprovider, sizeof (__stack_chk_guard),
85 (BYTE *)&__stack_chk_guard) && __stack_chk_guard != 0)
86 {
87 CryptReleaseContext(hprovider, 0);
88 return;
89 }
90 CryptReleaseContext(hprovider, 0);
91 }
92#else
93 int fd = open ("/dev/urandom", O_RDONLY);
94 if (fd != -1)
95 {
96 ssize_t size = read (fd, &__stack_chk_guard,
97 sizeof (__stack_chk_guard));
98 close (fd);
99 if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0)
100 return;
101 }
102
103#endif
104 /* If a random generator can't be used, the protector switches the guard
105 to the "terminator canary". */
106 p = (unsigned char *) &__stack_chk_guard;
107 p[sizeof(__stack_chk_guard)-1] = 255;
108 p[sizeof(__stack_chk_guard)-2] = '\n';
109 p[0] = 0;
110}
111
112static void
113fail (const char *msg1, size_t msg1len, const char *msg3)
114{
115#ifdef __GNU_LIBRARY__
116 extern char * __progname;
117#else
118 static const char __progname[] = "";
119#endif
120 int fd;
121
122 /* Print error message directly to the tty. This avoids Bad Things
123 happening if stderr is redirected. */
124 fd = open (_PATH_TTY, O_WRONLY);
125 if (fd != -1)
126 {
127 static const char msg2[] = " terminated\n";
128 size_t progname_len, len;
129 char *buf, *p;
130
131 progname_len = strlen (__progname);
132 len = msg1len + progname_len + sizeof(msg2)-1 + 1;
133 p = buf = alloca (len);
134
135 memcpy (p, msg1, msg1len);
136 p += msg1len;
137 memcpy (p, __progname, progname_len);
138 p += progname_len;
139 memcpy (p, msg2, sizeof(msg2));
140
141 while (len > 0)
142 {
143 ssize_t wrote = write (fd, buf, len);
144 if (wrote < 0)
145 break;
146 buf += wrote;
147 len -= wrote;
148 }
149 close (fd);
150 }
151
152#ifdef HAVE_SYSLOG_H
153 /* Only send the error to syslog if there was no tty available. */
154 else
155 syslog (LOG_CRIT, "%s", msg3);
156#endif /* HAVE_SYSLOG_H */
157
158 /* Try very hard to exit. Note that signals may be blocked preventing
159 the first two options from working. The use of volatile is here to
160 prevent optimizers from "knowing" that __builtin_trap is called first,
161 and that it doesn't return, and so "obviously" the rest of the code
162 is dead. */
163 {
164 volatile int state;
165 for (state = 0; ; state++)
166 switch (state)
167 {
168 case 0:
169 __builtin_trap ();
170 break;
171 case 1:
172 *(volatile int *)-1L = 0;
173 break;
174 case 2:
175 _exit (127);
176 break;
177 }
178 }
179}
180
181void
182__stack_chk_fail (void)
183{
184 const char *msg = "*** stack smashing detected ***: ";
185 fail (msg, strlen (msg), "stack smashing detected: terminated");
186}
187
188void
189__chk_fail (void)
190{
191 const char *msg = "*** buffer overflow detected ***: ";
192 fail (msg, strlen (msg), "buffer overflow detected: terminated");
193}
194
195#ifdef HAVE_HIDDEN_VISIBILITY
196void
197__attribute__((visibility ("hidden")))
198__stack_chk_fail_local (void)
199{
200 __stack_chk_fail ();
201}
202#endif
203