2018-09-13 Richard Biener <rguenther@suse.de>
[official-gcc.git] / libssp / ssp.c
blob741377ddd4050a1583952c32bdcffe372a3b4aa8
1 /* Stack protector support.
2 Copyright (C) 2005-2018 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
11 In addition to the permissions in the GNU General Public License, the
12 Free Software Foundation gives you unlimited permission to link the
13 compiled version of this file into combinations with other programs,
14 and to distribute those combinations without any restriction coming
15 from the use of this file. (The General Public License restrictions
16 do apply in other respects; for example, they cover modification of
17 the file, and distribution when not linked into a combine
18 executable.)
20 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
21 WARRANTY; without even the implied warranty of MERCHANTABILITY or
22 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
23 for more details.
25 Under Section 7 of GPL version 3, you are granted additional
26 permissions described in the GCC Runtime Library Exception, version
27 3.1, as published by the Free Software Foundation.
29 You should have received a copy of the GNU General Public License and
30 a copy of the GCC Runtime Library Exception along with this program;
31 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
32 <http://www.gnu.org/licenses/>. */
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
69 void *__stack_chk_guard = 0;
71 static void __attribute__ ((constructor))
72 __guard_setup (void)
74 unsigned char *p;
76 if (__stack_chk_guard != 0)
77 return;
79 #if defined (_WIN32) && !defined (__CYGWIN__)
80 HCRYPTPROV hprovider = 0;
81 if (CryptAcquireContext(&hprovider, NULL, NULL, PROV_RSA_FULL,
82 CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
84 if (CryptGenRandom(hprovider, sizeof (__stack_chk_guard),
85 (BYTE *)&__stack_chk_guard) && __stack_chk_guard != 0)
87 CryptReleaseContext(hprovider, 0);
88 return;
90 CryptReleaseContext(hprovider, 0);
92 #else
93 int fd = open ("/dev/urandom", O_RDONLY);
94 if (fd != -1)
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;
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;
112 static void
113 fail (const char *msg1, size_t msg1len, const char *msg3)
115 #ifdef __GNU_LIBRARY__
116 extern char * __progname;
117 #else
118 static const char __progname[] = "";
119 #endif
120 int fd;
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)
127 static const char msg2[] = " terminated\n";
128 size_t progname_len, len;
129 char *buf, *p;
131 progname_len = strlen (__progname);
132 len = msg1len + progname_len + sizeof(msg2)-1 + 1;
133 p = buf = alloca (len);
135 memcpy (p, msg1, msg1len);
136 p += msg1len;
137 memcpy (p, __progname, progname_len);
138 p += progname_len;
139 memcpy (p, msg2, sizeof(msg2));
141 while (len > 0)
143 ssize_t wrote = write (fd, buf, len);
144 if (wrote < 0)
145 break;
146 buf += wrote;
147 len -= wrote;
149 close (fd);
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 */
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. */
164 volatile int state;
165 for (state = 0; ; state++)
166 switch (state)
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;
181 void
182 __stack_chk_fail (void)
184 const char *msg = "*** stack smashing detected ***: ";
185 fail (msg, strlen (msg), "stack smashing detected: terminated");
188 void
189 __chk_fail (void)
191 const char *msg = "*** buffer overflow detected ***: ";
192 fail (msg, strlen (msg), "buffer overflow detected: terminated");
195 #ifdef HAVE_HIDDEN_VISIBILITY
196 void
197 __attribute__((visibility ("hidden")))
198 __stack_chk_fail_local (void)
200 __stack_chk_fail ();
202 #endif