1 /* Stack protector support. 2 Copyright (C) 2005-2013 Free Software Foundation, Inc. 3 4 This file is part of GCC. 5 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. 10 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.) 19 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. 24 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. 28 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/>. */ 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 69 void *__stack_chk_guard = 0; 70 71 static void __attribute__ ((constructor)) 72 __guard_setup (void) 73 { 74 unsigned char *p; 75 int fd; 76 77 if (__stack_chk_guard != 0) 78 return; 79 80 #if defined (_WIN32) && !defined (__CYGWIN__) 81 HCRYPTPROV hprovider = 0; 82 if (CryptAcquireContext(&hprovider, NULL, NULL, PROV_RSA_FULL, 83 CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) 84 { 85 if (CryptGenRandom(hprovider, sizeof (__stack_chk_guard), 86 (BYTE *)&__stack_chk_guard) && __stack_chk_guard != 0) 87 { 88 CryptReleaseContext(hprovider, 0); 89 return; 90 } 91 CryptReleaseContext(hprovider, 0); 92 } 93 #else 94 fd = open ("/dev/urandom", O_RDONLY); 95 if (fd != -1) 96 { 97 ssize_t size = read (fd, &__stack_chk_guard, 98 sizeof (__stack_chk_guard)); 99 close (fd); 100 if (size == sizeof(__stack_chk_guard) && __stack_chk_guard != 0) 101 return; 102 } 103 104 #endif 105 /* If a random generator can't be used, the protector switches the guard 106 to the "terminator canary". */ 107 p = (unsigned char *) &__stack_chk_guard; 108 p[sizeof(__stack_chk_guard)-1] = 255; 109 p[sizeof(__stack_chk_guard)-2] = '\n'; 110 p[0] = 0; 111 } 112 113 static void 114 fail (const char *msg1, size_t msg1len, const char *msg3) 115 { 116 #ifdef __GNU_LIBRARY__ 117 extern char * __progname; 118 #else 119 static const char __progname[] = ""; 120 #endif 121 int fd; 122 123 /* Print error message directly to the tty. This avoids Bad Things 124 happening if stderr is redirected. */ 125 fd = open (_PATH_TTY, O_WRONLY); 126 if (fd != -1) 127 { 128 static const char msg2[] = " terminated\n"; 129 size_t progname_len, len; 130 char *buf, *p; 131 132 progname_len = strlen (__progname); 133 len = msg1len + progname_len + sizeof(msg2)-1 + 1; 134 p = buf = alloca (len); 135 136 memcpy (p, msg1, msg1len); 137 p += msg1len; 138 memcpy (p, __progname, progname_len); 139 p += progname_len; 140 memcpy (p, msg2, sizeof(msg2)); 141 142 while (len > 0) 143 { 144 ssize_t wrote = write (fd, buf, len); 145 if (wrote < 0) 146 break; 147 buf += wrote; 148 len -= wrote; 149 } 150 close (fd); 151 } 152 153 #ifdef HAVE_SYSLOG_H 154 /* Only send the error to syslog if there was no tty available. */ 155 else 156 syslog (LOG_CRIT, "%s", msg3); 157 #endif /* HAVE_SYSLOG_H */ 158 159 /* Try very hard to exit. Note that signals may be blocked preventing 160 the first two options from working. The use of volatile is here to 161 prevent optimizers from "knowing" that __builtin_trap is called first, 162 and that it doesn't return, and so "obviously" the rest of the code 163 is dead. */ 164 { 165 volatile int state; 166 for (state = 0; ; state++) 167 switch (state) 168 { 169 case 0: 170 __builtin_trap (); 171 break; 172 case 1: 173 *(volatile int *)-1L = 0; 174 break; 175 case 2: 176 _exit (127); 177 break; 178 } 179 } 180 } 181 182 void 183 __stack_chk_fail (void) 184 { 185 const char *msg = "*** stack smashing detected ***: "; 186 fail (msg, strlen (msg), "stack smashing detected: terminated"); 187 } 188 189 void 190 __chk_fail (void) 191 { 192 const char *msg = "*** buffer overflow detected ***: "; 193 fail (msg, strlen (msg), "buffer overflow detected: terminated"); 194 } 195 196 #ifdef HAVE_HIDDEN_VISIBILITY 197 void 198 __attribute__((visibility ("hidden"))) 199 __stack_chk_fail_local (void) 200 { 201 __stack_chk_fail (); 202 } 203 #endif 204