1 /* Stack protector support. 2 Copyright (C) 2005-2020 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 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 } 111 112 static void 113 fail (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 } 180 181 void 182 __stack_chk_fail (void) 183 { 184 const char *msg = "*** stack smashing detected ***: "; 185 fail (msg, strlen (msg), "stack smashing detected: terminated"); 186 } 187 188 void 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 196 void 197 __attribute__((visibility ("hidden"))) 198 __stack_chk_fail_local (void) 199 { 200 __stack_chk_fail (); 201 } 202 #endif 203