1 /* Open a descriptor to a file. 2 Copyright (C) 2007-2020 Free Software Foundation, Inc. 3 4 This program is free software: you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation; either version 3 of the License, or 7 (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 16 17 /* Written by Bruno Haible <bruno@clisp.org>, 2007. */ 18 19 /* If the user's config.h happens to include <fcntl.h>, let it include only 20 the system's <fcntl.h> here, so that orig_open doesn't recurse to 21 rpl_open. */ 22 #define __need_system_fcntl_h 23 #include <config.h> 24 25 /* Get the original definition of open. It might be defined as a macro. */ 26 #include <fcntl.h> 27 #include <sys/types.h> 28 #undef __need_system_fcntl_h 29 30 static int 31 orig_open (const char *filename, int flags, mode_t mode) 32 { 33 return open (filename, flags, mode); 34 } 35 36 /* Specification. */ 37 /* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates 38 this include because of the preliminary #include <fcntl.h> above. */ 39 #include "fcntl.h" 40 41 #include "cloexec.h" 42 43 #include <errno.h> 44 #include <stdarg.h> 45 #include <string.h> 46 #include <sys/types.h> 47 #include <sys/stat.h> 48 #include <unistd.h> 49 50 #ifndef REPLACE_OPEN_DIRECTORY 51 # define REPLACE_OPEN_DIRECTORY 0 52 #endif 53 54 int 55 open (const char *filename, int flags, ...) 56 { 57 /* 0 = unknown, 1 = yes, -1 = no. */ 58 #if GNULIB_defined_O_CLOEXEC 59 int have_cloexec = -1; 60 #else 61 static int have_cloexec; 62 #endif 63 64 mode_t mode; 65 int fd; 66 67 mode = 0; 68 if (flags & O_CREAT) 69 { 70 va_list arg; 71 va_start (arg, flags); 72 73 /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4 74 creates crashing code when 'mode_t' is smaller than 'int'. */ 75 mode = va_arg (arg, PROMOTED_MODE_T); 76 77 va_end (arg); 78 } 79 80 #if GNULIB_defined_O_NONBLOCK 81 /* The only known platform that lacks O_NONBLOCK is mingw, but it 82 also lacks named pipes and Unix sockets, which are the only two 83 file types that require non-blocking handling in open(). 84 Therefore, it is safe to ignore O_NONBLOCK here. It is handy 85 that mingw also lacks openat(), so that is also covered here. */ 86 flags &= ~O_NONBLOCK; 87 #endif 88 89 #if defined _WIN32 && ! defined __CYGWIN__ 90 if (strcmp (filename, "/dev/null") == 0) 91 filename = "NUL"; 92 #endif 93 94 #if OPEN_TRAILING_SLASH_BUG 95 /* Fail if one of O_CREAT, O_WRONLY, O_RDWR is specified and the filename 96 ends in a slash, as POSIX says such a filename must name a directory 97 <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: 98 "A pathname that contains at least one non-<slash> character and that 99 ends with one or more trailing <slash> characters shall not be resolved 100 successfully unless the last pathname component before the trailing 101 <slash> characters names an existing directory" 102 If the named file already exists as a directory, then 103 - if O_CREAT is specified, open() must fail because of the semantics 104 of O_CREAT, 105 - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX 106 <https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html> 107 says that it fails with errno = EISDIR in this case. 108 If the named file does not exist or does not name a directory, then 109 - if O_CREAT is specified, open() must fail since open() cannot create 110 directories, 111 - if O_WRONLY or O_RDWR is specified, open() must fail because the 112 file does not contain a '.' directory. */ 113 if ((flags & O_CREAT) 114 || (flags & O_ACCMODE) == O_RDWR 115 || (flags & O_ACCMODE) == O_WRONLY) 116 { 117 size_t len = strlen (filename); 118 if (len > 0 && filename[len - 1] == '/') 119 { 120 errno = EISDIR; 121 return -1; 122 } 123 } 124 #endif 125 126 fd = orig_open (filename, 127 flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode); 128 129 if (flags & O_CLOEXEC) 130 { 131 if (! have_cloexec) 132 { 133 if (0 <= fd) 134 have_cloexec = 1; 135 else if (errno == EINVAL) 136 { 137 fd = orig_open (filename, flags & ~O_CLOEXEC, mode); 138 have_cloexec = -1; 139 } 140 } 141 if (have_cloexec < 0 && 0 <= fd) 142 set_cloexec_flag (fd, true); 143 } 144 145 146 #if REPLACE_FCHDIR 147 /* Implementing fchdir and fdopendir requires the ability to open a 148 directory file descriptor. If open doesn't support that (as on 149 mingw), we use a dummy file that behaves the same as directories 150 on Linux (ie. always reports EOF on attempts to read()), and 151 override fstat() in fchdir.c to hide the fact that we have a 152 dummy. */ 153 if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES 154 && ((flags & O_ACCMODE) == O_RDONLY 155 || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH))) 156 { 157 struct stat statbuf; 158 if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode)) 159 { 160 /* Maximum recursion depth of 1. */ 161 fd = open ("/dev/null", flags, mode); 162 if (0 <= fd) 163 fd = _gl_register_fd (fd, filename); 164 } 165 else 166 errno = EACCES; 167 } 168 #endif 169 170 #if OPEN_TRAILING_SLASH_BUG 171 /* If the filename ends in a slash and fd does not refer to a directory, 172 then fail. 173 Rationale: POSIX says such a filename must name a directory 174 <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: 175 "A pathname that contains at least one non-<slash> character and that 176 ends with one or more trailing <slash> characters shall not be resolved 177 successfully unless the last pathname component before the trailing 178 <slash> characters names an existing directory" 179 If the named file without the slash is not a directory, open() must fail 180 with ENOTDIR. */ 181 if (fd >= 0) 182 { 183 /* We know len is positive, since open did not fail with ENOENT. */ 184 size_t len = strlen (filename); 185 if (filename[len - 1] == '/') 186 { 187 struct stat statbuf; 188 189 if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode)) 190 { 191 close (fd); 192 errno = ENOTDIR; 193 return -1; 194 } 195 } 196 } 197 #endif 198 199 #if REPLACE_FCHDIR 200 if (!REPLACE_OPEN_DIRECTORY && 0 <= fd) 201 fd = _gl_register_fd (fd, filename); 202 #endif 203 204 return fd; 205 } 206