| 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 | O_WRONLY | O_RDWR)) |
| 114 | { |
| 115 | size_t len = strlen (filename); |
| 116 | if (len > 0 && filename[len - 1] == '/') |
| 117 | { |
| 118 | errno = EISDIR; |
| 119 | return -1; |
| 120 | } |
| 121 | } |
| 122 | #endif |
| 123 | |
| 124 | fd = orig_open (filename, |
| 125 | flags & ~(have_cloexec <= 0 ? O_CLOEXEC : 0), mode); |
| 126 | |
| 127 | if (flags & O_CLOEXEC) |
| 128 | { |
| 129 | if (! have_cloexec) |
| 130 | { |
| 131 | if (0 <= fd) |
| 132 | have_cloexec = 1; |
| 133 | else if (errno == EINVAL) |
| 134 | { |
| 135 | fd = orig_open (filename, flags & ~O_CLOEXEC, mode); |
| 136 | have_cloexec = -1; |
| 137 | } |
| 138 | } |
| 139 | if (have_cloexec < 0 && 0 <= fd) |
| 140 | set_cloexec_flag (fd, true); |
| 141 | } |
| 142 | |
| 143 | |
| 144 | #if REPLACE_FCHDIR |
| 145 | /* Implementing fchdir and fdopendir requires the ability to open a |
| 146 | directory file descriptor. If open doesn't support that (as on |
| 147 | mingw), we use a dummy file that behaves the same as directories |
| 148 | on Linux (ie. always reports EOF on attempts to read()), and |
| 149 | override fstat() in fchdir.c to hide the fact that we have a |
| 150 | dummy. */ |
| 151 | if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES |
| 152 | && ((flags & O_ACCMODE) == O_RDONLY |
| 153 | || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH))) |
| 154 | { |
| 155 | struct stat statbuf; |
| 156 | if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode)) |
| 157 | { |
| 158 | /* Maximum recursion depth of 1. */ |
| 159 | fd = open ("/dev/null", flags, mode); |
| 160 | if (0 <= fd) |
| 161 | fd = _gl_register_fd (fd, filename); |
| 162 | } |
| 163 | else |
| 164 | errno = EACCES; |
| 165 | } |
| 166 | #endif |
| 167 | |
| 168 | #if OPEN_TRAILING_SLASH_BUG |
| 169 | /* If the filename ends in a slash and fd does not refer to a directory, |
| 170 | then fail. |
| 171 | Rationale: POSIX says such a filename must name a directory |
| 172 | <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>: |
| 173 | "A pathname that contains at least one non-<slash> character and that |
| 174 | ends with one or more trailing <slash> characters shall not be resolved |
| 175 | successfully unless the last pathname component before the trailing |
| 176 | <slash> characters names an existing directory" |
| 177 | If the named file without the slash is not a directory, open() must fail |
| 178 | with ENOTDIR. */ |
| 179 | if (fd >= 0) |
| 180 | { |
| 181 | /* We know len is positive, since open did not fail with ENOENT. */ |
| 182 | size_t len = strlen (filename); |
| 183 | if (filename[len - 1] == '/') |
| 184 | { |
| 185 | struct stat statbuf; |
| 186 | |
| 187 | if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode)) |
| 188 | { |
| 189 | close (fd); |
| 190 | errno = ENOTDIR; |
| 191 | return -1; |
| 192 | } |
| 193 | } |
| 194 | } |
| 195 | #endif |
| 196 | |
| 197 | #if REPLACE_FCHDIR |
| 198 | if (!REPLACE_OPEN_DIRECTORY && 0 <= fd) |
| 199 | fd = _gl_register_fd (fd, filename); |
| 200 | #endif |
| 201 | |
| 202 | return fd; |
| 203 | } |