1 /* Open a descriptor to a file.
2 Copyright (C) 2007-2012 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 <http://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
orig_open(const char * filename,int flags,mode_t mode)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 <errno.h>
42 #include <stdarg.h>
43 #include <string.h>
44 #include <sys/types.h>
45 #include <sys/stat.h>
46 #include <unistd.h>
47
48 #ifndef REPLACE_OPEN_DIRECTORY
49 # define REPLACE_OPEN_DIRECTORY 0
50 #endif
51
52 int
open(const char * filename,int flags,...)53 open (const char *filename, int flags, ...)
54 {
55 mode_t mode;
56 int fd;
57
58 mode = 0;
59 if (flags & O_CREAT)
60 {
61 va_list arg;
62 va_start (arg, flags);
63
64 /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
65 creates crashing code when 'mode_t' is smaller than 'int'. */
66 mode = va_arg (arg, PROMOTED_MODE_T);
67
68 va_end (arg);
69 }
70
71 #if GNULIB_defined_O_NONBLOCK
72 /* The only known platform that lacks O_NONBLOCK is mingw, but it
73 also lacks named pipes and Unix sockets, which are the only two
74 file types that require non-blocking handling in open().
75 Therefore, it is safe to ignore O_NONBLOCK here. It is handy
76 that mingw also lacks openat(), so that is also covered here. */
77 flags &= ~O_NONBLOCK;
78 #endif
79
80 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
81 if (strcmp (filename, "/dev/null") == 0)
82 filename = "NUL";
83 #endif
84
85 #if OPEN_TRAILING_SLASH_BUG
86 /* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
87 is specified, then fail.
88 Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
89 says that
90 "A pathname that contains at least one non-slash character and that
91 ends with one or more trailing slashes shall be resolved as if a
92 single dot character ( '.' ) were appended to the pathname."
93 and
94 "The special filename dot shall refer to the directory specified by
95 its predecessor."
96 If the named file already exists as a directory, then
97 - if O_CREAT is specified, open() must fail because of the semantics
98 of O_CREAT,
99 - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
100 <http://www.opengroup.org/susv3/functions/open.html> says that it
101 fails with errno = EISDIR in this case.
102 If the named file does not exist or does not name a directory, then
103 - if O_CREAT is specified, open() must fail since open() cannot create
104 directories,
105 - if O_WRONLY or O_RDWR is specified, open() must fail because the
106 file does not contain a '.' directory. */
107 if (flags & (O_CREAT | O_WRONLY | O_RDWR))
108 {
109 size_t len = strlen (filename);
110 if (len > 0 && filename[len - 1] == '/')
111 {
112 errno = EISDIR;
113 return -1;
114 }
115 }
116 #endif
117
118 fd = orig_open (filename, flags, mode);
119
120 #if REPLACE_FCHDIR
121 /* Implementing fchdir and fdopendir requires the ability to open a
122 directory file descriptor. If open doesn't support that (as on
123 mingw), we use a dummy file that behaves the same as directories
124 on Linux (ie. always reports EOF on attempts to read()), and
125 override fstat() in fchdir.c to hide the fact that we have a
126 dummy. */
127 if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES
128 && ((flags & O_ACCMODE) == O_RDONLY
129 || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH)))
130 {
131 struct stat statbuf;
132 if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))
133 {
134 /* Maximum recursion depth of 1. */
135 fd = open ("/dev/null", flags, mode);
136 if (0 <= fd)
137 fd = _gl_register_fd (fd, filename);
138 }
139 else
140 errno = EACCES;
141 }
142 #endif
143
144 #if OPEN_TRAILING_SLASH_BUG
145 /* If the filename ends in a slash and fd does not refer to a directory,
146 then fail.
147 Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
148 says that
149 "A pathname that contains at least one non-slash character and that
150 ends with one or more trailing slashes shall be resolved as if a
151 single dot character ( '.' ) were appended to the pathname."
152 and
153 "The special filename dot shall refer to the directory specified by
154 its predecessor."
155 If the named file without the slash is not a directory, open() must fail
156 with ENOTDIR. */
157 if (fd >= 0)
158 {
159 /* We know len is positive, since open did not fail with ENOENT. */
160 size_t len = strlen (filename);
161 if (filename[len - 1] == '/')
162 {
163 struct stat statbuf;
164
165 if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
166 {
167 close (fd);
168 errno = ENOTDIR;
169 return -1;
170 }
171 }
172 }
173 #endif
174
175 #if REPLACE_FCHDIR
176 if (!REPLACE_OPEN_DIRECTORY && 0 <= fd)
177 fd = _gl_register_fd (fd, filename);
178 #endif
179
180 return fd;
181 }
182