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
30static int
31orig_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
52int
53open (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