gsasl  1.10.0
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open.c
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1 /* Open a descriptor to a file.
2  Copyright (C) 2007-2021 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 #if defined _WIN32 && !defined __CYGWIN__
34  return _open (filename, flags, mode);
35 #else
36  return open (filename, flags, mode);
37 #endif
38 }
39 
40 /* Specification. */
41 /* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
42  this include because of the preliminary #include <fcntl.h> above. */
43 #include "fcntl.h"
44 
45 #include "cloexec.h"
46 
47 #include <errno.h>
48 #include <stdarg.h>
49 #include <string.h>
50 #include <sys/types.h>
51 #include <sys/stat.h>
52 #include <unistd.h>
53 
54 #ifndef REPLACE_OPEN_DIRECTORY
55 # define REPLACE_OPEN_DIRECTORY 0
56 #endif
57 
58 int
59 open (const char *filename, int flags, ...)
60 {
61  /* 0 = unknown, 1 = yes, -1 = no. */
62 #if GNULIB_defined_O_CLOEXEC
63  int have_cloexec = -1;
64 #else
65  static int have_cloexec;
66 #endif
67 
68  mode_t mode;
69  int fd;
70 
71  mode = 0;
72  if (flags & O_CREAT)
73  {
74  va_list arg;
75  va_start (arg, flags);
76 
77  /* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
78  creates crashing code when 'mode_t' is smaller than 'int'. */
79  mode = va_arg (arg, PROMOTED_MODE_T);
80 
81  va_end (arg);
82  }
83 
84 #if GNULIB_defined_O_NONBLOCK
85  /* The only known platform that lacks O_NONBLOCK is mingw, but it
86  also lacks named pipes and Unix sockets, which are the only two
87  file types that require non-blocking handling in open().
88  Therefore, it is safe to ignore O_NONBLOCK here. It is handy
89  that mingw also lacks openat(), so that is also covered here. */
90  flags &= ~O_NONBLOCK;
91 #endif
92 
93 #if defined _WIN32 && ! defined __CYGWIN__
94  if (strcmp (filename, "/dev/null") == 0)
95  filename = "NUL";
96 #endif
97 
98 #if OPEN_TRAILING_SLASH_BUG
99  /* Fail if one of O_CREAT, O_WRONLY, O_RDWR is specified and the filename
100  ends in a slash, as POSIX says such a filename must name a directory
101  <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
102  "A pathname that contains at least one non-<slash> character and that
103  ends with one or more trailing <slash> characters shall not be resolved
104  successfully unless the last pathname component before the trailing
105  <slash> characters names an existing directory"
106  If the named file already exists as a directory, then
107  - if O_CREAT is specified, open() must fail because of the semantics
108  of O_CREAT,
109  - if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
110  <https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html>
111  says that it fails with errno = EISDIR in this case.
112  If the named file does not exist or does not name a directory, then
113  - if O_CREAT is specified, open() must fail since open() cannot create
114  directories,
115  - if O_WRONLY or O_RDWR is specified, open() must fail because the
116  file does not contain a '.' directory. */
117  if ((flags & O_CREAT)
118  || (flags & O_ACCMODE) == O_RDWR
119  || (flags & O_ACCMODE) == O_WRONLY)
120  {
121  size_t len = strlen (filename);
122  if (len > 0 && filename[len - 1] == '/')
123  {
124  errno = EISDIR;
125  return -1;
126  }
127  }
128 #endif
129 
130  fd = orig_open (filename,
131  flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode);
132 
133  if (flags & O_CLOEXEC)
134  {
135  if (! have_cloexec)
136  {
137  if (0 <= fd)
138  have_cloexec = 1;
139  else if (errno == EINVAL)
140  {
141  fd = orig_open (filename, flags & ~O_CLOEXEC, mode);
142  have_cloexec = -1;
143  }
144  }
145  if (have_cloexec < 0 && 0 <= fd)
146  set_cloexec_flag (fd, true);
147  }
148 
149 
150 #if REPLACE_FCHDIR
151  /* Implementing fchdir and fdopendir requires the ability to open a
152  directory file descriptor. If open doesn't support that (as on
153  mingw), we use a dummy file that behaves the same as directories
154  on Linux (ie. always reports EOF on attempts to read()), and
155  override fstat() in fchdir.c to hide the fact that we have a
156  dummy. */
157  if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES
158  && ((flags & O_ACCMODE) == O_RDONLY
159  || (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH)))
160  {
161  struct stat statbuf;
162  if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))
163  {
164  /* Maximum recursion depth of 1. */
165  fd = open ("/dev/null", flags, mode);
166  if (0 <= fd)
167  fd = _gl_register_fd (fd, filename);
168  }
169  else
170  errno = EACCES;
171  }
172 #endif
173 
174 #if OPEN_TRAILING_SLASH_BUG
175  /* If the filename ends in a slash and fd does not refer to a directory,
176  then fail.
177  Rationale: POSIX says such a filename must name a directory
178  <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
179  "A pathname that contains at least one non-<slash> character and that
180  ends with one or more trailing <slash> characters shall not be resolved
181  successfully unless the last pathname component before the trailing
182  <slash> characters names an existing directory"
183  If the named file without the slash is not a directory, open() must fail
184  with ENOTDIR. */
185  if (fd >= 0)
186  {
187  /* We know len is positive, since open did not fail with ENOENT. */
188  size_t len = strlen (filename);
189  if (filename[len - 1] == '/')
190  {
191  struct stat statbuf;
192 
193  if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
194  {
195  close (fd);
196  errno = ENOTDIR;
197  return -1;
198  }
199  }
200  }
201 #endif
202 
203 #if REPLACE_FCHDIR
204  if (!REPLACE_OPEN_DIRECTORY && 0 <= fd)
205  fd = _gl_register_fd (fd, filename);
206 #endif
207 
208  return fd;
209 }
int set_cloexec_flag(int desc, signed char value)
Definition: cloexec.c:39
#define O_NONBLOCK
Definition: fcntl.in.h:326
#define O_SEARCH
Definition: fcntl.in.h:367
#define O_CLOEXEC
Definition: fcntl.in.h:291
static int orig_open(const char *filename, int flags, mode_t mode)
Definition: open.c:31
#define REPLACE_OPEN_DIRECTORY
Definition: open.c:55
int open(const char *filename, int flags,...)
Definition: open.c:59
#define S_ISDIR(m)
Definition: sys_stat.in.h:195