209 lines
6.7 KiB
C
209 lines
6.7 KiB
C
/* Open a descriptor to a file.
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Copyright (C) 2007-2021 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible <bruno@clisp.org>, 2007. */
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/* If the user's config.h happens to include <fcntl.h>, let it include only
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the system's <fcntl.h> here, so that orig_open doesn't recurse to
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rpl_open. */
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#define __need_system_fcntl_h
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#include <config.h>
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/* Get the original definition of open. It might be defined as a macro. */
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#include <fcntl.h>
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#include <sys/types.h>
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#undef __need_system_fcntl_h
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static int
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orig_open (const char *filename, int flags, mode_t mode)
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{
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#if defined _WIN32 && !defined __CYGWIN__
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return _open (filename, flags, mode);
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#else
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return open (filename, flags, mode);
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#endif
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}
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/* Specification. */
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/* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
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this include because of the preliminary #include <fcntl.h> above. */
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#include "fcntl.h"
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#include "cloexec.h"
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#include <errno.h>
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#include <stdarg.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#ifndef REPLACE_OPEN_DIRECTORY
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# define REPLACE_OPEN_DIRECTORY 0
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#endif
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int
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open (const char *filename, int flags, ...)
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{
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/* 0 = unknown, 1 = yes, -1 = no. */
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#if GNULIB_defined_O_CLOEXEC
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int have_cloexec = -1;
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#else
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static int have_cloexec;
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#endif
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mode_t mode;
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int fd;
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mode = 0;
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if (flags & O_CREAT)
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{
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va_list arg;
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va_start (arg, flags);
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/* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
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creates crashing code when 'mode_t' is smaller than 'int'. */
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mode = va_arg (arg, PROMOTED_MODE_T);
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va_end (arg);
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}
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#if GNULIB_defined_O_NONBLOCK
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/* The only known platform that lacks O_NONBLOCK is mingw, but it
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also lacks named pipes and Unix sockets, which are the only two
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file types that require non-blocking handling in open().
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Therefore, it is safe to ignore O_NONBLOCK here. It is handy
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that mingw also lacks openat(), so that is also covered here. */
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flags &= ~O_NONBLOCK;
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#endif
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#if defined _WIN32 && ! defined __CYGWIN__
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if (strcmp (filename, "/dev/null") == 0)
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filename = "NUL";
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#endif
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#if OPEN_TRAILING_SLASH_BUG
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/* Fail if one of O_CREAT, O_WRONLY, O_RDWR is specified and the filename
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ends in a slash, as POSIX says such a filename must name a directory
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<https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
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"A pathname that contains at least one non-<slash> character and that
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ends with one or more trailing <slash> characters shall not be resolved
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successfully unless the last pathname component before the trailing
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<slash> characters names an existing directory"
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If the named file already exists as a directory, then
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- if O_CREAT is specified, open() must fail because of the semantics
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of O_CREAT,
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- if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
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<https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html>
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says that it fails with errno = EISDIR in this case.
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If the named file does not exist or does not name a directory, then
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- if O_CREAT is specified, open() must fail since open() cannot create
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directories,
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- if O_WRONLY or O_RDWR is specified, open() must fail because the
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file does not contain a '.' directory. */
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if ((flags & O_CREAT)
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|| (flags & O_ACCMODE) == O_RDWR
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|| (flags & O_ACCMODE) == O_WRONLY)
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{
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size_t len = strlen (filename);
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if (len > 0 && filename[len - 1] == '/')
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{
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errno = EISDIR;
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return -1;
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}
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}
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#endif
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fd = orig_open (filename,
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flags & ~(have_cloexec < 0 ? O_CLOEXEC : 0), mode);
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if (flags & O_CLOEXEC)
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{
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if (! have_cloexec)
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{
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if (0 <= fd)
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have_cloexec = 1;
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else if (errno == EINVAL)
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{
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fd = orig_open (filename, flags & ~O_CLOEXEC, mode);
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have_cloexec = -1;
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}
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}
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if (have_cloexec < 0 && 0 <= fd)
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set_cloexec_flag (fd, true);
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}
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#if REPLACE_FCHDIR
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/* Implementing fchdir and fdopendir requires the ability to open a
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directory file descriptor. If open doesn't support that (as on
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mingw), we use a dummy file that behaves the same as directories
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on Linux (ie. always reports EOF on attempts to read()), and
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override fstat() in fchdir.c to hide the fact that we have a
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dummy. */
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if (REPLACE_OPEN_DIRECTORY && fd < 0 && errno == EACCES
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&& ((flags & O_ACCMODE) == O_RDONLY
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|| (O_SEARCH != O_RDONLY && (flags & O_ACCMODE) == O_SEARCH)))
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{
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struct stat statbuf;
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if (stat (filename, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))
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{
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/* Maximum recursion depth of 1. */
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fd = open ("/dev/null", flags, mode);
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if (0 <= fd)
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fd = _gl_register_fd (fd, filename);
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}
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else
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errno = EACCES;
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}
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#endif
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#if OPEN_TRAILING_SLASH_BUG
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/* If the filename ends in a slash and fd does not refer to a directory,
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then fail.
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Rationale: POSIX says such a filename must name a directory
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<https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:
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"A pathname that contains at least one non-<slash> character and that
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ends with one or more trailing <slash> characters shall not be resolved
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successfully unless the last pathname component before the trailing
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<slash> characters names an existing directory"
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If the named file without the slash is not a directory, open() must fail
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with ENOTDIR. */
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if (fd >= 0)
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{
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/* We know len is positive, since open did not fail with ENOENT. */
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size_t len = strlen (filename);
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if (filename[len - 1] == '/')
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{
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struct stat statbuf;
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if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
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{
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close (fd);
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errno = ENOTDIR;
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return -1;
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}
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}
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}
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#endif
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#if REPLACE_FCHDIR
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if (!REPLACE_OPEN_DIRECTORY && 0 <= fd)
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fd = _gl_register_fd (fd, filename);
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#endif
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return fd;
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}
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