/* provide a replacement openat function
Copyright (C) 2004-2017 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
/* If the user's config.h happens to include <fcntl.h>, let it include only
the system's <fcntl.h> here, so that orig_openat doesn't recurse to
rpl_openat. */
#define __need_system_fcntl_h
#include <config.h>
/* Get the original definition of open. It might be defined as a macro. */
#include <fcntl.h>
#include <sys/types.h>
#undef __need_system_fcntl_h
#if HAVE_OPENAT
static int
orig_openat (int fd, char const *filename, int flags, mode_t mode)
{
return openat (fd, filename, flags, mode);
}
#endif
/* Write "fcntl.h" here, not <fcntl.h>, otherwise OSF/1 5.1 DTK cc eliminates
this include because of the preliminary #include <fcntl.h> above. */
#include "fcntl.h"
#include "openat.h"
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include <sys/stat.h>
#include <errno.h>
#if HAVE_OPENAT
/* Like openat, but work around Solaris 9 bugs with trailing slash. */
int
rpl_openat (int dfd, char const *filename, int flags, ...)
{
mode_t mode;
int fd;
mode = 0;
if (flags & O_CREAT)
{
va_list arg;
va_start (arg, flags);
/* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
creates crashing code when 'mode_t' is smaller than 'int'. */
mode = va_arg (arg, PROMOTED_MODE_T);
va_end (arg);
}
# if OPEN_TRAILING_SLASH_BUG
/* If the filename ends in a slash and one of O_CREAT, O_WRONLY, O_RDWR
is specified, then fail.
Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
says that
"A pathname that contains at least one non-slash character and that
ends with one or more trailing slashes shall be resolved as if a
single dot character ( '.' ) were appended to the pathname."
and
"The special filename dot shall refer to the directory specified by
its predecessor."
If the named file already exists as a directory, then
- if O_CREAT is specified, open() must fail because of the semantics
of O_CREAT,
- if O_WRONLY or O_RDWR is specified, open() must fail because POSIX
<http://www.opengroup.org/susv3/functions/open.html> says that it
fails with errno = EISDIR in this case.
If the named file does not exist or does not name a directory, then
- if O_CREAT is specified, open() must fail since open() cannot create
directories,
- if O_WRONLY or O_RDWR is specified, open() must fail because the
file does not contain a '.' directory. */
if (flags & (O_CREAT | O_WRONLY | O_RDWR))
{
size_t len = strlen (filename);
if (len > 0 && filename[len - 1] == '/')
{
errno = EISDIR;
return -1;
}
}
# endif
fd = orig_openat (dfd, filename, flags, mode);
# if OPEN_TRAILING_SLASH_BUG
/* If the filename ends in a slash and fd does not refer to a directory,
then fail.
Rationale: POSIX <http://www.opengroup.org/susv3/basedefs/xbd_chap04.html>
says that
"A pathname that contains at least one non-slash character and that
ends with one or more trailing slashes shall be resolved as if a
single dot character ( '.' ) were appended to the pathname."
and
"The special filename dot shall refer to the directory specified by
its predecessor."
If the named file without the slash is not a directory, open() must fail
with ENOTDIR. */
if (fd >= 0)
{
/* We know len is positive, since open did not fail with ENOENT. */
size_t len = strlen (filename);
if (filename[len - 1] == '/')
{
struct stat statbuf;
if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))
{
close (fd);
errno = ENOTDIR;
return -1;
}
}
}
# endif
return fd;
}
#else /* !HAVE_OPENAT */
# include "dosname.h" /* solely for definition of IS_ABSOLUTE_FILE_NAME */
# include "openat-priv.h"
# include "save-cwd.h"
/* Replacement for Solaris' openat function.
<http://www.google.com/search?q=openat+site:docs.sun.com>
First, try to simulate it via open ("/proc/self/fd/FD/FILE").
Failing that, simulate it by doing save_cwd/fchdir/open/restore_cwd.
If either the save_cwd or the restore_cwd fails (relatively unlikely),
then give a diagnostic and exit nonzero.
Otherwise, upon failure, set errno and return -1, as openat does.
Upon successful completion, return a file descriptor. */
int
openat (int fd, char const *file, int flags, ...)
{
mode_t mode = 0;
if (flags & O_CREAT)
{
va_list arg;
va_start (arg, flags);
/* We have to use PROMOTED_MODE_T instead of mode_t, otherwise GCC 4
creates crashing code when 'mode_t' is smaller than 'int'. */
mode = va_arg (arg, PROMOTED_MODE_T);
va_end (arg);
}
return openat_permissive (fd, file, flags, mode, NULL);
}
/* Like openat (FD, FILE, FLAGS, MODE), but if CWD_ERRNO is
nonnull, set *CWD_ERRNO to an errno value if unable to save
or restore the initial working directory. This is needed only
the first time remove.c's remove_dir opens a command-line
directory argument.
If a previous attempt to restore the current working directory
failed, then we must not even try to access a '.'-relative name.
It is the caller's responsibility not to call this function
in that case. */
int
openat_permissive (int fd, char const *file, int flags, mode_t mode,
int *cwd_errno)
{
struct saved_cwd saved_cwd;
int saved_errno;
int err;
bool save_ok;
if (fd == AT_FDCWD || IS_ABSOLUTE_FILE_NAME (file))
return open (file, flags, mode);
{
char buf[OPENAT_BUFFER_SIZE];
char *proc_file = openat_proc_name (buf, fd, file);
if (proc_file)
{
int open_result = open (proc_file, flags, mode);
int open_errno = errno;
if (proc_file != buf)
free (proc_file);
/* If the syscall succeeds, or if it fails with an unexpected
errno value, then return right away. Otherwise, fall through
and resort to using save_cwd/restore_cwd. */
if (0 <= open_result || ! EXPECTED_ERRNO (open_errno))
{
errno = open_errno;
return open_result;
}
}
}
save_ok = (save_cwd (&saved_cwd) == 0);
if (! save_ok)
{
if (! cwd_errno)
openat_save_fail (errno);
*cwd_errno = errno;
}
if (0 <= fd && fd == saved_cwd.desc)
{
/* If saving the working directory collides with the user's
requested fd, then the user's fd must have been closed to
begin with. */
free_cwd (&saved_cwd);
errno = EBADF;
return -1;
}
err = fchdir (fd);
saved_errno = errno;
if (! err)
{
err = open (file, flags, mode);
saved_errno = errno;
if (save_ok && restore_cwd (&saved_cwd) != 0)
{
if (! cwd_errno)
{
/* Don't write a message to just-created fd 2. */
saved_errno = errno;
if (err == STDERR_FILENO)
close (err);
openat_restore_fail (saved_errno);
}
*cwd_errno = errno;
}
}
free_cwd (&saved_cwd);
errno = saved_errno;
return err;
}
/* Return true if our openat implementation must resort to
using save_cwd and restore_cwd. */
bool
openat_needs_fchdir (void)
{
bool needs_fchdir = true;
int fd = open ("/", O_SEARCH);
if (0 <= fd)
{
char buf[OPENAT_BUFFER_SIZE];
char *proc_file = openat_proc_name (buf, fd, ".");
if (proc_file)
{
needs_fchdir = false;
if (proc_file != buf)
free (proc_file);
}
close (fd);
}
return needs_fchdir;
}
#endif /* !HAVE_OPENAT */