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/* Invoke opendir, but avoid some glitches.
Copyright (C) 2009-2020 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 <https://www.gnu.org/licenses/>. */
/* Written by Eric Blake. */
#include <config.h>
#include "dirent-safer.h"
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
/* Like opendir, but do not clobber stdin, stdout, or stderr. */
DIR *
opendir_safer (char const *name)
{
DIR *dp = opendir (name);
if (dp)
{
int fd = dirfd (dp);
if (0 <= fd && fd <= STDERR_FILENO)
{
/* If fdopendir is native (as on Linux), then it is safe to
assume dirfd(fdopendir(n))==n. If we are using the
gnulib module fdopendir, then this guarantee is not met,
but fdopendir recursively calls opendir_safer up to 3
times to at least get a safe fd. If fdopendir is not
present but dirfd is accurate (as on cygwin 1.5.x), then
we recurse up to 3 times ourselves. Finally, if dirfd
always fails (as on mingw), then we are already safe. */
DIR *newdp;
int e;
#if HAVE_FDOPENDIR || GNULIB_FDOPENDIR
int f = fcntl (fd, F_DUPFD_CLOEXEC, STDERR_FILENO + 1);
if (f < 0)
{
e = errno;
newdp = NULL;
}
else
{
newdp = fdopendir (f);
e = errno;
if (! newdp)
close (f);
}
#else /* !FDOPENDIR */
newdp = opendir_safer (name);
e = errno;
#endif
closedir (dp);
errno = e;
dp = newdp;
}
}
return dp;
}
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