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/* provide consistent interface to chown for systems that don't interpret
an ID of -1 as meaning "don't change the corresponding ID".
Copyright (C) 1997, 2004-2007, 2009-2025 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
/* Specification. */
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#if !HAVE_CHOWN
/* Simple stub that always fails with ENOSYS, for mingw. */
int
chown (_GL_UNUSED const char *file, _GL_UNUSED uid_t uid,
_GL_UNUSED gid_t gid)
{
errno = ENOSYS;
return -1;
}
#else /* HAVE_CHOWN */
/* Below we refer to the system's chown(). */
# undef chown
/* Provide a more-closely POSIX-conforming version of chown on
systems with one or both of the following problems:
- chown doesn't treat an ID of -1 as meaning
"don't change the corresponding ID".
- chown doesn't dereference symlinks. */
int
rpl_chown (const char *file, uid_t uid, gid_t gid)
{
# if (CHOWN_CHANGE_TIME_BUG || CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE \
|| CHOWN_TRAILING_SLASH_BUG)
struct stat st;
bool stat_valid = false;
# endif
int result;
# if CHOWN_CHANGE_TIME_BUG /* OpenBSD 7.2 */
if (gid != (gid_t) -1 || uid != (uid_t) -1)
{
if (stat (file, &st))
return -1;
stat_valid = true;
}
# endif
# if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE /* some very old platforms */
if (gid == (gid_t) -1 || uid == (uid_t) -1)
{
/* Stat file to get id(s) that should remain unchanged. */
if (!stat_valid && stat (file, &st))
return -1;
if (gid == (gid_t) -1)
gid = st.st_gid;
if (uid == (uid_t) -1)
uid = st.st_uid;
}
# endif
# if CHOWN_MODIFIES_SYMLINK /* some very old platforms */
/* The system-supplied chown function does not follow symlinks.
If the file is a symlink, open the file (following symlinks), and
fchown the resulting descriptor. Although the open might fail
due to lack of permissions, it's the best we can easily do. */
char linkbuf[1];
if (0 <= readlink (file, linkbuf, sizeof linkbuf))
{
int open_flags = O_NONBLOCK | O_NOCTTY | O_CLOEXEC;
int fd = open (file, O_RDONLY | open_flags);
if (fd < 0
&& (errno != EACCES
|| ((fd = open (file, O_WRONLY | open_flags)) < 0))
&& (errno != EACCES || O_EXEC == O_RDONLY
|| ((fd = open (file, O_EXEC | open_flags)) < 0))
&& (errno != EACCES || O_SEARCH == O_RDONLY || O_SEARCH == O_EXEC
|| ((fd = open (file, O_SEARCH | open_flags)) < 0)))
return fd;
int r = fchown (fd, uid, gid);
int err = errno;
close (fd);
errno = err;
return r;
}
# endif
# if CHOWN_TRAILING_SLASH_BUG /* macOS 12.5, FreeBSD 7.2, AIX 7.3.1, Solaris 9 */
if (!stat_valid)
{
size_t len = strlen (file);
if (len && file[len - 1] == '/' && stat (file, &st))
return -1;
}
# endif
result = chown (file, uid, gid);
# if CHOWN_CHANGE_TIME_BUG /* OpenBSD 7.2 */
if (result == 0 && stat_valid
&& (uid == st.st_uid || uid == (uid_t) -1)
&& (gid == st.st_gid || gid == (gid_t) -1))
{
/* No change in ownership, but at least one argument was not -1,
so we are required to update ctime. Since chown succeeded,
we assume that chmod will do likewise. Fortunately, on all
known systems where a 'no-op' chown skips the ctime update, a
'no-op' chmod still does the trick. */
result = chmod (file, st.st_mode & (S_IRWXU | S_IRWXG | S_IRWXO
| S_ISUID | S_ISGID | S_ISVTX));
}
# endif
return result;
}
#endif /* HAVE_CHOWN */
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