/* 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 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ Copyright (C) 1997, 2004-2007, 2009 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 2, or (at your option)
- any later version.
+ 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
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, write to the Free Software Foundation,
- Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
+
+/* Specification. */
+#include <unistd.h>
+
+#include <stdbool.h>
#include <sys/types.h>
-#ifdef HAVE_UNISTD_H
-# include <unistd.h>
-#endif
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
-/* FIXME: describe. */
+/* Below we refer to the system's chown(). */
+#undef chown
+
+/* The results of open() in this file are not used with fchdir,
+ therefore save some unnecessary work in fchdir.c. */
+#undef open
+#undef close
+
+/* 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
-chown (file, gid, uid)
- const char *file;
- gid_t git;
- uid_t uit;
+rpl_chown (const char *file, uid_t uid, gid_t gid)
{
+#if HAVE_CHOWN
+# if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
if (gid == (gid_t) -1 || uid == (uid_t) -1)
{
- /* Stat file to get id(s) that will remain unchanged. */
- FIXME
+ struct stat file_stats;
+
+ /* Stat file to get id(s) that should remain unchanged. */
+ if (stat (file, &file_stats))
+ return -1;
+
+ if (gid == (gid_t) -1)
+ gid = file_stats.st_gid;
+
+ if (uid == (uid_t) -1)
+ uid = file_stats.st_uid;
}
+# endif
-#undef chown
+# if CHOWN_MODIFIES_SYMLINK
+ {
+ /* Handle the case in which the system-supplied chown function
+ does *not* follow symlinks. Instead, it changes permissions
+ on the symlink itself. To work around that, we open the
+ file (but this can fail due to lack of read or write permission) and
+ use fchown on the resulting descriptor. */
+ int open_flags = O_NONBLOCK | O_NOCTTY;
+ int fd = open (file, O_RDONLY | open_flags);
+ if (0 <= fd
+ || (errno == EACCES
+ && 0 <= (fd = open (file, O_WRONLY | open_flags))))
+ {
+ int result = fchown (fd, uid, gid);
+ int saved_errno = errno;
+
+ /* POSIX says fchown can fail with errno == EINVAL on sockets,
+ so fall back on chown in that case. */
+ struct stat sb;
+ bool fchown_socket_failure =
+ (result != 0 && saved_errno == EINVAL
+ && fstat (fd, &sb) == 0 && S_ISFIFO (sb.st_mode));
- return chown (file, gid, uid);
+ close (fd);
+
+ if (! fchown_socket_failure)
+ {
+ errno = saved_errno;
+ return result;
+ }
+ }
+ else if (errno != EACCES)
+ return -1;
+ }
+# endif
+
+ return chown (file, uid, gid);
+
+#else /* !HAVE_CHOWN */
+ errno = ENOSYS;
+ return -1;
+#endif
}