1 files changed, 104 insertions, 0 deletions
diff --git a/lib/chown.c b/lib/chown.c
new file mode 100644
index 0000000..b7786f6
--- /dev/null
+++ b/lib/chown.c
@@ -0,0 +1,104 @@
+/* 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, 2005, 2006, 2007 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.
+
+   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, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <stdbool.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+
+/* 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
+rpl_chown (const char *file, uid_t uid, gid_t gid)
+{
+#if CHOWN_FAILS_TO_HONOR_ID_OF_NEGATIVE_ONE
+  if (gid == (gid_t) -1 || uid == (uid_t) -1)
+    {
+      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
+
+#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));
+
+	close (fd);
+
+	if (! fchown_socket_failure)
+	  {
+	    errno = saved_errno;
+	    return result;
+	  }
+      }
+    else if (errno != EACCES)
+      return -1;
+  }
+#endif
+
+  return chown (file, uid, gid);
+}