1 files changed, 116 insertions, 0 deletions
diff --git a/lib/fchownat.c b/lib/fchownat.c
new file mode 100644
index 0000000..ff368d3
--- /dev/null
+++ b/lib/fchownat.c
@@ -0,0 +1,116 @@
+/* This function serves as replacement for a missing fchownat function,
+   as well as a work around for the fchownat bug in glibc-2.4:
+    <https://lists.ubuntu.com/archives/ubuntu-users/2006-September/093218.html>
+   when the buggy fchownat-with-AT_SYMLINK_NOFOLLOW operates on a symlink, it
+   mistakenly affects the symlink referent, rather than the symlink itself.
+
+   Copyright (C) 2006-2007, 2009-2022 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 Jim Meyering */
+
+#include <config.h>
+
+/* Specification.  */
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "openat.h"
+
+#if !HAVE_FCHOWNAT
+
+/* Replacement for Solaris' function by the same name.
+   Invoke chown or lchown on file, FILE, using OWNER and GROUP, in the
+   directory open on descriptor FD.  If FLAG is AT_SYMLINK_NOFOLLOW, then
+   use lchown, otherwise, use chown.  If possible, do it without changing
+   the working directory.  Otherwise, resort to using save_cwd/fchdir,
+   then (chown|lchown)/restore_cwd.  If either the save_cwd or the
+   restore_cwd fails, then give a diagnostic and exit nonzero.  */
+
+# define AT_FUNC_NAME fchownat
+# define AT_FUNC_F1 lchown
+# define AT_FUNC_F2 chown
+# define AT_FUNC_USE_F1_COND AT_SYMLINK_NOFOLLOW
+# define AT_FUNC_POST_FILE_PARAM_DECLS , uid_t owner, gid_t group, int flag
+# define AT_FUNC_POST_FILE_ARGS        , owner, group
+# include "at-func.c"
+# undef AT_FUNC_NAME
+# undef AT_FUNC_F1
+# undef AT_FUNC_F2
+# undef AT_FUNC_USE_F1_COND
+# undef AT_FUNC_POST_FILE_PARAM_DECLS
+# undef AT_FUNC_POST_FILE_ARGS
+
+#else /* HAVE_FCHOWNAT */
+
+# undef fchownat
+
+# if FCHOWNAT_NOFOLLOW_BUG
+
+/* Failure to handle AT_SYMLINK_NOFOLLOW requires the /proc/self/fd or
+   fchdir workaround to call lchown for lchownat, but there is no need
+   to penalize chownat.  */
+static int
+local_lchownat (int fd, char const *file, uid_t owner, gid_t group);
+
+#  define AT_FUNC_NAME local_lchownat
+#  define AT_FUNC_F1 lchown
+#  define AT_FUNC_POST_FILE_PARAM_DECLS , uid_t owner, gid_t group
+#  define AT_FUNC_POST_FILE_ARGS        , owner, group
+#  include "at-func.c"
+#  undef AT_FUNC_NAME
+#  undef AT_FUNC_F1
+#  undef AT_FUNC_POST_FILE_PARAM_DECLS
+#  undef AT_FUNC_POST_FILE_ARGS
+
+# endif
+
+/* Work around bugs with trailing slash, using the same workarounds as
+   chown and lchown.  */
+
+int
+rpl_fchownat (int fd, char const *file, uid_t owner, gid_t group, int flag)
+{
+# if FCHOWNAT_NOFOLLOW_BUG
+  if (flag == AT_SYMLINK_NOFOLLOW)
+    return local_lchownat (fd, file, owner, group);
+# endif
+# if FCHOWNAT_EMPTY_FILENAME_BUG
+  if (file[0] == '\0')
+    {
+      errno = ENOENT;
+      return -1;
+    }
+# endif
+# if CHOWN_TRAILING_SLASH_BUG
+  {
+    size_t len = strlen (file);
+    struct stat st;
+    if (len && file[len - 1] == '/')
+      {
+        if (fstatat (fd, file, &st, 0))
+          return -1;
+        if (flag == AT_SYMLINK_NOFOLLOW)
+          return fchownat (fd, file, owner, group, 0);
+      }
+  }
+# endif
+  return fchownat (fd, file, owner, group, flag);
+}
+
+#endif /* HAVE_FCHOWNAT */