* lib/fileutils.rb (FileUtils::remove_entry_secure): there is a

race condition in the case where the given path is a directory,
  and some other user can move that directory, and create a
  symlink while this method is executing.
  Reported by: Nicholas Jefferson <nicholas at pythonic.com.au>


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30896 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Fri Feb 18 19:31:31 2011  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* lib/fileutils.rb (FileUtils::remove_entry_secure): there is a
+	  race condition in the case where the given path is a directory,
+	  and some other user can move that directory, and create a
+	  symlink while this method is executing.
+	  Reported by: Nicholas Jefferson <nicholas at pythonic.com.au>
+
 Fri Feb 18 00:28:39 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
 
 	* compile.c (get_exception_sym2type): guard temporary object from GC.

lib/fileutils.rb

@@ -667,10 +667,10 @@ module FileUtils
   # removing directories.  This requires the current process is the
   # owner of the removing whole directory tree, or is the super user (root).
   #
-  # WARNING: You must ensure that *ALL* parent directories are not
-  # world writable.  Otherwise this method does not work.
-  # Only exception is temporary directory like /tmp and /var/tmp,
-  # whose permission is 1777.
+  # WARNING: You must ensure that *ALL* parent directories cannot be
+  # moved by other untrusted users.  For example, parent directories
+  # should not be owned by untrusted users, and should not be world
+  # writable except when the sticky bit set.
   #
   # WARNING: Only the owner of the removing directory tree, or Unix super
   # user (root) should invoke this method.  Otherwise this method does not
@@ -713,6 +713,11 @@ module FileUtils
       end
       f.chown euid, -1
       f.chmod 0700
+      unless fu_stat_identical_entry?(st, File.lstat(fullpath))
+        # TOC-to-TOU attack?
+        File.unlink fullpath
+        return
+      end
     }
     # ---- tree root is frozen ----
     root = Entry_.new(path)