FileHandler should not be called for files outside the root

FileHandler#matches? should return false for files that are outside the
"root" path.

Conflicts:
	actionpack/lib/action_dispatch/middleware/static.rb

actionpack/lib/action_dispatch/middleware/static.rb

@@ -14,7 +14,8 @@ def match?(path)
       path = unescape_path(path)
       return false unless path.valid_encoding?
 
-      full_path = path.empty? ? @root : File.join(@root, escape_glob_chars(path))
+      full_path = path.empty? ? @root : File.join(@root,
+        clean_path_info(escape_glob_chars(path)))
       paths = "#{full_path}#{ext}"
 
       matches = Dir[paths]
@@ -43,6 +44,25 @@ def unescape_path(path)
     def escape_glob_chars(path)
       path.gsub(/[*?{}\[\]]/, "\\\\\\&")
     end
+
+    private
+
+    PATH_SEPS = Regexp.union(*[::File::SEPARATOR, ::File::ALT_SEPARATOR].compact)
+
+    def clean_path_info(path_info)
+      parts = path_info.split PATH_SEPS
+
+      clean = []
+
+      parts.each do |part|
+        next if part.empty? || part == '.'
+        part == '..' ? clean.pop : clean << part
+      end
+
+      clean.unshift '/' if parts.empty? || parts.first.empty?
+
+      ::File.join(*clean)
+    end
   end
 
   class Static

actionpack/test/dispatch/static_test.rb

@@ -147,19 +147,37 @@ class StaticTest < ActiveSupport::TestCase
   }
 
   def setup
-    @app = ActionDispatch::Static.new(DummyApp, "#{FIXTURE_LOAD_PATH}/public", "public, max-age=60")
+    @root = "#{FIXTURE_LOAD_PATH}/public"
+    @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end
 
   def public_path
     "public"
   end
 
   include StaticTests
+
+  def test_custom_handler_called_when_file_is_outside_root
+    filename = 'shared.html.erb'
+    assert File.exist?(File.join(@root, '..', filename))
+    env = {
+      "REQUEST_METHOD"=>"GET",
+      "REQUEST_PATH"=>"/..%2F#{filename}",
+      "PATH_INFO"=>"/..%2F#{filename}",
+      "REQUEST_URI"=>"/..%2F#{filename}",
+      "HTTP_VERSION"=>"HTTP/1.1",
+      "SERVER_NAME"=>"localhost",
+      "SERVER_PORT"=>"8080",
+      "QUERY_STRING"=>""
+    }
+    assert_equal(DummyApp.call(nil), @app.call(env))
+  end
 end
 
 class StaticEncodingTest < StaticTest
   def setup
-    @app = ActionDispatch::Static.new(DummyApp, "#{FIXTURE_LOAD_PATH}/公共", "public, max-age=60")
+    @root = "#{FIXTURE_LOAD_PATH}/公共"
+    @app = ActionDispatch::Static.new(DummyApp, @root, "public, max-age=60")
   end
 
   def public_path