Introduce Template::File as new render file:

The previous behaviour of render file: was essentially the same as
render template:, except that templates can be specified as an absolute
path on the filesystem.

This makes sense for historic reasons, but now render file: is almost
exclusively used to render raw files (not .erb) like public/404.html. In
addition to complicating the code in template/resolver.rb, I think the
current behaviour is surprising to developers.

This commit deprecates the existing "lookup a template from anywhere"
behaviour and replaces it with "render this file exactly as it is on
disk". Handlers will no longer be used (it will render the same as if
the :raw handler was used), but formats (.html, .xml, etc) will still be
detected (and will default to :plain).

The existing render file: behaviour was the path through which Rails
apps were vulnerable in the recent CVE-2019-5418. Although the
vulnerability has been patched in a fully backwards-compatible way, I
think it's a strong hint that we should drop the existing
previously-vulnerable behaviour if it isn't a benefit to developers.

1 files changed, 12 insertions, 1 deletions

diff --git a/actionview/test/template/log_subscriber_test.rb b/actionview/test/template/log_subscriber_test.rb
index 85735139c1..8b160a7336 100644
--- a/actionview/test/template/log_subscriber_test.rb
+++ b/actionview/test/template/log_subscriber_test.rb
@@ -51,9 +51,20 @@ class AVLogSubscriberTest < ActiveSupport::TestCase
     def @view.combined_fragment_cache_key(*); "ahoy `controller` dependency"; end
   end
 
+  def test_render_template_template
+    Rails.stub(:root, File.expand_path(FIXTURE_LOAD_PATH)) do
+      @view.render(template: "test/hello_world")
+      wait
+
+      assert_equal 2, @logger.logged(:info).size
+      assert_match(/Rendering test\/hello_world\.erb/, @logger.logged(:info).first)
+      assert_match(/Rendered test\/hello_world\.erb/, @logger.logged(:info).last)
+    end
+  end
+
   def test_render_file_template
     Rails.stub(:root, File.expand_path(FIXTURE_LOAD_PATH)) do
-      @view.render(file: "test/hello_world")
+      @view.render(file: "#{FIXTURE_LOAD_PATH}/test/hello_world.erb")
       wait
 
       assert_equal 2, @logger.logged(:info).size