Complete work on 3.2 for render_data_leak patch.

Render could leak access to external files before this patch.
A previous patch(CVE-2016-0752), attempted to fix this. However the tests
were miss-placed outside the TestCase subclass, so they were not running.

We should allow :file to be outside rails root, but anything else must
be inside the rails view directory.

The implementation has changed a bit though. Now the patch is more
similar with the 4.x series patches.
Now `render 'foo/bar'`, will add a special key in the options
hash, and not use the :file one, so when we look up that file, we
don't set the fallbacks, and only lookup a template, to constraint the
folders that can be accessed.

CVE-2016-2097

1 files changed, 19 insertions, 7 deletions

diff --git a/actionpack/lib/action_view/path_set.rb b/actionpack/lib/action_view/path_set.rb
index bbb1af8154..1c54a970cb 100644
--- a/actionpack/lib/action_view/path_set.rb
+++ b/actionpack/lib/action_view/path_set.rb
@@ -58,23 +58,35 @@ module ActionView #:nodoc:
       find_all(*args).first || raise(MissingTemplate.new(self, *args))
     end
 
+    def find_file(path, prefixes = [], *args)
+      _find_all(path, prefixes, args, true).first || raise(MissingTemplate.new(self, path, prefixes, *args))
+    end
+
     def find_all(path, prefixes = [], *args)
+      _find_all path, prefixes, args, false
+    end
+
+    def exists?(path, prefixes, *args)
+      find_all(path, prefixes, *args).any?
+    end
+
+    private
+
+    def _find_all(path, prefixes, args, outside_app)
       prefixes = [prefixes] if String === prefixes
       prefixes.each do |prefix|
         paths.each do |resolver|
-          templates = resolver.find_all(path, prefix, *args)
+          if outside_app
+            templates = resolver.find_all_anywhere(path, prefix, *args)
+          else
+            templates = resolver.find_all(path, prefix, *args)
+          end
           return templates unless templates.empty?
         end
       end
       []
     end
 
-    def exists?(path, prefixes, *args)
-      find_all(path, prefixes, *args).any?
-    end
-
-    private
-
     def typecast(paths)
       paths.map do |path|
         case path