Always reject files external to app

Previously, when using `render file:`, it was possible to render files
not only at an absolute path or relative to the current directory, but
relative to ANY view paths. This was probably done for absolutely
maximum compatibility when addressing CVE-2016-0752, but I think is
unlikely to be used in practice.

Tihs commit removes the ability to `render file:` with a path relative
to a non-fallback view path.

Make FallbackResolver.new private

To ensure nobody is making FallbackResolvers other than "/" and "".

Make reject_files_external_... no-op for fallbacks

Because there are only two values used for path: "" and "/", and
File.join("", "") == File.join("/", "") == "/", this method was only
testing that the absolute paths started at "/" (which of course all do).

This commit doesn't change any behaviour, but it makes it explicit that
the FallbackFileSystemResolver works this way.

Remove outside_app_allowed argument

Deprecate find_all_anywhere

This is now equivalent to find_all

Remove outside_app argument

Deprecate find_file for find

Both LookupContext#find_file and PathSet#find_file are now equivalent to
their respective #find methods.

7 files changed, 30 insertions, 35 deletions

diff --git a/actionview/lib/action_view/lookup_context.rb b/actionview/lib/action_view/lookup_context.rb
index fd3d025cbf..b9a8cc129c 100644
--- a/actionview/lib/action_view/lookup_context.rb
+++ b/actionview/lib/action_view/lookup_context.rb
@@ -130,9 +130,8 @@ module ActionView
       end
       alias :find_template :find
 
-      def find_file(name, prefixes = [], partial = false, keys = [], options = {})
-        @view_paths.find_file(*args_for_lookup(name, prefixes, partial, keys, options))
-      end
+      alias :find_file :find
+      deprecate :find_file
 
       def find_all(name, prefixes = [], partial = false, keys = [], options = {})
         @view_paths.find_all(*args_for_lookup(name, prefixes, partial, keys, options))
diff --git a/actionview/lib/action_view/path_set.rb b/actionview/lib/action_view/path_set.rb
index 691b53e2da..d54749d8e3 100644
--- a/actionview/lib/action_view/path_set.rb
+++ b/actionview/lib/action_view/path_set.rb
@@ -48,12 +48,11 @@ 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
+    alias :find_file :find
+    deprecate :find_file
 
     def find_all(path, prefixes = [], *args)
-      _find_all path, prefixes, args, false
+      _find_all path, prefixes, args
     end
 
     def exists?(path, prefixes, *args)
@@ -71,15 +70,11 @@ module ActionView #:nodoc:
 
     private
 
-      def _find_all(path, prefixes, args, outside_app)
+      def _find_all(path, prefixes, args)
         prefixes = [prefixes] if String === prefixes
         prefixes.each do |prefix|
           paths.each do |resolver|
-            if outside_app
-              templates = resolver.find_all_anywhere(path, prefix, *args)
-            else
-              templates = resolver.find_all(path, prefix, *args)
-            end
+            templates = resolver.find_all(path, prefix, *args)
             return templates unless templates.empty?
           end
         end
diff --git a/actionview/lib/action_view/renderer/template_renderer.rb b/actionview/lib/action_view/renderer/template_renderer.rb
index 698f535b49..e30016a027 100644
--- a/actionview/lib/action_view/renderer/template_renderer.rb
+++ b/actionview/lib/action_view/renderer/template_renderer.rb
@@ -30,7 +30,7 @@ module ActionView
             Template::File.new(options[:file])
           else
             ActiveSupport::Deprecation.warn "render file: should be given the absolute path to a file"
-            @lookup_context.with_fallbacks.find_file(options[:file], nil, false, keys, @details)
+            @lookup_context.with_fallbacks.find_template(options[:file], nil, false, keys, @details)
           end
         elsif options.key?(:inline)
           handler = Template.handler_for_extension(options[:type] || "erb")
diff --git a/actionview/lib/action_view/template/resolver.rb b/actionview/lib/action_view/template/resolver.rb
index 095e6cc3a1..d5cb3c823a 100644
--- a/actionview/lib/action_view/template/resolver.rb
+++ b/actionview/lib/action_view/template/resolver.rb
@@ -118,17 +118,12 @@ module ActionView
       locals = locals.map(&:to_s).sort!.freeze
 
       cached(key, [name, prefix, partial], details, locals) do
-        find_templates(name, prefix, partial, details, false, locals)
+        find_templates(name, prefix, partial, details, locals)
       end
     end
 
-    def find_all_anywhere(name, prefix, partial = false, details = {}, key = nil, locals = [])
-      locals = locals.map(&:to_s).sort!.freeze
-
-      cached(key, [name, prefix, partial], details, locals) do
-        find_templates(name, prefix, partial, details, true, locals)
-      end
-    end
+    alias :find_all_anywhere :find_all
+    deprecate :find_all_anywhere
 
     def find_all_with_query(query) # :nodoc:
       @cache.cache_query(query) { find_template_paths(File.join(@path, query)) }
@@ -141,8 +136,8 @@ module ActionView
     # This is what child classes implement. No defaults are needed
     # because Resolver guarantees that the arguments are present and
     # normalized.
-    def find_templates(name, prefix, partial, details, outside_app_allowed = false, locals = [])
-      raise NotImplementedError, "Subclasses must implement a find_templates(name, prefix, partial, details, outside_app_allowed = false, locals = []) method"
+    def find_templates(name, prefix, partial, details, locals = [])
+      raise NotImplementedError, "Subclasses must implement a find_templates(name, prefix, partial, details, locals = []) method"
     end
 
     # Handles templates caching. If a key is given and caching is on
@@ -179,14 +174,14 @@ module ActionView
 
     private
 
-      def find_templates(name, prefix, partial, details, outside_app_allowed = false, locals)
+      def find_templates(name, prefix, partial, details, locals)
         path = Path.build(name, prefix, partial)
-        query(path, details, details[:formats], outside_app_allowed, locals)
+        query(path, details, details[:formats], locals)
       end
 
-      def query(path, details, formats, outside_app_allowed, locals)
+      def query(path, details, formats, locals)
         template_paths = find_template_paths_from_details(path, details)
-        template_paths = reject_files_external_to_app(template_paths) unless outside_app_allowed
+        template_paths = reject_files_external_to_app(template_paths)
 
         template_paths.map do |template|
           build_template(template, path.virtual, locals)
@@ -360,6 +355,8 @@ module ActionView
   # The same as FileSystemResolver but does not allow templates to store
   # a virtual path since it is invalid for such resolvers.
   class FallbackFileSystemResolver < FileSystemResolver #:nodoc:
+    private_class_method :new
+
     def self.instances
       [new(""), new("/")]
     end
@@ -367,5 +364,9 @@ module ActionView
     def build_template(template, virtual_path, locals)
       super(template, nil, locals)
     end
+
+    def reject_files_external_to_app(files)
+      files
+    end
   end
 end
diff --git a/actionview/lib/action_view/testing/resolvers.rb b/actionview/lib/action_view/testing/resolvers.rb
index a16dc0096e..11ae9f731c 100644
--- a/actionview/lib/action_view/testing/resolvers.rb
+++ b/actionview/lib/action_view/testing/resolvers.rb
@@ -23,7 +23,7 @@ module ActionView #:nodoc:
 
     private
 
-      def query(path, exts, _, _, locals)
+      def query(path, exts, _, locals)
         query = +""
         EXTENSIONS.each_key do |ext|
           query << "(" << exts[ext].map { |e| e && Regexp.escape(".#{e}") }.join("|") << "|)"
@@ -47,7 +47,7 @@ module ActionView #:nodoc:
   end
 
   class NullResolver < PathResolver
-    def query(path, exts, _, _, locals)
+    def query(path, exts, _, locals)
       handler, format, variant = extract_handler_and_format_and_variant(path)
       [ActionView::Template.new("Template generated by Null Resolver", path.virtual, handler, virtual_path: path.virtual, format: format, variant: variant, locals: locals)]
     end
diff --git a/actionview/test/template/fallback_file_system_resolver_test.rb b/actionview/test/template/fallback_file_system_resolver_test.rb
index 304cdb8a03..fa770f3a15 100644
--- a/actionview/test/template/fallback_file_system_resolver_test.rb
+++ b/actionview/test/template/fallback_file_system_resolver_test.rb
@@ -4,7 +4,7 @@ require "abstract_unit"
 
 class FallbackFileSystemResolverTest < ActiveSupport::TestCase
   def setup
-    @root_resolver = ActionView::FallbackFileSystemResolver.new("/")
+    @root_resolver = ActionView::FallbackFileSystemResolver.send(:new, "/")
   end
 
   def test_should_have_no_virtual_path
diff --git a/actionview/test/template/lookup_context_test.rb b/actionview/test/template/lookup_context_test.rb
index 3e357fe1a7..72e1f50fdf 100644
--- a/actionview/test/template/lookup_context_test.rb
+++ b/actionview/test/template/lookup_context_test.rb
@@ -143,16 +143,16 @@ class LookupContextTest < ActiveSupport::TestCase
     assert_deprecated do
       @lookup_context.with_fallbacks do
         assert_equal 3, @lookup_context.view_paths.size
-        assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.new("")
-        assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.new("/")
+        assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.instances[0]
+        assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.instances[1]
       end
     end
 
     @lookup_context = @lookup_context.with_fallbacks
 
     assert_equal 3, @lookup_context.view_paths.size
-    assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.new("")
-    assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.new("/")
+    assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.instances[0]
+    assert_includes @lookup_context.view_paths, ActionView::FallbackFileSystemResolver.instances[1]
   end
 
   test "add fallbacks just once in nested fallbacks calls" do