From 9441acff1a867f672449fef0ecf8908016652d51 Mon Sep 17 00:00:00 2001
From: Andrew Carpenter <andrew@criticaljuncture.org>
Date: Thu, 28 Jul 2016 16:12:21 -0700
Subject: [PATCH] ensure tag/content_tag escapes " in attribute vals

Many helpers mark content as HTML-safe without escaping double quotes -- including `sanitize`. Regardless of whether or not the attribute values are HTML-escaped, we want to be sure they don't include double quotes, as that can cause XSS issues. For example: `content_tag(:div, "foo", title: sanitize('" onmouseover="alert(1);//'))`

CVE-2016-6316
---
 actionpack/lib/action_view/helpers/tag_helper.rb | 16 ++++++++++++----
 actionpack/test/template/tag_helper_test.rb      | 10 ++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/actionpack/lib/action_view/helpers/tag_helper.rb b/actionpack/lib/action_view/helpers/tag_helper.rb
index 7f58a27..6b659a7 100644
--- a/actionpack/lib/action_view/helpers/tag_helper.rb
+++ b/actionpack/lib/action_view/helpers/tag_helper.rb
@@ -10,6 +10,7 @@ module ActionView
     module TagHelper
       extend ActiveSupport::Concern
       include CaptureHelper
+      include OutputSafetyHelper
 
       BOOLEAN_ATTRIBUTES = %w(disabled readonly multiple checked autobuffer
                            autoplay controls loop selected hidden scoped async
@@ -141,20 +142,27 @@ module ActionView
                   unless v.is_a?(String) || v.is_a?(Symbol) || v.is_a?(BigDecimal)
                     v = v.to_json
                   end
-                  v = ERB::Util.html_escape(v) if escape
-                  attrs << %(data-#{k.to_s.dasherize}="#{v}")
+                  attrs << tag_option("data-#{k.to_s.dasherize}", v, escape)
                 end
               elsif BOOLEAN_ATTRIBUTES.include?(key)
                 attrs << %(#{key}="#{key}") if value
               elsif !value.nil?
                 final_value = value.is_a?(Array) ? value.join(" ") : value
-                final_value = ERB::Util.html_escape(final_value) if escape
-                attrs << %(#{key}="#{final_value}")
+                attrs << tag_option(key, value, escape)
               end
             end
             " #{attrs.sort * ' '}".html_safe unless attrs.empty?
           end
         end
+
+        def tag_option(key, value, escape)
+          if value.is_a?(Array)
+            value = escape ? safe_join(value, " ") : value.join(" ")
+          else
+            value = escape ? ERB::Util.html_escape(value) : value
+          end
+          %(#{key}="#{value.gsub(/"/, '&quot;'.freeze)}")
+        end
     end
   end
 end
diff --git a/actionpack/test/template/tag_helper_test.rb b/actionpack/test/template/tag_helper_test.rb
index e362955..9c3d636 100644
--- a/actionpack/test/template/tag_helper_test.rb
+++ b/actionpack/test/template/tag_helper_test.rb
@@ -101,6 +101,16 @@ class TagHelperTest < ActionView::TestCase
     end
   end
 
+  def test_tag_does_not_honor_html_safe_double_quotes_as_attributes
+    assert_dom_equal '<p title="&quot;">content</p>',
+      content_tag('p', "content", title: '"'.html_safe)
+  end
+
+  def test_data_tag_does_not_honor_html_safe_double_quotes_as_attributes
+    assert_dom_equal '<p data-title="&quot;">content</p>',
+      content_tag('p', "content", data: { title: '"'.html_safe })
+  end
+
   def test_skip_invalid_escaped_attributes
     ['&1;', '&#1dfa3;', '& #123;'].each do |escaped|
       assert_equal %(<a href="#{escaped.gsub(/&/, '&amp;')}" />), tag('a', :href => escaped)
-- 
2.8.1