Switch to on-by-default XSS escaping for rails.

  This consists of:

  * String#html_safe! a method to mark a string as 'safe'
  * ActionView::SafeBuffer a string subclass which escapes anything unsafe which is concatenated to it
  * Calls to String#html_safe! throughout the rails helpers
  * a 'raw' helper which lets you concatenate trusted HTML from non-safety-aware sources (e.g. presantized strings in the DB)
  * New ERB implementation based on erubis which uses a SafeBuffer instead of a String

Hat tip to Django for the inspiration.

1 files changed, 11 insertions, 1 deletions

diff --git a/actionpack/lib/action_view/erb/util.rb b/actionpack/lib/action_view/erb/util.rb
index 3c77c5ce76..f767a5e27e 100644
--- a/actionpack/lib/action_view/erb/util.rb
+++ b/actionpack/lib/action_view/erb/util.rb
@@ -15,9 +15,19 @@ class ERB
     #   puts html_escape("is a > 0 & a < 10?")
     #   # => is a &gt; 0 &amp; a &lt; 10?
     def html_escape(s)
-      s.to_s.gsub(/[&"><]/) { |special| HTML_ESCAPE[special] }
+      s = s.to_s
+      if s.html_safe?
+        s
+      else
+        s.gsub(/[&"><]/) { |special| HTML_ESCAPE[special] }.html_safe!
+      end
     end
 
+    alias h html_escape
+
+    module_function :html_escape
+    module_function :h
+
     # A utility method for escaping HTML entities in JSON strings.
     # This method is also aliased as <tt>j</tt>.
     #