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, 28 insertions, 0 deletions

diff --git a/actionpack/lib/action_view/safe_buffer.rb b/actionpack/lib/action_view/safe_buffer.rb
new file mode 100644
index 0000000000..8ba9cd80d6
--- /dev/null
+++ b/actionpack/lib/action_view/safe_buffer.rb
@@ -0,0 +1,28 @@
+
+module ActionView #:nodoc:
+  class SafeBuffer < String
+    def <<(value)
+      if value.html_safe?
+        super(value)
+      else
+        super(CGI.escapeHTML(value))
+      end
+    end
+
+    def concat(value)
+      self << value
+    end
+
+    def html_safe?
+      true
+    end
+
+    def html_safe!
+      self
+    end
+
+    def to_s
+      self
+    end
+  end
+end
\ No newline at end of file