Added TextHelper#sanitize that can will remove any Javascript handlers, blocks, and forms from an input of HTML. This allows for use of HTML on public sites, but still be free of XSS issues. #1277 [Jamis Buck]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1298 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 55 insertions, 0 deletions

diff --git a/actionpack/lib/action_view/helpers/text_helper.rb b/actionpack/lib/action_view/helpers/text_helper.rb
index 6b89bec9f2..2cc4b68ec0 100644
--- a/actionpack/lib/action_view/helpers/text_helper.rb
+++ b/actionpack/lib/action_view/helpers/text_helper.rb
@@ -128,6 +128,61 @@ module ActionView
       def strip_links(text)
         text.gsub(/<a.*>(.*)<\/a>/m, '\1')
       end
+
+      # Try to require the html-scanner library
+      begin
+        require 'html/tokenizer'
+        require 'html/node'
+      rescue LoadError
+        # if there isn't a copy installed, use the vendor version in
+        # action controller
+        $:.unshift File.join(File.dirname(__FILE__), "..", "..",
+                      "action_controller", "vendor", "html-scanner")
+        require 'html/tokenizer'
+        require 'html/node'
+      end
+
+      VERBOTEN_TAGS = %w(form script) unless defined?(VERBOTEN_TAGS)
+      VERBOTEN_ATTRS = /^on/i unless defined?(VERBOTEN_ATTRS)
+
+      # Sanitizes the given HTML by making form and script tags into regular
+      # text, and removing all "onxxx" attributes (so that arbitrary Javascript
+      # cannot be executed). Also removes href attributes that start with
+      # "javascript:".
+      #
+      # Returns the sanitized text.
+      def sanitize(html)
+        # only do this if absolutely necessary
+        if html.index("<")
+          tokenizer = HTML::Tokenizer.new(html)
+          new_text = ""
+
+          while token = tokenizer.next
+            node = HTML::Node.parse(nil, 0, 0, token, false)
+            new_text << case node
+              when HTML::Tag
+                if VERBOTEN_TAGS.include?(node.name)
+                  node.to_s.gsub(/</, "&lt;")
+                else
+                  if node.closing != :close
+                    node.attributes.delete_if { |attr,v| attr =~ VERBOTEN_ATTRS }
+                    if node.attributes["href"] =~ /^javascript:/i
+                      node.attributes.delete "href"
+                    end
+                  end
+                  node.to_s
+                end
+              else
+                node.to_s.gsub(/</, "&lt;")
+            end
+          end
+
+          html = new_text
+        end
+
+        html
+      end
+
       
       private
         # Returns a version of the text that's safe to use in a regular expression without triggering engine features.