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

3 files changed, 81 insertions, 0 deletions

diff --git a/actionpack/CHANGELOG b/actionpack/CHANGELOG
index 0751b162df..8c20ac3606 100644
--- a/actionpack/CHANGELOG
+++ b/actionpack/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* 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]
+
 * Fixed the HTML scanner used by assert_tag where a infinite loop could be caused by a stray less-than sign in the input #1270 [Jamis Buck]
 
 * Added functionality to assert_tag, so you can now do tests on the siblings of a node, to assert that some element comes before or after the element in question, or just to assert that some element exists as a sibling #1226 [Jamis Buck]
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.
diff --git a/actionpack/test/template/text_helper_test.rb b/actionpack/test/template/text_helper_test.rb
index ed2f08e755..926ebdaf47 100644
--- a/actionpack/test/template/text_helper_test.rb
+++ b/actionpack/test/template/text_helper_test.rb
@@ -86,5 +86,29 @@ class TextHelperTest < Test::Unit::TestCase
     assert_equal %(<p>Link #{link2_result}</p>), auto_link("<p>Link #{link2_raw}</p>")
     assert_equal %(<p>#{link2_result} Link</p>), auto_link("<p>#{link2_raw} Link</p>")
   end
+
+  def test_sanitize_form
+    raw = "<form action=\"/foo/bar\" method=\"post\"><input></form>"
+    result = sanitize(raw)
+    assert_equal "&lt;form action='/foo/bar' method='post'><input>&lt;/form>", result
+  end
+
+  def test_sanitize_script
+    raw = "<script language=\"Javascript\">blah blah blah</script>"
+    result = sanitize(raw)
+    assert_equal "&lt;script language='Javascript'>blah blah blah&lt;/script>", result
+  end
+
+  def test_sanitize_js_handlers
+    raw = %{onthis="do that" <a href="#" onclick="hello" name="foo" onbogus="remove me">hello</a>}
+    result = sanitize(raw)
+    assert_equal %{onthis="do that" <a name='foo' href='#'>hello</a>}, result
+  end
+
+  def test_sanitize_javascript_href
+    raw = %{href="javascript:bang" <a href="javascript:bang" name="hello">foo</a>, <span href="javascript:bang">bar</span>}
+    result = sanitize(raw)
+    assert_equal %{href="javascript:bang" <a name='hello'>foo</a>, <span>bar</span>}, result
+  end
   
 end