1 files changed, 57 insertions, 0 deletions
diff --git a/lib/gitlab/sanitizers/svg.rb b/lib/gitlab/sanitizers/svg.rb
new file mode 100644
index 00000000000..8304b9a482c
--- /dev/null
+++ b/lib/gitlab/sanitizers/svg.rb
@@ -0,0 +1,57 @@
+module Gitlab
+  module Sanitizers
+    module SVG
+      def self.clean(data)
+        Loofah.xml_document(data).scrub!(Scrubber.new).to_s
+      end
+
+      class Scrubber < Loofah::Scrubber
+        # http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#embedding-custom-non-visible-data-with-the-data-*-attributes
+        DATA_ATTR_PATTERN = /\Adata-(?!xml)[a-z_][\w.\u00E0-\u00F6\u00F8-\u017F\u01DD-\u02AF-]*\z/u
+
+        def scrub(node)
+          unless Whitelist::ALLOWED_ELEMENTS.include?(node.name)
+            node.unlink
+            return
+          end
+
+          valid_attributes = Whitelist::ALLOWED_ATTRIBUTES[node.name]
+          return unless valid_attributes
+
+          node.attribute_nodes.each do |attr|
+            attr_name = attribute_name_with_namespace(attr)
+
+            if valid_attributes.include?(attr_name)
+              attr.unlink if unsafe_href?(attr)
+            else
+              # Arbitrary data attributes are allowed.
+              unless allows_data_attribute?(node) && data_attribute?(attr)
+                attr.unlink
+              end
+            end
+          end
+        end
+
+        def attribute_name_with_namespace(attr)
+          if attr.namespace
+            "#{attr.namespace.prefix}:#{attr.name}"
+          else
+            attr.name
+          end
+        end
+
+        def allows_data_attribute?(node)
+          Whitelist::ALLOWED_DATA_ATTRIBUTES_IN_ELEMENTS.include?(node.name)
+        end
+
+        def unsafe_href?(attr)
+          attribute_name_with_namespace(attr) == 'xlink:href' && !attr.value.start_with?('#')
+        end
+
+        def data_attribute?(attr)
+          attr.name.start_with?('data-') && attr.name =~ DATA_ATTR_PATTERN && attr.namespace.nil?
+        end
+      end
+    end
+  end
+end