Fix SVG whitelisting to allow namespaced attributes

lib/gitlab/sanitizers/svg.rb

@@ -13,12 +13,11 @@ module Gitlab
           unless Whitelist::ALLOWED_ELEMENTS.include?(node.name)
             node.unlink
           else
-            node.attributes.each do |attr_name, attr|
             valid_attributes = Whitelist::ALLOWED_ATTRIBUTES[node.name]
 
-              unless valid_attributes && valid_attributes.include?(attr_name)
-                if Whitelist::ALLOWED_DATA_ATTRIBUTES_IN_ELEMENTS.include?(node.name) &&
-                    attr_name.start_with?('data-')
+            node.attribute_nodes.each do |attr|
+              unless valid_attributes && valid_attributes.include?(attribute_name_with_namespace(attr))
+                if Whitelist::ALLOWED_DATA_ATTRIBUTES_IN_ELEMENTS.include?(node.name) && data_attribute?(attr)
                   # Arbitrary data attributes are allowed. Verify that the attribute
                   # is a valid data attribute.
                   attr.unlink unless attr_name =~ DATA_ATTR_PATTERN
@@ -29,6 +28,20 @@ module Gitlab
             end
           end
         end
+
+        def attribute_name_with_namespace(attr)
+          if attr.namespace
+            "#{attr.namespace.prefix}:#{attr.name}"
+          else
+            attr.name
+          end
+        end
+
+        private
+
+        def data_attribute?(attr)
+          attr.name.start_with?('data-')
+        end
       end
     end
   end

spec/lib/gitlab/sanitizers/svg_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Sanitizers::SVG do
+  let(:scrubber) { Gitlab::Sanitizers::SVG::Scrubber.new }
+  let(:namespace) { double(Nokogiri::XML::Namespace, prefix: 'xlink') }
+  let(:namespaced_attr) { double(Nokogiri::XML::Attr, name: 'href', namespace: namespace) }
+
+  context 'scrubber' do
+    describe '#scrub' do
+      let(:invalid_element) { double(Nokogiri::XML::Node, name: 'invalid') }
+      let(:invalid_attribute) { double(Nokogiri::XML::Attr, name: 'invalid', namespace: nil) }
+      let(:valid_element) { double(Nokogiri::XML::Node, name: 'use') }
+
+      it 'removes an invalid element' do
+        expect(invalid_element).to receive(:unlink)
+
+        scrubber.scrub(invalid_element)
+      end
+
+      it 'removes an invalid attribute' do
+        allow(valid_element).to receive(:attribute_nodes) { [invalid_attribute] }
+        expect(invalid_attribute).to receive(:unlink)
+
+        scrubber.scrub(valid_element)
+      end
+
+      it 'accepts valid element' do
+        allow(valid_element).to receive(:attribute_nodes) { [namespaced_attr] }
+        expect(valid_element).not_to receive(:unlink)
+
+        scrubber.scrub(valid_element)
+      end
+
+      it 'accepts valid namespaced attributes' do
+        allow(valid_element).to receive(:attribute_nodes) { [namespaced_attr] }
+        expect(namespaced_attr).not_to receive(:unlink)
+
+        scrubber.scrub(valid_element)
+      end
+    end
+
+    describe '#attribute_name_with_namespace' do
+      it 'returns name with prefix when attribute is namespaced' do
+        expect(scrubber.attribute_name_with_namespace(namespaced_attr)).to eq('xlink:href')
+      end
+    end
+  end
+end