1 files changed, 96 insertions, 0 deletions
diff --git a/lib/banzai/filter/inline_metrics_redactor_filter.rb b/lib/banzai/filter/inline_metrics_redactor_filter.rb
new file mode 100644
index 00000000000..4d8a5028898
--- /dev/null
+++ b/lib/banzai/filter/inline_metrics_redactor_filter.rb
@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # HTML filter that removes embeded elements that the current user does
+    # not have permission to view.
+    class InlineMetricsRedactorFilter < HTML::Pipeline::Filter
+      include Gitlab::Utils::StrongMemoize
+
+      METRICS_CSS_CLASS = '.js-render-metrics'
+
+      # Finds all embeds based on the css class the FE
+      # uses to identify the embedded content, removing
+      # only unnecessary nodes.
+      def call
+        nodes.each do |node|
+          path = paths_by_node[node]
+          user_has_access = user_access_by_path[path]
+
+          node.remove unless user_has_access
+        end
+
+        doc
+      end
+
+      private
+
+      def user
+        context[:current_user]
+      end
+
+      # Returns all nodes which the FE will identify as
+      # a metrics dashboard placeholder element
+      #
+      # @return [Nokogiri::XML::NodeSet]
+      def nodes
+        @nodes ||= doc.css(METRICS_CSS_CLASS)
+      end
+
+      # Maps a node to the full path of a project.
+      # Memoized so we only need to run the regex to get
+      # the project full path from the url once per node.
+      #
+      # @return [Hash<Nokogiri::XML::Node, String>]
+      def paths_by_node
+        strong_memoize(:paths_by_node) do
+          nodes.each_with_object({}) do |node, paths|
+            paths[node] = path_for_node(node)
+          end
+        end
+      end
+
+      # Gets a project's full_path from the dashboard url
+      # in the placeholder node. The FE will use the attr
+      # `data-dashboard-url`, so we want to check against that
+      # attribute directly in case a user has manually
+      # created a metrics element (rather than supporting
+      # an alternate attr in InlineMetricsFilter).
+      #
+      # @return [String]
+      def path_for_node(node)
+        url = node.attribute('data-dashboard-url').to_s
+
+        Gitlab::Metrics::Dashboard::Url.regex.match(url) do |m|
+          "#{$~[:namespace]}/#{$~[:project]}"
+        end
+      end
+
+      # Maps a project's full path to a Project object.
+      # Contains all of the Projects referenced in the
+      # metrics placeholder elements of the current document
+      #
+      # @return [Hash<String, Project>]
+      def projects_by_path
+        strong_memoize(:projects_by_path) do
+          Project.eager_load(:route, namespace: [:route])
+            .where_full_path_in(paths_by_node.values.uniq)
+            .index_by(&:full_path)
+        end
+      end
+
+      # Returns a mapping representing whether the current user
+      # has permission to view the metrics for the project.
+      # Determined in a batch
+      #
+      # @return [Hash<Project, Boolean>]
+      def user_access_by_path
+        strong_memoize(:user_access_by_path) do
+          projects_by_path.each_with_object({}) do |(path, project), access|
+            access[path] = Ability.allowed?(user, :read_environment, project)
+          end
+        end
+      end
+    end
+  end
+end