1 files changed, 62 insertions, 0 deletions
diff --git a/lib/banzai/filter/asset_proxy_filter.rb b/lib/banzai/filter/asset_proxy_filter.rb
new file mode 100644
index 00000000000..0a9a52a73a1
--- /dev/null
+++ b/lib/banzai/filter/asset_proxy_filter.rb
@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+module Banzai
+  module Filter
+    # Proxy's images/assets to another server.  Reduces mixed content warnings
+    # as well as hiding the customer's IP address when requesting images.
+    # Copies the original img `src` to `data-canonical-src` then replaces the
+    # `src` with a new url to the proxy server.
+    class AssetProxyFilter < HTML::Pipeline::CamoFilter
+      def initialize(text, context = nil, result = nil)
+        super
+      end
+
+      def validate
+        needs(:asset_proxy, :asset_proxy_secret_key) if asset_proxy_enabled?
+      end
+
+      def asset_host_whitelisted?(host)
+        context[:asset_proxy_domain_regexp] ? context[:asset_proxy_domain_regexp].match?(host) : false
+      end
+
+      def self.transform_context(context)
+        context[:disable_asset_proxy] = !Gitlab.config.asset_proxy.enabled
+
+        unless context[:disable_asset_proxy]
+          context[:asset_proxy_enabled]       = !context[:disable_asset_proxy]
+          context[:asset_proxy]               = Gitlab.config.asset_proxy.url
+          context[:asset_proxy_secret_key]    = Gitlab.config.asset_proxy.secret_key
+          context[:asset_proxy_domain_regexp] = Gitlab.config.asset_proxy.domain_regexp
+        end
+
+        context
+      end
+
+      # called during an initializer. Caching the values in Gitlab.config significantly increased
+      # performance, rather than querying Gitlab::CurrentSettings.current_application_settings
+      # over and over.  However, this does mean that the Rails servers need to get restarted
+      # whenever the application settings are changed
+      def self.initialize_settings
+        application_settings           = Gitlab::CurrentSettings.current_application_settings
+        Gitlab.config['asset_proxy'] ||= Settingslogic.new({})
+
+        if application_settings.respond_to?(:asset_proxy_enabled)
+          Gitlab.config.asset_proxy['enabled']       = application_settings.asset_proxy_enabled
+          Gitlab.config.asset_proxy['url']           = application_settings.asset_proxy_url
+          Gitlab.config.asset_proxy['secret_key']    = application_settings.asset_proxy_secret_key
+          Gitlab.config.asset_proxy['whitelist']     = application_settings.asset_proxy_whitelist || [Gitlab.config.gitlab.host]
+          Gitlab.config.asset_proxy['domain_regexp'] = compile_whitelist(Gitlab.config.asset_proxy.whitelist)
+        else
+          Gitlab.config.asset_proxy['enabled']       = ::ApplicationSetting.defaults[:asset_proxy_enabled]
+        end
+      end
+
+      def self.compile_whitelist(domain_list)
+        return if domain_list.empty?
+
+        escaped = domain_list.map { |domain| Regexp.escape(domain).gsub('\*', '.*?') }
+        Regexp.new("^(#{escaped.join('|')})$", Regexp::IGNORECASE)
+      end
+    end
+  end
+end