1 files changed, 33 insertions, 0 deletions
diff --git a/lib/gitlab/asset_proxy.rb b/lib/gitlab/asset_proxy.rb
new file mode 100644
index 00000000000..fd7c58ba68f
--- /dev/null
+++ b/lib/gitlab/asset_proxy.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+# This is based on https://github.com/jch/html-pipeline/blob/v2.12.2/lib/html/pipeline/camo_filter.rb
+# and Banzai::Filter::AssetProxyFilter which we use to proxy images in Markdown
+
+module Gitlab
+  module AssetProxy
+    class << self
+      def proxy_url(url)
+        return url unless Gitlab.config.asset_proxy.enabled
+        return url if asset_host_whitelisted?(url)
+
+        "#{Gitlab.config.asset_proxy.url}/#{asset_url_hash(url)}/#{hexencode(url)}"
+      end
+
+      private
+
+      def asset_host_whitelisted?(url)
+        parsed_url = URI.parse(url)
+
+        Gitlab.config.asset_proxy.domain_regexp&.match?(parsed_url.host)
+      end
+
+      def asset_url_hash(url)
+        OpenSSL::HMAC.hexdigest('sha1', Gitlab.config.asset_proxy.secret_key, url)
+      end
+
+      def hexencode(str)
+        str.unpack1('H*')
+      end
+    end
+  end
+end