Log missing l param for WKD requests, return 400

app/controllers/web_key_directory_controller.rb

@@ -3,8 +3,15 @@ class WebKeyDirectoryController < WellKnownController
 
   # /.well-known/openpgpkey/hu/:hashed_username(.txt)?l=username
   def show
-    username = params[:l] || ""
-    @user = User.find_by(cn: username.downcase)
+    if params[:l].blank?
+      # TODO store hashed username in db if existing implementations trigger
+      # this a lot
+      msg = "WKD request with \"l\" param omitted for hu: #{params[:hashed_username]})"
+      Sentry.capture_message(msg) if Setting.sentry_enabled?
+      http_status :bad_request and return
+    end
+
+    @user = User.find_by(cn: params[:l].downcase)
 
     if @user.nil? ||
        @user.pgp_pubkey.blank? ||