Add #before_upload hook

Author: rastating

lib/wpxf/wordpress/shell_upload.rb

@@ -46,10 +46,17 @@ def payload_body_builder
   def uploaded_payload_location
   end
 
+  # Called prior to preparing and uploading the payload.
+  # @return [Boolean] true if no errors occurred.
+  def before_upload
+    true
+  end
+
   # Run the module.
   # @return [Boolean] true if successful.
   def run
     return false unless super
+    return false unless before_upload
 
     emit_info 'Preparing payload...'
     @payload_name = "#{Utility::Text.rand_alpha(payload_name_length)}.php"