Thanks for the tip! I'll be attacking this again tonight, I think I have an idea now that you mention auth. By the way, some subdomains are public (not sure if part of the game), like source.0x0539.com, oxidized etc.
Awesome work, thanks for the fun!
Edit: Just got past login, what an awesome puzzle. That being said, I hate that it looks like I have a run an executable from your site. Seems dangerous, so now I have to spend the time getting a VM setup.