Dynamic cookie domain (for multitenant app)

Rails
1

There is a Multitenant App, that should serve sites on domains like
this:
client1.app.com
client2.app.com
And it’s easy to share cookies between all of them (using ‘.app.com’
cookie domain):
ActionController::Base.session = {:key => thekey, :secret =>
thesecret, :domain => ‘.app.com’}

But! There is one more requirement, those sites should be also avaliable
as:
www.client1.com

So, in order to all this works the App should dynamically change the
cookie domain:
xxx.app.com => “.app.com”
www.xxx.com => “.xxx.com” or leave it blank

Google told me that there is one approach
http://codetunes.com/2009/04/17/dynamic-cookie-domains-with-racks-middleware/
but it doesn’t works (Rails 2.3.5).

I also tried my own solution:

class CrossDomainCookies
def initialize(app)
@app = app
end

def call(env)
  host = env["HTTP_HOST"].split(':').first.downcase
  if host.include?('.')
    normalized_host = host.scan(/[^\.]+\.[^\.]+$/).first
    cookie_domain = ".#{normalized_host}"
  else
    normalized_host = host
    cookie_domain = host
  end

  Rails.logger.info cookie_domain

  ActionController::Base.session_options['domain'] = cookie_domain

  @app.call(env)
end

end

But it also doesn’t works, maybe there are some other solutions?