I have a form on another website (using a different backend) that I want to be able to POST to my Rails application (on a different domain).
You can't generate an autenticity token from outside your Rails app. What you can do, is to disable the token protection only for this action and use a custom implementation based on a before_filter.
skip_before_filter :verify_authenticity_token, :only => :my_action
before_filter :verify_custom_authenticity_token, :only => :my_action
def verify_custom_authenticity_token
# checks whether the request comes from a trusted source
end
You could just remove the check by adding a filter like:
skip_before_filter :verify_authenticity_token, :only => :action_name