This middleware guards from DNS rebinding attacks by explicitly permitting the hosts a request can be sent to.

When a request comes to an unauthorized host, the response_app application will be executed and rendered. If no response_app is given, a default one will run, which responds with +403 Forbidden+.

Methods
C
N
Constants
ALLOWED_HOSTS_IN_DEVELOPMENT = [".localhost", IPAddr.new("0.0.0.0/0"), IPAddr.new("::/0")]
 
DEFAULT_RESPONSE_APP = -> env do request = Request.new(env) format = request.xhr? ? "text/plain" : "text/html" template = DebugView.new(host: request.host) body = template.render(template: "rescues/blocked_host", layout: "rescues/layout") [403, { "Content-Type" => "#{format}; charset=#{Response.default_charset}", "Content-Length" => body.bytesize.to_s, }, [body]] end
 
Class Public methods
new(app, hosts, response_app = nil)

Source: show | on GitHub 

# File actionpack/lib/action_dispatch/middleware/host_authorization.rb, line 90
def initialize(app, hosts, response_app = nil)
  @app = app
  @permissions = Permissions.new(hosts)
  @response_app = response_app || DEFAULT_RESPONSE_APP
end
Instance Public methods
call(env)

Source: show | on GitHub 

# File actionpack/lib/action_dispatch/middleware/host_authorization.rb, line 96
def call(env)
  return @app.call(env) if @permissions.empty?

  request = Request.new(env)

  if authorized?(request)
    mark_as_authorized(request)
    @app.call(env)
  else
    @response_app.call(env)
  end
end