class Net::SSH::Authentication::Methods::KeyboardInteractive

def authenticate(next_service, username, password=nil)
  debug { "trying keyboard-interactive" }
  send_message(userauth_request(username, next_service, "keyboard-interactive", "", ""))
  loop do
    message = session.next_message
    case message.type
    when USERAUTH_SUCCESS
      debug { "keyboard-interactive succeeded" }
      return true
    when USERAUTH_FAILURE
      debug { "keyboard-interactive failed" }
      raise Net::SSH::Authentication::DisallowedMethod unless
        message[:authentications].split(/,/).include? 'keyboard-interactive'
      return false
    when USERAUTH_INFO_REQUEST
      name = message.read_string
      instruction = message.read_string
      debug { "keyboard-interactive info request" }
      unless password
        puts(name) unless name.empty?
        puts(instruction) unless instruction.empty?
      end
      lang_tag = message.read_string
      responses =[]
      message.read_long.times do
        text = message.read_string
        echo = message.read_bool
        responses << (password || prompt(text, echo))
      end
      # if the password failed the first time around, don't try
      # and use it on subsequent requests.
      password = nil
      msg = Buffer.from(:byte, USERAUTH_INFO_RESPONSE, :long, responses.length, :string, responses)
      send_message(msg)
    else
      raise Net::SSH::Exception, "unexpected reply in keyboard interactive: #{message.type} (#{message.inspect})"
    end
  end
end