Rails 4 Strong Parameters opposite permit all attributes

Question

I am using rails 4 with strong parameters and trying to figure out how to set the strong parameters to not allow any attribute with the parameter.

I read this Rails 4 Strong parameters : permit all attributes? And would like to do the opposite of that.

params.require(:user).permit!

would permit all attributes, how could I do the opposite?

UPDATE THIS IS MY FULL CODE:

in app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception
  before_filter :configure_permitted_parameters, if: :devise_controller?

  protected

  def configure_permitted_parameters
      devise_parameter_sanitizer.for(:sign_up) { |u| u.permit(:username, :email, :password, :password_confirmation, :remember_me) }
      devise_parameter_sanitizer.for(:sign_in) { |u| u.permit(:signin, :password, :remember_me) }
      devise_parameter_sanitizer.for(:account_update) {|u| u.permit(:username, :email, :password, :password_confirmation, :current_password)}
      devise_parameter_sanitizer.for(:sign_in) { |a| a.permit(:signin, :password, :remember_me) }
      devise_parameter_sanitizer.for(:account_update) {|a| a.permit(:username, :email, :password, :password_confirmation, :current_password)}
  end
end

in app/models/admin.rb

    class Admin < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable, :registerable
  devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable

  attr_accessor :signin

  def self.find_first_by_auth_conditions(warden_conditions)
      conditions = warden_conditions.dup
      if login = conditions.delete(:signin)
        where(conditions).where(["username = :value OR lower(email) = lower(:value)", { :value => login }]).first
      else
        where(conditions).first
      end
    end

  validates :username, presence: true, length: {maximum: 255}, uniqueness: { case_sensitive: false }, format: { with: /\A[a-zA-Z0-9]*\z/, message: "may only contain letters and numbers." }
end

The users.rb model is the same as the admin.rb model. This leads to two different sign up/sign in links- 1 for each model. Also I need to leave the :registerable module so that I can override the default devise's registerable module. However I modified the views to not show the admin page when typed in a browser. --- I only need to block it via command line now.

I also have posted a previous question similar to this:

Rails 4 Devise Strong Parameters Admin Model

Answer 1

If you're not using any user-inputted parameters (like for a GET), you don't need to use params at all. Your controller will just work, and there won't be a security issue.

Answer 2

The default behavior is the opposite of .permit. If you don't mention an attribute in your params arguments, it is like denying the user access to do anything with those attributes.