# Simple authorization module with Rails

I created a simple Authorization module with Rails. I found that there are other authorization systems, such as CanCanCan, but they grant permissions at Model level and, for this particular website I am developing, it is more convenient to authorize at Controller level.

The idea is simple: the permissions are stored in a YAML file in the config directory and a function checks if the combination of admin_role, controller and action exist in the config file. There is also a wildcard :all.

# app/controllers/admins/base_controller.rb
class Admins::BaseController < ApplicationController

include Admins::AuthorizationHelper

before_action :authorize_admin

...

end

# app/helpers/admin/authorization_helper.rb
module Admins::AuthorizationHelper

private

def authorize_admin
unless is_authorized? params[:controller], params[:action]
refuse_access_to_admin_site
end
end

def is_authorized?(controller, action)
permissions = Rails.application.config_for :admin_auth
authority = current_admin.authority

if permissions[authority].nil?
false
elsif permissions[authority] == ['all']
true
elsif permissions[authority][controller].nil?
false
elsif permissions[authority][controller] == ['all']
true
elsif permissions[authority][controller].include? action
true
else
false
end
end

def refuse_access_to_admin_site
flash[:error] = 'Permission denied'

if request.referer.present?
redirect_to :back
else
redirect_to admins_products_path
end
end

end

# config/admin_auth.yml
defaults: &defaults
super_admins:
- all
admins:
admins/shops:
- index
- show_used_history
admins/products:
- index
admins/prescriptions:
- all
admins/products:
- index
operators:
admins/products:
- index
admins/prescriptions:
- all
admins/shipments:
- index
- show
test:
<<: *defaults
development:
<<: *defaults
staging:
<<: *defaults
production:
<<: *defaults

• I don't know much about rails, what's the point of this? if permissions[authority].nil?;false. Why not just deny permission if they no permission? Dec 13, 2015 at 18:07
• I was trying to avoid getting and exception while checking for permissions[authority][controller] if authority was nil. But this is because I still didn't know the method fetch( , []) for arrays. ;) Dec 14, 2015 at 1:11
• Awh I didn't know that either, makes sense. Dec 14, 2015 at 1:40

## 1 Answer

There's a lot of repeated code in that long if..else. Here's an idea (code not tested) for shortening it up:

def is_authorized?(controller, action)
permissions = Rails.application.config_for :admin_auth
authority = current_admin.authority

global_auth = permissions.fetch(authority, [])
return true if global_auth.include? 'all'

# Note the implicit assumption in this code, and the original code,
# that global_auth is a Hash if we have not already returned

ctrl_auth = global_auth.fetch(controller, [])
ctrl_auth.include? 'all' || ctrl_auth.include? action
end


Please see the inline comment for an assumption your making about the config data.

At a higher level, the deeper reason this code has to be overly complicated and do nil checks and checks for different kinds of data (array or hash) is because the config data structure has no regularity.

The real fix here is probably to wrap that returned data structure in an object that regularizes it, essentially using something similar to the NullObject pattern. So that your code could then read like this:

permissions = Rails.application.config_for :admin_auth
permissions = ConfiguredPermissions.new permissions

permissions.global_access? || permissions.for?(controller, action)


You can also avoid the if..else in your redirect method:

  def refuse_access_to_admin_site
flash[:error] = 'Permission denied'

location = request.referer.present? ? :back : admins_products_path
redirect_to location
end

• Thanks for the corrections! I really didn't like the long if...else, and your solution is quite more elegant (even if I had to check global_auth for nil). I've been checking for the NullObject pattern and I don't know if it would make things more complex. At the end, would be to create a new class in order to get rid of 5 lines of code, isn't it? Dec 15, 2015 at 14:08
• Indeed, it would probably be overkill in this situation. I just wanted to point it out to give deeper insight into what is going on. and if you added more security levels or other logic into the authorization, it might make sense at that point Dec 15, 2015 at 15:05