Use CanCan Authorization along with Custom Authentication in Rails 3 - ruby

Question

I am new to Rails and have been developing an app in rails 3 after following a Lynda.com tutorial where Kevin Skoglund showed us a way to authenticate a user using SHA1 Digest. I used that in my app and there is a need now to put in some Authorization. When I searched around, I found CanCan to be one of the better ones for authorization in rails. However, CanCan seems to be mostly implemented using Devise or Authlogic authentication and not custom authentication.
I wanted to know if it is at all possible to use CanCan if we use custom authentication, like I did. Is so, how to go about getting CanCan to work ?
It looks like CanCan needs some 'create_user' to be present but I am not sure how/where to create it.
Another alternative that I thought would be to put in my custom check on every page to check the user role and redirect them to an error page if they are unauthorized but that seems like a bad way to approach this problem...Your views on this please.
Please let me know if you need any additional information. I am using Ruby 1.9.3 and Rails 3.2.1.
Below is the way I have my current authentication set up. Any help would be greatly appreciated.
access_controller.rb
class AccessController < ApplicationController
before_filter :confirm_logged_in, :except => [:login, :attempt_login, :logout]
def attempt_login
authorized_user = User.authenticate(params[:username], params[:password])
if authorized_user
session[:user_id] = authorized_user.id
flash[:notice] = "You are logged in"
redirect_to(:controller => 'orders', :action => 'list')
else
flash[:notice] = "Invalid Username/password combination"
redirect_to(:action => 'login')
end
end
def logout
session[:user_id] = nil
flash[:notice] = "You have been logged out"
redirect_to(:action => 'login')
end
end
user.rb (User Model)
require 'digest/sha1'
class User < ActiveRecord::Base
has_one :profile
has_many :user_roles
has_many :roles, :through => :user_roles
attr_accessor :password
attr_protected :hashed_password, :salt
def self.authenticate(username="", password="")
user = User.find_by_username(username)
if user && user.password_match(password)
return user
else
return false
end
end
def password_match(password="")
hashed_password == User.hash_with_salt(password, salt)
end
validates_length_of :password, :within => 4..25, :on => :create
before_save :create_hashed_password
after_save :clear_password
def self.make_salt(username="")
Digest::SHA1.hexdigest("Use #{username} with #{Time.now} to make salt")
end
def self.hash_with_salt(password="", salt="")
Digest::SHA1.hexdigest("Put #{salt} on the #{password}" )
end
private
def create_hashed_password
unless password.blank?
self.salt = User.make_salt(username) if salt.blank?
self.hashed_password = User.hash_with_salt(password, salt)
end
end
def clear_password
self.password = nil
end
end
ApplicationController.rb
class ApplicationController < ActionController::Base
protect_from_forgery
private
def confirm_logged_in
unless session[:user_id]
flash[:notice] = "Please Log In"
redirect_to(:controller => 'access', :action => 'login')
return false
else
return true
end
end
end

Answer 1

I recommend first reading or watching the Railscast about CanCan. It is produced by the author of this gem and therefore very informative:
http://railscasts.com/episodes/192-authorization-with-cancan
You can also get help on the Github page:
https://github.com/ryanb/cancan
Somehow, you need to fetch the currently logged in user. This is what the current_user method does, and it needs to be defined on the users controller. Try something like this:
class UsersController < ApplicationController
# your other actions here
def current_user
User.find(session[:user_id])
end
end
Then, you should be able to use CanCan as described in the resources above.