I want to use cancan to allow updating a certain attribute of a model but not others. Here is what my update action looks like.
class UsersController < ApplicationController
load_and_authorize_resource
def update
respond_with User.update(params[:id], params[:user])
end
end
if resource.instance_of? Teacher
can [:read, :update], User do |user|
resource.users.include? user
end
I want Teacher to be able to modify user.course_id but nothing else. How should I change
can :update, User
to do what I want to.
Hm.. I"m not sure if the 'action' in a cancan ability has to explicitly be an action in the controller. If it doesn't, you could do...
# ability.rb
if resource.instance_of? Teacher
can :update_course, User
end
# Controller
def update
params[:user].delete(:course_id) if cannot? :update_course, User
respond_with User.update(params[:id], params[:user])
end
Related
I'm new to rails and for the life of me I don't "get" cancan.
I've read this tutorial but can't figure out how to apply instructions to my situation.
In the cancan wiki there is:
an AdminController
a roll_logs action
In the ability class is says:
can :roll, :logs if user.admin?
I don't get what the :roll and :logs symbols have to do with the controller and the action?
All I want to do is say, if a user is an admin, give them access to the AdminController actions, otherwise don't, is this possible?
Yes this is possible.
The statement
can :roll, :logs if user.admmin?
means that when calling authorize! :roll, :logs an unauthorized exception gets thrown if the user isn't an admin.
So it doesn't have anything to do with a controller or an action, untill you make it so.
If you have a logs_controller for example with an action roll you could do something like this.
class LogsController < ApplicationController
def roll
authorize! :roll, :logs
# Rest of the roll functionality.
end
So in your example, you want to give users who are admin permission to access all admin controller actions.
You can achieve this like this.
ability.rb
class Ability
include CanCan::Ability
def initialize(user)
can(:manage, :admin) if user.admin?
end
end
admin_controller.rb
class AdminController < ApplicationController
authorize_resource :class => false
def foo
end
def bar
end
end
This will make sure that only admins can access the foo and bar actions of the admin_controller.
The :class => false statement means that you are not authorizing a resource, which is what we want since you are not for example authorizing a certain post or comment. You are just authorizing actions on a controller.
I want to show a devise user provide inside another view.
Homeprivate/profile.html.erb:
<%= render "devise/registrations/edit" %>
I just converted the default edit view into a partial. To support the user to be available as a "resource", I have the following helper.
module HomeprivateHelper
def resource_name
:user
end
def resource
#resource ||= User.new
end
def devise_mapping
#devise_mapping ||= Devise.mappings[:user]
end
end
But if I sign in, and go to /homeprivate/profile -- I see all fields are empty. Somehow the current user is not mapped to the form. How do I map the current user to the profile view if it is displayed in a custom view? Seems like User.new is used, not the current user.
I'm fairly new to rails, but I got the same issue and figured out how to fill those empty fields. In your helper, instead of user.new use current_user. It should look like this:
def resource
#resource ||= current_user
end
That should work.
tl;dr
I use CanCan for authorization in a single-author blog. I want non-admin users to not be able to view unpublished posts. The following does not do the trick:
can :read, Post do |post|
post.published_at && post.published_at <= Time.zone.now
end
Why doesn't it work, and what can I do to make it work?
Thanks. ;-)
The long version
Hello World,
I have a single-user blogging application and use CanCan for authorization purposes. I want administrators (user.admin? # => true) to be able to do whatever they wish with everything (they are administrators after all…). I also want regular users (both those who are logged in, but does not have the admin role, and those who are not logged in) to be able to view blog posts that have been published. I do not want them to see those that are not published.
Blog posts (of the model Post) each have an attribute called published_at (which is a DateTime and nil by default). Needless to say: when published_at is nil, the post is not published, otherwise it is published at the set date and time.
I have the following in my Ability class:
class Ability
include CanCan::Ability
def initialize user
user ||= User.new # guest user (not logged in)
if user.admin?
can :manage, :all
else
can :read, Post do |post|
post.published_at && post.published_at <= Time.zone.now
end
end
end
end
However, this does not seem to work as I intend it to. I have read on the CanCan wiki that this might not always work. However, I believe it should work in my case here, as I do have an instance of the Post model called #post in my PostsController#show action:
class PostsController < ApplicationController
authorize_resource
respond_to :html, :json
# other actions omitted ...
def show
#post = Post.find params[:id]
respond_with #post
end
# other actions omitted ...
end
Even with this code I am able to visit the blog post through the show action and view. I have also tried removing the authorize_resource call from the PostsController, realizing it might override some abilities or something, but it didn't help.
I have figured out a temporary solution, although I find it ugly and really want to utilize the CanCan abilities. My ugly temporary solution checks internally in the PostsController#show if the user has access to view the resource:
def show
#post = Post.find params[:id]
unless #post.published_at
raise CanCan::AccessDenied unless current_user && current_user.admin?
end
respond_with #post
end
As I said, this works. But I don't really want to go with this solution, as I believe there's a better way of doing this as a CanCan ability.
I'd much appreciate an explanation of why my approach does not work as well as a good solution to the problem. Thanks in advance. :-)
At the point where authorize_resource is being called (before_filter) you don't have a post object to authorize.
Assuming CanCan 1.6 or later, try this..
In your Post model
class Post < ActiveRecord::Base
scope :published, lambda { where('published_at IS NOT NULL AND published_at <= ?', Time.zone.now) }
# the rest of your model code
end
In your Ability model
class Ability
include CanCan::Ability
def initialize user
user ||= User.new # guest user (not logged in)
if user.admin?
can :manage, :all
else
can :read, Post, Post.published do |post|
post.published_at && post.published_at <= Time.zone.now
end
end
end
end
In your controller
class PostsController < ApplicationController
load_and_authorize_resource
respond_to :html, :json
# other actions omitted ...
def show
respond_with #post
end
end
I'm using Devise for the first time with rails, and I'm having trouble with one thing:
I used the provided authenticate_user! method in my user's controller to restrict access to pages like so:
before_filter :authenticate_user!, :only => [:edit, :show, :update, :create, :destroy]
But this allows any signed in user to access any other users :edit action, which I want to restrict to only that user. How would I do that?
In your edit method, you need to do a check to see if the user owns the record:
def edit
#record = Record.find(params[:id])
if #record.user == current_user
#record.update_attributes(params[:record])
else
redirect_to root_path
end
end
You should look into Authorization such as CanCan. Or alternatively create a new method like so:
# Create an admin boolean column for your user table.
def authenticate_admin!
authenticate_user! and current_user.admin?
end
I have a model (say Car) in which a method needs access to the current_user to determine if the user is allowed to perform the things that the method does.
For example, a method might want to do these things:
Check that current_user owns this object
Check that the object status == 1 (Active)
Check that a related object exists and it's X field is not NULL
I need this business logic to be in the model, not in the controller, so that it's the one place where my business logic will be. The method might get called from places other than a controller.
I know that there are gems like cancan, declarative_authorization etc. but they seem to be overkill for what I need to do. And also, accessing current_user in a model is not considered the "right way".
Then, how do I make that check in the model but still feel "clean"?
I have experienced a situation where "current_user" needs be tightly connected to a model, but I handled it all in the Controller and it works pretty well. Here are some examples:
My model is "Photos". Photos are owned by users, and how people interact with photos is obviously tightly related to whether or not they own the photo.
In the show action I need to load either the existing rating a user has given to a photo (so they can edit it) or allow them to create a new one:
def show
#photo = Photo.find(params[:id])
if user_signed_in?
if #rating = current_user.ratings.find_by_photo_id(params[:id])
#rating
#current_user_rating = #rating.value
else
#rating = current_user.ratings.new
#current_user_rating = "n/a"
end
end
end
When people create photos I want them to be automatically assigned to the current user.
def new
#photo = Photo.new
end
def create
#photo = current_user.photos.create(params[:photo])
if #photo.save
redirect_to user_path(current_user), :notice => t('photo.notice.created')
else
render 'new'
end
end
Only the owners of a photo can change them:
def edit
#photo = Photo.find(params[:id])
if #photo.user == current_user
render 'edit'
else
redirect_to user_path(current_user), :alert => t('application.error.unauthorized')
end
end
def update
#photo = current_user.photos.find_by_id(params[:id])
#photo.update_attributes(params[:photo])
if #photo.save
redirect_to user_path(current_user), :notice => t('photo.notice.updated')
else
render 'edit'
end
end
This approach is based on the constraints that a "current_user" object is tied to the session, which only the controller knows about. So, in short, I have yet to find a good way to integrate "current_user" into a model, but I've been able to find (I think) pretty clean ways to tie the model and controller together so that this can be provided by the controller.
One fairly simple solution to most problems, if your controller is starting to get messy, would be to take a chunk of logic and define as a method in the model, but require one argument = a user object. Then you can just feed "current_user" to that method from your controller and the model handles the rest.
Good luck! Also, if anyone else has any better ideas for this, I'd love to hear them!
Handle auth'ing in a Controller.
Example: Putting auth logic in parent ApplicationController.
class ApplicationController < ActionController::Base
protect_from_forgery
protected
# Returns the currently logged in user or nil if there isn't one
def current_user
return unless session[:user_id]
#current_user ||= User.find_by_id(session[:user_id])
end
# Make current_user available in templates as a helper
helper_method :current_user
# Filter method to enforce a login requirement
# Apply as a before_filter on any controller you want to protect
def authenticate
logged_in? ? true : access_denied
end
# Predicate method to test for a logged in user
def logged_in?
current_user.is_a? User
end
# Make logged_in? available in templates as a helper
helper_method :logged_in?
def access_denied
redirect_to login_path, :notice => "Please log in to continue" and return false
end
end
Now that current_user is an accessor to the logged in user and you can access it in any controller, you can do your authorization logic in the appropriate controller before you do anything with the model.
Your right, though. Models don't care about authorization or who is accessing them.