I have been recently reading through the pundit gem's README and noticed that they never authorize the index view within a controller. (Instead they use scope).
They give good reasoning for this, as an index page generally contains a list of elements, by controlling the list that is generated you effectively control the data on the page. However, occasionally it may be desired to block access to even the index page itself. (Rather than allowing access to a blank index page.) My question is what would be the proper way to perform this?
I have so far come up with several possibilities, and have the following classes:
A model MyModel
A controller MyModelsController
A policy MyModelPolicy
In my index method of my controller, the recommended method to solve this would be as follows:
def index
#my_models = policy_Scope(MyModel)
end
This will then allow access to the index page, but will filter the results to only what that use can see. (E.G. no results for no access.)
However to block access to the index page itself I have arrived at two different possibilities:
def index
#my_models = policy_Scope(MyModel)
authorize #my_models
end
or
def index
#my_models = policy_Scope(MyModel)
authorize MyModel
end
Which of these would be the correct path, or is there a different alternative that would be preferred?
class MyModelPolicy < ApplicationPolicy
class Scope < Scope
def resolve
if user.admin?
scope.all
else
raise Pundit::NotAuthorizedError, 'not allowed to view this action'
end
end
end
end
Policy,
class MyModelPolicy < ApplicationPolicy
class Scope < Scope
def resolve
if user.admin?
scope.all
else
scope.where(user: user)
end
end
end
def index?
user.admin?
end
end
Controller,
def index
#my_models = policy_scope(MyModel)
authorize MyModel
end
Related
I am perhaps misunderstanding Pundit policies but I am facing an issue where the UserPolicy is clashing with the SongPolicy.
What happens if that a statement in UserPolicy is being asserted ignoring what's written in SongPolicy:
Pundit::NotAuthorizedError in SongsController#edit
not allowed to edit? this User
def authorization
authorize Current.user
end
The issue emerged after introducing a new role for users but I believe that I probably haven't configured it right and for some reason only UserPolicy is looked at for asserting authorization in the SongsController?
I have two controllers that check for the user to be signed in (require_user_logged_in) and another to check on Pundit's policies (authorization):
class UsersController < ApplicationController
before_action :require_user_logged_in!, :authorization, :turbo_frame_check
# Actions were removed for brevity.
end
class SongsController < ApplicationController
before_action :require_user_logged_in!, :authorization, except: [:index, :show]
# Actions were removed for brevity.
end
The authorization methods looks like this:
def authorization
authorize Current.user
end
There's an application-level policy class, ApplicationPolicy:
# frozen_string_literal: true
class ApplicationPolicy
attr_reader :user, :params, :record
# Allows params to be part of policies.
def initialize(context, record)
if context.is_a?(Hash)
#user = context[:user]
#params = context[:params]
else
#user = context
#params = {}
end
#record = record
end
def index?
false
end
def show?
false
end
def create?
false
end
def new?
create?
end
def update?
false
end
def edit?
update?
end
def destroy?
false
end
class Scope
def initialize(user, scope)
#user = user
#scope = scope
end
def resolve
raise NotImplementedError, "You must define #resolve in #{self.class}"
end
private
attr_reader :user, :scope
end
end
The UserPolicy to protect user views:
class UserPolicy < ApplicationPolicy
class Scope < Scope
end
def index?
user.has_role?(:admin)
end
def show?
# Access if admin or the same user only.
user.has_role?(:admin) || is_same_user?
end
def create?
index?
end
def new?
create?
end
def update?
index? || is_same_user?
end
def edit?
update? # This is called when accessing a view for `SongsController`.
end
def destroy?
index? || is_same_user?
end
def delete?
destroy?
end
private
# Used to keep a user from editing another.
# Admins should be allowed to edit all users.
def is_same_user?
# Check if user being accessed is the one being logged in.
params[:id].to_s == Current.user.username.to_s
end
end
And the SongPolicy:
class SongPolicy < ApplicationPolicy
class Scope < Scope
end
def index?
end
def show?
end
def create?
user.has_role?(:admin) || user.has_role?(:collaborator) # This is ignored.
end
def new?
create?
end
def update?
create?
end
def edit?
create?
end
def destroy?
user.has_role?(:admin)
end
def delete?
destroy?
end
end
Not sure what else to try here, I'm sure I'm missing something, if someone with more knowledge of Pundit could let me know their thoughts on why a statement for one policy can leak into another, it would be really helpful.
You're calling authorize on the current user, which is a User, so Pundit is going to infer the UserPolicy policy. It won't automatically infer the SongPolicy policy unless you provide a Song record, even if you're in the SongController controller.
If you want to use a different policy, you'll need to provide it via authorize(policy_class:).
authorize Current.user, policy_class: SongPolicy
Implicit authorization like this is generally a code smell. Ideally, you should be explicitly authorizing the current Song record(s) against the current user context.
My opinion is that you have a misconception on Pundit's approach. Particularly you're twisting the subject of the authorization with the object of the authorization. Let's try to explain.
You have an actor who wants to apply an action on an object. The object may be authorized to receive the action.
By default Pundit's always consider the actor to be the current_user.
The action is a method on a Policy.
The object is the resource you're working on; in the most trivial scenario it could be an ActiveRecord object - but it doesn't have to.
Pundit's authorize methods is intended, in plain english, as "authorize the the resource bar to receive the action foo from the current user".
What you're trying to do is instead "authorize the current user to apply the action foo on the resource bar.
What's the difference? The subject and the object of the authorization are swapped. IMO, while doing the authorization process, you should respond to the question: "Is this object authorized to receive this action by the actor?"
object action
------------ ------
authorize Current.user, :edit?
NOTE: the actor implicitly is current_user
NOTE: if action is not declared, then it will implicitly be action_name
which resolves to the question "is this specific user authorized to receive :edit? from the current user?"
Following the reasoning, this is what I'd consider the right approach for your example scenario:
class SongsController < ApplicationController
before_action :require_user_logged_in!, :authorization, except: [:index, :show]
private
def authorization
authorize Song
end
end
I do not advise to rely on callbacks and I'd rather write more explicit code
def edit
#song = Song.find(params[:id])
authorize #song, :edit?
end
This code resolves to the question "is this specific song authorized to receive :edit? from the current user?"
A word of warning about using a custom policy_class
like in
authorize Current.user, policy_class: SongPolicy
With this code the authorization will be made by calling SongPolicy#edit? but the record will regularly be set to Current.user's value ; let's suppose to have
class SongPolicy
def edit?
record.in_my_playlist?
end
end
where in_my_playlist? is Song's instance method: you'll end having
undefined method `in_my_playlist?` for #<User>
Probably you're not doing the thing you intended to do there.
A word of warning about the use of Current.user into your logic
If Current.user is using http://api.rubyonrails.org/classes/ActiveSupport/CurrentAttributes.html and your entire application is relying on that singleton, then you probably want to redefine Pundit's default user as documented here
class ApplicationController < ActionController::Base
def pundit_user
Current.user
end
end
otherwise you'll end up having your business logic and your authorization logic relying on two - potentially - different sources of truth.
I'm using the pundit gem and trying to figure out how to use it to prevent access to an index page that belongs to a user other than the current_user.
The examples only talk about how to scope the results to the current_user but no how to actually prevent access to the page itself if the current_user is NOT the owner of the record.
Any help appreciated
Thanks
Maybe you want something like this? (For class ModelName)
# /policies/model_name_policy.rb
class ModelNamePolicy
attr_reader :current_user, :resource
def initialize(current_user, resource)
#current_user = current_user
#resource = resource
end
def index?
current_user.authorized_to_edit?(resource)
end
end
# /models/user.rb
class User < ActiveRecord::Base
def authorized_to_edit?(resource)
admin? | (id == resource.created_by) # Or whatever method you want to call on your model to determine ownership
end
end
EDIT: Note that you will also need to call authorize from your controller to invoke the policy.
I am trying to figure out how to write pundit permissions in my Rails 4 app.
I have an article model, with an article policy. The article policy has:
class ArticlePolicy < ApplicationPolicy
attr_reader :user, :scope
def initialize(user, record, scope)
#scope = scope
super(user, record)
end
class Scope < Scope
def resolve
if user == article.user
scope.where(user_id: user_id)
elsif approval_required?
scope.where(article.state_machine.in_state?(:review)).(user.has_role?(:org_approver))
else
article.state_machine.in_state?(:publish)
end
end
end
# TO DO - check if this is correct - I'm not sure.
# I now think I don't need the index actions because I have changed the action in the articles controller to look for policy scope.
# def index?
# article.state_machine.in_state?(:publish)
# end
def article
record
end
The articles controller has:
def index
#articles = policy_scope(Article)
# query = params[:query].presence || "*"
# #articles = Article.search(query)
end
I am following the pundit documents relating to scopes and trying to figure out why the index action shown in the policy documents isn't working for me. I have tried the following (as shown in the docs):
<% policy_scope(#user.articles).sort_by(&:created_at).in_groups_of(2) do |group| %>
but I get this error:
undefined local variable or method `article' for #<ArticlePolicy::Scope:0x007fff08ae9f48>
Can anyone see where I've gone wrong?
I'm not sure that #user.articles is right. In my construct, articles belong to users, but in my index action, I want to show every user the articles that my scopes allow them to see.
You can try this in your action in controller.
#articles = policy_scope(Article).all
It will get all the articles. If you want to get the articles based on search params, you can try this.
#q = policy_scope(Article).search(params[:query])
#articles = #q.result
I think you may need to explicitly set article as an accessor in the Scope class as the error indicates that it doesn't recognise 'article'. Try something like
attr_accessor :article
set it in an initialize method and you can probably do away with the article method.
def initialize(record)
#article = record
end
I'm using Pundit for authorization and I want to make use of its scoping mechanisms for multi-tenancy (driven by hostname).
I've been doing this manually to date by virtue of:
class ApplicationController < ActionController::Base
# Returns a single Client record
def current_client
#current_client ||= Client.by_host(request.host)
end
end
And then in my controllers doing things like:
class PostsController < ApplicationController
def index
#posts = current_client.posts
end
end
Pretty standard fare, really.
I like the simplicity of Pundit's verify_policy_scoped filter for ensuring absolutely every action has been scoped to the correct Client. To me, it really is worthy of a 500 error if scoping has not been officially performed.
Given a Pundit policy scope:
class PostPolicy < ApplicationPolicy
class Scope < Scope
def resolve
# have access to #scope => Post class
# have access to #user => User object or nil
end
end
end
Now, Pundit seems to want me to filter Posts by user, e.g.:
def resolve
scope.where(user_id: user.id)
end
However, in this scenario I actually want to filter by current_client.posts as the default case. I'm not sure how to use Pundit scopes in this situation but my feeling is it needs to look something like:
def resolve
current_client.posts
end
But current_client is naturally not going to be available in the Pundit scope.
One solution could be to pass current_client.posts to policy_scope:
def index
#posts = policy_scope(current_client.posts)
end
But I feel this decentralizes my tenancy scoping destroys the purpose of using Pundit for this task.
Any ideas? Or am I driving Pundit beyond what it was designed for?
The most "Pundit-complient" way to deal with this problem would be to create a scope in your Post model:
Class Post < ActiveRecord::Base
scope :from_user, -> (user) do
user.posts
end
end
Then, you will be able to use it in your policy, where user is filled with the current_user from your controller:
class PostPolicy < ApplicationPolicy
class Scope
attr_reader :user, :scope
def initialize(user, scope)
#user = user
#scope = scope
end
def resolve
scope.from_user(user)
end
end
end
If you are returning an ActiveRecord::Relation from the scope, you can stop reading from here.
If your scope returns an array
The default ApplicationPolicy implement the method show using a where:
source.
So if your scope does not return an AR::Relation but an array, one work-around could be to override this show method:
class PostPolicy < ApplicationPolicy
class Scope
# same content than above
end
def show?
post = scope.find do |post_in_scope|
post_in_scope.id == post.id
end
post.present?
end
end
Whatever your implementation is, you just need to use the PostPolicy from your controller the "Pundit-way":
class PostsController < ApplicationController
def index
#posts = policy_scope(Post)
end
def show
#post = Post.find(params[:id])
authorize #post
end
end
Using Rails 3.2. I am trying to secure my app by checking user permission on all crud actions. Here is one of the examples:
class StatesController < ApplicationController
def create
#country = Country.find(params[:country_id])
if can_edit(#country)
#state.save
else
redirect_to country_path
end
end
def destroy
#country = Country.find(params[:country_id])
if can_edit(#country)
#state = State.find(params[:id])
#state.destroy
else
redirect_to country_path
end
end
end
class ApplicationController < ActionController::Base
def is_owner?(object)
current_user == object.user
end
def can_edit?(object)
if logged_in?
is_owner?(object) || current_user.admin?
end
end
end
I notice that I have been wrapping can_edit? in many controllers. Is there a DRYer way to do this?
Note: All must include an object to check if the logged in user is the owner.
You are looking for an authorization library. You should look at CanCan which allows you to set certain rules about which objects can be accessed by particular users or groups of users.
It has a method, load_and_authorize_resource, which you can call in a given controller. So your statues controller would look like:
class StatesController < ApplicationController
load_and_authorize_resource :country
def create
#state.save
end
def destroy
#state = State.find(params[:id])
#state.destroy
end
end
CanCan will first load the country and determine whether or not the user has the right to view this resource. If not, it will raise an error (which you can rescue in that controller or ApplicationController to return an appropriate response".) You can then access #country in any controller action knowing that the user has the right to do so.