#refineweek: Implementing Role Based Access Control

In this post, we implement Role Based Access Control (RBAC) on our Pixels Admin app. Pixels Admin serves as the admin dashboard of our Pixels client app that we built previously in the refineWeek series.

This is Day 6, and refineWeek is a seven-part tutorial that aims to help developers learn the ins-and-outs of refine's powerful capabilities and get going with refine within a week.

Overview

On Day 5, we implemented CRUD functionalities on our dashboard resources: users and canvases.

Taking it farther today, we add authorization for actions related to canvases resource at /canvases route. We have have two roles that seek authorization: editor and admin. An editor is allowed to only promote and unpromote a canvas, whereas an admin is free to promote / unpromote a canvas as well as delete it. Here's a short description of the specs:

editor can promote and unpromote a canvas.
editor cannot perform any other action.
admin can promote and unpromote a canvas.
admin can delete a canvas.
admin cannot perform any other action.

We manage RBAC and authorization using Casbin models and policies. We then make use of refine's accessControlProvider and associated hooks to enforce policies for these roles.

For the backend, we set and store user roles with the help of Supabase Custom Claims. Supabase Custom Claims are a handy mechanism to store user roles information on the auth.users table.

We also dig into some low level code in the <DeleteButton /> component that refine's Ant Design package gives us to see how authorization comes baked into some of the related components.

Let's start with Casbin.

Casbin with refine

In this app, we are implementing Role Based Access Control model with Casbin so we assume you are at least familiar with the RBAC related models and policies.

If you are not familiar with Casbin, please feel free to go through how it works. For a complete beginner, I recommend understanding the following sections in the Casbin docs:

If / when you are familiar, lovely yay! Be with me, go ahead and install Casbin:

yarn add casbin

Casbin Model and Policies

We are using the following model and policy adapter for our RBAC implementation:

// src/casbin/accessControl.ts

import { newModel, StringAdapter } from "casbin";

export const model = newModel(`
  [request_definition]
  r = sub, obj, act

  [policy_definition]
  p = sub, obj, act

  [role_definition]
  g = _, _

  [policy_effect]
  e = some(where (p.eft == allow))

  [matchers]
  m = g(r.sub, p.sub) && keyMatch(r.obj, p.obj) && regexMatch(r.act, p.act)
`);

export const adapter = new StringAdapter(`
  p, admin, users, list
  p, admin, canvases, (list)|(edit)|(delete)

  p, editor, users, list
  p, editor, canvases, (list)|(edit)
`);

A quick run down of the model is:

with the request definition in r = sub, obj, act, Casbin scans the request for the subject (editor or admin), object (the resource) and the action (get, create, edit, etc.).
with the same parameters in p = sub, obj, act, it compares the request parameters with those in the policy instances declared in the policy adapter
with the two level grouping in g = _, _, we are declaring user role inheritance can go two levels deep, i.e. an admin is an user.

The adapter holds our instances of policies produced from p. The policies above basically allows:

an admin to list users.
an admin to list, edit and delete canvases.
an editor to list users.
an editor to list and edit canvases.

Browser Fallbacks for Casbin

We need to configure polyfills for casbin to work in a browser environment. We are using react-app-rewired to override some of the configurations of our app. So, let's first add the following to package.json:

yarn add react-app-rewired

And update the scripts:

// package.json

"scripts": {
    "start": "react-app-rewired start",
    "build": "react-app-rewired build",
    "eject": "react-scripts eject",
    "refine": "refine"
 },

After that add the following packages:

yarn add assert buffer crypto-browserify stream-browserify

yarn add -D https-browserify os-browserify path stream-http

And then include this config-overrides.js file to the root of the app folder.

Without these overrides, casbin versions >5 is known to throw errors.

With this out of the way and the Casbin model policies ready, it's time for us to define the accessControlProvider.

`<Refine />`'s `accessControlProvider`

<Refine />'s accessControlProvider is responsible for enforcing authorization on every request sent from the app. If we look at the <App /> component, we can see that it comes passed to the <Refine /> component with the boilerplate code:

// src/App.tsx
...
<Refine
    accessControlProvider={accessControlProvider}
/>
...

refine `can` Method

The accessControlProvider implements only one method named can. It has the following type signature:

type CanParams = {
    resource: string;
    action: string;
    params?: {
        resource?: IResourceItem;
        id?: BaseKey;
        [key: string]: any;
    };
};

Let's now work on the can method. We can see from the type definition that resource and action are compulsory. Initially we define our can method like this:

// providers/accessControlProvider.ts

import { newEnforcer } from "casbin";
import { CanParams, CanReturnType } from "@pankod/refine-core";
import { adapter, model } from "../casbin/accessControl";
import { supabaseClient } from "utility";

export const accessControlProvider = {
  can: async ({ resource, action }: CanParams): Promise<CanReturnType> => {
    const enforcer = await newEnforcer(model, adapter);
    const can = await enforcer.enforce("admin", resource, action);

    return Promise.resolve({
      can,
    });
  }
};

We will modify this gradually to witness the functionality facilitated out-of-the-box by refine for each role defined in the policies. We will finalize it after we update the getPermissions() method in Supabase authProvider.

But for now, notice in the above definition that we are passing the compulsory resource and action parameters to can. We expect the useCan() access control hook to take these two arguments.

For more use cases and implementations of can, feel free to go through the elaborate examples in this definitive and guiding post.

In the above code, we are initializing a Casbin Enforcer with the model and adapter. We want this enforcer to enforce the policies with its accepted arguments. At the end, we get the Boolean decision based on the model's policy effect.

From inside a component, the accessControlProvider.can method will be invoked via the useCan() hook.

With this code now, there should be no change in our UI. That is, we should be able to view the contents of both our /users and /canvases resources like they were before. When we visit the /canvases route, we should have all the buttons displayed.

We expect this behavior to change when we change the role. In the can method above let's set the first argument of enforcer.enforce() to "editor":

const can = await enforcer.enforce("editor", resource, action);

And if we refresh at /canvases, we can see that the Delete button on each row gets disabled.

This is because now our policy for editor has taken effect.

The Delete button gets disabled because @pankod/refine-antd's special buttons like the <DeleteButton /> are enabled or disabled based on the result of access control enforcement. Our editor policies do not allow a delete action on canvases resource, so the Delete button is disabled.

Visit this section of the accessControlProvider API reference for the complete list of buttons that check for and depend on user authorization state in refine.

At this point, we have manipulated the role with changes in our code. This should, however, come from the authProvider's getPermissions() method.

So, let's look how to get the roles from our Supabase database next.

User Permissions with Supabase in Refine

In refine, user roles are fetched by authProvider's getPermissions() method. It is already defined for us by @pankod/refine-supabase. Right now, it looks like this:

// src/providers/authProvider.ts

getPermissions: async () => {
    const user = supabaseClient.auth.user();

    if (user) {
        return Promise.resolve(user.role);
    }
},

However, Supabase in itself does not support setting user roles to users in the auth.users table. So, it is not possible to set editor and admin roles we need for our designated users. And only two role options are available to the front end app: authenticated and anon.

So, before we can use the getPermissions() method, we have to set up custom user roles. One way to implement this is with Supabase Custom Claims.

Setting Up User Roles with Supabase Custom Claims

Supabase Custom Claims is a community contribution that enables setting additional data to the access token that a user receives from Supabase. These claims are stored in the auth.users.raw_app_meta_data field and is sent to the client with the access token. We are going to use these custom claims to set and retrieve user roles for our app.

Supabase does not support custom claims on its own. Due credits to @burggraf, they are enabled by installing a number of functions on our database. These functions allow us to set and get custom claims for a particular user in the auth.users table.

Here are two crucial particulars on how they work:

Only a user with a { claims_admin: true } claim can set claims data on others. So we need to bootstrap a claims_admin role for a first user using the Supabase SQL Editor.
Our app can access the getter and setter functions via Supabase Remote Procedure Calls (RPCs) with the supabaseClient.rpc() method.

With these in mind, let's go ahead and set up Supabase Custom Claims on our database.

Installing Custom Claims Functions

Let's start with installing the custom claims SQL functions. Copy, paste and run the install.sql script in your Supabase SQL Editor.

Take a note of the function named get_my_claims():

// https://github.com/supabase-community/supabase-custom-claims/blob/main/install.sql

CREATE OR REPLACE FUNCTION get_my_claims() RETURNS "jsonb"
    LANGUAGE "sql" STABLE
    AS $$
  select
      coalesce(nullif(current_setting('request.jwt.claims', true), '')::jsonb -> 'app_metadata', '{}'::jsonb)::jsonb

This SQL function will help us to remotely get user roles for our app. And we are going to call it from our getPermissions() method. To understand the details, please read through the Supabhase Custom Claims page.

Bootstrapping Claims Admin Role

We then have to bootstrap a claims_admin role because only users with { claims_admin: true } can set claims data for other users. This is necessary for security of the claims admin feature, and not for our app code. So, in the Supabase SQL Editor run the following query:

select set_claim('designated-user-uuid', 'claims_admin', 'true');

This will allow the user with id designated-user-uuid to set roles for other users from inside our app.

We can also set other data from the SQL Editor, such as the role itself. Let's use the following SQL query to set roles for some of our designated users. Doing so will help us in the coming sections:

select set_claim('designated-user-uuid', 'role', '"editor"');
select set_claim('another-designated-user-uuid', 'role', '"admin"');

We need to take special care about using the correct quotations. More on this in this section.

With these done, we are ready to update our getPermissions() and can methods.

refine `getPermissions()` with Supabase Custom Claims

Here's the adjusted getPermissions() method:

// providers/dataProvider.ts

getPermissions: async () => {
    const user = supabaseClient.auth.user();

    if (!user) {
        return Promise.reject();
    }

    const { data } = await supabaseClient.rpc('get_my_claim', { claim: 'role' });
    return Promise.resolve(data);
},

Here, we are basically using the supabaseClient.rpc() method to call the get_my_claims SQL function remotely.

refine `can` Method for Supabase Custom Roles

And now, we can finalize our can method with role received from authProvider.getPermissions():

// providers/accessControlProvider.ts

export const accessControlProvider = {
    can: async ({ resource, action }: CanParams): Promise<CanReturnType> => {
        const role = await authProvider.getPermissions();

        const enforcer = await newEnforcer(model, adapter);
        const can = await enforcer.enforce(role, resource, action);

        return Promise.resolve({
            can,
        });
    }
};

Earlier on, we have set admin and editor roles for a few designated users using the Supabase SQL Editor. Now, logging into their respective accounts will display the dashboard with Casbin policies applied.

In the /canvases route, an editor account should have the Delete buttons disabled because we don't have it in our policies.

In contrast, it is enabled for an admin role:

But, wait! We haven't used the useCan() hook or the <CanAccess /> component anywhere yet. How does refine get the value of role to decide whether to enable or disable the button? Let's find out next!

Low Level Inspection

If we dig into the @pankod/refine-antd package for the <DeleteButton /> component, we can see that useCan() hook is used to decide the authorization status:

// node_modules/@pankod/refine-antd/src/components/buttons/delete/index.ts

export const DeleteButton: React.FC<DeleteButtonProps> = ({
    ...
}) => {
    ...

    const { data } = useCan({
        resource: resourceName,
        action: "delete",
        params: { id, resource },
        queryOptions: {
                enabled: accessControlEnabled,
        },
    });

    if (accessControlEnabled && hideIfUnauthorized && !data?.can) {
        return null;
    }

    ...
};

Since authorization comes baked in with <DeleteButton />, we didn't have to worry about it in our case.

Summary

In this post, we implemented Role Based Access Control on users and canvases resources using refine's accessControlProvider in our Pixels Admin app.

We used Casbin model and policies to enforce authorization for editor and admin roles. We saw how the accessControlProvider.can method is used to enforce Casbin policies based on roles fetched from the backend using the authProvider.getPermissions method. We also learned how refine-antd buttons like the <DeleteButton /> implements access control via the useCan() access hook.

In the next episode, we will explore the auditLogProvider prop and add audit logging for pixels activities to both our Pixels and Pixels Admin apps.