How to restrict access by role in Supabase RLS?

 

Step 1: Set Up a Supabase Project

 

To start with Supabase and implement role-based access control using Row Level Security (RLS), you'll first need to set up a Supabase project:

• Sign up for a Supabase account at https://supabase.io.
• Create a new project.
• Take note of your API keys and database credentials for later use.

 

Step 2: Define Your Database Schema

 

Before implementing RLS, you need a well-defined database schema. For instance, suppose we have a simple users table with the following fields:

• id: The primary key of the user.
• email: The user's email address.
• role: The role assigned to the user (e.g., "admin", "editor", "viewer").

Create the users table by navigating to the SQL Editor and running the following SQL:

CREATE TABLE users (
  id SERIAL PRIMARY KEY,
  email VARCHAR(255) UNIQUE NOT NULL,
  role VARCHAR(50) NOT NULL CHECK (role IN ('admin', 'editor', 'viewer'))
);

 

Step 3: Enable Row Level Security (RLS)

 

After defining your schema, the next step is to enable RLS on your table. This feature allows you to define policies that restrict table access based on custom criteria.

In the Supabase dashboard, navigate to your database table, and execute the following SQL command in the SQL Editor to enable RLS for the users table:

ALTER TABLE users ENABLE ROW LEVEL SECURITY;

 

Step 4: Create Role-Based Access Policies

 

Now, define access policies based on user roles. Here is how you can create policies for different roles. Execute the following SQL commands in the SQL Editor:

• Allow "admin" to select all rows:

CREATE POLICY "Admins can read all data"
  ON users FOR SELECT
  USING (role = 'admin');

• Allow "editor" to update rows with certain conditions:

CREATE POLICY "Editors can update their data"
  ON users FOR UPDATE
  USING (role = 'editor' AND auth.uid() = id);

• Allow "viewer" to only select rows related to them:

CREATE POLICY "Viewers can read their data"
  ON users FOR SELECT
  USING (role = 'viewer' AND auth.uid() = id);

Replace auth.uid() with the correct function or variable that establishes the link between your application authentication and the database user identifier.

 

Step 5: Test Your RLS Policies

 

After creating your RLS policies, it's imperative to test them to ensure they work as expected. You can do this directly through SQL queries in the Supabase dashboard or by integrating them into your application.

• Test with sample queries:

-- As an admin user
SELECT \* FROM users; -- should return all rows

-- As an editor user
UPDATE users SET email = '[email protected]' WHERE id = ; -- only updates their row

-- As a viewer user
SELECT \* FROM users WHERE id = ; -- should return only their row

Ensure you replace <editor_id> and <viewer_id> with actual test user IDs that you want to test against.

 

Step 6: Integrate with Your Application

 

Finally, integrate these RLS policies with your application. Ensure your application sets the correct session variables or tokens that map to the roles defined in your policies.

For instance, you might set JWT claims during authentication that reflect the user's role and use these claims to interact with the Supabase API.

 

Now you've set up a detailed role-based access control with RLS in Supabase! Make sure to further refine policies as needed based on your real-world requirements and test thoroughly before going live.