Secure Supabase Data: RLS Policy Implementation

Aug 10, 2025 by Luna Greco 48 views

Secure Supabase Data with Row Level Security (RLS) Policies

Securing your Supabase data is paramount, guys, especially when dealing with sensitive user information. One of the most effective ways to achieve this is by implementing Row Level Security (RLS) policies. This article will guide you through the process of setting up RLS in Supabase to ensure that users can only access their own data, while administrators retain full control. We'll break down the steps, from enabling RLS to creating policies for different tables and roles, and finally, testing those policies to make sure everything works as expected. So, let's dive in and fortify your Supabase database!

Understanding Row Level Security (RLS)

Before we jump into the implementation, let's understand what Row Level Security (RLS) is and why it's so crucial. RLS is a powerful feature that allows you to control access to specific rows in a database table based on certain conditions. Think of it as a gatekeeper for your data, ensuring that only authorized users can view or modify specific records. This is particularly important in multi-tenant applications where you need to isolate data between different users or organizations.

Why is RLS so important, you ask? Well, without RLS, you're essentially relying on your application code to enforce data access restrictions. This can become complex and error-prone as your application grows. Imagine having to write custom queries and logic to filter data based on the current user every time you interact with the database. That's a lot of extra work, and it's easy to make mistakes that could lead to security vulnerabilities.

RLS, on the other hand, moves the access control logic into the database itself. This means that the database is responsible for enforcing the rules, regardless of how the data is accessed. This provides a much stronger and more reliable security layer. It also simplifies your application code, as you can trust the database to handle access control.

Key benefits of using RLS include:

Enhanced Security: RLS provides a robust security layer by restricting data access at the database level.
Data Isolation: It ensures that users can only access their own data, preventing unauthorized access to sensitive information.
Simplified Application Code: By offloading access control to the database, RLS reduces the complexity of your application code.
Centralized Access Control: RLS policies are defined and managed in one place, making it easier to maintain and audit your security rules.
Compliance: RLS helps you comply with data privacy regulations by ensuring that data is only accessed by authorized individuals.

In essence, RLS is a fundamental building block for building secure and scalable applications with Supabase. It's a must-have for any application that handles sensitive data, and it's surprisingly easy to get started with.

Step-by-Step Guide to Implementing RLS in Supabase

Okay, guys, now that we understand the importance of RLS, let's get our hands dirty and implement it in Supabase. This step-by-step guide will walk you through the process of enabling RLS on your tables, creating policies for different user roles, and testing those policies to ensure they're working correctly. So, buckle up, and let's get started!

1. Enabling RLS on Tables

The first step is to enable RLS on the tables you want to protect. By default, RLS is disabled on all tables in Supabase. To enable it, you'll need to use the Supabase dashboard or the SQL editor. We'll cover both methods here.

Using the Supabase Dashboard:

Go to your Supabase project dashboard.
Navigate to the Table Editor.
Select the table you want to enable RLS on.
Click on the Policies tab.
Click the Enable RLS toggle.

Using the SQL Editor:

Go to your Supabase project dashboard.
Navigate to the SQL Editor.
Execute the following SQL command, replacing your_table_name with the actual name of your table:
```
ALTER TABLE your_table_name ENABLE ROW LEVEL SECURITY;
```

Repeat this process for all the tables you want to protect with RLS. In our scenario, we'll need to enable RLS on the users, invitations, orders, order_items, and payments tables.

Enabling RLS is like putting a lock on the door – it prevents anyone from accessing the data without the right key (i.e., a valid RLS policy).

2. Creating RLS Policies

Once RLS is enabled on a table, you need to create policies to define who can access which rows. RLS policies are based on conditions that are evaluated when a user attempts to access data. These conditions can be based on user roles, claims in the JWT (JSON Web Token), or any other relevant data.

We'll create policies for each of our tables, focusing on the following scenarios:

Users table: Users should only be able to access their own user data.
Invitations table: Users should only be able to access their own invitations, while administrators should have access to all invitations.
Orders table: Users should only be able to access their own orders, while administrators should have access to all orders.
Order_items table: Policies should inherit from the orders table, ensuring that users can only access order items associated with their orders.
Payments table: Policies should inherit from the orders table, ensuring that users can only access payments associated with their orders.

Let's start with the users table.

Creating a Policy for the Users Table

We want to ensure that users can only access their own user data. To achieve this, we'll create a policy that checks if the user_id in the users table matches the user_id in the authenticated user's JWT.

Using the Supabase Dashboard:

Go to the Table Editor and select the users table.
Click on the Policies tab.
Click Create a new policy.
Select the Template: Enable for individual users template.
Give the policy a name, such as users_access_policy.
In the Target roles section, select authenticated.
In the Policy definition section, enter the following expression:
```
auth.uid() = id
```
This expression checks if the authenticated user's ID (auth.uid()) matches the id column in the users table.
Select SELECT, UPDATE, and DELETE permissions.
Click Save.

Using the SQL Editor:

Go to the SQL Editor.

Execute the following SQL command:

CREATE POLICY users_access_policy
ON users
FOR ALL
TO authenticated
USING (auth.uid() = id);

This SQL command creates a policy named users_access_policy on the users table. The FOR ALL clause means that this policy applies to all operations (SELECT, INSERT, UPDATE, DELETE). The TO authenticated clause specifies that this policy applies to authenticated users. The USING clause defines the condition that must be met for the policy to be applied.

Creating Policies for the Invitations Table

For the invitations table, we need to create two policies: one for regular users and one for administrators.

Users: Should only be able to access their own invitations.
Administrators: Should have access to all invitations.

First, let's create the policy for regular users.

Using the Supabase Dashboard:

Go to the Table Editor and select the invitations table.
Click on the Policies tab.
Click Create a new policy.
Select the Template: Enable for individual users template.
Give the policy a name, such as invitations_user_policy.
In the Target roles section, select authenticated.
In the Policy definition section, enter the following expression (assuming you have a user_id column in your invitations table):
```
auth.uid() = user_id
```
Select SELECT, INSERT, UPDATE, and DELETE permissions.
Click Save.

Using the SQL Editor:

Go to the SQL Editor.

Execute the following SQL command:

CREATE POLICY invitations_user_policy
ON invitations
FOR ALL
TO authenticated
USING (auth.uid() = user_id);

Now, let's create the policy for administrators. We'll assume you have a service_role role defined in your Supabase Auth settings (we'll cover roles and permissions later).

Using the Supabase Dashboard:

Go to the Table Editor and select the invitations table.
Click on the Policies tab.
Click Create a new policy.
Select the Template: Enable access to all rows template.
Give the policy a name, such as invitations_admin_policy.
In the Target roles section, select service_role.
Click Save.

Using the SQL Editor:

Go to the SQL Editor.

Execute the following SQL command:

CREATE POLICY invitations_admin_policy
ON invitations
FOR ALL
TO service_role
USING (true); -- Admins can access all rows

Creating Policies for the Orders Table

The policies for the orders table will be similar to the invitations table, with separate policies for regular users and administrators.

Users: Should only be able to access their own orders.
Administrators: Should have access to all orders.

Let's create the policy for regular users first.

Using the Supabase Dashboard (Orders Table - User Policy):

Follow the same steps as for the invitations_user_policy, but select the orders table and name the policy orders_user_policy.
Use the following expression in the Policy definition section (assuming you have a user_id column in your orders table):
```
auth.uid() = user_id
```

Using the SQL Editor (Orders Table - User Policy):

CREATE POLICY orders_user_policy
ON orders
FOR ALL
TO authenticated
USING (auth.uid() = user_id);

Now, let's create the policy for administrators.

Using the Supabase Dashboard (Orders Table - Admin Policy):

Follow the same steps as for the invitations_admin_policy, but select the orders table and name the policy orders_admin_policy.

Using the SQL Editor (Orders Table - Admin Policy):

CREATE POLICY orders_admin_policy
ON orders
FOR ALL
TO service_role
USING (true); -- Admins can access all rows

Creating Policies for the Order_items and Payments Tables (Inheriting from Orders)

For the order_items and payments tables, we want the policies to inherit from the orders table. This means that a user should only be able to access order items and payments that are associated with their orders. To achieve this, we'll create policies that join these tables with the orders table and check the user_id in the orders table.

Using the Supabase Dashboard (Order_items Table):

Go to the Table Editor and select the order_items table.
Click on the Policies tab.
Click Create a new policy.
Select the Template: Enable for individual users template.
Give the policy a name, such as order_items_policy.
In the Target roles section, select authenticated.
In the Policy definition section, enter the following expression (assuming you have an order_id column in your order_items table and the orders table has a user_id column):
```
EXISTS (SELECT 1 FROM orders WHERE orders.id = order_items.order_id AND orders.user_id = auth.uid())
```
Select SELECT, INSERT, UPDATE, and DELETE permissions.
Click Save.

Using the SQL Editor (Order_items Table):

CREATE POLICY order_items_policy
ON order_items
FOR ALL
TO authenticated
USING (EXISTS (SELECT 1 FROM orders WHERE orders.id = order_items.order_id AND orders.user_id = auth.uid()));

Using the Supabase Dashboard (Payments Table):

Go to the Table Editor and select the payments table.
Click on the Policies tab.
Click Create a new policy.
Select the Template: Enable for individual users template.
Give the policy a name, such as payments_policy.
In the Target roles section, select authenticated.

In the Policy definition section (assuming you have an order_id column in your payments table):

EXISTS (SELECT 1 FROM orders WHERE orders.id = payments.order_id AND orders.user_id = auth.uid())

Select SELECT, INSERT, UPDATE, and DELETE permissions.
Click Save.

Using the SQL Editor (Payments Table):

CREATE POLICY payments_policy
ON payments
FOR ALL
TO authenticated
USING (EXISTS (SELECT 1 FROM orders WHERE orders.id = payments.order_id AND orders.user_id = auth.uid()));

3. Creating Roles and Permissions in Supabase Auth

Now that we've created the RLS policies, we need to ensure that the appropriate roles and permissions are set up in Supabase Auth. Supabase Auth provides built-in roles like authenticated and service_role. The authenticated role is automatically assigned to any authenticated user, while the service_role is designed for administrative tasks and bypasses RLS policies.

If you need more granular control, you can create custom roles and assign specific permissions to them. However, for this example, we'll stick with the built-in roles.

To check your roles, go to the Supabase dashboard, navigate to Authentication, and then click on Roles. You should see the authenticated and service_role roles listed there.

If you need to create a custom role, you can do so using the Supabase Auth API or the supabase-js library. For example:

const { data, error } = await supabase.auth.admin.createRole({ id: 'admin' });

However, for the purpose of this article and based on the initial tasks defined, using the service_role for administrative tasks is sufficient. This is because our RLS policies for admin access are already set to service_role.

4. Testing the RLS Policies

The final step is to test the RLS policies to ensure they're working correctly. This is a crucial step to verify that your data is properly protected.

To test the policies, you'll need to simulate different user scenarios. Here's a breakdown of what you should test:

Regular User:
- Log in as a regular user.
- Try to access your own data in the users, invitations, orders, order_items, and payments tables. You should be able to access this data.
- Try to access data belonging to other users in the same tables. You should not be able to access this data.
Administrator:
- Log in as an administrator (using a service role key or a user with the service_role).
- Try to access data in all the tables. You should be able to access all data, regardless of the user.

You can use the Supabase API Explorer or your application code to perform these tests. Here's an example of how to test the RLS policies using the Supabase API Explorer:

Go to your Supabase project dashboard.
Navigate to the API Explorer.
Select the table you want to test.
Choose the HTTP method (e.g., GET, POST, PUT, DELETE).
Set the authorization header to the JWT of the user you want to simulate.
Execute the request and verify the results.

Example Test Scenario:

Let's say you have two users: user1 (with user ID 1) and user2 (with user ID 2). You also have an administrator with the service_role.

Test as user1:
- Log in as user1 and obtain their JWT.
- Use the API Explorer to fetch data from the users table with the filter id = 1. You should get user1's data.
- Use the API Explorer to fetch data from the users table with the filter id = 2. You should get an empty result or an error, indicating that you don't have access.
- Test accessing invitations, orders, order items, and payments in a similar way, ensuring you can only access data associated with user1.
Test as user2:
- Repeat the same tests as user1, but using user2's JWT. You should only be able to access data associated with user2.
Test as Administrator:
- Use the service role key or log in as a user with the service_role.
- Use the API Explorer to fetch data from all tables without any filters. You should be able to access all data.

If your tests pass, congratulations! You've successfully implemented RLS in Supabase. If not, double-check your policies and ensure that the conditions are correct.

Documenting Permissions

Guys, once you've implemented and tested your RLS policies, it's crucial to document them properly. Good documentation helps you understand your security rules and makes it easier to maintain and audit them in the future. It's like having a roadmap for your data access controls, ensuring everyone knows who has access to what and why.

Your documentation should include the following information:

Table: The table the policy applies to.
Policy Name: The name of the policy.
Description: A brief description of what the policy does.
Target Roles: The roles the policy applies to (e.g., authenticated, service_role).
Permissions: The operations the policy allows (e.g., SELECT, INSERT, UPDATE, DELETE).
Condition: The SQL expression that defines the policy's condition.
Example: A specific scenario illustrating how the policy works.

For our example, here's how you could document the policies we created:

Users Table

Policy Name: users_access_policy
Description: Allows authenticated users to access their own user data.
Target Roles: authenticated
Permissions: SELECT, UPDATE, DELETE
Condition: auth.uid() = id
Example: User with ID 1 can only access the row in the users table where id = 1.

Invitations Table

Policy Name: invitations_user_policy
Description: Allows authenticated users to access their own invitations.
Target Roles: authenticated
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: auth.uid() = user_id
Example: User with ID 1 can only access rows in the invitations table where user_id = 1.
Policy Name: invitations_admin_policy
Description: Allows administrators to access all invitations.
Target Roles: service_role
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: true
Example: Users with the service_role can access all rows in the invitations table.

Orders Table

Policy Name: orders_user_policy
Description: Allows authenticated users to access their own orders.
Target Roles: authenticated
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: auth.uid() = user_id
Example: User with ID 1 can only access rows in the orders table where user_id = 1.
Policy Name: orders_admin_policy
Description: Allows administrators to access all orders.
Target Roles: service_role
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: true
Example: Users with the service_role can access all rows in the orders table.

Order_items Table

Policy Name: order_items_policy
Description: Allows authenticated users to access order items associated with their orders.
Target Roles: authenticated
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: EXISTS (SELECT 1 FROM orders WHERE orders.id = order_items.order_id AND orders.user_id = auth.uid())
Example: User with ID 1 can only access rows in the order_items table where order_id matches an order in the orders table belonging to user 1.

Payments Table

Policy Name: payments_policy
Description: Allows authenticated users to access payments associated with their orders.
Target Roles: authenticated
Permissions: SELECT, INSERT, UPDATE, DELETE
Condition: EXISTS (SELECT 1 FROM orders WHERE orders.id = payments.order_id AND orders.user_id = auth.uid())
Example: User with ID 1 can only access rows in the payments table where order_id matches an order in the orders table belonging to user 1.

You can store this documentation in a variety of formats, such as a Markdown file in your project repository, a wiki page, or a dedicated documentation platform. The key is to make it accessible and easy to understand.

Regularly review and update your documentation as your policies evolve. This will help you maintain a clear understanding of your security posture and ensure that your data is always protected.

Conclusion

Implementing Row Level Security (RLS) in Supabase is a vital step in securing your data and ensuring that users only access what they're authorized to see. By following this guide, you've learned how to enable RLS on your tables, create policies for different user roles, and test those policies to ensure they're working correctly. You've also learned the importance of documenting your permissions for future maintenance and auditing.

Remember, data security is an ongoing process. Regularly review your RLS policies and adapt them as your application evolves and your security needs change. By staying proactive and implementing best practices like RLS, you can build a secure and scalable application with Supabase. Keep up the great work, guys, and stay secure!