Introduction

Authentication and user role management are crucial aspects of any modern web application. Supabase, a powerful open-source alternative to Firebase, provides a robust set of tools to handle these tasks efficiently. In this guide, we'll explore how to implement and manage authentication and user roles in Supabase, ensuring your application's security and flexibility.

Setting Up Basic Authentication

Supabase offers built-in authentication that's easy to set up and use. Let's start with the basics:

1. Enable auth providers in the Supabase dashboard:

   • Go to Authentication > Settings
   • Enable the providers you want (e.g., Email, Google, GitHub)

2. Implement sign-up functionality in your app:

const { user, error } = await supabase.auth.signUp({
  email: 'example@email.com',
  password: 'example-password',
})

3. Implement sign-in functionality:

const { user, error } = await supabase.auth.signIn({
  email: 'example@email.com',
  password: 'example-password',
})

4. Handle sign-out:

const { error } = await supabase.auth.signOut()

Creating and Managing User Roles

Supabase uses PostgreSQL roles for managing user permissions. Here's how to create and manage roles:

1. Create a new role in the SQL editor:

CREATE ROLE app_user;

2. Grant necessary permissions to the role:

GRANT USAGE ON SCHEMA public TO app_user;
GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA public TO app_user;

3. Assign the role to a user upon sign-up:

const { user, error } = await supabase.auth.signUp({
  email: 'example@email.com',
  password: 'example-password',
})

if (user) {
  const { data, error } = await supabase
    .from('profiles')
    .insert({ id: user.id, role: 'app_user' })
}

Implementing Row-Level Security (RLS)

Row-Level Security allows you to control access to rows in a table based on the user requesting the data. Here's how to set it up:

1. Enable RLS on a table:

ALTER TABLE your_table ENABLE ROW LEVEL SECURITY;

2. Create a policy:

CREATE POLICY "Users can only access their own data" ON your_table
  FOR ALL
  USING (auth.uid() = user_id);

This policy ensures that users can only access rows where their auth.uid() matches the user_id column.

Custom Claims and JWT Tokens

Supabase allows you to add custom claims to JWT tokens, which can be used for more granular permission control:

1. Add custom claims in the SQL editor:

CREATE OR REPLACE FUNCTION public.handle_new_user()
RETURNS trigger AS $$
BEGIN
  INSERT INTO public.profiles (id, role)
  VALUES (new.id, 'app_user');
  
  new.raw_app_meta_data := jsonb_set(
    coalesce(new.raw_app_meta_data, '{}'::jsonb),
    '{role}',
    '"app_user"'
  );
  
  RETURN new;
END;
$$ LANGUAGE plpgsql SECURITY DEFINER;

CREATE TRIGGER on_auth_user_created
  AFTER INSERT ON auth.users
  FOR EACH ROW EXECUTE PROCEDURE public.handle_new_user();

2. Use the custom claim in your policies:

CREATE POLICY "Admin users have full access" ON your_table
  FOR ALL
  USING (auth.jwt() ->> 'role' = 'admin');

Best Practices for Auth and Role Management

1. Use strong password policies
2. Implement multi-factor authentication for sensitive operations
3. Regularly audit and update user roles and permissions
4. Use the principle of least privilege when assigning roles
5. Implement proper error handling for auth operations
6. Regularly rotate security keys and tokens

Advanced Techniques

1. Implement social auth providers for a smoother user experience
2. Use Supabase's Auth Helpers for framework-specific integrations
3. Implement custom email templates for auth-related communications
4. Use Supabase's Realtime features to sync user data across devices

By following these guidelines and leveraging Supabase's powerful features, you can create a secure and flexible authentication and user role management system for your application. Remember to always keep security at the forefront of your development process and stay updated with the latest Supabase features and best practices.