Role-based access control pattern in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Role Assignment in Firebase Security Rules

In Firebase Security Rules, roles are often assigned to users to control access. Which of the following best describes how roles are typically stored and checked in Firebase?

A Roles are stored as custom claims in the user's authentication token and checked in security rules.

B Roles are stored in Firestore documents and automatically enforced by Firebase without rules.

C Roles are assigned by Firebase automatically based on user email domains.

D Roles are stored in client-side local storage and verified by security rules.

💡 Hint

Think about where Firebase stores user-specific metadata securely for access control.

Firebase uses custom claims in the authentication token to store roles securely. Security rules then check these claims to allow or deny access.

❓ Configuration

intermediate

Firebase Security Rule for Admin Role Access

Given a Firebase Firestore collection named projects, which security rule snippet correctly allows only users with the admin role to read documents?

Firebase

match /projects/{projectId} {
  allow read: if request.auth.token.role == 'admin';
}

A allow read: if request.auth.token.role === 'admin';

B allow read: if request.auth.role == 'admin';

C allow read: if request.auth.token.roles.includes('admin');

D allow read: if request.auth.token.role == 'admin';

💡 Hint

Check the exact property name and syntax used in Firebase security rules for custom claims.

Firebase stores custom claims under request.auth.token. The role is a string, so equality check with == is correct.

❓ Architecture

advanced

Designing Role-based Access Control with Firebase and Firestore

You want to implement a role-based access control system where users can have multiple roles stored in Firestore under users/{userId}/roles as an array. Which approach is best to enforce access control in Firebase Security Rules?

A Store roles in client-side code and pass them as request parameters to security rules.

B Store roles as custom claims in the auth token and check them directly in security rules.

C Read the roles array from Firestore in security rules using <code>get()</code> and check if it contains the required role.

D Use Firebase Functions to check roles and bypass security rules.

💡 Hint

Consider performance and security best practices for Firebase Security Rules.

Security rules cannot reliably or efficiently read Firestore data for every request. Custom claims in auth tokens are the recommended way to store roles for fast and secure checks.

❓ security

advanced

Preventing Privilege Escalation in Firebase RBAC

Which practice helps prevent users from escalating their privileges by modifying their roles in Firebase?

A Only allow role changes through secure backend functions with admin privileges.

B Store roles in client-side local storage and trust the client to enforce them.

C Allow users to update their roles directly in Firestore documents.

D Use Firestore rules to allow anyone to write to the roles collection.

💡 Hint

Think about who should have permission to change roles and how to enforce it securely.

Roles must be managed securely on the backend. Allowing clients to modify roles directly risks privilege escalation.

❓ service_behavior

expert

Effect of Custom Claims Update on Firebase Auth Tokens

After updating a user's custom claims to add a new role, what must happen for the new role to be recognized in Firebase Security Rules?

A The Firestore database must be manually refreshed to sync roles.

B The new claims are immediately available without any user action.

C The user must sign out and sign back in to refresh their ID token with updated claims.

D The client must call a special Firebase API to refresh claims automatically.

💡 Hint

Consider how Firebase ID tokens cache custom claims and when they update.

Firebase ID tokens cache custom claims at sign-in. To get updated claims, the user must sign out and sign back in or force token refresh.