Firebase Authentication Specialist

Comprehensive Firebase Authentication implementation covering Google ecosystem integration, social authentication providers, phone authentication, anonymous auth, custom claims, and Security Rules integration.

Quick Reference

Firebase Auth Core Features:

• Google Sign-In: Native Google ecosystem integration with Cloud Identity
• Social Auth: Facebook, Twitter/X, GitHub, Apple, Microsoft, Yahoo
• Phone Auth: SMS-based verification with international support
• Anonymous Auth: Guest access with account linking upgrade path
• Custom Claims: Role-based access and admin privileges
• Security Rules: Firestore, Storage, and Realtime Database integration

Context7 Documentation Access:

• Use resolve-library-id with "firebase" to get Context7 library ID
• Use get-library-docs with resolved ID and topic "authentication" for latest API

Platform SDK Support:

• Web: firebase/auth with modular SDK (v9+)
• iOS: FirebaseAuth with Swift and SwiftUI
• Android: firebase-auth with Kotlin
• Flutter: firebase_auth package
• React Native: @react-native-firebase/auth

Quick Decision Tree:

• Need Google ecosystem integration? Use Firebase Auth
• Building mobile-first application? Use Firebase Auth
• Need serverless Cloud Functions? Use Firebase Auth
• Need anonymous guest access? Use Firebase Auth
• Existing Firebase infrastructure? Use Firebase Auth

Module Index

This skill uses progressive disclosure with specialized modules for detailed implementation guidance.

Social Authentication

File: modules/social-auth.md

Covers Google Sign-In, Facebook Login, Apple Sign-In, Twitter/X, GitHub, and Microsoft authentication. Includes web, Flutter, iOS, and Android implementations with configuration requirements and error handling.

Key Topics:

• Google Sign-In with OAuth scopes and custom parameters
• Facebook Login with Graph API access
• Apple Sign-In (required for iOS apps with third-party login)
• Account linking between providers
• Error handling for popup and redirect flows

Phone Authentication

File: modules/phone-auth.md

Covers SMS-based phone number authentication with international support, reCAPTCHA verification, and platform-specific implementations.

Key Topics:

• Web implementation with RecaptchaVerifier
• Flutter verifyPhoneNumber flow with auto-verification
• iOS and Android native implementations
• E.164 phone number formatting
• Error handling and rate limiting

Custom Claims and Role Management

File: modules/custom-claims.md

Covers custom claims, role-based access control (RBAC), and admin privileges with Security Rules integration.

Key Topics:

• Setting claims with Admin SDK (Node.js, Python, Go)
• Cloud Functions for claim management
• Reading claims on client (Web, Flutter, iOS)
• Security Rules integration for Firestore and Storage
• Token refresh strategies

Implementation Guide

Firebase Project Setup

Step 1: Create Firebase project at console.firebase.google.com Step 2: Add your app (Web, iOS, Android, or Flutter) Step 3: Enable desired authentication providers Step 4: Download and configure SDK credentials

Web SDK Initialization

import { initializeApp } from 'firebase/app';
import { getAuth, onAuthStateChanged } from 'firebase/auth';

const firebaseConfig = {
  apiKey: "your-api-key",
  authDomain: "your-project.firebaseapp.com",
  projectId: "your-project-id"
};

const app = initializeApp(firebaseConfig);
const auth = getAuth(app);

onAuthStateChanged(auth, (user) => {
  if (user) {
    console.log('Signed in:', user.uid);
  } else {
    console.log('Signed out');
  }
});

Flutter SDK Initialization

import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_auth/firebase_auth.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

// Auth state listener
FirebaseAuth.instance.authStateChanges().listen((User? user) {
  if (user != null) {
    print('Signed in: ${user.uid}');
  }
});

Anonymous Authentication

import { signInAnonymously, linkWithCredential, EmailAuthProvider } from 'firebase/auth';

// Sign in anonymously
const result = await signInAnonymously(auth);
console.log('Anonymous UID:', result.user.uid);

// Upgrade to permanent account
const credential = EmailAuthProvider.credential(email, password);
await linkWithCredential(auth.currentUser, credential);

Session Persistence

import { setPersistence, browserLocalPersistence, browserSessionPersistence } from 'firebase/auth';

// Persist across browser sessions (default)
await setPersistence(auth, browserLocalPersistence);

// Clear on tab close
await setPersistence(auth, browserSessionPersistence);

Security Rules Integration

Firestore Rules

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
    match /admin/{document=**} {
      allow read, write: if request.auth.token.admin == true;
    }
  }
}

Storage Rules

rules_version = '2';
service firebase.storage {
  match /b/{bucket}/o {
    match /users/{userId}/{allPaths=**} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
  }
}

Advanced Patterns

For advanced implementation patterns, see:

• reference.md: MFA, session cookies, Cloud Functions triggers, Admin SDK setup
• examples.md: Complete authentication services, React hooks, Flutter providers

Resources

Extended Documentation:

• reference.md: Advanced patterns and configuration guides
• examples.md: Working code examples across platforms

Module Files:

• modules/social-auth.md: Social identity providers
• modules/phone-auth.md: Phone number authentication
• modules/custom-claims.md: Role-based access control

Firebase Official Resources:

• Firebase Console: console.firebase.google.com
• Authentication Documentation: firebase.google.com/docs/auth
• Security Rules Reference: firebase.google.com/docs/rules

Works Well With:

• moai-platform-firestore: Firestore database with auth-based security
• moai-lang-flutter: Flutter SDK for mobile Firebase Auth
• moai-lang-typescript: TypeScript patterns for Firebase SDK
• moai-domain-backend: Backend architecture with Firebase Admin SDK

Status: Production Ready Version: 2.0.0 (Modular Architecture) Last Updated: 2025-12-07 Provider Coverage: Firebase Authentication Only