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Authentification multifacteur (MFA)

Renforcez la sécurité en activant et en configurant l’authentification multifacteur pour vos utilisateurs Firebase

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Authentification multifacteur (MFA) est une leçon Firebase Auth & Realtime Database Apps gratuite sur CoddyKit. Ceci est la leçon 2 sur 4. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage Firebase Auth & Realtime Database Apps, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours Firebase Auth & Realtime Database Apps comprend 4 leçons au total.

Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.

Secure Your App with MFA

Multi-Factor Authentication (MFA) adds an extra layer of security to user accounts. Instead of just a password, users need a second "factor" to prove their identity.

This significantly reduces the risk of unauthorized access, even if a password is stolen.

Firebase MFA Overview

Firebase Authentication provides built-in support for MFA. It allows users to enroll multiple second factors, like a phone number for SMS verification.

When MFA is enabled, users first sign in with their primary method (e.g., email/password), then complete a challenge with one of their enrolled second factors.

Prerequisites for MFA

To enable MFA for a user, they must first be signed into your app. Firebase MFA works by associating additional factors with an existing user account.

  • User must be signed in.
  • Firebase SDK initialized.
  • You'll guide the user to enroll a second factor.

Adding a Phone Factor

A common second factor is a phone number, verified via SMS. This process involves:

  1. Sending a verification code to the user's phone.
  2. The user entering that code into your app.
  3. Firebase verifying the code and linking the phone number to the user's account.

Start Phone Enrollment

Here's how to initiate sending an SMS verification code to a user's phone number as an MFA factor. Remember to replace +16505551234 with the user's actual phone number.

import com.google.firebase.auth.*;
import com.google.firebase.FirebaseApp;
import java.util.concurrent.TimeUnit;

public class Main {
  public static void main(String[] args) {
    // Assume FirebaseApp is initialized and a user is signed in.
    // FirebaseAuth auth = FirebaseAuth.getInstance();
    // FirebaseUser user = auth.getCurrentUser(); // Must be non-null

    System.out.println("Simulating MFA phone enrollment initiation:");

    // Example PhoneAuthOptions (actual implementation requires Activity context)
    PhoneAuthOptions options = PhoneAuthOptions.newBuilder(FirebaseAuth.getInstance())
        .setPhoneNumber("+16505551234") // User's phone number
        .setTimeout(60L, TimeUnit.SECONDS)
        .setActivity(null) // Use 'this' for Activity context on Android
        .setCallbacks(new PhoneAuthProvider.OnVerificationStateChangedCallbacks() {
            @Override public void onVerificationCompleted(PhoneAuthCredential credential) { /* auto-verified */ }
            @Override public void onVerificationFailed(FirebaseException e) { System.err.println("Failed: " + e.getMessage()); }
            @Override public void onCodeSent(String verificationId, PhoneAuthProvider.ForceResendingToken token) {
                System.out.println("Code sent. Store verificationId: " + verificationId);
                // Prompt user for SMS code here.
            }
        }).build();

    // In a real app: PhoneAuthProvider.verifyPhoneNumber(options);
    System.out.println("SMS verification initiated (simulated).");
  }
}

Verify & Finalize Enrollment

Once the user receives the SMS code and enters it, you use the verificationId (from the previous step) and the code to create a PhoneAuthCredential, then enroll it as an MFA factor.

import com.google.firebase.auth.*;

public class Main {
  public static void main(String[] args) {
    // Assume FirebaseApp is initialized and a user is signed in.
    // FirebaseAuth auth = FirebaseAuth.getInstance();
    // FirebaseUser user = auth.getCurrentUser(); // Must be non-null

    String verificationId = "YOUR_VERIFICATION_ID"; // From onCodeSent callback
    String smsCode = "123456"; // User's input

    PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, smsCode);

    // Enroll the credential as an MFA factor
    // user.multiFactor.enroll(credential)
    //     .addOnCompleteListener(task -> {
    //         if (task.isSuccessful()) {
    //             System.out.println("MFA factor enrolled successfully!");
    //         } else {
    //             System.err.println("MFA factor enrollment failed: " + task.getException().getMessage());
    //         }
    //     });
    System.out.println("MFA enrollment code demonstrated. Actual enrollment is async.");
  }
}

Authenticating with MFA

When a user with MFA enabled tries to sign in, the initial sign-in (e.g., with email/password) might return a MultiFactorResolver. This resolver contains information about the available second factors.

Your app then prompts the user to select and verify one of their enrolled factors.

Respond to MFA Challenge

After a primary sign-in, if MFA is required, you'll get a MultiFactorResolver. You then use this to complete the sign-in with a second factor, such as a phone SMS code.

import com.google.firebase.auth.*;
import java.util.List;

public class Main {
  public static void main(String[] args) {
    // Assume FirebaseApp is initialized.
    // FirebaseAuth auth = FirebaseAuth.getInstance();

    // --- Scenario: After an initial sign-in attempt (e.g., email/password)
    // --- that requires MFA, you would receive a MultiFactorResolver.
    // --- This is a simplified demo.

    System.out.println("Simulating MFA sign-in challenge response:");

    // MultiFactorResolver resolver = ... (obtained from initial sign-in result)
    // For demonstration, let's mock a resolver context.
    // In a real app, you'd get this from a FirebaseAuthException.

    // Example of how you'd get enrolled factors from a resolver
    // List<MultiFactorInfo> factors = resolver.getFactors();
    // if (!factors.isEmpty()) {
    //     MultiFactorInfo selectedFactor = factors.get(0); // Choose one, e.g., phone
    //     if (selectedFactor.getFactorId().equals(PhoneMultiFactorGenerator.FACTOR_ID)) {
    //         // Initiate SMS verification for this factor
    //         // Then, get the SMS code from the user
    //         // String smsCode = "123456";
    //         // PhoneAuthCredential credential = PhoneAuthProvider.getCredential(verificationId, smsCode);
    //         // MultiFactorAssertion assertion = PhoneMultiFactorGenerator.getAssertion(credential);
    //
    //         // auth.signInWithMultiFactorCredential(resolver.resolveSignIn(assertion))
    //         //     .addOnCompleteListener(task -> {
    //         //         if (task.isSuccessful()) {
    //         //             System.out.println("Signed in successfully with MFA!");
    //         //         } else {
    //         //             System.err.println("MFA sign-in failed: " + task.getException().getMessage());
    //         //         }
    //         //     });
    //     }
    // }
    System.out.println("MFA sign-in challenge response simulated. See comments.");
  }
}

View & Unenroll Factors

Users can manage their enrolled MFA factors. This includes viewing a list of factors they've added and removing (unenrolling) factors they no longer wish to use.

This is crucial for user control and security, allowing them to revoke access for lost devices.

import com.google.firebase.auth.*;
import java.util.List;

public class Main {
  public static void main(String[] args) {
    // Assume FirebaseApp is initialized and a user is signed in.
    // FirebaseAuth auth = FirebaseAuth.getInstance();
    // FirebaseUser user = auth.getCurrentUser(); // Must be non-null

    if (user != null) {
      System.out.println("Managing MFA factors for user: " + user.getUid());

      // Get enrolled factors
      List<MultiFactorInfo> enrolledFactors = user.getMultiFactor().getEnrolledFactors();
      System.out.println("\nEnrolled factors:");
      if (enrolledFactors.isEmpty()) {
        System.out.println("  No MFA factors enrolled.");
      } else {
        for (MultiFactorInfo factor : enrolledFactors) {
          System.out.println("  - Factor ID: " + factor.getFactorId() + ", Display Name: " + factor.getDisplayName());
          // Example: unenroll the first factor
          // user.getMultiFactor().unenroll(factor)
          //     .addOnCompleteListener(task -> {
          //         if (task.isSuccessful()) {
          //             System.out.println("Factor unenrolled successfully: " + factor.getFactorId());
          //         } else {
          //             System.err.println("Failed to unenroll: " + task.getException().getMessage());
          //         }
          //     });
        }
      }
    } else {
      System.out.println("No user signed in to manage MFA factors.");
    }
  }
}

MFA Quick Check

Which of the following is NOT a typical step when a user with MFA enabled signs into a Firebase application?

MFA: Stronger Security

In this lesson, you learned how to enhance your application's security by implementing Firebase Multi-Factor Authentication (MFA).

  • We covered enrolling new MFA factors, specifically phone numbers.
  • We explored how to handle the MFA challenge during user sign-in.
  • You also saw how users can manage their enrolled factors.

MFA is a powerful tool to protect user accounts from unauthorized access.

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Cours
11
Leçons
44

Questions Fréquemment Posées

La leçon « Authentification multifacteur (MFA) » est-elle gratuite ?

Oui — le texte complet de « Authentification multifacteur (MFA) » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours Firebase Auth & Realtime Database Apps, passe à CoddyKit PRO. Le cours Firebase Auth & Realtime Database Apps comprend 4 leçons au total.

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Renforcez la sécurité en activant et en configurant l’authentification multifacteur pour vos utilisateurs Firebase Tu pratiques Firebase Auth & Realtime Database Apps avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.

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Toutes les leçons de ce cours

  1. Authentification par numéro de téléphone
  2. Authentification multifacteur (MFA)
  3. Attributs personnalisés et règles de sécurité
  4. Association de comptes et gestion des fournisseurs
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