How to fix auth/second-factor-required in Firebase

import { signInWithEmailAndPassword, getMultiFactorResolver } from "firebase/auth";
import { auth } from "./firebase-config";

try {
  await signInWithEmailAndPassword(auth, email, password);
  // User signed in successfully (no MFA required)
} catch (error) {
  if (error.code === "auth/multi-factor-auth-required") {
    // User has MFA enrolled - handle second factor
    const resolver = getMultiFactorResolver(auth, error);
    // Continue to next step
  } else {
    // Other authentication error
    console.error("Sign-in failed:", error.message);
  }
}

if (error.code === "auth/multi-factor-auth-required") {
  const resolver = getMultiFactorResolver(auth, error);

  // Get list of enrolled second factors
  const hints = resolver.hints;

  // Each hint contains information about a second factor
  hints.forEach((hint) => {
    if (hint.factorId === "phone") {
      console.log("SMS to:", hint.displayName); // Shows phone number like "+1 (555) 123-****"
    } else if (hint.factorId === "totp") {
      console.log("TOTP authenticator app");
    }
  });

  // Typically there will be one enrolled factor, but users can have multiple
}

const resolver = getMultiFactorResolver(auth, error);
const hints = resolver.hints;

// For a single SMS factor, automatically use it
const phoneHint = hints.find(h => h.factorId === "phone");

if (phoneHint) {
  // Send SMS code to the user's phone
  try {
    const phoneAuthProvider = new PhoneAuthProvider(auth);
    const verificationId = await phoneAuthProvider.verifyPhoneNumber(
      phoneHint.phoneNumber,
      window.recaptchaVerifier // or your RecaptchaVerifier instance
    );

    // Store verificationId for use in next step
    // Prompt user to enter SMS code they received
  } catch (error) {
    console.error("Failed to send SMS:", error);
  }
}

import {
  signInWithEmailAndPassword,
  getMultiFactorResolver,
  PhoneAuthProvider,
  PhoneMultiFactorGenerator,
  RecaptchaVerifier
} from "firebase/auth";

// After user enters SMS code
const smsCode = userEnteredCode; // "123456"
const verificationId = storedVerificationId; // From previous step

try {
  const resolver = getMultiFactorResolver(auth, error);

  // Create PhoneMultiFactorAssertion from the SMS code
  const phoneAssertion = PhoneMultiFactorGenerator.assertion(
    PhoneAuthProvider.credential(verificationId, smsCode)
  );

  // Complete sign-in with the second factor
  const result = await resolver.resolveSignIn(phoneAssertion);

  // User is now signed in
  console.log("Successfully signed in:", result.user.email);
} catch (error) {
  console.error("Invalid code or sign-in failed:", error);
}

import {
  getMultiFactorResolver,
  TOTPMultiFactorGenerator
} from "firebase/auth";

const resolver = getMultiFactorResolver(auth, error);
const totpHint = resolver.hints.find(h => h.factorId === "totp");

if (totpHint && userSelectedTOTP) {
  // User enters 6-digit code from their authenticator app
  const totpCode = userEnteredCode; // "123456"

  try {
    // Create TOTP assertion from the code
    const totpAssertion = TOTPMultiFactorGenerator.assertion(
      totpHint,
      totpCode
    );

    // Complete sign-in with TOTP
    const result = await resolver.resolveSignIn(totpAssertion);
    console.log("Signed in with TOTP:", result.user.email);
  } catch (error) {
    console.error("Invalid TOTP code:", error);
  }
}