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Implementing MFA with custom UIs ​

TIP

By default, Privy's wallet MFA feature will use Privy's UIs for enrolling users in MFA, managing MFA methods, and having users complete MFA to authorize signatures and transactions for the embedded wallet.


This guide is intended only for apps that would like to use wallet MFA with their own custom UIs, instead of Privy's defaults.

If you'd like to implement wallet MFA in your application using your own UIs, follow this guide. At a high-level, your app must set up two core user flows:

  1. Enrolling in MFA, with the user's desired authentication method(s)
  2. Completing MFA, when it is required by the embedded wallet

WARNING

Implementing wallet MFA with custom UIs is substantially more involved than integrating Privy's out-of-the-box wallet MFA feature. Make sure to consider the development trade-offs of using custom UIs over Privy defaults before finalizing on your approach!

Configuring MFA to be used with custom UIs ​

If you plan to use your own custom UIs for wallet MFA, set the mfa.noPromptOnMfaRequired property of the PrivyProvider to true.

tsx
function MyApp({Component, pageProps}: AppProps) {
  return (
    <>
      <PrivyProvider
        appId={process.env.NEXT_PUBLIC_PRIVY_APP_ID}
        config={{
          mfa: {
            // Defaults to 'false'
            noPromptOnMfaRequired: true,
          },
          ...insertTheRestOfYourConfig,
        }}
      >
        <Component {...pageProps} />
      </PrivyProvider>
    </>
  );
}

This will configure Privy to not show its default UIs for wallet MFA, and instead rely on your custom implementation (outlined below).

Enrolling in MFA ​

To enroll your users in MFA, use the useMfaEnrollment hook from Privy. Currently, users can enroll in two MFA methods:

  • SMS, where users authenticate with a 6-digit MFA code sent to their phone number
  • TOTP, where users authenticate with a 6-digit MFA code from an authentication app, like Authy or Google Authenticator

Follow the specific instructions below based on which method you'd like your user to enroll in!

SMS ​

To enroll your users in MFA with SMS, use the initEnrollmentWithSms and submitEnrollmentWithSms methods returned by the useMfaEnrollment hook:

tsx
const {initEnrollmentWithSms, submitEnrollmentWithSms} = useMfaEnrollment();

First, initiate enrollment by prompting your user to enter the phone number they'd like to use for MFA. Then, call Privy's initEnrollmentWithSms method. As a parameter to this initEnrollmentWithSms, pass a JSON object with a phoneNumber field that contains the user's provide phone number as a string.

tsx
// Prompt the user for their phone number
const phoneNumberInput = 'insert-phone-number-from-user';
// Send an enrollment code to their phone number
await initEnrollmentWithSms({phoneNumber: phoneNumberInput});

Once initEnrollmentWithSms is called with a valid phoneNumber, Privy will then send a 6-digit MFA enrollment code to the provided number. This method returns a Promise that will resolve to void if the code was successfully sent, or will reject with an error if there was an error sending the code (e.g. invalid phone number).

Next, prompt the user to enter the 6-digit code that was sent to their phone number, and use the submitEnrollmentWithSms method to complete enrollment of that phone number. As a parameter to submitEnrollmentWithSms, you must pass a JSON object with both the original phoneNumber that the user enrolled, and the mfaCode they received at that number.

tsx
// Prompt the user for the code sent to their phone number
const mfaCodeInput = 'insert-mfa-code-received-by-user';
await submitEnrollmentWithSms({
  phoneNumber: phoneNumberInput, // From above
  mfaCode: mfaCodeInput,
});

This method returns a Promise that will resolve to void if the provided code is correct and the user has successfully enrolled this phone number in MFA, or will reject with an error if there was an error. See the Handling errors with code submission section of this guide for how to best handle possible errors.

See an end-to-end example of enrolling users in MFA with SMS 👇

The component below serves as a reference implementation for how to enroll your users in MFA with SMS!

tsx
import {useMfaEnrollment} from '@privy-io/react-auth';

export default function MfaEnrollmentWithSms() {
  const {initEnrollmentWithSms, submitEnrollmentWithSms} = useMfaEnrollment();

  const [phoneNumber, setPhoneNumber] = useState<string | null>(null);
  const [mfaCode, setMfaCode] = useState<string | null>(null);
  const [pendingMfaCode, setPendingMfaCode] = useState<boolean>(false);

  // Handler for when the user enters their phone number to enroll in MFA.
  const onEnteredPhoneNumber = () => {
    await initEnrollmentWithSms({phoneNumber: phoneNumber}); // Sends an MFA code to the `phoneNumber`
    setPendingMfaCode(true);
  }

  // Handler for when the user enters the MFA code sent to their phone number.
  const onEnteredMfaCode = () => {
    await submitEnrollmentWithSms({phoneNumber: phoneNumber, mfaCode: mfaCode});
    // See the "Handling errors with code submission" section of this guide
    // for details on how to handle errors raised by `submitEnrollmentWithSms`
    setPendingMfaCode(false);
  }

  // If no MFA code has been sent yet, prompt the user for their phone number to enroll
  if (!pendingMfaCode) {
    // Input field for the user to enter the phone number they'd like to enroll for MFA
    return <>
      <input placeholder='(555) 555 5555' onChange={(event) => setPhoneNumber(event.target.value)}/>
      <button onClick={onEnteredPhoneNumber}>Enroll a Phone with MFA</button>
    </>;
  }

  // Input field for the user to enter the MFA code sent to their phone number
  return <>
    <input placeholder='123456' onChange={(event) => setMfaCode(event.target.value)}/>
    <button onClick={onEnteredMfaCode}>Submit Enrollment Code</button>
  </>;
}

INFO

If your app has enabled SMS as a possible login method, users will not be able to enroll SMS as a valid MFA method.

SMS must be either be used as a login method to secure user accounts, or as an MFA method for additional security on the users' wallets.

TOTP ​

To enroll your users in MFA with TOTP, use the initEnrollmentWithTotp and submitEnrollmentWithTotp methods returned by the useMfaEnrollment hook:

tsx
const {initEnrollmentWithTotp, submitEnrollmentWithTotp} = useMfaEnrollment();

First, initiate enrollment by calling Privy's initEnrollmentWithTotp method with no parameters. This method returns a Promise for an authUrl and secret that the user will need in order to complete enrollment.

tsx
const {authUrl, secret} = await initEnrollmentWithTotp();

Then, to have the user enroll, you can either:

  • display the TOTP authUrl as a QR code to the user, and prompt them to scan it with their TOTP client (commonly, a mobile app like Google Authenticator or Authy)
  • allow the user to copy the TOTP secret and paste it into their TOTP client

TIP

You can directly pass in the authUrl from above into a library like react-qr-code to render the URL as a QR code to your user.

Once your user has successfully scanned the QR code, an enrollment code for Privy will appear within their TOTP client. Prompt the user to enter this code in your app, and call Privy's submitEnrollmentWithTotp method. As a parameter to submitEnrollmentWithTotp, pass a JSON object with an mfaCode field that contains the MFA code from the user as a string.

tsx
const mfaCodeInput = 'insert-mfa-code-from-user-totp-app'; // Prompt the user for the code in their TOTP app
await submitEnrollmentWithTotp({mfaCode: mfaCodeInput});

This method returns a Promise that will resolve to void if the entered mfaCode was correct, and will reject with an error otherwise. See the Handling errors with code submission section of this guide for how to best handle possible errors.

See an end-to-end example of enrolling users in MFA with TOTP 👇

The component below serves as a reference implementation for how to enroll your users in MFA with TOTP!

tsx
import {useMfaEnrollment} from '@privy-io/react-auth';
import QRCode from 'react-qr-code';
import {CopyableElement} from '../components/CopyableElement';

export default function MfaEnrollmentWithTotp() {
  const {initEnrollmentWithTotp, submitEnrollmentWithTotp} = useMfaEnrollment();
  const [totpAuthUrl, setTotpAuthUrl] = useState<string | null>(null);
  const [totpSecret, setTotpSecret] = useState<string | null>(null);
  const [mfaCode, setMfaCode] = useState<string | null>(null);

  // Handler for when the user is ready to enroll in TOTP MFA
  const onGenerateTotpUrl = async () => {
    const {authUrl, secret} = await initEnrollmentWithTotp();
    setTotpAuthUrl(authUrl);
    setTotpSecret(secret);
  }

  // Handler for when the user enters the MFA code from their TOTP client
  const onEnteredMfaCode = async () => {
    await submitEnrollmentWithTotp({mfaCode: mfaCode});
    // See the "Handling errors with code submission" section of this guide
    // for details on how to handle errors raised by `submitEnrollmentWithTotp`
  }

  return(
    <div>
      {/* QR code for the user to scan */}
      {totpAuthUrl && totpSecret ?
        {/* If TOTP values have been generated... */}
        <>
          {/* ...show the user a QR code with the `authUrl` that they can scan...  */}
          <QRCode value={totpAuthUrl} />
          {/* ...or give them the option to copy the `secret` into their TOTP client  */}
          <CopyableElement value={totpSecret} />
        </> :
        {/* Else, show a button to generate the totpAuthUrl */}
        <button onClick={() => onGenerateTotpUrl()}>Show QR Code</button>
      }
      {/* Input field for the user to enter their MFA code */}
      <p>Enter the code from your authenticator app below.</p>
      <input placeholder='123456' onChange={(event) => setMfaCode(event.target.value)}/>
      <button onClick={() => submitEnrollmentWithTotp({mfaCode: mfaCode})}>Submit Enrollment Code</button>
    </div>
  );
}

Enrolling multiple MFA methods ​

Privy allows users to register in multiple MFA methods (e.g. both SMS and TOTP) if they wish.

INFO

If a user already has one MFA method enabled, and wishes to enroll in another (or change their existing MFA method), Privy will require the user to complete MFA with their existing method in order to complete enrollment of the new, additional method.

To ensure your users can complete this flow if required, please make sure you have implemented the Completing MFA logic described below before allowing users to enroll in another MFA method.

This is the generic logic that allows Privy to invoke an MFA flow for your users whenever required (signatures, transactions, and in this case, enrolling a new MFA method). Thereafter, you should not need any other setup to allow users to enroll in additional MFA methods.

Unenrolling MFA methods ​

Privy also allows users to also delete MFA methods via the useMfaEnrollemnt hook. You can use the returned methods:

  • unenrollWithSms, to unenroll the user from SMS-based MFA
  • unenrollWithTotp, to uneroll the user from TOTP-based MFA

When invoked, unenrollment methods will require the user to first complete MFA verification, in order to confirm unenrollment. In kind, unenrolling MFA methods requires that you have implemented the Completing MFA logic described below.

These methods return a Promise that resolves to void if unenrollment was successful, or rejects with an error if there was an issue with unenrollment (e.g. user did not complete MFA verification, or user did not have that MFA method enrolled).

tsx
import {useMfaEnrollment} from '@privy-io/react-auth';

export default function MfaUnenrollment() {
  const {unenrollWithSms, unenrollWithTotp} = useMfaEnrollment();

  return (
    <div>
      <button onClick={unenrollWithSms}>Unenroll SMS</button>
      <button onClick={unenrollWithTotp}>Unenroll TOTP</button>
    </div>
  );
}

Completing MFA ​

Once users have successfully enrolled in MFA with Privy, they will be required to complete MFA whenever the private key for their embedded wallet must be used. This includes signing messages and transactions, recovering the embedded wallet on new devices, exporting the wallet's private key, and setting a password on the wallet.

To ensure users can complete MFA when required, your app must do the following:

  1. Set up a flow to guide the user through completing MFA when required.
  2. Register an event listener to configure Privy to invoke the flow from step (1) whenever MFA is required.

TIP

Once a user has completed MFA on a given device, they can continue to use the wallet on that device without needing to complete MFA for 15 minutes.

After 15 minutes have elapsed, Privy will require that the user complete MFA again to re-authorize use of the wallet's private key.

Guiding the user through MFA ​

To set up a flow to have the user complete MFA, use Privy's useMfa hook.

tsx
const {init, submit, cancel} = useMfa();

This flow has three core components

  1. Requesting an MFA code be sent to the user's MFA method (init)
  2. Submitting the MFA code provided by the user (submit)
  3. Cancelling an in-progress MFA flow (cancel)

Requesting an MFA code ​

To request an MFA code for the current user, call the init method from the useMfa hook, passing the user's desired MFA method ('sms' or 'totp') as a parameter.

tsx
const selectedMfaMethod = 'sms'; // Must be 'sms' or 'totp'
await init(selectedMfaMethod);

The init method will then send an MFA code to the desired MFA method, and returns a Promise that resolves to void if the code was successfully sent, and rejects with an error if there was an issue sending the code. If the MFA method is 'sms', the user will receive an SMS with their MFA code at the phone number they originally enrolled. If the MFA method is 'totp', the user will receive the MFA code within their authenticator app.

Submitting the MFA code ​

Once init has resolved successfully, prompt the user to get their MFA code from their MFA method and to enter it within your app. Then, call the submit method from useMfa. As parameters to submit, pass the MFA method being used ('sms' or 'totp') and the MFA code that the user entered.

tsx
const mfaCode = 'insert-mfa-code-from-user';
await submit(selectedMfaMethod, mfaCode);

When invoked, submit returns a Promise that resolves to void if the user has successfully completed MFA, or rejects with an error if there was an issue completing MFA. See the Handling errors with code submission section of this guide for how to best handle possible errors.

Cancelling the MFA flow ​

After init has been called and the corresponding submit call has not yet occurred, the user may cancel their in-progress MFA flow if they wish.

To cancel the current MFA flow, call the cancel method from the useMfa hook.

tsx
cancel();
See a recommended abstraction for guiding users to complete MFA 👇

To simplify the implementation, we recommend abstracting the logic above into a self-contained component that can be used whenever the user needs to complete an MFA flow.

For instance, you might write an MFAModal component that allows the user to (1) select their desired method of their enrolled MFA methods, (2) request an MFA code, and (3) submit the MFA code to Privy for verification. A sample implementation is below:

tsx
import Modal from 'react-modal';

import {
  useMfaEnrollment,
  errorIndicatesMfaVerificationFailed,
  errorIndicatesMfaMaAttempts,
  errorIndicatesMfaTimeout,
} from '@privy-io/react-auth';

type Props = {
  // List of available MFA methods that the user has enrolled in
  mfaMethods: ('sms' | 'totp')[];
  // Boolean indicator to determine whether or not the modal should be open
  isOpen: boolean;
  // Helper function to open/close the modal */
  setIsOpen: (isOpen: boolean) => void;
};

export const MFAModal = ({mfaMethods, isOpen, setIsOpen}: Props) => {
  const {init, submit, cancel} = useMfa();
  // Stores the user's selected MFA method
  const [selectedMethod, setSelectedMethod] = useState<'sms' | 'otp' | null>(null);
  // Stores the user's MFA code
  const [mfaCode, setMfaCode] = useState('');
  // Stores an error message to display
  const [error, setError] = useState('');

  // Helper function to request an MFA code for a given method
  const onMfaInit = async (method: 'sms' | 'totp') => {
    await init(method);
    setError('');
    setSelectedMethod(method);
  };

  // Helper function to submit an MFA code to Privy for verification
  const onMfaSubmit = async () => {
    try {
      await submit(selectedMethod, mfaCode);
      setSelectedMethod(null); // Clear the MFA flow once complete
      setIsOpen(false); // Close the modal
    } catch (e) {
      // Handling possible errors with MFA code submission. See the "Handling errors
      // with code submission" section of this guide for a more detailed explanation.
      if (errorIndicatesMfaVerificationFailed(e)) {
        setError('Incorrect MFA code, please try again.');
        // Allow the user to re-enter the code and call `submit` again
      } else if (errorIndicatesMfaMaxAttempts(e)) {
        setError('Maximum MFA attempts reached, please request a new code.');
        setSelectedMethod(null); // Clear the MFA flow to allow the user to trya gain
      } else if (errorIndicatesMfaTimeout(e)) {
        setError('MFA code has expired, please request a new code.');
        setSelectedMethod(null); // Clear the MFA flow to allow the user to try again
      }
    }
  };

  // Helper function to clean up state when the user closes the modal
  const onModalClose = () => {
    cancel(); // Cancel any in-progress MFA flows
    setIsOpen(false);
  };

  return (
    <Modal isOpen={isOpen} onAfterClose={onModalClose}>
      {/* Button for the user to select an MFA method and request an MFA code */}
      {mfaMethods.map((method) => (
        <button onClick={() => onMfaInit(method)}>Choose to MFA with {method}</button>
      ))}
      {/* Input field for the user to enter their MFA code and submit it */}
      {selectedMethod && (
        <div>
          <p>Enter your MFA code below</p>
          <input placeholder="123456" onChange={(event) => setMfaCode(event.target.value)} />
          <button onClick={() => onMfaSubmit()}>Submit Code</button>
        </div>
      )}
      {/* Display error message if there is one */}
      {!!error.length && <p>{error}</p>}
    </Modal>
  );
};

Notice how the modal contains all logic for requesting the MFA code, submitting the MFA code, handling errors, and cancelling an in-progress MFA code.

Then, when your app needs to prompt a user to complete MFA, they can simply display this MFAModal component and configure the mfaMethods prop with the list of MFA methods that are available for the current user.

Registering an event listener ​

Once you've set up your app's logic for guiding a user to complete MFA, you lastly need to configure Privy to invoke this logic whenever MFA is required by the user's embedded wallet.

To set up this configuration, use Privy's useRegisterMfaListener hook. As a parameter to useRegisterMfaListener, you must pass a JSON object with an onMfaRequired callback, described below.

onMfaRequired ​

Privy will invoke the onMfaRequired callback you set whenever the user is required to complete MFA to use the embedded wallet. When this occurs, any use of the embedded wallet will be "paused" until the user has successfully completed MFA with Privy.

In this callback, you should invoke your app's logic for guiding through completing MFA (done via the useMfa hook, as documented above). Within this callback, you can also access an mfaMethods parameter that contains a list of available MFA methods that the user has enrolled in ('sms' and/or 'totp').

Example registration ​

As an example, you might use the useRegisterMfaListener within a component like below. This example uses the MFAModal component implemented in the Prompting the user for MFA section of this guide.

INFO

In order for Privy to invoke your app's MFA flow, the component that calls Privy's useRegisterMfaListener hook must be mounted whenever the user's embedded wallet requires that they complete MFA.

In kind, we recommend that you render this component near the root of your application, so that it is always rendered whenever the embedded wallet may be used.

Optimistic MFA Verification ​

Once you've integrated MFA verification into your application, whenever MFA is required, the verify flow will be triggered. In some cases, for optimal user experience, you will want to prompt MFA verification before the onMfaRequired callback fires.

INFO

Consider the case of a user registering SMS as their second MFA method. The ideal flow here would be to prompt MFA verification via the existing TOTP flow before asking the user for the phone number.

To accomplish this, you can use the promptMfa method returned by the useMfa hook. This will trigger the onMfaRequired callback if and only if the user doesn't have an active MFA token that can be used for subsequent protected actions. By running this prior to a protected action, you can place the MFA verification flow at the ideal place.

tsx
const {initEnrollmentWithSms, submitEnrollmentWithSms} = useMfaEnrollment();
const {promptMfa} = useMfa();

// Prompt the user for MFA
await promptMfa();
// Prompt the user for their phone number
const phoneNumberInput = 'insert-phone-number-from-user';
// Send an enrollment code to their phone number
await initEnrollmentWithSms({phoneNumber: phoneNumberInput});

Handling errors with code submission ​

When both enrolling in and completing MFA, Privy sends a 6-digit code to the user's selected MFA method, that the user must submit to Privy in order to verify their identity. This is done via the following methods:

  • submitEnrollmentWithSms from the useMfaEnrollment hook (for enrollment in SMS MFA)
  • submitEnrollmentWithTotp from the useMfaEnrollment hook (for enrollment in TOTP MFA)
  • submit from the useMfa hook (for completing MFA with both SMS and TOTP)

When submitting this MFA code, Privy may respond with an error if the code is incorrect, if the user has reached the maximum number of attempts for this MFA flow, or if the MFA flow has timed out. If the user enters in an incorrect code (e.g. by mistyping), the user is allowed to retry code submission up to a maximum of four attempts.

To simplify handling errors with MFA code submission, Privy provides the following helper functions to parse errors raised by the MFA code submission methods listed above. Each of these functions accepts the raw error raised as a parameter, and returns a Boolean indicating if the error meets a certain condition:

  • errorIndicatesMfaVerificationFailed: indicates the user entered an incorrect MFA code
  • errorIndicatesMfaMaxAttempts indicates has reached the maximum number of attempts for this MFA flow, and that a new MFA code must be requested via init
  • errorIndicatesMfaTimeout indicates that the current MFA code has expired, and that a new MFA code must be requested via init

As an example, to handle errors raised by submit, you might use these helpers like so:

tsx
try {
  // Errors from `submitEnrollmentWithSms` and `submitEnrollmentWithTotp` can be handled similarly
  await submit('insert-mfa-code', 'insert-mfa-method');
} catch (e) {
  if (errorIndicatesMfaVerificationFailed(e)) {
    console.error('Incorrect MFA code, please try again.');
    // Allow the user to re-enter the code and call `submit` again
  } else if (errorIndicatesMfaMaxAttempts(e)) {
    console.error('Maximum MFA attempts reached, please request a new code.');
    // Allow the user to request a new code with `init`
  } else if (errorIndicatesMfaTimeout(e)) {
    console.error('MFA code has expired, please request a new code.');
    // Allow the user to request a new code with `init`
  }
}