# Two-Factor Authentication with Authy, Python and Flask

> \[!WARNING]
>
> As of November 2022, Twilio no longer provides support for Authy SMS/Voice-only customers. Customers who were also using Authy TOTP or Push prior to March 1, 2023 are still supported. The Authy API is now closed to new customers and will be fully deprecated in the future.
>
> For new development, we encourage you to use the [Verify v2 API](/docs/verify/api).
>
> Existing customers will not be impacted at this time until Authy API has reached End of Life. For more information about migration, see [Migrating from Authy to Verify for SMS](https://www.twilio.com/blog/migrate-authy-to-verify).

This [Flask](https://flask.palletsprojects.com/en/2.1.x/) sample application is an example of typical login flow. To run this sample app yourself, [download the code and follow the instructions on GitHub](https://github.com/TwilioDevEd/authy2fa-flask).

Adding two-factor authentication (2FA) to your web application increases the security of your user's data. [Multi-factor authentication](https://en.wikipedia.org/wiki/Multi-factor_authentication) determines the identity of a user by validating once by logging into the app, and then a second time with their mobile device using [Authy](https://www.twilio.com/en-us/trusted-activation/verify).

For the second factor, we will validate that the user has their mobile phone by either:

* Sending them a OneTouch push notification to their mobile Authy app or
* Sending them a token through their mobile Authy app or
* Sending them a one-time token in a text message sent with Authy via Twilio.

*[See how VMware uses Authy 2FA to secure their enterprise mobility management solution.](https://customers.twilio.com/1143/vmware/?utm_source=docs\&utm_campaign=docs_to_stories)*

## Configuring Authy

If you haven't already, now is the time to [sign up for Authy](https://dashboard.authy.com/signup). Create your first application, naming it whatever you wish. After you create your application, your production API key will be visible on your [dashboard](https://dashboard.authy.com):

Once we have an Authy API key, we store it in our `.env` file, which helps us set the environment variables for our app.

You'll also want to set a callback URL for your application in the OneTouch section of the Authy dashboard. See the project [README](https://github.com/TwilioDevEd/authy2fa-flask) for more details.

```bash title="Environment Variable Settings" description="authy2fa-flask/.env_example"
# Environment variables for authy2fa-flask

# Secret key (used for sessions)
SECRET_KEY=not-so-secret

# Authy API Key
# Found at https://dashboard.authy.com under your application
AUTHY_API_KEY=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

```

Now that we've configured our Flask app, let's take a look at how we register a user with Authy.

## Register a User with Authy

When a new user signs up for our website we call this helper function, which handles storing the user in the database as well as registering the user with Authy.

In order to get a user set up for your application you will need their *email*, *phone number* and *country code*. We have fields for each of these on our sign up form.

Once we register the user with Authy we can get the user's Authy id off the response. This is very important — it's how we will verify the identity of our user with Authy.

```py title="Create and Register a User with Authy" description="twofa/utils.py"
# !mark(12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32)
from authy.api import AuthyApiClient
from flask import current_app
from authy import AuthyApiException


def get_authy_client():
    """ Return a configured Authy client. """
    return AuthyApiClient(current_app.config['AUTHY_API_KEY'])


def create_user(form):
    """Creates an Authy user and then creates a database User"""
    client = get_authy_client()

    # Create a new Authy user with the data from our form
    authy_user = client.users.create(
        form.email.data, form.phone_number.data, form.country_code.data
    )

    # If the Authy user was created successfully, create a local User
    # with the same information + the Authy user's id
    if authy_user.ok():
        return form.create_user(authy_user.id)
    else:
        raise AuthyApiException('', '', authy_user.errors()['message'])


def send_authy_token_request(authy_user_id):
    """
    Sends a request to Authy to send a SMS verification code to a user's phone
    """
    client = get_authy_client()

    client.users.request_sms(authy_user_id)


def send_authy_one_touch_request(authy_user_id, email=None):
    """Initiates an Authy OneTouch request for a user"""
    client = get_authy_client()

    details = {}

    if email:
        details['Email'] = email

    response = client.one_touch.send_request(
        authy_user_id, 'Request to log in to Twilio demo app', details=details
    )

    if response.ok():
        return response.content


def verify_authy_token(authy_user_id, user_entered_code):
    """Verifies a user-entered token with Authy"""
    client = get_authy_client()

    return client.tokens.verify(authy_user_id, user_entered_code)


def authy_user_has_app(authy_user_id):
    """Verifies a user has the Authy app installed"""
    client = get_authy_client()
    authy_user = client.users.status(authy_user_id)
    try:
        return authy_user.content['status']['registered']
    except KeyError:
        return False

```

Next up, let's take a look at the login.

## Log in with Authy OneTouch

When a user attempts to log in to our website, we will ask them for a second form of identification. Let's take a look at OneTouch verification first.

OneTouch works like so:

* We attempt to send a *[OneTouch Approval Request](/docs/authy/api)* to the user
* If the user has OneTouch enabled, we will get a `success` message back
* The user hits *Approve* in their Authy app
* Authy makes a `POST` request to our app with an `approved` status
* We log the user in

```py title="Log in with Authy OneTouch" description="twofa/auth/views.py"
# !mark(29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57)
from authy import AuthyApiException
from flask import flash, jsonify, redirect, render_template, request, session, url_for

from . import auth
from .forms import LoginForm, SignUpForm, VerifyForm
from ..database import db
from ..decorators import login_required, verify_authy_request
from ..models import User
from ..utils import create_user, send_authy_token_request, verify_authy_token


@auth.route('/sign-up', methods=['GET', 'POST'])
def sign_up():
    """Powers the new user form"""
    form = SignUpForm(request.form)

    if form.validate_on_submit():
        try:
            user = create_user(form)
            session['user_id'] = user.id

            return redirect(url_for('main.account'))

        except AuthyApiException as e:
            form.errors['Authy API'] = [
                'There was an error creating the Authy user',
                e.msg,
            ]

    return render_template('signup.html', form=form)


@auth.route('/login', methods=['GET', 'POST'])
def log_in():
    """
    Powers the main login form.

    - GET requests render the username / password form
    - POST requests process the form data via an AJAX request triggered in the
      user's browser
    """
    form = LoginForm(request.form)

    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user is not None and user.verify_password(form.password.data):
            session['user_id'] = user.id

            if user.has_authy_app:
                # Send a request to verify this user's login with OneTouch
                one_touch_response = user.send_one_touch_request()
                return jsonify(one_touch_response)
            else:
                return jsonify({'success': False})
        else:
            # The username and password weren't valid
            form.email.errors.append(
                'The username and password combination you entered are invalid'
            )

    if request.method == 'POST':
        # This was an AJAX request, and we should return any errors as JSON
        return jsonify(
            {'error': render_template('_login_error.html', form=form)}
        )  # noqa: E501
    else:
        return render_template('login.html', form=form)


@auth.route('/authy/callback', methods=['POST'])
@verify_authy_request
def authy_callback():
    """Authy uses this endpoint to tell us the result of a OneTouch request"""
    authy_id = request.json.get('authy_id')
    # When you're configuring your Endpoint/URL under OneTouch settings '1234'
    # is the preset 'authy_id'
    if authy_id != 1234:
        user = User.query.filter_by(authy_id=authy_id).one()

        if not user:
            return ('', 404)

        user.authy_status = request.json.get('status')
        db.session.add(user)
        db.session.commit()

    return ('', 200)


@auth.route('/login/status')
def login_status():
    """
    Used by AJAX requests to check the OneTouch verification status of a user
    """
    user = User.query.get(session['user_id'])
    return user.authy_status


@auth.route('/verify', methods=['GET', 'POST'])
@login_required
def verify():
    """Powers token validation (not using OneTouch)"""
    form = VerifyForm(request.form)
    user = User.query.get(session['user_id'])

    # Send a token to our user when they GET this page
    if request.method == 'GET':
        send_authy_token_request(user.authy_id)

    if form.validate_on_submit():
        user_entered_code = form.verification_code.data

        verified = verify_authy_token(user.authy_id, str(user_entered_code))
        if verified.ok():
            user.authy_status = 'approved'
            db.session.add(user)
            db.session.commit()

            flash(
                "You're logged in! Thanks for using two factor verification.", 'success'
            )  # noqa: E501
            return redirect(url_for('main.account'))
        else:
            form.errors['verification_code'] = ['Code invalid - please try again.']

    return render_template('verify.html', form=form)


@auth.route('/resend', methods=['POST'])
@login_required
def resend():
    """Resends a verification token to a user"""
    user = User.query.get(session.get('user_id'))
    send_authy_token_request(user.authy_id)
    flash('I just re-sent your verification code - enter it below.', 'info')
    return redirect(url_for('auth.verify'))


@auth.route('/logout')
def log_out():
    """Log out a user, clearing their session variables"""
    user_id = session.pop('user_id', None)
    user = User.query.get(user_id)
    user.authy_status = 'unverified'
    db.session.add(user)
    db.session.commit()

    flash("You're now logged out! Thanks for visiting.", 'info')
    return redirect(url_for('main.home'))
```

## Send the OneTouch Request

When our user logs in we immediately attempt to verify their identity with OneTouch. We will fall back gracefully if they don't have a OneTouch device, but we don't know until we try.

Authy lets us pass extra details with our OneTouch request including a message, a logo, and any other details we want to send. We could send any number of details by appending `details[some_detail]` to our `POST` request. You could imagine a scenario where we send a OneTouch request to approve a money transfer:

```py
data = {
    'api_key': client.api_key,
    'message': "Request to send money to Jarod's vault",
    'details[Request From]': 'Jarod',
    'details[Amount Requested]': '1,000,000',
    'details[Currency]': 'Galleons'
}
```

```py title="Send the OneTouch Request" description="twofa/models.py"
from werkzeug.security import generate_password_hash, check_password_hash

from . import db
from .utils import authy_user_has_app, send_authy_one_touch_request


class User(db.Model):
    """
    Represents a single user in the system.
    """

    __tablename__ = 'users'

    AUTHY_STATUSES = ('unverified', 'onetouch', 'sms', 'token', 'approved', 'denied')

    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(64), unique=True, index=True)
    password_hash = db.Column(db.String(128))
    full_name = db.Column(db.String(256))
    country_code = db.Column(db.Integer)
    phone = db.Column(db.String(30))
    authy_id = db.Column(db.Integer)
    authy_status = db.Column(db.Enum(*AUTHY_STATUSES, name='authy_statuses'))

    def __init__(
        self,
        email,
        password,
        full_name,
        country_code,
        phone,
        authy_id,
        authy_status='approved',
    ):
        self.email = email
        self.password = password
        self.full_name = full_name
        self.country_code = country_code
        self.phone = phone
        self.authy_id = authy_id
        self.authy_status = authy_status

    def __repr__(self):
        return '<User %r>' % self.email

    @property
    def password(self):
        raise AttributeError('password is not readable')

    @property
    def has_authy_app(self):
        return authy_user_has_app(self.authy_id)

    @password.setter
    def password(self, password):
        self.password_hash = generate_password_hash(password)

    def verify_password(self, password):
        return check_password_hash(self.password_hash, password)

    def send_one_touch_request(self):
        return send_authy_one_touch_request(self.authy_id, self.email)
```

Once we send the request we update our user's `authy_status` based on the response. This lets us know which method Authy will try first to verify this request with our user. But first we have to register a OneTouch callback endpoint.

## Configure the OneTouch callback

In order for our app to know what the user did after we sent the OneTouch request, we need to register a callback endpoint with Authy.

**Note:** In order to verify that the request is coming from Authy we've written a decorator, [`@verify_authy_request,`](https://github.com/TwilioDevEd/authy2fa-flask/blob/f5d27375358b69485385e6fb4da5759faa132634/twofa/decorators.py#L78-L114) that will halt the request if we cannot verify that it actually came from Authy\*.\*

Here in our callback, we look up the user using the `authy_id` sent with the Authy `POST` request. In a production application we might use a websocket to let our client know that we received a response from Authy. For this version, we update the `authy_status` on the user. Our client-side code will check that field before completing the login.

```py title="Update user status using Authy Callback" description="twofa/auth/views.py"
# !mark(59,60,61,62,63,64,65,66,67,68,69,70,71,72,73)
from authy import AuthyApiException
from flask import flash, jsonify, redirect, render_template, request, session, url_for

from . import auth
from .forms import LoginForm, SignUpForm, VerifyForm
from ..database import db
from ..decorators import login_required, verify_authy_request
from ..models import User
from ..utils import create_user, send_authy_token_request, verify_authy_token


@auth.route('/sign-up', methods=['GET', 'POST'])
def sign_up():
    """Powers the new user form"""
    form = SignUpForm(request.form)

    if form.validate_on_submit():
        try:
            user = create_user(form)
            session['user_id'] = user.id

            return redirect(url_for('main.account'))

        except AuthyApiException as e:
            form.errors['Authy API'] = [
                'There was an error creating the Authy user',
                e.msg,
            ]

    return render_template('signup.html', form=form)


@auth.route('/login', methods=['GET', 'POST'])
def log_in():
    """
    Powers the main login form.

    - GET requests render the username / password form
    - POST requests process the form data via an AJAX request triggered in the
      user's browser
    """
    form = LoginForm(request.form)

    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user is not None and user.verify_password(form.password.data):
            session['user_id'] = user.id

            if user.has_authy_app:
                # Send a request to verify this user's login with OneTouch
                one_touch_response = user.send_one_touch_request()
                return jsonify(one_touch_response)
            else:
                return jsonify({'success': False})
        else:
            # The username and password weren't valid
            form.email.errors.append(
                'The username and password combination you entered are invalid'
            )

    if request.method == 'POST':
        # This was an AJAX request, and we should return any errors as JSON
        return jsonify(
            {'error': render_template('_login_error.html', form=form)}
        )  # noqa: E501
    else:
        return render_template('login.html', form=form)


@auth.route('/authy/callback', methods=['POST'])
@verify_authy_request
def authy_callback():
    """Authy uses this endpoint to tell us the result of a OneTouch request"""
    authy_id = request.json.get('authy_id')
    # When you're configuring your Endpoint/URL under OneTouch settings '1234'
    # is the preset 'authy_id'
    if authy_id != 1234:
        user = User.query.filter_by(authy_id=authy_id).one()

        if not user:
            return ('', 404)

        user.authy_status = request.json.get('status')
        db.session.add(user)
        db.session.commit()

    return ('', 200)


@auth.route('/login/status')
def login_status():
    """
    Used by AJAX requests to check the OneTouch verification status of a user
    """
    user = User.query.get(session['user_id'])
    return user.authy_status


@auth.route('/verify', methods=['GET', 'POST'])
@login_required
def verify():
    """Powers token validation (not using OneTouch)"""
    form = VerifyForm(request.form)
    user = User.query.get(session['user_id'])

    # Send a token to our user when they GET this page
    if request.method == 'GET':
        send_authy_token_request(user.authy_id)

    if form.validate_on_submit():
        user_entered_code = form.verification_code.data

        verified = verify_authy_token(user.authy_id, str(user_entered_code))
        if verified.ok():
            user.authy_status = 'approved'
            db.session.add(user)
            db.session.commit()

            flash(
                "You're logged in! Thanks for using two factor verification.", 'success'
            )  # noqa: E501
            return redirect(url_for('main.account'))
        else:
            form.errors['verification_code'] = ['Code invalid - please try again.']

    return render_template('verify.html', form=form)


@auth.route('/resend', methods=['POST'])
@login_required
def resend():
    """Resends a verification token to a user"""
    user = User.query.get(session.get('user_id'))
    send_authy_token_request(user.authy_id)
    flash('I just re-sent your verification code - enter it below.', 'info')
    return redirect(url_for('auth.verify'))


@auth.route('/logout')
def log_out():
    """Log out a user, clearing their session variables"""
    user_id = session.pop('user_id', None)
    user = User.query.get(user_id)
    user.authy_status = 'unverified'
    db.session.add(user)
    db.session.commit()

    flash("You're now logged out! Thanks for visiting.", 'info')
    return redirect(url_for('main.home'))

```

Let's take a look at that client-side code now.

## Disabling Unsuccessful Callbacks

**Scenario:** The OneTouch callback URL provided by you is no longer active.

**Action:** We will disable the OneTouch callback after 3 consecutive HTTP error responses. We will also

* Set the OneTouch callback URL to blank.
* Send an email notifying you that the OneTouch callback is disabled with details on how to enable the OneTouch callback.

**How to enable OneTouch callback?** You need to update the OneTouch callback endpoint, which will allow the OneTouch callback.

Visit the Twilio Console: Console > Authy > Applications > \{ApplicationName} > Push Authentication > Webhooks > Endpoint/URL to update the Endpoint/URL with a valid OneTouch callback URL.

## Handle Two-Factor **Asynchronously**

In order for two-factor authentication to be seamless, it is best done asynchronously so that the user doesn't even know it's happening.

We've already taken a look at what's happening on the server side, so let's step in front of the cameras now and see how our JavaScript is interacting with those server endpoints.

First we hijack the login form submit and pass the data to our `sessions/create` controller using Ajax. Depending on how that endpoint responds, we will either wait for a OneTouch response or ask the user to enter a token.

If we expect a OneTouch response, we will begin polling `/login/status` until we see the OneTouch login was either approved or denied.

```js title="Handle Two-Factor Asynchronously" description="twofa/static/js/sessions.js"
$(document).ready(function() {

  $('#login-form').submit(function(e) {
    e.preventDefault();
    const formData = $(e.currentTarget).serialize();
    attemptOneTouchVerification(formData);
  });

  const attemptOneTouchVerification = function(form) {
    $.post( "/login", form, function(data) {
      $('.form-errors').remove();
      // Check first if we successfully authenticated the username and password
      if (data.hasOwnProperty('error')) {
        $('#login-form').prepend(data.error);
        return;
      }

      if (data.success) {
        $('#authy-modal').modal({backdrop:'static'},'show');
        $('.auth-ot').fadeIn();
        checkForOneTouch();
      } else {
        redirectToTokenForm();
      }
    });
  };

  const checkForOneTouch = function() {
    $.get( "/login/status", function(data) {

      if (data === 'approved') {
        window.location.href = "/account";
      } else if (data === 'denied') {
        redirectToTokenForm();
      } else {
        setTimeout(checkForOneTouch, 2000);
      }
    });
  };

  const redirectToTokenForm = function() {
    window.location.href = "/verify";
  };
});

```

Now let's see how to handle the case where we receive a denied OneTouch response.

## Fall back to a Token

This is the endpoint that our JavaScript is polling. It is waiting for the user's `authy_status` to be either `approved` or `denied`. If the user approves the OneTouch request, our JavaScript code from the previous step will redirect their browser to their account screen.

If the OneTouch request was denied, we will ask the user to log in with a token instead.

```py title="Handle Login Status" description="twofa/auth/views.py"
# !mark(75,76,77,78,79,80,81)
from authy import AuthyApiException
from flask import flash, jsonify, redirect, render_template, request, session, url_for

from . import auth
from .forms import LoginForm, SignUpForm, VerifyForm
from ..database import db
from ..decorators import login_required, verify_authy_request
from ..models import User
from ..utils import create_user, send_authy_token_request, verify_authy_token


@auth.route('/sign-up', methods=['GET', 'POST'])
def sign_up():
    """Powers the new user form"""
    form = SignUpForm(request.form)

    if form.validate_on_submit():
        try:
            user = create_user(form)
            session['user_id'] = user.id

            return redirect(url_for('main.account'))

        except AuthyApiException as e:
            form.errors['Authy API'] = [
                'There was an error creating the Authy user',
                e.msg,
            ]

    return render_template('signup.html', form=form)


@auth.route('/login', methods=['GET', 'POST'])
def log_in():
    """
    Powers the main login form.

    - GET requests render the username / password form
    - POST requests process the form data via an AJAX request triggered in the
      user's browser
    """
    form = LoginForm(request.form)

    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user is not None and user.verify_password(form.password.data):
            session['user_id'] = user.id

            if user.has_authy_app:
                # Send a request to verify this user's login with OneTouch
                one_touch_response = user.send_one_touch_request()
                return jsonify(one_touch_response)
            else:
                return jsonify({'success': False})
        else:
            # The username and password weren't valid
            form.email.errors.append(
                'The username and password combination you entered are invalid'
            )

    if request.method == 'POST':
        # This was an AJAX request, and we should return any errors as JSON
        return jsonify(
            {'error': render_template('_login_error.html', form=form)}
        )  # noqa: E501
    else:
        return render_template('login.html', form=form)


@auth.route('/authy/callback', methods=['POST'])
@verify_authy_request
def authy_callback():
    """Authy uses this endpoint to tell us the result of a OneTouch request"""
    authy_id = request.json.get('authy_id')
    # When you're configuring your Endpoint/URL under OneTouch settings '1234'
    # is the preset 'authy_id'
    if authy_id != 1234:
        user = User.query.filter_by(authy_id=authy_id).one()

        if not user:
            return ('', 404)

        user.authy_status = request.json.get('status')
        db.session.add(user)
        db.session.commit()

    return ('', 200)


@auth.route('/login/status')
def login_status():
    """
    Used by AJAX requests to check the OneTouch verification status of a user
    """
    user = User.query.get(session['user_id'])
    return user.authy_status


@auth.route('/verify', methods=['GET', 'POST'])
@login_required
def verify():
    """Powers token validation (not using OneTouch)"""
    form = VerifyForm(request.form)
    user = User.query.get(session['user_id'])

    # Send a token to our user when they GET this page
    if request.method == 'GET':
        send_authy_token_request(user.authy_id)

    if form.validate_on_submit():
        user_entered_code = form.verification_code.data

        verified = verify_authy_token(user.authy_id, str(user_entered_code))
        if verified.ok():
            user.authy_status = 'approved'
            db.session.add(user)
            db.session.commit()

            flash(
                "You're logged in! Thanks for using two factor verification.", 'success'
            )  # noqa: E501
            return redirect(url_for('main.account'))
        else:
            form.errors['verification_code'] = ['Code invalid - please try again.']

    return render_template('verify.html', form=form)


@auth.route('/resend', methods=['POST'])
@login_required
def resend():
    """Resends a verification token to a user"""
    user = User.query.get(session.get('user_id'))
    send_authy_token_request(user.authy_id)
    flash('I just re-sent your verification code - enter it below.', 'info')
    return redirect(url_for('auth.verify'))


@auth.route('/logout')
def log_out():
    """Log out a user, clearing their session variables"""
    user_id = session.pop('user_id', None)
    user = User.query.get(user_id)
    user.authy_status = 'unverified'
    db.session.add(user)
    db.session.commit()

    flash("You're now logged out! Thanks for visiting.", 'info')
    return redirect(url_for('main.home'))

```

Now let's see how to send a token to the user.

## Send a Token

This view is responsible for sending the token and then validating the code that our user enters.

In the case where our user already has the Authy app but is not enabled for OneTouch, this same method will trigger a push notification that will be sent to their phone with a code inside the Authy app.

The user will see a verification form.

A `POST` request to this view validates the code our user enters. First, we grab the `User` model by the ID we stored in the session. Next, we use the Authy API to validate the code our user entered against the one Authy sent them.

If the two match, our login process is complete! We mark the user's `authy_status` as `approved` and thank them for using two-factor authentication.

```py title="Verify users via Authy Token" description="twofa/auth/views.py"
# !mark(100,101,102,103,104,105,106,107,108,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99)
from authy import AuthyApiException
from flask import flash, jsonify, redirect, render_template, request, session, url_for

from . import auth
from .forms import LoginForm, SignUpForm, VerifyForm
from ..database import db
from ..decorators import login_required, verify_authy_request
from ..models import User
from ..utils import create_user, send_authy_token_request, verify_authy_token


@auth.route('/sign-up', methods=['GET', 'POST'])
def sign_up():
    """Powers the new user form"""
    form = SignUpForm(request.form)

    if form.validate_on_submit():
        try:
            user = create_user(form)
            session['user_id'] = user.id

            return redirect(url_for('main.account'))

        except AuthyApiException as e:
            form.errors['Authy API'] = [
                'There was an error creating the Authy user',
                e.msg,
            ]

    return render_template('signup.html', form=form)


@auth.route('/login', methods=['GET', 'POST'])
def log_in():
    """
    Powers the main login form.

    - GET requests render the username / password form
    - POST requests process the form data via an AJAX request triggered in the
      user's browser
    """
    form = LoginForm(request.form)

    if form.validate_on_submit():
        user = User.query.filter_by(email=form.email.data).first()
        if user is not None and user.verify_password(form.password.data):
            session['user_id'] = user.id

            if user.has_authy_app:
                # Send a request to verify this user's login with OneTouch
                one_touch_response = user.send_one_touch_request()
                return jsonify(one_touch_response)
            else:
                return jsonify({'success': False})
        else:
            # The username and password weren't valid
            form.email.errors.append(
                'The username and password combination you entered are invalid'
            )

    if request.method == 'POST':
        # This was an AJAX request, and we should return any errors as JSON
        return jsonify(
            {'error': render_template('_login_error.html', form=form)}
        )  # noqa: E501
    else:
        return render_template('login.html', form=form)


@auth.route('/authy/callback', methods=['POST'])
@verify_authy_request
def authy_callback():
    """Authy uses this endpoint to tell us the result of a OneTouch request"""
    authy_id = request.json.get('authy_id')
    # When you're configuring your Endpoint/URL under OneTouch settings '1234'
    # is the preset 'authy_id'
    if authy_id != 1234:
        user = User.query.filter_by(authy_id=authy_id).one()

        if not user:
            return ('', 404)

        user.authy_status = request.json.get('status')
        db.session.add(user)
        db.session.commit()

    return ('', 200)


@auth.route('/login/status')
def login_status():
    """
    Used by AJAX requests to check the OneTouch verification status of a user
    """
    user = User.query.get(session['user_id'])
    return user.authy_status


@auth.route('/verify', methods=['GET', 'POST'])
@login_required
def verify():
    """Powers token validation (not using OneTouch)"""
    form = VerifyForm(request.form)
    user = User.query.get(session['user_id'])

    # Send a token to our user when they GET this page
    if request.method == 'GET':
        send_authy_token_request(user.authy_id)

    if form.validate_on_submit():
        user_entered_code = form.verification_code.data

        verified = verify_authy_token(user.authy_id, str(user_entered_code))
        if verified.ok():
            user.authy_status = 'approved'
            db.session.add(user)
            db.session.commit()

            flash(
                "You're logged in! Thanks for using two factor verification.", 'success'
            )  # noqa: E501
            return redirect(url_for('main.account'))
        else:
            form.errors['verification_code'] = ['Code invalid - please try again.']

    return render_template('verify.html', form=form)


@auth.route('/resend', methods=['POST'])
@login_required
def resend():
    """Resends a verification token to a user"""
    user = User.query.get(session.get('user_id'))
    send_authy_token_request(user.authy_id)
    flash('I just re-sent your verification code - enter it below.', 'info')
    return redirect(url_for('auth.verify'))


@auth.route('/logout')
def log_out():
    """Log out a user, clearing their session variables"""
    user_id = session.pop('user_id', None)
    user = User.query.get(user_id)
    user.authy_status = 'unverified'
    db.session.add(user)
    db.session.commit()

    flash("You're now logged out! Thanks for visiting.", 'info')
    return redirect(url_for('main.home'))

```

That's it! We've just implemented two-factor auth using three different methods and the latest in Authy technology.

## Where to next?

If you're a Python developer working with Twilio, you might enjoy these other tutorials:

**[SMS and MMS Notifications](/blog/server-notifications-python-django)**

Faster than email and less likely to get blocked, text messages are great for timely alerts and notifications. Learn how to send out SMS (and MMS) notifications to a list of server administrators.

**[Call Tracking](/blog/call-tracking-python-django)**

Call Tracking helps you measure the effectiveness of different marketing campaigns. By assigning a unique phone number to different advertisements, you can track which ones have the best call rates and get some data about the callers themselves.