How to build Mailgun Email passwordless sign-in with Python

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Logto is an Auth0 alternative designed for modern apps and SaaS products. It offers both Cloud and Open-source services to help you quickly launch your identity and management (IAM) system. Enjoy authentication, authorization, and multi-tenant management all in one.

We recommend starting with a free development tenant on Logto Cloud. This allows you to explore all the features easily.

In this article, we will go through the steps to quickly build the Mailgun sign-in experience (user authentication) with Python and Logto.

Prerequisites

A running Logto instance. Check out the introduction page to get started.
Basic knowledge of Python.
A usable Mailgun account.

Create an application in Logto

Logto is based on OpenID Connect (OIDC) authentication and OAuth 2.0 authorization. It supports federated identity management across multiple applications, commonly called Single Sign-On (SSO).

To create your Traditional web application, simply follow these steps:

Open the Logto Console. In the "Get started" section, click the "View all" link to open the application frameworks list. Alternatively, you can navigate to Logto Console > Applications, and click the "Create application" button.
In the opening modal, click the "Traditional web" section or filter all the available "Traditional web" frameworks using the quick filter checkboxes on the left. Click the "Flask" framework card to start creating your application.
Enter the application name, e.g., "Bookstore," and click "Create application".

🎉 Ta-da! You just created your first application in Logto. You'll see a congrats page which includes a detailed integration guide. Follow the guide to see what the experience will be in your application.

Integrate Flask with Logto

tip:

The example uses Flask, but the concepts are the same for other frameworks.
The Python sample project is available on our Python SDK repo.
Logto SDK leverages coroutines, remember to use await when calling async functions.

Installation

Execute in the project root directory:

pip install logto # or `poetry add logto` or whatever you use

Init LogtoClient

First, create a Logto config:

client.py
from logto import LogtoClient, LogtoConfig

client = LogtoClient(
    LogtoConfig(
        endpoint="https://you-logto-endpoint.app",  # Replace with your Logto endpoint
        appId="replace-with-your-app-id",
        appSecret="replace-with-your-app-secret",
    ),
)

tip:

You can find and copy "App Secret" from application details page in Admin Console:

Also replace the default memory storage with a persistent storage, for example:

client.py
from logto import LogtoClient, LogtoConfig, Storage
from flask import session
from typing import Union

class SessionStorage(Storage):
    def get(self, key: str) -> Union[str, None]:
        return session.get(key, None)

    def set(self, key: str, value: Union[str, None]) -> None:
        session[key] = value

    def delete(self, key: str) -> None:
        session.pop(key, None)

client = LogtoClient(
    LogtoConfig(...),
    storage=SessionStorage(),
)

See Storage for more details.

In your web application, add a route to properly handle the sign-in request from users. Let's use /sign-in as an example:

flask.py
@app.route("/sign-in")
async def sign_in():
  # Get the sign-in URL and redirect the user to it
  return redirect(await client.signIn(
      redirectUri="http://localhost:3000/callback",
  ))

Replace http://localhost:3000/callback with the callback URL you set in your Logto Console for this application.

If you want to show the sign-up page on the first screen, you can set interactionMode to signUp:

flask.py
@app.route("/sign-in")
async def sign_in():
  return redirect(await client.signIn(
      redirectUri="http://localhost:3000/callback",
      interactionMode="signUp", # Show the sign-up page on the first screen
  ))

Now, whenever your users visit http://localhost:3000/sign-in, it will start a new sign-in attempt and redirect the user to the Logto sign-in page.

Note Creating a sign-in route isn't the only way to start a sign-in attempt. You can always use the signIn method to get the sign-in URL and redirect the user to it.

After the user makes a signing-out request, Logto will clear all user authentication information in the session.

To clean up the Python session and Logto session, a sign-out route can be implemented as follows:

flask.py
@app.route("/sign-out")
async def sign_out():
  return redirect(
      # Redirect the user to the home page after a successful sign-out
      await client.signOut(postLogoutRedirectUri="http://localhost:3000/")
  )

Handle authentication status

In Logto SDK, we can use client.isAuthenticated() to check the authentication status, if the user is signed in, the value will be true, otherwise, the value will be false.

Here we also implement a simple home page for demonstration:

If the user is not signed in, show a sign-in button;
If the user is signed in, show a sign-out button.

@app.route("/")
async def home():
    if client.isAuthenticated() is False:
        return "Not authenticated <a href='/sign-in'>Sign in</a>"
    return "Authenticated <a href='/sign-out'>Sign out</a>"

Checkpoint: Test your application

Now, you can test your application:

Run your application, you will see the sign-in button.
Click the sign-in button, the SDK will init the sign-in process and redirect you to the Logto sign-in page.
After you signed in, you will be redirected back to your application and see the sign-out button.
Click the sign-out button to clear token storage and sign out.

Add Mailgun connector

Email connector is a method used to send one-time passwords (OTPs) for authentication. It enables Email address verification to support passwordless authentication, including Email-based registration, sign-in, two-factor authentication (2FA), and account recovery. You can easily connect Mailgun as your Email provider. With the Logto Email connector, you can set this up in just a few minutes.

To add a Email connector, simply follow these steps:

Navigate to Console > Connector > Email and SMS connectors.
To add a new Email connector, click the "Set up" button and select "Mailgun".
Review the README documentation for your selected provider.
Complete the configuration fields in the "Parameter Configuration" section.
Customize the Email template using the JSON editor.
Test your configuration by sending a verification code to your Email address.

note:

If you are following the in-place Connector guide, you can skip the next section.

Set up Mailgun email connector

Prerequisites

A Mailgun account
An API key from your Mailgun account, requires the permission to send messages (emails). See Where Can I Find My API Key and SMTP Credentials? for more information.

Basic configuration

Fill out the endpoint field when you are using a different Mailgun API endpoint, for example, EU region should be https://api.eu.mailgun.net. The default value is https://api.mailgun.net.
Fill out the domain field with the domain you have registered in your Mailgun account. This value can be found in the Domains section of the Mailgun dashboard. The domain should be in the format example.com, without the https:// or http:// prefix.
Fill out the apiKey field with the API key you have generated in your Mailgun account.
Fill out the from field with the email address you want to send emails from. This email address must be registered in your Mailgun account. The email address should be in the format Sender Name \<[email protected]>.

Deliveries

Config object

The "Deliveries" section allows you to configure the content of the emails to be sent in different scenarios. It is a JSON key-value map where the key is the usage type and the value is an object containing the content config for the email to be sent.

{
  "<usage-type>": {
    // ...
  }
}

Usage types

The following usage types are supported:

Register: The email to be sent when a user is registering.
SignIn: The email to be sent when a user is signing in.
ForgotPassword: The email to be sent when a user is resetting their password.
Generic: The email to be sent when a user is performing a generic action, for example, testing the email connector.

note:

If the usage type is not specified in the deliveries config, the generic email will be sent. If the generic email is not specified, the connector will return an error.

Content config

The connector supports both direct HTML content and Mailgun template. You can use one of them for each usage type.

In both subject and content, you can use the {{code}} placeholder to insert the verification code.

To use direct HTML content, fill out the following fields:

subject: The subject of the email to be sent.
replyTo: The email address to be used as the reply-to address.
html: (Required) The HTML content of the email to be sent.
text: The plain text version of the email to be sent.

To use Mailgun template, fill out the following fields:

subject: The subject of the email to be sent.
replyTo: The email address to be used as the reply-to address.
template: (Required) The name of the Mailgun template to be used.
variables: The variables to be passed to the Mailgun template. Should be a JSON key-value map since it will be stringified before sending to Mailgun. Note there's no need to include the code variable since it will be automatically added by the connector.

Example

The following is an example of the deliveries config:

{
  "Register": {
    "subject": "{{code}} is your verification code",
    "replyTo": "Foo <[email protected]>",
    "html": "<h1>Welcome to Logto</h1><p>Your verification code is {{code}}.</p>",
    "text": "Welcome to Logto. Your verification code is {{code}}."
  },
  "SignIn": {
    "subject": "Welcome back to Logto",
    "replyTo": "Foo <[email protected]>",
    "template": "logto-sign-in",
    "variables": {
      "bar": "baz"
    }
  }
}

Save your configuration

Double check you have filled out necessary values in the Logto connector configuration area. Click "Save and Done" (or "Save changes") and the Mailgun connector should be available now.

Once you create a connector successfully, you can enable phone number-based passwordless login and registration.

Navigate to Console > Sign-in experience > Sign-up and sign-in.
Set up sign-up methods (Optional):
1. Select "Email address" or "Email or phone number" as the sign-up identifier.
2. "Verify at sign-up" is forced to be enabled. You can also enable "Create a password" on registration.
Set up sign-in methods:
1. Select Email address as one of sign-in identifiers. You can provide multiple available identifiers (email, phone number, and username).
2. Select "Verification code" and / or "Password" as the authentication factor.
Click "Save changes" and test it in "Live preview".

In addition to registration and login via OTPs, you can also have password recovery and -based security verification enabled, as well as linking Email address to profile. See End-user flows for more details.

Testing and Validation

Return to your Python app. You should now be able to sign in with Mailgun. Enjoy!

Create an application in Logto​

Integrate Flask with Logto​

Installation​

Init LogtoClient​

Implement sign-in and sign-out​

Handle authentication status​

Checkpoint: Test your application​

Add Mailgun connector​

Set up Mailgun email connector​

Prerequisites​

Basic configuration​

Deliveries​

Config object​

Usage types​

Content config​

Example​

Save your configuration​

Enable Mailgun connector in Sign-in Experience​

Testing and Validation​

Further readings​