Code-via-Email Authentication

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Code-via-Email Authentication

A two-factor provider to generate a random numeric code and send it to the user via email.

How authentication works

On successful authentication it generates a random number and persists it in the user entity. The number is sent to the user via email. Then the user must enter that number to gain access.

The number of digits can be configured:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        digits: 6

Installation

To make use of this feature, you have to install scheb/2fa-email.

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composer require scheb/2fa-email

The bundle's default implementation for sending emails assumes you're using symfony/mailer. To install the package:

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composer require symfony/mailer

You're free to use any other mail-sending library you like, but then you have to implement a custom mailer class (instructions below).

Basic Configuration

To enable this authentication method add this to your configuration:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        enabled: true
        sender_email: no-reply@example.com
        sender_name: John Doe  # Optional

Your user entity has to implement Scheb\TwoFactorBundle\Model\Email\TwoFactorInterface. The authentication code must be persisted, so make sure that it is stored in a persisted field.

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<?php

namespace Acme\Demo\Entity;

use Doctrine\ORM\Mapping as ORM;
use Scheb\TwoFactorBundle\Model\Email\TwoFactorInterface;
use Symfony\Component\Security\Core\User\UserInterface;

class User implements UserInterface, TwoFactorInterface
{
    /**
     * @ORM\Column(type="string")
     */
    private string $email;

    /**
     * @ORM\Column(type="string", nullable=true)
     */
    private string $authCode;

    // [...]

    public function isEmailAuthEnabled(): bool
    {
        return true; // This can be a persisted field to switch email code authentication on/off
    }

    public function getEmailAuthRecipient(): string
    {
        return $this->email;
    }

    public function getEmailAuthCode(): string
    {
        if (null === $this->authCode) {
            throw new \LogicException('The email authentication code was not set');
        }

        return $this->authCode;
    }

    public function setEmailAuthCode(string $authCode): void
    {
        $this->authCode = $authCode;
    }
}

Configuration Reference

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        enabled: true                  # If email authentication should be enabled, default false
        mailer: acme.custom_mailer_service  # Use alternative service to send the authentication code
        code_generator: acme.custom_code_generator_service  # Use alternative service to generate authentication code
        sender_email: me@example.com   # Sender email address
        sender_name: John Doe          # Sender name
        digits: 4                      # Number of digits in authentication code
        template: security/2fa_form.html.twig   # Template used to render the authentication form

Custom Mailer

By default the email is plain text and very simple. If you want a different style (e.g. HTML) you have to create your own mailer service. It must implement Scheb\TwoFactorBundle\Mailer\AuthCodeMailerInterface.

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<?php

namespace Acme\Demo\Mailer;

use Scheb\TwoFactorBundle\Model\Email\TwoFactorInterface;
use Scheb\TwoFactorBundle\Mailer\AuthCodeMailerInterface;

class MyAuthCodeMailer implements AuthCodeMailerInterface
{
    // [...]

    public function sendAuthCode(TwoFactorInterface $user): void
    {
        $authCode = $user->getEmailAuthCode();

        // Send email
    }
}

Then register it as a service and update your configuration:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        mailer: acme.custom_mailer_service

Re-send Authentication Code

When you're using the default authentication code generator that is coming with the bundle, there's an easy way to resend the email with the authentication code. Get/inject service scheb_two_factor.security.email.code_generator and call method reSend(\Scheb\TwoFactorBundle\Model\Email\TwoFactorInterface $user).

Custom Code Generator

If you want to have the code generated differently, you can have your own code generator. Create a service implementing Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Email\Generator\CodeGeneratorInterface and register it in the configuration:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        code_generator: acme.custom_code_generator_service

Custom Authentication Form Template

The bundle uses Resources/views/Authentication/form.html.twig to render the authentication form. If you want to use a different template you can simply register it in configuration:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        template: security/2fa_form.html.twig

Custom Form Rendering

There are certain cases when it's not enough to just change the template. For example, you're using two-factor authentication on multiple firewalls and you need to render the form differently for each firewall. In such a case you can implement a form renderer to fully customize the rendering logic.

Create a class implementing Scheb\TwoFactorBundle\Security\TwoFactor\Provider\TwoFactorFormRendererInterface:

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<?php

namespace Acme\Demo\FormRenderer;

use Scheb\TwoFactorBundle\Security\TwoFactor\Provider\TwoFactorFormRendererInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

class MyFormRenderer implements TwoFactorFormRendererInterface
{
    // [...]

    public function renderForm(Request $request, array $templateVars): Response
    {
        // Customize form rendering
    }
}

Then register it as a service and update your configuration:

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# config/packages/scheb_2fa.yaml
scheb_two_factor:
    email:
        form_renderer: acme.custom_form_renderer_service
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.