Backend login form API 

Registering a login provider 

The concept of the backend login is based on "login providers".

A login provider can be registered within your config/system/settings.php or config/system/additional.php like this:

$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['backend']['loginProviders'][1433416020] = [
    'provider' => \MyVendor\MyExtension\LoginProvider\CustomLoginProvider::class,
    'sorting' => 50,
    'iconIdentifier' => 'actions-key',
    'label' => 'LLL:EXT:backend/Resources/Private/Language/locallang.xlf:login.link'
];

The settings are defined as:

provider

The login provider class name, which must implement \TYPO3\CMS\Backend\LoginProvider\LoginProviderInterface .

sorting

The sorting is important for the ordering of the links to the possible login providers on the login screen.

iconIdentifier

Accepts any icon identifier that is available in the Icon Registry.

label

The label for the login provider link on the login screen.

For a new login provider you have to register a new key - by best practice the current unix timestamp - in $GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['backend']['loginProviders'] .

If your login provider extends another one, you may only overwrite necessary settings. An example would be to extend an existing provider and replace its registered provider class with your custom class.

$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['backend']['loginProviders'][1433416020]['provider'] =
    \MyVendor\MyExtension\LoginProvider\CustomProviderExtendingUsernamePasswordLoginProvider::class

LoginProviderInterface 

interface LoginProviderInterface

Fully qualified name

\TYPO3\CMS\Backend\LoginProvider\LoginProviderInterface

Interface for Backend Login providers

modifyView ( \Psr\Http\Message\ServerRequestInterface $request, \TYPO3\CMS\Core\View\ViewInterface $view)

Interface to render the backend login view.

See UsernamePasswordLoginProvider on how this can be used.

param $request

the request

param $view

the view

Return description

Template file to render

Returns

string

Consumers of LoginProviderInterface should implement the modifyView() method. See the example below.

An implementation of LoginProviderInterface could look like this:

<?php

namespace MyVendor\MyExtension\Login;

use Psr\Http\Message\ServerRequestInterface;
use Symfony\Component\DependencyInjection\Attribute\Autoconfigure;
use TYPO3\CMS\Backend\LoginProvider\LoginProviderInterface;
use TYPO3\CMS\Core\Page\PageRenderer;
use TYPO3\CMS\Core\View\ViewInterface;
use TYPO3\CMS\Fluid\View\FluidViewAdapter;

#[Autoconfigure(public: true)]
final readonly class MyLoginProvider implements LoginProviderInterface
{
    public function __construct(
        private PageRenderer $pageRenderer,
    ) {}

    public function modifyView(ServerRequestInterface $request, ViewInterface $view): string
    {
        $this->pageRenderer->addJsFile('someFile');
        // Custom login provider implementations can add custom fluid lookup paths.
        if ($view instanceof FluidViewAdapter) {
            $templatePaths = $view->getRenderingContext()->getTemplatePaths();
            $templateRootPaths = $templatePaths->getTemplateRootPaths();
            $templateRootPaths[] = 'EXT:my_extension/Resources/Private/Templates';
            $templatePaths->setTemplateRootPaths($templateRootPaths);
        }
        $view->assign('Some Variable', 'some value');
        return 'Login/MyLoginForm';
    }
}

The default implementation in UsernamePasswordLoginProvider is a good example. Extensions that need to configure additional template, layout or partial lookup paths can extend them, see lines 23-28 in the example above.

The view 

The name of the template must be returned by the modifyView() method of the login provider. Variables can be assigned to the view supplied as second parameter.

The template file must only contain the form fields, not the form-tag. Later on, the view renders the complete login screen.

View requirements:

• The template must use the Login-layout provided by the Core <f:layout name="Login">.
• Form fields must be provided within the section <f:section name="loginFormFields">.

<f:layout name="Login" />
<f:section name="loginFormFields">
    <div class="form-group t3js-login-openid-section" id="t3-login-openid_url-section">
        <div class="input-group">
            <input
                type="text"
                id="openid_url"
                name="openid_url"
                value="{presetOpenId}"
                autofocus="autofocus"
                placeholder="{f:translate(key: 'openId', extensionName: 'openid')}"
                class="form-control input-login t3js-clearable t3js-login-openid-field"
            >
            <div class="input-group-addon">
                <span class="fa fa-openid"></span>
            </div>
        </div>
    </div>
</f:section>

Examples 

Within the Core you can find the standard implementation in the system extension backend:

See class EXT:backend/Classes/LoginProvider/UsernamePasswordLoginProvider.php (GitHub) with its template EXT:backend/Resources/Private/Templates/Login/UserPassLoginForm.fluid.html (GitHub).