How to Build a Traditional Login Form

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How to Build a Traditional Login Form

Tip

If you need a login form and are storing users in some sort of a database, then you should consider using FOSUserBundle, which helps you build your User object and gives you many routes and controllers for common tasks like login, registration and forgot password.

In this entry, you'll build a traditional login form. Of course, when the user logs in, you can load your users from anywhere - like the database. See Security for details.

First, enable form login under your firewall:

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# app/config/security.yml
security:
    # ...

    firewalls:
        main:
            anonymous: ~
            form_login:
                login_path: login
                check_path: login

Tip

The login_path and check_path can also be route names (but cannot have mandatory wildcards - e.g. /login/{foo} where foo has no default value).

Now, when the security system initiates the authentication process, it will redirect the user to the login form /login. Implementing this login form visually is your job. First, create a new SecurityController inside a bundle:

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// src/AppBundle/Controller/SecurityController.php
namespace AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;

class SecurityController extends Controller
{
}

Next, configure the route that you earlier used under your form_login configuration (login):

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// src/AppBundle/Controller/SecurityController.php

// ...
use Symfony\Component\HttpFoundation\Request;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;

class SecurityController extends Controller
{
    /**
     * @Route("/login", name="login")
     */
    public function loginAction(Request $request)
    {
    }
}

Great! Next, add the logic to loginAction that will display the login form:

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// src/AppBundle/Controller/SecurityController.php

public function loginAction(Request $request)
{
    $authenticationUtils = $this->get('security.authentication_utils');

    // get the login error if there is one
    $error = $authenticationUtils->getLastAuthenticationError();

    // last username entered by the user
    $lastUsername = $authenticationUtils->getLastUsername();

    return $this->render(
        'security/login.html.twig',
        array(
            // last username entered by the user
            'last_username' => $lastUsername,
            'error'         => $error,
        )
    );
}

Don't let this controller confuse you. As you'll see in a moment, when the user submits the form, the security system automatically handles the form submission for you. If the user submits an invalid username or password, this controller reads the form submission error from the security system, so that it can be displayed back to the user.

In other words, your job is to display the login form and any login errors that may have occurred, but the security system itself takes care of checking the submitted username and password and authenticating the user.

Finally, create the template:

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{# app/Resources/views/security/login.html.twig #}
{# ... you will probably extends your base template, like base.html.twig #}

{% if error %}
    <div>{{ error.messageKey|trans(error.messageData, 'security') }}</div>
{% endif %}

<form action="{{ path('login') }}" method="post">
    <label for="username">Username:</label>
    <input type="text" id="username" name="_username" value="{{ last_username }}" />

    <label for="password">Password:</label>
    <input type="password" id="password" name="_password" />

    {#
        If you want to control the URL the user
        is redirected to on success (more details below)
        <input type="hidden" name="_target_path" value="/account" />
    #}

    <button type="submit">login</button>
</form>

Tip

The error variable passed into the template is an instance of AuthenticationException. It may contain more information - or even sensitive information - about the authentication failure, so use it wisely!

The form can look like anything, but has a few requirements:

  • The form must POST to the login route, since that's what you configured under the form_login key in security.yml.
  • The username must have the name _username and the password must have the name _password.

Tip

Actually, all of this can be configured under the form_login key. See SecurityBundle Configuration ("security") for more details.

Caution

This login form is currently not protected against CSRF attacks. Read Using CSRF Protection in the Login Form on how to protect your login form.

And that's it! When you submit the form, the security system will automatically check the user's credentials and either authenticate the user or send the user back to the login form where the error can be displayed.

To review the whole process:

  1. The user tries to access a resource that is protected;
  2. The firewall initiates the authentication process by redirecting the user to the login form (/login);
  3. The /login page renders login form via the route and controller created in this example;
  4. The user submits the login form to /login;
  5. The security system intercepts the request, checks the user's submitted credentials, authenticates the user if they are correct, and sends the user back to the login form if they are not.

Redirecting after Success

If the submitted credentials are correct, the user will be redirected to the original page that was requested (e.g. /admin/foo). If the user originally went straight to the login page, they'll be redirected to the homepage. This can all be customized, allowing you to, for example, redirect the user to a specific URL.

For more details on this and how to customize the form login process in general, see How to Customize your Form Login.

Avoid Common Pitfalls

When setting up your login form, watch out for a few common pitfalls.

1. Create the Correct Routes

First, be sure that you've defined the /login route correctly and that it corresponds to the login_path and check_path config values. A misconfiguration here can mean that you're redirected to a 404 page instead of the login page, or that submitting the login form does nothing (you just see the login form over and over again).

2. Be Sure the Login Page Isn't Secure (Redirect Loop!)

Also, be sure that the login page is accessible by anonymous users. For example, the following configuration - which requires the ROLE_ADMIN role for all URLs (including the /login URL), will cause a redirect loop:

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# app/config/security.yml

# ...
access_control:
    - { path: ^/, roles: ROLE_ADMIN }

Adding an access control that matches /login/* and requires no authentication fixes the problem:

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# app/config/security.yml

# ...
access_control:
    - { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
    - { path: ^/, roles: ROLE_ADMIN }

Also, if your firewall does not allow for anonymous users (no anonymous key), you'll need to create a special firewall that allows anonymous users for the login page:

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# app/config/security.yml

# ...
firewalls:
    # order matters! This must be before the ^/ firewall
    login_firewall:
        pattern:   ^/login$
        anonymous: ~
    secured_area:
        pattern:    ^/
        form_login: ~

3. Be Sure check_path Is Behind a Firewall

Next, make sure that your check_path URL (e.g. /login) is behind the firewall you're using for your form login (in this example, the single firewall matches all URLs, including /login). If /login doesn't match any firewall, you'll receive a Unable to find the controller for path "/login" exception.

4. Multiple Firewalls Don't Share the Same Security Context

If you're using multiple firewalls and you authenticate against one firewall, you will not be authenticated against any other firewalls automatically. Different firewalls are like different security systems. To do this you have to explicitly specify the same SecurityBundle Configuration ("security") for different firewalls. But usually for most applications, having one main firewall is enough.

5. Routing Error Pages Are not Covered by Firewalls

As routing is done before security, 404 error pages are not covered by any firewall. This means you can't check for security or even access the user object on these pages. See How to Customize Error Pages for more details.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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