Symfony2 HTTP_BASIC authentication [duplicate]

For some reason It's impossible to get access to my secured page. Every time I enter valid credentials the authentication pop-up comes up again. Any suggestions? Am I blind or stupid?

security:
    encoders:
        Symfony\Component\Security\Core\User\User: plaintext
    providers:
        in_memory:
            memory: 
                users:
                    tom: { password: lamp, roles: ROLE_USER }
                    gaelle: { password: lamp, roles: ROLE_USER }
                    tmas: { password: lamp, roles: ROLE_USER }

    firewalls:
        dev:
            pattern: ^/(_(profiler|wdt)|css|images|js)/
            security: false

        default:
            pattern: ^/
            anonymous: ~
            http_basic:
                realm: "Gaelle & Tom - Login"
                provider: in_memory

    access_control:
        - { path: ^/admin, roles: ROLE_USER }

I tried multiple things, including adding this line to my .htacccess:

RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization},L]

My config is declared valid and feedback from logging gives me no information. These lines keep repeating itself after each login attempt:

[2015-01-15 13:03:04] security.DEBUG: Access is denied (user is not fully authenticated) by "/var/www/gaelleentom/vendor/symfony/symfony/src/Symfony/Component/Security/Http/Firewall/AccessListener.php" at line 70; redirecting to authentication entry point [] []

[2015-01-15 13:03:04] security.DEBUG: Calling Authentication entry point [] []

I'm using Symfony version 2.6