$app = new Silex\Application;

$oAuth2Provider = new TH\OAuth2\Pimple\OAuth2ServerProvider;
$app['security.entry_point.api.oauth2.realm'] = 'My App';
$app->register($oAuth2Provider, [
    'oauth2_server.storage.client' => function () use ($config) {
        return new TH\OAuth2\Storage\Memory\ClientMemoryStorage([
            'NICE_DEV_CLIENT' => [
                'name' => 'Nice Dev Client',
                'redirect_uri' => 'http://..../my_oauth2_callback',
            ],
        ]);
    },
    'oauth2_server.storage.pdo_connection' => function(Application $app) {
        return new PDO('...');
    },
]);
$app->mount('/auth/', $oAuth2Provider);

$app['users.provider'] = [
    // raw password is foo
    'admin' => array('ROLE_ADMIN', '5FZ2Z8QIkA7UTZ4BYkoC+GsReLf569mSKDsfods6LYQ8t+a8EW9oaircfMpmaLbPBh4FOBiiFyLfuZmTSUwzZg=='),
];

$app->register(new Silex\Provider\SecurityServiceProvider, [
    'security.firewalls' => [
        'oauth.token' => [
            'pattern' => '^/auth/token',
            'security' => false,
        ],
        'oauth.authorize' => [
            'pattern' => '^/auth/authorize',
            'http' => true,
            'users' => $app['users.provider'],
        ],
        'api' => [
            'pattern' => '^/api',
            'stateless' => true,
            'oauth2' => true,
            'security' => true,
            'users' => $app['users.provider'],
        ],
    ],
]);