bug #25508 [FrameworkBundle] Auto-enable CSRF if the component *+ session* are loaded (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
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[FrameworkBundle] Auto-enable CSRF if the component *+ session* are loaded

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/recipes/issues/262
| License       | MIT
| Doc PR        | -

By binding CSRF and session default state, we provide better DX, but we also provide a way for bundles to enable session on its own: they just need to require "symfony/security-csrf".
Yes, that's a side effect, but I think that's a nice one for 3.4/4.0.
Of course, we might do better in 4.1, but for bug fix only releases, LGTM.

Commits
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9e8231f [FrameworkBundle] Automatically enable the CSRF if component *+ session* are loaded

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php

@@ -21,6 +21,7 @@ use Symfony\Component\Config\Definition\ConfigurationInterface;
 use Symfony\Component\Form\Form;
 use Symfony\Component\Lock\Lock;
 use Symfony\Component\Lock\Store\SemaphoreStore;
+use Symfony\Component\Security\Csrf\CsrfTokenManagerInterface;
 use Symfony\Component\Serializer\Serializer;
 use Symfony\Component\Translation\Translator;
 use Symfony\Component\Validator\Validation;
@@ -142,7 +143,14 @@ class Configuration implements ConfigurationInterface
         $rootNode
             ->children()
                 ->arrayNode('csrf_protection')
-                    ->canBeEnabled()
+                    ->treatFalseLike(array('enabled' => false))
+                    ->treatTrueLike(array('enabled' => true))
+                    ->treatNullLike(array('enabled' => true))
+                    ->addDefaultsIfNotSet()
+                    ->children()
+                        // defaults to framework.session.enabled && !class_exists(FullStack::class) && interface_exists(CsrfTokenManagerInterface::class)
+                        ->booleanNode('enabled')->defaultNull()->end()
+                    ->end()
                 ->end()
             ->end()
         ;

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php

@@ -17,6 +17,7 @@ use Symfony\Bridge\Monolog\Processor\DebugProcessor;
 use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Symfony\Bundle\FrameworkBundle\Routing\AnnotatedRouteControllerLoader;
+use Symfony\Bundle\FullStack;
 use Symfony\Component\Cache\Adapter\AbstractAdapter;
 use Symfony\Component\Cache\Adapter\AdapterInterface;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
@@ -65,6 +66,7 @@ use Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface;
 use Symfony\Component\Routing\Loader\AnnotationDirectoryLoader;
 use Symfony\Component\Routing\Loader\AnnotationFileLoader;
 use Symfony\Component\Security\Core\Security;
+use Symfony\Component\Security\Csrf\CsrfTokenManagerInterface;
 use Symfony\Component\Serializer\Encoder\DecoderInterface;
 use Symfony\Component\Serializer\Encoder\EncoderInterface;
 use Symfony\Component\Serializer\Mapping\Factory\CacheClassMetadataFactory;
@@ -231,6 +233,11 @@ class FrameworkExtension extends Extension
             $this->registerRequestConfiguration($config['request'], $container, $loader);
         }
 
+        if (null === $config['csrf_protection']['enabled']) {
+            $config['csrf_protection']['enabled'] = $this->sessionConfigEnabled && !class_exists(FullStack::class) && interface_exists(CsrfTokenManagerInterface::class);
+        }
+        $this->registerSecurityCsrfConfiguration($config['csrf_protection'], $container, $loader);
+
         if ($this->isConfigEnabled($container, $config['form'])) {
             if (!class_exists('Symfony\Component\Form\Form')) {
                 throw new LogicException('Form support cannot be enabled as the Form component is not installed.');
@@ -251,8 +258,6 @@ class FrameworkExtension extends Extension
             $container->removeDefinition('console.command.form_debug');
         }
 
-        $this->registerSecurityCsrfConfiguration($config['csrf_protection'], $container, $loader);
-
         if ($this->isConfigEnabled($container, $config['assets'])) {
             if (!class_exists('Symfony\Component\Asset\Package')) {
                 throw new LogicException('Asset support cannot be enabled as the Asset component is not installed.');