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Form Protection Component

class FormProtection(ComponentCollection $collection, array $config = [])

The FormProtection Component provides protection against form data tampering.

Like all components it is configured through several configurable parameters. All of these properties can be set directly or through setter methods of the same name in your controller’s initialize() or beforeFilter() methods.

If you are using other components that process form data in their startup() callbacks, be sure to place FormProtection Component before those components in your initialize() method.

Note

When using the FormProtection Component you must use the FormHelper to create your forms. In addition, you must not override any of the fields’ “name” attributes. The FormProtection Component looks for certain indicators that are created and managed by the FormHelper (especially those created in Cake\View\Helper\FormHelper::create() and Cake\View\Helper\FormHelper::end()). Dynamically altering the fields that are submitted in a POST request, such as disabling, deleting or creating new fields via JavaScript, is likely to cause the form token validation to fail.

Form tampering prevention

By default the FormProtectionComponent prevents users from tampering with forms in specific ways. It will prevent the following things:

  • Form’s action (URL) cannot be modified.

  • Unknown fields cannot be added to the form.

  • Fields cannot be removed from the form.

  • Values in hidden inputs cannot be modified.

Preventing these types of tampering is accomplished by working with the FormHelper and tracking which fields are in a form. The values for hidden fields are tracked as well. All of this data is combined and turned into a hash and hidden token fields are automatically be inserted into forms. When a form is submitted, the FormProtectionComponent will use the POST data to build the same structure and compare the hash.

Note

The FormProtectionComponent will not prevent select options from being added/changed. Nor will it prevent radio options from being added/changed.

Usage

Configuring the form protection component is generally done in the controller’s initialize() or beforeFilter() callbacks

Available options are:

validate

Set to false to completely skip the validation of POST requests, essentially turning off form validation.

unlockedFields

Set to a list of form fields to exclude from POST validation. Fields can be unlocked either in the Component, or with FormHelper::unlockField(). Fields that have been unlocked are not required to be part of the POST and hidden unlocked fields do not have their values checked.

unlockedActions

Actions to exclude from POST validation checks.

validationFailureCallback

Callback to call in case of validation failure. Must be a valid Closure. Unset by default in which case exception is thrown on validation failure.

Disabling form tampering checks

namespace App\Controller;

use App\Controller\AppController;
use Cake\Event\EventInterface;

class WidgetsController extends AppController
{
    public function initialize(): void
    {
        parent::initialize();

        $this->loadComponent('FormProtection');
    }

    public function beforeFilter(EventInterface $event)
    {
        parent::beforeFilter($event);

        if ($this->request->getParam('prefix') === 'Admin') {
            $this->FormProtection->setConfig('validate', false);
        }
    }
}

The above example would disable form tampering prevention for admin prefixed routes.

Disabling form tampering for specific actions

There may be cases where you want to disable form tampering prevention for an action (ex. AJAX requests). You may “unlock” these actions by listing them in $this->FormProtection->setConfig('unlockedActions', ['edit']); in your beforeFilter():

namespace App\Controller;

use App\Controller\AppController;
use Cake\Event\EventInterface;

class WidgetController extends AppController
{
    public function initialize(): void
    {
        parent::initialize();
        $this->loadComponent('FormProtection');
    }

    public function beforeFilter(EventInterface $event)
    {
        parent::beforeFilter($event);

        $this->FormProtection->setConfig('unlockedActions', ['edit']);
    }
}

This example would disable all security checks for the edit action.

Handling validation failure through callbacks

If form protection validation fails it will result in a 400 error by default. You can configure this behavior by setting the validationFailureCallback configuration option to a callback function in the controller.

By configuring a callback method you can customize how the failure handling process works:

public function beforeFilter(EventInterface $event)
{
    parent::beforeFilter($event);

    $this->FormProtection->setConfig(
        'validationFailureCallback',
        function (BadRequestException $exception) {
            // You can either return a response instance or throw the exception
            // received as argument.
        }
    );
}