2.3.0 - Custom Payment Method - Invalid Form Key. Please refresh the page

Question

I have a custom payment method that uses the cc-form to take debit/credit card payments.

After the user has entered their card details, they are re-directed to my controller with a hidden form, then to the 3dsecure page.

After 3dsecure, they are re-directed to the same controller and various logic is checked.

After the logic is valid, they are re-directed to the checkout success page.

This was working with Magento 2.2, but in 2.3.0 this is not working.

After placing order, I am re-directed to 3dsecure as normal, but on returning from 3dsecure, I am re-directed to the home page with

"Invalid Form Key. Please refresh the page."

Answer 1

Your Response Controller must implement CsrfAwareActionInterface and 2 of its methods. Your response controller should be like this.Then only form key issues will fix. I have the same issue in paytabs payment method and resolved using this way

    use Magento\Framework\App\CsrfAwareActionInterface;
    use Magento\Framework\App\Request\InvalidRequestException;
    use Magento\Framework\App\RequestInterface;

    class CustomPaymentResponse extends \Magento\Framework\App\Action\Action implements CsrfAwareActionInterface
    {

        /** 
         * @inheritDoc
         */
        public function createCsrfValidationException(
            RequestInterface $request 
        ): ?InvalidRequestException {
            return null;
        }

        /**
         * @inheritDoc
         */
        public function validateForCsrf(RequestInterface $request): ?bool
        {
            return true;
        }
       /**
         * Dispatch request
         *
         * @return \Magento\Framework\Controller\ResultInterface|ResponseInterface
         * @throws \Magento\Framework\Exception\NotFoundException
         */
       public function execute()
        {
        //your response check
        }
    }