woocommerce/includes/helpers/class-wc-nonce-helper.php

<?php

return new WC_Nonce_Helper();

class WC_Nonce_Helper extends WC_Helper {
	/**
	 * Return a nonce field.
	 *
	 * @access public
	 * @param mixed $action
	 * @param bool $referer (default: true)
	 * @param bool $echo (default: true)
	 * @return void
	 */
	public function nonce_field( $action, $referer = true , $echo = true ) {
		return wp_nonce_field('woocommerce-' . $action, '_n', $referer, $echo );
	}


	/**
	 * Return a url with a nonce appended.
	 *
	 * @access public
	 * @param mixed $action
	 * @param string $url (default: '')
	 * @return string
	 */
	public function nonce_url( $action, $url = '' ) {
		return add_query_arg( '_n', wp_create_nonce( 'woocommerce-' . $action ), $url );
	}

	/**
	 * Check a nonce and sets woocommerce error in case it is invalid.
	 *
	 * To fail silently, set the error_message to an empty string
	 *
	 * @access public
	 * @param string $name the nonce name
	 * @param string $action then nonce action
	 * @param string $method the http request method _POST, _GET or _REQUEST
	 * @param string $error_message custom error message, or false for default message, or an empty string to fail silently
	 * @return bool
	 */
	public function verify_nonce( $action, $method='_POST', $error_message = false ) {

		$name = '_n';
		$action = 'woocommerce-' . $action;

		if ( $error_message === false ) $error_message = __( 'Action failed. Please refresh the page and retry.', 'woocommerce' );

		if ( ! in_array( $method, array( '_GET', '_POST', '_REQUEST' ) ) ) $method = '_POST';

		if ( isset($_REQUEST[$name] ) && wp_verify_nonce( $_REQUEST[$name], $action ) ) return true;

		if ( $error_message ) $this->add_error( $error_message );

		return false;
	}
}