Ability to change order address without triggering address validations in solidus

Impact

This vulnerability allows a malicious customer to craft request data with
parameters that allow changing the address of the current order without
changing the shipment costs associated with the new shipment.

All stores with at least two shipping zones and different costs of shipment
per zone are impacted.

E.g.

1. Store admin configured the store so that there are two zones in US:
   • East Cost Zone - Shipping Method cost: $1
   • West Cost Zone - Shipping Method cost: $10

The attacker user can know that shipping to NY is less expensive than to LA
just by testing different addresses in checkout.

2. The attacker user enters any NY shipping address in the address step
3. The attacker user chooses the $1 delivery option
4. The attacker user crafts a request with their real LA address, similar to:

// POST #checkout/update:

{
  state: 'payment',
  order: {
    ship_address_attributes: {
      city: 'Los Angeles',
      ...
    }
  }
}

5. The attacker user proceeds with checking out with a new address and the $1
   shipment costs.

Another scenario where this could be dangerous is:

> You cannot ship products in some zones and you are relying on Solidus
> Shipping Method building only to filter out unwanted zones. Malicious
> users can enter an allowed zone’s address and change back to an unwanted
> one in the payment step by crafting a request with some proper
> ship_address_attributes.

This problem comes from how checkout permitted attributes are structured.
We have a single list of attributes that are permitted across the whole
checkout, no matter the step that is being submitted.

Workarounds

When it’s not possible to upgrade to a supported patched version, please
use this gist to patch the store:

https://gist.github.com/kennyadsl/4618cd9797984cb64f7700a81bda889d