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Use case:

Alice submits an extrinsic on chain A which, among other things, sends an XCM message including a Transact operation to chain B.

On chain A, Alice pays for the extrinsic execution. What I am trying to do, is to let Alice also pay with her account on chain B.

The XCM that is composed inside the extrinsic is the following:

[
  DescendOrigin(
    AccountId32 {
      network: None,
      id: dispatcher.into(),
    }.into(),
  ),
  WithdrawAsset(asset.clone().into()),
  BuyExecution {
    fees: asset,
    weight_limit: Unlimited,
  },
  Transact {
    origin_kind: OriginKind::Native,
    require_weight_at_most: weight,
    call: dest_tx,
  }
]

where dispatcher is the signed origin on chain A, asset and weight are parameters of the extrinsic and must be under the control of Alice on chain B.

Clearly, I could only use a OriginKind::Native since otherwise the call would not have the parachain priviledge. Nevertheless, I cannot get the Transact to be executed without getting a BadOrigin error. It does not seem possible, right now, to have an OriginConverter which accepts a Multilocation of type ../Parachain(x)/AccountId(acc). The LocationConverter works fine with just using the provided Account32Hash<(), AccountId>, although a new PR is in the making to address this. On the contrary, origin conversion does not seem to be supported, and of course any attempt to insert a ClearOrigin call before the Transact would fail.

Is calling UniversalOrigin the only way to charge a user on chain B for the execution of the Transact? Or is there some other way to charge the user on chain B while still making sure that only the chain A can indeed send such XCM message? An OriginKind::SoverignAccount does not seem to be good for our case since everyone could just send it via the XCM pallet, while chain A wants to give chain B guarantees that the messages has higher priviledge then a simple user.

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