FP: Double withdrawal

[elRaulito]

No description provided.

[keyan-m]

Not a full review, but just pointing out one thing I spotted :)

[keyan-m]

Validation on the NFT seems missing. We do have a helper:

midgard/onchain/aiken/lib/midgard/common/utils.ak

Lines 139 to 156 in ca46d75

	/// For beacon UTxOs with specific policy IDs. Note that the address is not
	/// checked.
	pub fn get_authentic_input_with_policy_at(
	inputs: List<Input>,
	nft_policy_id: PolicyId,
	input_index: Int,
	) -> Input {
	expect Some(
	Input { output: Output { value: input_value, .. }, .. } as found_input,
	) = list.at(inputs, input_index)
	expect (input_nft_policy_id, _, 1) =
	get_single_asset_from_value_apart_from_ada(input_value)
	expect input_nft_policy_id == nft_policy_id
	found_input
	}

Suggested change

	pub fn get_withdrawals_root(
	tx: Transaction,
	state_queue_node_ref_input_index: Int,
	) -> ByteArray {
	// Reference input with block_hash
	expect Some(state_queue_node_input) =
	list.at(tx.reference_inputs, state_queue_node_ref_input_index)
	pub fn get_withdrawals_root(
	reference_inputs: List<Input>,
	state_queue_policy: PolicyId,
	state_queue_node_ref_input_index: Int,
	) -> ByteArray {
	// Reference input with block_hash
	let state_queue_node_input =
	utils.get_authentic_input_with_policy_at(
	reference_inputs,
	state_queue_policy,
	state_queue_node_ref_input_index,
	)

It might make sense to also define a get_datum in /lib/midgard/state-queue.ak (similar to the one we have in hub-oracle.ak) and use it here.

[elRaulito]

Hey @keyan-m

isn't this code doing the nft beacon verification?

let ct_token_asset_name = get_singleton_ct_token(own_input, ct_token_policy_id)

[elRaulito]

Oh nevermind I see

I get the asset name but I never use it

[keyan-m]

That line seems fine and is validating authenticity of the input (own_input). For the withdrawals root, we're reading the datum off of a reference input, so its state token must also be validated.

[elRaulito]

Isn't that missing also here then?

midgard\fraud-proof\common\utils.ak

pub fn get_tx_root_validate_block_hash(
  tx: Transaction,
  state_queue_node_ref_input_index: Int,
  ct_token_asset_name: ByteArray,
) -> ByteArray {
  // Reference input with block_hash 
  expect Some(state_queue_node_input) =
    list.at(tx.reference_inputs, state_queue_node_ref_input_index)

  // Extract tx_root via the state queue block hash
  expect InlineDatum(state_queue_datum_data) =
    state_queue_node_input.output.datum
  expect state_queue_node_datum: unordered.NodeDatum = state_queue_datum_data
  expect parsed_state_queue_datum: Header = state_queue_node_datum.data
  expect unordered.Key { key: block_hash } = state_queue_node_datum.key
  let extracted_tx_root = parsed_state_queue_datum.transactions_root

  // Get CT token and check match with the block hash
  expect drop(ct_token_asset_name, n: 4) == block_hash

  extracted_tx_root
}

[keyan-m]

It seems to be, yeah. I would suggest defining get_confirmed_datum and get_block_datum helpers under /lib/midgard/state-queue.ak so that they can be reused for such validations.