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Implement swap recover function for Alice

Browse source 
This introduces a lot of duplication between the binary and the
library, but it's okay because this module should only be a temporary
measure until we allow recovery to be handled by the original state
machine.

Also, fix a bug in `xmr_btc::alice::action_generator` caused by the
incorrect assumption that Alice's ability to punish Bob could be
determined before the cancel transaction hits the blockchain.
This commit is contained in:
Lucas Soriano del Pino 2020-11-03 17:08:31 +11:00 • committed by rishflab
parent b989e94322
commit 28225f8643
8 changed files with 242 additions and 97 deletions
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93
xmr-btc/src/alice.rs
View file

@ -97,7 +97,7 @@ where
#[derive(Debug)]
enum SwapFailed {
BeforeBtcLock(Reason),
AfterXmrLock { tx_lock_height: u32, reason: Reason },
AfterXmrLock(Reason),
}
/// Reason why the swap has failed.
@ -114,9 +114,7 @@ where
#[derive(Debug)]
enum RefundFailed {
BtcPunishable {
tx_cancel_was_published: bool,
},
BtcPunishable,
/// Could not find Alice's signature on the refund transaction witness
/// stack.
BtcRefundSignature,
@ -167,12 +165,7 @@ where
.await
{
Either::Left((encsig, _)) => encsig,
Either::Right(_) => {
return Err(SwapFailed::AfterXmrLock {
reason: Reason::BtcExpired,
tx_lock_height,
})
}
Either::Right(_) => return Err(SwapFailed::AfterXmrLock(Reason::BtcExpired)),
};
tracing::debug!("select returned redeem encsig from message");
@ -191,10 +184,7 @@ where
&tx_redeem.digest(),
&tx_redeem_encsig,
)
.map_err(|_| SwapFailed::AfterXmrLock {
reason: Reason::InvalidEncryptedSignature,
tx_lock_height,
})?;
.map_err(|_| SwapFailed::AfterXmrLock(Reason::InvalidEncryptedSignature))?;
let sig_a = a.sign(tx_redeem.digest());
let sig_b =
@ -217,12 +207,7 @@ where
.await
{
Either::Left(_) => {}
Either::Right(_) => {
return Err(SwapFailed::AfterXmrLock {
reason: Reason::BtcExpired,
tx_lock_height,
})
}
Either::Right(_) => return Err(SwapFailed::AfterXmrLock(Reason::BtcExpired)),
};
Ok(())
@ -233,19 +218,8 @@ where
error!("swap failed: {:?}", err);
}
if let Err(SwapFailed::AfterXmrLock {
reason: Reason::BtcExpired,
tx_lock_height,
}) = swap_result
{
if let Err(SwapFailed::AfterXmrLock(Reason::BtcExpired)) = swap_result {
let refund_result: Result<(), RefundFailed> = async {
let poll_until_bob_can_be_punished = poll_until_block_height_is_gte(
bitcoin_client.as_ref(),
tx_lock_height + refund_timelock + punish_timelock,
)
.shared();
pin_mut!(poll_until_bob_can_be_punished);
let tx_cancel =
bitcoin::TxCancel::new(&tx_lock, refund_timelock, a.public(), B.clone());
let signed_tx_cancel = {
@ -260,19 +234,19 @@ where
co.yield_(Action::CancelBtc(signed_tx_cancel)).await;
match select(
bitcoin_client.watch_for_raw_transaction(tx_cancel.txid()),
poll_until_bob_can_be_punished.clone(),
bitcoin_client
.watch_for_raw_transaction(tx_cancel.txid())
.await;
let tx_cancel_height = bitcoin_client
.transaction_block_height(tx_cancel.txid())
.await;
let poll_until_bob_can_be_punished = poll_until_block_height_is_gte(
bitcoin_client.as_ref(),
tx_cancel_height + punish_timelock,
)
.await
{
Either::Left(_) => {}
Either::Right(_) => {
return Err(RefundFailed::BtcPunishable {
tx_cancel_was_published: false,
})
}
};
.shared();
pin_mut!(poll_until_bob_can_be_punished);
let tx_refund = bitcoin::TxRefund::new(&tx_cancel, &refund_address);
let tx_refund_published = match select(
@ -282,11 +256,7 @@ where
.await
{
Either::Left((tx, _)) => tx,
Either::Right(_) => {
return Err(RefundFailed::BtcPunishable {
tx_cancel_was_published: true,
});
}
Either::Right(_) => return Err(RefundFailed::BtcPunishable),
};
let s_a = monero::PrivateKey {
@ -321,32 +291,9 @@ where
// transaction with his refund transaction. Alice would then need to carry on
// with the refund on Monero. Doing so may be too verbose with the current,
// linear approach. A different design may be required
if let Err(RefundFailed::BtcPunishable {
tx_cancel_was_published,
}) = refund_result
{
if let Err(RefundFailed::BtcPunishable) = refund_result {
let tx_cancel =
bitcoin::TxCancel::new(&tx_lock, refund_timelock, a.public(), B.clone());
if !tx_cancel_was_published {
let tx_cancel_txid = tx_cancel.txid();
let signed_tx_cancel = {
let sig_a = a.sign(tx_cancel.digest());
let sig_b = tx_cancel_sig_bob;
tx_cancel
.clone()
.add_signatures(&tx_lock, (a.public(), sig_a), (B.clone(), sig_b))
.expect("sig_{a,b} to be valid signatures for tx_cancel")
};
co.yield_(Action::CancelBtc(signed_tx_cancel)).await;
let _ = bitcoin_client
.watch_for_raw_transaction(tx_cancel_txid)
.await;
}
let tx_punish =
bitcoin::TxPunish::new(&tx_cancel, &punish_address, punish_timelock);
let tx_punish_txid = tx_punish.txid();

4
xmr-btc/src/bob.rs
View file

@ -507,10 +507,10 @@ pub struct State2 {
btc: bitcoin::Amount,
pub xmr: monero::Amount,
pub refund_timelock: u32,
punish_timelock: u32,
pub punish_timelock: u32,
pub refund_address: bitcoin::Address,
pub redeem_address: bitcoin::Address,
punish_address: bitcoin::Address,
pub punish_address: bitcoin::Address,
pub tx_lock: bitcoin::TxLock,
pub tx_cancel_sig_a: Signature,
pub tx_refund_encsig: EncryptedSignature,