Incoming chain swaps: refund only considers 1st UTXO

SatoshiPortal / boltz-rust

Boltz client rust crate

https://docs.boltz.exchange

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Incoming chain swaps: refund only considers 1st UTXO #72

Closed ok300 closed 1 week ago

ok300 commented 1 month ago

For incoming chain swaps (BTC -> LBTC), in case of address re-use (e.g. user locks up funds via several txs to the swap lockup address), the refund will only consider the 1st utxo. This means it's not possible to refund any of the subsequent utxos. It's also not possible to claim them, as the claim is also triggered for the 1st utxo.

There are several variants of this:

user sends funds several times to the lockup address, then tries to refund
user goes through a chain swap completely (which ends either with a claim or a refund), then sends funds again to the lockup address

In both cases, it would be useful if BtcSwapTx::new_refund would build a refund tx using all available utxos.

i5hi commented 1 month ago

Yes. Kind of related to this: https://github.com/SatoshiPortal/boltz-rust/issues/11

Although this is extremely rare, the library should handle such edge cases.

We should make fetch_utxos return a Vec<(Outpoint, TxOut)> rather than a single (Outpoint,Txout) and SwapTx to have utxos as a Vec rather than a single utxo

i5hi commented 1 month ago

Just noticed you have a PR for this too.

Nice! Reviewing it now.