}
/// Attempts to claim a counterparty HTLC-Success/HTLC-Timeout's outputs using the revocation key
- fn check_spend_counterparty_htlc<L: Deref>(&mut self, tx: &Transaction, commitment_number: u64, height: u32, logger: &L) -> (Vec<PackageTemplate>, Option<TransactionOutputs>) where L::Target: Logger {
- let htlc_txid = tx.txid();
- if tx.input.len() != 1 || tx.output.len() != 1 || tx.input[0].witness.len() != 5 {
- return (Vec::new(), None)
- }
-
- macro_rules! ignore_error {
- ( $thing : expr ) => {
- match $thing {
- Ok(a) => a,
- Err(_) => return (Vec::new(), None)
- }
- };
- }
-
+ fn check_spend_counterparty_htlc<L: Deref>(
+ &mut self, tx: &Transaction, commitment_number: u64, commitment_txid: &Txid, height: u32, logger: &L
+ ) -> (Vec<PackageTemplate>, Option<TransactionOutputs>) where L::Target: Logger {
let secret = if let Some(secret) = self.get_secret(commitment_number) { secret } else { return (Vec::new(), None); };
- let per_commitment_key = ignore_error!(SecretKey::from_slice(&secret));
+ let per_commitment_key = match SecretKey::from_slice(&secret) {
+ Ok(key) => key,
+ Err(_) => return (Vec::new(), None)
+ };
let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);
- log_error!(logger, "Got broadcast of revoked counterparty HTLC transaction, spending {}:{}", htlc_txid, 0);
- let revk_outp = RevokedOutput::build(per_commitment_point, self.counterparty_commitment_params.counterparty_delayed_payment_base_key, self.counterparty_commitment_params.counterparty_htlc_base_key, per_commitment_key, tx.output[0].value, self.counterparty_commitment_params.on_counterparty_tx_csv);
- let justice_package = PackageTemplate::build_package(htlc_txid, 0, PackageSolvingData::RevokedOutput(revk_outp), height + self.counterparty_commitment_params.on_counterparty_tx_csv as u32, true, height);
- let claimable_outpoints = vec!(justice_package);
- let outputs = vec![(0, tx.output[0].clone())];
- (claimable_outpoints, Some((htlc_txid, outputs)))
+ let htlc_txid = tx.txid();
+ let mut claimable_outpoints = vec![];
+ let mut outputs_to_watch = None;
+ // Previously, we would only claim HTLCs from revoked HTLC transactions if they had 1 input
+ // with a witness of 5 elements and 1 output. This wasn't enough for anchor outputs, as the
+ // counterparty can now aggregate multiple HTLCs into a single transaction thanks to
+ // `SIGHASH_SINGLE` remote signatures, leading us to not claim any HTLCs upon seeing a
+ // confirmed revoked HTLC transaction (for more details, see
+ // https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-April/003561.html).
+ //
+ // We make sure we're not vulnerable to this case by checking all inputs of the transaction,
+ // and claim those which spend the commitment transaction, have a witness of 5 elements, and
+ // have a corresponding output at the same index within the transaction.
+ for (idx, input) in tx.input.iter().enumerate() {
+ if input.previous_output.txid == *commitment_txid && input.witness.len() == 5 && tx.output.get(idx).is_some() {
+ log_error!(logger, "Got broadcast of revoked counterparty HTLC transaction, spending {}:{}", htlc_txid, idx);
+ let revk_outp = RevokedOutput::build(
+ per_commitment_point, self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
+ self.counterparty_commitment_params.counterparty_htlc_base_key, per_commitment_key,
+ tx.output[idx].value, self.counterparty_commitment_params.on_counterparty_tx_csv
+ );
+ let justice_package = PackageTemplate::build_package(
+ htlc_txid, idx as u32, PackageSolvingData::RevokedOutput(revk_outp),
+ height + self.counterparty_commitment_params.on_counterparty_tx_csv as u32, true, height
+ );
+ claimable_outpoints.push(justice_package);
+ if outputs_to_watch.is_none() {
+ outputs_to_watch = Some((htlc_txid, vec![]));
+ }
+ outputs_to_watch.as_mut().unwrap().1.push((idx as u32, tx.output[idx].clone()));
+ }
+ }
+ (claimable_outpoints, outputs_to_watch)
}
// Returns (1) `PackageTemplate`s that can be given to the OnchainTxHandler, so that the handler can
if tx.input.len() == 1 {
// Assuming our keys were not leaked (in which case we're screwed no matter what),
- // commitment transactions and HTLC transactions will all only ever have one input,
- // which is an easy way to filter out any potential non-matching txn for lazy
- // filters.
+ // commitment transactions and HTLC transactions will all only ever have one input
+ // (except for HTLC transactions for channels with anchor outputs), which is an easy
+ // way to filter out any potential non-matching txn for lazy filters.
let prevout = &tx.input[0].previous_output;
if prevout.txid == self.funding_info.0.txid && prevout.vout == self.funding_info.0.index as u32 {
let mut balance_spendable_csv = None;
commitment_tx_to_counterparty_output,
},
});
- } else {
- if let Some(&commitment_number) = self.counterparty_commitment_txn_on_chain.get(&prevout.txid) {
- let (mut new_outpoints, new_outputs_option) = self.check_spend_counterparty_htlc(&tx, commitment_number, height, &logger);
+ }
+ }
+ if tx.input.len() >= 1 {
+ // While all commitment transactions have one input, HTLC transactions may have more
+ // if the HTLC was present in an anchor channel. HTLCs can also be resolved in a few
+ // other ways which can have more than one output.
+ for tx_input in &tx.input {
+ let commitment_txid = tx_input.previous_output.txid;
+ if let Some(&commitment_number) = self.counterparty_commitment_txn_on_chain.get(&commitment_txid) {
+ let (mut new_outpoints, new_outputs_option) = self.check_spend_counterparty_htlc(
+ &tx, commitment_number, &commitment_txid, height, &logger
+ );
claimable_outpoints.append(&mut new_outpoints);
if let Some(new_outputs) = new_outputs_option {
watch_outputs.push(new_outputs);
}
+ // Since there may be multiple HTLCs (all from the same commitment) being
+ // claimed by the counterparty within the same transaction, and
+ // `check_spend_counterparty_htlc` already checks for all of them, we can
+ // safely break from our loop.
+ break;
}
}
- }
- // While all commitment/HTLC-Success/HTLC-Timeout transactions have one input, HTLCs
- // can also be resolved in a few other ways which can have more than one output. Thus,
- // we call is_resolving_htlc_output here outside of the tx.input.len() == 1 check.
- self.is_resolving_htlc_output(&tx, height, &block_hash, &logger);
+ self.is_resolving_htlc_output(&tx, height, &block_hash, &logger);
- self.is_paying_spendable_output(&tx, height, &block_hash, &logger);
+ self.is_paying_spendable_output(&tx, height, &block_hash, &logger);
+ }
}
if height > self.best_block.height() {
projects / rust-lightning / commitdiff