Prevent any update of local commitment transaction once signed

[rust-lightning] / lightning / src / ln / channelmonitor.rs

diff --git a/lightning/src/ln/channelmonitor.rs b/lightning/src/ln/channelmonitor.rs
index 70c92143af8b50d58eb06f9c10878fc6fe190e2d..2fa416edb2dd79f26c8c0f5433b31e60c135bc2b 100644 (file)
--- a/lightning/src/ln/channelmonitor.rs
+++ b/lightning/src/ln/channelmonitor.rs
@@ -1241,10 +1241,18 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
                if self.their_to_self_delay.is_none() {
                        return Err(MonitorUpdateError("Got a local commitment tx info update before we'd set basic information about the channel"));
                }
+               // Returning a monitor error before updating tracking points means in case of using
+               // a concurrent watchtower implementation for same channel, if this one doesn't
+               // reject update as we do, you MAY have the latest local valid commitment tx onchain
+               // for which you want to spend outputs. We're NOT robust again this scenario right
+               // now but we should consider it later.
+               if let Err(_) = self.onchain_tx_handler.provide_latest_local_tx(commitment_tx.clone()) {
+                       return Err(MonitorUpdateError("Local commitment signed has already been signed, no further update of LOCAL commitment transaction is allowed"));
+               }
                self.prev_local_signed_commitment_tx = self.current_local_signed_commitment_tx.take();
                self.current_local_signed_commitment_tx = Some(LocalSignedTx {
                        txid: commitment_tx.txid(),
-                       tx: commitment_tx.clone(),
+                       tx: commitment_tx,
                        revocation_key: local_keys.revocation_key,
                        a_htlc_key: local_keys.a_htlc_key,
                        b_htlc_key: local_keys.b_htlc_key,
@@ -1253,7 +1261,6 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
                        feerate_per_kw,
                        htlc_outputs,
                });
-               self.onchain_tx_handler.provide_latest_local_tx(commitment_tx);
                Ok(())
        }