Reject oversized splice-out amounts

src/lib.rs

@@ -1700,7 +1700,9 @@ impl Node {
 		if let Some(channel_details) =
 			open_channels.iter().find(|c| c.user_channel_id == user_channel_id.0)
 		{
-			if splice_amount_sats > channel_details.outbound_capacity_msat {
+			let splice_amount_msat =
+				splice_amount_sats.checked_mul(1_000).ok_or(Error::ChannelSplicingFailed)?;
+			if splice_amount_msat > channel_details.outbound_capacity_msat {
 				return Err(Error::ChannelSplicingFailed);
 			}
 

tests/common/mod.rs

@@ -1364,7 +1364,9 @@ pub(crate) async fn do_channel_full_cycle<E: ElectrumApi>(
 
 	println!("\nB splices out to pay A");
 	let addr_a = node_a.onchain_payment().new_address().unwrap();
-	let splice_out_sat = funding_amount_sat / 2;
+	let available_splice_out_sat = node_b.list_channels()[0].outbound_capacity_msat / 1000;
+	let splice_out_sat = available_splice_out_sat / 2;
+	assert!(splice_out_sat > 500_000);
 	node_b.splice_out(&user_channel_id_b, node_a.node_id(), &addr_a, splice_out_sat).unwrap();
 
 	expect_splice_negotiated_event!(node_a, node_b.node_id());

tests/integration_tests_rust.rs

@@ -1036,6 +1036,18 @@ async fn splice_channel() {
 	);
 	assert_eq!(node_b.list_balances().total_lightning_balance_sats, 0);
 
+	let address = node_a.onchain_payment().new_address().unwrap();
+	let excessive_splice_out_sats = node_a.list_channels()[0].outbound_capacity_msat / 1000 + 1;
+	assert_eq!(
+		node_a.splice_out(
+			&user_channel_id_a,
+			node_b.node_id(),
+			&address,
+			excessive_splice_out_sats
+		),
+		Err(NodeError::ChannelSplicingFailed),
+	);
+
 	// Test that splicing and payments fail when there are insufficient funds
 	let address = node_b.onchain_payment().new_address().unwrap();
 	let amount_msat = 400_000_000;