Fix bug in check_spend_remote_htlc and let csv delays being user configurable

src/ln/channel.rs

@@ -18,7 +18,7 @@ use secp256k1;
 use ln::msgs;
 use ln::msgs::{DecodeError, OptionalField, LocalFeatures};
 use ln::channelmonitor::ChannelMonitor;
-use ln::channelmanager::{PendingHTLCStatus, HTLCSource, HTLCFailReason, HTLCFailureMsg, PendingForwardHTLCInfo, RAACommitmentOrder, PaymentPreimage, PaymentHash};
+use ln::channelmanager::{PendingHTLCStatus, HTLCSource, HTLCFailReason, HTLCFailureMsg, PendingForwardHTLCInfo, RAACommitmentOrder, PaymentPreimage, PaymentHash, BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
 use ln::chan_utils::{TxCreationKeys,HTLCOutputInCommitment,HTLC_SUCCESS_TX_WEIGHT,HTLC_TIMEOUT_TX_WEIGHT};
 use ln::chan_utils;
 use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
@@ -317,7 +317,7 @@ pub(super) struct Channel {
 	their_htlc_minimum_msat: u64,
 	our_htlc_minimum_msat: u64,
 	their_to_self_delay: u16,
-	//implied by BREAKDOWN_TIMEOUT: our_to_self_delay: u16,
+	our_to_self_delay: u16,
 	#[cfg(test)]
 	pub their_max_accepted_htlcs: u16,
 	#[cfg(not(test))]
@@ -347,14 +347,6 @@ pub const OUR_MAX_HTLCS: u16 = 50; //TODO
 /// on ice until the funding transaction gets more confirmations, but the LN protocol doesn't
 /// really allow for this, so instead we're stuck closing it out at that point.
 const UNCONF_THRESHOLD: u32 = 6;
-/// The amount of time we require our counterparty wait to claim their money (ie time between when
-/// we, or our watchtower, must check for them having broadcast a theft transaction).
-#[cfg(not(test))]
-const BREAKDOWN_TIMEOUT: u16 = 6 * 24 * 7; //TODO?
-#[cfg(test)]
-pub const BREAKDOWN_TIMEOUT: u16 = 6 * 24 * 7; //TODO?
-/// The amount of time we're willing to wait to claim money back to us
-const MAX_LOCAL_BREAKDOWN_TIMEOUT: u16 = 6 * 24 * 14;
 /// Exposing these two constants for use in test in ChannelMonitor
 pub const COMMITMENT_TX_BASE_WEIGHT: u64 = 724;
 pub const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
@@ -421,6 +413,9 @@ impl Channel {
 		if push_msat > channel_value_satoshis * 1000 {
 			return Err(APIError::APIMisuseError{err: "push value > channel value"});
 		}
+		if config.own_channel_config.our_to_self_delay < BREAKDOWN_TIMEOUT {
+			return Err(APIError::APIMisuseError{err: "Configured with an unreasonable our_to_self_delay putting user funds at risks"});
+		}
 
 
 		let background_feerate = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
@@ -432,7 +427,7 @@ impl Channel {
 
 		let secp_ctx = Secp256k1::new();
 		let channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key, &chan_keys.delayed_payment_base_key,
-		                                          &chan_keys.htlc_base_key, &chan_keys.payment_base_key, &keys_provider.get_shutdown_pubkey(), BREAKDOWN_TIMEOUT,
+		                                          &chan_keys.htlc_base_key, &chan_keys.payment_base_key, &keys_provider.get_shutdown_pubkey(), config.own_channel_config.our_to_self_delay,
 		                                          keys_provider.get_destination_script(), logger.clone());
 
 		Ok(Channel {
@@ -489,6 +484,7 @@ impl Channel {
 			their_htlc_minimum_msat: 0,
 			our_htlc_minimum_msat: Channel::derive_our_htlc_minimum_msat(feerate),
 			their_to_self_delay: 0,
+			our_to_self_delay: config.own_channel_config.our_to_self_delay,
 			their_max_accepted_htlcs: 0,
 			minimum_depth: 0, // Filled in in accept_channel
 
@@ -526,6 +522,10 @@ impl Channel {
 		let chan_keys = keys_provider.get_channel_keys(true);
 		let mut local_config = (*config).channel_options.clone();
 
+		if config.own_channel_config.our_to_self_delay < BREAKDOWN_TIMEOUT {
+			return Err(ChannelError::Close("Configured with an unreasonable our_to_self_delay putting user funds at risks"));
+		}
+
 		// Check sanity of message fields:
 		if msg.funding_satoshis >= MAX_FUNDING_SATOSHIS {
 			return Err(ChannelError::Close("funding value > 2^24"));
@@ -547,7 +547,7 @@ impl Channel {
 		}
 		Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
 
-		if msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
+		if msg.to_self_delay > config.peer_channel_config_limits.their_to_self_delay || msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
 			return Err(ChannelError::Close("They wanted our payments to be delayed by a needlessly long period"));
 		}
 		if msg.max_accepted_htlcs < 1 {
@@ -620,7 +620,7 @@ impl Channel {
 
 		let secp_ctx = Secp256k1::new();
 		let mut channel_monitor = ChannelMonitor::new(&chan_keys.revocation_base_key, &chan_keys.delayed_payment_base_key,
-		                                              &chan_keys.htlc_base_key, &chan_keys.payment_base_key, &keys_provider.get_shutdown_pubkey(), BREAKDOWN_TIMEOUT,
+		                                              &chan_keys.htlc_base_key, &chan_keys.payment_base_key, &keys_provider.get_shutdown_pubkey(), config.own_channel_config.our_to_self_delay,
 		                                              keys_provider.get_destination_script(), logger.clone());
 		channel_monitor.set_their_base_keys(&msg.htlc_basepoint, &msg.delayed_payment_basepoint);
 		channel_monitor.set_their_to_self_delay(msg.to_self_delay);
@@ -700,6 +700,7 @@ impl Channel {
 			their_htlc_minimum_msat: msg.htlc_minimum_msat,
 			our_htlc_minimum_msat: Channel::derive_our_htlc_minimum_msat(msg.feerate_per_kw as u64),
 			their_to_self_delay: msg.to_self_delay,
+			our_to_self_delay: config.own_channel_config.our_to_self_delay,
 			their_max_accepted_htlcs: msg.max_accepted_htlcs,
 			minimum_depth: config.own_channel_config.minimum_depth,
 
@@ -935,7 +936,7 @@ impl Channel {
 			log_trace!(self, "   ...including {} output with value {}", if local { "to_local" } else { "to_remote" }, value_to_a);
 			txouts.push((TxOut {
 				script_pubkey: chan_utils::get_revokeable_redeemscript(&keys.revocation_key,
-				                                                       if local { self.their_to_self_delay } else { BREAKDOWN_TIMEOUT },
+				                                                       if local { self.their_to_self_delay } else { self.our_to_self_delay },
 				                                                       &keys.a_delayed_payment_key).to_v0_p2wsh(),
 				value: value_to_a as u64
 			}, None));
@@ -1134,7 +1135,7 @@ impl Channel {
 	/// @local is used only to convert relevant internal structures which refer to remote vs local
 	/// to decide value of outputs and direction of HTLCs.
 	fn build_htlc_transaction(&self, prev_hash: &Sha256dHash, htlc: &HTLCOutputInCommitment, local: bool, keys: &TxCreationKeys, feerate_per_kw: u64) -> Transaction {
-		chan_utils::build_htlc_transaction(prev_hash, feerate_per_kw, if local { self.their_to_self_delay } else { BREAKDOWN_TIMEOUT }, htlc, &keys.a_delayed_payment_key, &keys.revocation_key)
+		chan_utils::build_htlc_transaction(prev_hash, feerate_per_kw, if local { self.their_to_self_delay } else { self.our_to_self_delay }, htlc, &keys.a_delayed_payment_key, &keys.revocation_key)
 	}
 
 	fn create_htlc_tx_signature(&self, tx: &Transaction, htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Result<(Script, Signature, bool), ChannelError> {
@@ -1388,7 +1389,7 @@ impl Channel {
 		if msg.htlc_minimum_msat >= (self.channel_value_satoshis - msg.channel_reserve_satoshis) * 1000 {
 			return Err(ChannelError::Close("Minimum htlc value is full channel value"));
 		}
-		if msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
+		if msg.to_self_delay > config.peer_channel_config_limits.their_to_self_delay || msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
 			return Err(ChannelError::Close("They wanted our payments to be delayed by a needlessly long period"));
 		}
 		if msg.max_accepted_htlcs < 1 {
@@ -3072,7 +3073,7 @@ impl Channel {
 			channel_reserve_satoshis: Channel::get_our_channel_reserve_satoshis(self.channel_value_satoshis),
 			htlc_minimum_msat: self.our_htlc_minimum_msat,
 			feerate_per_kw: fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background) as u32,
-			to_self_delay: BREAKDOWN_TIMEOUT,
+			to_self_delay: self.our_to_self_delay,
 			max_accepted_htlcs: OUR_MAX_HTLCS,
 			funding_pubkey: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.funding_key),
 			revocation_basepoint: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.revocation_base_key),
@@ -3105,7 +3106,7 @@ impl Channel {
 			channel_reserve_satoshis: Channel::get_our_channel_reserve_satoshis(self.channel_value_satoshis),
 			htlc_minimum_msat: self.our_htlc_minimum_msat,
 			minimum_depth: self.minimum_depth,
-			to_self_delay: BREAKDOWN_TIMEOUT,
+			to_self_delay: self.our_to_self_delay,
 			max_accepted_htlcs: OUR_MAX_HTLCS,
 			funding_pubkey: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.funding_key),
 			revocation_basepoint: PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.revocation_base_key),
@@ -3754,6 +3755,7 @@ impl Writeable for Channel {
 		self.their_htlc_minimum_msat.write(writer)?;
 		self.our_htlc_minimum_msat.write(writer)?;
 		self.their_to_self_delay.write(writer)?;
+		self.our_to_self_delay.write(writer)?;
 		self.their_max_accepted_htlcs.write(writer)?;
 		self.minimum_depth.write(writer)?;
 
@@ -3915,6 +3917,7 @@ impl<R : ::std::io::Read> ReadableArgs<R, Arc<Logger>> for Channel {
 		let their_htlc_minimum_msat = Readable::read(reader)?;
 		let our_htlc_minimum_msat = Readable::read(reader)?;
 		let their_to_self_delay = Readable::read(reader)?;
+		let our_to_self_delay = Readable::read(reader)?;
 		let their_max_accepted_htlcs = Readable::read(reader)?;
 		let minimum_depth = Readable::read(reader)?;
 
@@ -3992,6 +3995,7 @@ impl<R : ::std::io::Read> ReadableArgs<R, Arc<Logger>> for Channel {
 			their_htlc_minimum_msat,
 			our_htlc_minimum_msat,
 			their_to_self_delay,
+			our_to_self_delay,
 			their_max_accepted_htlcs,
 			minimum_depth,
 

src/ln/channelmanager.rs

@@ -341,6 +341,12 @@ pub struct ChannelManager {
 	logger: Arc<Logger>,
 }
 
+/// The amount of time we require our counterparty wait to claim their money (ie time between when
+/// we, or our watchtower, must check for them having broadcast a theft transaction).
+pub(crate) const BREAKDOWN_TIMEOUT: u16 = 6 * 24;
+/// The amount of time we're willing to wait to claim money back to us
+pub(crate) const MAX_LOCAL_BREAKDOWN_TIMEOUT: u16 = 6 * 24 * 7;
+
 /// The minimum number of blocks between an inbound HTLC's CLTV and the corresponding outbound
 /// HTLC's CLTV. This should always be a few blocks greater than channelmonitor::CLTV_CLAIM_BUFFER,
 /// ie the node we forwarded the payment on to should always have enough room to reliably time out

src/ln/channelmonitor.rs

@@ -1768,7 +1768,7 @@ impl ChannelMonitor {
 			None => return (None, None),
 			Some(their_delayed_payment_base_key) => ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &per_commitment_point, &their_delayed_payment_base_key)),
 		};
-		let redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.their_to_self_delay.unwrap(), &delayed_key);
+		let redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.our_to_self_delay, &delayed_key);
 		let revokeable_p2wsh = redeemscript.to_v0_p2wsh();
 		let htlc_txid = tx.txid(); //TODO: This is gonna be a performance bottleneck for watchtowers!
 

src/ln/functional_tests.rs

@@ -4,11 +4,11 @@
 
 use chain::transaction::OutPoint;
 use chain::chaininterface::{ChainListener, ChainWatchInterface};
-use chain::keysinterface::{KeysInterface, SpendableOutputDescriptor};
-use ln::channel::{COMMITMENT_TX_BASE_WEIGHT, COMMITMENT_TX_WEIGHT_PER_HTLC, BREAKDOWN_TIMEOUT};
-use ln::channelmanager::{ChannelManager,ChannelManagerReadArgs,HTLCForwardInfo,RAACommitmentOrder, PaymentPreimage, PaymentHash};
+use chain::keysinterface::{KeysInterface, SpendableOutputDescriptor, KeysManager};
+use ln::channel::{COMMITMENT_TX_BASE_WEIGHT, COMMITMENT_TX_WEIGHT_PER_HTLC};
+use ln::channelmanager::{ChannelManager,ChannelManagerReadArgs,HTLCForwardInfo,RAACommitmentOrder, PaymentPreimage, PaymentHash, BREAKDOWN_TIMEOUT};
 use ln::channelmonitor::{ChannelMonitor, CLTV_CLAIM_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS, ManyChannelMonitor, ANTI_REORG_DELAY};
-use ln::channel::{ACCEPTED_HTLC_SCRIPT_WEIGHT, OFFERED_HTLC_SCRIPT_WEIGHT};
+use ln::channel::{ACCEPTED_HTLC_SCRIPT_WEIGHT, OFFERED_HTLC_SCRIPT_WEIGHT, Channel, ChannelError};
 use ln::onion_utils;
 use ln::router::{Route, RouteHop};
 use ln::msgs;
@@ -1727,7 +1727,15 @@ fn channel_monitor_network_test() {
 fn test_justice_tx() {
 	// Test justice txn built on revoked HTLC-Success tx, against both sides
 
-	let nodes = create_network(2, &[None, None]);
+	let mut alice_config = UserConfig::new();
+	alice_config.channel_options.announced_channel = true;
+	alice_config.peer_channel_config_limits.force_announced_channel_preference = false;
+	alice_config.own_channel_config.our_to_self_delay = 6 * 24 * 5;
+	let mut bob_config = UserConfig::new();
+	bob_config.channel_options.announced_channel = true;
+	bob_config.peer_channel_config_limits.force_announced_channel_preference = false;
+	bob_config.own_channel_config.our_to_self_delay = 6 * 24 * 3;
+	let nodes = create_network(2, &[Some(alice_config), Some(bob_config)]);
 	// Create some new channels:
 	let chan_5 = create_announced_chan_between_nodes(&nodes, 0, 1, LocalFeatures::new(), LocalFeatures::new());
 
@@ -5879,3 +5887,61 @@ fn test_upfront_shutdown_script() {
 		_ => panic!("Unexpected event"),
 	}
 }
+
+#[test]
+fn test_user_configurable_csv_delay() {
+	// We test our channel constructors yield errors when we pass them absurd csv delay
+
+	let mut low_our_to_self_config = UserConfig::new();
+	low_our_to_self_config.own_channel_config.our_to_self_delay = 6;
+	let mut high_their_to_self_config = UserConfig::new();
+	high_their_to_self_config.peer_channel_config_limits.their_to_self_delay = 100;
+	let nodes = create_network(2, &[Some(high_their_to_self_config.clone()), None]);
+
+	// We test config.our_to_self > BREAKDOWN_TIMEOUT is enforced in Channel::new_outbound()
+	let keys_manager: Arc<KeysInterface> = Arc::new(KeysManager::new(&nodes[0].node_seed, Network::Testnet, Arc::new(test_utils::TestLogger::new()), 10, 20));
+	if let Err(error) = Channel::new_outbound(&test_utils::TestFeeEstimator { sat_per_kw: 253 }, &keys_manager, nodes[1].node.get_our_node_id(), 1000000, 1000000, 0, Arc::new(test_utils::TestLogger::new()), &low_our_to_self_config) {
+		match error {
+			APIError::APIMisuseError { err } => { assert_eq!(err, "Configured with an unreasonable our_to_self_delay putting user funds at risks"); },
+			_ => panic!("Unexpected event"),
+		}
+	} else { assert!(false) }
+
+	// We test config.our_to_self > BREAKDOWN_TIMEOUT is enforced in Channel::new_from_req()
+	nodes[1].node.create_channel(nodes[0].node.get_our_node_id(), 1000000, 1000000, 42).unwrap();
+	let mut open_channel = get_event_msg!(nodes[1], MessageSendEvent::SendOpenChannel, nodes[0].node.get_our_node_id());
+	open_channel.to_self_delay = 200;
+	if let Err(error) = Channel::new_from_req(&test_utils::TestFeeEstimator { sat_per_kw: 253 }, &keys_manager, nodes[1].node.get_our_node_id(), LocalFeatures::new(), &open_channel, 0, Arc::new(test_utils::TestLogger::new()), &low_our_to_self_config) {
+		match error {
+			ChannelError::Close(err) => { assert_eq!(err, "Configured with an unreasonable our_to_self_delay putting user funds at risks"); },
+			_ => panic!("Unexpected event"),
+		}
+	} else { assert!(false); }
+
+	// We test msg.to_self_delay <= config.their_to_self_delay is enforced in Chanel::accept_channel()
+	nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), 1000000, 1000000, 42).unwrap();
+	nodes[1].node.handle_open_channel(&nodes[0].node.get_our_node_id(), LocalFeatures::new(), &get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id())).unwrap();
+	let mut accept_channel = get_event_msg!(nodes[1], MessageSendEvent::SendAcceptChannel, nodes[0].node.get_our_node_id());
+	accept_channel.to_self_delay = 200;
+	if let Err(error) = nodes[0].node.handle_accept_channel(&nodes[1].node.get_our_node_id(), LocalFeatures::new(), &accept_channel) {
+		if let Some(error) = error.action {
+			match error {
+				ErrorAction::SendErrorMessage { msg } => {
+					assert_eq!(msg.data,"They wanted our payments to be delayed by a needlessly long period");
+				},
+				_ => { assert!(false); }
+			}
+		} else { assert!(false); }
+	} else { assert!(false); }
+
+	// We test msg.to_self_delay <= config.their_to_self_delay is enforced in Channel::new_from_req()
+	nodes[1].node.create_channel(nodes[0].node.get_our_node_id(), 1000000, 1000000, 42).unwrap();
+	let mut open_channel = get_event_msg!(nodes[1], MessageSendEvent::SendOpenChannel, nodes[0].node.get_our_node_id());
+	open_channel.to_self_delay = 200;
+	if let Err(error) = Channel::new_from_req(&test_utils::TestFeeEstimator { sat_per_kw: 253 }, &keys_manager, nodes[1].node.get_our_node_id(), LocalFeatures::new(), &open_channel, 0, Arc::new(test_utils::TestLogger::new()), &high_their_to_self_config) {
+		match error {
+			ChannelError::Close(err) => { assert_eq!(err, "They wanted our payments to be delayed by a needlessly long period"); },
+			_ => panic!("Unexpected event"),
+		}
+	} else { assert!(false); }
+}

src/util/config.rs

@@ -1,6 +1,8 @@
 //! Various user-configurable channel limits and settings which ChannelManager
 //! applies for you.
 
+use ln::channelmanager::{BREAKDOWN_TIMEOUT, MAX_LOCAL_BREAKDOWN_TIMEOUT};
+
 /// Top-level config which holds ChannelHandshakeLimits and ChannelConfig.
 #[derive(Clone, Debug)]
 pub struct UserConfig {
@@ -30,13 +32,26 @@ pub struct ChannelHandshakeConfig {
 	/// Applied only for inbound channels (see ChannelHandshakeLimits::max_minimum_depth for the
 	/// equivalent limit applied to outbound channels).
 	pub minimum_depth: u32,
+	/// Set to the amount of time we require our counterparty to wait to claim their money.
+	///
+	/// It's one of the main parameter of our security model. We (or one of our watchtowers) MUST
+	/// be online to check for peer having broadcast a revoked transaction to steal our funds
+	/// at least once every our_to_self_delay blocks.
+	/// Default is BREAKDOWN_TIMEOUT, we enforce it as a minimum at channel opening so you can
+	/// tweak config to ask for more security, not less.
+	///
+	/// Meanwhile, asking for a too high delay, we bother peer to freeze funds for nothing in
+	/// case of an honest unilateral channel close, which implicitly decrease the economic value of
+	/// our channel.
+	pub our_to_self_delay: u16,
 }
 
 impl ChannelHandshakeConfig {
 	/// Provides sane defaults for `ChannelHandshakeConfig`
 	pub fn new() -> ChannelHandshakeConfig {
 		ChannelHandshakeConfig {
 			minimum_depth: 6,
+			our_to_self_delay: BREAKDOWN_TIMEOUT,
 		}
 	}
 }
@@ -88,6 +103,13 @@ pub struct ChannelHandshakeLimits {
 	/// Defaults to true to make the default that no announced channels are possible (which is
 	/// appropriate for any nodes which are not online very reliably).
 	pub force_announced_channel_preference: bool,
+	/// Set to the amount of time we're willing to wait to claim money back to us.
+	///
+	/// Not checking this value would be a security issue, as our peer would be able to set it to
+	/// max relative lock-time (a year) and we would "lose" money as it would be locked for a long time.
+	/// Default is MAX_LOCAL_BREAKDOWN_TIMEOUT, which we also enforce as a maximum value
+	/// so you can tweak config to reduce the loss of having useless locked funds (if your peer accepts)
+	pub their_to_self_delay: u16
 }
 
 impl ChannelHandshakeLimits {
@@ -107,6 +129,7 @@ impl ChannelHandshakeLimits {
 			max_dust_limit_satoshis: <u64>::max_value(),
 			max_minimum_depth: 144,
 			force_announced_channel_preference: true,
+			their_to_self_delay: MAX_LOCAL_BREAKDOWN_TIMEOUT,
 		}
 	}
 }