Complete route blinding support

lightning/src/ln/blinded_payment_tests.rs

@@ -490,6 +490,29 @@ fn two_hop_blinded_path_success() {
 	claim_payment(&nodes[0], &[&nodes[1], &nodes[2]], payment_preimage);
 }
 
+#[test]
+fn three_hop_blinded_path_success() {
+	let chanmon_cfgs = create_chanmon_cfgs(5);
+	let node_cfgs = create_node_cfgs(5, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(5, &node_cfgs, &[None, None, None, None, None]);
+	let mut nodes = create_network(5, &node_cfgs, &node_chanmgrs);
+	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);
+	create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0);
+	let chan_upd_2_3 = create_announced_chan_between_nodes_with_value(&nodes, 2, 3, 1_000_000, 0).0.contents;
+	let chan_upd_3_4 = create_announced_chan_between_nodes_with_value(&nodes, 3, 4, 1_000_000, 0).0.contents;
+
+	let amt_msat = 5000;
+	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[4], Some(amt_msat), None);
+	let route_params = get_blinded_route_parameters(amt_msat, payment_secret,
+		nodes.iter().skip(2).map(|n| n.node.get_our_node_id()).collect(),
+		&[&chan_upd_2_3, &chan_upd_3_4], &chanmon_cfgs[4].keys_manager);
+
+	nodes[0].node.send_payment(payment_hash, RecipientOnionFields::spontaneous_empty(), PaymentId(payment_hash.0), route_params, Retry::Attempts(0)).unwrap();
+	check_added_monitors(&nodes[0], 1);
+	pass_along_route(&nodes[0], &[&[&nodes[1], &nodes[2], &nodes[3], &nodes[4]]], amt_msat, payment_hash, payment_secret);
+	claim_payment(&nodes[0], &[&nodes[1], &nodes[2], &nodes[3], &nodes[4]], payment_preimage);
+}
+
 #[derive(PartialEq)]
 enum ReceiveCheckFail {
 	// The recipient fails the payment upon `PaymentClaimable`.
@@ -537,19 +560,20 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
 	};
 
 	let amt_msat = 5000;
-	let final_cltv_delta = if check == ReceiveCheckFail::ProcessPendingHTLCsCheck {
+	let excess_final_cltv_delta_opt = if check == ReceiveCheckFail::ProcessPendingHTLCsCheck {
 		// Set the final CLTV expiry too low to trigger the failure in process_pending_htlc_forwards.
 		Some(TEST_FINAL_CLTV as u16 - 2)
 	} else { None };
-	let (_, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[2], Some(amt_msat), final_cltv_delta);
+	let (_, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[2], Some(amt_msat), excess_final_cltv_delta_opt);
 	let mut route_params = get_blinded_route_parameters(amt_msat, payment_secret,
 		nodes.iter().skip(1).map(|n| n.node.get_our_node_id()).collect(), &[&chan_upd_1_2],
 		&chanmon_cfgs[2].keys_manager);
 
 	let route = if check == ReceiveCheckFail::ProcessPendingHTLCsCheck {
 		let mut route = get_route(&nodes[0], &route_params).unwrap();
 		// Set the final CLTV expiry too low to trigger the failure in process_pending_htlc_forwards.
-		route.paths[0].blinded_tail.as_mut().map(|bt| bt.excess_final_cltv_expiry_delta = TEST_FINAL_CLTV - 2);
+		route.paths[0].hops.last_mut().map(|h| h.cltv_expiry_delta += excess_final_cltv_delta_opt.unwrap() as u32);
+		route.paths[0].blinded_tail.as_mut().map(|bt| bt.excess_final_cltv_expiry_delta = excess_final_cltv_delta_opt.unwrap() as u32);
 		route
 	} else if check == ReceiveCheckFail::PaymentConstraints {
 		// Create a blinded path where the receiver's encrypted payload has an htlc_minimum_msat that is
@@ -657,6 +681,7 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
 			commitment_signed_dance!(nodes[2], nodes[1], (), false, true, false, false);
 		},
 		ReceiveCheckFail::ProcessPendingHTLCsCheck => {
+			assert_eq!(payment_event_1_2.msgs[0].cltv_expiry, nodes[0].best_block_info().1 + 1 + excess_final_cltv_delta_opt.unwrap() as u32);
 			nodes[2].node.handle_update_add_htlc(&nodes[1].node.get_our_node_id(), &payment_event_1_2.msgs[0]);
 			check_added_monitors!(nodes[2], 0);
 			do_commitment_signed_dance(&nodes[2], &nodes[1], &payment_event_1_2.commitment_msg, true, true);

lightning/src/ln/channelmanager.rs

@@ -202,15 +202,16 @@ pub struct BlindedForward {
 	/// onion payload if we're the introduction node. Useful for calculating the next hop's
 	/// [`msgs::UpdateAddHTLC::blinding_point`].
 	pub inbound_blinding_point: PublicKey,
-	// Another field will be added here when we support forwarding as a non-intro node.
+	/// If needed, this determines how this HTLC should be failed backwards, based on whether we are
+	/// the introduction node.
+	pub failure: BlindedFailure,
 }
 
 impl PendingHTLCRouting {
 	// Used to override the onion failure code and data if the HTLC is blinded.
 	fn blinded_failure(&self) -> Option<BlindedFailure> {
-		// TODO: needs update when we support forwarding blinded HTLCs as non-intro node
 		match self {
-			Self::Forward { blinded: Some(_), .. } => Some(BlindedFailure::FromIntroductionNode),
+			Self::Forward { blinded: Some(BlindedForward { failure, .. }), .. } => Some(*failure),
 			Self::Receive { requires_blinded_error: true, .. } => Some(BlindedFailure::FromBlindedNode),
 			_ => None,
 		}
@@ -305,10 +306,15 @@ pub(super) enum HTLCForwardInfo {
 	},
 }
 
-// Used for failing blinded HTLCs backwards correctly.
+/// Whether this blinded HTLC is being failed backwards by the introduction node or a blinded node,
+/// which determines the failure message that should be used.
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
-enum BlindedFailure {
+pub enum BlindedFailure {
+	/// This HTLC is being failed backwards by the introduction node, and thus should be failed with
+	/// [`msgs::UpdateFailHTLC`] and error code `0x8000|0x4000|24`.
 	FromIntroductionNode,
+	/// This HTLC is being failed backwards by a blinded node within the path, and thus should be
+	/// failed with [`msgs::UpdateFailMalformedHTLC`] and error code `0x8000|0x4000|24`.
 	FromBlindedNode,
 }
 
@@ -3024,8 +3030,9 @@ where
 
 		let is_intro_node_forward = match next_hop {
 			onion_utils::Hop::Forward {
-				// TODO: update this when we support blinded forwarding as non-intro node
-				next_hop_data: msgs::InboundOnionPayload::BlindedForward { .. }, ..
+				next_hop_data: msgs::InboundOnionPayload::BlindedForward {
+					intro_node_blinding_point: Some(_), ..
+				}, ..
 			} => true,
 			_ => false,
 		};
@@ -4370,7 +4377,7 @@ where
 										incoming_packet_shared_secret: incoming_shared_secret,
 										// Phantom payments are only PendingHTLCRouting::Receive.
 										phantom_shared_secret: None,
-										blinded_failure: blinded.map(|_| BlindedFailure::FromIntroductionNode),
+										blinded_failure: blinded.map(|b| b.failure),
 									});
 									let next_blinding_point = blinded.and_then(|b| {
 										let encrypted_tlvs_ss = self.node_signer.ecdh(
@@ -9350,6 +9357,7 @@ pub fn provided_init_features(config: &UserConfig) -> InitFeatures {
 	features.set_channel_type_optional();
 	features.set_scid_privacy_optional();
 	features.set_zero_conf_optional();
+	features.set_route_blinding_optional();
 	if config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx {
 		features.set_anchors_zero_fee_htlc_tx_optional();
 	}
@@ -9495,6 +9503,7 @@ impl_writeable_tlv_based!(PhantomRouteHints, {
 
 impl_writeable_tlv_based!(BlindedForward, {
 	(0, inbound_blinding_point, required),
+	(1, failure, (default_value, BlindedFailure::FromIntroductionNode)),
 });
 
 impl_writeable_tlv_based_enum!(PendingHTLCRouting,

lightning/src/ln/msgs.rs

@@ -1714,7 +1714,7 @@ mod fuzzy_internal_msgs {
 			payment_relay: PaymentRelay,
 			payment_constraints: PaymentConstraints,
 			features: BlindedHopFeatures,
-			intro_node_blinding_point: PublicKey,
+			intro_node_blinding_point: Option<PublicKey>,
 		},
 		BlindedReceive {
 			sender_intended_htlc_amt_msat: u64,
@@ -2394,7 +2394,7 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, &NS)> for InboundOnionPayload w
 						payment_relay,
 						payment_constraints,
 						features,
-						intro_node_blinding_point: intro_node_blinding_point.ok_or(DecodeError::InvalidValue)?,
+						intro_node_blinding_point,
 					})
 				},
 				ChaChaPolyReadAdapter { readable: BlindedPaymentTlvs::Receive(ReceiveTlvs {

lightning/src/ln/onion_payment.rs

@@ -12,7 +12,7 @@ use crate::blinded_path;
 use crate::blinded_path::payment::{PaymentConstraints, PaymentRelay};
 use crate::chain::channelmonitor::{HTLC_FAIL_BACK_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS};
 use crate::ln::PaymentHash;
-use crate::ln::channelmanager::{BlindedForward, CLTV_FAR_FAR_AWAY, HTLCFailureMsg, MIN_CLTV_EXPIRY_DELTA, PendingHTLCInfo, PendingHTLCRouting};
+use crate::ln::channelmanager::{BlindedFailure, BlindedForward, CLTV_FAR_FAR_AWAY, HTLCFailureMsg, MIN_CLTV_EXPIRY_DELTA, PendingHTLCInfo, PendingHTLCRouting};
 use crate::ln::features::BlindedHopFeatures;
 use crate::ln::msgs;
 use crate::ln::onion_utils;
@@ -73,7 +73,7 @@ pub(super) fn create_fwd_pending_htlc_info(
 	};
 
 	let (
-		short_channel_id, amt_to_forward, outgoing_cltv_value, inbound_blinding_point
+		short_channel_id, amt_to_forward, outgoing_cltv_value, intro_node_blinding_point
 	) = match hop_data {
 		msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
 			(short_channel_id, amt_to_forward, outgoing_cltv_value, None),
@@ -91,7 +91,7 @@ pub(super) fn create_fwd_pending_htlc_info(
 					err_data: vec![0; 32],
 				}
 			})?;
-			(short_channel_id, amt_to_forward, outgoing_cltv_value, Some(intro_node_blinding_point))
+			(short_channel_id, amt_to_forward, outgoing_cltv_value, intro_node_blinding_point)
 		},
 		msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
 			return Err(InboundHTLCErr {
@@ -105,7 +105,13 @@ pub(super) fn create_fwd_pending_htlc_info(
 		routing: PendingHTLCRouting::Forward {
 			onion_packet: outgoing_packet,
 			short_channel_id,
-			blinded: inbound_blinding_point.map(|bp| BlindedForward { inbound_blinding_point: bp }),
+			blinded: intro_node_blinding_point.or(msg.blinding_point)
+				.map(|bp| BlindedForward {
+					inbound_blinding_point: bp,
+					failure: intro_node_blinding_point
+						.map(|_| BlindedFailure::FromIntroductionNode)
+						.unwrap_or(BlindedFailure::FromBlindedNode),
+				}),
 		},
 		payment_hash: msg.payment_hash,
 		incoming_shared_secret: shared_secret,

lightning/src/ln/onion_utils.rs

@@ -188,11 +188,10 @@ pub(super) fn build_onion_payloads(path: &Path, total_msat: u64, mut recipient_o
 				for (i, blinded_hop) in hops.iter().enumerate() {
 					if i == hops.len() - 1 {
 						cur_value_msat += final_value_msat;
-						cur_cltv += excess_final_cltv_expiry_delta;
 						res.push(msgs::OutboundOnionPayload::BlindedReceive {
 							sender_intended_htlc_amt_msat: *final_value_msat,
 							total_msat,
-							cltv_expiry_height: cltv,
+							cltv_expiry_height: cur_cltv + excess_final_cltv_expiry_delta,
 							encrypted_tlvs: blinded_hop.encrypted_payload.clone(),
 							intro_node_blinding_point: blinding_point.take(),
 						});

lightning/src/ln/peer_handler.rs

@@ -305,6 +305,7 @@ impl ChannelMessageHandler for ErroringMessageHandler {
 		features.set_channel_type_optional();
 		features.set_scid_privacy_optional();
 		features.set_zero_conf_optional();
+		features.set_route_blinding_optional();
 		features
 	}