Pathfind Trampoline forward and construct onion [rephrase]

Author: arik-so

lightning/src/ln/blinded_payment_tests.rs

@@ -2496,3 +2496,165 @@ fn test_trampoline_constraint_enforcement() {
 		expect_payment_failed_conditions(&nodes[0], payment_hash, false, payment_failed_conditions);
 	}
 }
+
+#[test]
+fn test_unblinded_trampoline_forward() {
+	// Simulate a payment of A (0) -> B (1) -> C(Trampoline) (2) -> D(Trampoline(receive)) (3)
+	// trampoline hops C -> T0 (4) -> D
+	// make it fail at B, then at C's outer onion, then at C's inner onion
+	const TOTAL_NODE_COUNT: usize = 5;
+	let secp_ctx = Secp256k1::new();
+
+	let chanmon_cfgs = create_chanmon_cfgs(TOTAL_NODE_COUNT);
+	let node_cfgs = create_node_cfgs(TOTAL_NODE_COUNT, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(TOTAL_NODE_COUNT, &node_cfgs, &vec![None; TOTAL_NODE_COUNT]);
+	let mut nodes = create_network(TOTAL_NODE_COUNT, &node_cfgs, &node_chanmgrs);
+
+	let (_, _, chan_id_alice_bob, _) = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);
+	let (_, _, chan_id_bob_carol, _) = create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0);
+	let (_, _, _, _) = create_announced_chan_between_nodes_with_value(&nodes, 2, 4, 1_000_000, 0);
+	let (_, _, _, _) = create_announced_chan_between_nodes_with_value(&nodes, 4, 3, 1_000_000, 0);
+
+	for i in 0..TOTAL_NODE_COUNT { // connect all nodes' blocks
+		connect_blocks(&nodes[i], (TOTAL_NODE_COUNT as u32) * CHAN_CONFIRM_DEPTH + 1 - nodes[i].best_block_info().1);
+	}
+
+	let alice_node_id = nodes[0].node().get_our_node_id();
+	let bob_node_id = nodes[1].node().get_our_node_id();
+	let carol_node_id = nodes[2].node().get_our_node_id();
+	let dave_node_id = nodes[3].node().get_our_node_id();
+
+	let alice_bob_scid = nodes[0].node().list_channels().iter().find(|c| c.channel_id == chan_id_alice_bob).unwrap().short_channel_id.unwrap();
+	let bob_carol_scid = nodes[1].node().list_channels().iter().find(|c| c.channel_id == chan_id_bob_carol).unwrap().short_channel_id.unwrap();
+
+	let amt_msat = 1000;
+	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[3], Some(amt_msat), None);
+
+	let route = Route {
+		paths: vec![Path {
+			hops: vec![
+				// Bob
+				RouteHop {
+					pubkey: bob_node_id,
+					node_features: NodeFeatures::empty(),
+					short_channel_id: alice_bob_scid,
+					channel_features: ChannelFeatures::empty(),
+					fee_msat: 1000, // forwarding fee to Carol
+					cltv_expiry_delta: 48,
+					maybe_announced_channel: false,
+				},
+
+				// Carol
+				RouteHop {
+					pubkey: carol_node_id,
+					node_features: NodeFeatures::empty(),
+					short_channel_id: bob_carol_scid,
+					channel_features: ChannelFeatures::empty(),
+					fee_msat: 2000, // fee for the usage of the entire blinded path, including Trampoline
+					cltv_expiry_delta: 48,
+					maybe_announced_channel: false,
+				}
+			],
+			blinded_tail: Some(BlindedTail {
+				trampoline_hops: vec![
+					// Carol
+					TrampolineHop {
+						pubkey: carol_node_id,
+						node_features: Features::empty(),
+						fee_msat: amt_msat,
+						cltv_expiry_delta: 176, // let her cook
+					},
+
+					// Dave (recipient)
+					TrampolineHop {
+						pubkey: dave_node_id,
+						node_features: Features::empty(),
+						fee_msat: 0, // no need to charge a fee as the recipient
+						cltv_expiry_delta: 24,
+					},
+				],
+				hops: vec![
+					// Dave's blinded node id
+					BlindedHop {
+						blinded_node_id: pubkey_from_hex("0295d40514096a8be54859e7dfe947b376eaafea8afe5cb4eb2c13ff857ed0b4be"),
+						encrypted_payload: bytes_from_hex("0ccf3c8a58deaa603f657ee2a5ed9d604eb5c8ca1e5f801989afa8f3ea6d789bbdde2c7e7a1ef9ca8c38d2c54760febad8446d3f273ddb537569ef56613846ccd3aba78a"),
+					}
+				],
+				blinding_point: alice_node_id,
+				excess_final_cltv_expiry_delta: 39,
+				final_value_msat: amt_msat,
+			})
+		}],
+		route_params: None,
+	};
+
+	nodes[0].node.send_payment_with_route(route.clone(), payment_hash, RecipientOnionFields::spontaneous_empty(), PaymentId(payment_hash.0)).unwrap();
+
+	let replacement_onion = {
+		// create a substitute onion where the last Trampoline hop is an unblinded receive, which we
+		// (deliberately) do not support out of the box, therefore necessitating this workaround
+		let trampoline_secret_key = secret_from_hex("0134928f7b7ca6769080d70f16be84c812c741f545b49a34db47ce338a205799");
+		let prng_seed = secret_from_hex("fe02b4b9054302a3ddf4e1e9f7c411d644aebbd295218ab009dca94435f775a9");
+		let recipient_onion_fields = RecipientOnionFields::spontaneous_empty();
+
+		let blinded_tail = route.paths[0].blinded_tail.clone().unwrap();
+		let (mut trampoline_payloads, outer_total_msat, outer_starting_htlc_offset) = onion_utils::build_trampoline_onion_payloads(&blinded_tail, amt_msat, &recipient_onion_fields, 32, &None).unwrap();
+
+		// pop the last dummy hop
+		trampoline_payloads.pop();
+
+		trampoline_payloads.push(msgs::OutboundTrampolinePayload::Receive {
+			payment_data: Some(msgs::FinalOnionHopData {
+				payment_secret,
+				total_msat: amt_msat,
+			}),
+			sender_intended_htlc_amt_msat: amt_msat,
+			cltv_expiry_height: 96,
+		});
+
+		let trampoline_onion_keys = onion_utils::construct_trampoline_onion_keys(&secp_ctx, &route.paths[0].blinded_tail.as_ref().unwrap(), &trampoline_secret_key).unwrap();
+		let trampoline_packet = onion_utils::construct_trampoline_onion_packet(
+			trampoline_payloads,
+			trampoline_onion_keys,
+			prng_seed.secret_bytes(),
+			&payment_hash,
+			None,
+		).unwrap();
+
+		let outer_session_priv = secret_from_hex("e52c20461ed7acd46c4e7b591a37610519179482887bd73bf3b94617f8f03677");
+
+		let (outer_payloads, _, _) = onion_utils::build_onion_payloads(&route.paths[0], outer_total_msat, &recipient_onion_fields, outer_starting_htlc_offset, &None, None, Some(trampoline_packet)).unwrap();
+		let outer_onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.clone().paths[0], &outer_session_priv).unwrap();
+		let outer_packet = onion_utils::construct_onion_packet(
+			outer_payloads,
+			outer_onion_keys,
+			prng_seed.secret_bytes(),
+			&payment_hash,
+		).unwrap();
+
+		outer_packet
+	};
+
+	check_added_monitors!(&nodes[0], 1);
+
+	let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+	assert_eq!(events.len(), 1);
+	let mut first_message_event = remove_first_msg_event_to_node(&nodes[1].node.get_our_node_id(), &mut events);
+	let mut update_message = match first_message_event {
+		MessageSendEvent::UpdateHTLCs { ref mut updates, .. } => {
+			assert_eq!(updates.update_add_htlcs.len(), 1);
+			updates.update_add_htlcs.get_mut(0)
+		},
+		_ => panic!()
+	};
+	update_message.map(|msg| {
+		msg.onion_routing_packet = replacement_onion.clone();
+	});
+
+	let route: &[&Node] = &[&nodes[1], &nodes[2], &nodes[4], &nodes[3]];
+	let args = PassAlongPathArgs::new(&nodes[0], route, amt_msat, payment_hash, first_message_event)
+		.with_payment_secret(payment_secret);
+	do_pass_along_path(args);
+
+	claim_payment(&nodes[0], &[&nodes[1], &nodes[2], &nodes[4], &nodes[3]], payment_preimage);
+}