Merge pull request lightningdevkit#2576 from valentinewallace/2023-09-fix-outbound-bp-fail-ev

Fix `PaymentPathFailed::payment_failed_permanently` on blinded path fail

Author: TheBlueMatt

lightning/src/ln/onion_route_tests.rs

@@ -645,8 +645,34 @@ fn test_onion_failure() {
 		}, || nodes[2].node.fail_htlc_backwards(&payment_hash), false, None,
 		Some(NetworkUpdate::NodeFailure { node_id: route.paths[0].hops[1].pubkey, is_permanent: true }),
 		Some(channels[1].0.contents.short_channel_id));
-	run_onion_failure_test_with_fail_intercept("0-length channel update in UPDATE onion failure", 200, &nodes,
-		&route, &payment_hash, &payment_secret, |_msg| {}, |msg| {
+	run_onion_failure_test_with_fail_intercept("0-length channel update in intermediate node UPDATE onion failure",
+		100, &nodes, &route, &payment_hash, &payment_secret, |msg| {
+			msg.amount_msat -= 1;
+		}, |msg| {
+			let session_priv = SecretKey::from_slice(&[3; 32]).unwrap();
+			let onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
+			let mut decoded_err_packet = msgs::DecodedOnionErrorPacket {
+				failuremsg: vec![
+					0x10, 0x7, // UPDATE|7
+					0x0, 0x0 // 0-len channel update
+				],
+				pad: vec![0; 255 - 4 /* 4-byte error message */],
+				hmac: [0; 32],
+			};
+			let um = onion_utils::gen_um_from_shared_secret(&onion_keys[0].shared_secret.as_ref());
+			let mut hmac = HmacEngine::<Sha256>::new(&um);
+			hmac.input(&decoded_err_packet.encode()[32..]);
+			decoded_err_packet.hmac = Hmac::from_engine(hmac).into_inner();
+			msg.reason = onion_utils::encrypt_failure_packet(
+				&onion_keys[0].shared_secret.as_ref(), &decoded_err_packet.encode()[..])
+		}, || {}, true, Some(0x1000|7),
+		Some(NetworkUpdate::ChannelFailure {
+			short_channel_id: channels[1].0.contents.short_channel_id,
+			is_permanent: false,
+		}),
+		Some(channels[1].0.contents.short_channel_id));
+	run_onion_failure_test_with_fail_intercept("0-length channel update in final node UPDATE onion failure",
+		200, &nodes, &route, &payment_hash, &payment_secret, |_msg| {}, |msg| {
 			let session_priv = SecretKey::from_slice(&[3; 32]).unwrap();
 			let onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
 			let mut decoded_err_packet = msgs::DecodedOnionErrorPacket {

lightning/src/ln/onion_utils.rs

@@ -426,7 +426,7 @@ pub(super) fn build_first_hop_failure_packet(shared_secret: &[u8], failure_type:
 pub(crate) struct DecodedOnionFailure {
 	pub(crate) network_update: Option<NetworkUpdate>,
 	pub(crate) short_channel_id: Option<u64>,
-	pub(crate) payment_retryable: bool,
+	pub(crate) payment_failed_permanently: bool,
 	#[cfg(test)]
 	pub(crate) onion_error_code: Option<u16>,
 	#[cfg(test)]
@@ -444,7 +444,14 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 	} = htlc_source {
 		(path, session_priv, first_hop_htlc_msat)
 	} else { unreachable!() };
-	let mut res = None;
+
+	// Learnings from the HTLC failure to inform future payment retries and scoring.
+	struct FailureLearnings {
+		network_update: Option<NetworkUpdate>,
+		short_channel_id: Option<u64>,
+		payment_failed_permanently: bool,
+	}
+	let mut res: Option<FailureLearnings> = None;
 	let mut htlc_msat = *first_hop_htlc_msat;
 	let mut error_code_ret = None;
 	let mut error_packet_ret = None;
@@ -467,11 +474,33 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 				// Got an error from within a blinded route.
 				error_code_ret = Some(BADONION | PERM | 24); // invalid_onion_blinding
 				error_packet_ret = Some(vec![0; 32]);
-				is_from_final_node = false;
+				res = Some(FailureLearnings {
+					network_update: None, short_channel_id: None, payment_failed_permanently: false
+				});
 				return
 			},
 		};
 
+		// The failing hop includes either the inbound channel to the recipient or the outbound channel
+		// from the current hop (i.e., the next hop's inbound channel).
+		let num_blinded_hops = path.blinded_tail.as_ref().map_or(0, |bt| bt.hops.len());
+		// For 1-hop blinded paths, the final `path.hops` entry is the recipient.
+		is_from_final_node = route_hop_idx + 1 == path.hops.len() && num_blinded_hops <= 1;
+		let failing_route_hop = if is_from_final_node { route_hop } else {
+			match path.hops.get(route_hop_idx + 1) {
+				Some(hop) => hop,
+				None => {
+					// The failing hop is within a multi-hop blinded path.
+					error_code_ret = Some(BADONION | PERM | 24); // invalid_onion_blinding
+					error_packet_ret = Some(vec![0; 32]);
+					res = Some(FailureLearnings {
+						network_update: None, short_channel_id: None, payment_failed_permanently: false
+					});
+					return
+				}
+			}
+		};
+
 		let amt_to_forward = htlc_msat - route_hop.fee_msat;
 		htlc_msat = amt_to_forward;
 
@@ -483,11 +512,6 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 		chacha.process(&packet_decrypted, &mut decryption_tmp[..]);
 		packet_decrypted = decryption_tmp;
 
-		// The failing hop includes either the inbound channel to the recipient or the outbound channel
-		// from the current hop (i.e., the next hop's inbound channel).
-		is_from_final_node = route_hop_idx + 1 == path.hops.len();
-		let failing_route_hop = if is_from_final_node { route_hop } else { &path.hops[route_hop_idx + 1] };
-
 		let err_packet = match msgs::DecodedOnionErrorPacket::read(&mut Cursor::new(&packet_decrypted)) {
 			Ok(p) => p,
 			Err(_) => return
@@ -507,7 +531,9 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 					is_permanent: true,
 				});
 				let short_channel_id = Some(route_hop.short_channel_id);
-				res = Some((network_update, short_channel_id, !is_from_final_node));
+				res = Some(FailureLearnings {
+					network_update, short_channel_id, payment_failed_permanently: is_from_final_node
+				});
 				return
 			}
 		};
@@ -615,8 +641,9 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 							} else {
 								// The node in question intentionally encoded a 0-length channel update. This is
 								// likely due to https://github.com/ElementsProject/lightning/issues/6200.
+								short_channel_id = Some(failing_route_hop.short_channel_id);
 								network_update = Some(NetworkUpdate::ChannelFailure {
-									short_channel_id: route_hop.short_channel_id,
+									short_channel_id: failing_route_hop.short_channel_id,
 									is_permanent: false,
 								});
 							}
@@ -659,7 +686,10 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 			short_channel_id = Some(route_hop.short_channel_id);
 		}
 
-		res = Some((network_update, short_channel_id, !(error_code & PERM == PERM && is_from_final_node)));
+		res = Some(FailureLearnings {
+			network_update, short_channel_id,
+			payment_failed_permanently: error_code & PERM == PERM && is_from_final_node
+		});
 
 		let (description, title) = errors::get_onion_error_description(error_code);
 		if debug_field_size > 0 && err_packet.failuremsg.len() >= 4 + debug_field_size {
@@ -668,9 +698,11 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 			log_info!(logger, "Onion Error[from {}: {}({:#x})] {}", route_hop.pubkey, title, error_code, description);
 		}
 	}).expect("Route that we sent via spontaneously grew invalid keys in the middle of it?");
-	if let Some((network_update, short_channel_id, payment_retryable)) = res {
+	if let Some(FailureLearnings {
+		network_update, short_channel_id, payment_failed_permanently
+	}) = res {
 		DecodedOnionFailure {
-			network_update, short_channel_id, payment_retryable,
+			network_update, short_channel_id, payment_failed_permanently,
 			#[cfg(test)]
 			onion_error_code: error_code_ret,
 			#[cfg(test)]
@@ -680,7 +712,7 @@ pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
 		// only not set either packet unparseable or hmac does not match with any
 		// payment not retryable only when garbage is from the final node
 		DecodedOnionFailure {
-			network_update: None, short_channel_id: None, payment_retryable: !is_from_final_node,
+			network_update: None, short_channel_id: None, payment_failed_permanently: is_from_final_node,
 			#[cfg(test)]
 			onion_error_code: None,
 			#[cfg(test)]
@@ -824,7 +856,7 @@ impl HTLCFailReason {
 				if let &HTLCSource::OutboundRoute { ref path, .. } = htlc_source {
 					DecodedOnionFailure {
 						network_update: None,
-						payment_retryable: true,
+						payment_failed_permanently: false,
 						short_channel_id: Some(path.hops[0].short_channel_id),
 						#[cfg(test)]
 						onion_error_code: Some(*failure_code),

lightning/src/ln/outbound_payment.rs

@@ -1497,10 +1497,11 @@ impl OutboundPayments {
 	) -> bool where L::Target: Logger {
 		#[cfg(test)]
 		let DecodedOnionFailure {
-			network_update, short_channel_id, payment_retryable, onion_error_code, onion_error_data
+			network_update, short_channel_id, payment_failed_permanently, onion_error_code,
+			onion_error_data
 		} = onion_error.decode_onion_failure(secp_ctx, logger, &source);
 		#[cfg(not(test))]
-		let DecodedOnionFailure { network_update, short_channel_id, payment_retryable } =
+		let DecodedOnionFailure { network_update, short_channel_id, payment_failed_permanently } =
 			onion_error.decode_onion_failure(secp_ctx, logger, &source);
 
 		let payment_is_probe = payment_is_probe(payment_hash, &payment_id, probing_cookie_secret);
@@ -1541,8 +1542,8 @@ impl OutboundPayments {
 				payment.get_mut().insert_previously_failed_scid(scid);
 			}
 
-			if payment_is_probe || !is_retryable_now || !payment_retryable {
-				let reason = if !payment_retryable {
+			if payment_is_probe || !is_retryable_now || payment_failed_permanently {
+				let reason = if payment_failed_permanently {
 					PaymentFailureReason::RecipientRejected
 				} else {
 					PaymentFailureReason::RetriesExhausted
@@ -1572,7 +1573,7 @@ impl OutboundPayments {
 
 		let path_failure = {
 			if payment_is_probe {
-				if !payment_retryable {
+				if payment_failed_permanently {
 					events::Event::ProbeSuccessful {
 						payment_id: *payment_id,
 						payment_hash: payment_hash.clone(),
@@ -1596,7 +1597,7 @@ impl OutboundPayments {
 				events::Event::PaymentPathFailed {
 					payment_id: Some(*payment_id),
 					payment_hash: payment_hash.clone(),
-					payment_failed_permanently: !payment_retryable,
+					payment_failed_permanently,
 					failure: events::PathFailure::OnPath { network_update },
 					path: path.clone(),
 					short_channel_id,