Update Payment Tlvs to also contain the Option<Padding>

Co-authored-by: Jeffrey Czyz <[email protected]>

lightning/src/blinded_path/payment.rs

@@ -14,7 +14,7 @@
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
 
 use crate::blinded_path::{BlindedHop, BlindedPath, IntroductionNode, NodeIdLookUp};
-use crate::blinded_path::utils;
+use crate::blinded_path::utils::{self, Padding};
 use crate::crypto::streams::ChaChaPolyReadAdapter;
 use crate::io;
 use crate::io::Cursor;
@@ -50,6 +50,8 @@ pub struct ForwardNode {
 /// Data to construct a [`BlindedHop`] for forwarding a payment.
 #[derive(Clone, Debug)]
 pub struct ForwardTlvs {
+	/// The padding data used to make all packets of a Blinded Path of same size
+	pub padding: Option<Padding>,
 	/// The short channel id this payment should be forwarded out over.
 	pub short_channel_id: u64,
 	/// Payment parameters for relaying over [`Self::short_channel_id`].
@@ -67,6 +69,8 @@ pub struct ForwardTlvs {
 /// may not be valid if received by another lightning implementation.
 #[derive(Clone, Debug)]
 pub struct ReceiveTlvs {
+	/// The padding data used to make all packets of a Blinded Path of same size
+	pub padding: Option<Padding>,
 	/// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
 	pub payment_secret: PaymentSecret,
 	/// Constraints for the receiver of this payment.
@@ -78,13 +82,29 @@ pub struct ReceiveTlvs {
 /// Data to construct a [`BlindedHop`] for sending a payment over.
 ///
 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
+#[derive(Clone)]
 pub(crate) enum BlindedPaymentTlvs {
 	/// This blinded payment data is for a forwarding node.
 	Forward(ForwardTlvs),
 	/// This blinded payment data is for the receiving node.
 	Receive(ReceiveTlvs),
 }
 
+impl BlindedPaymentTlvs {
+	pub(crate) fn pad_to_length(mut self, length: usize) -> Self {
+		let pad_length = length.checked_sub(self.serialized_length());
+		debug_assert!(pad_length.is_some(), "Size of this packet should not be larger than the size of largest packet.");
+		let padding = Some(Padding::new(pad_length.unwrap()));
+
+		match &mut self {
+			BlindedPaymentTlvs::Forward(tlvs) => tlvs.padding = padding,
+			BlindedPaymentTlvs::Receive(tlvs) => tlvs.padding = padding,
+		}
+
+		self
+	}
+}
+
 /// Parameters for relaying over a given [`BlindedHop`].
 ///
 /// [`BlindedHop`]: crate::blinded_path::BlindedHop
@@ -198,6 +218,7 @@ impl Writeable for ForwardTlvs {
 			if self.features == BlindedHopFeatures::empty() { None }
 			else { Some(&self.features) };
 		encode_tlv_stream!(w, {
+			(1, self.padding, option),
 			(2, self.short_channel_id, required),
 			(10, self.payment_relay, required),
 			(12, self.payment_constraints, required),
@@ -210,6 +231,7 @@ impl Writeable for ForwardTlvs {
 impl Writeable for ReceiveTlvs {
 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 		encode_tlv_stream!(w, {
+			(1, self.padding, option),
 			(12, self.payment_constraints, required),
 			(65536, self.payment_secret, required),
 			(65537, self.payment_context, required)
@@ -246,6 +268,7 @@ impl Readable for BlindedPaymentTlvs {
 				return Err(DecodeError::InvalidValue)
 			}
 			Ok(BlindedPaymentTlvs::Forward(ForwardTlvs {
+				padding: None,
 				short_channel_id,
 				payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
 				payment_constraints: payment_constraints.0.unwrap(),
@@ -254,6 +277,7 @@ impl Readable for BlindedPaymentTlvs {
 		} else {
 			if payment_relay.is_some() || features.is_some() { return Err(DecodeError::InvalidValue) }
 			Ok(BlindedPaymentTlvs::Receive(ReceiveTlvs {
+				padding: None,
 				payment_secret: payment_secret.ok_or(DecodeError::InvalidValue)?,
 				payment_constraints: payment_constraints.0.unwrap(),
 				payment_context: payment_context.0.unwrap(),
@@ -272,7 +296,14 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 	let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvs::Forward(node.tlvs.clone()))
 		.chain(core::iter::once(BlindedPaymentTlvs::Receive(payee_tlvs)));
 
-	utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
+	let max_length = tlvs.clone()
+		.map(|tlv| tlv.serialized_length())
+		.max()
+		.unwrap_or(0);
+
+	let length_tlvs = tlvs.map(|tlv| tlv.pad_to_length(max_length));
+
+	utils::construct_blinded_hops(secp_ctx, pks, length_tlvs, session_priv)
 }
 
 // Advance the blinded onion payment path by one hop, so make the second hop into the new
@@ -484,6 +515,7 @@ mod tests {
 		let intermediate_nodes = vec![ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 144,
@@ -500,6 +532,7 @@ mod tests {
 		}, ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 144,
@@ -515,6 +548,7 @@ mod tests {
 			htlc_maximum_msat: u64::max_value(),
 		}];
 		let recv_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret: PaymentSecret([0; 32]),
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry: 0,
@@ -534,6 +568,7 @@ mod tests {
 	#[test]
 	fn compute_payinfo_1_hop() {
 		let recv_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret: PaymentSecret([0; 32]),
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry: 0,
@@ -557,6 +592,7 @@ mod tests {
 		let intermediate_nodes = vec![ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -573,6 +609,7 @@ mod tests {
 		}, ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -588,6 +625,7 @@ mod tests {
 			htlc_maximum_msat: u64::max_value()
 		}];
 		let recv_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret: PaymentSecret([0; 32]),
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry: 0,
@@ -608,6 +646,7 @@ mod tests {
 		let intermediate_nodes = vec![ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -624,6 +663,7 @@ mod tests {
 		}, ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -639,6 +679,7 @@ mod tests {
 			htlc_maximum_msat: u64::max_value()
 		}];
 		let recv_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret: PaymentSecret([0; 32]),
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry: 0,
@@ -663,6 +704,7 @@ mod tests {
 		let intermediate_nodes = vec![ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -679,6 +721,7 @@ mod tests {
 		}, ForwardNode {
 			node_id: dummy_pk,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: 0,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: 0,
@@ -694,6 +737,7 @@ mod tests {
 			htlc_maximum_msat: 10_000
 		}];
 		let recv_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret: PaymentSecret([0; 32]),
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry: 0,

lightning/src/ln/blinded_payment_tests.rs

@@ -39,6 +39,7 @@ fn blinded_payment_path(
 		intermediate_nodes.push(ForwardNode {
 			node_id: *node_id,
 			tlvs: ForwardTlvs {
+				padding: None,
 				short_channel_id: chan_upd.short_channel_id,
 				payment_relay: PaymentRelay {
 					cltv_expiry_delta: chan_upd.cltv_expiry_delta,
@@ -57,6 +58,7 @@ fn blinded_payment_path(
 		});
 	}
 	let payee_tlvs = ReceiveTlvs {
+		padding: None,
 		payment_secret,
 		payment_constraints: PaymentConstraints {
 			max_cltv_expiry: u32::max_value(),
@@ -104,6 +106,7 @@ fn do_one_hop_blinded_path(success: bool) {
 	let amt_msat = 5000;
 	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[1], Some(amt_msat), None);
 	let payee_tlvs = ReceiveTlvs {
+		padding: None,
 		payment_secret,
 		payment_constraints: PaymentConstraints {
 			max_cltv_expiry: u32::max_value(),
@@ -148,6 +151,7 @@ fn mpp_to_one_hop_blinded_path() {
 	let amt_msat = 15_000_000;
 	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[3], Some(amt_msat), None);
 	let payee_tlvs = ReceiveTlvs {
+		padding: None,
 		payment_secret,
 		payment_constraints: PaymentConstraints {
 			max_cltv_expiry: u32::max_value(),
@@ -1293,6 +1297,7 @@ fn custom_tlvs_to_blinded_path() {
 	let amt_msat = 5000;
 	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[1], Some(amt_msat), None);
 	let payee_tlvs = ReceiveTlvs {
+		padding: None,
 		payment_secret,
 		payment_constraints: PaymentConstraints {
 			max_cltv_expiry: u32::max_value(),

lightning/src/ln/channelmanager.rs

@@ -9345,6 +9345,7 @@ where
 		let max_cltv_expiry = self.best_block.read().unwrap().height + CLTV_FAR_FAR_AWAY
 			+ LATENCY_GRACE_PERIOD_BLOCKS;
 		let payee_tlvs = ReceiveTlvs {
+			padding: None,
 			payment_secret,
 			payment_constraints: PaymentConstraints {
 				max_cltv_expiry,

lightning/src/ln/max_payment_path_len_tests.rs

@@ -159,6 +159,7 @@ fn one_hop_blinded_path_with_custom_tlv() {
 	let amt_msat = 100_000;
 	let (payment_preimage, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[2], Some(amt_msat), None);
 	let payee_tlvs = ReceiveTlvs {
+		padding: None,
 		payment_secret,
 		payment_constraints: PaymentConstraints {
 			max_cltv_expiry: u32::max_value(),

lightning/src/ln/msgs.rs

@@ -2758,7 +2758,8 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, &NS)> for InboundOnionPayload w
 			let mut reader = FixedLengthReader::new(&mut s, enc_tlvs.len() as u64);
 			match ChaChaPolyReadAdapter::read(&mut reader, rho)? {
 				ChaChaPolyReadAdapter { readable: BlindedPaymentTlvs::Forward(ForwardTlvs {
-					short_channel_id, payment_relay, payment_constraints, features
+					padding: _, short_channel_id, payment_relay,
+					payment_constraints, features
 				})} => {
 					if amt.is_some() || cltv_value.is_some() || total_msat.is_some() ||
 						keysend_preimage.is_some()
@@ -2774,7 +2775,8 @@ impl<NS: Deref> ReadableArgs<(Option<PublicKey>, &NS)> for InboundOnionPayload w
 					})
 				},
 				ChaChaPolyReadAdapter { readable: BlindedPaymentTlvs::Receive(ReceiveTlvs {
-					payment_secret, payment_constraints, payment_context
+					padding: _, payment_secret, payment_constraints,
+					payment_context
 				})} => {
 					if total_msat.unwrap_or(0) > MAX_VALUE_MSAT { return Err(DecodeError::InvalidValue) }
 					Ok(Self::BlindedReceive {

lightning/src/routing/router.rs

@@ -146,6 +146,7 @@ impl<G: Deref<Target = NetworkGraph<L>> + Clone, L: Deref, ES: Deref, S: Deref,
 				};
 				Some(payment::ForwardNode {
 					tlvs: ForwardTlvs {
+						padding: None,
 						short_channel_id,
 						payment_relay,
 						payment_constraints,