Introduce Padding for Blinded Payment Paths

Author: shaavan

lightning/src/blinded_path/payment.rs

@@ -12,7 +12,7 @@
 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, WithPadding};
 use crate::crypto::streams::ChaChaPolyReadAdapter;
 use crate::io;
 use crate::io::Cursor;
@@ -412,7 +412,6 @@ impl Writeable for ReceiveTlvs {
 
 impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
-		// TODO: write padding
 		match self {
 			Self::Forward(tlvs) => tlvs.write(w)?,
 			Self::Receive(tlvs) => tlvs.write(w)?,
@@ -467,7 +466,7 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 	let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
 		.chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
 
-	let path = pks.zip(tlvs);
+	let path = pks.zip(tlvs.map(|tlv| WithPadding { tlvs: tlv }));
 
 	utils::construct_blinded_hops(secp_ctx, path, session_priv)
 }

lightning/src/ln/blinded_payment_tests.rs

@@ -298,7 +298,7 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
 	let mut route_params = get_blinded_route_parameters(amt_msat, payment_secret, 1, 1_0000_0000,
 		nodes.iter().skip(1).map(|n| n.node.get_our_node_id()).collect(),
 		&[&chan_upd_1_2, &chan_upd_2_3], &chanmon_cfgs[3].keys_manager);
-	route_params.payment_params.max_path_length = 18;
+	route_params.payment_params.max_path_length = 16;
 
 	let route = get_route(&nodes[0], &route_params).unwrap();
 	node_cfgs[0].router.expect_find_route(route_params.clone(), Ok(route.clone()));
@@ -822,6 +822,8 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
 		nodes.iter().skip(1).map(|n| n.node.get_our_node_id()).collect(), &[&chan_upd_1_2],
 		&chanmon_cfgs[2].keys_manager);
 
+	route_params.payment_params.max_path_length = 17;
+
 	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.