Allow create_blinded_paths functions to accept MessageContext as input field

- Enabled `create_blinded_paths` to accept `MessageContext` TLVs as
  an input field.
- `MessageContext` is intended to be sent along with the `reply_path`
   to the counterparty.
- Added `MessageContext` in the `create_blinded_paths` flow, optionally
  appending it within the `reply_path`.
- Updated tests to verify the new feature.

Author: shaavan

fuzz/src/chanmon_consistency.rs

@@ -33,6 +33,7 @@ use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hashes::Hash as TraitImport;
 use bitcoin::WPubkeyHash;
 
+use lightning::blinded_path::message::MessageContext;
 use lightning::blinded_path::payment::ReceiveTlvs;
 use lightning::blinded_path::BlindedPath;
 use lightning::chain;
@@ -138,7 +139,8 @@ impl MessageRouter for FuzzRouter {
 	}
 
 	fn create_blinded_paths<T: secp256k1::Signing + secp256k1::Verification>(
-		&self, _recipient: PublicKey, _peers: Vec<PublicKey>, _secp_ctx: &Secp256k1<T>,
+		&self, _recipient: PublicKey, _context: MessageContext, _peers: Vec<PublicKey>,
+		_secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPath>, ()> {
 		unreachable!()
 	}

fuzz/src/full_stack.rs

@@ -30,6 +30,7 @@ use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hashes::Hash as _;
 use bitcoin::WPubkeyHash;
 
+use lightning::blinded_path::message::MessageContext;
 use lightning::blinded_path::payment::ReceiveTlvs;
 use lightning::blinded_path::BlindedPath;
 use lightning::chain;
@@ -175,7 +176,8 @@ impl MessageRouter for FuzzRouter {
 	}
 
 	fn create_blinded_paths<T: secp256k1::Signing + secp256k1::Verification>(
-		&self, _recipient: PublicKey, _peers: Vec<PublicKey>, _secp_ctx: &Secp256k1<T>,
+		&self, _recipient: PublicKey, _context: MessageContext, _peers: Vec<PublicKey>,
+		_secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPath>, ()> {
 		unreachable!()
 	}

fuzz/src/invoice_request_deser.rs

@@ -87,10 +87,22 @@ fn build_response<T: secp256k1::Signing + secp256k1::Verification>(
 		],
 	];
 	let paths = vec![
-		BlindedPath::new_for_message(&intermediate_nodes[0], pubkey(42), &entropy_source, secp_ctx)
-			.unwrap(),
-		BlindedPath::new_for_message(&intermediate_nodes[1], pubkey(42), &entropy_source, secp_ctx)
-			.unwrap(),
+		BlindedPath::new_for_message(
+			&intermediate_nodes[0],
+			pubkey(42),
+			None,
+			&entropy_source,
+			secp_ctx,
+		)
+		.unwrap(),
+		BlindedPath::new_for_message(
+			&intermediate_nodes[1],
+			pubkey(42),
+			None,
+			&entropy_source,
+			secp_ctx,
+		)
+		.unwrap(),
 	];
 
 	let payinfo = vec![

fuzz/src/onion_message.rs

@@ -95,7 +95,8 @@ impl MessageRouter for TestMessageRouter {
 	}
 
 	fn create_blinded_paths<T: secp256k1::Signing + secp256k1::Verification>(
-		&self, _recipient: PublicKey, _peers: Vec<PublicKey>, _secp_ctx: &Secp256k1<T>,
+		&self, _recipient: PublicKey, _context: MessageContext, _peers: Vec<PublicKey>,
+		_secp_ctx: &Secp256k1<T>,
 	) -> Result<Vec<BlindedPath>, ()> {
 		unreachable!()
 	}

fuzz/src/refund_deser.rs

@@ -76,10 +76,22 @@ fn build_response<T: secp256k1::Signing + secp256k1::Verification>(
 		],
 	];
 	let paths = vec![
-		BlindedPath::new_for_message(&intermediate_nodes[0], pubkey(42), &entropy_source, secp_ctx)
-			.unwrap(),
-		BlindedPath::new_for_message(&intermediate_nodes[1], pubkey(42), &entropy_source, secp_ctx)
-			.unwrap(),
+		BlindedPath::new_for_message(
+			&intermediate_nodes[0],
+			pubkey(42),
+			None,
+			&entropy_source,
+			secp_ctx,
+		)
+		.unwrap(),
+		BlindedPath::new_for_message(
+			&intermediate_nodes[1],
+			pubkey(42),
+			None,
+			&entropy_source,
+			secp_ctx,
+		)
+		.unwrap(),
 	];
 
 	let payinfo = vec![

lightning/src/blinded_path/message.rs

@@ -12,6 +12,7 @@
 //! [`BlindedPath`]: crate::blinded_path::BlindedPath
 
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
+
 #[allow(unused_imports)]
 use crate::prelude::*;
 
@@ -138,7 +139,7 @@ impl_writeable_tlv_based_enum!(OffersContext,
 /// Construct blinded onion message hops for the given `intermediate_nodes` and `recipient_node_id`.
 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 	secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode], recipient_node_id: PublicKey,
-	session_priv: &SecretKey
+	context: MessageContext, session_priv: &SecretKey
 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
 	let pks = intermediate_nodes.iter().map(|node| &node.node_id)
 		.chain(core::iter::once(&recipient_node_id));
@@ -150,7 +151,7 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
 			None => NextMessageHop::NodeId(*pubkey),
 		})
 		.map(|next_hop| ControlTlvs::Forward(ForwardTlvs { next_hop, next_blinding_override: None }))
-		.chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs { context: None })));
+		.chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs{ context: Some(context) })));
 
 	utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 }

lightning/src/blinded_path/mod.rs

@@ -14,6 +14,7 @@ pub mod message;
 pub(crate) mod utils;
 
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
+use message::MessageContext;
 use core::ops::Deref;
 
 use crate::ln::msgs::DecodeError;
@@ -123,9 +124,9 @@ pub struct BlindedHop {
 impl BlindedPath {
 	/// Create a one-hop blinded path for a message.
 	pub fn one_hop_for_message<ES: Deref, T: secp256k1::Signing + secp256k1::Verification>(
-		recipient_node_id: PublicKey, entropy_source: ES, secp_ctx: &Secp256k1<T>
+		recipient_node_id: PublicKey, context: MessageContext, entropy_source: ES, secp_ctx: &Secp256k1<T>
 	) -> Result<Self, ()> where ES::Target: EntropySource {
-		Self::new_for_message(&[], recipient_node_id, entropy_source, secp_ctx)
+		Self::new_for_message(&[], recipient_node_id, context, entropy_source, secp_ctx)
 	}
 
 	/// Create a blinded path for an onion message, to be forwarded along `node_pks`. The last node
@@ -135,7 +136,7 @@ impl BlindedPath {
 	//  TODO: make all payloads the same size with padding + add dummy hops
 	pub fn new_for_message<ES: Deref, T: secp256k1::Signing + secp256k1::Verification>(
 		intermediate_nodes: &[message::ForwardNode], recipient_node_id: PublicKey,
-		entropy_source: ES, secp_ctx: &Secp256k1<T>
+		context: MessageContext, entropy_source: ES, secp_ctx: &Secp256k1<T>
 	) -> Result<Self, ()> where ES::Target: EntropySource {
 		let introduction_node = IntroductionNode::NodeId(
 			intermediate_nodes.first().map_or(recipient_node_id, |n| n.node_id)
@@ -147,7 +148,8 @@ impl BlindedPath {
 			introduction_node,
 			blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
 			blinded_hops: message::blinded_hops(
-				secp_ctx, intermediate_nodes, recipient_node_id, &blinding_secret,
+				secp_ctx, intermediate_nodes, recipient_node_id,
+				context, &blinding_secret,
 			).map_err(|_| ())?,
 		})
 	}

lightning/src/ln/channelmanager.rs

@@ -31,7 +31,7 @@ use bitcoin::secp256k1::{SecretKey,PublicKey};
 use bitcoin::secp256k1::Secp256k1;
 use bitcoin::{secp256k1, Sequence};
 
-use crate::blinded_path::message::OffersContext;
+use crate::blinded_path::message::{MessageContext, OffersContext};
 use crate::blinded_path::{BlindedPath, NodeIdLookUp};
 use crate::blinded_path::message::ForwardNode;
 use crate::blinded_path::payment::{Bolt12OfferContext, Bolt12RefundContext, PaymentConstraints, PaymentContext, ReceiveTlvs};
@@ -8375,7 +8375,7 @@ macro_rules! create_offer_builder { ($self: ident, $builder: ty) => {
 		let entropy = &*$self.entropy_source;
 		let secp_ctx = &$self.secp_ctx;
 
-		let path = $self.create_blinded_path_using_absolute_expiry(absolute_expiry)
+		let path = $self.create_blinded_path_using_absolute_expiry(OffersContext::Unknown {}, absolute_expiry)
 			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 		let builder = OfferBuilder::deriving_signing_pubkey(
 			node_id, expanded_key, entropy, secp_ctx
@@ -8447,7 +8447,8 @@ macro_rules! create_refund_builder { ($self: ident, $builder: ty) => {
 		let entropy = &*$self.entropy_source;
 		let secp_ctx = &$self.secp_ctx;
 
-		let path = $self.create_blinded_path_using_absolute_expiry(Some(absolute_expiry))
+		let context = OffersContext::OutboundPayment { payment_id };
+		let path = $self.create_blinded_path_using_absolute_expiry(context, Some(absolute_expiry))
 			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 		let builder = RefundBuilder::deriving_payer_id(
 			node_id, expanded_key, entropy, secp_ctx, amount_msats, payment_id
@@ -8570,7 +8571,9 @@ where
 			Some(payer_note) => builder.payer_note(payer_note),
 		};
 		let invoice_request = builder.build_and_sign()?;
-		let reply_path = self.create_blinded_path().map_err(|_| Bolt12SemanticError::MissingPaths)?;
+
+		let context = OffersContext::OutboundPayment { payment_id };
+		let reply_path = self.create_blinded_path(context).map_err(|_| Bolt12SemanticError::MissingPaths)?;
 
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 
@@ -8670,7 +8673,7 @@ where
 				)?;
 				let builder: InvoiceBuilder<DerivedSigningPubkey> = builder.into();
 				let invoice = builder.allow_mpp().build_and_sign(secp_ctx)?;
-				let reply_path = self.create_blinded_path()
+				let reply_path = self.create_blinded_path(OffersContext::Unknown {})
 					.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 
 				let mut pending_offers_messages = self.pending_offers_messages.lock().unwrap();
@@ -8803,15 +8806,15 @@ where
 	/// respectively, based on the given `absolute_expiry` as seconds since the Unix epoch. See
 	/// [`MAX_SHORT_LIVED_RELATIVE_EXPIRY`].
 	fn create_blinded_path_using_absolute_expiry(
-		&self, absolute_expiry: Option<Duration>
+		&self, context: OffersContext, absolute_expiry: Option<Duration>,
 	) -> Result<BlindedPath, ()> {
 		let now = self.duration_since_epoch();
 		let max_short_lived_absolute_expiry = now.saturating_add(MAX_SHORT_LIVED_RELATIVE_EXPIRY);
 
 		if absolute_expiry.unwrap_or(Duration::MAX) <= max_short_lived_absolute_expiry {
-			self.create_compact_blinded_path()
+			self.create_compact_blinded_path(context)
 		} else {
-			self.create_blinded_path()
+			self.create_blinded_path(context)
 		}
 	}
 
@@ -8831,7 +8834,7 @@ where
 	/// Creates a blinded path by delegating to [`MessageRouter::create_blinded_paths`].
 	///
 	/// Errors if the `MessageRouter` errors or returns an empty `Vec`.
-	fn create_blinded_path(&self) -> Result<BlindedPath, ()> {
+	fn create_blinded_path(&self, context: OffersContext) -> Result<BlindedPath, ()> {
 		let recipient = self.get_our_node_id();
 		let secp_ctx = &self.secp_ctx;
 
@@ -8844,14 +8847,14 @@ where
 			.collect::<Vec<_>>();
 
 		self.router
-			.create_blinded_paths(recipient, peers, secp_ctx)
+			.create_blinded_paths(recipient, MessageContext::Offers(context), peers, secp_ctx)
 			.and_then(|paths| paths.into_iter().next().ok_or(()))
 	}
 
 	/// Creates a blinded path by delegating to [`MessageRouter::create_compact_blinded_paths`].
 	///
 	/// Errors if the `MessageRouter` errors or returns an empty `Vec`.
-	fn create_compact_blinded_path(&self) -> Result<BlindedPath, ()> {
+	fn create_compact_blinded_path(&self, context: OffersContext) -> Result<BlindedPath, ()> {
 		let recipient = self.get_our_node_id();
 		let secp_ctx = &self.secp_ctx;
 
@@ -8871,7 +8874,7 @@ where
 			.collect::<Vec<_>>();
 
 		self.router
-			.create_compact_blinded_paths(recipient, peers, secp_ctx)
+			.create_compact_blinded_paths(recipient, MessageContext::Offers(context), peers, secp_ctx)
 			.and_then(|paths| paths.into_iter().next().ok_or(()))
 	}
 

lightning/src/ln/offers_tests.rs

@@ -1412,6 +1412,14 @@ fn fails_sending_invoice_without_blinded_payment_paths_for_offer() {
 
 	let invoice_error = extract_invoice_error(david, &onion_message);
 	assert_eq!(invoice_error, InvoiceError::from(Bolt12SemanticError::MissingPaths));
+
+	// Confirm that david drops this failed payment from his pending outbound payments.
+	match get_event!(david, Event::InvoiceRequestFailed) {
+		Event::InvoiceRequestFailed { payment_id: pay_id } => {
+			assert_eq!(pay_id, payment_id)
+		},
+		_ => panic!("No Event::InvoiceRequestFailed"),
+	}
 }
 
 #[test]