WIP: Include blinded paths

lightning/src/blinded_path/mod.rs

@@ -64,9 +64,9 @@ impl BlindedPath {
 	///
 	/// Errors if less than two hops are provided or if `node_pk`(s) are invalid.
 	//  TODO: make all payloads the same size with padding + add dummy hops
-	pub fn new_for_message<ES: EntropySource, T: secp256k1::Signing + secp256k1::Verification>
-		(node_pks: &[PublicKey], entropy_source: &ES, secp_ctx: &Secp256k1<T>) -> Result<Self, ()>
-	{
+	pub fn new_for_message<ES: Deref, T: secp256k1::Signing + secp256k1::Verification>(
+		node_pks: &[PublicKey], entropy_source: ES, secp_ctx: &Secp256k1<T>
+	) -> Result<Self, ()> where ES::Target: EntropySource {
 		if node_pks.len() < 2 { return Err(()) }
 		let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 		let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");

lightning/src/ln/channelmanager.rs

@@ -30,6 +30,7 @@ use bitcoin::secp256k1::{SecretKey,PublicKey};
 use bitcoin::secp256k1::Secp256k1;
 use bitcoin::{LockTime, secp256k1, Sequence};
 
+use crate::blinded_path::BlindedPath;
 use crate::chain;
 use crate::chain::{Confirm, ChannelMonitorUpdateStatus, Watch, BestBlock};
 use crate::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator};
@@ -6353,6 +6354,10 @@ where
 	/// Creates an [`OfferBuilder`] such that the [`Offer`] it builds is recognized by the
 	/// [`ChannelManager`] when handling [`InvoiceRequest`] messages for the offer.
 	///
+	/// Uses [`Router::find_partial_paths`] to construct a [`BlindedPath`] for the offer. If one is
+	/// found, also uses a derived signing pubkey for recipient privacy. Otherwise, uses the node id
+	/// as the signing pubkey.
+	///
 	/// [`Offer`]: crate::offers::offer::Offer
 	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 	pub fn create_offer_builder(
@@ -6362,16 +6367,26 @@ where
 		let expanded_key = &self.inbound_payment_key;
 		let entropy = &*self.entropy_source;
 		let secp_ctx = &self.secp_ctx;
+		let builder = OfferBuilder::deriving_signing_pubkey(
+			description, node_id, expanded_key, entropy, secp_ctx
+		);
 
-		// TODO: Set blinded paths
-		OfferBuilder::deriving_signing_pubkey(description, node_id, expanded_key, entropy, secp_ctx)
+		match self.create_blinded_paths(1) {
+			Ok(paths) if !paths.is_empty() => builder.path(paths.into_iter().next().unwrap()),
+			// TODO: check if node is public?
+			Ok(_) | Err(_) => builder,
+		}
 	}
 
 	/// Creates a [`RefundBuilder`] such that the [`Refund`] it builds is recognized by the
 	/// [`ChannelManager`] when handling [`Bolt12Invoice`] messages for the refund.
 	///
 	/// The provided `payment_id` is used to ensure that only one invoice is paid for the refund.
 	///
+	/// Uses [`Router::find_partial_paths`] to construct a [`BlindedPath`] for the refund. If one is
+	/// found, also uses a derived payer id for sender privacy. Otherwise, uses the node id as the
+	/// payer id.
+	///
 	/// [`Refund`]: crate::offers::refund::Refund
 	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 	pub fn create_refund_builder(
@@ -6382,10 +6397,14 @@ where
 		let entropy = &*self.entropy_source;
 		let secp_ctx = &self.secp_ctx;
 
-		// TODO: Set blinded paths
 		let builder = RefundBuilder::deriving_payer_id(
 			description, node_id, expanded_key, entropy, secp_ctx, amount_msats, payment_id
 		)?;
+		let builder = match self.create_blinded_paths(1) {
+			Ok(paths) if !paths.is_empty() => builder.path(paths.into_iter().next().unwrap()),
+			// TODO: check if node is public?
+			Ok(_) | Err(_) => builder,
+		};
 		self.pending_outbound_payments
 			.add_new_awaiting_invoice(payment_id)
 			.map_err(|_| Bolt12SemanticError::DuplicatePaymentId)?;
@@ -6518,6 +6537,23 @@ where
 		inbound_payment::get_payment_preimage(payment_hash, payment_secret, &self.inbound_payment_key)
 	}
 
+	///
+	fn create_blinded_paths(&self, count: usize) -> Result<Vec<BlindedPath>, ()> {
+		let last_hops = self.per_peer_state.read().unwrap().iter()
+			.filter(|(_, peer)| peer.lock().unwrap().latest_features.supports_route_blinding())
+			.map(|(node_id, _)| *node_id)
+			.collect::<Vec<_>>();
+		let entropy_source = self.entropy_source.deref();
+		let secp_ctx = &self.secp_ctx;
+
+		self.router
+			.find_partial_paths(self.get_our_node_id(), last_hops.as_slice())?
+			.into_iter()
+			.map(|node_pks| BlindedPath::new_for_message(&node_pks[..], entropy_source, secp_ctx))
+			.take(count)
+			.collect()
+	}
+
 	/// Gets a fake short channel id for use in receiving [phantom node payments]. These fake scids
 	/// are used when constructing the phantom invoice's route hints.
 	///

lightning/src/routing/router.rs

@@ -90,6 +90,7 @@ pub trait Router {
 		&self, payer: &PublicKey, route_params: &RouteParameters,
 		first_hops: Option<&[&ChannelDetails]>, inflight_htlcs: InFlightHtlcs
 	) -> Result<Route, LightningError>;
+
 	/// Finds a [`Route`] for a payment between the given `payer` and a payee.
 	///
 	/// The `payee` and the payment's value are given in [`RouteParameters::payment_params`]
@@ -104,6 +105,17 @@ pub trait Router {
 	) -> Result<Route, LightningError> {
 		self.find_route(payer, route_params, first_hops, inflight_htlcs)
 	}
+
+	/// Finds partial paths to the `recipient` node for creating `BlindedPath`s. The nodes in
+	/// `peers` are assumed to be direct peers with the `recipient`.
+	///
+	/// The default implementation returns two-node paths for each node in `peers` with the
+	/// `recipient` node.
+	fn find_partial_paths(
+		&self, recipient: PublicKey, peers: &[PublicKey]
+	) -> Result<Vec<Vec<PublicKey>>, ()> {
+		Ok(peers.iter().map(|hop| vec![*hop, recipient]).collect())
+	}
 }
 
 /// [`Score`] implementation that factors in in-flight HTLC liquidity.