WIP: Include blinded paths

Author: jkczyz

lightning/src/blinded_path/mod.rs

@@ -15,6 +15,7 @@ pub(crate) mod utils;
 
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
 
+use core::ops::Deref;
 use crate::ln::msgs::DecodeError;
 use crate::offers::invoice::BlindedPayInfo;
 use crate::sign::EntropySource;
@@ -61,10 +62,9 @@ impl BlindedPath {
 	///
 	/// Errors if less than one hop is 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, ()>
-	{
-		if node_pks.is_empty() { return Err(()) }
+	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 {
 		let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 		let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 		let introduction_node_id = node_pks[0];

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};
@@ -6708,6 +6709,9 @@ where
 	/// Creates an [`OfferBuilder`] such that the [`Offer`] it builds is recognized by the
 	/// [`ChannelManager`] when handling [`InvoiceRequest`] messages for the offer.
 	///
+	/// Uses a one-hop [`BlindedPath`] for the offer with [`ChannelManager::get_our_node_id`] as the
+	/// introduction node and a derived signing pubkey for recipient privacy.
+	///
 	/// [`Offer`]: crate::offers::offer::Offer
 	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 	pub fn create_offer_builder(
@@ -6717,16 +6721,25 @@ 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_one_hop_blinded_path() {
+			Ok(path) => builder.path(path),
+			// TODO: check if node is public?
+			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 a one-hop [`BlindedPath`] for the refund with [`ChannelManager::get_our_node_id`] as
+	/// the introduction node and a derived payer id for sender privacy.
+	///
 	/// [`Refund`]: crate::offers::refund::Refund
 	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 	pub fn create_refund_builder(
@@ -6737,10 +6750,14 @@ 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_one_hop_blinded_path() {
+			Ok(path) => builder.path(path),
+			// TODO: check if node is public?
+			Err(_) => builder,
+		};
 		self.pending_outbound_payments
 			.add_new_awaiting_invoice(payment_id, retry_strategy)
 			.map_err(|_| Bolt12SemanticError::DuplicatePaymentId)?;
@@ -6873,6 +6890,15 @@ where
 		inbound_payment::get_payment_preimage(payment_hash, payment_secret, &self.inbound_payment_key)
 	}
 
+	/// Creates a one-hop blinded path with [`ChannelManager::get_our_node_id`] as the introduction
+	/// node.
+	fn create_one_hop_blinded_path(&self) -> Result<BlindedPath, ()> {
+		let entropy_source = self.entropy_source.deref();
+		let secp_ctx = &self.secp_ctx;
+		BlindedPath::new_for_message(&[self.get_our_node_id()], entropy_source, secp_ctx)
+
+	}
+
 	/// 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`]