Move some blinded path message code into message submodule.

We'll similarly separate blinded path payments code into its own module.

Author: valentinewallace

lightning/src/blinded_path/message.rs

@@ -0,0 +1,79 @@
+use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
+use crate::blinded_path::BlindedHop;
+use crate::blinded_path::utils;
+use crate::io;
+use crate::prelude::*;
+use crate::util::ser::{Writeable, Writer};
+
+/// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
+/// route, they are encoded into [`BlindedHop::encrypted_payload`].
+pub(crate) struct ForwardTlvs {
+	/// The node id of the next hop in the onion message's path.
+	pub(crate) next_node_id: PublicKey,
+	/// Senders to a blinded path use this value to concatenate the route they find to the
+	/// introduction node with the blinded path.
+	pub(crate) next_blinding_override: Option<PublicKey>,
+}
+
+/// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
+pub(crate) struct ReceiveTlvs {
+	/// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
+	/// sending to. This is useful for receivers to check that said blinded path is being used in
+	/// the right context.
+	pub(crate) path_id: Option<[u8; 32]>,
+}
+
+impl Writeable for ForwardTlvs {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+		// TODO: write padding
+		encode_tlv_stream!(writer, {
+			(4, self.next_node_id, required),
+			(8, self.next_blinding_override, option)
+		});
+		Ok(())
+	}
+}
+
+impl Writeable for ReceiveTlvs {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+		// TODO: write padding
+		encode_tlv_stream!(writer, {
+			(6, self.path_id, option),
+		});
+		Ok(())
+	}
+}
+
+/// Construct blinded onion message hops for the given `unblinded_path`.
+pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
+	secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
+) -> Result<Vec<BlindedHop>, secp256k1::Error> {
+	let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
+
+	let mut prev_ss_and_blinded_node_id = None;
+	utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
+		if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
+			if let Some(pk) = unblinded_pk {
+				let payload = ForwardTlvs {
+					next_node_id: pk,
+					next_blinding_override: None,
+				};
+				blinded_hops.push(BlindedHop {
+					blinded_node_id: prev_blinded_node_id,
+					encrypted_payload: utils::encrypt_payload(payload, prev_ss),
+				});
+			} else { debug_assert!(false); }
+		}
+		prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
+	})?;
+
+	if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
+		let final_payload = ReceiveTlvs { path_id: None };
+		blinded_hops.push(BlindedHop {
+			blinded_node_id: final_blinded_node_id,
+			encrypted_payload: utils::encrypt_payload(final_payload, final_ss),
+		});
+	} else { debug_assert!(false) }
+
+	Ok(blinded_hops)
+}

lightning/src/blinded_path/mod.rs

@@ -9,6 +9,7 @@
 
 //! Creating blinded paths and related utilities live here.
 
+pub(crate) mod message;
 pub(crate) mod utils;
 
 use bitcoin::hashes::{Hash, HashEngine};
@@ -75,7 +76,7 @@ impl BlindedPath {
 		Ok(BlindedPath {
 			introduction_node_id,
 			blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
-			blinded_hops: blinded_message_hops(secp_ctx, node_pks, &blinding_secret).map_err(|_| ())?,
+			blinded_hops: message::blinded_hops(secp_ctx, node_pks, &blinding_secret).map_err(|_| ())?,
 		})
 	}
 
@@ -91,7 +92,7 @@ impl BlindedPath {
 		let mut s = Cursor::new(&encrypted_control_tlvs);
 		let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
 		match ChaChaPolyReadAdapter::read(&mut reader, rho) {
-			Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(ForwardTlvs {
+			Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(message::ForwardTlvs {
 				mut next_node_id, next_blinding_override,
 			})}) => {
 				let mut new_blinding_point = match next_blinding_override {
@@ -116,40 +117,6 @@ impl BlindedPath {
 	}
 }
 
-/// Construct blinded onion message hops for the given `unblinded_path`.
-fn blinded_message_hops<T: secp256k1::Signing + secp256k1::Verification>(
-	secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
-) -> Result<Vec<BlindedHop>, secp256k1::Error> {
-	let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
-
-	let mut prev_ss_and_blinded_node_id = None;
-	utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
-		if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
-			if let Some(pk) = unblinded_pk {
-				let payload = ForwardTlvs {
-					next_node_id: pk,
-					next_blinding_override: None,
-				};
-				blinded_hops.push(BlindedHop {
-					blinded_node_id: prev_blinded_node_id,
-					encrypted_payload: utils::encrypt_payload(payload, prev_ss),
-				});
-			} else { debug_assert!(false); }
-		}
-		prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
-	})?;
-
-	if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
-		let final_payload = ReceiveTlvs { path_id: None };
-		blinded_hops.push(BlindedHop {
-			blinded_node_id: final_blinded_node_id,
-			encrypted_payload: utils::encrypt_payload(final_payload, final_ss),
-		});
-	} else { debug_assert!(false) }
-
-	Ok(blinded_hops)
-}
-
 impl Writeable for BlindedPath {
 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 		self.introduction_node_id.write(w)?;
@@ -185,41 +152,3 @@ impl_writeable!(BlindedHop, {
 	encrypted_payload
 });
 
-/// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
-/// route, they are encoded into [`BlindedHop::encrypted_payload`].
-pub(crate) struct ForwardTlvs {
-	/// The node id of the next hop in the onion message's path.
-	pub(super) next_node_id: PublicKey,
-	/// Senders to a blinded path use this value to concatenate the route they find to the
-	/// introduction node with the blinded path.
-	pub(super) next_blinding_override: Option<PublicKey>,
-}
-
-/// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
-pub(crate) struct ReceiveTlvs {
-	/// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
-	/// sending to. This is useful for receivers to check that said blinded path is being used in
-	/// the right context.
-	pub(super) path_id: Option<[u8; 32]>,
-}
-
-impl Writeable for ForwardTlvs {
-	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
-		// TODO: write padding
-		encode_tlv_stream!(writer, {
-			(4, self.next_node_id, required),
-			(8, self.next_blinding_override, option)
-		});
-		Ok(())
-	}
-}
-
-impl Writeable for ReceiveTlvs {
-	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
-		// TODO: write padding
-		encode_tlv_stream!(writer, {
-			(6, self.path_id, option),
-		});
-		Ok(())
-	}
-}

lightning/src/onion_message/messenger.rs

@@ -15,7 +15,9 @@ use bitcoin::hashes::hmac::{Hmac, HmacEngine};
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
 
-use crate::blinded_path::{BlindedPath, ForwardTlvs, ReceiveTlvs, utils};
+use crate::blinded_path::BlindedPath;
+use crate::blinded_path::message::{ForwardTlvs, ReceiveTlvs};
+use crate::blinded_path::utils;
 use crate::sign::{EntropySource, KeysManager, NodeSigner, Recipient};
 use crate::events::OnionMessageProvider;
 use crate::ln::features::{InitFeatures, NodeFeatures};

lightning/src/onion_message/packet.rs

@@ -12,7 +12,8 @@
 use bitcoin::secp256k1::PublicKey;
 use bitcoin::secp256k1::ecdh::SharedSecret;
 
-use crate::blinded_path::{BlindedPath, ForwardTlvs, ReceiveTlvs};
+use crate::blinded_path::BlindedPath;
+use crate::blinded_path::message::{ForwardTlvs, ReceiveTlvs};
 use crate::ln::msgs::DecodeError;
 use crate::ln::onion_utils;
 use super::messenger::CustomOnionMessageHandler;
@@ -151,15 +152,16 @@ pub(super) enum ForwardControlTlvs {
 	Blinded(Vec<u8>),
 	/// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 	/// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
-	/// them into an intermediate Vec. See [`crate::blinded_path::ForwardTlvs`] for more info.
+	/// them into an intermediate Vec. See [`crate::blinded_path::message::ForwardTlvs`] for more
+	/// info.
 	Unblinded(ForwardTlvs),
 }
 
 /// Receive control TLVs in their blinded and unblinded form.
 pub(super) enum ReceiveControlTlvs {
 	/// See [`ForwardControlTlvs::Blinded`].
 	Blinded(Vec<u8>),
-	/// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::ReceiveTlvs`].
+	/// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::message::ReceiveTlvs`].
 	Unblinded(ReceiveTlvs),
 }