public onion utils, create/peel payment

Author: Evanfeenstra

lightning/src/ln/mod.rs

@@ -39,6 +39,7 @@ pub(crate) mod onion_utils;
 mod outbound_payment;
 pub mod wire;
 
+pub use onion_utils::{ForwardedPayment, PeeledPayment, ReceivedPayment, create_payment_onion, peel_payment_onion};
 // Older rustc (which we support) refuses to let us call the get_payment_preimage_hash!() macro
 // without the node parameter being mut. This is incorrect, and thus newer rustcs will complain
 // about an unnecessary mut. Thus, we silence the unused_mut warning in two test modules below.

lightning/src/ln/msgs.rs

@@ -1674,17 +1674,21 @@ pub use self::fuzzy_internal_msgs::*;
 #[cfg(not(fuzzing))]
 pub(crate) use self::fuzzy_internal_msgs::*;
 
+/// Bolt04 OnionPacket including hop data for the next peer
 #[derive(Clone)]
-pub(crate) struct OnionPacket {
-	pub(crate) version: u8,
+pub struct OnionPacket {
+	/// Bolt 04 version number
+	pub version: u8,
 	/// In order to ensure we always return an error on onion decode in compliance with [BOLT
 	/// #4](https://github.com/lightning/bolts/blob/master/04-onion-routing.md), we have to
 	/// deserialize `OnionPacket`s contained in [`UpdateAddHTLC`] messages even if the ephemeral
 	/// public key (here) is bogus, so we hold a [`Result`] instead of a [`PublicKey`] as we'd
 	/// like.
-	pub(crate) public_key: Result<PublicKey, secp256k1::Error>,
-	pub(crate) hop_data: [u8; 20*65],
-	pub(crate) hmac: [u8; 32],
+	pub public_key: Result<PublicKey, secp256k1::Error>,
+	/// 1300 bytes encrypted payload for the next hop
+	pub hop_data: [u8; 20*65],
+	/// HMAC to verify the integrity of hop_data
+	pub hmac: [u8; 32],
 }
 
 impl onion_utils::Packet for OnionPacket {

lightning/src/ln/onion_utils.rs

@@ -13,7 +13,7 @@ use crate::ln::msgs;
 use crate::ln::wire::Encode;
 use crate::routing::gossip::NetworkUpdate;
 use crate::routing::router::{BlindedTail, Path, RouteHop};
-use crate::sign::NodeSigner;
+use crate::sign::{NodeSigner, Recipient};
 use crate::util::chacha20::{ChaCha20, ChaChaReader};
 use crate::util::errors::{self, APIError};
 use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer, LengthCalculatingWriter};
@@ -935,6 +935,180 @@ pub(crate) fn decode_next_payment_hop<NS: Deref>(
 	}
 }
 
+/// Build a payment onion, returning the first hop msat and cltv values as well.
+pub fn create_payment_onion<T>(
+	secp_ctx: &Secp256k1<T>, path: &Path, session_priv: &SecretKey, total_msat: u64, 
+	recipient_onion: RecipientOnionFields, best_block_height: u32, payment_hash: PaymentHash,
+	keysend_preimage: Option<PaymentPreimage>, prng_seed: [u8; 32]
+) -> Result<(u64, u32, msgs::OnionPacket), ()>
+where
+	T: secp256k1::Signing
+{
+	let onion_keys = construct_onion_keys(&secp_ctx, &path, &session_priv).map_err(|_| ())?;
+	let (onion_payloads, htlc_msat, htlc_cltv) = build_onion_payloads(
+		&path,
+		total_msat,
+		recipient_onion,
+		best_block_height + 1,
+		&keysend_preimage,
+	).map_err(|_| ())?;
+	let onion_packet = construct_onion_packet(
+		onion_payloads, onion_keys, prng_seed, &payment_hash
+	)?;
+	Ok((htlc_msat, htlc_cltv, onion_packet))
+}
+
+/// Forwarded Payment, including next hop details.
+pub struct ForwardedPayment {
+	/// Short channel id of the next hop.
+	pub short_channel_id: u64,
+	/// The value, in msat, of the payment after this hop's fee is deducted.
+	pub amt_to_forward: u64,
+	/// Outgoing CLTV for the next hop.
+	pub outgoing_cltv_value: u32,
+	/// Onion packet for the next hop.
+	pub onion_packet: msgs::OnionPacket,
+}
+
+/// Received payment, of either regular or blinded type.
+pub enum ReceivedPayment {
+	/// Regular (unblinded) payment.
+	Unblinded {
+		/// Payment_secret to authenticate sender to the receiver.
+		payment_secret: Option<[u8; 32]>,
+		/// The total value, in msat, of the payment as received by the ultimate recipient.
+		total_msat: Option<u64>,
+		/// Custom payment metadata included in the payment.
+		payment_metadata: Option<Vec<u8>>,
+		/// Preimage used in spontaneous payment.
+		keysend_preimage: Option<[u8; 32]>,
+		/// Custom TLV records included in the payment.
+		custom_tlvs: Vec<(u64, Vec<u8>)>,
+		/// Amount received.
+		amt_msat: u64,
+		/// CLTV expiration.
+		cltv_expiry: u32,
+	},
+	/// Blinded payment
+	Blinded {
+		/// Amount received.
+		amt_msat: u64,
+		/// Amount received plus fees paid.
+		total_msat: u64,
+		/// CLTV expiration.
+		cltv_expiry: u32,
+		/// Payment secret.
+		payment_secret: [u8; 32],
+		/// The maximum total CLTV that is acceptable when relaying a payment over this hop.
+		max_cltv_expiry: u32,
+		/// The minimum value, in msat, that may be accepted by the node corresponding to this hop.
+		htlc_minimum_msat: u64,
+		/// Blinding point from intro node.
+		intro_node_blinding_point: PublicKey,
+	}
+}
+
+impl core::convert::TryFrom<msgs::InboundOnionPayload> for ReceivedPayment {
+    type Error = ();
+    fn try_from(pld: msgs::InboundOnionPayload) -> Result<Self, Self::Error> {
+		match pld {
+			msgs::InboundOnionPayload::Forward {
+				short_channel_id: _, amt_to_forward: _, outgoing_cltv_value: _
+			} => {
+				Err(())
+			},
+			msgs::InboundOnionPayload::Receive {
+				payment_data, payment_metadata, keysend_preimage, custom_tlvs, amt_msat,
+				outgoing_cltv_value
+			} => {
+				let (payment_secret, total_msat) = match payment_data {
+					Some(p) => (Some(p.payment_secret.0), Some(p.total_msat)),
+					None => (None, None),
+				};
+				let keysend_preimage = keysend_preimage.map(|p| p.0);
+				Ok(Self::Unblinded {
+					payment_secret, total_msat, payment_metadata, keysend_preimage, custom_tlvs,
+					amt_msat, cltv_expiry: outgoing_cltv_value
+				})
+			},
+			msgs::InboundOnionPayload::BlindedReceive {
+				amt_msat, total_msat, outgoing_cltv_value, payment_secret, payment_constraints,
+				intro_node_blinding_point
+			} => {
+				let payment_secret = payment_secret.0;
+				let max_cltv_expiry = payment_constraints.max_cltv_expiry;
+				let htlc_minimum_msat = payment_constraints.htlc_minimum_msat;
+				Ok(Self::Blinded {
+					amt_msat, total_msat, cltv_expiry: outgoing_cltv_value, payment_secret,
+					max_cltv_expiry, htlc_minimum_msat, intro_node_blinding_point
+				})
+			}
+		}
+    }
+}
+
+/// Received and decrypted onion payment, either of type Receive (for us), or Forward.
+pub enum PeeledPayment {
+	/// This onion payload was for us, not for forwarding to a next-hop.
+	Receive(ReceivedPayment),
+	/// This onion payload to be forwarded to next peer.
+	Forward(ForwardedPayment),
+}
+
+/// Unwrap one layer of an incoming HTLC, returning either or a received payment, or a another
+/// onion to forward.
+pub fn peel_payment_onion<NS: Deref>(
+	onion: &msgs::OnionPacket, payment_hash: PaymentHash, node_signer: &NS,
+	secp_ctx: &Secp256k1<secp256k1::All>
+) -> Result<PeeledPayment, ()> 
+where 
+	NS::Target: NodeSigner,
+{
+	if onion.public_key.is_err() {
+		return Err(());
+	}
+	let shared_secret = node_signer
+		.ecdh(Recipient::Node, &onion.public_key.unwrap(), None)
+		.unwrap()
+		.secret_bytes();
+
+	let hop = decode_next_payment_hop(
+		shared_secret, &onion.hop_data[..], onion.hmac, payment_hash, node_signer
+	).map_err(|_| ())?;
+	let peeled = match hop {
+		Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
+			if let msgs::InboundOnionPayload::Forward{
+				short_channel_id, amt_to_forward, outgoing_cltv_value
+			} = next_hop_data {
+
+				let next_packet_pk = next_hop_pubkey(
+					secp_ctx, onion.public_key.unwrap(), &shared_secret
+				);
+
+				let onion_packet = msgs::OnionPacket {
+					version: 0,
+					public_key: next_packet_pk,
+					hop_data: new_packet_bytes,
+					hmac: next_hop_hmac,
+				};
+				PeeledPayment::Forward(ForwardedPayment{
+					short_channel_id,
+					amt_to_forward,
+					outgoing_cltv_value,
+					onion_packet,
+				})
+			} else {
+				return Err(());
+			}
+		},
+		Hop::Receive(inbound) => {
+			let payload: ReceivedPayment = inbound.try_into().map_err(|_| ())?;
+			PeeledPayment::Receive(payload)
+		},
+	};
+	Ok(peeled)
+}
+
 pub(crate) fn decode_next_untagged_hop<T, R: ReadableArgs<T>, N: NextPacketBytes>(shared_secret: [u8; 32], hop_data: &[u8], hmac_bytes: [u8; 32], read_args: T) -> Result<(R, Option<([u8; 32], N)>), OnionDecodeErr> {
 	decode_next_hop(shared_secret, hop_data, hmac_bytes, None, read_args)
 }
@@ -1019,7 +1193,8 @@ fn decode_next_hop<T, R: ReadableArgs<T>, N: NextPacketBytes>(shared_secret: [u8
 #[cfg(test)]
 mod tests {
 	use crate::io;
-	use crate::prelude::*;
+	use crate::ln::{PaymentPreimage, PaymentSecret};
+use crate::prelude::*;
 	use crate::ln::PaymentHash;
 	use crate::ln::features::{ChannelFeatures, NodeFeatures};
 	use crate::routing::router::{Path, Route, RouteHop};
@@ -1235,4 +1410,117 @@ mod tests {
 			writer.write_all(&self.data[..])
 		}
 	}
+
+	use crate::ln::channelmanager::RecipientOnionFields;
+	use crate::sign::KeysManager;
+	use super::{create_payment_onion, peel_payment_onion};
+	use super::{PeeledPayment, ReceivedPayment};
+
+	fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
+		SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
+		Vec<RouteHop>, u64, PaymentSecret,
+	) {
+		use core::convert::TryInto;
+		use super::{Sha256, Hash};
+
+		let session_priv_bytes = [42; 32];
+		let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
+		let total_amt_msat = 1000;
+		let cur_height = 1000;
+		let pay_secret = PaymentSecret([99; 32]);
+		let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
+		let preimage_bytes = [43; 32];
+		let preimage = PaymentPreimage(preimage_bytes);
+		let rhash = Sha256::hash(&preimage_bytes).to_vec();
+		let rhash_bytes: [u8; 32] = rhash.try_into().unwrap();
+		let payment_hash = PaymentHash(rhash_bytes);
+		let prng_seed = [44; 32];
+
+		// make a route alice -> bob -> charlie
+		let hop_fee = 1;
+		let recipient_amount = total_amt_msat - hop_fee;
+		let hops = vec![
+			RouteHop {
+				pubkey: hop_pk,
+				fee_msat: hop_fee,
+				cltv_expiry_delta: 0,
+				short_channel_id: 1,
+				node_features: NodeFeatures::empty(),
+				channel_features: ChannelFeatures::empty(),
+				maybe_announced_channel: false,
+			},
+			RouteHop {
+				pubkey: recipient_pk,
+				fee_msat: recipient_amount,
+				cltv_expiry_delta: 0,
+				short_channel_id: 2,
+				node_features: NodeFeatures::empty(),
+				channel_features: ChannelFeatures::empty(),
+				maybe_announced_channel: false,
+			}
+		];
+
+		(session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
+			prng_seed, hops, recipient_amount, pay_secret)
+	}
+
+	#[test]
+	fn create_and_peel_unblinded_payment() {
+		let secp_ctx = Secp256k1::new();
+
+		// let alice = make_keys_manager(&[1; 32]);
+		let bob = make_keys_manager(&[2; 32]);
+		let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
+		let charlie = make_keys_manager(&[3; 32]);
+		let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
+		
+		let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash, 
+			prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
+
+		let path = Path {
+			hops: hops,
+			blinded_tail: None,
+		};
+
+		let (_htlc_msat, _htlc_cltv, onion) = create_payment_onion(
+			&secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
+			payment_hash, Some(preimage), prng_seed
+		).unwrap();
+
+		// bob peels to find another onion
+		let next_onion = match peel_payment_onion(&onion, payment_hash, &&bob, &secp_ctx).unwrap() {
+			PeeledPayment::Receive(_) => panic!("should not be Receive"),
+			PeeledPayment::Forward(forwarded) => forwarded.onion_packet,
+		};
+
+		// charlie peels to find a received payment
+		let received = match peel_payment_onion(
+			&next_onion, payment_hash, &&charlie, &secp_ctx
+		).unwrap() {
+			PeeledPayment::Receive(received) => received,
+			PeeledPayment::Forward(_) => panic!("should not be a Forward"),
+		};
+
+		match received {
+			ReceivedPayment::Unblinded{
+				amt_msat, keysend_preimage, payment_secret, total_msat, payment_metadata,
+				custom_tlvs, cltv_expiry
+			} => {
+				assert_eq!(amt_msat, recipient_amount);
+				assert_eq!(keysend_preimage, Some(preimage.0));
+				assert_eq!(payment_secret, Some(pay_secret.0));
+				assert_eq!(total_msat, Some(total_amt_msat));
+				assert_eq!(payment_metadata, None);
+				assert_eq!(custom_tlvs, Vec::new());
+				assert_eq!(cltv_expiry, cur_height + 1);
+			},
+			ReceivedPayment::Blinded { .. } => panic!("Should not be Blinded"),
+		}
+
+	}
+
+	fn make_keys_manager(seed: &[u8; 32]) -> KeysManager {
+		KeysManager::new(seed, 42, 42)
+	}
+
 }

lightning/src/onion_message/mod.rs

@@ -28,6 +28,7 @@ mod functional_tests;
 
 // Re-export structs so they can be imported with just the `onion_message::` module prefix.
 pub use self::messenger::{CustomOnionMessageHandler, DefaultMessageRouter, Destination, MessageRouter, OnionMessageContents, OnionMessagePath, OnionMessenger, PeeledOnion, PendingOnionMessage, SendError};
+pub use self::messenger::{create_onion_message, peel_onion_message};
 #[cfg(not(c_bindings))]
 pub use self::messenger::{SimpleArcOnionMessenger, SimpleRefOnionMessenger};
 pub use self::offers::{OffersMessage, OffersMessageHandler};