Serialize Trampoline payloads in outbound onions.

lightning/src/ln/features.rs

@@ -66,6 +66,8 @@
 //!      for more info).
 //! - `Keysend` - send funds to a node without an invoice
 //!     (see the [`Keysend` feature assignment proposal](https://github.com/lightning/bolts/issues/605#issuecomment-606679798) for more information).
+//! - `Trampoline` - supports receiving and forwarding Trampoline payments
+//!     (see the [`Trampoline` feature proposal](https://github.com/lightning/bolts/pull/836) for more information).
 //!
 //! LDK knows about the following features, but does not support them:
 //! - `AnchorsNonzeroFeeHtlcTx` - the initial version of anchor outputs, which was later found to be
@@ -152,6 +154,8 @@ mod sealed {
 		ChannelType | SCIDPrivacy,
 		// Byte 6
 		ZeroConf,
+		// Byte 7
+		Trampoline,
 	]);
 	define_context!(NodeContext, [
 		// Byte 0
@@ -168,6 +172,8 @@ mod sealed {
 		ChannelType | SCIDPrivacy,
 		// Byte 6
 		ZeroConf | Keysend,
+		// Byte 7
+		Trampoline,
 	]);
 	define_context!(ChannelContext, []);
 	define_context!(Bolt11InvoiceContext, [
@@ -185,6 +191,8 @@ mod sealed {
 		,
 		// Byte 6
 		PaymentMetadata,
+		// Byte 7
+		Trampoline,
 	]);
 	define_context!(OfferContext, []);
 	define_context!(InvoiceRequestContext, []);
@@ -420,6 +428,9 @@ mod sealed {
 	define_feature!(55, Keysend, [NodeContext],
 		"Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
 		supports_keysend, requires_keysend);
+	define_feature!(57, Trampoline, [InitContext, NodeContext, Bolt11InvoiceContext],
+		"Feature flags for Trampoline routing.", set_trampoline_routing_optional, set_trampoline_routing_required,
+		supports_trampoline_routing, requires_trampoline_routing);
 	// Note: update the module-level docs when a new feature bit is added!
 
 	#[cfg(test)]

lightning/src/ln/msgs.rs

@@ -1654,7 +1654,7 @@ mod fuzzy_internal_msgs {
 	use crate::prelude::*;
 	use crate::ln::{PaymentPreimage, PaymentSecret};
 	use crate::ln::features::BlindedHopFeatures;
-	use super::FinalOnionHopData;
+	use super::{FinalOnionHopData, TrampolineOnionPacket};
 
 	// These types aren't intended to be pub, but are exposed for direct fuzzing (as we deserialize
 	// them from untrusted input):
@@ -1698,6 +1698,13 @@ mod fuzzy_internal_msgs {
 			amt_to_forward: u64,
 			outgoing_cltv_value: u32,
 		},
+		#[allow(unused)]
+		TrampolineEntrypoint {
+			amt_to_forward: u64,
+			outgoing_cltv_value: u32,
+			multipath_trampoline_data: Option<FinalOnionHopData>,
+			trampoline_packet: TrampolineOnionPacket,
+		},
 		Receive {
 			payment_data: Option<FinalOnionHopData>,
 			payment_metadata: Option<Vec<u8>>,
@@ -1765,6 +1772,52 @@ impl fmt::Debug for OnionPacket {
 	}
 }
 
+/// BOLT 4 onion packet including hop data for the next peer.
+#[derive(Clone, Hash, PartialEq, Eq)]
+pub struct TrampolineOnionPacket {
+	/// Bolt 04 version number
+	pub version: u8,
+	/// A random sepc256k1 point, used to build the ECDH shared secret to decrypt hop_data
+	pub public_key: PublicKey,
+	/// Encrypted payload for the next hop
+	//
+	// Unlike the onion packets used for payments, Trampoline onion packets have to be shorter than
+	// 1300 bytes. The expected default is 650 bytes.
+	// TODO: if 650 ends up being the most common size, optimize this to be:
+	// enum { ThirteenHundred([u8; 650]), VarLen(Vec<u8>) }
+	pub hop_data: Vec<u8>,
+	/// HMAC to verify the integrity of hop_data
+	pub hmac: [u8; 32],
+}
+
+impl onion_utils::Packet for TrampolineOnionPacket {
+	type Data = Vec<u8>;
+	fn new(public_key: PublicKey, hop_data: Vec<u8>, hmac: [u8; 32]) -> Self {
+		Self {
+			version: 0,
+			public_key,
+			hop_data,
+			hmac,
+		}
+	}
+}
+
+impl Writeable for TrampolineOnionPacket {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.version.write(w)?;
+		self.public_key.write(w)?;
+		w.write_all(&self.hop_data)?;
+		self.hmac.write(w)?;
+		Ok(())
+	}
+}
+
+impl Debug for TrampolineOnionPacket {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		f.write_fmt(format_args!("TrampolineOnionPacket version {} with hmac {:?}", self.version, &self.hmac[..]))
+	}
+}
+
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
 pub(crate) struct OnionErrorPacket {
 	// This really should be a constant size slice, but the spec lets these things be up to 128KB?
@@ -2478,6 +2531,17 @@ impl Writeable for OutboundOnionPayload {
 					(6, short_channel_id, required)
 				});
 			},
+			Self::TrampolineEntrypoint {
+				amt_to_forward, outgoing_cltv_value, ref multipath_trampoline_data,
+				ref trampoline_packet
+			} => {
+				_encode_varint_length_prefixed_tlv!(w, {
+					(2, HighZeroBytesDroppedBigSize(*amt_to_forward), required),
+					(4, HighZeroBytesDroppedBigSize(*outgoing_cltv_value), required),
+					(8, multipath_trampoline_data, option),
+					(20, trampoline_packet, required)
+				});
+			},
 			Self::Receive {
 				ref payment_data, ref payment_metadata, ref keysend_preimage, sender_intended_htlc_amt_msat,
 				cltv_expiry_height, ref custom_tlvs,
@@ -3043,10 +3107,10 @@ mod tests {
 	use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 	use crate::ln::ChannelId;
 	use crate::ln::features::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, NodeFeatures};
-	use crate::ln::msgs::{self, FinalOnionHopData, OnionErrorPacket, CommonOpenChannelFields, CommonAcceptChannelFields};
+	use crate::ln::msgs::{self, FinalOnionHopData, OnionErrorPacket, CommonOpenChannelFields, CommonAcceptChannelFields, TrampolineOnionPacket};
 	use crate::ln::msgs::SocketAddress;
 	use crate::routing::gossip::{NodeAlias, NodeId};
-	use crate::util::ser::{Writeable, Readable, ReadableArgs, Hostname, TransactionU16LenLimited};
+	use crate::util::ser::{BigSize, Hostname, Readable, ReadableArgs, TransactionU16LenLimited, Writeable};
 	use crate::util::test_utils;
 
 	use bitcoin::hashes::hex::FromHex;
@@ -4338,6 +4402,64 @@ mod tests {
 		} else { panic!(); }
 	}
 
+	#[test]
+	fn encoding_final_onion_hop_data_with_trampoline_packet() {
+		let secp_ctx = Secp256k1::new();
+		let (_private_key, public_key) = get_keys_from!("0101010101010101010101010101010101010101010101010101010101010101", secp_ctx);
+
+		let compressed_public_key = public_key.serialize();
+		assert_eq!(compressed_public_key.len(), 33);
+
+		let trampoline_packet = TrampolineOnionPacket {
+			version: 0,
+			public_key,
+			hop_data: vec![1; 650], // this should be the standard encoded length
+			hmac: [2; 32],
+		};
+		let encoded_trampoline_packet = trampoline_packet.encode();
+		assert_eq!(encoded_trampoline_packet.len(), 716);
+
+		let msg = msgs::OutboundOnionPayload::TrampolineEntrypoint {
+			multipath_trampoline_data: None,
+			amt_to_forward: 0x0badf00d01020304,
+			outgoing_cltv_value: 0xffffffff,
+			trampoline_packet,
+		};
+		let encoded_payload = msg.encode();
+
+		let trampoline_type_bytes = &encoded_payload[19..=19];
+		let mut trampoline_type_cursor = Cursor::new(trampoline_type_bytes);
+		let trampoline_type_big_size: BigSize = Readable::read(&mut trampoline_type_cursor).unwrap();
+		assert_eq!(trampoline_type_big_size.0, 20);
+
+		let trampoline_length_bytes = &encoded_payload[20..=22];
+		let mut trampoline_length_cursor = Cursor::new(trampoline_length_bytes);
+		let trampoline_length_big_size: BigSize = Readable::read(&mut trampoline_length_cursor).unwrap();
+		assert_eq!(trampoline_length_big_size.0, encoded_trampoline_packet.len() as u64);
+	}
+
+	#[test]
+	fn encoding_final_onion_hop_data_with_eclair_trampoline_packet() {
+		let public_key = PublicKey::from_slice(&<Vec<u8>>::from_hex("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()).unwrap();
+		let hop_data = <Vec<u8>>::from_hex("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").unwrap();
+		let hmac_vector = <Vec<u8>>::from_hex("bb079bfc4b35190eee9f59a1d7b41ba2f773179f322dafb4b1af900c289ebd6c").unwrap();
+		let mut hmac = [0; 32];
+		hmac.copy_from_slice(&hmac_vector);
+
+		let compressed_public_key = public_key.serialize();
+		assert_eq!(compressed_public_key.len(), 33);
+
+		let trampoline_packet = TrampolineOnionPacket {
+			version: 0,
+			public_key,
+			hop_data,
+			hmac,
+		};
+		let encoded_trampoline_packet = trampoline_packet.encode();
+		let expected_eclair_trampoline_packet = <Vec<u8>>::from_hex("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").unwrap();
+		assert_eq!(encoded_trampoline_packet, expected_eclair_trampoline_packet);
+	}
+
 	#[test]
 	fn query_channel_range_end_blocknum() {
 		let tests: Vec<(u32, u32, u32)> = vec![