Fix tx-add-input serialization

Author: optout21

lightning/src/ln/msgs.rs

@@ -29,7 +29,7 @@ use bitcoin::hash_types::Txid;
 use bitcoin::script::ScriptBuf;
 use bitcoin::secp256k1::ecdsa::Signature;
 use bitcoin::secp256k1::PublicKey;
-use bitcoin::{secp256k1, Witness};
+use bitcoin::{secp256k1, Transaction, Witness};
 
 use crate::blinded_path::payment::{
 	BlindedPaymentTlvs, ForwardTlvs, ReceiveTlvs, UnauthenticatedReceiveTlvs,
@@ -2664,15 +2664,60 @@ impl_writeable_msg!(SpliceLocked, {
 	splice_txid,
 }, {});
 
-impl_writeable_msg!(TxAddInput, {
-	channel_id,
-	serial_id,
-	prevtx_out,
-	sequence,
-}, {
-	(0, prevtx, option),
-	(1, shared_input_txid, option), // `funding_txid`
-});
+impl Writeable for TxAddInput {
+	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+		self.channel_id.write(w)?;
+		self.serial_id.write(w)?;
+		if let Some(prevtx) = self.prevtx.as_ref() {
+			debug_assert!(self.shared_input_txid.is_none());
+			prevtx.write(w)?;
+		} else {
+			debug_assert!(self.shared_input_txid.is_some());
+			0u16.write(w)?;
+		}
+		self.prevtx_out.write(w)?;
+		self.sequence.write(w)?;
+
+		if let Some(shared_input_txid) = self.shared_input_txid.as_ref() {
+			encode_tlv_stream!(w, { (0, shared_input_txid, required) });
+		} else {
+			encode_tlv_stream!(w, {});
+		}
+
+		Ok(())
+	}
+}
+
+impl LengthReadable for TxAddInput {
+	fn read_from_fixed_length_buffer<R: LengthLimitedRead>(r: &mut R) -> Result<Self, DecodeError> {
+		let channel_id = Readable::read(r)?;
+		let serial_id = Readable::read(r)?;
+		let prevtx_len = <u16 as Readable>::read(r)?;
+		let mut prevtx = None;
+		if prevtx_len > 0 {
+			let mut tx_reader = FixedLengthReader::new(r, prevtx_len as u64);
+			let tx: Transaction = Readable::read(&mut tx_reader)?;
+			if tx_reader.bytes_remain() {
+				return Err(DecodeError::BadLengthDescriptor);
+			}
+			prevtx =
+				Some(TransactionU16LenLimited::new(tx).map_err(|_| DecodeError::InvalidValue)?);
+		}
+		let prevtx_out = Readable::read(r)?;
+		let sequence = Readable::read(r)?;
+
+		let mut shared_input_txid = None;
+		if prevtx_len > 0 {
+			decode_tlv_stream!(r, {});
+		} else {
+			decode_tlv_stream!(r, {
+				(0, shared_input_txid, required),
+			});
+		}
+
+		Ok(Self { channel_id, serial_id, prevtx, prevtx_out, sequence, shared_input_txid })
+	}
+}
 
 impl_writeable_msg!(TxAddOutput, {
 	channel_id,
@@ -5230,10 +5275,28 @@ mod tests {
 			}).unwrap()),
 			prevtx_out: 305419896,
 			sequence: 305419896,
-			shared_input_txid: Some(Txid::from_str("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e").unwrap()),
+			shared_input_txid: None,
+		};
+		let encoded_value = tx_add_input.encode();
+		let target_value = "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";
+		assert_eq!(encoded_value.as_hex().to_string(), target_value);
+	}
+
+	#[test]
+	fn encoding_tx_add_input_shared() {
+		let tx_add_input = msgs::TxAddInput {
+			channel_id: ChannelId::from_bytes([2; 32]),
+			serial_id: 4886718345,
+			prevtx: None,
+			prevtx_out: 305419896,
+			sequence: 305419896,
+			shared_input_txid: Some(
+				Txid::from_str("c2d4449afa8d26140898dd54d3390b057ba2a5afcf03ba29d7dc0d8b9ffe966e")
+					.unwrap(),
+			),
 		};
 		let encoded_value = tx_add_input.encode();
-		let target_value = "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";
+		let target_value = "020202020202020202020202020202020202020202020202020202020202020200000001234567890000123456781234567800206e96fe9f8b0ddcd729ba03cfafa5a27b050b39d354dd980814268dfa9a44d4c2";
 		assert_eq!(encoded_value.as_hex().to_string(), target_value);
 	}