Allow to send payjoin transactions

Implements the payjoin sender as describe in BIP77.

This would allow the on chain wallet linked to LDK node to send payjoin
transactions.

Cargo.toml

@@ -69,6 +69,7 @@ tokio = { version = "1.37", default-features = false, features = [ "rt-multi-thr
 esplora-client = { version = "0.6", default-features = false }
 libc = "0.2"
 uniffi = { version = "0.26.0", features = ["build"], optional = true }
+payjoin = { version = "0.16.0", default-features = false, features = ["send", "v2"] }
 
 [target.'cfg(vss)'.dependencies]
 vss-client = "0.2"
@@ -85,6 +86,9 @@ bitcoincore-rpc = { version = "0.17.0", default-features = false }
 proptest = "1.0.0"
 regex = "1.5.6"
 
+payjoin = { version = "0.16.0", default-features = false, features = ["send", "v2", "receive"] }
+reqwest = { version = "0.11", default-features = false, features = ["json", "rustls-tls", "blocking"] }
+
 [target.'cfg(not(no_download))'.dev-dependencies]
 electrsd = { version = "0.26.0", features = ["legacy", "esplora_a33e97e1", "bitcoind_25_0"] }
 

bindings/ldk_node.udl

@@ -64,6 +64,7 @@ interface Node {
 	SpontaneousPayment spontaneous_payment();
 	OnchainPayment onchain_payment();
 	UnifiedQrPayment unified_qr_payment();
+	PayjoinPayment payjoin_payment();
 	[Throws=NodeError]
 	void connect(PublicKey node_id, SocketAddress address, boolean persist);
 	[Throws=NodeError]
@@ -156,6 +157,13 @@ interface UnifiedQrPayment {
     QrPaymentResult send([ByRef]string uri_str);
 };
 
+interface PayjoinPayment {
+	[Throws=NodeError]
+	void send(string payjoin_uri);
+	[Throws=NodeError]
+	void send_with_amount(string payjoin_uri, u64 amount_sats);
+};
+
 [Error]
 enum NodeError {
 	"AlreadyRunning",
@@ -206,6 +214,12 @@ enum NodeError {
 	"InsufficientFunds",
 	"LiquiditySourceUnavailable",
 	"LiquidityFeeTooHigh",
+	"PayjoinUnavailable",
+	"PayjoinUriInvalid",
+	"PayjoinRequestMissingAmount",
+	"PayjoinRequestCreationFailed",
+	"PayjoinRequestSendingFailed",
+	"PayjoinResponseProcessingFailed",
 };
 
 dictionary NodeStatus {
@@ -231,6 +245,7 @@ enum BuildError {
 	"InvalidSystemTime",
 	"InvalidChannelMonitor",
 	"InvalidListeningAddresses",
+	"InvalidPayjoinConfig",
 	"ReadFailed",
 	"WriteFailed",
 	"StoragePathAccessFailed",
@@ -248,6 +263,11 @@ interface Event {
 	ChannelPending(ChannelId channel_id, UserChannelId user_channel_id, ChannelId former_temporary_channel_id, PublicKey counterparty_node_id, OutPoint funding_txo);
 	ChannelReady(ChannelId channel_id, UserChannelId user_channel_id, PublicKey? counterparty_node_id);
 	ChannelClosed(ChannelId channel_id, UserChannelId user_channel_id, PublicKey? counterparty_node_id, ClosureReason? reason);
+	PayjoinPaymentPending(Txid txid, u64 amount_sats, ScriptBuf recipient);
+	PayjoinPaymentBroadcasted(Txid txid, u64 amount_sats, ScriptBuf recipient);
+	PayjoinPaymentSuccessful(Txid txid, u64 amount_sats, ScriptBuf recipient);
+	PayjoinPaymentFailed(Txid txid, u64 amount_sats, ScriptBuf recipient, PayjoinPaymentFailureReason reason);
+	PayjoinPaymentOriginalPsbtBroadcasted(Txid txid, u64 amount_sats, ScriptBuf recipient);
 };
 
 enum PaymentFailureReason {
@@ -259,6 +279,12 @@ enum PaymentFailureReason {
 	"UnexpectedError",
 };
 
+enum PayjoinPaymentFailureReason {
+	"Timeout",
+	"RequestSendingFailed",
+	"ResponseProcessingFailed",
+};
+
 [Enum]
 interface ClosureReason {
 	CounterpartyForceClosed(UntrustedString peer_msg);
@@ -284,6 +310,7 @@ interface PaymentKind {
 	Bolt12Offer(PaymentHash? hash, PaymentPreimage? preimage, PaymentSecret? secret, OfferId offer_id);
 	Bolt12Refund(PaymentHash? hash, PaymentPreimage? preimage, PaymentSecret? secret);
 	Spontaneous(PaymentHash hash, PaymentPreimage? preimage);
+	Payjoin();
 };
 
 [Enum]
@@ -516,3 +543,6 @@ typedef string Mnemonic;
 
 [Custom]
 typedef string UntrustedString;
+
+[Custom]
+typedef string ScriptBuf;

src/builder.rs

@@ -11,6 +11,7 @@ use crate::io::sqlite_store::SqliteStore;
 use crate::liquidity::LiquiditySource;
 use crate::logger::{log_error, log_info, FilesystemLogger, Logger};
 use crate::message_handler::NodeCustomMessageHandler;
+use crate::payment::payjoin::handler::PayjoinHandler;
 use crate::payment::store::PaymentStore;
 use crate::peer_store::PeerStore;
 use crate::tx_broadcaster::TransactionBroadcaster;
@@ -93,6 +94,11 @@ struct LiquiditySourceConfig {
 	lsps2_service: Option<(SocketAddress, PublicKey, Option<String>)>,
 }
 
+#[derive(Debug, Clone)]
+struct PayjoinConfig {
+	payjoin_relay: payjoin::Url,
+}
+
 impl Default for LiquiditySourceConfig {
 	fn default() -> Self {
 		Self { lsps2_service: None }
@@ -132,6 +138,8 @@ pub enum BuildError {
 	WalletSetupFailed,
 	/// We failed to setup the logger.
 	LoggerSetupFailed,
+	/// Invalid Payjoin configuration.
+	InvalidPayjoinConfig,
 }
 
 impl fmt::Display for BuildError {
@@ -152,6 +160,10 @@ impl fmt::Display for BuildError {
 			Self::KVStoreSetupFailed => write!(f, "Failed to setup KVStore."),
 			Self::WalletSetupFailed => write!(f, "Failed to setup onchain wallet."),
 			Self::LoggerSetupFailed => write!(f, "Failed to setup the logger."),
+			Self::InvalidPayjoinConfig => write!(
+				f,
+				"Invalid Payjoin configuration. Make sure the provided arguments are valid URLs."
+			),
 		}
 	}
 }
@@ -172,6 +184,7 @@ pub struct NodeBuilder {
 	chain_data_source_config: Option<ChainDataSourceConfig>,
 	gossip_source_config: Option<GossipSourceConfig>,
 	liquidity_source_config: Option<LiquiditySourceConfig>,
+	payjoin_config: Option<PayjoinConfig>,
 }
 
 impl NodeBuilder {
@@ -187,12 +200,14 @@ impl NodeBuilder {
 		let chain_data_source_config = None;
 		let gossip_source_config = None;
 		let liquidity_source_config = None;
+		let payjoin_config = None;
 		Self {
 			config,
 			entropy_source_config,
 			chain_data_source_config,
 			gossip_source_config,
 			liquidity_source_config,
+			payjoin_config,
 		}
 	}
 
@@ -247,6 +262,14 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to enable payjoin transactions.
+	pub fn set_payjoin_config(&mut self, payjoin_relay: String) -> Result<&mut Self, BuildError> {
+		let payjoin_relay =
+			payjoin::Url::parse(&payjoin_relay).map_err(|_| BuildError::InvalidPayjoinConfig)?;
+		self.payjoin_config = Some(PayjoinConfig { payjoin_relay });
+		Ok(self)
+	}
+
 	/// Configures the [`Node`] instance to source its inbound liquidity from the given
 	/// [LSPS2](https://github.com/BitcoinAndLightningLayerSpecs/lsp/blob/main/LSPS2/README.md)
 	/// service.
@@ -365,6 +388,7 @@ impl NodeBuilder {
 			self.chain_data_source_config.as_ref(),
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
+			self.payjoin_config.as_ref(),
 			seed_bytes,
 			logger,
 			vss_store,
@@ -386,6 +410,7 @@ impl NodeBuilder {
 			self.chain_data_source_config.as_ref(),
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
+			self.payjoin_config.as_ref(),
 			seed_bytes,
 			logger,
 			kv_store,
@@ -453,6 +478,11 @@ impl ArcedNodeBuilder {
 		self.inner.write().unwrap().set_gossip_source_p2p();
 	}
 
+	/// Configures the [`Node`] instance to enable payjoin transactions.
+	pub fn set_payjoin_config(&self, payjoin_relay: String) -> Result<(), BuildError> {
+		self.inner.write().unwrap().set_payjoin_config(payjoin_relay).map(|_| ())
+	}
+
 	/// Configures the [`Node`] instance to source its gossip data from the given RapidGossipSync
 	/// server.
 	pub fn set_gossip_source_rgs(&self, rgs_server_url: String) {
@@ -521,8 +551,9 @@ impl ArcedNodeBuilder {
 fn build_with_store_internal(
 	config: Arc<Config>, chain_data_source_config: Option<&ChainDataSourceConfig>,
 	gossip_source_config: Option<&GossipSourceConfig>,
-	liquidity_source_config: Option<&LiquiditySourceConfig>, seed_bytes: [u8; 64],
-	logger: Arc<FilesystemLogger>, kv_store: Arc<DynStore>,
+	liquidity_source_config: Option<&LiquiditySourceConfig>,
+	payjoin_config: Option<&PayjoinConfig>, seed_bytes: [u8; 64], logger: Arc<FilesystemLogger>,
+	kv_store: Arc<DynStore>,
 ) -> Result<Node, BuildError> {
 	// Initialize the on-chain wallet and chain access
 	let xprv = bitcoin::bip32::ExtendedPrivKey::new_master(config.network.into(), &seed_bytes)
@@ -966,6 +997,17 @@ fn build_with_store_internal(
 	let (stop_sender, _) = tokio::sync::watch::channel(());
 	let (event_handling_stopped_sender, _) = tokio::sync::watch::channel(());
 
+	let payjoin_handler = payjoin_config.map(|pj_config| {
+		Arc::new(PayjoinHandler::new(
+			Arc::clone(&tx_sync),
+			Arc::clone(&event_queue),
+			Arc::clone(&logger),
+			pj_config.payjoin_relay.clone(),
+			Arc::clone(&payment_store),
+			Arc::clone(&wallet),
+		))
+	});
+
 	let is_listening = Arc::new(AtomicBool::new(false));
 	let latest_wallet_sync_timestamp = Arc::new(RwLock::new(None));
 	let latest_onchain_wallet_sync_timestamp = Arc::new(RwLock::new(None));
@@ -987,6 +1029,7 @@ fn build_with_store_internal(
 		channel_manager,
 		chain_monitor,
 		output_sweeper,
+		payjoin_handler,
 		peer_manager,
 		connection_manager,
 		keys_manager,

src/config.rs

@@ -40,6 +40,15 @@ pub(crate) const RESOLVED_CHANNEL_MONITOR_ARCHIVAL_INTERVAL: u32 = 6;
 // The time in-between peer reconnection attempts.
 pub(crate) const PEER_RECONNECTION_INTERVAL: Duration = Duration::from_secs(10);
 
+// The time before a payjoin http request is considered timed out.
+pub(crate) const PAYJOIN_REQUEST_TIMEOUT: Duration = Duration::from_secs(30);
+
+// The duration between retries of a payjoin http request.
+pub(crate) const PAYJOIN_RETRY_INTERVAL: Duration = Duration::from_secs(3);
+
+// The total duration of retrying to send a payjoin http request.
+pub(crate) const PAYJOIN_REQUEST_TOTAL_DURATION: Duration = Duration::from_secs(24 * 60 * 60);
+
 // The time in-between RGS sync attempts.
 pub(crate) const RGS_SYNC_INTERVAL: Duration = Duration::from_secs(60 * 60);
 

src/error.rs

@@ -99,6 +99,18 @@ pub enum Error {
 	LiquiditySourceUnavailable,
 	/// The given operation failed due to the LSP's required opening fee being too high.
 	LiquidityFeeTooHigh,
+	/// Failed to access Payjoin object.
+	PayjoinUnavailable,
+	/// Payjoin URI is invalid.
+	PayjoinUriInvalid,
+	/// Amount is neither user-provided nor defined in the URI.
+	PayjoinRequestMissingAmount,
+	/// Failed to build a Payjoin request.
+	PayjoinRequestCreationFailed,
+	/// Failed to send Payjoin request.
+	PayjoinRequestSendingFailed,
+	/// Payjoin response processing failed.
+	PayjoinResponseProcessingFailed,
 }
 
 impl fmt::Display for Error {
@@ -168,6 +180,30 @@ impl fmt::Display for Error {
 			Self::LiquidityFeeTooHigh => {
 				write!(f, "The given operation failed due to the LSP's required opening fee being too high.")
 			},
+			Self::PayjoinUnavailable => {
+				write!(
+					f,
+					"Failed to access Payjoin object. Make sure you have enabled Payjoin support."
+				)
+			},
+			Self::PayjoinRequestMissingAmount => {
+				write!(
+					f,
+					"Amount is neither user-provided nor defined in the provided Payjoin URI."
+				)
+			},
+			Self::PayjoinRequestCreationFailed => {
+				write!(f, "Failed construct a Payjoin request")
+			},
+			Self::PayjoinUriInvalid => {
+				write!(f, "The provided Payjoin URI is invalid")
+			},
+			Self::PayjoinRequestSendingFailed => {
+				write!(f, "Failed to send Payjoin request")
+			},
+			Self::PayjoinResponseProcessingFailed => {
+				write!(f, "Payjoin receiver responded to our request with an invalid response")
+			},
 		}
 	}
 }