Add ability to receive payjoin transactions

Allows the node wallet to receive payjoin transactions as specified in
BIP78.

bindings/ldk_node.udl

@@ -180,6 +180,9 @@ enum NodeError {
 	"PayjoinRequestCreationFailed",
 	"PayjoinResponseProcessingFailed",
 	"PayjoinRequestTimeout",
+	"PayjoinReceiverUnavailable",
+	"PayjoinReceiverRequestValidationFailed",
+	"PayjoinReceiverEnrollementFailed"
 };
 
 dictionary NodeStatus {

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::payjoin_receiver::PayjoinReceiver;
 use crate::payment::store::PaymentStore;
 use crate::peer_store::PeerStore;
 use crate::tx_broadcaster::TransactionBroadcaster;
@@ -99,6 +100,13 @@ struct PayjoinSenderConfig {
 	payjoin_relay: String,
 }
 
+#[derive(Debug, Clone)]
+struct PayjoinReceiverConfig {
+	payjoin_relay: String,
+	payjoin_directory: String,
+	ohttp_keys: Option<String>,
+}
+
 impl Default for LiquiditySourceConfig {
 	fn default() -> Self {
 		Self { lsps2_service: None }
@@ -179,6 +187,7 @@ pub struct NodeBuilder {
 	gossip_source_config: Option<GossipSourceConfig>,
 	liquidity_source_config: Option<LiquiditySourceConfig>,
 	payjoin_sender_config: Option<PayjoinSenderConfig>,
+	payjoin_receiver_config: Option<PayjoinReceiverConfig>,
 }
 
 impl NodeBuilder {
@@ -195,13 +204,15 @@ impl NodeBuilder {
 		let gossip_source_config = None;
 		let liquidity_source_config = None;
 		let payjoin_sender_config = None;
+		let payjoin_receiver_config = None;
 		Self {
 			config,
 			entropy_source_config,
 			chain_data_source_config,
 			gossip_source_config,
 			liquidity_source_config,
 			payjoin_sender_config,
+			payjoin_receiver_config,
 		}
 	}
 
@@ -262,6 +273,15 @@ impl NodeBuilder {
 		self
 	}
 
+	/// Configures the [`Node`] instance to enable receiving payjoin transactions.
+	pub fn set_payjoin_receiver_config(
+		&mut self, payjoin_relay: String, payjoin_directory: String, ohttp_keys: Option<String>,
+	) -> &mut Self {
+		self.payjoin_receiver_config =
+			Some(PayjoinReceiverConfig { payjoin_relay, payjoin_directory, ohttp_keys });
+		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.
@@ -381,6 +401,7 @@ impl NodeBuilder {
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
 			self.payjoin_sender_config.as_ref(),
+			self.payjoin_receiver_config.as_ref(),
 			seed_bytes,
 			logger,
 			vss_store,
@@ -403,6 +424,7 @@ impl NodeBuilder {
 			self.gossip_source_config.as_ref(),
 			self.liquidity_source_config.as_ref(),
 			self.payjoin_sender_config.as_ref(),
+			self.payjoin_receiver_config.as_ref(),
 			seed_bytes,
 			logger,
 			kv_store,
@@ -475,6 +497,17 @@ impl ArcedNodeBuilder {
 		self.inner.write().unwrap().set_payjoin_sender_config(payjoin_relay);
 	}
 
+	/// Configures the [`Node`] instance to enable receiving payjoin transactions.
+	pub fn set_payjoin_receiver_config(
+		&mut self, payjoin_relay: String, payjoin_directory: String, ohttp_keys: Option<String>,
+	) {
+		self.inner.write().unwrap().set_payjoin_receiver_config(
+			payjoin_relay,
+			payjoin_directory,
+			ohttp_keys,
+		);
+	}
+
 	/// 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) {
@@ -544,7 +577,8 @@ fn build_with_store_internal(
 	config: Arc<Config>, chain_data_source_config: Option<&ChainDataSourceConfig>,
 	gossip_source_config: Option<&GossipSourceConfig>,
 	liquidity_source_config: Option<&LiquiditySourceConfig>,
-	payjoin_sender_config: Option<&PayjoinSenderConfig>, seed_bytes: [u8; 64],
+	payjoin_sender_config: Option<&PayjoinSenderConfig>,
+	payjoin_receiver_config: Option<&PayjoinReceiverConfig>, seed_bytes: [u8; 64],
 	logger: Arc<FilesystemLogger>, kv_store: Arc<DynStore>,
 ) -> Result<Node, BuildError> {
 	// Initialize the on-chain wallet and chain access
@@ -1010,6 +1044,44 @@ fn build_with_store_internal(
 		}
 	});
 
+	let payjoin_receiver = payjoin_receiver_config.as_ref().and_then(|prc| {
+		match (payjoin::Url::parse(&prc.payjoin_directory), payjoin::Url::parse(&prc.payjoin_relay))
+		{
+			(Ok(directory), Ok(relay)) => {
+				let ohttp_keys = match prc.ohttp_keys.clone() {
+					Some(keys) => {
+						let keys = match bitcoin::base64::decode(keys) {
+							Ok(keys) => keys,
+							Err(e) => {
+								log_info!(logger, "Failed to decode ohttp keys: the provided key is not a valid Base64 string {}", e);
+								return None;
+							},
+						};
+						match payjoin::OhttpKeys::decode(&keys) {
+							Ok(ohttp_keys) => Some(ohttp_keys),
+							Err(e) => {
+								log_info!(logger, "Failed to decode ohttp keys, make sure you provided a valid Ohttp Key as provided by the payjoin directory: {}", e);
+								return None;
+							},
+						}
+					},
+					None => None,
+				};
+				Some(Arc::new(PayjoinReceiver::new(
+					Arc::clone(&logger),
+					Arc::clone(&wallet),
+					directory,
+					relay,
+					ohttp_keys,
+				)))
+			},
+			_ => {
+				log_info!(logger, "The provided payjoin relay URL is invalid.");
+				None
+			},
+		}
+	});
+
 	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));
@@ -1030,6 +1102,7 @@ fn build_with_store_internal(
 		chain_monitor,
 		output_sweeper,
 		payjoin_sender,
+		payjoin_receiver,
 		peer_manager,
 		connection_manager,
 		keys_manager,

src/error.rs

@@ -97,6 +97,12 @@ pub enum Error {
 	PayjoinResponseProcessingFailed,
 	/// Payjoin request timed out.
 	PayjoinRequestTimeout,
+	/// Failed to access payjoin receiver object.
+	PayjoinReceiverUnavailable,
+	/// Failed to enroll payjoin receiver.
+	PayjoinReceiverEnrollementFailed,
+	/// Failed to validate an incoming payjoin request.
+	PayjoinReceiverRequestValidationFailed,
 }
 
 impl fmt::Display for Error {
@@ -175,6 +181,15 @@ impl fmt::Display for Error {
 			Self::PayjoinRequestTimeout => {
 				write!(f, "Payjoin receiver did not respond to our request within the timeout period. Notice they can still broadcast the original PSBT we shared with them")
 			},
+			Self::PayjoinReceiverUnavailable => {
+				write!(f, "Failed to access payjoin receiver object. Make sure you have enabled Payjoin receiving support.")
+			},
+			Self::PayjoinReceiverRequestValidationFailed => {
+				write!(f, "Failed to validate an incoming payjoin request. Payjoin sender request didnt pass the payjoin validation steps.")
+			},
+			Self::PayjoinReceiverEnrollementFailed => {
+				write!(f, "Failed to enroll payjoin receiver. Make sure the configured Payjoin directory & Payjoin relay are available.")
+			},
 		}
 	}
 }

src/io/utils.rs

@@ -511,6 +511,13 @@ pub(crate) fn check_namespace_key_validity(
 	Ok(())
 }
 
+pub(crate) fn ohttp_headers() -> reqwest::header::HeaderMap<reqwest::header::HeaderValue> {
+	let mut headers = reqwest::header::HeaderMap::new();
+	let header_value = reqwest::header::HeaderValue::from_static("message/ohttp-req");
+	headers.insert(reqwest::header::CONTENT_TYPE, header_value);
+	headers
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;

src/lib.rs

@@ -88,6 +88,7 @@ pub mod io;
 mod liquidity;
 mod logger;
 mod message_handler;
+mod payjoin_receiver;
 mod payjoin_sender;
 pub mod payment;
 mod peer_store;
@@ -131,6 +132,7 @@ use connection::ConnectionManager;
 use event::{EventHandler, EventQueue};
 use gossip::GossipSource;
 use liquidity::LiquiditySource;
+use payjoin_receiver::PayjoinReceiver;
 use payment::store::PaymentStore;
 use payment::{
 	Bolt11Payment, Bolt12Payment, OnchainPayment, PayjoinPayment, PaymentDetails,
@@ -187,6 +189,7 @@ pub struct Node {
 	peer_manager: Arc<PeerManager>,
 	connection_manager: Arc<ConnectionManager<Arc<FilesystemLogger>>>,
 	payjoin_sender: Option<Arc<PayjoinSender>>,
+	payjoin_receiver: Option<Arc<PayjoinReceiver>>,
 	keys_manager: Arc<KeysManager>,
 	network_graph: Arc<NetworkGraph>,
 	gossip_source: Arc<GossipSource>,
@@ -626,6 +629,28 @@ impl Node {
 			}
 		});
 
+		if let Some(payjoin_receiver) = &self.payjoin_receiver {
+			let mut stop_payjoin_server = self.stop_sender.subscribe();
+			let payjoin_receiver = Arc::clone(&payjoin_receiver);
+			let payjoin_check_interval = 5;
+			runtime.spawn(async move {
+				let mut payjoin_interval =
+					tokio::time::interval(Duration::from_secs(payjoin_check_interval));
+				payjoin_interval.reset();
+				payjoin_interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
+				loop {
+					tokio::select! {
+						_ = stop_payjoin_server.changed() => {
+							return;
+						}
+						_ = payjoin_interval.tick() => {
+							let _ = payjoin_receiver.process_payjoin_request().await;
+						}
+					}
+				}
+			});
+		}
+
 		let event_handler = Arc::new(EventHandler::new(
 			Arc::clone(&self.event_queue),
 			Arc::clone(&self.wallet),
@@ -938,9 +963,11 @@ impl Node {
 	#[cfg(not(feature = "uniffi"))]
 	pub fn payjoin_payment(&self) -> PayjoinPayment {
 		let payjoin_sender = self.payjoin_sender.as_ref();
+		let payjoin_receiver = self.payjoin_receiver.as_ref();
 		PayjoinPayment::new(
 			Arc::clone(&self.runtime),
 			payjoin_sender.map(Arc::clone),
+			payjoin_receiver.map(Arc::clone),
 			Arc::clone(&self.config),
 		)
 	}
@@ -956,9 +983,11 @@ impl Node {
 	#[cfg(feature = "uniffi")]
 	pub fn payjoin_payment(&self) -> PayjoinPayment {
 		let payjoin_sender = self.payjoin_sender.as_ref();
+		let payjoin_receiver = self.payjoin_receiver.as_ref();
 		PayjoinPayment::new(
 			Arc::clone(&self.runtime),
 			payjoin_sender.map(Arc::clone),
+			payjoin_receiver.map(Arc::clone),
 			Arc::clone(&self.config),
 		)
 	}