feat: allow self payment

This PR solves issue #2462. If we asked to
pay an invoice that we generated ourselves. We
generate PaymentSent and PaymentClaimable event
and mark the payment as fulfilled in our set
of outbound payments.

This PR is important because we realized users
can easily screw up self payments when they implement
it themselves. See here: https://lists.linuxfoundation.org/pipermail/lightning-dev/2023-June/003983.html

Author: vladimirfomene

lightning/src/ln/channelmanager.rs

@@ -401,7 +401,7 @@ pub enum FailureCode {
 }
 
 impl Into<u16> for FailureCode {
-    fn into(self) -> u16 {
+	fn into(self) -> u16 {
 		match self {
 			FailureCode::TemporaryNodeFailure => 0x2000 | 2,
 			FailureCode::RequiredNodeFeatureMissing => 0x4000 | 0x2000 | 3,
@@ -3396,7 +3396,7 @@ where
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 		self.pending_outbound_payments
 			.send_payment_with_route(route, payment_hash, recipient_onion, payment_id,
-				&self.entropy_source, &self.node_signer, best_block_height,
+				&self.entropy_source, &self.node_signer, best_block_height, &self.pending_events,
 				|args| self.send_payment_along_path(args))
 	}
 
@@ -3406,7 +3406,7 @@ where
 		let best_block_height = self.best_block.read().unwrap().height();
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 		self.pending_outbound_payments
-			.send_payment(payment_hash, recipient_onion, payment_id, retry_strategy, route_params,
+			.send_payment(payment_hash,recipient_onion, payment_id, retry_strategy, route_params,
 				&self.router, self.list_usable_channels(), || self.compute_inflight_htlcs(),
 				&self.entropy_source, &self.node_signer, best_block_height, &self.logger,
 				&self.pending_events, |args| self.send_payment_along_path(args))
@@ -3418,7 +3418,7 @@ where
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 		self.pending_outbound_payments.test_send_payment_internal(route, payment_hash, recipient_onion,
 			keysend_preimage, payment_id, recv_value_msat, onion_session_privs, &self.node_signer,
-			best_block_height, |args| self.send_payment_along_path(args))
+			best_block_height, &self.pending_events, |args| self.send_payment_along_path(args))
 	}
 
 	#[cfg(test)]
@@ -3482,7 +3482,7 @@ where
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 		self.pending_outbound_payments.send_spontaneous_payment_with_route(
 			route, payment_preimage, recipient_onion, payment_id, &self.entropy_source,
-			&self.node_signer, best_block_height, |args| self.send_payment_along_path(args))
+			&self.node_signer, best_block_height, &self.pending_events, |args| self.send_payment_along_path(args))
 	}
 
 	/// Similar to [`ChannelManager::send_spontaneous_payment`], but will automatically find a route
@@ -3509,7 +3509,7 @@ where
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
 		self.pending_outbound_payments.send_probe(path, self.probing_cookie_secret,
 			&self.entropy_source, &self.node_signer, best_block_height,
-			|args| self.send_payment_along_path(args))
+			&self.pending_events, |args| self.send_payment_along_path(args))
 	}
 
 	/// Returns whether a payment with the given [`PaymentHash`] and [`PaymentId`] is, in fact, a
@@ -5708,7 +5708,7 @@ where
 
 		let per_peer_state = self.per_peer_state.read().unwrap();
 		let peer_state_mutex = per_peer_state.get(counterparty_node_id)
-		    .ok_or_else(|| {
+			.ok_or_else(|| {
 				debug_assert!(false);
 				MsgHandleErrInternal::send_err_msg_no_close(format!("Can't find a peer matching the passed counterparty node_id {}", counterparty_node_id), msg.temporary_channel_id.clone())
 			})?;

lightning/src/ln/outbound_payment.rs

@@ -14,12 +14,12 @@ use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::secp256k1::{self, Secp256k1, SecretKey};
 
 use crate::sign::{EntropySource, NodeSigner, Recipient};
-use crate::events::{self, PaymentFailureReason};
+use crate::events::{self, PaymentFailureReason, Event, PaymentPurpose};
 use crate::ln::{PaymentHash, PaymentPreimage, PaymentSecret};
 use crate::ln::channelmanager::{ChannelDetails, EventCompletionAction, HTLCSource, PaymentId};
 use crate::ln::onion_utils::{DecodedOnionFailure, HTLCFailReason};
 use crate::offers::invoice::Bolt12Invoice;
-use crate::routing::router::{InFlightHtlcs, Path, PaymentParameters, Route, RouteParameters, Router};
+use crate::routing::router::{InFlightHtlcs, Path, PaymentParameters, Route, RouteParameters, Router, Payee};
 use crate::util::errors::APIError;
 use crate::util::logger::Logger;
 use crate::util::time::Time;
@@ -650,7 +650,7 @@ impl OutboundPayments {
 	pub(super) fn send_payment_with_route<ES: Deref, NS: Deref, F>(
 		&self, route: &Route, payment_hash: PaymentHash, recipient_onion: RecipientOnionFields,
 		payment_id: PaymentId, entropy_source: &ES, node_signer: &NS, best_block_height: u32,
-		send_payment_along_path: F
+		pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>, send_payment_along_path: F
 	) -> Result<(), PaymentSendFailure>
 	where
 		ES::Target: EntropySource,
@@ -659,7 +659,7 @@ impl OutboundPayments {
 	{
 		let onion_session_privs = self.add_new_pending_payment(payment_hash, recipient_onion.clone(), payment_id, None, route, None, None, entropy_source, best_block_height)?;
 		self.pay_route_internal(route, payment_hash, recipient_onion, None, payment_id, None,
-			onion_session_privs, node_signer, best_block_height, &send_payment_along_path)
+			onion_session_privs, node_signer, best_block_height, pending_events, &send_payment_along_path)
 			.map_err(|e| { self.remove_outbound_if_all_failed(payment_id, &e); e })
 	}
 
@@ -690,7 +690,8 @@ impl OutboundPayments {
 	pub(super) fn send_spontaneous_payment_with_route<ES: Deref, NS: Deref, F>(
 		&self, route: &Route, payment_preimage: Option<PaymentPreimage>,
 		recipient_onion: RecipientOnionFields, payment_id: PaymentId, entropy_source: &ES,
-		node_signer: &NS, best_block_height: u32, send_payment_along_path: F
+		node_signer: &NS, best_block_height: u32, pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>,
+		send_payment_along_path: F
 	) -> Result<PaymentHash, PaymentSendFailure>
 	where
 		ES::Target: EntropySource,
@@ -704,7 +705,7 @@ impl OutboundPayments {
 			payment_id, Some(preimage), &route, None, None, entropy_source, best_block_height)?;
 
 		match self.pay_route_internal(route, payment_hash, recipient_onion, Some(preimage),
-			payment_id, None, onion_session_privs, node_signer, best_block_height, &send_payment_along_path
+			payment_id, None, onion_session_privs, node_signer, best_block_height, pending_events, &send_payment_along_path
 		) {
 			Ok(()) => Ok(payment_hash),
 			Err(e) => {
@@ -849,8 +850,9 @@ impl OutboundPayments {
 			}
 		}
 
+		let payer_pubkey = node_signer.get_node_id(Recipient::Node).unwrap();
 		let route = router.find_route_with_id(
-			&node_signer.get_node_id(Recipient::Node).unwrap(), &route_params,
+			&payer_pubkey, &route_params,
 			Some(&first_hops.iter().collect::<Vec<_>>()), inflight_htlcs(),
 			payment_hash, payment_id,
 		).map_err(|_| {
@@ -869,7 +871,7 @@ impl OutboundPayments {
 			})?;
 
 		let res = self.pay_route_internal(&route, payment_hash, recipient_onion, keysend_preimage, payment_id, None,
-			onion_session_privs, node_signer, best_block_height, &send_payment_along_path);
+			onion_session_privs, node_signer, best_block_height, pending_events, &send_payment_along_path);
 		log_info!(logger, "Sending payment with id {} and hash {} returned {:?}",
 			payment_id, payment_hash, res);
 		if let Err(e) = res {
@@ -1021,7 +1023,7 @@ impl OutboundPayments {
 		};
 		let res = self.pay_route_internal(&route, payment_hash, recipient_onion, keysend_preimage,
 			payment_id, Some(total_msat), onion_session_privs, node_signer, best_block_height,
-			&send_payment_along_path);
+			pending_events, &send_payment_along_path);
 		log_info!(logger, "Result retrying payment id {}: {:?}", &payment_id, res);
 		if let Err(e) = res {
 			self.handle_pay_route_err(e, payment_id, payment_hash, route, route_params, router, first_hops, inflight_htlcs, entropy_source, node_signer, best_block_height, logger, pending_events, send_payment_along_path);
@@ -1107,7 +1109,7 @@ impl OutboundPayments {
 
 	pub(super) fn send_probe<ES: Deref, NS: Deref, F>(
 		&self, path: Path, probing_cookie_secret: [u8; 32], entropy_source: &ES, node_signer: &NS,
-		best_block_height: u32, send_payment_along_path: F
+		best_block_height: u32, pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>, send_payment_along_path: F
 	) -> Result<(PaymentHash, PaymentId), PaymentSendFailure>
 	where
 		ES::Target: EntropySource,
@@ -1131,7 +1133,7 @@ impl OutboundPayments {
 			entropy_source, best_block_height)?;
 
 		match self.pay_route_internal(&route, payment_hash, RecipientOnionFields::spontaneous_empty(),
-			None, payment_id, None, onion_session_privs, node_signer, best_block_height, &send_payment_along_path
+			None, payment_id, None, onion_session_privs, node_signer, best_block_height, pending_events, &send_payment_along_path
 		) {
 			Ok(()) => Ok((payment_hash, payment_id)),
 			Err(e) => {
@@ -1238,7 +1240,7 @@ impl OutboundPayments {
 		&self, route: &Route, payment_hash: PaymentHash, recipient_onion: RecipientOnionFields,
 		keysend_preimage: Option<PaymentPreimage>, payment_id: PaymentId, recv_value_msat: Option<u64>,
 		onion_session_privs: Vec<[u8; 32]>, node_signer: &NS, best_block_height: u32,
-		send_payment_along_path: &F
+		pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>, send_payment_along_path: &F
 	) -> Result<(), PaymentSendFailure>
 	where
 		NS::Target: NodeSigner,
@@ -1252,6 +1254,42 @@ impl OutboundPayments {
 		{
 			return Err(PaymentSendFailure::ParameterError(APIError::APIMisuseError{err: "Payment secret is required for multi-path payments".to_owned()}));
 		}
+
+		if let Some(path) = route.paths.get(0) {
+			// handle self payment if path doesn't have a blinded tail.
+			if path.blinded_tail.is_none() {
+				let last_hop = path.hops.last().unwrap();
+				if node_signer.get_node_id(Recipient::Node).unwrap() == last_hop.pubkey {
+					let payment_secret = match recipient_onion.payment_secret {
+						Some(secret) => secret,
+						None => PaymentSecret([0; 32])
+					};
+	
+					let payment_preimage = PaymentPreimage([0; 32]);
+					let payment_purpose = PaymentPurpose::InvoicePayment {
+						payment_preimage: Some(payment_preimage),
+						payment_secret,
+					};
+					
+					let mut pending_outbounds_lock = self.pending_outbound_payments.lock().unwrap();
+					let payment = pending_outbounds_lock.get_mut(&payment_id).unwrap();
+					payment.mark_fulfilled();
+	
+					let mut pending_events_lock = pending_events.lock().unwrap();
+					pending_events_lock.push_back((Event::PaymentSent { payment_id: Some(payment_id), payment_preimage,
+								payment_hash, fee_paid_msat: None }, None));
+					let amt_to_receive = match &route.route_params {
+						Some(route_params) => route_params.final_value_msat,
+						None => if recv_value_msat.is_some() { recv_value_msat.unwrap() } else { 0 },
+					};
+					pending_events_lock.push_back((Event::PaymentClaimable { receiver_node_id: Some(last_hop.pubkey), payment_hash,
+								onion_fields: Some(recipient_onion), amount_msat: amt_to_receive, counterparty_skimmed_fee_msat: 0,
+								purpose: payment_purpose, via_channel_id: None, via_user_channel_id: None, claim_deadline: None }, None));
+					return Ok(());
+				}
+			}
+		}
+
 		let mut total_value = 0;
 		let our_node_id = node_signer.get_node_id(Recipient::Node).unwrap(); // TODO no unwrap
 		let mut path_errs = Vec::with_capacity(route.paths.len());
@@ -1346,15 +1384,15 @@ impl OutboundPayments {
 		&self, route: &Route, payment_hash: PaymentHash, recipient_onion: RecipientOnionFields,
 		keysend_preimage: Option<PaymentPreimage>, payment_id: PaymentId, recv_value_msat: Option<u64>,
 		onion_session_privs: Vec<[u8; 32]>, node_signer: &NS, best_block_height: u32,
-		send_payment_along_path: F
+		pending_events: &Mutex<VecDeque<(events::Event, Option<EventCompletionAction>)>>, send_payment_along_path: F
 	) -> Result<(), PaymentSendFailure>
 	where
 		NS::Target: NodeSigner,
 		F: Fn(SendAlongPathArgs) -> Result<(), APIError>,
 	{
 		self.pay_route_internal(route, payment_hash, recipient_onion, keysend_preimage, payment_id,
 			recv_value_msat, onion_session_privs, node_signer, best_block_height,
-			&send_payment_along_path)
+			pending_events, &send_payment_along_path)
 			.map_err(|e| { self.remove_outbound_if_all_failed(payment_id, &e); e })
 	}
 

lightning/src/routing/router.rs

@@ -1466,7 +1466,17 @@ where L::Target: Logger {
 	let our_node_id = NodeId::from_pubkey(&our_node_pubkey);
 
 	if payee_node_id_opt.map_or(false, |payee| payee == our_node_id) {
-		return Err(LightningError{err: "Cannot generate a route to ourselves".to_owned(), action: ErrorAction::IgnoreError});
+		let dummy_path = Path { hops: vec![RouteHop {
+			pubkey: our_node_pubkey.clone(),
+			short_channel_id: 0,
+			node_features: NodeFeatures::empty(),
+			channel_features: ChannelFeatures::empty(),
+			fee_msat: 0,
+			cltv_expiry_delta: 0,
+			maybe_announced_channel: false,
+
+		}], blinded_tail: None };
+		return Ok(Route { paths: vec![dummy_path], route_params: Some(route_params.clone()) });
 	}
 
 	if final_value_msat > MAX_VALUE_MSAT {