add the bolt12 invoice to the PaymentSend event

To enable proof of payment, we need to share the bolt12 invoice with the library user.

This is already possible if we `manually_handle_bolt12_invoices`, but
this approach requires a significant amount of work from the user.

This commit adds the bolt12 invoice to the PaymentSend event when
the payment is completed. This allows the user to always have the option to
perform proof of payment.

Link: lightningdevkit#3344
Signed-off-by: Vincenzo Palazzo <[email protected]>

Author: vincenzopalazzo

lightning/src/events/mod.rs

@@ -949,6 +949,13 @@ pub enum Event {
 		///
 		/// [`Route::get_total_fees`]: crate::routing::router::Route::get_total_fees
 		fee_paid_msat: Option<u64>,
+		/// The bolt12 invoice that was paid. `None` if the payment was a non-bolt12 payment.
+		///
+		/// The bolt12 invoice is useful for proof of payment because it contains the
+		/// payment hash. A third party can verify that the payment was made by
+		/// showing the invoice and confirming that the payment hash matches
+		/// the hash of the payment preimage.
+		bolt12_invoice: Option<Bolt12Invoice>,
 	},
 	/// Indicates an outbound payment failed. Individual [`Event::PaymentPathFailed`] events
 	/// provide failure information for each path attempt in the payment, including retries.
@@ -1556,14 +1563,15 @@ impl Writeable for Event {
 					(13, payment_id, option),
 				});
 			},
-			&Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref amount_msat, ref fee_paid_msat } => {
+			&Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref amount_msat, ref fee_paid_msat, ref bolt12_invoice } => {
 				2u8.write(writer)?;
 				write_tlv_fields!(writer, {
 					(0, payment_preimage, required),
 					(1, payment_hash, required),
 					(3, payment_id, option),
 					(5, fee_paid_msat, option),
 					(7, amount_msat, option),
+					(9, bolt12_invoice, option),
 				});
 			},
 			&Event::PaymentPathFailed {
@@ -1898,12 +1906,14 @@ impl MaybeReadable for Event {
 					let mut payment_id = None;
 					let mut amount_msat = None;
 					let mut fee_paid_msat = None;
+					let mut bolt12_invoice = None;
 					read_tlv_fields!(reader, {
 						(0, payment_preimage, required),
 						(1, payment_hash, option),
 						(3, payment_id, option),
 						(5, fee_paid_msat, option),
 						(7, amount_msat, option),
+						(9, bolt12_invoice, option),
 					});
 					if payment_hash.is_none() {
 						payment_hash = Some(PaymentHash(Sha256::hash(&payment_preimage.0[..]).to_byte_array()));
@@ -1914,6 +1924,7 @@ impl MaybeReadable for Event {
 						payment_hash: payment_hash.unwrap(),
 						amount_msat,
 						fee_paid_msat,
+						bolt12_invoice,
 					}))
 				};
 				f()

lightning/src/ln/functional_test_utils.rs

@@ -35,6 +35,7 @@ use crate::util::test_channel_signer::SignerOp;
 use crate::util::test_utils;
 use crate::util::test_utils::{TestChainMonitor, TestScorer, TestKeysInterface};
 use crate::util::ser::{ReadableArgs, Writeable};
+use crate::offers::invoice::Bolt12Invoice;
 
 use bitcoin::{Weight, WPubkeyHash};
 use bitcoin::amount::Amount;
@@ -3116,10 +3117,11 @@ pub fn claim_payment_along_route(args: ClaimAlongRouteArgs) {
 	}
 }
 
-pub fn claim_payment<'a, 'b, 'c>(origin_node: &Node<'a, 'b, 'c>, expected_route: &[&Node<'a, 'b, 'c>], our_payment_preimage: PaymentPreimage) {
+pub fn claim_payment<'a, 'b, 'c>(origin_node: &Node<'a, 'b, 'c>, expected_route: &[&Node<'a, 'b, 'c>], our_payment_preimage: PaymentPreimage) -> Option<Bolt12Invoice> {
 	claim_payment_along_route(
 		ClaimAlongRouteArgs::new(origin_node, &[expected_route], our_payment_preimage)
 	);
+	None
 }
 
 pub const TEST_FINAL_CLTV: u32 = 70;

lightning/src/ln/offers_tests.rs

@@ -168,7 +168,7 @@ fn route_bolt12_payment<'a, 'b, 'c>(
 }
 
 fn claim_bolt12_payment<'a, 'b, 'c>(
-	node: &Node<'a, 'b, 'c>, path: &[&Node<'a, 'b, 'c>], expected_payment_context: PaymentContext
+	node: &Node<'a, 'b, 'c>, path: &[&Node<'a, 'b, 'c>], expected_payment_context: PaymentContext, invoice: &Bolt12Invoice
 ) {
 	let recipient = &path[path.len() - 1];
 	let payment_purpose = match get_event!(recipient, Event::PaymentClaimable) {
@@ -188,7 +188,9 @@ fn claim_bolt12_payment<'a, 'b, 'c>(
 		},
 		_ => panic!("Unexpected payment purpose: {:?}", payment_purpose),
 	}
-	claim_payment(node, path, payment_preimage);
+	if let Some(inv) = claim_payment(node, path, payment_preimage) {
+		assert_eq!(inv, invoice.to_owned());
+	};
 }
 
 fn extract_offer_nonce<'a, 'b, 'c>(node: &Node<'a, 'b, 'c>, message: &OnionMessage) -> Nonce {
@@ -597,7 +599,7 @@ fn creates_and_pays_for_offer_using_two_hop_blinded_path() {
 	route_bolt12_payment(david, &[charlie, bob, alice], &invoice);
 	expect_recent_payment!(david, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context);
+	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context, &invoice);
 	expect_recent_payment!(david, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -680,7 +682,7 @@ fn creates_and_pays_for_refund_using_two_hop_blinded_path() {
 	route_bolt12_payment(david, &[charlie, bob, alice], &invoice);
 	expect_recent_payment!(david, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context);
+	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context, &invoice);
 	expect_recent_payment!(david, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -747,7 +749,7 @@ fn creates_and_pays_for_offer_using_one_hop_blinded_path() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -803,7 +805,7 @@ fn creates_and_pays_for_refund_using_one_hop_blinded_path() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -857,7 +859,7 @@ fn pays_for_offer_without_blinded_paths() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -900,7 +902,7 @@ fn pays_for_refund_without_blinded_paths() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -1138,7 +1140,7 @@ fn creates_and_pays_for_offer_with_retry() {
 	}
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -1209,7 +1211,7 @@ fn pays_bolt12_invoice_asynchronously() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 
 	assert_eq!(
@@ -1289,7 +1291,7 @@ fn creates_offer_with_blinded_path_using_unannounced_introduction_node() {
 	route_bolt12_payment(bob, &[alice], &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Pending, payment_id);
 
-	claim_bolt12_payment(bob, &[alice], payment_context);
+	claim_bolt12_payment(bob, &[alice], payment_context, &invoice);
 	expect_recent_payment!(bob, RecentPaymentDetails::Fulfilled, payment_id);
 }
 
@@ -2145,7 +2147,7 @@ fn fails_paying_invoice_more_than_once() {
 	assert!(david.node.get_and_clear_pending_msg_events().is_empty());
 
 	// Complete paying the first invoice
-	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context);
+	claim_bolt12_payment(david, &[charlie, bob, alice], payment_context, &invoice1);
 	expect_recent_payment!(david, RecentPaymentDetails::Fulfilled, payment_id);
 }
 

lightning/src/ln/outbound_payment.rs

@@ -2028,6 +2028,7 @@ impl OutboundPayments {
 					payment_hash,
 					amount_msat,
 					fee_paid_msat,
+					bolt12_invoice: payment.get().bolt12_invoice().cloned(),
 				}, Some(ev_completion_action.clone())));
 				payment.get_mut().mark_fulfilled();
 			}