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

Diff for: 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<PaidInvoice>,
 	},
 	/// 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()
@@ -2438,3 +2449,19 @@ impl<T: EventHandler> EventHandler for Arc<T> {
 		self.deref().handle_event(event)
 	}
 }
+
+/// Wrapper time to move the bolt12 invoice and the static
+/// invoice across the same event as a unique type.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum PaidInvoice {
+	/// Bolt12 invoice
+	Bolt12Invoice(crate::offers::invoice::Bolt12Invoice),
+	/// Static invoice
+	StaticInvoice(crate::offers::static_invoice::StaticInvoice),
+ }
+
+impl_writeable_tlv_based_enum_legacy!(PaidInvoice,
+	;
+	(0, Bolt12Invoice),
+	(2, StaticInvoice)
+);

Diff for: 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;

Diff for: 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);
 }
 

Diff for: lightning/src/ln/outbound_payment.rs

@@ -15,7 +15,8 @@ use bitcoin::secp256k1::{self, Secp256k1, SecretKey};
 use lightning_invoice::Bolt11Invoice;
 
 use crate::blinded_path::{IntroductionNode, NodeIdLookUp};
-use crate::events::{self, PaymentFailureReason};
+use crate::events::{self, PaymentFailureReason, PaidInvoice};
+use crate::offers::static_invoice::StaticInvoice;
 use crate::types::payment::{PaymentHash, PaymentPreimage, PaymentSecret};
 use crate::ln::channel_state::ChannelDetails;
 use crate::ln::channelmanager::{EventCompletionAction, HTLCSource, PaymentId};
@@ -34,10 +35,7 @@ use crate::util::time::Instant;
 use crate::util::ser::ReadableArgs;
 
 #[cfg(async_payments)]
-use {
-	crate::offers::invoice::{DerivedSigningPubkey, InvoiceBuilder},
-	crate::offers::static_invoice::StaticInvoice,
-};
+use crate::offers::invoice::{DerivedSigningPubkey, InvoiceBuilder};
 
 use core::fmt::{self, Display, Formatter};
 use core::ops::Deref;
@@ -108,7 +106,7 @@ pub(crate) enum PendingOutboundPayment {
 		invoice_request: Option<InvoiceRequest>,
 		// Storing the bolt12 invoice here to allow Proof of Payment after
 		// the payment is made.
-		bolt12_invoice: Option<Bolt12Invoice>,
+		bolt12_invoice: Option<PaidInvoice>,
 		custom_tlvs: Vec<(u64, Vec<u8>)>,
 		pending_amt_msat: u64,
 		/// Used to track the fee paid. Present iff the payment was serialized on 0.0.103+.
@@ -158,7 +156,7 @@ impl_writeable_tlv_based!(RetryableInvoiceRequest, {
 });
 
 impl PendingOutboundPayment {
-	fn bolt12_invoice(&self) -> Option<&Bolt12Invoice> {
+	fn bolt12_invoice(&self) -> Option<&PaidInvoice> {
 		match self {
 			PendingOutboundPayment::Retryable { bolt12_invoice, .. } => bolt12_invoice.as_ref(),
 			_ => None,
@@ -967,8 +965,9 @@ impl OutboundPayments {
 		if let Some(max_fee_msat) = params_config.max_total_routing_fee_msat {
 			route_params.max_total_routing_fee_msat = Some(max_fee_msat);
 		}
+		let invoice = PaidInvoice::Bolt12Invoice(invoice.clone());
 		self.send_payment_for_bolt12_invoice_internal(
-			payment_id, payment_hash, None, None, Some(invoice), route_params, retry_strategy, router, first_hops,
+			payment_id, payment_hash, None, None, Some(&invoice), route_params, retry_strategy, router, first_hops,
 			inflight_htlcs, entropy_source, node_signer, node_id_lookup, secp_ctx, best_block_height,
 			logger, pending_events, send_payment_along_path
 		)
@@ -979,7 +978,7 @@ impl OutboundPayments {
 	>(
 		&self, payment_id: PaymentId, payment_hash: PaymentHash,
 		keysend_preimage: Option<PaymentPreimage>, invoice_request: Option<&InvoiceRequest>,
-		bolt12_invoice: Option<&Bolt12Invoice>,
+		bolt12_invoice: Option<&PaidInvoice>,
 		mut route_params: RouteParameters, retry_strategy: Retry, router: &R,
 		first_hops: Vec<ChannelDetails>, inflight_htlcs: IH, entropy_source: &ES, node_signer: &NS,
 		node_id_lookup: &NL, secp_ctx: &Secp256k1<secp256k1::All>, best_block_height: u32, logger: &L,
@@ -1726,7 +1725,7 @@ impl OutboundPayments {
 		&self, payment_hash: PaymentHash, recipient_onion: RecipientOnionFields, payment_id: PaymentId,
 		keysend_preimage: Option<PaymentPreimage>, route: &Route, retry_strategy: Option<Retry>,
 		payment_params: Option<PaymentParameters>, entropy_source: &ES, best_block_height: u32,
-		bolt12_invoice: Option<Bolt12Invoice>
+		bolt12_invoice: Option<PaidInvoice>
 	) -> Result<Vec<[u8; 32]>, PaymentSendFailure> where ES::Target: EntropySource {
 		let mut pending_outbounds = self.pending_outbound_payments.lock().unwrap();
 		match pending_outbounds.entry(payment_id) {
@@ -1745,7 +1744,7 @@ impl OutboundPayments {
 	fn create_pending_payment<ES: Deref>(
 		payment_hash: PaymentHash, recipient_onion: RecipientOnionFields,
 		keysend_preimage: Option<PaymentPreimage>, invoice_request: Option<InvoiceRequest>,
-		bolt12_invoice: Option<Bolt12Invoice>, route: &Route, retry_strategy: Option<Retry>,
+		bolt12_invoice: Option<PaidInvoice>, route: &Route, retry_strategy: Option<Retry>,
 		payment_params: Option<PaymentParameters>, entropy_source: &ES, best_block_height: u32
 	) -> (PendingOutboundPayment, Vec<[u8; 32]>)
 	where
@@ -2028,6 +2027,7 @@ 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();
 			}

Diff for: lightning/src/offers/static_invoice.rs

@@ -33,7 +33,7 @@ use crate::offers::offer::{
 };
 use crate::offers::parse::{Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
 use crate::types::features::{Bolt12InvoiceFeatures, OfferFeatures};
-use crate::util::ser::{CursorReadable, Iterable, WithoutLength, Writeable, Writer};
+use crate::util::ser::{CursorReadable, Iterable, Readable, WithoutLength, Writeable, Writer};
 use crate::util::string::PrintableString;
 use bitcoin::address::Address;
 use bitcoin::constants::ChainHash;
@@ -70,6 +70,14 @@ pub struct StaticInvoice {
 	signature: Signature,
 }
 
+impl PartialEq for StaticInvoice {
+	fn eq(&self, other: &Self) -> bool {
+		self.bytes.eq(&other.bytes)
+	}
+}
+
+impl Eq for StaticInvoice {}
+
 /// The contents of a [`StaticInvoice`] for responding to an [`Offer`].
 ///
 /// [`Offer`]: crate::offers::offer::Offer
@@ -535,6 +543,13 @@ impl Writeable for StaticInvoice {
 	}
 }
 
+impl Readable for StaticInvoice {
+	fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		let bytes: WithoutLength<Vec<u8>> = Readable::read(reader)?;
+		Self::try_from(bytes.0).map_err(|_| DecodeError::InvalidValue)
+	}
+}
+
 impl TryFrom<Vec<u8>> for StaticInvoice {
 	type Error = Bolt12ParseError;