Support receiving async payment HTLCs

After a lot of setup in prior commits, here we finally finish support for
receiving HTLCs paid to static BOLT 12 invoices. It amounts to verifying the
invoice request contained within the onion and generating the right
PaymentPurpose for the claimable event.

Author: valentinewallace

lightning/src/events/mod.rs

@@ -28,6 +28,7 @@ use crate::ln::msgs;
 use crate::ln::types::ChannelId;
 use crate::types::payment::{PaymentPreimage, PaymentHash, PaymentSecret};
 use crate::offers::invoice::Bolt12Invoice;
+use crate::offers::invoice_request::VerifiedInvoiceRequest;
 use crate::onion_message::messenger::Responder;
 use crate::routing::gossip::NetworkUpdate;
 use crate::routing::router::{BlindedTail, Path, RouteHop, RouteParameters};
@@ -180,7 +181,7 @@ impl PaymentPurpose {
 
 	pub(crate) fn from_parts(
 		payment_preimage: Option<PaymentPreimage>, payment_secret: PaymentSecret,
-		payment_context: Option<PaymentContext>,
+		payment_context: Option<PaymentContext>, invreq: Option<VerifiedInvoiceRequest>,
 	) -> Result<Self, ()> {
 		match payment_context {
 			None => {
@@ -203,11 +204,18 @@ impl PaymentPurpose {
 					payment_context: context,
 				})
 			},
-			Some(PaymentContext::AsyncBolt12Offer(_context)) => {
-				// This code will change to return Self::Bolt12OfferPayment when we add support for async
-				// receive.
-				Err(())
-			},
+			Some(PaymentContext::AsyncBolt12Offer(_)) => {
+				let invoice_request = invreq.ok_or(())?;
+				if payment_preimage.is_none() { return Err(()) }
+				Ok(PaymentPurpose::Bolt12OfferPayment {
+					payment_preimage,
+					payment_secret,
+					payment_context: Bolt12OfferContext {
+						offer_id: invoice_request.offer_id,
+						invoice_request: invoice_request.fields(),
+					},
+				})
+			}
 		}
 	}
 }
@@ -1190,12 +1198,12 @@ pub enum Event {
 		/// events generated or serialized by versions prior to 0.0.122.
 		next_user_channel_id: Option<u128>,
 		/// The node id of the previous node.
-		/// 
+		///
 		/// This is only `None` for HTLCs received prior to 0.1 or for events serialized by
 		/// versions prior to 0.1
 		prev_node_id: Option<PublicKey>,
 		/// The node id of the next node.
-		/// 
+		///
 		/// This is only `None` for HTLCs received prior to 0.1 or for events serialized by
 		/// versions prior to 0.1
 		next_node_id: Option<PublicKey>,
@@ -1872,7 +1880,7 @@ impl MaybeReadable for Event {
 						(13, payment_id, option),
 					});
 					let purpose = match payment_secret {
-						Some(secret) => PaymentPurpose::from_parts(payment_preimage, secret, payment_context)
+						Some(secret) => PaymentPurpose::from_parts(payment_preimage, secret, payment_context, None)
 							.map_err(|()| msgs::DecodeError::InvalidValue)?,
 						None if payment_preimage.is_some() => PaymentPurpose::SpontaneousPayment(payment_preimage.unwrap()),
 						None => return Err(msgs::DecodeError::InvalidValue),

lightning/src/ln/channelmanager.rs

@@ -36,7 +36,7 @@ use crate::events::FundingInfo;
 use crate::blinded_path::message::{AsyncPaymentsContext, MessageContext, OffersContext};
 use crate::blinded_path::NodeIdLookUp;
 use crate::blinded_path::message::{BlindedMessagePath, MessageForwardNode};
-use crate::blinded_path::payment::{BlindedPaymentPath, Bolt12OfferContext, Bolt12RefundContext, PaymentConstraints, PaymentContext, UnauthenticatedReceiveTlvs};
+use crate::blinded_path::payment::{AsyncBolt12OfferContext, BlindedPaymentPath, Bolt12OfferContext, Bolt12RefundContext, PaymentConstraints, PaymentContext, UnauthenticatedReceiveTlvs};
 use crate::chain;
 use crate::chain::{Confirm, ChannelMonitorUpdateStatus, Watch, BestBlock};
 use crate::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator, LowerBoundedFeeEstimator};
@@ -89,7 +89,6 @@ use crate::util::ser::TransactionU16LenLimited;
 use crate::util::logger::{Level, Logger, WithContext};
 use crate::util::errors::APIError;
 #[cfg(async_payments)] use {
-	crate::blinded_path::payment::AsyncBolt12OfferContext,
 	crate::offers::offer::Amount,
 	crate::offers::static_invoice::{DEFAULT_RELATIVE_EXPIRY as STATIC_INVOICE_DEFAULT_RELATIVE_EXPIRY, StaticInvoice, StaticInvoiceBuilder},
 };
@@ -6010,7 +6009,7 @@ where
 								let blinded_failure = routing.blinded_failure();
 								let (
 									cltv_expiry, onion_payload, payment_data, payment_context, phantom_shared_secret,
-									mut onion_fields, has_recipient_created_payment_secret, _invoice_request_opt
+									mut onion_fields, has_recipient_created_payment_secret, invoice_request_opt
 								) = match routing {
 									PendingHTLCRouting::Receive {
 										payment_data, payment_metadata, payment_context,
@@ -6224,6 +6223,7 @@ where
 											payment_preimage,
 											payment_data.payment_secret,
 											payment_context,
+											None,
 										) {
 											Ok(purpose) => purpose,
 											Err(()) => {
@@ -6232,14 +6232,50 @@ where
 										};
 										check_total_value!(purpose);
 									},
-									OnionPayload::Spontaneous(preimage) => {
-										if payment_context.is_some() {
-											if !matches!(payment_context, Some(PaymentContext::AsyncBolt12Offer(_))) {
-												log_trace!(self.logger, "Failing new HTLC with payment_hash {}: received a keysend payment to a non-async payments context {:#?}", payment_hash, payment_context);
+									OnionPayload::Spontaneous(keysend_preimage) => {
+										let purpose = if let Some(PaymentContext::AsyncBolt12Offer(
+											AsyncBolt12OfferContext { offer_nonce }
+										)) = payment_context {
+											let payment_data = match payment_data {
+												Some(data) => data,
+												None => {
+													debug_assert!(false, "We checked that payment_data is Some above");
+													fail_htlc!(claimable_htlc, payment_hash);
+												},
+											};
+
+											let verified_invreq = match invoice_request_opt
+												.and_then(|invreq| invreq.verify_using_recipient_data(
+													offer_nonce, &self.inbound_payment_key, &self.secp_ctx
+												).ok())
+											{
+												Some(verified_invreq) => {
+													if let Some(invreq_amt_msat) = verified_invreq.amount_msats() {
+														if payment_data.total_msat < invreq_amt_msat {
+															fail_htlc!(claimable_htlc, payment_hash);
+														}
+													}
+													verified_invreq
+												},
+												None => {
+													fail_htlc!(claimable_htlc, payment_hash);
+												}
+											};
+											match events::PaymentPurpose::from_parts(
+												Some(keysend_preimage), payment_data.payment_secret, payment_context,
+												Some(verified_invreq),
+											) {
+												Ok(purpose) => purpose,
+												Err(()) => {
+													fail_htlc!(claimable_htlc, payment_hash);
+												}
 											}
+										} else if payment_context.is_some() {
+											log_trace!(self.logger, "Failing new HTLC with payment_hash {}: received a keysend payment to a non-async payments context {:#?}", payment_hash, payment_context);
 											fail_htlc!(claimable_htlc, payment_hash);
-										}
-										let purpose = events::PaymentPurpose::SpontaneousPayment(preimage);
+										} else {
+											events::PaymentPurpose::SpontaneousPayment(keysend_preimage)
+										};
 										check_total_value!(purpose);
 									}
 								}