Split OffersContext::OutboundPayment into InRefund/InInvReq

TheBlueMatt · TheBlueMatt · commit b60ba66aa1b4 · 2025-11-09T23:18:35.000Z
Because they end up both being used to validate a `Bolt12Invoice`,
we ended up with a single `OffersContext` both for inclusion in a
`Refund` and an `InvoiceRequest`. However, this is ambiguous, and
while it doesn't seem like an issue, it also seems like a nice
property to only use a given `OffersContext` in one place.

Further, in the next commit, we use `OffersContext` to figure out
what we're building a blinded path for and changing behavior based
on it, so its nice to be unambiguous.

Thus, we split the single existing context into
`OutboundPaymentInRefund` and `OutboundPaymentInInvReq`.
diff --git a/lightning/src/blinded_path/message.rs b/lightning/src/blinded_path/message.rs
@@ -416,28 +416,45 @@ pub enum OffersContext {
 		/// Useful to timeout async recipients that are no longer supported as clients.
 		path_absolute_expiry: Duration,
 	},
-	/// Context used by a [`BlindedMessagePath`] within a [`Refund`] or as a reply path for an
-	/// [`InvoiceRequest`].
+	/// Context used by a [`BlindedMessagePath`] within a [`Refund`].
 	///
 	/// This variant is intended to be received when handling a [`Bolt12Invoice`] or an
 	/// [`InvoiceError`].
 	///
 	/// [`Refund`]: crate::offers::refund::Refund
-	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 	/// [`InvoiceError`]: crate::offers::invoice_error::InvoiceError
-	OutboundPayment {
-		/// Payment ID used when creating a [`Refund`] or [`InvoiceRequest`].
+	OutboundPaymentInRefund {
+		/// Payment ID used when creating a [`Refund`].
 		///
 		/// [`Refund`]: crate::offers::refund::Refund
-		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 		payment_id: PaymentId,
 
-		/// A nonce used for authenticating that a [`Bolt12Invoice`] is for a valid [`Refund`] or
-		/// [`InvoiceRequest`] and for deriving their signing keys.
+		/// A nonce used for authenticating that a [`Bolt12Invoice`] is for a valid [`Refund`] and
+		/// for deriving its signing keys.
 		///
 		/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 		/// [`Refund`]: crate::offers::refund::Refund
+		nonce: Nonce,
+	},
+	/// Context used by a [`BlindedMessagePath`] as a reply path for an [`InvoiceRequest`].
+	///
+	/// This variant is intended to be received when handling a [`Bolt12Invoice`] or an
+	/// [`InvoiceError`].
+	///
+	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+	/// [`InvoiceError`]: crate::offers::invoice_error::InvoiceError
+	OutboundPaymentInInvReq {
+		/// Payment ID used when creating an [`InvoiceRequest`].
+		///
+		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+		payment_id: PaymentId,
+
+		/// A nonce used for authenticating that a [`Bolt12Invoice`] is for a valid
+		/// [`InvoiceRequest`] and for deriving its signing keys.
+		///
+		/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 		/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 		nonce: Nonce,
 	},
@@ -619,7 +636,7 @@ impl_writeable_tlv_based_enum!(OffersContext,
 	(0, InvoiceRequest) => {
 		(0, nonce, required),
 	},
-	(1, OutboundPayment) => {
+	(1, OutboundPaymentInRefund) => {
 		(0, payment_id, required),
 		(1, nonce, required),
 	},
@@ -631,6 +648,10 @@ impl_writeable_tlv_based_enum!(OffersContext,
 		(2, invoice_slot, required),
 		(4, path_absolute_expiry, required),
 	},
+	(4, OutboundPaymentInInvReq) => {
+		(0, payment_id, required),
+		(1, nonce, required),
+	},
 );
 
 impl_writeable_tlv_based_enum!(AsyncPaymentsContext,
diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
@@ -5593,29 +5593,12 @@ where
 	pub fn send_payment_for_bolt12_invoice(
 		&self, invoice: &Bolt12Invoice, context: Option<&OffersContext>,
 	) -> Result<(), Bolt12PaymentError> {
-		match self.verify_bolt12_invoice(invoice, context) {
+		match self.flow.verify_bolt12_invoice(invoice, context) {
 			Ok(payment_id) => self.send_payment_for_verified_bolt12_invoice(invoice, payment_id),
 			Err(()) => Err(Bolt12PaymentError::UnexpectedInvoice),
 		}
 	}
 
-	fn verify_bolt12_invoice(
-		&self, invoice: &Bolt12Invoice, context: Option<&OffersContext>,
-	) -> Result<PaymentId, ()> {
-		let secp_ctx = &self.secp_ctx;
-		let expanded_key = &self.inbound_payment_key;
-
-		match context {
-			None if invoice.is_for_refund_without_paths() => {
-				invoice.verify_using_metadata(expanded_key, secp_ctx)
-			},
-			Some(&OffersContext::OutboundPayment { payment_id, nonce, .. }) => {
-				invoice.verify_using_payer_data(payment_id, nonce, expanded_key, secp_ctx)
-			},
-			_ => Err(()),
-		}
-	}
-
 	fn send_payment_for_verified_bolt12_invoice(
 		&self, invoice: &Bolt12Invoice, payment_id: PaymentId,
 	) -> Result<(), Bolt12PaymentError> {
@@ -15366,7 +15349,7 @@ where
 			},
 			OffersMessage::StaticInvoice(invoice) => {
 				let payment_id = match context {
-					Some(OffersContext::OutboundPayment { payment_id, .. }) => payment_id,
+					Some(OffersContext::OutboundPaymentInInvReq { payment_id, .. }) => payment_id,
 					_ => return None
 				};
 				let res = self.initiate_async_payment(&invoice, payment_id);
@@ -15382,7 +15365,8 @@ where
 				log_trace!(logger, "Received invoice_error: {}", invoice_error);
 
 				match context {
-					Some(OffersContext::OutboundPayment { payment_id, .. }) => {
+					Some(OffersContext::OutboundPaymentInInvReq { payment_id, .. })
+					|Some(OffersContext::OutboundPaymentInRefund { payment_id, .. }) => {
 						self.abandon_payment_with_reason(
 							payment_id, PaymentFailureReason::InvoiceRequestRejected,
 						);
diff --git a/lightning/src/offers/flow.rs b/lightning/src/offers/flow.rs
@@ -495,11 +495,12 @@ where
 		Ok(InvreqResponseInstructions::SendInvoice(invoice_request))
 	}
 
-	/// Verifies a [`Bolt12Invoice`] using the provided [`OffersContext`] or the invoice's payer metadata,
-	/// returning the corresponding [`PaymentId`] if successful.
+	/// Verifies a [`Bolt12Invoice`] using the provided [`OffersContext`] or the invoice's payer
+	/// metadata, returning the corresponding [`PaymentId`] if successful.
 	///
-	/// - If an [`OffersContext::OutboundPayment`] with a `nonce` is provided, verification is performed
-	///   using this to form the payer metadata.
+	/// - If an [`OffersContext::OutboundPaymentInInvReq`] or
+	///   [`OffersContext::OutboundPaymentInRefund`] with a `nonce` is provided, verification is
+	///   performed using this to form the payer metadata.
 	/// - If no context is provided and the invoice corresponds to a [`Refund`] without blinded paths,
 	///   verification is performed using the [`Bolt12Invoice::payer_metadata`].
 	/// - If neither condition is met, verification fails.
@@ -513,8 +514,19 @@ where
 			None if invoice.is_for_refund_without_paths() => {
 				invoice.verify_using_metadata(expanded_key, secp_ctx)
 			},
-			Some(&OffersContext::OutboundPayment { payment_id, nonce, .. }) => {
-				invoice.verify_using_payer_data(payment_id, nonce, expanded_key, secp_ctx)
+			Some(&OffersContext::OutboundPaymentInInvReq { payment_id, nonce, .. }) => {
+				if invoice.is_for_offer() {
+					invoice.verify_using_payer_data(payment_id, nonce, expanded_key, secp_ctx)
+				} else {
+					Err(())
+				}
+			},
+			Some(&OffersContext::OutboundPaymentInRefund { payment_id, nonce, .. }) => {
+				if invoice.is_for_refund() {
+					invoice.verify_using_payer_data(payment_id, nonce, expanded_key, secp_ctx)
+				} else {
+					Err(())
+				}
 			},
 			_ => Err(()),
 		}
@@ -680,7 +692,8 @@ where
 		let secp_ctx = &self.secp_ctx;
 
 		let nonce = Nonce::from_entropy_source(entropy);
-		let context = MessageContext::Offers(OffersContext::OutboundPayment { payment_id, nonce });
+		let context =
+			MessageContext::Offers(OffersContext::OutboundPaymentInRefund { payment_id, nonce });
 
 		// Create the base builder with common properties
 		let mut builder = RefundBuilder::deriving_signing_pubkey(
@@ -1116,7 +1129,8 @@ where
 		&self, invoice_request: InvoiceRequest, payment_id: PaymentId, nonce: Nonce,
 		peers: Vec<MessageForwardNode>,
 	) -> Result<(), Bolt12SemanticError> {
-		let context = MessageContext::Offers(OffersContext::OutboundPayment { payment_id, nonce });
+		let context =
+			MessageContext::Offers(OffersContext::OutboundPaymentInInvReq { payment_id, nonce });
 		let reply_paths = self
 			.create_blinded_paths(peers, context)
 			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
diff --git a/lightning/src/offers/invoice.rs b/lightning/src/offers/invoice.rs
@@ -778,6 +778,19 @@ struct InvoiceFields {
 }
 
 macro_rules! invoice_accessors { ($self: ident, $contents: expr) => {
+	/// Whether the invoice was created in response to a [`Refund`].
+	pub fn is_for_refund(&$self) -> bool {
+		$contents.is_for_refund()
+	}
+
+	/// Whether the invoice was created in response to an [`InvoiceRequest`] created from an
+	/// [`Offer`].
+	///
+	/// [`Offer`]: crate::offers::offer::Offer
+	pub fn is_for_offer(&$self) -> bool {
+		$contents.is_for_offer()
+	}
+
 	/// The chains that may be used when paying a requested invoice.
 	///
 	/// From [`Offer::chains`]; `None` if the invoice was created in response to a [`Refund`].
@@ -1093,6 +1106,20 @@ impl InvoiceContents {
 		}
 	}
 
+	fn is_for_refund(&self) -> bool {
+		match self {
+			InvoiceContents::ForRefund { .. } => true,
+			InvoiceContents::ForOffer { .. } => false,
+		}
+	}
+
+	fn is_for_offer(&self) -> bool {
+		match self {
+			InvoiceContents::ForRefund { .. } => false,
+			InvoiceContents::ForOffer { .. } => true,
+		}
+	}
+
 	fn offer_chains(&self) -> Option<Vec<ChainHash>> {
 		match self {
 			InvoiceContents::ForOffer { invoice_request, .. } => {
