Add UserConfig::manually_handle_bolt12_invoices

BOLT12 invoices are automatically paid once they have been verified.
Users may want to manually pay them by first performing additional
checks. Add a manually_handle_bolt12_invoices configuration option that
when set generates an Event::InvoiceReceived instead of paying the
invoice.

Author: jkczyz

lightning/src/ln/channelmanager.rs

@@ -10443,21 +10443,25 @@ where
 				}
 			},
 			OffersMessage::Invoice(invoice) => {
-				let result = invoice
-					.verify(expanded_key, secp_ctx)
-					.map_err(|()| InvoiceError::from_string("Unrecognized invoice".to_owned()))
-					.and_then(|payment_id| {
+				let result = match invoice.verify(expanded_key, secp_ctx) {
+					Ok(payment_id) => {
 						let features = self.bolt12_invoice_features();
 						if invoice.invoice_features().requires_unknown_bits_from(&features) {
 							Err(InvoiceError::from(Bolt12SemanticError::UnknownRequiredFeatures))
+						} else if self.default_configuration.manually_handle_bolt12_invoices {
+							let event = Event::InvoiceReceived { payment_id, invoice, responder };
+							self.pending_events.lock().unwrap().push_back((event, None));
+							return ResponseInstruction::NoResponse;
 						} else {
 							self.send_payment_for_bolt12_invoice(&invoice, payment_id)
 								.map_err(|e| {
 									log_trace!(self.logger, "Failed paying invoice: {:?}", e);
 									InvoiceError::from_string(format!("{:?}", e))
 								})
 						}
-					});
+					},
+					Err(()) => Err(InvoiceError::from_string("Unrecognized invoice".to_owned())),
+				};
 
 				match result {
 					Ok(()) => ResponseInstruction::NoResponse,

lightning/src/util/config.rs

@@ -847,6 +847,16 @@ pub struct UserConfig {
 	///
 	/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 	pub accept_mpp_keysend: bool,
+	/// If this is set to true, the user needs to manually pay [`Bolt12Invoice`]s when received.
+	///
+	/// When set to true, [`Event::InvoiceReceived`] will be generated for each received
+	/// [`Bolt12Invoice`] instead of being automatically paid after verification.
+	///
+	/// Default value: false.
+	///
+	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+	/// [`Event::InvoiceReceived`]: crate::events::Event::InvoiceReceived
+	pub manually_handle_bolt12_invoices: bool,
 }
 
 impl Default for UserConfig {
@@ -860,6 +870,7 @@ impl Default for UserConfig {
 			manually_accept_inbound_channels: false,
 			accept_intercept_htlcs: false,
 			accept_mpp_keysend: false,
+			manually_handle_bolt12_invoices: false,
 		}
 	}
 }
@@ -879,6 +890,7 @@ impl Readable for UserConfig {
 			manually_accept_inbound_channels: Readable::read(reader)?,
 			accept_intercept_htlcs: Readable::read(reader)?,
 			accept_mpp_keysend: Readable::read(reader)?,
+			manually_handle_bolt12_invoices: Readable::read(reader)?,
 		})
 	}
 }