Fail request_refund_payment for unsupported chain

lightning/src/ln/channelmanager.rs

@@ -7830,6 +7830,7 @@ where
 	/// Errors if:
 	/// - a duplicate `payment_id` is provided given the caveats in the aforementioned link,
 	/// - the provided parameters are invalid for the offer,
+	/// - the offer is for an unsupported chain, or
 	/// - the parameterized [`Router`] is unable to create a blinded reply path for the invoice
 	///   request.
 	///
@@ -7918,8 +7919,10 @@ where
 	///
 	/// # Errors
 	///
-	/// Errors if the parameterized [`Router`] is unable to create a blinded payment path or reply
-	/// path for the invoice.
+	/// Errors if:
+	/// - the refund is for an unsupported chain, or
+	/// - the parameterized [`Router`] is unable to create a blinded payment path or reply path for
+	///   the invoice.
 	///
 	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 	pub fn request_refund_payment(&self, refund: &Refund) -> Result<(), Bolt12SemanticError> {
@@ -7930,6 +7933,10 @@ where
 		let amount_msats = refund.amount_msats();
 		let relative_expiry = DEFAULT_RELATIVE_EXPIRY.as_secs() as u32;
 
+		if refund.chain() != self.chain_hash {
+			return Err(Bolt12SemanticError::UnsupportedChain);
+		}
+
 		match self.create_inbound_payment(Some(amount_msats), relative_expiry, None) {
 			Ok((payment_hash, payment_secret)) => {
 				let payment_paths = self.create_blinded_payment_paths(amount_msats, payment_secret)

lightning/src/ln/offers_tests.rs

@@ -40,6 +40,7 @@
 //! Nodes without channels are disconnected and connected as needed to ensure that deterministic
 //! blinded paths are used.
 
+use bitcoin::network::constants::Network;
 use core::time::Duration;
 use crate::blinded_path::BlindedPath;
 use crate::events::{Event, MessageSendEventsProvider, PaymentPurpose};
@@ -732,6 +733,61 @@ fn fails_creating_refund_without_blinded_paths() {
 	assert!(nodes[0].node.list_recent_payments().is_empty());
 }
 
+/// Fails creating an invoice request when the offer contains an unsupported chain.
+#[test]
+fn fails_creating_invoice_request_for_unsupported_chain() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 1_000_000_000);
+
+	let alice = &nodes[0];
+	let bob = &nodes[1];
+
+	let offer = alice.node
+		.create_offer_builder("coffee".to_string()).unwrap()
+		.clear_chains()
+		.chain(Network::Signet)
+		.build().unwrap();
+
+	let payment_id = PaymentId([1; 32]);
+	match bob.node.pay_for_offer(&offer, None, None, None, payment_id, Retry::Attempts(0), None) {
+		Ok(_) => panic!("Expected error"),
+		Err(e) => assert_eq!(e, Bolt12SemanticError::UnsupportedChain),
+	}
+}
+
+/// Fails requesting a payment when the refund contains an unsupported chain.
+#[test]
+fn fails_sending_invoice_with_unsupported_chain_for_refund() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 10_000_000, 1_000_000_000);
+
+	let alice = &nodes[0];
+	let bob = &nodes[1];
+
+	let absolute_expiry = Duration::from_secs(u64::MAX);
+	let payment_id = PaymentId([1; 32]);
+	let refund = bob.node
+		.create_refund_builder(
+			"refund".to_string(), 10_000_000, absolute_expiry, payment_id, Retry::Attempts(0), None
+		)
+		.unwrap()
+		.chain(Network::Signet)
+		.build().unwrap();
+
+	match alice.node.request_refund_payment(&refund) {
+		Ok(_) => panic!("Expected error"),
+		Err(e) => assert_eq!(e, Bolt12SemanticError::UnsupportedChain),
+	}
+}
+
 /// Fails creating an invoice request when a blinded reply path cannot be created without exposing
 /// the node's id.
 #[test]

lightning/src/offers/offer.rs

@@ -390,6 +390,12 @@ macro_rules! offer_builder_test_methods { (
 		$return_value
 	}
 
+	#[cfg_attr(c_bindings, allow(dead_code))]
+	pub(crate) fn clear_chains($($self_mut)* $self: $self_type) -> $return_type {
+		$self.offer.chains = None;
+		$return_value
+	}
+
 	#[cfg_attr(c_bindings, allow(dead_code))]
 	pub(crate) fn clear_paths($($self_mut)* $self: $self_type) -> $return_type {
 		$self.offer.paths = None;