Clean up error handling on onion keys construction

Onion keys construction can only fail if we have a key which is
the inverse of a hash containing a public key which we generated
(even indirectly). Because we prefer to panic if our RNG creates an
insecure key (as it indicates operating is incredibly unsafe), we
thus don't actually need to return an error from
`construct_onion_keys_generic_callback`, which we clean up here.

Author: TheBlueMatt

lightning/src/ln/blinded_payment_tests.rs

@@ -384,7 +384,7 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
 				ForwardCheckFail::ForwardPayloadEncodedAsReceive => {
 					let recipient_onion_fields = RecipientOnionFields::spontaneous_empty();
 					let session_priv = SecretKey::from_slice(&[3; 32]).unwrap();
-					let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
+					let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv);
 					let cur_height = nodes[0].best_block_info().1;
 					let (mut onion_payloads, ..) = onion_utils::build_onion_payloads(
 						&route.paths[0], amt_msat, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
@@ -965,7 +965,7 @@ fn do_multi_hop_receiver_fail(check: ReceiveCheckFail) {
 		},
 		ReceiveCheckFail::OnionDecodeFail => {
 			let session_priv = SecretKey::from_slice(&session_priv).unwrap();
-			let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
+			let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv);
 			let cur_height = nodes[0].best_block_info().1;
 			let recipient_onion_fields = RecipientOnionFields::spontaneous_empty();
 			let (mut onion_payloads, ..) = onion_utils::build_onion_payloads(

lightning/src/ln/functional_tests.rs

@@ -1434,7 +1434,7 @@ pub fn test_fee_spike_violation_fails_htlc() {
 
 	let cur_height = nodes[1].node.best_block.read().unwrap().height + 1;
 
-	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv).unwrap();
+	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv);
 	let recipient_onion_fields = RecipientOnionFields::secret_only(payment_secret);
 	let (onion_payloads, htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(&route.paths[0],
 		3460001, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
@@ -1632,7 +1632,7 @@ pub fn test_chan_reserve_violation_inbound_htlc_outbound_channel() {
 	let secp_ctx = Secp256k1::new();
 	let session_priv = SecretKey::from_slice(&[42; 32]).unwrap();
 	let cur_height = nodes[1].node.best_block.read().unwrap().height + 1;
-	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv).unwrap();
+	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv);
 	let recipient_onion_fields = RecipientOnionFields::secret_only(payment_secret);
 	let (onion_payloads, htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(&route.paths[0],
 		700_000, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
@@ -1812,7 +1812,7 @@ pub fn test_chan_reserve_violation_inbound_htlc_inbound_chan() {
 	let secp_ctx = Secp256k1::new();
 	let session_priv = SecretKey::from_slice(&[42; 32]).unwrap();
 	let cur_height = nodes[0].node.best_block.read().unwrap().height + 1;
-	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route_2.paths[0], &session_priv).unwrap();
+	let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route_2.paths[0], &session_priv);
 	let recipient_onion_fields = RecipientOnionFields::spontaneous_empty();
 	let (onion_payloads, htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(
 		&route_2.paths[0], recv_value_2, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
@@ -3864,7 +3864,7 @@ pub fn fail_backward_pending_htlc_upon_channel_failure() {
 		let recipient_onion_fields = RecipientOnionFields::secret_only(payment_secret);
 		let (onion_payloads, _amount_msat, cltv_expiry) = onion_utils::build_onion_payloads(
 			&route.paths[0], 50_000, &recipient_onion_fields, current_height, &None, None, None).unwrap();
-		let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv).unwrap();
+		let onion_keys = onion_utils::construct_onion_keys(&secp_ctx, &route.paths[0], &session_priv);
 		let onion_routing_packet = onion_utils::construct_onion_packet(onion_payloads, onion_keys, [0; 32], &payment_hash).unwrap();
 
 		// Send a 0-msat update_add_htlc to fail the channel.
@@ -6876,7 +6876,7 @@ pub fn test_update_add_htlc_bolt2_receiver_check_max_htlc_limit() {
 	route.paths[0].hops[0].fee_msat = send_amt;
 	let session_priv = SecretKey::from_slice(&[42; 32]).unwrap();
 	let cur_height = nodes[0].node.best_block.read().unwrap().height + 1;
-	let onion_keys = onion_utils::construct_onion_keys(&Secp256k1::signing_only(), &route.paths[0], &session_priv).unwrap();
+	let onion_keys = onion_utils::construct_onion_keys(&Secp256k1::signing_only(), &route.paths[0], &session_priv);
 	let recipient_onion_fields = RecipientOnionFields::secret_only(our_payment_secret);
 	let (onion_payloads, _htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(
 		&route.paths[0], send_amt, &recipient_onion_fields, cur_height, &None, None, None).unwrap();
@@ -8691,7 +8691,7 @@ pub fn test_onion_value_mpp_set_calculation() {
 			let session_priv = [3; 32];
 			let height = nodes[0].best_block_info().1;
 			let session_priv = SecretKey::from_slice(&session_priv).unwrap();
-			let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv).unwrap();
+			let mut onion_keys = onion_utils::construct_onion_keys(&Secp256k1::new(), &route.paths[0], &session_priv);
 			let recipient_onion_fields = RecipientOnionFields::secret_only(our_payment_secret);
 			let (mut onion_payloads, _, _) = onion_utils::build_onion_payloads(&route.paths[0], 100_000,
 				&recipient_onion_fields, height + 1, &None, None, None).unwrap();

lightning/src/ln/onion_payment.rs

@@ -647,7 +647,7 @@ mod tests {
 		recipient_onion.custom_tlvs.push((13377331, vec![0; 1156]));
 
 		let path = Path { hops, blinded_tail: None, };
-		let onion_keys = super::onion_utils::construct_onion_keys(&secp_ctx, &path, &session_priv).unwrap();
+		let onion_keys = super::onion_utils::construct_onion_keys(&secp_ctx, &path, &session_priv);
 		let (onion_payloads, ..) = super::onion_utils::build_onion_payloads(
 			&path, total_amt_msat, &recipient_onion, cur_height + 1, &Some(keysend_preimage), None, None
 		).unwrap();