Support responding to refunds with transient keys

[rust-lightning] / lightning / src / offers / invoice.rs

diff --git a/lightning/src/offers/invoice.rs b/lightning/src/offers/invoice.rs
index 1635d956cbe88d0b55f5726836eae926cac942bf..0cc6c407c1dc0e39a3082adc11251e8881ac11f8 100644 (file)
--- a/lightning/src/offers/invoice.rs
+++ b/lightning/src/offers/invoice.rs
@@ -207,6 +207,22 @@ impl<'a> InvoiceBuilder<'a, DerivedSigningPubkey> {
 
                Self::new(&invoice_request.bytes, contents, Some(keys))
        }
+
+       pub(super) fn for_refund_using_keys(
+               refund: &'a Refund, payment_paths: Vec<(BlindedPath, BlindedPayInfo)>, created_at: Duration,
+               payment_hash: PaymentHash, keys: KeyPair,
+       ) -> Result<Self, SemanticError> {
+               let contents = InvoiceContents::ForRefund {
+                       refund: refund.contents.clone(),
+                       fields: InvoiceFields {
+                               payment_paths, created_at, relative_expiry: None, payment_hash,
+                               amount_msats: refund.amount_msats(), fallbacks: None,
+                               features: Bolt12InvoiceFeatures::empty(), signing_pubkey: keys.public_key(),
+                       },
+               };
+
+               Self::new(&refund.bytes, contents, Some(keys))
+       }
 }
 
 impl<'a, S: SigningPubkeyStrategy> InvoiceBuilder<'a, S> {
@@ -322,12 +338,9 @@ impl<'a> InvoiceBuilder<'a, DerivedSigningPubkey> {
                }
 
                let InvoiceBuilder { invreq_bytes, invoice, keys, .. } = self;
-               let keys = match &invoice {
-                       InvoiceContents::ForOffer { .. } => keys.unwrap(),
-                       InvoiceContents::ForRefund { .. } => unreachable!(),
-               };
-
                let unsigned_invoice = UnsignedInvoice { invreq_bytes, invoice };
+
+               let keys = keys.unwrap();
                let invoice = unsigned_invoice
                        .sign::<_, Infallible>(|digest| Ok(secp_ctx.sign_schnorr_no_aux_rand(digest, &keys)))
                        .unwrap();
@@ -1223,6 +1236,26 @@ mod tests {
                }
        }
 
+       #[test]
+       fn builds_invoice_from_refund_using_derived_keys() {
+               let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+               let entropy = FixedEntropy {};
+               let secp_ctx = Secp256k1::new();
+
+               let refund = RefundBuilder::new("foo".into(), vec![1; 32], payer_pubkey(), 1000).unwrap()
+                       .build().unwrap();
+
+               if let Err(e) = refund
+                       .respond_using_derived_keys_no_std(
+                               payment_paths(), payment_hash(), now(), &expanded_key, &entropy
+                       )
+                       .unwrap()
+                       .build_and_sign(&secp_ctx)
+               {
+                       panic!("error building invoice: {:?}", e);
+               }
+       }
+
        #[test]
        fn builds_invoice_with_relative_expiry() {
                let now = now();