Add InvoiceRequestTlvStream::paths

Instead of reusing OfferTlvStream::paths, add a dedicated paths TLV to
InvoiceRequestTlvStream such that it can be used in Refund. This allows
for an Offer without a signing_pubkey and still be able to differentiate
whether an invoice is for an offer or a refund.

Author: jkczyz

lightning/src/offers/invoice.rs

@@ -1632,6 +1632,7 @@ mod tests {
 					quantity: None,
 					payer_id: Some(&payer_pubkey()),
 					payer_note: None,
+					paths: None,
 				},
 				InvoiceTlvStreamRef {
 					paths: Some(Iterable(payment_paths.iter().map(|(_, path)| path))),
@@ -1724,6 +1725,7 @@ mod tests {
 					quantity: None,
 					payer_id: Some(&payer_pubkey()),
 					payer_note: None,
+					paths: None,
 				},
 				InvoiceTlvStreamRef {
 					paths: Some(Iterable(payment_paths.iter().map(|(_, path)| path))),

lightning/src/offers/invoice_request.rs

@@ -971,6 +971,7 @@ impl InvoiceRequestContentsWithoutPayerId {
 			quantity: self.quantity,
 			payer_id: None,
 			payer_note: self.payer_note.as_ref(),
+			paths: None,
 		};
 
 		(payer, offer, invoice_request)
@@ -1003,13 +1004,17 @@ pub(super) const INVOICE_REQUEST_TYPES: core::ops::Range<u64> = 80..160;
 /// [`Refund::payer_id`]: crate::offers::refund::Refund::payer_id
 pub(super) const INVOICE_REQUEST_PAYER_ID_TYPE: u64 = 88;
 
+// This TLV stream is used for both InvoiceRequest and Refund, but not all TLV records are valid for
+// InvoiceRequest as noted below.
 tlv_stream!(InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef, INVOICE_REQUEST_TYPES, {
 	(80, chain: ChainHash),
 	(82, amount: (u64, HighZeroBytesDroppedBigSize)),
 	(84, features: (InvoiceRequestFeatures, WithoutLength)),
 	(86, quantity: (u64, HighZeroBytesDroppedBigSize)),
 	(INVOICE_REQUEST_PAYER_ID_TYPE, payer_id: PublicKey),
 	(89, payer_note: (String, WithoutLength)),
+	// Only used for Refund since the onion message of an InvoiceRequest has a reply path.
+	(90, paths: (Vec<BlindedPath>, WithoutLength)),
 });
 
 type FullInvoiceRequestTlvStream =
@@ -1092,7 +1097,9 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 		let (
 			PayerTlvStream { metadata },
 			offer_tlv_stream,
-			InvoiceRequestTlvStream { chain, amount, features, quantity, payer_id, payer_note },
+			InvoiceRequestTlvStream {
+				chain, amount, features, quantity, payer_id, payer_note, paths,
+			},
 		) = tlv_stream;
 
 		let payer = match metadata {
@@ -1119,6 +1126,10 @@ impl TryFrom<PartialInvoiceRequestTlvStream> for InvoiceRequestContents {
 			Some(payer_id) => payer_id,
 		};
 
+		if paths.is_some() {
+			return Err(Bolt12SemanticError::UnexpectedPaths);
+		}
+
 		Ok(InvoiceRequestContents {
 			inner: InvoiceRequestContentsWithoutPayerId {
 				payer, offer, chain, amount_msats: amount, features, quantity, payer_note,
@@ -1310,6 +1321,7 @@ mod tests {
 					quantity: None,
 					payer_id: Some(&payer_pubkey()),
 					payer_note: None,
+					paths: None,
 				},
 				SignatureTlvStreamRef { signature: Some(&invoice_request.signature()) },
 			),

lightning/src/offers/parse.rs

@@ -183,6 +183,8 @@ pub enum Bolt12SemanticError {
 	DuplicatePaymentId,
 	/// Blinded paths were expected but were missing.
 	MissingPaths,
+	/// Blinded paths were provided but were not expected.
+	UnexpectedPaths,
 	/// The blinded payinfo given does not match the number of blinded path hops.
 	InvalidPayInfo,
 	/// An invoice creation time was expected but was missing.

lightning/src/offers/refund.rs

@@ -170,8 +170,8 @@ macro_rules! refund_explicit_metadata_builder_methods { () => {
 		Ok(Self {
 			refund: RefundContents {
 				payer: PayerContents(metadata), description, absolute_expiry: None, issuer: None,
-				paths: None, chain: None, amount_msats, features: InvoiceRequestFeatures::empty(),
-				quantity: None, payer_id, payer_note: None,
+				chain: None, amount_msats, features: InvoiceRequestFeatures::empty(),
+				quantity: None, payer_id, payer_note: None, paths: None,
 			},
 			secp_ctx: None,
 		})
@@ -209,8 +209,8 @@ macro_rules! refund_builder_methods { (
 		Ok(Self {
 			refund: RefundContents {
 				payer: PayerContents(metadata), description, absolute_expiry: None, issuer: None,
-				paths: None, chain: None, amount_msats, features: InvoiceRequestFeatures::empty(),
-				quantity: None, payer_id: node_id, payer_note: None,
+				chain: None, amount_msats, features: InvoiceRequestFeatures::empty(),
+				quantity: None, payer_id: node_id, payer_note: None, paths: None,
 			},
 			secp_ctx: Some(secp_ctx),
 		})
@@ -410,14 +410,14 @@ pub(super) struct RefundContents {
 	description: String,
 	absolute_expiry: Option<Duration>,
 	issuer: Option<String>,
-	paths: Option<Vec<BlindedPath>>,
 	// invoice_request fields
 	chain: Option<ChainHash>,
 	amount_msats: u64,
 	features: InvoiceRequestFeatures,
 	quantity: Option<u64>,
 	payer_id: PublicKey,
 	payer_note: Option<String>,
+	paths: Option<Vec<BlindedPath>>,
 }
 
 impl Refund {
@@ -734,7 +734,7 @@ impl RefundContents {
 			description: Some(&self.description),
 			features: None,
 			absolute_expiry: self.absolute_expiry.map(|duration| duration.as_secs()),
-			paths: self.paths.as_ref(),
+			paths: None,
 			issuer: self.issuer.as_ref(),
 			quantity_max: None,
 			node_id: None,
@@ -752,6 +752,7 @@ impl RefundContents {
 			quantity: self.quantity,
 			payer_id: Some(&self.payer_id),
 			payer_note: self.payer_note.as_ref(),
+			paths: self.paths.as_ref(),
 		};
 
 		(payer, offer, invoice_request)
@@ -820,9 +821,12 @@ impl TryFrom<RefundTlvStream> for RefundContents {
 			PayerTlvStream { metadata: payer_metadata },
 			OfferTlvStream {
 				chains, metadata, currency, amount: offer_amount, description,
-				features: offer_features, absolute_expiry, paths, issuer, quantity_max, node_id,
+				features: offer_features, absolute_expiry, paths: offer_paths, issuer, quantity_max,
+				node_id,
+			},
+			InvoiceRequestTlvStream {
+				chain, amount, features, quantity, payer_id, payer_note, paths
 			},
-			InvoiceRequestTlvStream { chain, amount, features, quantity, payer_id, payer_note },
 		) = tlv_stream;
 
 		let payer = match payer_metadata {
@@ -853,6 +857,10 @@ impl TryFrom<RefundTlvStream> for RefundContents {
 
 		let absolute_expiry = absolute_expiry.map(Duration::from_secs);
 
+		if offer_paths.is_some() {
+			return Err(Bolt12SemanticError::UnexpectedPaths);
+		}
+
 		if quantity_max.is_some() {
 			return Err(Bolt12SemanticError::UnexpectedQuantity);
 		}
@@ -877,8 +885,8 @@ impl TryFrom<RefundTlvStream> for RefundContents {
 		};
 
 		Ok(RefundContents {
-			payer, description, absolute_expiry, issuer, paths, chain, amount_msats, features,
-			quantity, payer_id, payer_note,
+			payer, description, absolute_expiry, issuer, chain, amount_msats, features, quantity,
+			payer_id, payer_note, paths,
 		})
 	}
 }
@@ -980,6 +988,7 @@ mod tests {
 					quantity: None,
 					payer_id: Some(&payer_pubkey()),
 					payer_note: None,
+					paths: None,
 				},
 			),
 		);
@@ -1173,12 +1182,12 @@ mod tests {
 			.path(paths[1].clone())
 			.build()
 			.unwrap();
-		let (_, offer_tlv_stream, invoice_request_tlv_stream) = refund.as_tlv_stream();
-		assert_eq!(refund.paths(), paths.as_slice());
+		let (_, _, invoice_request_tlv_stream) = refund.as_tlv_stream();
 		assert_eq!(refund.payer_id(), pubkey(42));
+		assert_eq!(refund.paths(), paths.as_slice());
 		assert_ne!(pubkey(42), pubkey(44));
-		assert_eq!(offer_tlv_stream.paths, Some(&paths));
 		assert_eq!(invoice_request_tlv_stream.payer_id, Some(&pubkey(42)));
+		assert_eq!(invoice_request_tlv_stream.paths, Some(&paths));
 	}
 
 	#[test]