Disallow user-provided payer_signing_pubkey

When creating an InvoiceRequests, users may choose to either use a
transient signing pubkey generated by LDK or provide a static one.
Disallow the latter as it allows users to reuse the same pubkey, which
results in poor sender privacy.

Author: jkczyz

lightning/src/ln/channelmanager.rs

@@ -9003,7 +9003,7 @@ where
 
 		let nonce = Nonce::from_entropy_source(entropy);
 		let builder: InvoiceRequestBuilder<DerivedPayerSigningPubkey, secp256k1::All> = offer
-			.request_invoice_deriving_signing_pubkey(expanded_key, nonce, secp_ctx, payment_id)?
+			.request_invoice(expanded_key, nonce, secp_ctx, payment_id)?
 			.into();
 		let builder = builder.chain_hash(self.chain_hash)?;
 

lightning/src/ln/outbound_payment.rs

@@ -1952,14 +1952,17 @@ mod tests {
 	use crate::ln::types::PaymentHash;
 	use crate::ln::channelmanager::{PaymentId, RecipientOnionFields};
 	use crate::ln::features::{ChannelFeatures, NodeFeatures};
+	use crate::ln::inbound_payment::ExpandedKey;
 	use crate::ln::msgs::{ErrorAction, LightningError};
 	use crate::ln::outbound_payment::{Bolt12PaymentError, OutboundPayments, Retry, RetryableSendFailure, StaleExpiration};
 	#[cfg(feature = "std")]
 	use crate::offers::invoice::DEFAULT_RELATIVE_EXPIRY;
+	use crate::offers::nonce::Nonce;
 	use crate::offers::offer::OfferBuilder;
 	use crate::offers::test_utils::*;
 	use crate::routing::gossip::NetworkGraph;
 	use crate::routing::router::{InFlightHtlcs, Path, PaymentParameters, Route, RouteHop, RouteParameters};
+	use crate::sign::KeyMaterial;
 	use crate::sync::{Arc, Mutex, RwLock};
 	use crate::util::errors::APIError;
 	use crate::util::test_utils;
@@ -2293,6 +2296,8 @@ mod tests {
 		let router = test_utils::TestRouter::new(network_graph, &logger, &scorer);
 		let secp_ctx = Secp256k1::new();
 		let keys_manager = test_utils::TestKeysInterface::new(&[0; 32], Network::Testnet);
+		let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+		let nonce = Nonce([0; 16]);
 
 		let pending_events = Mutex::new(VecDeque::new());
 		let outbound_payments = OutboundPayments::new();
@@ -2310,9 +2315,8 @@ mod tests {
 		let invoice = OfferBuilder::new(recipient_pubkey())
 			.amount_msats(1000)
 			.build().unwrap()
-			.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
-			.build().unwrap()
-			.sign(payer_sign).unwrap()
+			.request_invoice(&expanded_key, nonce, &secp_ctx, payment_id).unwrap()
+			.build_and_sign().unwrap()
 			.respond_with_no_std(payment_paths(), payment_hash(), created_at).unwrap()
 			.build().unwrap()
 			.sign(recipient_sign).unwrap();
@@ -2349,15 +2353,16 @@ mod tests {
 
 		let pending_events = Mutex::new(VecDeque::new());
 		let outbound_payments = OutboundPayments::new();
+		let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+		let nonce = Nonce([0; 16]);
 		let payment_id = PaymentId([0; 32]);
 		let expiration = StaleExpiration::AbsoluteTimeout(Duration::from_secs(100));
 
 		let invoice = OfferBuilder::new(recipient_pubkey())
 			.amount_msats(1000)
 			.build().unwrap()
-			.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
-			.build().unwrap()
-			.sign(payer_sign).unwrap()
+			.request_invoice(&expanded_key, nonce, &secp_ctx, payment_id).unwrap()
+			.build_and_sign().unwrap()
 			.respond_with_no_std(payment_paths(), payment_hash(), now()).unwrap()
 			.build().unwrap()
 			.sign(recipient_sign).unwrap();
@@ -2410,15 +2415,16 @@ mod tests {
 
 		let pending_events = Mutex::new(VecDeque::new());
 		let outbound_payments = OutboundPayments::new();
+		let expanded_key = ExpandedKey::new(&KeyMaterial([42; 32]));
+		let nonce = Nonce([0; 16]);
 		let payment_id = PaymentId([0; 32]);
 		let expiration = StaleExpiration::AbsoluteTimeout(Duration::from_secs(100));
 
 		let invoice = OfferBuilder::new(recipient_pubkey())
 			.amount_msats(1000)
 			.build().unwrap()
-			.request_invoice(vec![1; 32], payer_pubkey()).unwrap()
-			.build().unwrap()
-			.sign(payer_sign).unwrap()
+			.request_invoice(&expanded_key, nonce, &secp_ctx, payment_id).unwrap()
+			.build_and_sign().unwrap()
 			.respond_with_no_std(payment_paths(), payment_hash(), now()).unwrap()
 			.build().unwrap()
 			.sign(recipient_sign).unwrap();