Return ExpandedKey from NodeSigner

NodeSinger::get_inbound_payment_key_material returns KeyMaterial, which
is used for constructing an ExpandedKey. Change the trait to return an
ExpandedKey directly instead. This allows for direct access to the
ExpandedKey when a NodeSigner referenced is available. Otherwise, it
would either need to be reconstructed or passed in separately.

Author: jkczyz

fuzz/src/chanmon_consistency.rs

@@ -51,6 +51,7 @@ use lightning::ln::channelmanager::{
 	RecipientOnionFields,
 };
 use lightning::ln::functional_test_utils::*;
+use lightning::ln::inbound_payment::ExpandedKey;
 use lightning::ln::msgs::{
 	self, ChannelMessageHandler, CommitmentUpdate, DecodeError, Init, UpdateAddHTLC,
 };
@@ -327,10 +328,10 @@ impl NodeSigner for KeyProvider {
 		Ok(SharedSecret::new(other_key, &node_secret))
 	}
 
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
 		#[rustfmt::skip]
 		let random_bytes = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, self.node_secret[31]];
-		KeyMaterial(random_bytes)
+		ExpandedKey::new(&KeyMaterial(random_bytes))
 	}
 
 	fn sign_invoice(

fuzz/src/full_stack.rs

@@ -43,6 +43,7 @@ use lightning::ln::channelmanager::{
 	ChainParameters, ChannelManager, InterceptId, PaymentId, RecipientOnionFields, Retry,
 };
 use lightning::ln::functional_test_utils::*;
+use lightning::ln::inbound_payment::ExpandedKey;
 use lightning::ln::msgs::{self, DecodeError};
 use lightning::ln::peer_handler::{
 	IgnoringMessageHandler, MessageHandler, PeerManager, SocketDescriptor,
@@ -79,7 +80,6 @@ use bitcoin::secp256k1::{self, Message, PublicKey, Scalar, Secp256k1, SecretKey}
 
 use std::cell::RefCell;
 use std::cmp;
-use std::convert::TryInto;
 use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
 
@@ -364,7 +364,7 @@ impl<'a> Drop for MoneyLossDetector<'a> {
 
 struct KeyProvider {
 	node_secret: SecretKey,
-	inbound_payment_key: KeyMaterial,
+	inbound_payment_key: ExpandedKey,
 	counter: AtomicU64,
 	signer_state: RefCell<HashMap<u8, (bool, Arc<Mutex<EnforcementState>>)>>,
 }
@@ -402,8 +402,8 @@ impl NodeSigner for KeyProvider {
 		Ok(SharedSecret::new(other_key, &node_secret))
 	}
 
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial {
-		self.inbound_payment_key.clone()
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
+		self.inbound_payment_key
 	}
 
 	fn sign_invoice(
@@ -636,7 +636,7 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger>) {
 
 	let keys_manager = Arc::new(KeyProvider {
 		node_secret: our_network_key.clone(),
-		inbound_payment_key: KeyMaterial(inbound_payment_key.try_into().unwrap()),
+		inbound_payment_key: ExpandedKey::new(&KeyMaterial(inbound_payment_key)),
 		counter: AtomicU64::new(0),
 		signer_state: RefCell::new(new_hash_map()),
 	});

fuzz/src/onion_message.rs

@@ -9,6 +9,7 @@ use lightning::blinded_path::message::{
 	AsyncPaymentsContext, BlindedMessagePath, MessageContext, OffersContext,
 };
 use lightning::blinded_path::EmptyNodeIdLookUp;
+use lightning::ln::inbound_payment::ExpandedKey;
 use lightning::ln::msgs::{self, DecodeError, OnionMessageHandler};
 use lightning::ln::peer_handler::IgnoringMessageHandler;
 use lightning::ln::script::ShutdownScript;
@@ -22,7 +23,7 @@ use lightning::onion_message::messenger::{
 };
 use lightning::onion_message::offers::{OffersMessage, OffersMessageHandler};
 use lightning::onion_message::packet::OnionMessageContents;
-use lightning::sign::{EntropySource, KeyMaterial, NodeSigner, Recipient, SignerProvider};
+use lightning::sign::{EntropySource, NodeSigner, Recipient, SignerProvider};
 use lightning::types::features::InitFeatures;
 use lightning::util::logger::Logger;
 use lightning::util::ser::{Readable, Writeable, Writer};
@@ -223,7 +224,7 @@ impl NodeSigner for KeyProvider {
 		Ok(SharedSecret::new(other_key, &node_secret))
 	}
 
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
 		unreachable!()
 	}
 

lightning/src/ln/blinded_payment_tests.rs

@@ -33,7 +33,7 @@ use crate::offers::invoice::UnsignedBolt12Invoice;
 use crate::offers::nonce::Nonce;
 use crate::prelude::*;
 use crate::routing::router::{BlindedTail, Path, Payee, PaymentParameters, RouteHop, RouteParameters};
-use crate::sign::{KeyMaterial, NodeSigner, Recipient};
+use crate::sign::{NodeSigner, Recipient};
 use crate::util::config::UserConfig;
 use crate::util::ser::WithoutLength;
 use crate::util::test_utils;
@@ -98,7 +98,7 @@ fn hmac_payee_tlvs(
 	payee_tlvs: &ReceiveTlvs, keys_manager: &test_utils::TestKeysInterface,
 ) -> (Hmac<Sha256>, Nonce) {
 	let nonce = Nonce([42u8; 16]);
-	let expanded_key = ExpandedKey::new(&keys_manager.get_inbound_payment_key_material());
+	let expanded_key = keys_manager.get_inbound_payment_key();
 	let hmac = payee_tlvs.hmac_for_offer_payment(nonce, &expanded_key);
 	(hmac, nonce)
 }
@@ -1244,9 +1244,7 @@ fn blinded_keysend() {
 	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1_000_000, 0);
 	let chan_upd_1_2 = create_announced_chan_between_nodes_with_value(&nodes, 1, 2, 1_000_000, 0).0.contents;
 
-	let inbound_payment_key = inbound_payment::ExpandedKey::new(
-		&nodes[2].keys_manager.get_inbound_payment_key_material()
-	);
+	let inbound_payment_key = nodes[2].keys_manager.get_inbound_payment_key();
 	let payment_secret = inbound_payment::create_for_spontaneous_payment(
 		&inbound_payment_key, None, u32::MAX, nodes[2].node.duration_since_epoch().as_secs(), None
 	).unwrap();
@@ -1287,9 +1285,7 @@ fn blinded_mpp_keysend() {
 	let chan_1_3 = create_announced_chan_between_nodes(&nodes, 1, 3);
 	let chan_2_3 = create_announced_chan_between_nodes(&nodes, 2, 3);
 
-	let inbound_payment_key = inbound_payment::ExpandedKey::new(
-		&nodes[3].keys_manager.get_inbound_payment_key_material()
-	);
+	let inbound_payment_key = nodes[3].keys_manager.get_inbound_payment_key();
 	let payment_secret = inbound_payment::create_for_spontaneous_payment(
 		&inbound_payment_key, None, u32::MAX, nodes[3].node.duration_since_epoch().as_secs(), None
 	).unwrap();
@@ -1557,7 +1553,7 @@ fn route_blinding_spec_test_vector() {
 			}
 			Ok(SharedSecret::new(other_key, &node_secret))
 		}
-		fn get_inbound_payment_key_material(&self) -> KeyMaterial { unreachable!() }
+		fn get_inbound_payment_key(&self) -> ExpandedKey { unreachable!() }
 		fn get_node_id(&self, _recipient: Recipient) -> Result<PublicKey, ()> { unreachable!() }
 		fn sign_invoice(
 			&self, _invoice: &RawBolt11Invoice, _recipient: Recipient,

lightning/src/ln/channelmanager.rs

@@ -230,7 +230,7 @@ pub enum PendingHTLCRouting {
 		requires_blinded_error: bool,
 		/// Set if we are receiving a keysend to a blinded path, meaning we created the
 		/// [`PaymentSecret`] and should verify it using our
-		/// [`NodeSigner::get_inbound_payment_key_material`].
+		/// [`NodeSigner::get_inbound_payment_key`].
 		has_recipient_created_payment_secret: bool,
 	},
 }
@@ -3418,8 +3418,7 @@ where
 	) -> Self {
 		let mut secp_ctx = Secp256k1::new();
 		secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
-		let inbound_pmt_key_material = node_signer.get_inbound_payment_key_material();
-		let expanded_inbound_key = inbound_payment::ExpandedKey::new(&inbound_pmt_key_material);
+		let expanded_inbound_key = node_signer.get_inbound_payment_key();
 		ChannelManager {
 			default_configuration: config.clone(),
 			chain_hash: ChainHash::using_genesis_block(params.network),
@@ -13858,8 +13857,7 @@ where
 			}, None));
 		}
 
-		let inbound_pmt_key_material = args.node_signer.get_inbound_payment_key_material();
-		let expanded_inbound_key = inbound_payment::ExpandedKey::new(&inbound_pmt_key_material);
+		let expanded_inbound_key = args.node_signer.get_inbound_payment_key();
 
 		let mut claimable_payments = hash_map_with_capacity(claimable_htlcs_list.len());
 		if let Some(purposes) = claimable_htlc_purposes {

lightning/src/ln/inbound_payment.rs

@@ -37,10 +37,10 @@ const AMT_MSAT_LEN: usize = 8;
 // retrieve said payment type bits.
 const METHOD_TYPE_OFFSET: usize = 5;
 
-/// A set of keys that were HKDF-expanded from an initial call to
-/// [`NodeSigner::get_inbound_payment_key_material`].
+/// A set of keys that were HKDF-expanded. Returned by [`NodeSigner::get_inbound_payment_key`].
 ///
-/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
+/// [`NodeSigner::get_inbound_payment_key`]: crate::sign::NodeSigner::get_inbound_payment_key
+#[derive(Hash, Copy, Clone, PartialEq, Eq, Debug)]
 pub struct ExpandedKey {
 	/// The key used to encrypt the bytes containing the payment metadata (i.e. the amount and
 	/// expiry, included for payment verification on decryption).
@@ -129,7 +129,7 @@ fn min_final_cltv_expiry_delta_from_metadata(bytes: [u8; METADATA_LEN]) -> u16 {
 /// `ChannelManager` is required. Useful for generating invoices for [phantom node payments] without
 /// a `ChannelManager`.
 ///
-/// `keys` is generated by calling [`NodeSigner::get_inbound_payment_key_material`] and then
+/// `keys` is generated by calling [`NodeSigner::get_inbound_payment_key`] and then
 /// calling [`ExpandedKey::new`] with its result. It is recommended to cache this value and not
 /// regenerate it for each new inbound payment.
 ///
@@ -139,7 +139,7 @@ fn min_final_cltv_expiry_delta_from_metadata(bytes: [u8; METADATA_LEN]) -> u16 {
 /// on versions of LDK prior to 0.0.114.
 ///
 /// [phantom node payments]: crate::sign::PhantomKeysManager
-/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
+/// [`NodeSigner::get_inbound_payment_key`]: crate::sign::NodeSigner::get_inbound_payment_key
 pub fn create<ES: Deref>(keys: &ExpandedKey, min_value_msat: Option<u64>,
 	invoice_expiry_delta_secs: u32, entropy_source: &ES, current_time: u64,
 	min_final_cltv_expiry_delta: Option<u16>) -> Result<(PaymentHash, PaymentSecret), ()>
@@ -281,7 +281,7 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD
 /// For payments including a custom `min_final_cltv_expiry_delta`, the metadata is constructed as:
 ///   payment method (3 bits) || payment amount (8 bytes - 3 bits) || min_final_cltv_expiry_delta (2 bytes) || expiry (6 bytes)
 ///
-/// In both cases the result is then encrypted using a key derived from [`NodeSigner::get_inbound_payment_key_material`].
+/// In both cases the result is then encrypted using a key derived from [`NodeSigner::get_inbound_payment_key`].
 ///
 /// Then on payment receipt, we verify in this method that the payment preimage and payment secret
 /// match what was constructed.
@@ -302,7 +302,7 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD
 ///
 /// See [`ExpandedKey`] docs for more info on the individual keys used.
 ///
-/// [`NodeSigner::get_inbound_payment_key_material`]: crate::sign::NodeSigner::get_inbound_payment_key_material
+/// [`NodeSigner::get_inbound_payment_key`]: crate::sign::NodeSigner::get_inbound_payment_key
 /// [`create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
 /// [`create_inbound_payment_for_hash`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
 pub(super) fn verify<L: Deref>(payment_hash: PaymentHash, payment_data: &msgs::FinalOnionHopData,

lightning/src/ln/invoice_utils.rs

@@ -12,7 +12,7 @@ use crate::sign::{Recipient, NodeSigner, SignerProvider, EntropySource};
 use crate::types::payment::PaymentHash;
 use crate::ln::channel_state::ChannelDetails;
 use crate::ln::channelmanager::{Bolt11InvoiceParameters, ChannelManager, PhantomRouteHints, MIN_CLTV_EXPIRY_DELTA, MIN_FINAL_CLTV_EXPIRY_DELTA};
-use crate::ln::inbound_payment::{create, create_from_hash, ExpandedKey};
+use crate::ln::inbound_payment::{create, create_from_hash};
 use crate::routing::gossip::RoutingFees;
 use crate::routing::router::{RouteHint, RouteHintHop, Router};
 use crate::onion_message::messenger::MessageRouter;
@@ -165,8 +165,7 @@ where
 		Bolt11InvoiceDescription::Hash(hash) => InvoiceBuilder::new(network).description_hash(hash.0),
 	};
 
-	// If we ever see performance here being too slow then we should probably take this ExpandedKey as a parameter instead.
-	let keys = ExpandedKey::new(&node_signer.get_inbound_payment_key_material());
+	let keys = node_signer.get_inbound_payment_key();
 	let (payment_hash, payment_secret) = if let Some(payment_hash) = payment_hash {
 		let payment_secret = create_from_hash(
 			&keys,

lightning/src/ln/max_payment_path_len_tests.rs

@@ -19,7 +19,6 @@ use crate::ln::blinded_payment_tests::get_blinded_route_parameters;
 use crate::ln::channelmanager::{PaymentId, Verification};
 use crate::types::features::BlindedHopFeatures;
 use crate::ln::functional_test_utils::*;
-use crate::ln::inbound_payment::ExpandedKey;
 use crate::ln::msgs;
 use crate::ln::msgs::OnionMessageHandler;
 use crate::ln::onion_utils;
@@ -170,7 +169,7 @@ fn one_hop_blinded_path_with_custom_tlv() {
 		authentication: None,
 	};
 	let nonce = Nonce([42u8; 16]);
-	let expanded_key = ExpandedKey::new(&chanmon_cfgs[2].keys_manager.get_inbound_payment_key_material());
+	let expanded_key = chanmon_cfgs[2].keys_manager.get_inbound_payment_key();
 	let hmac = payee_tlvs.hmac_for_offer_payment(nonce, &expanded_key);
 	payee_tlvs.authentication = Some((hmac, nonce));
 	let mut secp_ctx = Secp256k1::new();

lightning/src/ln/offers_tests.rs

@@ -51,7 +51,6 @@ use crate::events::{ClosureReason, Event, MessageSendEventsProvider, PaymentFail
 use crate::ln::channelmanager::{Bolt12PaymentError, MAX_SHORT_LIVED_RELATIVE_EXPIRY, PaymentId, RecentPaymentDetails, Retry, self};
 use crate::types::features::Bolt12InvoiceFeatures;
 use crate::ln::functional_test_utils::*;
-use crate::ln::inbound_payment::ExpandedKey;
 use crate::ln::msgs::{ChannelMessageHandler, Init, NodeAnnouncement, OnionMessage, OnionMessageHandler, RoutingMessageHandler, SocketAddress, UnsignedGossipMessage, UnsignedNodeAnnouncement};
 use crate::ln::outbound_payment::IDEMPOTENCY_TIMEOUT_TICKS;
 use crate::offers::invoice::Bolt12Invoice;
@@ -2218,7 +2217,7 @@ fn fails_paying_invoice_with_unknown_required_features() {
 	let payment_paths = invoice.payment_paths().to_vec();
 	let payment_hash = invoice.payment_hash();
 
-	let expanded_key = ExpandedKey::new(&alice.keys_manager.get_inbound_payment_key_material());
+	let expanded_key = alice.keys_manager.get_inbound_payment_key();
 	let secp_ctx = Secp256k1::new();
 
 	let created_at = alice.node.duration_since_epoch();

lightning/src/sign/mod.rs

@@ -51,6 +51,7 @@ use crate::ln::channel_keys::{
 	add_public_key_tweak, DelayedPaymentBasepoint, DelayedPaymentKey, HtlcBasepoint, HtlcKey,
 	RevocationBasepoint, RevocationKey,
 };
+use crate::ln::inbound_payment::ExpandedKey;
 #[cfg(taproot)]
 use crate::ln::msgs::PartialSignatureWithNonce;
 use crate::ln::msgs::{UnsignedChannelAnnouncement, UnsignedGossipMessage};
@@ -820,7 +821,7 @@ pub trait EntropySource {
 
 /// A trait that can handle cryptographic operations at the scope level of a node.
 pub trait NodeSigner {
-	/// Get secret key material as bytes for use in encrypting and decrypting inbound payment data.
+	/// Get the [`ExpandedKey`] for use in encrypting and decrypting inbound payment data.
 	///
 	/// If the implementor of this trait supports [phantom node payments], then every node that is
 	/// intended to be included in the phantom invoice route hints must return the same value from
@@ -832,7 +833,7 @@ pub trait NodeSigner {
 	/// This method must return the same value each time it is called.
 	///
 	/// [phantom node payments]: PhantomKeysManager
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial;
+	fn get_inbound_payment_key(&self) -> ExpandedKey;
 
 	/// Get node id based on the provided [`Recipient`].
 	///
@@ -1852,7 +1853,7 @@ pub struct KeysManager {
 	secp_ctx: Secp256k1<secp256k1::All>,
 	node_secret: SecretKey,
 	node_id: PublicKey,
-	inbound_payment_key: KeyMaterial,
+	inbound_payment_key: ExpandedKey,
 	destination_script: ScriptBuf,
 	shutdown_pubkey: PublicKey,
 	channel_master_key: Xpriv,
@@ -1938,7 +1939,7 @@ impl KeysManager {
 					secp_ctx,
 					node_secret,
 					node_id,
-					inbound_payment_key: KeyMaterial(inbound_pmt_key_bytes),
+					inbound_payment_key: ExpandedKey::new(&KeyMaterial(inbound_pmt_key_bytes)),
 
 					destination_script,
 					shutdown_pubkey,
@@ -2175,7 +2176,7 @@ impl NodeSigner for KeysManager {
 		Ok(SharedSecret::new(other_key, &node_secret))
 	}
 
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
 		self.inbound_payment_key.clone()
 	}
 
@@ -2312,7 +2313,7 @@ pub struct PhantomKeysManager {
 	pub(crate) inner: KeysManager,
 	#[cfg(not(test))]
 	inner: KeysManager,
-	inbound_payment_key: KeyMaterial,
+	inbound_payment_key: ExpandedKey,
 	phantom_secret: SecretKey,
 	phantom_node_id: PublicKey,
 }
@@ -2344,7 +2345,7 @@ impl NodeSigner for PhantomKeysManager {
 		Ok(SharedSecret::new(other_key, &node_secret))
 	}
 
-	fn get_inbound_payment_key_material(&self) -> KeyMaterial {
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
 		self.inbound_payment_key.clone()
 	}
 
@@ -2444,7 +2445,7 @@ impl PhantomKeysManager {
 		let phantom_node_id = PublicKey::from_secret_key(&inner.secp_ctx, &phantom_secret);
 		Self {
 			inner,
-			inbound_payment_key: KeyMaterial(inbound_key),
+			inbound_payment_key: ExpandedKey::new(&KeyMaterial(inbound_key)),
 			phantom_secret,
 			phantom_node_id,
 		}

lightning/src/util/test_utils.rs

@@ -30,6 +30,7 @@ use crate::ln::channelmanager;
 #[cfg(test)]
 use crate::ln::chan_utils::CommitmentTransaction;
 use crate::types::features::{ChannelFeatures, InitFeatures, NodeFeatures};
+use crate::ln::inbound_payment::ExpandedKey;
 use crate::ln::{msgs, wire};
 use crate::ln::msgs::LightningError;
 use crate::ln::script::ShutdownScript;
@@ -1188,7 +1189,7 @@ impl TestNodeSigner {
 }
 
 impl NodeSigner for TestNodeSigner {
-	fn get_inbound_payment_key_material(&self) -> crate::sign::KeyMaterial {
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
 		unreachable!()
 	}
 
@@ -1254,8 +1255,8 @@ impl NodeSigner for TestKeysInterface {
 		self.backing.ecdh(recipient, other_key, tweak)
 	}
 
-	fn get_inbound_payment_key_material(&self) -> sign::KeyMaterial {
-		self.backing.get_inbound_payment_key_material()
+	fn get_inbound_payment_key(&self) -> ExpandedKey {
+		self.backing.get_inbound_payment_key()
 	}
 
 	fn sign_invoice(&self, invoice: &RawBolt11Invoice, recipient: Recipient) -> Result<RecoverableSignature, ()> {