Swap key_derivation_params (u64, u64) for channel_keys_id [u8; 32]

Instead of `key_derivation_params` being a rather strange type, we
call it `channel_keys_id` and give it a generic 32 byte array. This
should be much clearer for users and also more flexible.

Author: TheBlueMatt

fuzz/src/chanmon_consistency.rs

@@ -179,7 +179,7 @@ impl KeysInterface for KeyProvider {
 			SecretKey::from_slice(&[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, 8, self.node_id]).unwrap(),
 			[id, 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, 9, self.node_id],
 			channel_value_satoshis,
-			(0, 0),
+			[0; 32],
 		);
 		let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
 		EnforcingChannelKeys::new_with_revoked(keys, revoked_commitment, false)

fuzz/src/full_stack.rs

@@ -279,7 +279,7 @@ impl KeysInterface for KeyProvider {
 				SecretKey::from_slice(&[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, 5, ctr]).unwrap(),
 				[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, 6, ctr],
 				channel_value_satoshis,
-				(0, 0),
+				[0; 32]
 			)
 		} else {
 			InMemoryChannelKeys::new(
@@ -291,7 +291,7 @@ impl KeysInterface for KeyProvider {
 				SecretKey::from_slice(&[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, 11, ctr]).unwrap(),
 				[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, 12, ctr],
 				channel_value_satoshis,
-				(0, 0),
+				[0; 32]
 			)
 		})
 	}

lightning/src/chain/channelmonitor.rs

@@ -632,7 +632,7 @@ pub struct ChannelMonitor<ChanSigner: ChannelKeys> {
 	counterparty_payment_script: Script,
 	shutdown_script: Script,
 
-	key_derivation_params: (u64, u64),
+	channel_keys_id: [u8; 32],
 	holder_revocation_basepoint: PublicKey,
 	funding_info: (OutPoint, Script),
 	current_counterparty_commitment_txid: Option<Txid>,
@@ -728,7 +728,7 @@ impl<ChanSigner: ChannelKeys> PartialEq for ChannelMonitor<ChanSigner> {
 			self.destination_script != other.destination_script ||
 			self.broadcasted_holder_revokable_script != other.broadcasted_holder_revokable_script ||
 			self.counterparty_payment_script != other.counterparty_payment_script ||
-			self.key_derivation_params != other.key_derivation_params ||
+			self.channel_keys_id != other.channel_keys_id ||
 			self.holder_revocation_basepoint != other.holder_revocation_basepoint ||
 			self.funding_info != other.funding_info ||
 			self.current_counterparty_commitment_txid != other.current_counterparty_commitment_txid ||
@@ -786,7 +786,7 @@ impl<ChanSigner: ChannelKeys> Writeable for ChannelMonitor<ChanSigner> {
 		self.counterparty_payment_script.write(writer)?;
 		self.shutdown_script.write(writer)?;
 
-		self.key_derivation_params.write(writer)?;
+		self.channel_keys_id.write(writer)?;
 		self.holder_revocation_basepoint.write(writer)?;
 		writer.write_all(&self.funding_info.0.txid[..])?;
 		writer.write_all(&byte_utils::be16_to_array(self.funding_info.0.index))?;
@@ -967,7 +967,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		let counterparty_htlc_base_key = counterparty_channel_parameters.pubkeys.htlc_basepoint;
 		let counterparty_tx_cache = CounterpartyCommitmentTransaction { counterparty_delayed_payment_base_key, counterparty_htlc_base_key, on_counterparty_tx_csv, per_htlc: HashMap::new() };
 
-		let key_derivation_params = keys.key_derivation_params();
+		let channel_keys_id = keys.channel_keys_id();
 		let holder_revocation_basepoint = keys.pubkeys().revocation_basepoint;
 
 		let secp_ctx = Secp256k1::new();
@@ -1006,7 +1006,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 			counterparty_payment_script,
 			shutdown_script,
 
-			key_derivation_params,
+			channel_keys_id,
 			holder_revocation_basepoint,
 			funding_info,
 			current_counterparty_commitment_txid: None,
@@ -2206,7 +2206,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 						per_commitment_point: broadcasted_holder_revokable_script.1,
 						to_self_delay: self.on_holder_tx_csv,
 						output: outp.clone(),
-						key_derivation_params: self.key_derivation_params,
+						channel_keys_id: self.channel_keys_id,
 						revocation_pubkey: broadcasted_holder_revokable_script.2.clone(),
 					});
 					break;
@@ -2215,7 +2215,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 				spendable_output = Some(SpendableOutputDescriptor::StaticOutputCounterpartyPayment {
 					outpoint: OutPoint { txid: tx.txid(), index: i as u16 },
 					output: outp.clone(),
-					key_derivation_params: self.key_derivation_params,
+					channel_keys_id: self.channel_keys_id,
 				});
 				break;
 			} else if outp.script_pubkey == self.shutdown_script {
@@ -2332,7 +2332,7 @@ impl<'a, ChanSigner: ChannelKeys, K: KeysInterface<ChanKeySigner = ChanSigner>>
 		let counterparty_payment_script = Readable::read(reader)?;
 		let shutdown_script = Readable::read(reader)?;
 
-		let key_derivation_params = Readable::read(reader)?;
+		let channel_keys_id = Readable::read(reader)?;
 		let holder_revocation_basepoint = Readable::read(reader)?;
 		// Technically this can fail and serialize fail a round-trip, but only for serialization of
 		// barely-init'd ChannelMonitors that we can't do anything with.
@@ -2547,7 +2547,7 @@ impl<'a, ChanSigner: ChannelKeys, K: KeysInterface<ChanKeySigner = ChanSigner>>
 			counterparty_payment_script,
 			shutdown_script,
 
-			key_derivation_params,
+			channel_keys_id,
 			holder_revocation_basepoint,
 			funding_info,
 			current_counterparty_commitment_txid,
@@ -2675,7 +2675,7 @@ mod tests {
 			SecretKey::from_slice(&[41; 32]).unwrap(),
 			[41; 32],
 			0,
-			(0, 0)
+			[0; 32]
 		);
 
 		let counterparty_pubkeys = ChannelPublicKeys {

lightning/src/chain/keysinterface.rs

@@ -100,7 +100,7 @@ pub enum SpendableOutputDescriptor {
 		output: TxOut,
 		/// The channel keys state used to proceed to derivation of signing key. Must
 		/// be pass to KeysInterface::derive_channel_keys.
-		key_derivation_params: (u64, u64),
+		channel_keys_id: [u8; 32],
 		/// The revocation_pubkey used to derive witnessScript
 		revocation_pubkey: PublicKey
 	},
@@ -118,7 +118,7 @@ pub enum SpendableOutputDescriptor {
 		output: TxOut,
 		/// The channel keys state used to proceed to derivation of signing key. Must
 		/// be pass to KeysInterface::derive_channel_keys.
-		key_derivation_params: (u64, u64),
+		channel_keys_id: [u8; 32],
 	}
 }
 
@@ -130,22 +130,20 @@ impl Writeable for SpendableOutputDescriptor {
 				outpoint.write(writer)?;
 				output.write(writer)?;
 			},
-			&SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref per_commitment_point, ref to_self_delay, ref output, ref key_derivation_params, ref revocation_pubkey } => {
+			&SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref per_commitment_point, ref to_self_delay, ref output, ref channel_keys_id, ref revocation_pubkey } => {
 				1u8.write(writer)?;
 				outpoint.write(writer)?;
 				per_commitment_point.write(writer)?;
 				to_self_delay.write(writer)?;
 				output.write(writer)?;
-				key_derivation_params.0.write(writer)?;
-				key_derivation_params.1.write(writer)?;
+				channel_keys_id.write(writer)?;
 				revocation_pubkey.write(writer)?;
 			},
-			&SpendableOutputDescriptor::StaticOutputCounterpartyPayment { ref outpoint, ref output, ref key_derivation_params } => {
+			&SpendableOutputDescriptor::StaticOutputCounterpartyPayment { ref outpoint, ref output, ref channel_keys_id } => {
 				2u8.write(writer)?;
 				outpoint.write(writer)?;
 				output.write(writer)?;
-				key_derivation_params.0.write(writer)?;
-				key_derivation_params.1.write(writer)?;
+				channel_keys_id.write(writer)?;
 			},
 		}
 		Ok(())
@@ -164,13 +162,13 @@ impl Readable for SpendableOutputDescriptor {
 				per_commitment_point: Readable::read(reader)?,
 				to_self_delay: Readable::read(reader)?,
 				output: Readable::read(reader)?,
-				key_derivation_params: (Readable::read(reader)?, Readable::read(reader)?),
+				channel_keys_id: Readable::read(reader)?,
 				revocation_pubkey: Readable::read(reader)?,
 			}),
 			2u8 => Ok(SpendableOutputDescriptor::StaticOutputCounterpartyPayment {
 				outpoint: Readable::read(reader)?,
 				output: Readable::read(reader)?,
-				key_derivation_params: (Readable::read(reader)?, Readable::read(reader)?),
+				channel_keys_id: Readable::read(reader)?,
 			}),
 			_ => Err(DecodeError::InvalidValue),
 		}
@@ -221,10 +219,10 @@ pub trait ChannelKeys : Send+Clone + Writeable {
 	fn release_commitment_secret(&self, idx: u64) -> [u8; 32];
 	/// Gets the holder's channel public keys and basepoints
 	fn pubkeys(&self) -> &ChannelPublicKeys;
-	/// Gets arbitrary identifiers describing the set of keys which are provided back to you in
-	/// some SpendableOutputDescriptor types. These should be sufficient to identify this
+	/// Gets an arbitrary identifier describing the set of keys which are provided back to you in
+	/// some SpendableOutputDescriptor types. This should be sufficient to identify this
 	/// ChannelKeys object uniquely and lookup or re-derive its keys.
-	fn key_derivation_params(&self) -> (u64, u64);
+	fn channel_keys_id(&self) -> [u8; 32];
 
 	/// Create a signature for a counterparty's commitment transaction and associated HTLC transactions.
 	///
@@ -375,7 +373,7 @@ pub struct InMemoryChannelKeys {
 	/// The total value of this channel
 	channel_value_satoshis: u64,
 	/// Key derivation parameters
-	key_derivation_params: (u64, u64),
+	channel_keys_id: [u8; 32],
 }
 
 impl InMemoryChannelKeys {
@@ -389,7 +387,7 @@ impl InMemoryChannelKeys {
 		htlc_base_key: SecretKey,
 		commitment_seed: [u8; 32],
 		channel_value_satoshis: u64,
-		key_derivation_params: (u64, u64)) -> InMemoryChannelKeys {
+		channel_keys_id: [u8; 32]) -> InMemoryChannelKeys {
 		let holder_channel_pubkeys =
 			InMemoryChannelKeys::make_holder_keys(secp_ctx, &funding_key, &revocation_base_key,
 			                                     &payment_key, &delayed_payment_base_key,
@@ -404,7 +402,7 @@ impl InMemoryChannelKeys {
 			channel_value_satoshis,
 			holder_channel_pubkeys,
 			channel_parameters: None,
-			key_derivation_params,
+			channel_keys_id,
 		}
 	}
 
@@ -468,7 +466,7 @@ impl ChannelKeys for InMemoryChannelKeys {
 	}
 
 	fn pubkeys(&self) -> &ChannelPublicKeys { &self.holder_channel_pubkeys }
-	fn key_derivation_params(&self) -> (u64, u64) { self.key_derivation_params }
+	fn channel_keys_id(&self) -> [u8; 32] { self.channel_keys_id }
 
 	fn sign_counterparty_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
 		let trusted_tx = commitment_tx.trust();
@@ -600,8 +598,7 @@ impl Writeable for InMemoryChannelKeys {
 		self.commitment_seed.write(writer)?;
 		self.channel_parameters.write(writer)?;
 		self.channel_value_satoshis.write(writer)?;
-		self.key_derivation_params.0.write(writer)?;
-		self.key_derivation_params.1.write(writer)?;
+		self.channel_keys_id.write(writer)?;
 
 		Ok(())
 	}
@@ -622,8 +619,7 @@ impl Readable for InMemoryChannelKeys {
 			InMemoryChannelKeys::make_holder_keys(&secp_ctx, &funding_key, &revocation_base_key,
 			                                     &payment_key, &delayed_payment_base_key,
 			                                     &htlc_base_key);
-		let params_1 = Readable::read(reader)?;
-		let params_2 = Readable::read(reader)?;
+		let keys_id = Readable::read(reader)?;
 
 		Ok(InMemoryChannelKeys {
 			funding_key,
@@ -635,7 +631,7 @@ impl Readable for InMemoryChannelKeys {
 			channel_value_satoshis,
 			holder_channel_pubkeys,
 			channel_parameters: counterparty_channel_data,
-			key_derivation_params: (params_1, params_2),
+			channel_keys_id: keys_id,
 		})
 	}
 }
@@ -731,19 +727,19 @@ impl KeysManager {
 	/// Derive an old set of ChannelKeys for per-channel secrets based on a key derivation
 	/// parameters.
 	/// Key derivation parameters are accessible through a per-channel secrets
-	/// ChannelKeys::key_derivation_params and is provided inside DynamicOuputP2WSH in case of
+	/// ChannelKeys::channel_keys_id and is provided inside DynamicOuputP2WSH in case of
 	/// onchain output detection for which a corresponding delayed_payment_key must be derived.
-	pub fn derive_channel_keys(&self, channel_value_satoshis: u64, params_1: u64, params_2: u64) -> InMemoryChannelKeys {
-		let chan_id = ((params_1 & 0xFFFF_FFFF_0000_0000) >> 32) as u32;
+	pub fn derive_channel_keys(&self, channel_value_satoshis: u64, params: &[u8; 32]) -> InMemoryChannelKeys {
+		let chan_id = byte_utils::slice_to_be64(&params[0..8]);
+		assert!(chan_id <= std::u32::MAX as u64); // Otherwise the params field wasn't created by us
 		let mut unique_start = Sha256::engine();
-		unique_start.input(&byte_utils::be64_to_array(params_2));
-		unique_start.input(&byte_utils::be32_to_array(params_1 as u32));
+		unique_start.input(params);
 		unique_start.input(&self.seed);
 
 		// We only seriously intend to rely on the channel_master_key for true secure
 		// entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
 		// starting_time provided in the constructor) to be unique.
-		let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(chan_id).expect("key space exhausted")).expect("Your RNG is busted");
+		let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(chan_id as u32).expect("key space exhausted")).expect("Your RNG is busted");
 		unique_start.input(&child_privkey.private_key.key[..]);
 
 		let seed = Sha256::from_engine(unique_start).into_inner();
@@ -778,7 +774,7 @@ impl KeysManager {
 			htlc_base_key,
 			commitment_seed,
 			channel_value_satoshis,
-			(params_1, params_2),
+			params.clone()
 		)
 	}
 }
@@ -800,8 +796,12 @@ impl KeysInterface for KeysManager {
 
 	fn get_channel_keys(&self, _inbound: bool, channel_value_satoshis: u64) -> Self::ChanKeySigner {
 		let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
-		let ix_and_nanos: u64 = (child_ix as u64) << 32 | (self.starting_time_nanos as u64);
-		self.derive_channel_keys(channel_value_satoshis, ix_and_nanos, self.starting_time_secs)
+		assert!(child_ix <= std::u32::MAX as usize);
+		let mut id = [0; 32];
+		id[0..8].copy_from_slice(&byte_utils::be64_to_array(child_ix as u64));
+		id[8..16].copy_from_slice(&byte_utils::be64_to_array(self.starting_time_nanos as u64));
+		id[16..24].copy_from_slice(&byte_utils::be64_to_array(self.starting_time_secs));
+		self.derive_channel_keys(channel_value_satoshis, &id)
 	}
 
 	fn get_secure_random_bytes(&self) -> [u8; 32] {

lightning/src/ln/channel.rs

@@ -4657,7 +4657,7 @@ mod tests {
 			// These aren't set in the test vectors:
 			[0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff],
 			10_000_000,
-			(0, 0)
+			[0; 32]
 		);
 
 		assert_eq!(chan_keys.pubkeys().funding_pubkey.serialize()[..],

lightning/src/ln/functional_tests.rs

@@ -4662,7 +4662,7 @@ macro_rules! check_spendable_outputs {
 					Event::SpendableOutputs { ref outputs } => {
 						for outp in outputs {
 							match *outp {
-								SpendableOutputDescriptor::StaticOutputCounterpartyPayment { ref outpoint, ref output, ref key_derivation_params } => {
+								SpendableOutputDescriptor::StaticOutputCounterpartyPayment { ref outpoint, ref output, ref channel_keys_id } => {
 									let input = TxIn {
 										previous_output: outpoint.into_bitcoin_outpoint(),
 										script_sig: Script::new(),
@@ -4681,7 +4681,7 @@ macro_rules! check_spendable_outputs {
 									};
 									spend_tx.output[0].value -= (spend_tx.get_weight() + 2 + 1 + 73 + 35 + 3) as u64 / 4; // (Max weight + 3 (to round up)) / 4
 									let secp_ctx = Secp256k1::new();
-									let keys = $keysinterface.derive_channel_keys($chan_value, key_derivation_params.0, key_derivation_params.1);
+									let keys = $keysinterface.derive_channel_keys($chan_value, channel_keys_id);
 									let remotepubkey = keys.pubkeys().payment_point;
 									let witness_script = Address::p2pkh(&::bitcoin::PublicKey{compressed: true, key: remotepubkey}, Network::Testnet).script_pubkey();
 									let sighash = Message::from_slice(&bip143::SigHashCache::new(&spend_tx).signature_hash(0, &witness_script, output.value, SigHashType::All)[..]).unwrap();
@@ -4691,7 +4691,7 @@ macro_rules! check_spendable_outputs {
 									spend_tx.input[0].witness.push(remotepubkey.serialize().to_vec());
 									txn.push(spend_tx);
 								},
-								SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref per_commitment_point, ref to_self_delay, ref output, ref key_derivation_params, ref revocation_pubkey } => {
+								SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref per_commitment_point, ref to_self_delay, ref output, ref channel_keys_id, ref revocation_pubkey } => {
 									let input = TxIn {
 										previous_output: outpoint.into_bitcoin_outpoint(),
 										script_sig: Script::new(),
@@ -4709,7 +4709,7 @@ macro_rules! check_spendable_outputs {
 										output: vec![outp],
 									};
 									let secp_ctx = Secp256k1::new();
-									let keys = $keysinterface.derive_channel_keys($chan_value, key_derivation_params.0, key_derivation_params.1);
+									let keys = $keysinterface.derive_channel_keys($chan_value, channel_keys_id);
 									if let Ok(delayed_payment_key) = chan_utils::derive_private_key(&secp_ctx, &per_commitment_point, &keys.inner.delayed_payment_base_key) {
 
 										let delayed_payment_pubkey = PublicKey::from_secret_key(&secp_ctx, &delayed_payment_key);

lightning/src/util/enforcing_trait_impls.rs

@@ -89,7 +89,7 @@ impl ChannelKeys for EnforcingChannelKeys {
 	}
 
 	fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
-	fn key_derivation_params(&self) -> (u64, u64) { self.inner.key_derivation_params() }
+	fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 
 	fn sign_counterparty_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
 		self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);

lightning/src/util/test_utils.rs

@@ -482,8 +482,8 @@ impl TestKeysInterface {
 			revoked_commitments: Mutex::new(HashMap::new()),
 		}
 	}
-	pub fn derive_channel_keys(&self, channel_value_satoshis: u64, user_id_1: u64, user_id_2: u64) -> EnforcingChannelKeys {
-		let keys = self.backing.derive_channel_keys(channel_value_satoshis, user_id_1, user_id_2);
+	pub fn derive_channel_keys(&self, channel_value_satoshis: u64, id: &[u8; 32]) -> EnforcingChannelKeys {
+		let keys = self.backing.derive_channel_keys(channel_value_satoshis, id);
 		let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
 		EnforcingChannelKeys::new_with_revoked(keys, revoked_commitment, self.disable_revocation_policy_check)
 	}