diff --git a/lightning/src/chain/channelmonitor.rs b/lightning/src/chain/channelmonitor.rs index c2d3a43b1f4..bd5bd1fe9c6 100644 --- a/lightning/src/chain/channelmonitor.rs +++ b/lightning/src/chain/channelmonitor.rs @@ -4330,6 +4330,7 @@ impl ChannelMonitorImpl { revocation_pubkey: broadcasted_holder_revokable_script.2, channel_keys_id: self.channel_keys_id, channel_value_satoshis: self.channel_value_satoshis, + channel_transaction_parameters: Some(self.onchain_tx_handler.channel_transaction_parameters.clone()), })); } } diff --git a/lightning/src/ln/channel_keys.rs b/lightning/src/ln/channel_keys.rs index b577dc60008..838dd0b6f46 100644 --- a/lightning/src/ln/channel_keys.rs +++ b/lightning/src/ln/channel_keys.rs @@ -37,6 +37,23 @@ macro_rules! basepoint_impl { pub fn to_public_key(&self) -> PublicKey { self.0 } + + /// Derives a per-commitment-transaction (eg an htlc key or delayed_payment key) private key addition tweak + /// from a basepoint and a per_commitment_point: + /// `privkey = basepoint_secret + SHA256(per_commitment_point || basepoint)` + /// This calculates the hash part in the tweak derivation process, which is used to ensure + /// that each key is unique and cannot be guessed by an external party. It is equivalent + /// to the `from_basepoint` method, but without the addition operation, providing just the + /// tweak from the hash of the per_commitment_point and the basepoint. + pub fn derive_add_tweak( + &self, + per_commitment_point: &PublicKey, + ) -> [u8; 32] { + let mut sha = Sha256::engine(); + sha.input(&per_commitment_point.serialize()); + sha.input(&self.to_public_key().serialize()); + Sha256::from_engine(sha).to_byte_array() + } } impl From for $BasepointT { @@ -44,7 +61,6 @@ macro_rules! basepoint_impl { Self(value) } } - } } macro_rules! key_impl { diff --git a/lightning/src/sign/mod.rs b/lightning/src/sign/mod.rs index 9b5efee4b96..819369f5813 100644 --- a/lightning/src/sign/mod.rs +++ b/lightning/src/sign/mod.rs @@ -40,8 +40,9 @@ use bitcoin::{secp256k1, Sequence, Txid, Witness}; use crate::chain::transaction::OutPoint; use crate::crypto::utils::{hkdf_extract_expand_twice, sign, sign_with_aux_rand}; use crate::ln::chan_utils::{ - make_funding_redeemscript, ChannelPublicKeys, ChannelTransactionParameters, ClosingTransaction, - CommitmentTransaction, HTLCOutputInCommitment, HolderCommitmentTransaction, + get_revokeable_redeemscript, make_funding_redeemscript, ChannelPublicKeys, + ChannelTransactionParameters, ClosingTransaction, CommitmentTransaction, + HTLCOutputInCommitment, HolderCommitmentTransaction, }; use crate::ln::channel::ANCHOR_OUTPUT_VALUE_SATOSHI; use crate::ln::channel_keys::{ @@ -68,6 +69,7 @@ use crate::sign::ecdsa::{EcdsaChannelSigner, WriteableEcdsaChannelSigner}; use crate::sign::taproot::TaprootChannelSigner; use crate::util::atomic_counter::AtomicCounter; use crate::util::invoice::construct_invoice_preimage; +use core::convert::TryInto; use core::ops::Deref; use core::sync::atomic::{AtomicUsize, Ordering}; #[cfg(taproot)] @@ -108,7 +110,13 @@ pub struct DelayedPaymentOutputDescriptor { pub channel_keys_id: [u8; 32], /// The value of the channel which this output originated from, possibly indirectly. pub channel_value_satoshis: u64, + /// The channel public keys and other parameters needed to generate a spending transaction or to provide to a re-derived signer through + /// [`ChannelSigner::provide_channel_parameters`]. + /// + /// Added as optional, but always `Some` if the descriptor was produced in v0.0.123 or later. + pub channel_transaction_parameters: Option, } + impl DelayedPaymentOutputDescriptor { /// The maximum length a well-formed witness spending one of these should have. /// Note: If you have the grind_signatures feature enabled, this will be at least 1 byte @@ -127,6 +135,7 @@ impl_writeable_tlv_based!(DelayedPaymentOutputDescriptor, { (8, revocation_pubkey, required), (10, channel_keys_id, required), (12, channel_value_satoshis, required), + (13, channel_transaction_parameters, option), }); pub(crate) const P2WPKH_WITNESS_WEIGHT: u64 = 1 /* num stack items */ + @@ -155,6 +164,7 @@ pub struct StaticPaymentOutputDescriptor { /// Added as optional, but always `Some` if the descriptor was produced in v0.0.117 or later. pub channel_transaction_parameters: Option, } + impl StaticPaymentOutputDescriptor { /// Returns the `witness_script` of the spendable output. /// @@ -306,23 +316,121 @@ impl SpendableOutputDescriptor { /// /// This is not exported to bindings users as there is no standard serialization for an input. /// See [`Self::create_spendable_outputs_psbt`] instead. - pub fn to_psbt_input(&self) -> bitcoin::psbt::Input { + /// + /// The proprietary field is used to store add tweak for the signing key of this transaction. + /// See the [DelayedPaymentBasepoint::derive_add_tweak] docs for more info on add tweak and how to use it. + /// + /// To get the proprietary field use: + /// ``` + /// use bitcoin::psbt::{PartiallySignedTransaction}; + /// use bitcoin::hashes::hex::FromHex; + /// + /// # let s = "70736274ff0100520200000001dee978529ab3e61a2987bea5183713d0e6d5ceb5ac81100fdb54a1a2\ + /// # 69cef505000000000090000000011f26000000000000160014abb3ab63280d4ccc5c11d6b50fd427a8\ + /// # e19d6470000000000001012b10270000000000002200200afe4736760d814a2651bae63b572d935d9a\ + /// # b74a1a16c01774e341a32afa763601054d63210394a27a700617f5b7aee72bd4f8076b5770a582b7fb\ + /// # d1d4ee2ea3802cd3cfbe2067029000b27521034629b1c8fdebfaeb58a74cd181f485e2c462e594cb30\ + /// # 34dee655875f69f6c7c968ac20fc144c444b5f7370656e6461626c655f6f7574707574006164645f74\ + /// # 7765616b20a86534f38ad61dc580ef41c3886204adf0911b81619c1ad7a2f5b5de39a2ba600000"; + /// # let psbt = PartiallySignedTransaction::deserialize( as FromHex>::from_hex(s).unwrap().as_slice()).unwrap(); + /// let key = bitcoin::psbt::raw::ProprietaryKey { + /// prefix: "LDK_spendable_output".as_bytes().to_vec(), + /// subtype: 0, + /// key: "add_tweak".as_bytes().to_vec(), + /// }; + /// let value = psbt + /// .inputs + /// .first() + /// .expect("Unable to get add tweak as there are no inputs") + /// .proprietary + /// .get(&key) + /// .map(|x| x.to_owned()); + /// ``` + pub fn to_psbt_input( + &self, secp_ctx: &Secp256k1, + ) -> bitcoin::psbt::Input { match self { SpendableOutputDescriptor::StaticOutput { output, .. } => { // Is a standard P2WPKH, no need for witness script bitcoin::psbt::Input { witness_utxo: Some(output.clone()), ..Default::default() } }, - SpendableOutputDescriptor::DelayedPaymentOutput(descriptor) => { - // TODO we could add the witness script as well + SpendableOutputDescriptor::DelayedPaymentOutput(DelayedPaymentOutputDescriptor { + channel_transaction_parameters, + per_commitment_point, + revocation_pubkey, + to_self_delay, + output, + .. + }) => { + let delayed_payment_basepoint = channel_transaction_parameters + .as_ref() + .map(|params| params.holder_pubkeys.delayed_payment_basepoint); + + let (witness_script, add_tweak) = + if let Some(basepoint) = delayed_payment_basepoint.as_ref() { + let payment_key = DelayedPaymentKey::from_basepoint( + secp_ctx, + basepoint, + &per_commitment_point, + ); + // Required to derive signing key: privkey = basepoint_secret + SHA256(per_commitment_point || basepoint) + let add_tweak = basepoint.derive_add_tweak(&per_commitment_point); + ( + Some(get_revokeable_redeemscript( + &revocation_pubkey, + *to_self_delay, + &payment_key, + )), + Some(add_tweak), + ) + } else { + (None, None) + }; + bitcoin::psbt::Input { - witness_utxo: Some(descriptor.output.clone()), + witness_utxo: Some(output.clone()), + witness_script, + proprietary: add_tweak + .map(|add_tweak| { + [( + bitcoin::psbt::raw::ProprietaryKey { + // A non standard namespace for spendable outputs, used to store the tweak needed + // to derive the private key + prefix: "LDK_spendable_output".as_bytes().to_vec(), + subtype: 0, + key: "add_tweak".as_bytes().to_vec(), + }, + add_tweak.to_vec(), + )] + .into_iter() + .collect() + }) + .unwrap_or_default(), ..Default::default() } }, SpendableOutputDescriptor::StaticPaymentOutput(descriptor) => { - // TODO we could add the witness script as well + let witness_script = if let Some(true) = descriptor + .channel_transaction_parameters + .as_ref() + .and_then(|channel_params| Some(channel_params.supports_anchors())) + { + descriptor.witness_script() + } else { + descriptor.channel_transaction_parameters.as_ref().and_then(|channel_params| { + // Use simplified derivation, assuming `option_static_remotekey` is negotiated. + // `remote_payment_basepoint` is used as Payment Key. + let payment_point = channel_params.holder_pubkeys.payment_point; + Some(ScriptBuf::new_p2pkh( + &bitcoin::PublicKey::new(payment_point).pubkey_hash(), + )) + }) + }; + // With simplified derivation, the private payment key is equal to private payment basepoint, + // so add tweak is not needed. bitcoin::psbt::Input { witness_utxo: Some(descriptor.output.clone()), + witness_script, ..Default::default() } }, @@ -345,8 +453,8 @@ impl SpendableOutputDescriptor { /// does not match the one we can spend. /// /// We do not enforce that outputs meet the dust limit or that any output scripts are standard. - pub fn create_spendable_outputs_psbt( - descriptors: &[&SpendableOutputDescriptor], outputs: Vec, + pub fn create_spendable_outputs_psbt( + secp_ctx: &Secp256k1, descriptors: &[&SpendableOutputDescriptor], outputs: Vec, change_destination_script: ScriptBuf, feerate_sat_per_1000_weight: u32, locktime: Option, ) -> Result<(PartiallySignedTransaction, u64), ()> { @@ -438,7 +546,8 @@ impl SpendableOutputDescriptor { change_destination_script, )?; - let psbt_inputs = descriptors.iter().map(|d| d.to_psbt_input()).collect::>(); + let psbt_inputs = + descriptors.iter().map(|d| d.to_psbt_input(&secp_ctx)).collect::>(); let psbt = PartiallySignedTransaction { inputs: psbt_inputs, outputs: vec![Default::default(); tx.output.len()], @@ -2112,6 +2221,7 @@ impl OutputSpender for KeysManager { ) -> Result { let (mut psbt, expected_max_weight) = SpendableOutputDescriptor::create_spendable_outputs_psbt( + secp_ctx, descriptors, outputs, change_destination_script,