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Move spendable output descriptors key behind signer interface #562

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Move spendable output descriptors key behind signer interface #562

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3244e41
Cache remote basepoint and remote_csv in new OnchainTxHandler::Remote…
Mar 24, 2020
3caa38f
Cache remote HTLC inside OnchainTxHandler::RemoteTxCache
Mar 24, 2020
ea8df9d
Replace is_htlc in InputMaterial by InputDescriptor
Mar 24, 2020
b082827
Build witness_script for justice tx inside OnchainTxHandler
Mar 24, 2020
bb5b14c
Move justice transaction signature behind ChanSigner
Mar 24, 2020
d2a6a78
Build witness_script for remote htlc transactions inside
Mar 24, 2020
5a8f68f
Move remote htlc transaction signature behind ChanSigner
Mar 24, 2020
4fd727f
Add test-only ChannelMonitor::get_chan_signer to sign spendable output
Mar 24, 2020
13a6604
Remove SecretKey from DynamicOutputP2WSH descriptor
Mar 24, 2020
7a23c0c
Remove SecretKey from DynamicOuputP2WPKH descriptor
Mar 24, 2020
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91 changes: 81 additions & 10 deletions lightning/src/chain/keysinterface.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,11 +2,12 @@
//! spendable on-chain outputs which the user owns and is responsible for using just as any other
//! on-chain output which is theirs.

use bitcoin::blockdata::transaction::{Transaction, OutPoint, TxOut};
use bitcoin::blockdata::transaction::{Transaction, OutPoint, TxOut, SigHashType};
use bitcoin::blockdata::script::{Script, Builder};
use bitcoin::blockdata::opcodes;
use bitcoin::network::constants::Network;
use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber};
use bitcoin::util::address::Address;
use bitcoin::util::bip143;

use bitcoin_hashes::{Hash, HashEngine};
Expand All @@ -26,6 +27,7 @@ use util::ser::{Writeable, Writer, Readable};
use ln::chan_utils;
use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys, LocalCommitmentTransaction};
use ln::msgs;
use ln::channelmanager::PaymentPreimage;

use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
Expand Down Expand Up @@ -64,8 +66,8 @@ pub enum SpendableOutputDescriptor {
DynamicOutputP2WSH {
/// The outpoint which is spendable
outpoint: OutPoint,
/// The secret key which must be used to sign the spending transaction
key: SecretKey,
/// Per commitment point to derive delayed_payment_key by key holder
per_commitment_point: PublicKey,
/// The witness redeemScript which is hashed to create the script_pubkey in the given output
witness_script: Script,
/// The nSequence value which must be set in the spending input to satisfy the OP_CSV in
Expand All @@ -83,7 +85,7 @@ pub enum SpendableOutputDescriptor {
/// The outpoint which is spendable
outpoint: OutPoint,
/// The secret key which must be used to sign the spending transaction
key: SecretKey,
per_commitment_point: PublicKey,
/// The output which is reference by the given outpoint
output: TxOut,
}
Expand All @@ -97,18 +99,18 @@ impl Writeable for SpendableOutputDescriptor {
outpoint.write(writer)?;
output.write(writer)?;
},
&SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref key, ref witness_script, ref to_self_delay, ref output } => {
&SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref per_commitment_point, ref witness_script, ref to_self_delay, ref output } => {
1u8.write(writer)?;
outpoint.write(writer)?;
key.write(writer)?;
per_commitment_point.write(writer)?;
witness_script.write(writer)?;
to_self_delay.write(writer)?;
output.write(writer)?;
},
&SpendableOutputDescriptor::DynamicOutputP2WPKH { ref outpoint, ref key, ref output } => {
&SpendableOutputDescriptor::DynamicOutputP2WPKH { ref outpoint, ref per_commitment_point, ref output } => {
2u8.write(writer)?;
outpoint.write(writer)?;
key.write(writer)?;
per_commitment_point.write(writer)?;
output.write(writer)?;
},
}
Expand All @@ -125,14 +127,14 @@ impl Readable for SpendableOutputDescriptor {
}),
1u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WSH {
outpoint: Readable::read(reader)?,
key: Readable::read(reader)?,
per_commitment_point: Readable::read(reader)?,
witness_script: Readable::read(reader)?,
to_self_delay: Readable::read(reader)?,
output: Readable::read(reader)?,
}),
2u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WPKH {
outpoint: Readable::read(reader)?,
key: Readable::read(reader)?,
per_commitment_point: Readable::read(reader)?,
output: Readable::read(reader)?,
}),
_ => Err(DecodeError::InvalidValue),
Expand Down Expand Up @@ -245,12 +247,24 @@ pub trait ChannelKeys : Send+Clone {
/// return value must contain a signature.
fn sign_local_commitment_htlc_transactions<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, local_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Vec<Option<Signature>>, ()>;

/// Signs a justice transaction.
fn sign_justice_transaction<T: secp256k1::Signing>(&self, bumped_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1<T>);

/// Signs a remote htlc transaction.
fn sign_remote_htlc_transaction<T: secp256k1::Signing>(&self, bumped_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option<PaymentPreimage>, secp_ctx: &Secp256k1<T>);

/// Create a signature for a (proposed) closing transaction.
///
/// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
/// chosen to forgo their output as dust.
fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;

/// Create a signature for a delayed transaction.
fn sign_delayed_transaction<T: secp256k1::Signing>(&self, spend_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, secp_ctx: &Secp256k1<T>);

/// Create a signture for a payment transaction spending a to_remote output on a remote commitment tx.
fn sign_payment_transaction<T: secp256k1::Signing>(&self, spend_tx: &mut Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, network: Network, secp_ctx: &Secp256k1<T>);

/// Signs a channel announcement message with our funding key, proving it comes from one
/// of the channel participants.
///
Expand Down Expand Up @@ -393,6 +407,38 @@ impl ChannelKeys for InMemoryChannelKeys {
local_commitment_tx.get_htlc_sigs(&self.htlc_base_key, local_csv, secp_ctx)
}

fn sign_justice_transaction<T: secp256k1::Signing>(&self, bumped_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1<T>) {
if let Ok(revocation_key) = chan_utils::derive_private_revocation_key(&secp_ctx, &per_commitment_key, &self.revocation_base_key) {
let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[input], &witness_script, amount)[..]);
let sig = secp_ctx.sign(&sighash, &revocation_key);
bumped_tx.input[input].witness.push(sig.serialize_der().to_vec());
bumped_tx.input[input].witness[0].push(SigHashType::All as u8);
if is_htlc {
bumped_tx.input[input].witness.push(revocation_pubkey.clone().serialize().to_vec());
} else {
bumped_tx.input[input].witness.push(vec!(1));
}
bumped_tx.input[input].witness.push(witness_script.clone().into_bytes());
}
}

fn sign_remote_htlc_transaction<T: secp256k1::Signing>(&self, bumped_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option<PaymentPreimage>, secp_ctx: &Secp256k1<T>) {
if let Ok(htlc_key) = chan_utils::derive_private_key(&secp_ctx, &per_commitment_point, &self.htlc_base_key) {
let sighash_parts = bip143::SighashComponents::new(&bumped_tx);
let sighash = hash_to_message!(&sighash_parts.sighash_all(&bumped_tx.input[input], &witness_script, amount)[..]);
let sig = secp_ctx.sign(&sighash, &htlc_key);
bumped_tx.input[input].witness.push(sig.serialize_der().to_vec());
bumped_tx.input[input].witness[0].push(SigHashType::All as u8);
if let &Some(preimage) = preimage {
bumped_tx.input[input].witness.push(preimage.0.to_vec());
} else {
bumped_tx.input[input].witness.push(vec![0]);
}
bumped_tx.input[input].witness.push(witness_script.clone().into_bytes());
}
}

fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
if closing_tx.input.len() != 1 { return Err(()); }
if closing_tx.input[0].witness.len() != 0 { return Err(()); }
Expand All @@ -407,6 +453,31 @@ impl ChannelKeys for InMemoryChannelKeys {
Ok(secp_ctx.sign(&sighash, &self.funding_key))
}

fn sign_delayed_transaction<T: secp256k1::Signing>(&self, spend_tx: &mut Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, secp_ctx: &Secp256k1<T>) {
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the witness_script could be derived here rather than passed in, if I'm not mistaken

if let Ok(htlc_key) = chan_utils::derive_private_key(&secp_ctx, &per_commitment_point, &self.delayed_payment_base_key) {
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failing here likely indicates a serious internal error, so should propagate the error to the caller

let sighash_parts = bip143::SighashComponents::new(&spend_tx);
let sighash = hash_to_message!(&sighash_parts.sighash_all(&spend_tx.input[input], witness_script, amount)[..]);
let local_delaysig = secp_ctx.sign(&sighash, &htlc_key);
spend_tx.input[0].witness.push(local_delaysig.serialize_der().to_vec());
spend_tx.input[0].witness[0].push(SigHashType::All as u8);
spend_tx.input[0].witness.push(vec!(0));
spend_tx.input[0].witness.push(witness_script.clone().into_bytes());
}
}

fn sign_payment_transaction<T: secp256k1::Signing>(&self, spend_tx: &mut Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, network: Network, secp_ctx: &Secp256k1<T>) {
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see two comments on sign_delayed_transaction

if let Ok(payment_key) = chan_utils::derive_private_key(&secp_ctx, &per_commitment_point, &self.payment_base_key) {
let remotepubkey = PublicKey::from_secret_key(&secp_ctx, &payment_key);
let witness_script = Address::p2pkh(&::bitcoin::PublicKey{compressed: true, key: remotepubkey}, network).script_pubkey();
let sighash_parts = bip143::SighashComponents::new(&spend_tx);
let sighash = hash_to_message!(&sighash_parts.sighash_all(&spend_tx.input[input], &witness_script, amount)[..]);
let remotesig = secp_ctx.sign(&sighash, &payment_key);
spend_tx.input[0].witness.push(remotesig.serialize_der().to_vec());
spend_tx.input[0].witness[0].push(SigHashType::All as u8);
spend_tx.input[0].witness.push(remotepubkey.serialize().to_vec());
}
}

fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
Ok(secp_ctx.sign(&msghash, &self.funding_key))
Expand Down
2 changes: 1 addition & 1 deletion lightning/src/ln/chan_utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -198,7 +198,7 @@ pub(super) fn derive_public_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>,
/// Derives a revocation key from its constituent parts.
/// Note that this is infallible iff we trust that at least one of the two input keys are randomly
/// generated (ie our own).
pub(super) fn derive_private_revocation_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_secret: &SecretKey, revocation_base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
pub fn derive_private_revocation_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_secret: &SecretKey, revocation_base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
let revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &revocation_base_secret);
let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);

Expand Down
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