From 479e1c8ddfc6caa11cd4f872e0b7149534035423 Mon Sep 17 00:00:00 2001 From: Antoine Riard Date: Mon, 4 May 2020 02:20:56 -0400 Subject: [PATCH] Dry-up witnessScript in sign_justice_transaction Instead of blindly signing provided witnessScript, signer must derive channel keys corresponding to the provided per-commitment-point and regenerate templated witnessScript to ensure its syntax correctness. --- lightning/src/chain/keysinterface.rs | 50 ++++++++++++++++----- lightning/src/ln/onchaintx.rs | 2 +- lightning/src/util/enforcing_trait_impls.rs | 4 +- 3 files changed, 41 insertions(+), 15 deletions(-) diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs index 1ef109d43..7745afb41 100644 --- a/lightning/src/chain/keysinterface.rs +++ b/lightning/src/chain/keysinterface.rs @@ -280,9 +280,6 @@ pub trait ChannelKeys : Send+Clone { /// It may be called multiples time for same output(s) if a fee-bump is needed with regards /// to an upcoming timelock expiration. /// - /// Witness_script is a revokable witness script as defined in BOLT3 for `to_local`/HTLC - /// outputs. - /// /// Input index is a pointer towards outpoint spent, commited by sigs (BIP 143). /// /// Amount is value of the output spent by this input, committed by sigs (BIP 143). @@ -291,8 +288,14 @@ pub trait ChannelKeys : Send+Clone { /// revocating detected onchain transaction. It's not a _local_ secret key, therefore /// it may cross interfaces, a node compromise won't allow to spend revoked output without /// also compromissing revocation key. - //TODO: dry-up witness_script and pass pubkeys - fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1) -> Result; + /// + /// htlc holds HTLC elements (hash, timelock) if output spent is a HTLC one, committed as + /// part of witnessScript by sigs (BIP 143). + /// + /// on_remote_tx_csv is the relative lock-time challenge if output spent is on remote + /// balance or 2nd-stage HTLC transactions, committed as part of witnessScript by sigs + /// (BIP 143). + fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option, on_remote_tx_csv: u16, secp_ctx: &Secp256k1) -> Result; /// Create a signature for a claiming transaction for a HTLC output on a remote commitment /// transaction, either offered or received. @@ -468,13 +471,36 @@ impl ChannelKeys for InMemoryChannelKeys { local_commitment_tx.get_htlc_sigs(&self.htlc_base_key, local_csv, secp_ctx) } - fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1) -> Result { - 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(&justice_tx); - let sighash = hash_to_message!(&sighash_parts.sighash_all(&justice_tx.input[input], &witness_script, amount)[..]); - return Ok(secp_ctx.sign(&sighash, &revocation_key)) - } - Err(()) + fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option, on_remote_tx_csv: u16, secp_ctx: &Secp256k1) -> Result { + let revocation_key = match chan_utils::derive_private_revocation_key(&secp_ctx, &per_commitment_key, &self.revocation_base_key) { + Ok(revocation_key) => revocation_key, + Err(_) => return Err(()) + }; + let per_commitment_point = PublicKey::from_secret_key(secp_ctx, &per_commitment_key); + let revocation_pubkey = match chan_utils::derive_public_revocation_key(&secp_ctx, &per_commitment_point, &self.pubkeys().revocation_basepoint) { + Ok(revocation_pubkey) => revocation_pubkey, + Err(_) => return Err(()) + }; + let witness_script = if let &Some(ref htlc) = htlc { + let remote_htlcpubkey = match chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.remote_pubkeys().htlc_basepoint) { + Ok(remote_htlcpubkey) => remote_htlcpubkey, + Err(_) => return Err(()) + }; + let local_htlcpubkey = match chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.pubkeys().htlc_basepoint) { + Ok(local_htlcpubkey) => local_htlcpubkey, + Err(_) => return Err(()) + }; + chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &remote_htlcpubkey, &local_htlcpubkey, &revocation_pubkey) + } else { + let remote_delayedpubkey = match chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.remote_pubkeys().delayed_payment_basepoint) { + Ok(remote_delayedpubkey) => remote_delayedpubkey, + Err(_) => return Err(()) + }; + chan_utils::get_revokeable_redeemscript(&revocation_pubkey, on_remote_tx_csv, &remote_delayedpubkey) + }; + let sighash_parts = bip143::SighashComponents::new(&justice_tx); + let sighash = hash_to_message!(&sighash_parts.sighash_all(&justice_tx.input[input], &witness_script, amount)[..]); + return Ok(secp_ctx.sign(&sighash, &revocation_key)) } fn sign_remote_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option, secp_ctx: &Secp256k1) -> Result { diff --git a/lightning/src/ln/onchaintx.rs b/lightning/src/ln/onchaintx.rs index 012668636..e27315a8f 100644 --- a/lightning/src/ln/onchaintx.rs +++ b/lightning/src/ln/onchaintx.rs @@ -582,7 +582,7 @@ impl OnchainTxHandler { chan_utils::get_revokeable_redeemscript(&chan_keys.revocation_key, *on_remote_tx_csv, &chan_keys.a_delayed_payment_key) }; - if let Ok(sig) = self.key_storage.sign_justice_transaction(&bumped_tx, i, &witness_script, *amount, &per_commitment_key, &chan_keys.revocation_key, htlc.is_some(), &self.secp_ctx) { + if let Ok(sig) = self.key_storage.sign_justice_transaction(&bumped_tx, i, *amount, &per_commitment_key, htlc, *on_remote_tx_csv, &self.secp_ctx) { bumped_tx.input[i].witness.push(sig.serialize_der().to_vec()); bumped_tx.input[i].witness[0].push(SigHashType::All as u8); if htlc.is_some() { diff --git a/lightning/src/util/enforcing_trait_impls.rs b/lightning/src/util/enforcing_trait_impls.rs index 5c5b70443..184df41ff 100644 --- a/lightning/src/util/enforcing_trait_impls.rs +++ b/lightning/src/util/enforcing_trait_impls.rs @@ -106,8 +106,8 @@ impl ChannelKeys for EnforcingChannelKeys { Ok(self.inner.sign_local_commitment_htlc_transactions(local_commitment_tx, local_csv, secp_ctx).unwrap()) } - fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1) -> Result { - Ok(self.inner.sign_justice_transaction(justice_tx, input, witness_script, amount, per_commitment_key, revocation_pubkey, is_htlc, secp_ctx).unwrap()) + fn sign_justice_transaction(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option, on_remote_tx_csv: u16, secp_ctx: &Secp256k1) -> Result { + Ok(self.inner.sign_justice_transaction(justice_tx, input, amount, per_commitment_key, htlc, on_remote_tx_csv, secp_ctx).unwrap()) } fn sign_remote_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option, secp_ctx: &Secp256k1) -> Result { -- 2.39.5