From 06445b61893ab74ec09765a10c091415e877a82c Mon Sep 17 00:00:00 2001 From: Antoine Riard Date: Mon, 4 May 2020 02:35:54 -0400 Subject: [PATCH] Dry-up witnessScript in sign_remote_htlc_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 | 18 ++++++++++++------ lightning/src/ln/onchaintx.rs | 2 +- lightning/src/util/enforcing_trait_impls.rs | 4 ++-- 3 files changed, 15 insertions(+), 9 deletions(-) diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs index 7745afb4..654ba71e 100644 --- a/lightning/src/chain/keysinterface.rs +++ b/lightning/src/chain/keysinterface.rs @@ -25,7 +25,6 @@ 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::atomic::{AtomicUsize, Ordering}; use std::io::Error; @@ -311,10 +310,10 @@ pub trait ChannelKeys : Send+Clone { /// /// Amount is value of the output spent by this input, committed by sigs (BIP 143). /// - /// Preimage is solution for an offered HTLC haslock. A preimage sets to None hints this - /// htlc_tx as timing-out funds back to us on a received output. - //TODO: dry-up witness_script and pass pubkeys - 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; + /// Per_commitment_point is the dynamic point corresponding to the channel state + /// detected onchain. It has been generated by remote party and is used to derive + /// channel state keys, committed as part of witnessScript by sigs (BIP 143). + fn sign_remote_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1) -> Result; /// Create a signature for a (proposed) closing transaction. /// @@ -503,8 +502,15 @@ impl ChannelKeys for InMemoryChannelKeys { 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 { + fn sign_remote_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1) -> Result { if let Ok(htlc_key) = chan_utils::derive_private_key(&secp_ctx, &per_commitment_point, &self.htlc_base_key) { + let witness_script = if let Ok(revocation_pubkey) = chan_utils::derive_public_revocation_key(&secp_ctx, &per_commitment_point, &self.pubkeys().revocation_basepoint) { + if let Ok(remote_htlcpubkey) = chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.remote_pubkeys().htlc_basepoint) { + if let Ok(local_htlcpubkey) = chan_utils::derive_public_key(&secp_ctx, &per_commitment_point, &self.pubkeys().htlc_basepoint) { + chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &remote_htlcpubkey, &local_htlcpubkey, &revocation_pubkey) + } else { return Err(()) } + } else { return Err(()) } + } else { return Err(()) }; let sighash_parts = bip143::SighashComponents::new(&htlc_tx); let sighash = hash_to_message!(&sighash_parts.sighash_all(&htlc_tx.input[input], &witness_script, amount)[..]); return Ok(secp_ctx.sign(&sighash, &htlc_key)) diff --git a/lightning/src/ln/onchaintx.rs b/lightning/src/ln/onchaintx.rs index e27315a8..c99dc87d 100644 --- a/lightning/src/ln/onchaintx.rs +++ b/lightning/src/ln/onchaintx.rs @@ -602,7 +602,7 @@ impl OnchainTxHandler { let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &chan_keys.a_htlc_key, &chan_keys.b_htlc_key, &chan_keys.revocation_key); if !preimage.is_some() { bumped_tx.lock_time = htlc.cltv_expiry }; // Right now we don't aggregate time-locked transaction, if we do we should set lock_time before to avoid breaking hash computation - if let Ok(sig) = self.key_storage.sign_remote_htlc_transaction(&bumped_tx, i, &witness_script, htlc.amount_msat / 1000, &per_commitment_point, preimage, &self.secp_ctx) { + if let Ok(sig) = self.key_storage.sign_remote_htlc_transaction(&bumped_tx, i, &htlc.amount_msat / 1000, &per_commitment_point, htlc, &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 let &Some(preimage) = preimage { diff --git a/lightning/src/util/enforcing_trait_impls.rs b/lightning/src/util/enforcing_trait_impls.rs index 184df41f..59a8b5cf 100644 --- a/lightning/src/util/enforcing_trait_impls.rs +++ b/lightning/src/util/enforcing_trait_impls.rs @@ -110,8 +110,8 @@ impl ChannelKeys for EnforcingChannelKeys { 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 { - Ok(self.inner.sign_remote_htlc_transaction(htlc_tx, input, witness_script, amount, per_commitment_point, preimage, secp_ctx).unwrap()) + fn sign_remote_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1) -> Result { + Ok(self.inner.sign_remote_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap()) } fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1) -> Result { -- 2.30.2