From 78b967f5b0a1ad7c135cd459895047fa697260fa Mon Sep 17 00:00:00 2001 From: Wilmer Paulino Date: Wed, 19 Apr 2023 15:08:29 -0700 Subject: [PATCH] Generate local signatures with additional randomness Previously, our local signatures would always be deterministic, whether we'd grind for low R value signatures or not. For peers supporting SegWit, Bitcoin Core will generally use a transaction's witness-txid, as opposed to its txid, to advertise transactions. Therefore, to ensure a transaction has the best chance to propagate across node mempools in the network, each of its broadcast attempts should have a unique/distinct witness-txid, which we can achieve by introducing random nonce data when generating local signatures, such that they are no longer deterministic. --- lightning/src/chain/keysinterface.rs | 28 ++++++++++++++-------------- lightning/src/ln/chan_utils.rs | 24 ++++++++++++++++++------ lightning/src/ln/functional_tests.rs | 4 ++-- lightning/src/ln/payment_tests.rs | 4 ++-- lightning/src/util/crypto.rs | 20 ++++++++++++++++++++ 5 files changed, 56 insertions(+), 24 deletions(-) diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs index 8d522a3b..f291f4c8 100644 --- a/lightning/src/chain/keysinterface.rs +++ b/lightning/src/chain/keysinterface.rs @@ -32,7 +32,7 @@ use bitcoin::secp256k1::ecdsa::RecoverableSignature; use bitcoin::{PackedLockTime, secp256k1, Sequence, Witness}; use crate::util::transaction_utils; -use crate::util::crypto::{hkdf_extract_expand_twice, sign}; +use crate::util::crypto::{hkdf_extract_expand_twice, sign, sign_with_aux_rand}; use crate::util::ser::{Writeable, Writer, Readable, ReadableArgs}; use crate::chain::transaction::OutPoint; #[cfg(anchors)] @@ -713,7 +713,7 @@ impl InMemorySigner { let remotepubkey = self.pubkeys().payment_point; let witness_script = bitcoin::Address::p2pkh(&::bitcoin::PublicKey{compressed: true, inner: remotepubkey}, Network::Testnet).script_pubkey(); let sighash = hash_to_message!(&sighash::SighashCache::new(spend_tx).segwit_signature_hash(input_idx, &witness_script, descriptor.output.value, EcdsaSighashType::All).unwrap()[..]); - let remotesig = sign(secp_ctx, &sighash, &self.payment_key); + let remotesig = sign_with_aux_rand(secp_ctx, &sighash, &self.payment_key, &self); let payment_script = bitcoin::Address::p2wpkh(&::bitcoin::PublicKey{compressed: true, inner: remotepubkey}, Network::Bitcoin).unwrap().script_pubkey(); if payment_script != descriptor.output.script_pubkey { return Err(()); } @@ -749,7 +749,7 @@ impl InMemorySigner { let delayed_payment_pubkey = PublicKey::from_secret_key(&secp_ctx, &delayed_payment_key); let witness_script = chan_utils::get_revokeable_redeemscript(&descriptor.revocation_pubkey, descriptor.to_self_delay, &delayed_payment_pubkey); let sighash = hash_to_message!(&sighash::SighashCache::new(spend_tx).segwit_signature_hash(input_idx, &witness_script, descriptor.output.value, EcdsaSighashType::All).unwrap()[..]); - let local_delayedsig = sign(secp_ctx, &sighash, &delayed_payment_key); + let local_delayedsig = sign_with_aux_rand(secp_ctx, &sighash, &delayed_payment_key, &self); let payment_script = bitcoin::Address::p2wsh(&witness_script, Network::Bitcoin).script_pubkey(); if descriptor.output.script_pubkey != payment_script { return Err(()); } @@ -810,7 +810,7 @@ impl EcdsaChannelSigner for InMemorySigner { let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey); let built_tx = trusted_tx.built_transaction(); - let commitment_sig = built_tx.sign(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx); + let commitment_sig = built_tx.sign_counterparty_commitment(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx); let commitment_txid = built_tx.txid; let mut htlc_sigs = Vec::with_capacity(commitment_tx.htlcs().len()); @@ -835,9 +835,9 @@ impl EcdsaChannelSigner for InMemorySigner { let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key); let funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey); let trusted_tx = commitment_tx.trust(); - let sig = trusted_tx.built_transaction().sign(&self.funding_key, &funding_redeemscript, self.channel_value_satoshis, secp_ctx); + let sig = trusted_tx.built_transaction().sign_holder_commitment(&self.funding_key, &funding_redeemscript, self.channel_value_satoshis, &self, secp_ctx); let channel_parameters = self.get_channel_parameters(); - let htlc_sigs = trusted_tx.get_htlc_sigs(&self.htlc_base_key, &channel_parameters.as_holder_broadcastable(), secp_ctx)?; + let htlc_sigs = trusted_tx.get_htlc_sigs(&self.htlc_base_key, &channel_parameters.as_holder_broadcastable(), &self, secp_ctx)?; Ok((sig, htlc_sigs)) } @@ -846,9 +846,9 @@ impl EcdsaChannelSigner for InMemorySigner { let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key); let funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &self.counterparty_pubkeys().funding_pubkey); let trusted_tx = commitment_tx.trust(); - let sig = trusted_tx.built_transaction().sign(&self.funding_key, &funding_redeemscript, self.channel_value_satoshis, secp_ctx); + let sig = trusted_tx.built_transaction().sign_holder_commitment(&self.funding_key, &funding_redeemscript, self.channel_value_satoshis, &self, secp_ctx); let channel_parameters = self.get_channel_parameters(); - let htlc_sigs = trusted_tx.get_htlc_sigs(&self.htlc_base_key, &channel_parameters.as_holder_broadcastable(), secp_ctx)?; + let htlc_sigs = trusted_tx.get_htlc_sigs(&self.htlc_base_key, &channel_parameters.as_holder_broadcastable(), &self, secp_ctx)?; Ok((sig, htlc_sigs)) } @@ -862,7 +862,7 @@ impl EcdsaChannelSigner for InMemorySigner { }; let mut sighash_parts = sighash::SighashCache::new(justice_tx); let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]); - return Ok(sign(secp_ctx, &sighash, &revocation_key)) + return Ok(sign_with_aux_rand(secp_ctx, &sighash, &revocation_key, &self)) } fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1) -> Result { @@ -876,7 +876,7 @@ impl EcdsaChannelSigner for InMemorySigner { }; let mut sighash_parts = sighash::SighashCache::new(justice_tx); let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]); - return Ok(sign(secp_ctx, &sighash, &revocation_key)) + return Ok(sign_with_aux_rand(secp_ctx, &sighash, &revocation_key, &self)) } #[cfg(anchors)] @@ -894,7 +894,7 @@ impl EcdsaChannelSigner for InMemorySigner { let our_htlc_private_key = chan_utils::derive_private_key( &secp_ctx, &per_commitment_point, &self.htlc_base_key ); - Ok(sign(&secp_ctx, &hash_to_message!(sighash), &our_htlc_private_key)) + Ok(sign_with_aux_rand(&secp_ctx, &hash_to_message!(sighash), &our_htlc_private_key, &self)) } fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1) -> Result { @@ -905,7 +905,7 @@ impl EcdsaChannelSigner for InMemorySigner { let witness_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, self.opt_anchors(), &counterparty_htlcpubkey, &htlcpubkey, &revocation_pubkey); let mut sighash_parts = sighash::SighashCache::new(htlc_tx); let sighash = hash_to_message!(&sighash_parts.segwit_signature_hash(input, &witness_script, amount, EcdsaSighashType::All).unwrap()[..]); - Ok(sign(secp_ctx, &sighash, &htlc_key)) + Ok(sign_with_aux_rand(secp_ctx, &sighash, &htlc_key, &self)) } fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1) -> Result { @@ -921,7 +921,7 @@ impl EcdsaChannelSigner for InMemorySigner { let sighash = sighash::SighashCache::new(&*anchor_tx).segwit_signature_hash( input, &witness_script, ANCHOR_OUTPUT_VALUE_SATOSHI, EcdsaSighashType::All, ).unwrap(); - Ok(sign(secp_ctx, &hash_to_message!(&sighash[..]), &self.funding_key)) + Ok(sign_with_aux_rand(secp_ctx, &hash_to_message!(&sighash[..]), &self.funding_key, &self)) } fn sign_channel_announcement_with_funding_key( @@ -1273,7 +1273,7 @@ impl KeysManager { if payment_script != output.script_pubkey { return Err(()); }; let sighash = hash_to_message!(&sighash::SighashCache::new(&spend_tx).segwit_signature_hash(input_idx, &witness_script, output.value, EcdsaSighashType::All).unwrap()[..]); - let sig = sign(secp_ctx, &sighash, &secret.private_key); + let sig = sign_with_aux_rand(secp_ctx, &sighash, &secret.private_key, &self); let mut sig_ser = sig.serialize_der().to_vec(); sig_ser.push(EcdsaSighashType::All as u8); spend_tx.input[input_idx].witness.push(sig_ser); diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs index 533da977..9699cc78 100644 --- a/lightning/src/ln/chan_utils.rs +++ b/lightning/src/ln/chan_utils.rs @@ -21,6 +21,7 @@ use bitcoin::hashes::sha256::Hash as Sha256; use bitcoin::hashes::ripemd160::Hash as Ripemd160; use bitcoin::hash_types::{Txid, PubkeyHash}; +use crate::chain::keysinterface::EntropySource; use crate::ln::{PaymentHash, PaymentPreimage}; use crate::ln::msgs::DecodeError; use crate::util::ser::{Readable, Writeable, Writer}; @@ -39,7 +40,7 @@ use crate::util::transaction_utils::sort_outputs; use crate::ln::channel::{INITIAL_COMMITMENT_NUMBER, ANCHOR_OUTPUT_VALUE_SATOSHI}; use core::ops::Deref; use crate::chain; -use crate::util::crypto::sign; +use crate::util::crypto::{sign, sign_with_aux_rand}; /// Maximum number of one-way in-flight HTLC (protocol-level value). pub const MAX_HTLCS: u16 = 483; @@ -1081,12 +1082,20 @@ impl BuiltCommitmentTransaction { hash_to_message!(sighash) } - /// Sign a transaction, either because we are counter-signing the counterparty's transaction or - /// because we are about to broadcast a holder transaction. - pub fn sign(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1) -> Signature { + /// Signs the counterparty's commitment transaction. + pub fn sign_counterparty_commitment(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1) -> Signature { let sighash = self.get_sighash_all(funding_redeemscript, channel_value_satoshis); sign(secp_ctx, &sighash, funding_key) } + + /// Signs the holder commitment transaction because we are about to broadcast it. + pub fn sign_holder_commitment( + &self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, + entropy_source: &ES, secp_ctx: &Secp256k1 + ) -> Signature where ES::Target: EntropySource { + let sighash = self.get_sighash_all(funding_redeemscript, channel_value_satoshis); + sign_with_aux_rand(secp_ctx, &sighash, funding_key, entropy_source) + } } /// This class tracks the per-transaction information needed to build a closing transaction and will @@ -1563,7 +1572,10 @@ impl<'a> TrustedCommitmentTransaction<'a> { /// The returned Vec has one entry for each HTLC, and in the same order. /// /// This function is only valid in the holder commitment context, it always uses EcdsaSighashType::All. - pub fn get_htlc_sigs(&self, htlc_base_key: &SecretKey, channel_parameters: &DirectedChannelTransactionParameters, secp_ctx: &Secp256k1) -> Result, ()> { + pub fn get_htlc_sigs( + &self, htlc_base_key: &SecretKey, channel_parameters: &DirectedChannelTransactionParameters, + entropy_source: &ES, secp_ctx: &Secp256k1, + ) -> Result, ()> where ES::Target: EntropySource { let inner = self.inner; let keys = &inner.keys; let txid = inner.built.txid; @@ -1577,7 +1589,7 @@ impl<'a> TrustedCommitmentTransaction<'a> { let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc, self.opt_anchors(), &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key); let sighash = hash_to_message!(&sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, EcdsaSighashType::All).unwrap()[..]); - ret.push(sign(secp_ctx, &sighash, &holder_htlc_key)); + ret.push(sign_with_aux_rand(secp_ctx, &sighash, &holder_htlc_key, entropy_source)); } Ok(ret) } diff --git a/lightning/src/ln/functional_tests.rs b/lightning/src/ln/functional_tests.rs index f2b05b6e..401667f3 100644 --- a/lightning/src/ln/functional_tests.rs +++ b/lightning/src/ln/functional_tests.rs @@ -3461,7 +3461,7 @@ fn test_htlc_ignore_latest_remote_commitment() { let node_txn = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().split_off(0); assert_eq!(node_txn.len(), 3); - assert_eq!(node_txn[0], node_txn[1]); + assert_eq!(node_txn[0].txid(), node_txn[1].txid()); let mut header = BlockHeader { version: 0x20000000, prev_blockhash: nodes[1].best_block_hash(), merkle_root: TxMerkleNode::all_zeros(), time: 42, bits: 42, nonce: 42 }; connect_block(&nodes[1], &Block { header, txdata: vec![node_txn[0].clone(), node_txn[1].clone()]}); @@ -9248,7 +9248,7 @@ fn do_test_tx_confirmed_skipping_blocks_immediate_broadcast(test_height_before_t // We should broadcast an HTLC transaction spending our funding transaction first let spending_txn = nodes[1].tx_broadcaster.txn_broadcasted.lock().unwrap().split_off(0); assert_eq!(spending_txn.len(), 2); - assert_eq!(spending_txn[0], node_txn[0]); + assert_eq!(spending_txn[0].txid(), node_txn[0].txid()); check_spends!(spending_txn[1], node_txn[0]); // We should also generate a SpendableOutputs event with the to_self output (as its // timelock is up). diff --git a/lightning/src/ln/payment_tests.rs b/lightning/src/ln/payment_tests.rs index 65b0fc00..51811ec6 100644 --- a/lightning/src/ln/payment_tests.rs +++ b/lightning/src/ln/payment_tests.rs @@ -343,7 +343,7 @@ fn do_retry_with_no_persist(confirm_before_reload: bool) { if !confirm_before_reload { let as_broadcasted_txn = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().split_off(0); assert_eq!(as_broadcasted_txn.len(), 1); - assert_eq!(as_broadcasted_txn[0], as_commitment_tx); + assert_eq!(as_broadcasted_txn[0].txid(), as_commitment_tx.txid()); } else { assert!(nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().is_empty()); } @@ -684,7 +684,7 @@ fn do_test_dup_htlc_onchain_fails_on_reload(persist_manager_post_event: bool, co connect_blocks(&nodes[0], TEST_FINAL_CLTV + LATENCY_GRACE_PERIOD_BLOCKS + 1); let node_txn = nodes[0].tx_broadcaster.txn_broadcasted.lock().unwrap().split_off(0); assert_eq!(node_txn.len(), 3); - assert_eq!(node_txn[0], node_txn[1]); + assert_eq!(node_txn[0].txid(), node_txn[1].txid()); check_spends!(node_txn[1], funding_tx); check_spends!(node_txn[2], node_txn[1]); let timeout_txn = vec![node_txn[2].clone()]; diff --git a/lightning/src/util/crypto.rs b/lightning/src/util/crypto.rs index 2f2d33b2..d4d15cfa 100644 --- a/lightning/src/util/crypto.rs +++ b/lightning/src/util/crypto.rs @@ -3,6 +3,10 @@ use bitcoin::hashes::hmac::{Hmac, HmacEngine}; use bitcoin::hashes::sha256::Hash as Sha256; use bitcoin::secp256k1::{Message, Secp256k1, SecretKey, ecdsa::Signature, Signing}; +use crate::chain::keysinterface::EntropySource; + +use core::ops::Deref; + macro_rules! hkdf_extract_expand { ($salt: expr, $ikm: expr) => {{ let mut hmac = HmacEngine::::new($salt); @@ -46,3 +50,19 @@ pub fn sign(ctx: &Secp256k1, msg: &Message, sk: &SecretKey) -> Si let sig = ctx.sign_ecdsa(msg, sk); sig } + +#[inline] +pub fn sign_with_aux_rand( + ctx: &Secp256k1, msg: &Message, sk: &SecretKey, entropy_source: &ES +) -> Signature where ES::Target: EntropySource { + #[cfg(feature = "grind_signatures")] + let sig = loop { + let sig = ctx.sign_ecdsa_with_noncedata(msg, sk, &entropy_source.get_secure_random_bytes()); + if sig.serialize_compact()[0] < 0x80 { + break sig; + } + }; + #[cfg(not(feature = "grind_signatures"))] + let sig = ctx.sign_ecdsa_with_noncedata(msg, sk, &entropy_source.get_secure_random_bytes()); + sig +} -- 2.30.2