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.

diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs
index 1ef109d43108e8a4ef74ecdb5641d2a647fc740f..7745afb419700642c2ecd6453a962fe3e73f93d8 100644 (file)
--- 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<T: secp256k1::Signing>(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
+       ///
+       /// 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<T: secp256k1::Signing + secp256k1::Verification>(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option<HTLCOutputInCommitment>, on_remote_tx_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
 
        /// 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<T: secp256k1::Signing>(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
-               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<T: secp256k1::Signing + secp256k1::Verification>(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option<HTLCOutputInCommitment>, on_remote_tx_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
+               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<T: secp256k1::Signing>(&self, htlc_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option<PaymentPreimage>, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {

diff --git a/lightning/src/ln/onchaintx.rs b/lightning/src/ln/onchaintx.rs
index 012668636a897ef0a64bb2b34d1f12e10ee6f237..e27315a8f075bd647d19c6e1ea66a5555ae9fea7 100644 (file)
--- a/lightning/src/ln/onchaintx.rs
+++ b/lightning/src/ln/onchaintx.rs
@@ -582,7 +582,7 @@ impl<ChanSigner: ChannelKeys> OnchainTxHandler<ChanSigner> {
                                                                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 5c5b7044334a9a44322a75c588395726242eacc6..184df41ffc5c3ef3fbe2f319ab94e2fdc00a9b5e 100644 (file)
--- 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<T: secp256k1::Signing>(&self, justice_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_key: &SecretKey, revocation_pubkey: &PublicKey, is_htlc: bool, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
-               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<T: secp256k1::Signing + secp256k1::Verification>(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &Option<HTLCOutputInCommitment>, on_remote_tx_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
+               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<T: secp256k1::Signing>(&self, htlc_tx: &Transaction, input: usize, witness_script: &Script, amount: u64, per_commitment_point: &PublicKey, preimage: &Option<PaymentPreimage>, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {