Merge pull request #1106 from TheBlueMatt/2021-10-no-perm-err-broadcast
[rust-lightning] / lightning / src / ln / chan_utils.rs
index 41d1eff856a71ed88cf8f43c14d8ffe234d27447..df0378938b42eeb0b1ff0fbd1413f6f140617a12 100644 (file)
@@ -26,10 +26,10 @@ use util::ser::{Readable, Writeable, Writer};
 use util::{byte_utils, transaction_utils};
 
 use bitcoin::hash_types::WPubkeyHash;
-use bitcoin::secp256k1::{SecretKey, PublicKey};
+use bitcoin::secp256k1::{SecretKey, PublicKey, Scalar};
 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature, Message};
 use bitcoin::secp256k1::Error as SecpError;
-use bitcoin::{secp256k1, Witness};
+use bitcoin::{PackedLockTime, secp256k1, Sequence, Witness};
 
 use io;
 use prelude::*;
@@ -42,6 +42,12 @@ use chain;
 use util::crypto::sign;
 
 pub(crate) const MAX_HTLCS: u16 = 483;
+pub(crate) const OFFERED_HTLC_SCRIPT_WEIGHT: usize = 133;
+pub(crate) const OFFERED_HTLC_SCRIPT_WEIGHT_ANCHORS: usize = 136;
+// The weight of `accepted_htlc_script` can vary in function of its CLTV argument value. We define a
+// range that encompasses both its non-anchors and anchors variants.
+pub(crate) const MIN_ACCEPTED_HTLC_SCRIPT_WEIGHT: usize = 136;
+pub(crate) const MAX_ACCEPTED_HTLC_SCRIPT_WEIGHT: usize = 143;
 
 /// Gets the weight for an HTLC-Success transaction.
 #[inline]
@@ -60,18 +66,72 @@ pub fn htlc_timeout_tx_weight(opt_anchors: bool) -> u64 {
 }
 
 #[derive(PartialEq)]
-pub(crate) enum HTLCType {
-       AcceptedHTLC,
-       OfferedHTLC
+pub(crate) enum HTLCClaim {
+       OfferedTimeout,
+       OfferedPreimage,
+       AcceptedTimeout,
+       AcceptedPreimage,
+       Revocation,
 }
 
-impl HTLCType {
-       /// Check if a given tx witnessScript len matchs one of a pre-signed HTLC
-       pub(crate) fn scriptlen_to_htlctype(witness_script_len: usize) ->  Option<HTLCType> {
-               if witness_script_len == 133 {
-                       Some(HTLCType::OfferedHTLC)
-               } else if witness_script_len >= 136 && witness_script_len <= 139 {
-                       Some(HTLCType::AcceptedHTLC)
+impl HTLCClaim {
+       /// Check if a given input witness attempts to claim a HTLC.
+       pub(crate) fn from_witness(witness: &Witness) -> Option<Self> {
+               debug_assert_eq!(OFFERED_HTLC_SCRIPT_WEIGHT_ANCHORS, MIN_ACCEPTED_HTLC_SCRIPT_WEIGHT);
+               if witness.len() < 2 {
+                       return None;
+               }
+               let witness_script = witness.last().unwrap();
+               let second_to_last = witness.second_to_last().unwrap();
+               if witness_script.len() == OFFERED_HTLC_SCRIPT_WEIGHT {
+                       if witness.len() == 3 && second_to_last.len() == 33 {
+                               // <revocation sig> <revocationpubkey> <witness_script>
+                               Some(Self::Revocation)
+                       } else if witness.len() == 3 && second_to_last.len() == 32 {
+                               // <remotehtlcsig> <payment_preimage> <witness_script>
+                               Some(Self::OfferedPreimage)
+                       } else if witness.len() == 5 && second_to_last.len() == 0 {
+                               // 0 <remotehtlcsig> <localhtlcsig> <> <witness_script>
+                               Some(Self::OfferedTimeout)
+                       } else {
+                               None
+                       }
+               } else if witness_script.len() == OFFERED_HTLC_SCRIPT_WEIGHT_ANCHORS {
+                       // It's possible for the weight of `offered_htlc_script` and `accepted_htlc_script` to
+                       // match so we check for both here.
+                       if witness.len() == 3 && second_to_last.len() == 33 {
+                               // <revocation sig> <revocationpubkey> <witness_script>
+                               Some(Self::Revocation)
+                       } else if witness.len() == 3 && second_to_last.len() == 32 {
+                               // <remotehtlcsig> <payment_preimage> <witness_script>
+                               Some(Self::OfferedPreimage)
+                       } else if witness.len() == 5 && second_to_last.len() == 0 {
+                               // 0 <remotehtlcsig> <localhtlcsig> <> <witness_script>
+                               Some(Self::OfferedTimeout)
+                       } else if witness.len() == 3 && second_to_last.len() == 0 {
+                               // <remotehtlcsig> <> <witness_script>
+                               Some(Self::AcceptedTimeout)
+                       } else if witness.len() == 5 && second_to_last.len() == 32 {
+                               // 0 <remotehtlcsig> <localhtlcsig> <payment_preimage> <witness_script>
+                               Some(Self::AcceptedPreimage)
+                       } else {
+                               None
+                       }
+               } else if witness_script.len() > MIN_ACCEPTED_HTLC_SCRIPT_WEIGHT &&
+                       witness_script.len() <= MAX_ACCEPTED_HTLC_SCRIPT_WEIGHT {
+                       // Handle remaining range of ACCEPTED_HTLC_SCRIPT_WEIGHT.
+                       if witness.len() == 3 && second_to_last.len() == 33 {
+                               // <revocation sig> <revocationpubkey> <witness_script>
+                               Some(Self::Revocation)
+                       } else if witness.len() == 3 && second_to_last.len() == 0 {
+                               // <remotehtlcsig> <> <witness_script>
+                               Some(Self::AcceptedTimeout)
+                       } else if witness.len() == 5 && second_to_last.len() == 32 {
+                               // 0 <remotehtlcsig> <localhtlcsig> <payment_preimage> <witness_script>
+                               Some(Self::AcceptedPreimage)
+                       } else {
+                               None
+                       }
                } else {
                        None
                }
@@ -101,7 +161,7 @@ pub fn build_closing_transaction(to_holder_value_sat: u64, to_counterparty_value
                ins.push(TxIn {
                        previous_output: funding_outpoint,
                        script_sig: Script::new(),
-                       sequence: 0xffffffff,
+                       sequence: Sequence::MAX,
                        witness: Witness::new(),
                });
                ins
@@ -132,7 +192,7 @@ pub fn build_closing_transaction(to_holder_value_sat: u64, to_counterparty_value
 
        Transaction {
                version: 2,
-               lock_time: 0,
+               lock_time: PackedLockTime::ZERO,
                input: txins,
                output: outputs,
        }
@@ -264,9 +324,7 @@ pub fn derive_private_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_co
        sha.input(&PublicKey::from_secret_key(&secp_ctx, &base_secret).serialize());
        let res = Sha256::from_engine(sha).into_inner();
 
-       let mut key = base_secret.clone();
-       key.add_assign(&res)?;
-       Ok(key)
+       base_secret.clone().add_tweak(&Scalar::from_be_bytes(res).unwrap())
 }
 
 /// Derives a per-commitment-transaction public key (eg an htlc key or a delayed_payment key)
@@ -287,7 +345,7 @@ pub fn derive_public_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_com
 
 /// Derives a per-commitment-transaction revocation key from its constituent parts.
 ///
-/// Only the cheating participant owns a valid witness to propagate a revoked 
+/// Only the cheating participant owns a valid witness to propagate a revoked
 /// commitment transaction, thus per_commitment_secret always come from cheater
 /// and revocation_base_secret always come from punisher, which is the broadcaster
 /// of the transaction spending with this key knowledge.
@@ -313,19 +371,16 @@ pub fn derive_private_revocation_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1
                Sha256::from_engine(sha).into_inner()
        };
 
-       let mut countersignatory_contrib = countersignatory_revocation_base_secret.clone();
-       countersignatory_contrib.mul_assign(&rev_append_commit_hash_key)?;
-       let mut broadcaster_contrib = per_commitment_secret.clone();
-       broadcaster_contrib.mul_assign(&commit_append_rev_hash_key)?;
-       countersignatory_contrib.add_assign(&broadcaster_contrib[..])?;
-       Ok(countersignatory_contrib)
+       let countersignatory_contrib = countersignatory_revocation_base_secret.clone().mul_tweak(&Scalar::from_be_bytes(rev_append_commit_hash_key).unwrap())?;
+       let broadcaster_contrib = per_commitment_secret.clone().mul_tweak(&Scalar::from_be_bytes(commit_append_rev_hash_key).unwrap())?;
+       countersignatory_contrib.add_tweak(&Scalar::from_be_bytes(broadcaster_contrib.secret_bytes()).unwrap())
 }
 
 /// Derives a per-commitment-transaction revocation public key from its constituent parts. This is
 /// the public equivalend of derive_private_revocation_key - using only public keys to derive a
 /// public key instead of private keys.
 ///
-/// Only the cheating participant owns a valid witness to propagate a revoked 
+/// Only the cheating participant owns a valid witness to propagate a revoked
 /// commitment transaction, thus per_commitment_point always come from cheater
 /// and revocation_base_point always come from punisher, which is the broadcaster
 /// of the transaction spending with this key knowledge.
@@ -348,10 +403,8 @@ pub fn derive_public_revocation_key<T: secp256k1::Verification>(secp_ctx: &Secp2
                Sha256::from_engine(sha).into_inner()
        };
 
-       let mut countersignatory_contrib = countersignatory_revocation_base_point.clone();
-       countersignatory_contrib.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
-       let mut broadcaster_contrib = per_commitment_point.clone();
-       broadcaster_contrib.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
+       let countersignatory_contrib = countersignatory_revocation_base_point.clone().mul_tweak(&secp_ctx, &Scalar::from_be_bytes(rev_append_commit_hash_key).unwrap())?;
+       let broadcaster_contrib = per_commitment_point.clone().mul_tweak(&secp_ctx, &Scalar::from_be_bytes(commit_append_rev_hash_key).unwrap())?;
        countersignatory_contrib.combine(&broadcaster_contrib)
 }
 
@@ -614,7 +667,7 @@ pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, conte
                        vout: htlc.transaction_output_index.expect("Can't build an HTLC transaction for a dust output"),
                },
                script_sig: Script::new(),
-               sequence: if opt_anchors { 1 } else { 0 },
+               sequence: Sequence(if opt_anchors { 1 } else { 0 }),
                witness: Witness::new(),
        });
 
@@ -623,17 +676,22 @@ pub fn build_htlc_transaction(commitment_txid: &Txid, feerate_per_kw: u32, conte
        } else {
                htlc_success_tx_weight(opt_anchors)
        };
-       let total_fee = feerate_per_kw as u64 * weight / 1000;
+       let output_value = if opt_anchors {
+               htlc.amount_msat / 1000
+       } else {
+               let total_fee = feerate_per_kw as u64 * weight / 1000;
+               htlc.amount_msat / 1000 - total_fee
+       };
 
        let mut txouts: Vec<TxOut> = Vec::new();
        txouts.push(TxOut {
                script_pubkey: get_revokeable_redeemscript(revocation_key, contest_delay, broadcaster_delayed_payment_key).to_v0_p2wsh(),
-               value: htlc.amount_msat / 1000 - total_fee //TODO: BOLT 3 does not specify if we should add amount_msat before dividing or if we should divide by 1000 before subtracting (as we do here)
+               value: output_value,
        });
 
        Transaction {
                version: 2,
-               lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
+               lock_time: PackedLockTime(if htlc.offered { htlc.cltv_expiry } else { 0 }),
                input: txins,
                output: txouts,
        }
@@ -687,7 +745,8 @@ pub struct ChannelTransactionParameters {
        pub counterparty_parameters: Option<CounterpartyChannelTransactionParameters>,
        /// The late-bound funding outpoint
        pub funding_outpoint: Option<chain::transaction::OutPoint>,
-       /// Are anchors used for this channel.  Boolean is serialization backwards-compatible
+       /// Are anchors (zero fee HTLC transaction variant) used for this channel. Boolean is
+       /// serialization backwards-compatible.
        pub opt_anchors: Option<()>
 }
 
@@ -863,7 +922,7 @@ impl HolderCommitmentTransaction {
                        holder_selected_contest_delay: 0,
                        is_outbound_from_holder: false,
                        counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: channel_pubkeys.clone(), selected_contest_delay: 0 }),
-                       funding_outpoint: Some(chain::transaction::OutPoint { txid: Default::default(), index: 0 }),
+                       funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
                        opt_anchors: None
                };
                let mut htlcs_with_aux: Vec<(_, ())> = Vec::new();
@@ -1167,7 +1226,7 @@ impl CommitmentTransaction {
        fn make_transaction(obscured_commitment_transaction_number: u64, txins: Vec<TxIn>, outputs: Vec<TxOut>) -> Transaction {
                Transaction {
                        version: 2,
-                       lock_time: ((0x20 as u32) << 8 * 3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32),
+                       lock_time: PackedLockTime(((0x20 as u32) << 8 * 3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32)),
                        input: txins,
                        output: outputs,
                }
@@ -1291,8 +1350,8 @@ impl CommitmentTransaction {
                        ins.push(TxIn {
                                previous_output: channel_parameters.funding_outpoint(),
                                script_sig: Script::new(),
-                               sequence: ((0x80 as u32) << 8 * 3)
-                                       | ((obscured_commitment_transaction_number >> 3 * 8) as u32),
+                               sequence: Sequence(((0x80 as u32) << 8 * 3)
+                                       | ((obscured_commitment_transaction_number >> 3 * 8) as u32)),
                                witness: Witness::new(),
                        });
                        ins
@@ -1508,7 +1567,8 @@ mod tests {
        use bitcoin::secp256k1::{PublicKey, SecretKey, Secp256k1};
        use util::test_utils;
        use chain::keysinterface::{KeysInterface, BaseSign};
-       use bitcoin::Network;
+       use bitcoin::{Network, Txid};
+       use bitcoin::hashes::Hash;
        use ln::PaymentHash;
        use bitcoin::hashes::hex::ToHex;
 
@@ -1533,7 +1593,7 @@ mod tests {
                        holder_selected_contest_delay: 0,
                        is_outbound_from_holder: false,
                        counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: counterparty_pubkeys.clone(), selected_contest_delay: 0 }),
-                       funding_outpoint: Some(chain::transaction::OutPoint { txid: Default::default(), index: 0 }),
+                       funding_outpoint: Some(chain::transaction::OutPoint { txid: Txid::all_zeros(), index: 0 }),
                        opt_anchors: None
                };