--- /dev/null
+use bitcoin::blockdata::script::{Script,Builder};
+use bitcoin::blockdata::opcodes;
+use bitcoin::blockdata::transaction::{TxIn,TxOut,OutPoint,Transaction};
+
+use bitcoin_hashes::{Hash, HashEngine};
+use bitcoin_hashes::sha256::Hash as Sha256;
+use bitcoin_hashes::ripemd160::Hash as Ripemd160;
+use bitcoin_hashes::hash160::Hash as Hash160;
+use bitcoin_hashes::sha256d::Hash as Sha256dHash;
+
+use ln::channelmanager::PaymentHash;
+
+use secp256k1::key::{PublicKey,SecretKey};
+use secp256k1::Secp256k1;
+use secp256k1;
+
+pub const HTLC_SUCCESS_TX_WEIGHT: u64 = 703;
+pub const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663;
+
+// Various functions for key derivation and transaction creation for use within channels. Primarily
+// used in Channel and ChannelMonitor.
+
+pub fn build_commitment_secret(commitment_seed: [u8; 32], idx: u64) -> [u8; 32] {
+ let mut res: [u8; 32] = commitment_seed;
+ for i in 0..48 {
+ let bitpos = 47 - i;
+ if idx & (1 << bitpos) == (1 << bitpos) {
+ res[bitpos / 8] ^= 1 << (bitpos & 7);
+ res = Sha256::hash(&res).into_inner();
+ }
+ }
+ res
+}
+
+pub fn derive_private_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
+ let mut sha = Sha256::engine();
+ sha.input(&per_commitment_point.serialize());
+ 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)
+}
+
+pub fn derive_public_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result<PublicKey, secp256k1::Error> {
+ let mut sha = Sha256::engine();
+ sha.input(&per_commitment_point.serialize());
+ sha.input(&base_point.serialize());
+ let res = Sha256::from_engine(sha).into_inner();
+
+ let hashkey = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&res)?);
+ base_point.combine(&hashkey)
+}
+
+/// Derives a revocation key from its constituent parts
+pub fn derive_private_revocation_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_secret: &SecretKey, revocation_base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
+ let revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &revocation_base_secret);
+ let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);
+
+ let rev_append_commit_hash_key = {
+ let mut sha = Sha256::engine();
+ sha.input(&revocation_base_point.serialize());
+ sha.input(&per_commitment_point.serialize());
+
+ Sha256::from_engine(sha).into_inner()
+ };
+ let commit_append_rev_hash_key = {
+ let mut sha = Sha256::engine();
+ sha.input(&per_commitment_point.serialize());
+ sha.input(&revocation_base_point.serialize());
+
+ Sha256::from_engine(sha).into_inner()
+ };
+
+ let mut part_a = revocation_base_secret.clone();
+ part_a.mul_assign(&rev_append_commit_hash_key)?;
+ let mut part_b = per_commitment_secret.clone();
+ part_b.mul_assign(&commit_append_rev_hash_key)?;
+ part_a.add_assign(&part_b[..])?;
+ Ok(part_a)
+}
+
+pub fn derive_public_revocation_key<T: secp256k1::Verification>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, revocation_base_point: &PublicKey) -> Result<PublicKey, secp256k1::Error> {
+ let rev_append_commit_hash_key = {
+ let mut sha = Sha256::engine();
+ sha.input(&revocation_base_point.serialize());
+ sha.input(&per_commitment_point.serialize());
+
+ Sha256::from_engine(sha).into_inner()
+ };
+ let commit_append_rev_hash_key = {
+ let mut sha = Sha256::engine();
+ sha.input(&per_commitment_point.serialize());
+ sha.input(&revocation_base_point.serialize());
+
+ Sha256::from_engine(sha).into_inner()
+ };
+
+ let mut part_a = revocation_base_point.clone();
+ part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
+ let mut part_b = per_commitment_point.clone();
+ part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
+ part_a.combine(&part_b)
+}
+
+pub struct TxCreationKeys {
+ pub per_commitment_point: PublicKey,
+ pub revocation_key: PublicKey,
+ pub a_htlc_key: PublicKey,
+ pub b_htlc_key: PublicKey,
+ pub a_delayed_payment_key: PublicKey,
+ pub b_payment_key: PublicKey,
+}
+
+impl TxCreationKeys {
+ pub fn new<T: secp256k1::Signing + secp256k1::Verification>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, a_delayed_payment_base: &PublicKey, a_htlc_base: &PublicKey, b_revocation_base: &PublicKey, b_payment_base: &PublicKey, b_htlc_base: &PublicKey) -> Result<TxCreationKeys, secp256k1::Error> {
+ Ok(TxCreationKeys {
+ per_commitment_point: per_commitment_point.clone(),
+ revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &b_revocation_base)?,
+ a_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_htlc_base)?,
+ b_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_htlc_base)?,
+ a_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_delayed_payment_base)?,
+ b_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_payment_base)?,
+ })
+ }
+}
+
+/// Gets the "to_local" output redeemscript, ie the script which is time-locked or spendable by
+/// the revocation key
+pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, to_self_delay: u16, delayed_payment_key: &PublicKey) -> Script {
+ Builder::new().push_opcode(opcodes::all::OP_IF)
+ .push_slice(&revocation_key.serialize())
+ .push_opcode(opcodes::all::OP_ELSE)
+ .push_int(to_self_delay as i64)
+ .push_opcode(opcodes::all::OP_CSV)
+ .push_opcode(opcodes::all::OP_DROP)
+ .push_slice(&delayed_payment_key.serialize())
+ .push_opcode(opcodes::all::OP_ENDIF)
+ .push_opcode(opcodes::all::OP_CHECKSIG)
+ .into_script()
+}
+
+#[derive(Clone, PartialEq)]
+pub struct HTLCOutputInCommitment {
+ pub offered: bool,
+ pub amount_msat: u64,
+ pub cltv_expiry: u32,
+ pub payment_hash: PaymentHash,
+ pub transaction_output_index: Option<u32>,
+}
+
+#[inline]
+pub fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, a_htlc_key: &PublicKey, b_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script {
+ let payment_hash160 = Ripemd160::hash(&htlc.payment_hash.0[..]).into_inner();
+ if htlc.offered {
+ Builder::new().push_opcode(opcodes::all::OP_DUP)
+ .push_opcode(opcodes::all::OP_HASH160)
+ .push_slice(&Hash160::hash(&revocation_key.serialize())[..])
+ .push_opcode(opcodes::all::OP_EQUAL)
+ .push_opcode(opcodes::all::OP_IF)
+ .push_opcode(opcodes::all::OP_CHECKSIG)
+ .push_opcode(opcodes::all::OP_ELSE)
+ .push_slice(&b_htlc_key.serialize()[..])
+ .push_opcode(opcodes::all::OP_SWAP)
+ .push_opcode(opcodes::all::OP_SIZE)
+ .push_int(32)
+ .push_opcode(opcodes::all::OP_EQUAL)
+ .push_opcode(opcodes::all::OP_NOTIF)
+ .push_opcode(opcodes::all::OP_DROP)
+ .push_int(2)
+ .push_opcode(opcodes::all::OP_SWAP)
+ .push_slice(&a_htlc_key.serialize()[..])
+ .push_int(2)
+ .push_opcode(opcodes::all::OP_CHECKMULTISIG)
+ .push_opcode(opcodes::all::OP_ELSE)
+ .push_opcode(opcodes::all::OP_HASH160)
+ .push_slice(&payment_hash160)
+ .push_opcode(opcodes::all::OP_EQUALVERIFY)
+ .push_opcode(opcodes::all::OP_CHECKSIG)
+ .push_opcode(opcodes::all::OP_ENDIF)
+ .push_opcode(opcodes::all::OP_ENDIF)
+ .into_script()
+ } else {
+ Builder::new().push_opcode(opcodes::all::OP_DUP)
+ .push_opcode(opcodes::all::OP_HASH160)
+ .push_slice(&Hash160::hash(&revocation_key.serialize())[..])
+ .push_opcode(opcodes::all::OP_EQUAL)
+ .push_opcode(opcodes::all::OP_IF)
+ .push_opcode(opcodes::all::OP_CHECKSIG)
+ .push_opcode(opcodes::all::OP_ELSE)
+ .push_slice(&b_htlc_key.serialize()[..])
+ .push_opcode(opcodes::all::OP_SWAP)
+ .push_opcode(opcodes::all::OP_SIZE)
+ .push_int(32)
+ .push_opcode(opcodes::all::OP_EQUAL)
+ .push_opcode(opcodes::all::OP_IF)
+ .push_opcode(opcodes::all::OP_HASH160)
+ .push_slice(&payment_hash160)
+ .push_opcode(opcodes::all::OP_EQUALVERIFY)
+ .push_int(2)
+ .push_opcode(opcodes::all::OP_SWAP)
+ .push_slice(&a_htlc_key.serialize()[..])
+ .push_int(2)
+ .push_opcode(opcodes::all::OP_CHECKMULTISIG)
+ .push_opcode(opcodes::all::OP_ELSE)
+ .push_opcode(opcodes::all::OP_DROP)
+ .push_int(htlc.cltv_expiry as i64)
+ .push_opcode(opcodes::all::OP_CLTV)
+ .push_opcode(opcodes::all::OP_DROP)
+ .push_opcode(opcodes::all::OP_CHECKSIG)
+ .push_opcode(opcodes::all::OP_ENDIF)
+ .push_opcode(opcodes::all::OP_ENDIF)
+ .into_script()
+ }
+}
+
+/// note here that 'a_revocation_key' is generated using b_revocation_basepoint and a's
+/// commitment secret. 'htlc' does *not* need to have its previous_output_index filled.
+#[inline]
+pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Script {
+ get_htlc_redeemscript_with_explicit_keys(htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key)
+}
+
+/// panics if htlc.transaction_output_index.is_none()!
+pub fn build_htlc_transaction(prev_hash: &Sha256dHash, feerate_per_kw: u64, to_self_delay: u16, htlc: &HTLCOutputInCommitment, a_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
+ let mut txins: Vec<TxIn> = Vec::new();
+ txins.push(TxIn {
+ previous_output: OutPoint {
+ txid: prev_hash.clone(),
+ vout: htlc.transaction_output_index.expect("Can't build an HTLC transaction for a dust output"),
+ },
+ script_sig: Script::new(),
+ sequence: 0,
+ witness: Vec::new(),
+ });
+
+ let total_fee = if htlc.offered {
+ feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
+ } else {
+ feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000
+ };
+
+ let mut txouts: Vec<TxOut> = Vec::new();
+ txouts.push(TxOut {
+ script_pubkey: get_revokeable_redeemscript(revocation_key, to_self_delay, a_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)
+ });
+
+ Transaction {
+ version: 2,
+ lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
+ input: txins,
+ output: txouts,
+ }
+}
projects / rust-lightning / blobdiff