_ Git - rust-lightning/blob - src/ln/chan_utils.rs

   1 use bitcoin::blockdata::script::{Script,Builder};
   2 use bitcoin::blockdata::opcodes;
   3 use bitcoin::blockdata::transaction::{TxIn,TxOut,OutPoint,Transaction};
   4 use bitcoin::util::hash::{Hash160,Sha256dHash};
   5
   6 use bitcoin_hashes::{Hash, HashEngine};
   7 use bitcoin_hashes::sha256::Hash as Sha256;
   8
   9 use ln::channelmanager::PaymentHash;
  10
  11 use secp256k1::key::{PublicKey,SecretKey};
  12 use secp256k1::Secp256k1;
  13 use secp256k1;
  14
  15 use crypto::digest::Digest;
  16 use crypto::ripemd160::Ripemd160;
  17
  18 pub const HTLC_SUCCESS_TX_WEIGHT: u64 = 703;
  19 pub const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663;
  20
  21 // Various functions for key derivation and transaction creation for use within channels. Primarily
  22 // used in Channel and ChannelMonitor.
  23
  24 pub fn build_commitment_secret(commitment_seed: [u8; 32], idx: u64) -> [u8; 32] {
  25         let mut res: [u8; 32] = commitment_seed;
  26         for i in 0..48 {
  27                 let bitpos = 47 - i;
  28                 if idx & (1 << bitpos) == (1 << bitpos) {
  29                         res[bitpos / 8] ^= 1 << (bitpos & 7);
  30                         res = Sha256::hash(&res).into_inner();
  31                 }
  32         }
  33         res
  34 }
  35
  36 pub fn derive_private_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
  37         let mut sha = Sha256::engine();
  38         sha.input(&per_commitment_point.serialize());
  39         sha.input(&PublicKey::from_secret_key(&secp_ctx, &base_secret).serialize());
  40         let res = Sha256::from_engine(sha).into_inner();
  41
  42         let mut key = base_secret.clone();
  43         key.add_assign(&secp_ctx, &SecretKey::from_slice(&secp_ctx, &res)?)?;
  44         Ok(key)
  45 }
  46
  47 pub fn derive_public_key<T: secp256k1::Signing>(secp_ctx: &Secp256k1<T>, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result<PublicKey, secp256k1::Error> {
  48         let mut sha = Sha256::engine();
  49         sha.input(&per_commitment_point.serialize());
  50         sha.input(&base_point.serialize());
  51         let res = Sha256::from_engine(sha).into_inner();
  52
  53         let hashkey = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&secp_ctx, &res)?);
  54         base_point.combine(&secp_ctx, &hashkey)
  55 }
  56
  57 /// Derives a revocation key from its constituent parts
  58 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> {
  59         let revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &revocation_base_secret);
  60         let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret);
  61
  62         let rev_append_commit_hash_key = {
  63                 let mut sha = Sha256::engine();
  64                 sha.input(&revocation_base_point.serialize());
  65                 sha.input(&per_commitment_point.serialize());
  66
  67                 SecretKey::from_slice(&secp_ctx, &Sha256::from_engine(sha).into_inner())?
  68         };
  69         let commit_append_rev_hash_key = {
  70                 let mut sha = Sha256::engine();
  71                 sha.input(&per_commitment_point.serialize());
  72                 sha.input(&revocation_base_point.serialize());
  73
  74                 SecretKey::from_slice(&secp_ctx, &Sha256::from_engine(sha).into_inner())?
  75         };
  76
  77         let mut part_a = revocation_base_secret.clone();
  78         part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
  79         let mut part_b = per_commitment_secret.clone();
  80         part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
  81         part_a.add_assign(&secp_ctx, &part_b)?;
  82         Ok(part_a)
  83 }
  84
  85 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> {
  86         let rev_append_commit_hash_key = {
  87                 let mut sha = Sha256::engine();
  88                 sha.input(&revocation_base_point.serialize());
  89                 sha.input(&per_commitment_point.serialize());
  90
  91                 SecretKey::from_slice(&secp_ctx, &Sha256::from_engine(sha).into_inner())?
  92         };
  93         let commit_append_rev_hash_key = {
  94                 let mut sha = Sha256::engine();
  95                 sha.input(&per_commitment_point.serialize());
  96                 sha.input(&revocation_base_point.serialize());
  97
  98                 SecretKey::from_slice(&secp_ctx, &Sha256::from_engine(sha).into_inner())?
  99         };
 100
 101         let mut part_a = revocation_base_point.clone();
 102         part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
 103         let mut part_b = per_commitment_point.clone();
 104         part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
 105         part_a.combine(&secp_ctx, &part_b)
 106 }
 107
 108 pub struct TxCreationKeys {
 109         pub per_commitment_point: PublicKey,
 110         pub revocation_key: PublicKey,
 111         pub a_htlc_key: PublicKey,
 112         pub b_htlc_key: PublicKey,
 113         pub a_delayed_payment_key: PublicKey,
 114         pub b_payment_key: PublicKey,
 115 }
 116
 117 impl TxCreationKeys {
 118         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> {
 119                 Ok(TxCreationKeys {
 120                         per_commitment_point: per_commitment_point.clone(),
 121                         revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &b_revocation_base)?,
 122                         a_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_htlc_base)?,
 123                         b_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_htlc_base)?,
 124                         a_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_delayed_payment_base)?,
 125                         b_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_payment_base)?,
 126                 })
 127         }
 128 }
 129
 130 /// Gets the "to_local" output redeemscript, ie the script which is time-locked or spendable by
 131 /// the revocation key
 132 pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, to_self_delay: u16, delayed_payment_key: &PublicKey) -> Script {
 133         Builder::new().push_opcode(opcodes::All::OP_IF)
 134                       .push_slice(&revocation_key.serialize())
 135                       .push_opcode(opcodes::All::OP_ELSE)
 136                       .push_int(to_self_delay as i64)
 137                       .push_opcode(opcodes::OP_CSV)
 138                       .push_opcode(opcodes::All::OP_DROP)
 139                       .push_slice(&delayed_payment_key.serialize())
 140                       .push_opcode(opcodes::All::OP_ENDIF)
 141                       .push_opcode(opcodes::All::OP_CHECKSIG)
 142                       .into_script()
 143 }
 144
 145 #[derive(Clone, PartialEq)]
 146 pub struct HTLCOutputInCommitment {
 147         pub offered: bool,
 148         pub amount_msat: u64,
 149         pub cltv_expiry: u32,
 150         pub payment_hash: PaymentHash,
 151         pub transaction_output_index: u32,
 152 }
 153
 154 #[inline]
 155 pub fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, a_htlc_key: &PublicKey, b_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script {
 156         let payment_hash160 = {
 157                 let mut ripemd = Ripemd160::new();
 158                 ripemd.input(&htlc.payment_hash.0[..]);
 159                 let mut res = [0; 20];
 160                 ripemd.result(&mut res);
 161                 res
 162         };
 163         if htlc.offered {
 164                 Builder::new().push_opcode(opcodes::All::OP_DUP)
 165                               .push_opcode(opcodes::All::OP_HASH160)
 166                               .push_slice(&Hash160::from_data(&revocation_key.serialize())[..])
 167                               .push_opcode(opcodes::All::OP_EQUAL)
 168                               .push_opcode(opcodes::All::OP_IF)
 169                               .push_opcode(opcodes::All::OP_CHECKSIG)
 170                               .push_opcode(opcodes::All::OP_ELSE)
 171                               .push_slice(&b_htlc_key.serialize()[..])
 172                               .push_opcode(opcodes::All::OP_SWAP)
 173                               .push_opcode(opcodes::All::OP_SIZE)
 174                               .push_int(32)
 175                               .push_opcode(opcodes::All::OP_EQUAL)
 176                               .push_opcode(opcodes::All::OP_NOTIF)
 177                               .push_opcode(opcodes::All::OP_DROP)
 178                               .push_int(2)
 179                               .push_opcode(opcodes::All::OP_SWAP)
 180                               .push_slice(&a_htlc_key.serialize()[..])
 181                               .push_int(2)
 182                               .push_opcode(opcodes::All::OP_CHECKMULTISIG)
 183                               .push_opcode(opcodes::All::OP_ELSE)
 184                               .push_opcode(opcodes::All::OP_HASH160)
 185                               .push_slice(&payment_hash160)
 186                               .push_opcode(opcodes::All::OP_EQUALVERIFY)
 187                               .push_opcode(opcodes::All::OP_CHECKSIG)
 188                               .push_opcode(opcodes::All::OP_ENDIF)
 189                               .push_opcode(opcodes::All::OP_ENDIF)
 190                               .into_script()
 191         } else {
 192                 Builder::new().push_opcode(opcodes::All::OP_DUP)
 193                               .push_opcode(opcodes::All::OP_HASH160)
 194                               .push_slice(&Hash160::from_data(&revocation_key.serialize())[..])
 195                               .push_opcode(opcodes::All::OP_EQUAL)
 196                               .push_opcode(opcodes::All::OP_IF)
 197                               .push_opcode(opcodes::All::OP_CHECKSIG)
 198                               .push_opcode(opcodes::All::OP_ELSE)
 199                               .push_slice(&b_htlc_key.serialize()[..])
 200                               .push_opcode(opcodes::All::OP_SWAP)
 201                               .push_opcode(opcodes::All::OP_SIZE)
 202                               .push_int(32)
 203                               .push_opcode(opcodes::All::OP_EQUAL)
 204                               .push_opcode(opcodes::All::OP_IF)
 205                               .push_opcode(opcodes::All::OP_HASH160)
 206                               .push_slice(&payment_hash160)
 207                               .push_opcode(opcodes::All::OP_EQUALVERIFY)
 208                               .push_int(2)
 209                               .push_opcode(opcodes::All::OP_SWAP)
 210                               .push_slice(&a_htlc_key.serialize()[..])
 211                               .push_int(2)
 212                               .push_opcode(opcodes::All::OP_CHECKMULTISIG)
 213                               .push_opcode(opcodes::All::OP_ELSE)
 214                               .push_opcode(opcodes::All::OP_DROP)
 215                               .push_int(htlc.cltv_expiry as i64)
 216                               .push_opcode(opcodes::OP_CLTV)
 217                               .push_opcode(opcodes::All::OP_DROP)
 218                               .push_opcode(opcodes::All::OP_CHECKSIG)
 219                               .push_opcode(opcodes::All::OP_ENDIF)
 220                               .push_opcode(opcodes::All::OP_ENDIF)
 221                               .into_script()
 222         }
 223 }
 224
 225 /// note here that 'a_revocation_key' is generated using b_revocation_basepoint and a's
 226 /// commitment secret. 'htlc' does *not* need to have its previous_output_index filled.
 227 #[inline]
 228 pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Script {
 229         get_htlc_redeemscript_with_explicit_keys(htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key)
 230 }
 231
 232 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 {
 233         let mut txins: Vec<TxIn> = Vec::new();
 234         txins.push(TxIn {
 235                 previous_output: OutPoint {
 236                         txid: prev_hash.clone(),
 237                         vout: htlc.transaction_output_index,
 238                 },
 239                 script_sig: Script::new(),
 240                 sequence: 0,
 241                 witness: Vec::new(),
 242         });
 243
 244         let total_fee = if htlc.offered {
 245                         feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
 246                 } else {
 247                         feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000
 248                 };
 249
 250         let mut txouts: Vec<TxOut> = Vec::new();
 251         txouts.push(TxOut {
 252                 script_pubkey: get_revokeable_redeemscript(revocation_key, to_self_delay, a_delayed_payment_key).to_v0_p2wsh(),
 253                 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)
 254         });
 255
 256         Transaction {
 257                 version: 2,
 258                 lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
 259                 input: txins,
 260                 output: txouts,
 261         }
 262 }