git.bitcoin.ninja 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,Transaction};
   4 use bitcoin::util::hash::{Hash160,Sha256dHash};
   5
   6 use secp256k1::key::{PublicKey,SecretKey};
   7 use secp256k1::Secp256k1;
   8 use secp256k1;
   9
  10 use crypto::digest::Digest;
  11 use crypto::ripemd160::Ripemd160;
  12
  13 use util::sha2::Sha256;
  14
  15 pub const HTLC_SUCCESS_TX_WEIGHT: u64 = 703;
  16 pub const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663;
  17
  18 // Various functions for key derivation and transaction creation for use within channels. Primarily
  19 // used in Channel and ChannelMonitor.
  20
  21 pub fn build_commitment_secret(commitment_seed: [u8; 32], idx: u64) -> [u8; 32] {
  22         let mut res: [u8; 32] = commitment_seed;
  23         for i in 0..48 {
  24                 let bitpos = 47 - i;
  25                 if idx & (1 << bitpos) == (1 << bitpos) {
  26                         res[bitpos / 8] ^= 1 << (bitpos & 7);
  27                         let mut sha = Sha256::new();
  28                         sha.input(&res);
  29                         sha.result(&mut res);
  30                 }
  31         }
  32         res
  33 }
  34
  35 pub fn derive_private_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
  36         let mut sha = Sha256::new();
  37         sha.input(&per_commitment_point.serialize());
  38         sha.input(&PublicKey::from_secret_key(&secp_ctx, &base_secret).unwrap().serialize());
  39         let mut res = [0; 32];
  40         sha.result(&mut res);
  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(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result<PublicKey, secp256k1::Error> {
  48         let mut sha = Sha256::new();
  49         sha.input(&per_commitment_point.serialize());
  50         sha.input(&base_point.serialize());
  51         let mut res = [0; 32];
  52         sha.result(&mut res);
  53
  54         let hashkey = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&secp_ctx, &res)?).unwrap();
  55         base_point.combine(&secp_ctx, &hashkey)
  56 }
  57
  58 /// Derives a revocation key from its constituent parts
  59 pub fn derive_private_revocation_key(secp_ctx: &Secp256k1, per_commitment_secret: &SecretKey, revocation_base_secret: &SecretKey) -> Result<SecretKey, secp256k1::Error> {
  60         let revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &revocation_base_secret).unwrap();
  61         let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret).unwrap();
  62
  63         let rev_append_commit_hash_key = {
  64                 let mut sha = Sha256::new();
  65                 sha.input(&revocation_base_point.serialize());
  66                 sha.input(&per_commitment_point.serialize());
  67                 let mut res = [0; 32];
  68                 sha.result(&mut res);
  69
  70                 SecretKey::from_slice(&secp_ctx, &res)?
  71         };
  72         let commit_append_rev_hash_key = {
  73                 let mut sha = Sha256::new();
  74                 sha.input(&per_commitment_point.serialize());
  75                 sha.input(&revocation_base_point.serialize());
  76                 let mut res = [0; 32];
  77                 sha.result(&mut res);
  78
  79                 SecretKey::from_slice(&secp_ctx, &res)?
  80         };
  81
  82         let mut part_a = revocation_base_secret.clone();
  83         part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
  84         let mut part_b = per_commitment_secret.clone();
  85         part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
  86         part_a.add_assign(&secp_ctx, &part_b)?;
  87         Ok(part_a)
  88 }
  89
  90 pub fn derive_public_revocation_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, revocation_base_point: &PublicKey) -> Result<PublicKey, secp256k1::Error> {
  91         let rev_append_commit_hash_key = {
  92                 let mut sha = Sha256::new();
  93                 sha.input(&revocation_base_point.serialize());
  94                 sha.input(&per_commitment_point.serialize());
  95                 let mut res = [0; 32];
  96                 sha.result(&mut res);
  97
  98                 SecretKey::from_slice(&secp_ctx, &res)?
  99         };
 100         let commit_append_rev_hash_key = {
 101                 let mut sha = Sha256::new();
 102                 sha.input(&per_commitment_point.serialize());
 103                 sha.input(&revocation_base_point.serialize());
 104                 let mut res = [0; 32];
 105                 sha.result(&mut res);
 106
 107                 SecretKey::from_slice(&secp_ctx, &res)?
 108         };
 109
 110         let mut part_a = revocation_base_point.clone();
 111         part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?;
 112         let mut part_b = per_commitment_point.clone();
 113         part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?;
 114         part_a.combine(&secp_ctx, &part_b)
 115 }
 116
 117 pub struct TxCreationKeys {
 118         pub per_commitment_point: PublicKey,
 119         pub revocation_key: PublicKey,
 120         pub a_htlc_key: PublicKey,
 121         pub b_htlc_key: PublicKey,
 122         pub a_delayed_payment_key: PublicKey,
 123         pub b_payment_key: PublicKey,
 124 }
 125
 126 impl TxCreationKeys {
 127         pub fn new(secp_ctx: &Secp256k1, 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> {
 128                 Ok(TxCreationKeys {
 129                         per_commitment_point: per_commitment_point.clone(),
 130                         revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &b_revocation_base)?,
 131                         a_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_htlc_base)?,
 132                         b_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_htlc_base)?,
 133                         a_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_delayed_payment_base)?,
 134                         b_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_payment_base)?,
 135                 })
 136         }
 137 }
 138
 139 /// Gets the "to_local" output redeemscript, ie the script which is time-locked or spendable by
 140 /// the revocation key
 141 pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, to_self_delay: u16, delayed_payment_key: &PublicKey) -> Script {
 142         Builder::new().push_opcode(opcodes::All::OP_IF)
 143                                      .push_slice(&revocation_key.serialize())
 144                                      .push_opcode(opcodes::All::OP_ELSE)
 145                                      .push_int(to_self_delay as i64)
 146                                      .push_opcode(opcodes::OP_CSV)
 147                                      .push_opcode(opcodes::All::OP_DROP)
 148                                      .push_slice(&delayed_payment_key.serialize())
 149                                      .push_opcode(opcodes::All::OP_ENDIF)
 150                                      .push_opcode(opcodes::All::OP_CHECKSIG)
 151                                      .into_script()
 152 }
 153
 154 #[derive(Clone)]
 155 pub struct HTLCOutputInCommitment {
 156         pub offered: bool,
 157         pub amount_msat: u64,
 158         pub cltv_expiry: u32,
 159         pub payment_hash: [u8; 32],
 160         pub transaction_output_index: u32,
 161 }
 162
 163 #[inline]
 164 pub fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, a_htlc_key: &PublicKey, b_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script {
 165         let payment_hash160 = {
 166                 let mut ripemd = Ripemd160::new();
 167                 ripemd.input(&htlc.payment_hash);
 168                 let mut res = [0; 20];
 169                 ripemd.result(&mut res);
 170                 res
 171         };
 172         if htlc.offered {
 173                 Builder::new().push_opcode(opcodes::All::OP_DUP)
 174                               .push_opcode(opcodes::All::OP_HASH160)
 175                               .push_slice(&Hash160::from_data(&revocation_key.serialize())[..])
 176                               .push_opcode(opcodes::All::OP_EQUAL)
 177                               .push_opcode(opcodes::All::OP_IF)
 178                               .push_opcode(opcodes::All::OP_CHECKSIG)
 179                               .push_opcode(opcodes::All::OP_ELSE)
 180                               .push_slice(&b_htlc_key.serialize()[..])
 181                               .push_opcode(opcodes::All::OP_SWAP)
 182                               .push_opcode(opcodes::All::OP_SIZE)
 183                               .push_int(32)
 184                               .push_opcode(opcodes::All::OP_EQUAL)
 185                               .push_opcode(opcodes::All::OP_NOTIF)
 186                               .push_opcode(opcodes::All::OP_DROP)
 187                               .push_int(2)
 188                               .push_opcode(opcodes::All::OP_SWAP)
 189                               .push_slice(&a_htlc_key.serialize()[..])
 190                               .push_int(2)
 191                               .push_opcode(opcodes::All::OP_CHECKMULTISIG)
 192                               .push_opcode(opcodes::All::OP_ELSE)
 193                               .push_opcode(opcodes::All::OP_HASH160)
 194                               .push_slice(&payment_hash160)
 195                               .push_opcode(opcodes::All::OP_EQUALVERIFY)
 196                               .push_opcode(opcodes::All::OP_CHECKSIG)
 197                               .push_opcode(opcodes::All::OP_ENDIF)
 198                               .push_opcode(opcodes::All::OP_ENDIF)
 199                               .into_script()
 200         } else {
 201                 Builder::new().push_opcode(opcodes::All::OP_DUP)
 202                               .push_opcode(opcodes::All::OP_HASH160)
 203                               .push_slice(&Hash160::from_data(&revocation_key.serialize())[..])
 204                               .push_opcode(opcodes::All::OP_EQUAL)
 205                               .push_opcode(opcodes::All::OP_IF)
 206                               .push_opcode(opcodes::All::OP_CHECKSIG)
 207                               .push_opcode(opcodes::All::OP_ELSE)
 208                               .push_slice(&b_htlc_key.serialize()[..])
 209                               .push_opcode(opcodes::All::OP_SWAP)
 210                               .push_opcode(opcodes::All::OP_SIZE)
 211                               .push_int(32)
 212                               .push_opcode(opcodes::All::OP_EQUAL)
 213                               .push_opcode(opcodes::All::OP_IF)
 214                               .push_opcode(opcodes::All::OP_HASH160)
 215                               .push_slice(&payment_hash160)
 216                               .push_opcode(opcodes::All::OP_EQUALVERIFY)
 217                               .push_int(2)
 218                               .push_opcode(opcodes::All::OP_SWAP)
 219                               .push_slice(&a_htlc_key.serialize()[..])
 220                               .push_int(2)
 221                               .push_opcode(opcodes::All::OP_CHECKMULTISIG)
 222                               .push_opcode(opcodes::All::OP_ELSE)
 223                               .push_opcode(opcodes::All::OP_DROP)
 224                               .push_int(htlc.cltv_expiry as i64)
 225                               .push_opcode(opcodes::OP_CLTV)
 226                               .push_opcode(opcodes::All::OP_DROP)
 227                               .push_opcode(opcodes::All::OP_CHECKSIG)
 228                               .push_opcode(opcodes::All::OP_ENDIF)
 229                               .push_opcode(opcodes::All::OP_ENDIF)
 230                               .into_script()
 231         }
 232 }
 233
 234 /// note here that 'a_revocation_key' is generated using b_revocation_basepoint and a's
 235 /// commitment secret. 'htlc' does *not* need to have its previous_output_index filled.
 236 #[inline]
 237 pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Script {
 238         get_htlc_redeemscript_with_explicit_keys(htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key)
 239 }
 240
 241 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 {
 242         let mut txins: Vec<TxIn> = Vec::new();
 243         txins.push(TxIn {
 244                 prev_hash: prev_hash.clone(),
 245                 prev_index: htlc.transaction_output_index,
 246                 script_sig: Script::new(),
 247                 sequence: 0,
 248                 witness: Vec::new(),
 249         });
 250
 251         let total_fee = if htlc.offered {
 252                         feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
 253                 } else {
 254                         feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000
 255                 };
 256
 257         let mut txouts: Vec<TxOut> = Vec::new();
 258         txouts.push(TxOut {
 259                 script_pubkey: get_revokeable_redeemscript(revocation_key, to_self_delay, a_delayed_payment_key).to_v0_p2wsh(),
 260                 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)
 261         });
 262
 263         Transaction {
 264                 version: 2,
 265                 lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
 266                 input: txins,
 267                 output: txouts,
 268         }
 269 }