_ Git - rust-lightning/blob - src/chain/keysinterface.rs

   1 //! keysinterface provides keys into rust-lightning and defines some useful enums which describe
   2 //! spendable on-chain outputs which the user owns and is responsible for using just as any other
   3 //! on-chain output which is theirs.
   4
   5 use bitcoin::blockdata::transaction::{OutPoint, TxOut};
   6 use bitcoin::blockdata::script::{Script, Builder};
   7 use bitcoin::blockdata::opcodes;
   8 use bitcoin::network::constants::Network;
   9 use bitcoin::util::hash::Hash160;
  10 use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber};
  11
  12 use secp256k1::key::{SecretKey, PublicKey};
  13 use secp256k1::Secp256k1;
  14 use secp256k1;
  15
  16 use crypto::hkdf::{hkdf_extract,hkdf_expand};
  17 use crypto::digest::Digest;
  18
  19 use util::sha2::Sha256;
  20 use util::logger::Logger;
  21 use util::rng;
  22 use util::byte_utils;
  23
  24 use std::time::{SystemTime, UNIX_EPOCH};
  25 use std::sync::Arc;
  26 use std::sync::atomic::{AtomicUsize, Ordering};
  27
  28 /// When on-chain outputs are created by rust-lightning an event is generated which informs the
  29 /// user thereof. This enum describes the format of the output and provides the OutPoint.
  30 pub enum SpendableOutputDescriptor {
  31         /// Outpoint with an output to a script which was provided via KeysInterface, thus you should
  32         /// have stored somewhere how to spend script_pubkey!
  33         /// Outputs from a justice tx, claim tx or preimage tx
  34         StaticOutput {
  35                 /// The outpoint spendable by user wallet
  36                 outpoint: OutPoint,
  37                 /// The output which is referenced by the given outpoint
  38                 output: TxOut,
  39         },
  40         /// Outpoint commits to a P2WSH
  41         /// P2WSH should be spend by the following witness :
  42         /// <local_delayedsig> 0 <witnessScript>
  43         /// With input nSequence set to_self_delay.
  44         /// Outputs from a HTLC-Success/Timeout tx/commitment tx
  45         DynamicOutputP2WSH {
  46                 /// Outpoint spendable by user wallet
  47                 outpoint: OutPoint,
  48                 /// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint) OR
  49                 key: SecretKey,
  50                 /// witness redeemScript encumbering output.
  51                 witness_script: Script,
  52                 /// nSequence input must commit to self_delay to satisfy script's OP_CSV
  53                 to_self_delay: u16,
  54                 /// The output which is referenced by the given outpoint
  55                 output: TxOut,
  56         },
  57         /// Outpoint commits to a P2WPKH
  58         /// P2WPKH should be spend by the following witness :
  59         /// <local_sig> <local_pubkey>
  60         /// Outputs to_remote from a commitment tx
  61         DynamicOutputP2WPKH {
  62                 /// Outpoint spendable by user wallet
  63                 outpoint: OutPoint,
  64                 /// localkey = payment_basepoint_secret + SHA256(per_commitment_point || payment_basepoint
  65                 key: SecretKey,
  66                 /// The output which is reference by the given outpoint
  67                 output: TxOut,
  68         }
  69 }
  70
  71 /// A trait to describe an object which can get user secrets and key material.
  72 pub trait KeysInterface: Send + Sync {
  73         /// Get node secret key (aka node_id or network_key)
  74         fn get_node_secret(&self) -> SecretKey;
  75         /// Get destination redeemScript to encumber static protocol exit points.
  76         fn get_destination_script(&self) -> Script;
  77         /// Get shutdown_pubkey to use as PublicKey at channel closure
  78         fn get_shutdown_pubkey(&self) -> PublicKey;
  79         /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you
  80         /// restarted with some stale data!
  81         fn get_channel_keys(&self, inbound: bool) -> ChannelKeys;
  82 }
  83
  84 /// Set of lightning keys needed to operate a channel as described in BOLT 3
  85 #[derive(Clone)]
  86 pub struct ChannelKeys {
  87         /// Private key of anchor tx
  88         pub funding_key: SecretKey,
  89         /// Local secret key for blinded revocation pubkey
  90         pub revocation_base_key: SecretKey,
  91         /// Local secret key used in commitment tx htlc outputs
  92         pub payment_base_key: SecretKey,
  93         /// Local secret key used in HTLC tx
  94         pub delayed_payment_base_key: SecretKey,
  95         /// Local htlc secret key used in commitment tx htlc outputs
  96         pub htlc_base_key: SecretKey,
  97         /// Commitment seed
  98         pub commitment_seed: [u8; 32],
  99 }
 100
 101 impl_writeable!(ChannelKeys, 0, {
 102         funding_key,
 103         revocation_base_key,
 104         payment_base_key,
 105         delayed_payment_base_key,
 106         htlc_base_key,
 107         commitment_seed
 108 });
 109
 110 impl ChannelKeys {
 111         /// Generate a set of lightning keys needed to operate a channel by HKDF-expanding a given
 112         /// random 32-byte seed
 113         pub fn new_from_seed(seed: &[u8; 32]) -> ChannelKeys {
 114                 let mut prk = [0; 32];
 115                 hkdf_extract(Sha256::new(), b"rust-lightning key gen salt", seed, &mut prk);
 116                 let secp_ctx = Secp256k1::without_caps();
 117
 118                 let mut okm = [0; 32];
 119                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning funding key info", &mut okm);
 120                 let funding_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 121
 122                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning revocation base key info", &mut okm);
 123                 let revocation_base_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 124
 125                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning payment base key info", &mut okm);
 126                 let payment_base_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 127
 128                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning delayed payment base key info", &mut okm);
 129                 let delayed_payment_base_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 130
 131                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning htlc base key info", &mut okm);
 132                 let htlc_base_key = SecretKey::from_slice(&secp_ctx, &okm).expect("Sha256 is broken");
 133
 134                 hkdf_expand(Sha256::new(), &prk, b"rust-lightning local commitment seed info", &mut okm);
 135
 136                 ChannelKeys {
 137                         funding_key: funding_key,
 138                         revocation_base_key: revocation_base_key,
 139                         payment_base_key: payment_base_key,
 140                         delayed_payment_base_key: delayed_payment_base_key,
 141                         htlc_base_key: htlc_base_key,
 142                         commitment_seed: okm
 143                 }
 144         }
 145 }
 146
 147 /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key
 148 /// and derives keys from that.
 149 ///
 150 /// Your node_id is seed/0'
 151 /// ChannelMonitor closes may use seed/1'
 152 /// Cooperative closes may use seed/2'
 153 /// The two close keys may be needed to claim on-chain funds!
 154 pub struct KeysManager {
 155         secp_ctx: Secp256k1<secp256k1::All>,
 156         node_secret: SecretKey,
 157         destination_script: Script,
 158         shutdown_pubkey: PublicKey,
 159         channel_master_key: ExtendedPrivKey,
 160         channel_child_index: AtomicUsize,
 161
 162         logger: Arc<Logger>,
 163 }
 164
 165 impl KeysManager {
 166         /// Constructs a KeysManager from a 32-byte seed. If the seed is in some way biased (eg your
 167         /// RNG is busted) this may panic.
 168         pub fn new(seed: &[u8; 32], network: Network, logger: Arc<Logger>) -> KeysManager {
 169                 let secp_ctx = Secp256k1::new();
 170                 match ExtendedPrivKey::new_master(&secp_ctx, network.clone(), seed) {
 171                         Ok(master_key) => {
 172                                 let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0)).expect("Your RNG is busted").secret_key;
 173                                 let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1)) {
 174                                         Ok(destination_key) => {
 175                                                 let pubkey_hash160 = Hash160::from_data(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.serialize()[..]);
 176                                                 Builder::new().push_opcode(opcodes::All::OP_PUSHBYTES_0)
 177                                                               .push_slice(pubkey_hash160.as_bytes())
 178                                                               .into_script()
 179                                         },
 180                                         Err(_) => panic!("Your RNG is busted"),
 181                                 };
 182                                 let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2)) {
 183                                         Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key,
 184                                         Err(_) => panic!("Your RNG is busted"),
 185                                 };
 186                                 let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3)).expect("Your RNG is busted");
 187                                 KeysManager {
 188                                         secp_ctx,
 189                                         node_secret,
 190                                         destination_script,
 191                                         shutdown_pubkey,
 192                                         channel_master_key,
 193                                         channel_child_index: AtomicUsize::new(0),
 194
 195                                         logger,
 196                                 }
 197                         },
 198                         Err(_) => panic!("Your rng is busted"),
 199                 }
 200         }
 201 }
 202
 203 impl KeysInterface for KeysManager {
 204         fn get_node_secret(&self) -> SecretKey {
 205                 self.node_secret.clone()
 206         }
 207
 208         fn get_destination_script(&self) -> Script {
 209                 self.destination_script.clone()
 210         }
 211
 212         fn get_shutdown_pubkey(&self) -> PublicKey {
 213                 self.shutdown_pubkey.clone()
 214         }
 215
 216         fn get_channel_keys(&self, _inbound: bool) -> ChannelKeys {
 217                 // We only seriously intend to rely on the channel_master_key for true secure
 218                 // entropy, everything else just ensures uniqueness. We generally don't expect
 219                 // all clients to have non-broken RNGs here, so we also include the current
 220                 // time as a fallback to get uniqueness.
 221                 let mut sha = Sha256::new();
 222
 223                 let mut seed = [0u8; 32];
 224                 rng::fill_bytes(&mut seed[..]);
 225                 sha.input(&seed);
 226
 227                 let now = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time went backwards");
 228                 sha.input(&byte_utils::be32_to_array(now.subsec_nanos()));
 229                 sha.input(&byte_utils::be64_to_array(now.as_secs()));
 230
 231                 let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
 232                 let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32)).expect("Your RNG is busted");
 233                 sha.input(&child_privkey.secret_key[..]);
 234
 235                 sha.result(&mut seed);
 236                 ChannelKeys::new_from_seed(&seed)
 237         }
 238 }