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