_ Git - rust-lightning/blob - lightning/src/util/enforcing_trait_impls.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction};
  11 use ln::{chan_utils, msgs};
  12 use chain::keysinterface::{Sign, InMemorySigner, BaseSign};
  13
  14 use prelude::*;
  15 use core::cmp;
  16 use sync::{Mutex, Arc};
  17 #[cfg(test)] use sync::MutexGuard;
  18
  19 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
  20 use bitcoin::util::bip143;
  21
  22 use bitcoin::secp256k1;
  23 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
  24 use bitcoin::secp256k1::{Secp256k1, Signature};
  25 use util::ser::{Writeable, Writer};
  26 use io::Error;
  27
  28 /// Initial value for revoked commitment downward counter
  29 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
  30
  31 /// An implementation of Sign that enforces some policy checks.  The current checks
  32 /// are an incomplete set.  They include:
  33 ///
  34 /// - When signing, the holder transaction has not been revoked
  35 /// - When revoking, the holder transaction has not been signed
  36 /// - The holder commitment number is monotonic and without gaps
  37 /// - The revoked holder commitment number is monotonic and without gaps
  38 /// - There is at least one unrevoked holder transaction at all times
  39 /// - The counterparty commitment number is monotonic and without gaps
  40 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
  41 ///
  42 /// Eventually we will probably want to expose a variant of this which would essentially
  43 /// be what you'd want to run on a hardware wallet.
  44 ///
  45 /// Note that counterparty signatures on the holder transaction are not checked, but it should
  46 /// be in a complete implementation.
  47 ///
  48 /// Note that before we do so we should ensure its serialization format has backwards- and
  49 /// forwards-compatibility prefix/suffixes!
  50 #[derive(Clone)]
  51 pub struct EnforcingSigner {
  52         pub inner: InMemorySigner,
  53         /// Channel state used for policy enforcement
  54         pub state: Arc<Mutex<EnforcementState>>,
  55         pub disable_revocation_policy_check: bool,
  56 }
  57
  58 impl EnforcingSigner {
  59         /// Construct an EnforcingSigner
  60         pub fn new(inner: InMemorySigner) -> Self {
  61                 let state = Arc::new(Mutex::new(EnforcementState::new()));
  62                 Self {
  63                         inner,
  64                         state,
  65                         disable_revocation_policy_check: false
  66                 }
  67         }
  68
  69         /// Construct an EnforcingSigner with externally managed storage
  70         ///
  71         /// Since there are multiple copies of this struct for each channel, some coordination is needed
  72         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
  73         /// here, usually by an implementation of KeysInterface.
  74         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
  75                 Self {
  76                         inner,
  77                         state,
  78                         disable_revocation_policy_check
  79                 }
  80         }
  81
  82         #[cfg(test)]
  83         pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
  84                 self.state.lock().unwrap()
  85         }
  86 }
  87
  88 impl BaseSign for EnforcingSigner {
  89         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
  90                 self.inner.get_per_commitment_point(idx, secp_ctx)
  91         }
  92
  93         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
  94                 {
  95                         let mut state = self.state.lock().unwrap();
  96                         assert!(idx == state.last_holder_revoked_commitment || idx == state.last_holder_revoked_commitment - 1, "can only revoke the current or next unrevoked commitment - trying {}, last revoked {}", idx, state.last_holder_revoked_commitment);
  97                         assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
  98                         state.last_holder_revoked_commitment = idx;
  99                 }
 100                 self.inner.release_commitment_secret(idx)
 101         }
 102
 103         fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) -> Result<(), ()> {
 104                 let mut state = self.state.lock().unwrap();
 105                 let idx = holder_tx.commitment_number();
 106                 assert!(idx == state.last_holder_commitment || idx == state.last_holder_commitment - 1, "expecting to validate the current or next holder commitment - trying {}, current {}", idx, state.last_holder_commitment);
 107                 state.last_holder_commitment = idx;
 108                 Ok(())
 109         }
 110
 111         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
 112         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 113
 114         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 115                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
 116
 117                 {
 118                         let mut state = self.state.lock().unwrap();
 119                         let actual_commitment_number = commitment_tx.commitment_number();
 120                         let last_commitment_number = state.last_counterparty_commitment;
 121                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 122                         // or the next one.
 123                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 124                         // Ensure that the counterparty doesn't get more than two broadcastable commitments -
 125                         // the last and the one we are trying to sign
 126                         assert!(actual_commitment_number >= state.last_counterparty_revoked_commitment - 2, "cannot sign a commitment if second to last wasn't revoked - signing {} revoked {}", actual_commitment_number, state.last_counterparty_revoked_commitment);
 127                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
 128                 }
 129
 130                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
 131         }
 132
 133         fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
 134                 let mut state = self.state.lock().unwrap();
 135                 assert!(idx == state.last_counterparty_revoked_commitment || idx == state.last_counterparty_revoked_commitment - 1, "expecting to validate the current or next counterparty revocation - trying {}, current {}", idx, state.last_counterparty_revoked_commitment);
 136                 state.last_counterparty_revoked_commitment = idx;
 137                 Ok(())
 138         }
 139
 140         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 141                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 142                 let commitment_txid = trusted_tx.txid();
 143                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 144
 145                 let state = self.state.lock().unwrap();
 146                 let commitment_number = trusted_tx.commitment_number();
 147                 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
 148                         if !self.disable_revocation_policy_check {
 149                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 150                                        state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
 151                         }
 152                 }
 153
 154                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 155                         assert!(this_htlc.transaction_output_index.is_some());
 156                         let keys = trusted_tx.keys();
 157                         let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, trusted_tx.feerate_per_kw(), holder_csv, &this_htlc, &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
 158
 159                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
 160
 161                         let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
 162                         secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 163                 }
 164
 165                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 166         }
 167
 168         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 169         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 170                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 171         }
 172
 173         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 174                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 175         }
 176
 177         fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 178                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 179         }
 180
 181         fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 182                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 183         }
 184
 185         fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 186                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 187         }
 188
 189         fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 190                 self.inner.sign_channel_announcement(msg, secp_ctx)
 191         }
 192
 193         fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
 194                 self.inner.ready_channel(channel_parameters)
 195         }
 196 }
 197
 198 impl Sign for EnforcingSigner {}
 199
 200 impl Writeable for EnforcingSigner {
 201         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 202                 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
 203                 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
 204                 // [`KeysInterface::read_chan_signer`]. `state` is managed by [`KeysInterface`]
 205                 // and will be serialized as needed by the implementation of that trait.
 206                 self.inner.write(writer)?;
 207                 Ok(())
 208         }
 209 }
 210
 211 impl EnforcingSigner {
 212         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 213                 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
 214                                      self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
 215                         .expect("derived different per-tx keys or built transaction")
 216         }
 217
 218         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 219                 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
 220                                      self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
 221                         .expect("derived different per-tx keys or built transaction")
 222         }
 223 }
 224
 225 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
 226 ///
 227 /// This structure is maintained by KeysInterface since we may have multiple copies of
 228 /// the signer and they must coordinate their state.
 229 #[derive(Clone)]
 230 pub struct EnforcementState {
 231         /// The last counterparty commitment number we signed, backwards counting
 232         pub last_counterparty_commitment: u64,
 233         /// The last counterparty commitment they revoked, backwards counting
 234         pub last_counterparty_revoked_commitment: u64,
 235         /// The last holder commitment number we revoked, backwards counting
 236         pub last_holder_revoked_commitment: u64,
 237         /// The last validated holder commitment number, backwards counting
 238         pub last_holder_commitment: u64,
 239 }
 240
 241 impl EnforcementState {
 242         /// Enforcement state for a new channel
 243         pub fn new() -> Self {
 244                 EnforcementState {
 245                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 246                         last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 247                         last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 248                         last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 249                 }
 250         }
 251 }