_ 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 io;
  15 use prelude::*;
  16 use core::cmp;
  17 use sync::{Mutex, Arc};
  18 #[cfg(test)] use sync::MutexGuard;
  19
  20 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
  21 use bitcoin::util::bip143;
  22
  23 use bitcoin::secp256k1;
  24 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
  25 use bitcoin::secp256k1::{Secp256k1, Signature};
  26 use util::ser::{Writeable, Writer, Readable};
  27 use io::Error;
  28 use ln::msgs::DecodeError;
  29
  30 /// Initial value for revoked commitment downward counter
  31 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
  32
  33 /// An implementation of Sign that enforces some policy checks.  The current checks
  34 /// are an incomplete set.  They include:
  35 ///
  36 /// - When signing, the holder transaction has not been revoked
  37 /// - When revoking, the holder transaction has not been signed
  38 /// - The holder commitment number is monotonic and without gaps
  39 /// - The revoked holder commitment number is monotonic and without gaps
  40 /// - There is at least one unrevoked holder transaction at all times
  41 /// - The counterparty commitment number is monotonic and without gaps
  42 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
  43 ///
  44 /// Eventually we will probably want to expose a variant of this which would essentially
  45 /// be what you'd want to run on a hardware wallet.
  46 ///
  47 /// Note that counterparty signatures on the holder transaction are not checked, but it should
  48 /// be in a complete implementation.
  49 ///
  50 /// Note that before we do so we should ensure its serialization format has backwards- and
  51 /// forwards-compatibility prefix/suffixes!
  52 #[derive(Clone)]
  53 pub struct EnforcingSigner {
  54         pub inner: InMemorySigner,
  55         /// Channel state used for policy enforcement
  56         pub state: Arc<Mutex<EnforcementState>>,
  57         pub disable_revocation_policy_check: bool,
  58 }
  59
  60 impl EnforcingSigner {
  61         /// Construct an EnforcingSigner
  62         pub fn new(inner: InMemorySigner) -> Self {
  63                 let state = Arc::new(Mutex::new(EnforcementState::new()));
  64                 Self {
  65                         inner,
  66                         state,
  67                         disable_revocation_policy_check: false
  68                 }
  69         }
  70
  71         /// Construct an EnforcingSigner with externally managed storage
  72         ///
  73         /// Since there are multiple copies of this struct for each channel, some coordination is needed
  74         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
  75         /// here, usually by an implementation of KeysInterface.
  76         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
  77                 Self {
  78                         inner,
  79                         state,
  80                         disable_revocation_policy_check
  81                 }
  82         }
  83
  84         #[cfg(test)]
  85         pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
  86                 self.state.lock().unwrap()
  87         }
  88 }
  89
  90 impl BaseSign for EnforcingSigner {
  91         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
  92                 self.inner.get_per_commitment_point(idx, secp_ctx)
  93         }
  94
  95         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
  96                 {
  97                         let mut state = self.state.lock().unwrap();
  98                         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);
  99                         assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
 100                         state.last_holder_revoked_commitment = idx;
 101                 }
 102                 self.inner.release_commitment_secret(idx)
 103         }
 104
 105         fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) {
 106                 let mut state = self.state.lock().unwrap();
 107                 let idx = holder_tx.commitment_number();
 108                 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);
 109                 state.last_holder_commitment = idx;
 110         }
 111
 112         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
 113         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 114
 115         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 116                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
 117
 118                 {
 119                         let mut state = self.state.lock().unwrap();
 120                         let actual_commitment_number = commitment_tx.commitment_number();
 121                         let last_commitment_number = state.last_counterparty_commitment;
 122                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 123                         // or the next one.
 124                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 125                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
 126                 }
 127
 128                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
 129         }
 130
 131         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 132                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 133                 let commitment_txid = trusted_tx.txid();
 134                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 135
 136                 let state = self.state.lock().unwrap();
 137                 let commitment_number = trusted_tx.commitment_number();
 138                 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
 139                         if !self.disable_revocation_policy_check {
 140                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 141                                        state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
 142                         }
 143                 }
 144
 145                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 146                         assert!(this_htlc.transaction_output_index.is_some());
 147                         let keys = trusted_tx.keys();
 148                         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);
 149
 150                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
 151
 152                         let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
 153                         secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 154                 }
 155
 156                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 157         }
 158
 159         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 160         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 161                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 162         }
 163
 164         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 165                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 166         }
 167
 168         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, ()> {
 169                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 170         }
 171
 172         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, ()> {
 173                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 174         }
 175
 176         fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 177                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 178         }
 179
 180         fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 181                 self.inner.sign_channel_announcement(msg, secp_ctx)
 182         }
 183
 184         fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
 185                 self.inner.ready_channel(channel_parameters)
 186         }
 187 }
 188
 189 impl Sign for EnforcingSigner {}
 190
 191 impl Writeable for EnforcingSigner {
 192         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 193                 self.inner.write(writer)?;
 194                 // NOTE - the commitment state is maintained by KeysInterface, so we don't persist it
 195                 Ok(())
 196         }
 197 }
 198
 199 impl Readable for EnforcingSigner {
 200         fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 201                 let inner = Readable::read(reader)?;
 202                 let state = Arc::new(Mutex::new(EnforcementState::new()));
 203                 Ok(EnforcingSigner {
 204                         inner,
 205                         state,
 206                         disable_revocation_policy_check: false,
 207                 })
 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 holder commitment number we revoked, backwards counting
 234         pub last_holder_revoked_commitment: u64,
 235         /// The last validated holder commitment number, backwards counting
 236         pub last_holder_commitment: u64,
 237 }
 238
 239 impl EnforcementState {
 240         /// Enforcement state for a new channel
 241         pub fn new() -> Self {
 242                 EnforcementState {
 243                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 244                         last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 245                         last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 246                 }
 247         }
 248 }