git.bitcoin.ninja 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 crate::ln::channel::{ANCHOR_OUTPUT_VALUE_SATOSHI, MIN_CHAN_DUST_LIMIT_SATOSHIS};
  11 use crate::ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction, ClosingTransaction};
  12 use crate::ln::{chan_utils, msgs, PaymentPreimage};
  13 use crate::chain::keysinterface::{Sign, InMemorySigner, BaseSign};
  14
  15 use crate::prelude::*;
  16 use core::cmp;
  17 use crate::sync::{Mutex, Arc};
  18 #[cfg(test)] use crate::sync::MutexGuard;
  19
  20 use bitcoin::blockdata::transaction::{Transaction, EcdsaSighashType};
  21 use bitcoin::util::sighash;
  22
  23 use bitcoin::secp256k1;
  24 use bitcoin::secp256k1::{SecretKey, PublicKey};
  25 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
  26 #[cfg(anchors)]
  27 use crate::util::events::HTLCDescriptor;
  28 use crate::util::ser::{Writeable, Writer};
  29 use crate::io::Error;
  30
  31 /// Initial value for revoked commitment downward counter
  32 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
  33
  34 /// An implementation of Sign that enforces some policy checks.  The current checks
  35 /// are an incomplete set.  They include:
  36 ///
  37 /// - When signing, the holder transaction has not been revoked
  38 /// - When revoking, the holder transaction has not been signed
  39 /// - The holder commitment number is monotonic and without gaps
  40 /// - The revoked holder commitment number is monotonic and without gaps
  41 /// - There is at least one unrevoked holder transaction at all times
  42 /// - The counterparty commitment number is monotonic and without gaps
  43 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
  44 ///
  45 /// Eventually we will probably want to expose a variant of this which would essentially
  46 /// be what you'd want to run on a hardware wallet.
  47 ///
  48 /// Note that counterparty signatures on the holder transaction are not checked, but it should
  49 /// be in a complete implementation.
  50 ///
  51 /// Note that before we do so we should ensure its serialization format has backwards- and
  52 /// forwards-compatibility prefix/suffixes!
  53 #[derive(Clone)]
  54 pub struct EnforcingSigner {
  55         pub inner: InMemorySigner,
  56         /// Channel state used for policy enforcement
  57         pub state: Arc<Mutex<EnforcementState>>,
  58         pub disable_revocation_policy_check: bool,
  59 }
  60
  61 impl EnforcingSigner {
  62         /// Construct an EnforcingSigner
  63         pub fn new(inner: InMemorySigner) -> Self {
  64                 let state = Arc::new(Mutex::new(EnforcementState::new()));
  65                 Self {
  66                         inner,
  67                         state,
  68                         disable_revocation_policy_check: false
  69                 }
  70         }
  71
  72         /// Construct an EnforcingSigner with externally managed storage
  73         ///
  74         /// Since there are multiple copies of this struct for each channel, some coordination is needed
  75         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
  76         /// here, usually by an implementation of KeysInterface.
  77         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
  78                 Self {
  79                         inner,
  80                         state,
  81                         disable_revocation_policy_check
  82                 }
  83         }
  84
  85         pub fn opt_anchors(&self) -> bool { self.inner.opt_anchors() }
  86
  87         #[cfg(test)]
  88         pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
  89                 self.state.lock().unwrap()
  90         }
  91 }
  92
  93 impl BaseSign for EnforcingSigner {
  94         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
  95                 self.inner.get_per_commitment_point(idx, secp_ctx)
  96         }
  97
  98         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
  99                 {
 100                         let mut state = self.state.lock().unwrap();
 101                         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);
 102                         assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
 103                         state.last_holder_revoked_commitment = idx;
 104                 }
 105                 self.inner.release_commitment_secret(idx)
 106         }
 107
 108         fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction, _preimages: Vec<PaymentPreimage>) -> Result<(), ()> {
 109                 let mut state = self.state.lock().unwrap();
 110                 let idx = holder_tx.commitment_number();
 111                 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);
 112                 state.last_holder_commitment = idx;
 113                 Ok(())
 114         }
 115
 116         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
 117         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 118
 119         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 120                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
 121
 122                 {
 123                         let mut state = self.state.lock().unwrap();
 124                         let actual_commitment_number = commitment_tx.commitment_number();
 125                         let last_commitment_number = state.last_counterparty_commitment;
 126                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 127                         // or the next one.
 128                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 129                         // Ensure that the counterparty doesn't get more than two broadcastable commitments -
 130                         // the last and the one we are trying to sign
 131                         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);
 132                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
 133                 }
 134
 135                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
 136         }
 137
 138         fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
 139                 let mut state = self.state.lock().unwrap();
 140                 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);
 141                 state.last_counterparty_revoked_commitment = idx;
 142                 Ok(())
 143         }
 144
 145         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 146                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 147                 let commitment_txid = trusted_tx.txid();
 148                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 149
 150                 let state = self.state.lock().unwrap();
 151                 let commitment_number = trusted_tx.commitment_number();
 152                 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
 153                         if !self.disable_revocation_policy_check {
 154                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 155                                        state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
 156                         }
 157                 }
 158
 159                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 160                         assert!(this_htlc.transaction_output_index.is_some());
 161                         let keys = trusted_tx.keys();
 162                         let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, trusted_tx.feerate_per_kw(), holder_csv, &this_htlc, self.opt_anchors(), false, &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
 163
 164                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.opt_anchors(), &keys);
 165
 166                         let sighash_type = if self.opt_anchors() {
 167                                 EcdsaSighashType::SinglePlusAnyoneCanPay
 168                         } else {
 169                                 EcdsaSighashType::All
 170                         };
 171                         let sighash = hash_to_message!(
 172                                 &sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(
 173                                         0, &htlc_redeemscript, this_htlc.amount_msat / 1000, sighash_type,
 174                                 ).unwrap()[..]
 175                         );
 176                         secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 177                 }
 178
 179                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 180         }
 181
 182         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 183         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 184                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 185         }
 186
 187         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 188                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 189         }
 190
 191         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, ()> {
 192                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 193         }
 194
 195         #[cfg(anchors)]
 196         fn sign_holder_htlc_transaction(
 197                 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
 198                 secp_ctx: &Secp256k1<secp256k1::All>
 199         ) -> Result<Signature, ()> {
 200                 let per_commitment_point = self.get_per_commitment_point(htlc_descriptor.per_commitment_number, secp_ctx);
 201                 assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
 202                 assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(&per_commitment_point, secp_ctx));
 203                 Ok(self.inner.sign_holder_htlc_transaction(htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
 204         }
 205
 206         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, ()> {
 207                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 208         }
 209
 210         fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 211                 closing_tx.verify(self.inner.funding_outpoint().into_bitcoin_outpoint())
 212                         .expect("derived different closing transaction");
 213                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 214         }
 215
 216         fn sign_holder_anchor_input(
 217                 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
 218         ) -> Result<Signature, ()> {
 219                 debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
 220                 // As long as our minimum dust limit is enforced and is greater than our anchor output
 221                 // value, an anchor output can only have an index within [0, 1].
 222                 assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
 223                 self.inner.sign_holder_anchor_input(anchor_tx, input, secp_ctx)
 224         }
 225
 226         fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>)
 227         -> Result<(Signature, Signature), ()> {
 228                 self.inner.sign_channel_announcement(msg, secp_ctx)
 229         }
 230
 231         fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
 232                 self.inner.provide_channel_parameters(channel_parameters)
 233         }
 234 }
 235
 236 impl Sign for EnforcingSigner {}
 237
 238 impl Writeable for EnforcingSigner {
 239         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 240                 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
 241                 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
 242                 // [`KeysInterface::read_chan_signer`]. `state` is managed by [`KeysInterface`]
 243                 // and will be serialized as needed by the implementation of that trait.
 244                 self.inner.write(writer)?;
 245                 Ok(())
 246         }
 247 }
 248
 249 impl EnforcingSigner {
 250         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 251                 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
 252                                      self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
 253                         .expect("derived different per-tx keys or built transaction")
 254         }
 255
 256         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 257                 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
 258                                      self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
 259                         .expect("derived different per-tx keys or built transaction")
 260         }
 261 }
 262
 263 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
 264 ///
 265 /// This structure is maintained by KeysInterface since we may have multiple copies of
 266 /// the signer and they must coordinate their state.
 267 #[derive(Clone)]
 268 pub struct EnforcementState {
 269         /// The last counterparty commitment number we signed, backwards counting
 270         pub last_counterparty_commitment: u64,
 271         /// The last counterparty commitment they revoked, backwards counting
 272         pub last_counterparty_revoked_commitment: u64,
 273         /// The last holder commitment number we revoked, backwards counting
 274         pub last_holder_revoked_commitment: u64,
 275         /// The last validated holder commitment number, backwards counting
 276         pub last_holder_commitment: u64,
 277 }
 278
 279 impl EnforcementState {
 280         /// Enforcement state for a new channel
 281         pub fn new() -> Self {
 282                 EnforcementState {
 283                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 284                         last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 285                         last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 286                         last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 287                 }
 288         }
 289 }