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::sign::{WriteableEcdsaChannelSigner, InMemorySigner, ChannelSigner, EcdsaChannelSigner};
  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::events::bump_transaction::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  37 /// - When signing, the holder transaction has not been revoked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 PartialEq for EnforcingSigner {
  62         fn eq(&self, o: &Self) -> bool {
  63                 Arc::ptr_eq(&self.state, &o.state)
  64         }
  65 }
  66
  67 impl EnforcingSigner {
  68         /// Construct an EnforcingSigner
  69         pub fn new(inner: InMemorySigner) -> Self {
  70                 let state = Arc::new(Mutex::new(EnforcementState::new()));
  71                 Self {
  72                         inner,
  73                         state,
  74                         disable_revocation_policy_check: false
  75                 }
  76         }
  77
  78         /// Construct an EnforcingSigner with externally managed storage
  79         ///
  80         /// Since there are multiple copies of this struct for each channel, some coordination is needed
  81         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
  82         /// here, usually by an implementation of KeysInterface.
  83         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
  84                 Self {
  85                         inner,
  86                         state,
  87                         disable_revocation_policy_check
  88                 }
  89         }
  90
  91         pub fn opt_anchors(&self) -> bool { self.inner.opt_anchors() }
  92
  93         #[cfg(test)]
  94         pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
  95                 self.state.lock().unwrap()
  96         }
  97 }
  98
  99 impl ChannelSigner for EnforcingSigner {
 100         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
 101                 self.inner.get_per_commitment_point(idx, secp_ctx)
 102         }
 103
 104         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
 105                 {
 106                         let mut state = self.state.lock().unwrap();
 107                         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);
 108                         assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
 109                         state.last_holder_revoked_commitment = idx;
 110                 }
 111                 self.inner.release_commitment_secret(idx)
 112         }
 113
 114         fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction, _preimages: Vec<PaymentPreimage>) -> Result<(), ()> {
 115                 let mut state = self.state.lock().unwrap();
 116                 let idx = holder_tx.commitment_number();
 117                 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);
 118                 state.last_holder_commitment = idx;
 119                 Ok(())
 120         }
 121
 122         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
 123
 124         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
 125
 126         fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
 127                 self.inner.provide_channel_parameters(channel_parameters)
 128         }
 129 }
 130
 131 impl EcdsaChannelSigner for EnforcingSigner {
 132         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 133                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
 134
 135                 {
 136                         let mut state = self.state.lock().unwrap();
 137                         let actual_commitment_number = commitment_tx.commitment_number();
 138                         let last_commitment_number = state.last_counterparty_commitment;
 139                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
 140                         // or the next one.
 141                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
 142                         // Ensure that the counterparty doesn't get more than two broadcastable commitments -
 143                         // the last and the one we are trying to sign
 144                         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);
 145                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
 146                 }
 147
 148                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
 149         }
 150
 151         fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
 152                 let mut state = self.state.lock().unwrap();
 153                 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);
 154                 state.last_counterparty_revoked_commitment = idx;
 155                 Ok(())
 156         }
 157
 158         fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 159                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
 160                 let commitment_txid = trusted_tx.txid();
 161                 let holder_csv = self.inner.counterparty_selected_contest_delay();
 162
 163                 let state = self.state.lock().unwrap();
 164                 let commitment_number = trusted_tx.commitment_number();
 165                 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
 166                         if !self.disable_revocation_policy_check {
 167                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
 168                                        state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
 169                         }
 170                 }
 171
 172                 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
 173                         assert!(this_htlc.transaction_output_index.is_some());
 174                         let keys = trusted_tx.keys();
 175                         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);
 176
 177                         let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.opt_anchors(), &keys);
 178
 179                         let sighash_type = if self.opt_anchors() {
 180                                 EcdsaSighashType::SinglePlusAnyoneCanPay
 181                         } else {
 182                                 EcdsaSighashType::All
 183                         };
 184                         let sighash = hash_to_message!(
 185                                 &sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(
 186                                         0, &htlc_redeemscript, this_htlc.amount_msat / 1000, sighash_type,
 187                                 ).unwrap()[..]
 188                         );
 189                         secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
 190                 }
 191
 192                 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 193         }
 194
 195         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
 196         fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
 197                 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
 198         }
 199
 200         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 201                 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
 202         }
 203
 204         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, ()> {
 205                 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
 206         }
 207
 208         #[cfg(anchors)]
 209         fn sign_holder_htlc_transaction(
 210                 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
 211                 secp_ctx: &Secp256k1<secp256k1::All>
 212         ) -> Result<Signature, ()> {
 213                 let per_commitment_point = self.get_per_commitment_point(htlc_descriptor.per_commitment_number, secp_ctx);
 214                 assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
 215                 assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(&per_commitment_point, secp_ctx));
 216                 Ok(self.inner.sign_holder_htlc_transaction(htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
 217         }
 218
 219         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, ()> {
 220                 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
 221         }
 222
 223         fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
 224                 closing_tx.verify(self.inner.funding_outpoint().into_bitcoin_outpoint())
 225                         .expect("derived different closing transaction");
 226                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
 227         }
 228
 229         fn sign_holder_anchor_input(
 230                 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
 231         ) -> Result<Signature, ()> {
 232                 debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
 233                 // As long as our minimum dust limit is enforced and is greater than our anchor output
 234                 // value, an anchor output can only have an index within [0, 1].
 235                 assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
 236                 self.inner.sign_holder_anchor_input(anchor_tx, input, secp_ctx)
 237         }
 238
 239         fn sign_channel_announcement_with_funding_key(
 240                 &self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
 241         ) -> Result<Signature, ()> {
 242                 self.inner.sign_channel_announcement_with_funding_key(msg, secp_ctx)
 243         }
 244 }
 245
 246 impl WriteableEcdsaChannelSigner for EnforcingSigner {}
 247
 248 impl Writeable for EnforcingSigner {
 249         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
 250                 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
 251                 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
 252                 // [`SignerProvider::read_chan_signer`]. `state` is managed by [`SignerProvider`]
 253                 // and will be serialized as needed by the implementation of that trait.
 254                 self.inner.write(writer)?;
 255                 Ok(())
 256         }
 257 }
 258
 259 impl EnforcingSigner {
 260         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 261                 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
 262                                      self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
 263                         .expect("derived different per-tx keys or built transaction")
 264         }
 265
 266         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
 267                 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
 268                                      self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
 269                         .expect("derived different per-tx keys or built transaction")
 270         }
 271 }
 272
 273 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
 274 ///
 275 /// This structure is maintained by KeysInterface since we may have multiple copies of
 276 /// the signer and they must coordinate their state.
 277 #[derive(Clone)]
 278 pub struct EnforcementState {
 279         /// The last counterparty commitment number we signed, backwards counting
 280         pub last_counterparty_commitment: u64,
 281         /// The last counterparty commitment they revoked, backwards counting
 282         pub last_counterparty_revoked_commitment: u64,
 283         /// The last holder commitment number we revoked, backwards counting
 284         pub last_holder_revoked_commitment: u64,
 285         /// The last validated holder commitment number, backwards counting
 286         pub last_holder_commitment: u64,
 287 }
 288
 289 impl EnforcementState {
 290         /// Enforcement state for a new channel
 291         pub fn new() -> Self {
 292                 EnforcementState {
 293                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 294                         last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 295                         last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 296                         last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
 297                 }
 298         }
 299 }