+impl EcdsaChannelSigner for EnforcingSigner {
+ fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
+ self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
+
+ {
+ let mut state = self.state.lock().unwrap();
+ let actual_commitment_number = commitment_tx.commitment_number();
+ let last_commitment_number = state.last_counterparty_commitment;
+ // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
+ // or the next one.
+ assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
+ // Ensure that the counterparty doesn't get more than two broadcastable commitments -
+ // the last and the one we are trying to sign
+ 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);
+ state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
+ }
+
+ Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
+ }
+
+ fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
+ let mut state = self.state.lock().unwrap();
+ 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);
+ state.last_counterparty_revoked_commitment = idx;
+ Ok(())
+ }
+
+ fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
+ let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
+ let commitment_txid = trusted_tx.txid();
+ let holder_csv = self.inner.counterparty_selected_contest_delay();
+
+ let state = self.state.lock().unwrap();
+ let commitment_number = trusted_tx.commitment_number();
+ if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
+ if !self.disable_revocation_policy_check {
+ panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
+ state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
+ }
+ }
+
+ for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
+ assert!(this_htlc.transaction_output_index.is_some());
+ let keys = trusted_tx.keys();
+ 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);
+
+ let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.opt_anchors(), &keys);
+
+ let sighash_type = if self.opt_anchors() {
+ EcdsaSighashType::SinglePlusAnyoneCanPay
+ } else {
+ EcdsaSighashType::All
+ };
+ let sighash = hash_to_message!(
+ &sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(
+ 0, &htlc_redeemscript, this_htlc.amount_msat / 1000, sighash_type,
+ ).unwrap()[..]
+ );
+ secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
+ }
+
+ Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
+ }
+
+ #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
+ fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
+ Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
+ }
+
+ fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
+ Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
+ }
+
+ 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, ()> {
+ Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
+ }
+
+ #[cfg(anchors)]
+ fn sign_holder_htlc_transaction(
+ &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
+ secp_ctx: &Secp256k1<secp256k1::All>
+ ) -> Result<Signature, ()> {
+ let per_commitment_point = self.get_per_commitment_point(htlc_descriptor.per_commitment_number, secp_ctx);
+ assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
+ assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(&per_commitment_point, secp_ctx));
+ Ok(self.inner.sign_holder_htlc_transaction(htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
+ }
+
+ 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, ()> {
+ Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
+ }
+
+ fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
+ closing_tx.verify(self.inner.funding_outpoint().into_bitcoin_outpoint())
+ .expect("derived different closing transaction");
+ Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
+ }
+
+ fn sign_holder_anchor_input(
+ &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
+ ) -> Result<Signature, ()> {
+ debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
+ // As long as our minimum dust limit is enforced and is greater than our anchor output
+ // value, an anchor output can only have an index within [0, 1].
+ assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
+ self.inner.sign_holder_anchor_input(anchor_tx, input, secp_ctx)
+ }
+
+ fn sign_channel_announcement_with_funding_key(
+ &self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
+ ) -> Result<Signature, ()> {
+ self.inner.sign_channel_announcement_with_funding_key(msg, secp_ctx)
+ }
+}
+
+impl WriteableEcdsaChannelSigner for EnforcingSigner {}
+
+impl Writeable for EnforcingSigner {
+ fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
+ // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
+ // ([`EnforcementState`]). `inner` is serialized here and deserialized by
+ // [`SignerProvider::read_chan_signer`]. `state` is managed by [`SignerProvider`]
+ // and will be serialized as needed by the implementation of that trait.
+ self.inner.write(writer)?;
+ Ok(())
+ }
+}
+
+impl EnforcingSigner {
+ fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
+ commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
+ self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
+ .expect("derived different per-tx keys or built transaction")
+ }
+
+ fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
+ commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
+ self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
+ .expect("derived different per-tx keys or built transaction")
+ }
+}
+
+/// The state used by [`EnforcingSigner`] in order to enforce policy checks
+///
+/// This structure is maintained by KeysInterface since we may have multiple copies of
+/// the signer and they must coordinate their state.
+#[derive(Clone)]
+pub struct EnforcementState {
+ /// The last counterparty commitment number we signed, backwards counting
+ pub last_counterparty_commitment: u64,
+ /// The last counterparty commitment they revoked, backwards counting
+ pub last_counterparty_revoked_commitment: u64,
+ /// The last holder commitment number we revoked, backwards counting
+ pub last_holder_revoked_commitment: u64,
+ /// The last validated holder commitment number, backwards counting
+ pub last_holder_commitment: u64,
+}
+
+impl EnforcementState {
+ /// Enforcement state for a new channel
+ pub fn new() -> Self {
+ EnforcementState {
+ last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+ last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+ last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+ last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
+ }
+ }
+}