1 // This file is Copyright its original authors, visible in version control
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
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};
15 use crate::prelude::*;
17 use crate::sync::{Mutex, Arc};
18 #[cfg(test)] use crate::sync::MutexGuard;
20 use bitcoin::blockdata::transaction::{Transaction, EcdsaSighashType};
21 use bitcoin::util::sighash;
23 use bitcoin::secp256k1;
24 use bitcoin::secp256k1::{SecretKey, PublicKey};
25 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
27 use crate::events::bump_transaction::HTLCDescriptor;
28 use crate::util::ser::{Writeable, Writer};
30 use crate::ln::features::ChannelTypeFeatures;
32 /// Initial value for revoked commitment downward counter
33 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
35 /// An implementation of Sign that enforces some policy checks. The current checks
36 /// are an incomplete set. They include:
38 /// - When signing, the holder transaction has not been revoked
39 /// - When revoking, the holder transaction has not been signed
40 /// - The holder commitment number is monotonic and without gaps
41 /// - The revoked holder commitment number is monotonic and without gaps
42 /// - There is at least one unrevoked holder transaction at all times
43 /// - The counterparty commitment number is monotonic and without gaps
44 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
46 /// Eventually we will probably want to expose a variant of this which would essentially
47 /// be what you'd want to run on a hardware wallet.
49 /// Note that counterparty signatures on the holder transaction are not checked, but it should
50 /// be in a complete implementation.
52 /// Note that before we do so we should ensure its serialization format has backwards- and
53 /// forwards-compatibility prefix/suffixes!
55 pub struct EnforcingSigner {
56 pub inner: InMemorySigner,
57 /// Channel state used for policy enforcement
58 pub state: Arc<Mutex<EnforcementState>>,
59 pub disable_revocation_policy_check: bool,
62 impl PartialEq for EnforcingSigner {
63 fn eq(&self, o: &Self) -> bool {
64 Arc::ptr_eq(&self.state, &o.state)
68 impl EnforcingSigner {
69 /// Construct an EnforcingSigner
70 pub fn new(inner: InMemorySigner) -> Self {
71 let state = Arc::new(Mutex::new(EnforcementState::new()));
75 disable_revocation_policy_check: false
79 /// Construct an EnforcingSigner with externally managed storage
81 /// Since there are multiple copies of this struct for each channel, some coordination is needed
82 /// so that all copies are aware of enforcement state. A pointer to this state is provided
83 /// here, usually by an implementation of KeysInterface.
84 pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
88 disable_revocation_policy_check
92 pub fn channel_type_features(&self) -> &ChannelTypeFeatures { self.inner.channel_type_features() }
95 pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
96 self.state.lock().unwrap()
100 impl ChannelSigner for EnforcingSigner {
101 fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
102 self.inner.get_per_commitment_point(idx, secp_ctx)
105 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
107 let mut state = self.state.lock().unwrap();
108 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);
109 assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
110 state.last_holder_revoked_commitment = idx;
112 self.inner.release_commitment_secret(idx)
115 fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction, _preimages: Vec<PaymentPreimage>) -> Result<(), ()> {
116 let mut state = self.state.lock().unwrap();
117 let idx = holder_tx.commitment_number();
118 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);
119 state.last_holder_commitment = idx;
123 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
125 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
127 fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
128 self.inner.provide_channel_parameters(channel_parameters)
132 impl EcdsaChannelSigner for EnforcingSigner {
133 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
134 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
137 let mut state = self.state.lock().unwrap();
138 let actual_commitment_number = commitment_tx.commitment_number();
139 let last_commitment_number = state.last_counterparty_commitment;
140 // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
142 assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
143 // Ensure that the counterparty doesn't get more than two broadcastable commitments -
144 // the last and the one we are trying to sign
145 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);
146 state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
149 Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
152 fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
153 let mut state = self.state.lock().unwrap();
154 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);
155 state.last_counterparty_revoked_commitment = idx;
159 fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
160 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
161 let commitment_txid = trusted_tx.txid();
162 let holder_csv = self.inner.counterparty_selected_contest_delay();
164 let state = self.state.lock().unwrap();
165 let commitment_number = trusted_tx.commitment_number();
166 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
167 if !self.disable_revocation_policy_check {
168 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
169 state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
173 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
174 assert!(this_htlc.transaction_output_index.is_some());
175 let keys = trusted_tx.keys();
176 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, trusted_tx.feerate_per_kw(), holder_csv, &this_htlc, self.channel_type_features(), &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
178 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.channel_type_features(), &keys);
180 let sighash_type = if self.channel_type_features().supports_anchors_zero_fee_htlc_tx() {
181 EcdsaSighashType::SinglePlusAnyoneCanPay
183 EcdsaSighashType::All
185 let sighash = hash_to_message!(
186 &sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(
187 0, &htlc_redeemscript, this_htlc.amount_msat / 1000, sighash_type,
190 secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
193 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
196 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
197 fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
198 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
201 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
202 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
205 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, ()> {
206 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
210 fn sign_holder_htlc_transaction(
211 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
212 secp_ctx: &Secp256k1<secp256k1::All>
213 ) -> Result<Signature, ()> {
214 let per_commitment_point = self.get_per_commitment_point(htlc_descriptor.per_commitment_number, secp_ctx);
215 assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
216 assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(&per_commitment_point, secp_ctx));
217 Ok(self.inner.sign_holder_htlc_transaction(htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
220 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, ()> {
221 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
224 fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
225 closing_tx.verify(self.inner.funding_outpoint().into_bitcoin_outpoint())
226 .expect("derived different closing transaction");
227 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
230 fn sign_holder_anchor_input(
231 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
232 ) -> Result<Signature, ()> {
233 debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
234 // As long as our minimum dust limit is enforced and is greater than our anchor output
235 // value, an anchor output can only have an index within [0, 1].
236 assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
237 self.inner.sign_holder_anchor_input(anchor_tx, input, secp_ctx)
240 fn sign_channel_announcement_with_funding_key(
241 &self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
242 ) -> Result<Signature, ()> {
243 self.inner.sign_channel_announcement_with_funding_key(msg, secp_ctx)
247 impl WriteableEcdsaChannelSigner for EnforcingSigner {}
249 impl Writeable for EnforcingSigner {
250 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
251 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
252 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
253 // [`SignerProvider::read_chan_signer`]. `state` is managed by [`SignerProvider`]
254 // and will be serialized as needed by the implementation of that trait.
255 self.inner.write(writer)?;
260 impl EnforcingSigner {
261 fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
262 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
263 self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
264 .expect("derived different per-tx keys or built transaction")
267 fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
268 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
269 self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
270 .expect("derived different per-tx keys or built transaction")
274 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
276 /// This structure is maintained by KeysInterface since we may have multiple copies of
277 /// the signer and they must coordinate their state.
279 pub struct EnforcementState {
280 /// The last counterparty commitment number we signed, backwards counting
281 pub last_counterparty_commitment: u64,
282 /// The last counterparty commitment they revoked, backwards counting
283 pub last_counterparty_revoked_commitment: u64,
284 /// The last holder commitment number we revoked, backwards counting
285 pub last_holder_revoked_commitment: u64,
286 /// The last validated holder commitment number, backwards counting
287 pub last_holder_commitment: u64,
290 impl EnforcementState {
291 /// Enforcement state for a new channel
292 pub fn new() -> Self {
294 last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
295 last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
296 last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
297 last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,