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::chain::keysinterface::{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::util::events::HTLCDescriptor;
28 use crate::util::ser::{Writeable, Writer};
31 /// Initial value for revoked commitment downward counter
32 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
34 /// An implementation of Sign that enforces some policy checks. The current checks
35 /// are an incomplete set. They include:
37 /// - When signing, the holder transaction has not been revoked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
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.
48 /// Note that counterparty signatures on the holder transaction are not checked, but it should
49 /// be in a complete implementation.
51 /// Note that before we do so we should ensure its serialization format has backwards- and
52 /// forwards-compatibility prefix/suffixes!
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,
61 impl EnforcingSigner {
62 /// Construct an EnforcingSigner
63 pub fn new(inner: InMemorySigner) -> Self {
64 let state = Arc::new(Mutex::new(EnforcementState::new()));
68 disable_revocation_policy_check: false
72 /// Construct an EnforcingSigner with externally managed storage
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 {
81 disable_revocation_policy_check
85 pub fn opt_anchors(&self) -> bool { self.inner.opt_anchors() }
88 pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
89 self.state.lock().unwrap()
93 impl ChannelSigner 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)
98 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
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;
105 self.inner.release_commitment_secret(idx)
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;
116 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
118 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
120 fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
121 self.inner.provide_channel_parameters(channel_parameters)
125 impl EcdsaChannelSigner for EnforcingSigner {
126 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
127 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
130 let mut state = self.state.lock().unwrap();
131 let actual_commitment_number = commitment_tx.commitment_number();
132 let last_commitment_number = state.last_counterparty_commitment;
133 // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
135 assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
136 // Ensure that the counterparty doesn't get more than two broadcastable commitments -
137 // the last and the one we are trying to sign
138 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);
139 state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
142 Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
145 fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
146 let mut state = self.state.lock().unwrap();
147 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);
148 state.last_counterparty_revoked_commitment = idx;
152 fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
153 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
154 let commitment_txid = trusted_tx.txid();
155 let holder_csv = self.inner.counterparty_selected_contest_delay();
157 let state = self.state.lock().unwrap();
158 let commitment_number = trusted_tx.commitment_number();
159 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
160 if !self.disable_revocation_policy_check {
161 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
162 state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
166 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
167 assert!(this_htlc.transaction_output_index.is_some());
168 let keys = trusted_tx.keys();
169 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);
171 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.opt_anchors(), &keys);
173 let sighash_type = if self.opt_anchors() {
174 EcdsaSighashType::SinglePlusAnyoneCanPay
176 EcdsaSighashType::All
178 let sighash = hash_to_message!(
179 &sighash::SighashCache::new(&htlc_tx).segwit_signature_hash(
180 0, &htlc_redeemscript, this_htlc.amount_msat / 1000, sighash_type,
183 secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
186 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
189 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
190 fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
191 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
194 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
195 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
198 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, ()> {
199 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
203 fn sign_holder_htlc_transaction(
204 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
205 secp_ctx: &Secp256k1<secp256k1::All>
206 ) -> Result<Signature, ()> {
207 let per_commitment_point = self.get_per_commitment_point(htlc_descriptor.per_commitment_number, secp_ctx);
208 assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
209 assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(&per_commitment_point, secp_ctx));
210 Ok(self.inner.sign_holder_htlc_transaction(htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
213 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, ()> {
214 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
217 fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
218 closing_tx.verify(self.inner.funding_outpoint().into_bitcoin_outpoint())
219 .expect("derived different closing transaction");
220 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
223 fn sign_holder_anchor_input(
224 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
225 ) -> Result<Signature, ()> {
226 debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
227 // As long as our minimum dust limit is enforced and is greater than our anchor output
228 // value, an anchor output can only have an index within [0, 1].
229 assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
230 self.inner.sign_holder_anchor_input(anchor_tx, input, secp_ctx)
233 fn sign_channel_announcement_with_funding_key(
234 &self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
235 ) -> Result<Signature, ()> {
236 self.inner.sign_channel_announcement_with_funding_key(msg, secp_ctx)
240 impl WriteableEcdsaChannelSigner for EnforcingSigner {}
242 impl Writeable for EnforcingSigner {
243 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
244 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
245 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
246 // [`SignerProvider::read_chan_signer`]. `state` is managed by [`SignerProvider`]
247 // and will be serialized as needed by the implementation of that trait.
248 self.inner.write(writer)?;
253 impl EnforcingSigner {
254 fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
255 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
256 self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
257 .expect("derived different per-tx keys or built transaction")
260 fn verify_holder_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_holder_broadcastable(),
262 self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
263 .expect("derived different per-tx keys or built transaction")
267 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
269 /// This structure is maintained by KeysInterface since we may have multiple copies of
270 /// the signer and they must coordinate their state.
272 pub struct EnforcementState {
273 /// The last counterparty commitment number we signed, backwards counting
274 pub last_counterparty_commitment: u64,
275 /// The last counterparty commitment they revoked, backwards counting
276 pub last_counterparty_revoked_commitment: u64,
277 /// The last holder commitment number we revoked, backwards counting
278 pub last_holder_revoked_commitment: u64,
279 /// The last validated holder commitment number, backwards counting
280 pub last_holder_commitment: u64,
283 impl EnforcementState {
284 /// Enforcement state for a new channel
285 pub fn new() -> Self {
287 last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
288 last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
289 last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
290 last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,