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::events::bump_transaction::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37 /// - When signing, the holder transaction has not been revoked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 PartialEq for EnforcingSigner {
62 fn eq(&self, o: &Self) -> bool {
63 Arc::ptr_eq(&self.state, &o.state)
67 impl EnforcingSigner {
68 /// Construct an EnforcingSigner
69 pub fn new(inner: InMemorySigner) -> Self {
70 let state = Arc::new(Mutex::new(EnforcementState::new()));
74 disable_revocation_policy_check: false
78 /// Construct an EnforcingSigner with externally managed storage
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 {
87 disable_revocation_policy_check
91 pub fn opt_anchors(&self) -> bool { self.inner.opt_anchors() }
94 pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
95 self.state.lock().unwrap()
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)
104 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
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;
111 self.inner.release_commitment_secret(idx)
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;
122 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
124 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
126 fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
127 self.inner.provide_channel_parameters(channel_parameters)
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);
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,
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)
148 Ok(self.inner.sign_counterparty_commitment(commitment_tx, preimages, secp_ctx).unwrap())
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;
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();
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])
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);
177 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, self.opt_anchors(), &keys);
179 let sighash_type = if self.opt_anchors() {
180 EcdsaSighashType::SinglePlusAnyoneCanPay
182 EcdsaSighashType::All
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,
189 secp_ctx.verify_ecdsa(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
192 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
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())
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())
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())
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())
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())
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())
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)
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)
246 impl WriteableEcdsaChannelSigner for EnforcingSigner {}
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)?;
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")
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")
273 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
275 /// This structure is maintained by KeysInterface since we may have multiple copies of
276 /// the signer and they must coordinate their state.
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,
289 impl EnforcementState {
290 /// Enforcement state for a new channel
291 pub fn new() -> Self {
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,