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 ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, HolderCommitmentTransaction, CommitmentTransaction, ChannelTransactionParameters, TrustedCommitmentTransaction};
11 use ln::{chan_utils, msgs};
12 use chain::keysinterface::{Sign, InMemorySigner, BaseSign};
17 use sync::{Mutex, Arc};
19 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
20 use bitcoin::util::bip143;
22 use bitcoin::secp256k1;
23 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
24 use bitcoin::secp256k1::{Secp256k1, Signature};
25 use util::ser::{Writeable, Writer, Readable};
27 use ln::msgs::DecodeError;
29 /// Initial value for revoked commitment downward counter
30 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
32 /// An implementation of Sign that enforces some policy checks. The current checks
33 /// are an incomplete set. They include:
35 /// - When signing, the holder transaction has not been revoked
36 /// - When revoking, the holder transaction has not been signed
37 /// - The holder commitment number is monotonic and without gaps
38 /// - The counterparty commitment number is monotonic and without gaps
39 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
41 /// Eventually we will probably want to expose a variant of this which would essentially
42 /// be what you'd want to run on a hardware wallet.
44 /// Note that before we do so we should ensure its serialization format has backwards- and
45 /// forwards-compatibility prefix/suffixes!
47 pub struct EnforcingSigner {
48 pub inner: InMemorySigner,
49 /// Channel state used for policy enforcement
50 pub state: Arc<Mutex<EnforcementState>>,
51 pub disable_revocation_policy_check: bool,
54 impl EnforcingSigner {
55 /// Construct an EnforcingSigner
56 pub fn new(inner: InMemorySigner) -> Self {
57 let state = Arc::new(Mutex::new(EnforcementState::new()));
61 disable_revocation_policy_check: false
65 /// Construct an EnforcingSigner with externally managed storage
67 /// Since there are multiple copies of this struct for each channel, some coordination is needed
68 /// so that all copies are aware of enforcement state. A pointer to this state is provided
69 /// here, usually by an implementation of KeysInterface.
70 pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
74 disable_revocation_policy_check
79 impl BaseSign for EnforcingSigner {
80 fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
81 self.inner.get_per_commitment_point(idx, secp_ctx)
84 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
86 let mut state = self.state.lock().unwrap();
87 assert!(idx == state.revoked_commitment || idx == state.revoked_commitment - 1, "can only revoke the current or next unrevoked commitment - trying {}, revoked {}", idx, state.revoked_commitment);
88 state.revoked_commitment = idx;
90 self.inner.release_commitment_secret(idx)
93 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
94 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
96 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
97 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
100 let mut state = self.state.lock().unwrap();
101 let actual_commitment_number = commitment_tx.commitment_number();
102 let last_commitment_number = state.last_counterparty_commitment;
103 // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
105 assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
106 state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
109 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
112 fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
113 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
114 let commitment_txid = trusted_tx.txid();
115 let holder_csv = self.inner.counterparty_selected_contest_delay();
117 let state = self.state.lock().unwrap();
118 let commitment_number = trusted_tx.commitment_number();
119 if state.revoked_commitment - 1 != commitment_number && state.revoked_commitment - 2 != commitment_number {
120 if !self.disable_revocation_policy_check {
121 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
122 state.revoked_commitment, commitment_number, self.inner.commitment_seed[0])
126 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
127 assert!(this_htlc.transaction_output_index.is_some());
128 let keys = trusted_tx.keys();
129 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, trusted_tx.feerate_per_kw(), holder_csv, &this_htlc, &keys.broadcaster_delayed_payment_key, &keys.revocation_key);
131 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
133 let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
134 secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
137 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
140 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
141 fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
142 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
145 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
146 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
149 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, ()> {
150 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
153 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, ()> {
154 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
157 fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
158 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
161 fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
162 self.inner.sign_channel_announcement(msg, secp_ctx)
165 fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
166 self.inner.ready_channel(channel_parameters)
170 impl Sign for EnforcingSigner {}
172 impl Writeable for EnforcingSigner {
173 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
174 self.inner.write(writer)?;
175 // NOTE - the commitment state is maintained by KeysInterface, so we don't persist it
180 impl Readable for EnforcingSigner {
181 fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
182 let inner = Readable::read(reader)?;
183 let state = Arc::new(Mutex::new(EnforcementState::new()));
187 disable_revocation_policy_check: false,
192 impl EnforcingSigner {
193 fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
194 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
195 self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
196 .expect("derived different per-tx keys or built transaction")
199 fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
200 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
201 self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
202 .expect("derived different per-tx keys or built transaction")
206 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
208 /// This structure is maintained by KeysInterface since we may have multiple copies of
209 /// the signer and they must coordinate their state.
211 pub struct EnforcementState {
212 /// The last counterparty commitment number we signed, backwards counting
213 pub last_counterparty_commitment: u64,
214 /// The last holder commitment number we revoked, backwards counting
215 pub revoked_commitment: u64,
219 impl EnforcementState {
220 /// Enforcement state for a new channel
221 pub fn new() -> Self {
223 last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
224 revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,