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};
16 use sync::{Mutex, Arc};
17 #[cfg(test)] use sync::MutexGuard;
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};
28 /// Initial value for revoked commitment downward counter
29 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
31 /// An implementation of Sign that enforces some policy checks. The current checks
32 /// are an incomplete set. They include:
34 /// - When signing, the holder transaction has not been revoked
35 /// - When revoking, the holder transaction has not been signed
36 /// - The holder commitment number is monotonic and without gaps
37 /// - The revoked holder commitment number is monotonic and without gaps
38 /// - There is at least one unrevoked holder transaction at all times
39 /// - The counterparty commitment number is monotonic and without gaps
40 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
42 /// Eventually we will probably want to expose a variant of this which would essentially
43 /// be what you'd want to run on a hardware wallet.
45 /// Note that counterparty signatures on the holder transaction are not checked, but it should
46 /// be in a complete implementation.
48 /// Note that before we do so we should ensure its serialization format has backwards- and
49 /// forwards-compatibility prefix/suffixes!
51 pub struct EnforcingSigner {
52 pub inner: InMemorySigner,
53 /// Channel state used for policy enforcement
54 pub state: Arc<Mutex<EnforcementState>>,
55 pub disable_revocation_policy_check: bool,
58 impl EnforcingSigner {
59 /// Construct an EnforcingSigner
60 pub fn new(inner: InMemorySigner) -> Self {
61 let state = Arc::new(Mutex::new(EnforcementState::new()));
65 disable_revocation_policy_check: false
69 /// Construct an EnforcingSigner with externally managed storage
71 /// Since there are multiple copies of this struct for each channel, some coordination is needed
72 /// so that all copies are aware of enforcement state. A pointer to this state is provided
73 /// here, usually by an implementation of KeysInterface.
74 pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
78 disable_revocation_policy_check
83 pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
84 self.state.lock().unwrap()
88 impl BaseSign for EnforcingSigner {
89 fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
90 self.inner.get_per_commitment_point(idx, secp_ctx)
93 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
95 let mut state = self.state.lock().unwrap();
96 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);
97 assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
98 state.last_holder_revoked_commitment = idx;
100 self.inner.release_commitment_secret(idx)
103 fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) {
104 let mut state = self.state.lock().unwrap();
105 let idx = holder_tx.commitment_number();
106 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);
107 state.last_holder_commitment = idx;
110 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
111 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
113 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
114 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
117 let mut state = self.state.lock().unwrap();
118 let actual_commitment_number = commitment_tx.commitment_number();
119 let last_commitment_number = state.last_counterparty_commitment;
120 // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
122 assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
123 // Ensure that the counterparty doesn't get more than two broadcastable commitments -
124 // the last and the one we are trying to sign
125 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);
126 state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
129 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
132 fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) {
133 let mut state = self.state.lock().unwrap();
134 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);
135 state.last_counterparty_revoked_commitment = idx;
138 fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
139 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
140 let commitment_txid = trusted_tx.txid();
141 let holder_csv = self.inner.counterparty_selected_contest_delay();
143 let state = self.state.lock().unwrap();
144 let commitment_number = trusted_tx.commitment_number();
145 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
146 if !self.disable_revocation_policy_check {
147 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
148 state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
152 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
153 assert!(this_htlc.transaction_output_index.is_some());
154 let keys = trusted_tx.keys();
155 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);
157 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
159 let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
160 secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
163 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
166 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
167 fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
168 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
171 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
172 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
175 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, ()> {
176 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
179 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, ()> {
180 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
183 fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
184 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
187 fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
188 self.inner.sign_channel_announcement(msg, secp_ctx)
191 fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
192 self.inner.ready_channel(channel_parameters)
196 impl Sign for EnforcingSigner {}
198 impl Writeable for EnforcingSigner {
199 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
200 // EnforcingSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
201 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
202 // [`KeysInterface::read_chan_signer`]. `state` is managed by [`KeysInterface`]
203 // and will be serialized as needed by the implementation of that trait.
204 self.inner.write(writer)?;
209 impl EnforcingSigner {
210 fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
211 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
212 self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
213 .expect("derived different per-tx keys or built transaction")
216 fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
217 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
218 self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
219 .expect("derived different per-tx keys or built transaction")
223 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
225 /// This structure is maintained by KeysInterface since we may have multiple copies of
226 /// the signer and they must coordinate their state.
228 pub struct EnforcementState {
229 /// The last counterparty commitment number we signed, backwards counting
230 pub last_counterparty_commitment: u64,
231 /// The last counterparty commitment they revoked, backwards counting
232 pub last_counterparty_revoked_commitment: u64,
233 /// The last holder commitment number we revoked, backwards counting
234 pub last_holder_revoked_commitment: u64,
235 /// The last validated holder commitment number, backwards counting
236 pub last_holder_commitment: u64,
239 impl EnforcementState {
240 /// Enforcement state for a new channel
241 pub fn new() -> Self {
243 last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
244 last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
245 last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
246 last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,