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};
18 #[cfg(test)] use sync::MutexGuard;
20 use bitcoin::blockdata::transaction::{Transaction, SigHashType};
21 use bitcoin::util::bip143;
23 use bitcoin::secp256k1;
24 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
25 use bitcoin::secp256k1::{Secp256k1, Signature};
26 use util::ser::{Writeable, Writer, Readable};
28 use ln::msgs::DecodeError;
30 /// Initial value for revoked commitment downward counter
31 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
33 /// An implementation of Sign that enforces some policy checks. The current checks
34 /// are an incomplete set. They include:
36 /// - When signing, the holder transaction has not been revoked
37 /// - When revoking, the holder transaction has not been signed
38 /// - The holder commitment number is monotonic and without gaps
39 /// - The revoked holder commitment number is monotonic and without gaps
40 /// - There is at least one unrevoked holder transaction at all times
41 /// - The counterparty commitment number is monotonic and without gaps
42 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
44 /// Eventually we will probably want to expose a variant of this which would essentially
45 /// be what you'd want to run on a hardware wallet.
47 /// Note that counterparty signatures on the holder transaction are not checked, but it should
48 /// be in a complete implementation.
50 /// Note that before we do so we should ensure its serialization format has backwards- and
51 /// forwards-compatibility prefix/suffixes!
53 pub struct EnforcingSigner {
54 pub inner: InMemorySigner,
55 /// Channel state used for policy enforcement
56 pub state: Arc<Mutex<EnforcementState>>,
57 pub disable_revocation_policy_check: bool,
60 impl EnforcingSigner {
61 /// Construct an EnforcingSigner
62 pub fn new(inner: InMemorySigner) -> Self {
63 let state = Arc::new(Mutex::new(EnforcementState::new()));
67 disable_revocation_policy_check: false
71 /// Construct an EnforcingSigner with externally managed storage
73 /// Since there are multiple copies of this struct for each channel, some coordination is needed
74 /// so that all copies are aware of enforcement state. A pointer to this state is provided
75 /// here, usually by an implementation of KeysInterface.
76 pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
80 disable_revocation_policy_check
85 pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
86 self.state.lock().unwrap()
90 impl BaseSign for EnforcingSigner {
91 fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
92 self.inner.get_per_commitment_point(idx, secp_ctx)
95 fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
97 let mut state = self.state.lock().unwrap();
98 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);
99 assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
100 state.last_holder_revoked_commitment = idx;
102 self.inner.release_commitment_secret(idx)
105 fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction) {
106 let mut state = self.state.lock().unwrap();
107 let idx = holder_tx.commitment_number();
108 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);
109 state.last_holder_commitment = idx;
112 fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
113 fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
115 fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
116 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
119 let mut state = self.state.lock().unwrap();
120 let actual_commitment_number = commitment_tx.commitment_number();
121 let last_commitment_number = state.last_counterparty_commitment;
122 // These commitment numbers are backwards counting. We expect either the same as the previously encountered,
124 assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
125 state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
128 Ok(self.inner.sign_counterparty_commitment(commitment_tx, secp_ctx).unwrap())
131 fn sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
132 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
133 let commitment_txid = trusted_tx.txid();
134 let holder_csv = self.inner.counterparty_selected_contest_delay();
136 let state = self.state.lock().unwrap();
137 let commitment_number = trusted_tx.commitment_number();
138 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
139 if !self.disable_revocation_policy_check {
140 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
141 state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
145 for (this_htlc, sig) in trusted_tx.htlcs().iter().zip(&commitment_tx.counterparty_htlc_sigs) {
146 assert!(this_htlc.transaction_output_index.is_some());
147 let keys = trusted_tx.keys();
148 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);
150 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&this_htlc, &keys);
152 let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]);
153 secp_ctx.verify(&sighash, sig, &keys.countersignatory_htlc_key).unwrap();
156 Ok(self.inner.sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
159 #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
160 fn unsafe_sign_holder_commitment_and_htlcs(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
161 Ok(self.inner.unsafe_sign_holder_commitment_and_htlcs(commitment_tx, secp_ctx).unwrap())
164 fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
165 Ok(self.inner.sign_justice_revoked_output(justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
168 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, ()> {
169 Ok(self.inner.sign_justice_revoked_htlc(justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
172 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, ()> {
173 Ok(self.inner.sign_counterparty_htlc_transaction(htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
176 fn sign_closing_transaction(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
177 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
180 fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
181 self.inner.sign_channel_announcement(msg, secp_ctx)
184 fn ready_channel(&mut self, channel_parameters: &ChannelTransactionParameters) {
185 self.inner.ready_channel(channel_parameters)
189 impl Sign for EnforcingSigner {}
191 impl Writeable for EnforcingSigner {
192 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
193 self.inner.write(writer)?;
194 // NOTE - the commitment state is maintained by KeysInterface, so we don't persist it
199 impl Readable for EnforcingSigner {
200 fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
201 let inner = Readable::read(reader)?;
202 let state = Arc::new(Mutex::new(EnforcementState::new()));
206 disable_revocation_policy_check: false,
211 impl EnforcingSigner {
212 fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
213 commitment_tx.verify(&self.inner.get_channel_parameters().as_counterparty_broadcastable(),
214 self.inner.counterparty_pubkeys(), self.inner.pubkeys(), secp_ctx)
215 .expect("derived different per-tx keys or built transaction")
218 fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
219 commitment_tx.verify(&self.inner.get_channel_parameters().as_holder_broadcastable(),
220 self.inner.pubkeys(), self.inner.counterparty_pubkeys(), secp_ctx)
221 .expect("derived different per-tx keys or built transaction")
225 /// The state used by [`EnforcingSigner`] in order to enforce policy checks
227 /// This structure is maintained by KeysInterface since we may have multiple copies of
228 /// the signer and they must coordinate their state.
230 pub struct EnforcementState {
231 /// The last counterparty commitment number we signed, backwards counting
232 pub last_counterparty_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_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
245 last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,