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Merge pull request #2935 from valentinewallace/2024-03-keysend-to-blinded
[rust-lightning] / lightning / src / util / test_channel_signer.rs
1 // This file is Copyright its original authors, visible in version control
2 // history.
3 //
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
8 // licenses.
9
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::channel_keys::{HtlcKey};
13 use crate::ln::{msgs, PaymentPreimage};
14 use crate::sign::{InMemorySigner, ChannelSigner};
15 use crate::sign::ecdsa::{EcdsaChannelSigner, WriteableEcdsaChannelSigner};
16
17 use crate::prelude::*;
18 use core::cmp;
19 use crate::sync::{Mutex, Arc};
20 #[cfg(test)] use crate::sync::MutexGuard;
21
22 use bitcoin::blockdata::transaction::Transaction;
23 use bitcoin::hashes::Hash;
24 use bitcoin::sighash;
25 use bitcoin::sighash::EcdsaSighashType;
26
27 use bitcoin::secp256k1;
28 #[cfg(taproot)]
29 use bitcoin::secp256k1::All;
30 use bitcoin::secp256k1::{SecretKey, PublicKey};
31 use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
32 #[cfg(taproot)]
33 use musig2::types::{PartialSignature, PublicNonce, SecretNonce};
34 use crate::sign::HTLCDescriptor;
35 use crate::util::ser::{Writeable, Writer};
36 use crate::io::Error;
37 use crate::ln::features::ChannelTypeFeatures;
38 #[cfg(taproot)]
39 use crate::ln::msgs::PartialSignatureWithNonce;
40 #[cfg(taproot)]
41 use crate::sign::taproot::TaprootChannelSigner;
42
43 /// Initial value for revoked commitment downward counter
44 pub const INITIAL_REVOKED_COMMITMENT_NUMBER: u64 = 1 << 48;
45
46 /// An implementation of Sign that enforces some policy checks.  The current checks
47 /// are an incomplete set.  They include:
48 ///
49 /// - When signing, the holder transaction has not been revoked
50 /// - When revoking, the holder transaction has not been signed
51 /// - The holder commitment number is monotonic and without gaps
52 /// - The revoked holder commitment number is monotonic and without gaps
53 /// - There is at least one unrevoked holder transaction at all times
54 /// - The counterparty commitment number is monotonic and without gaps
55 /// - The pre-derived keys and pre-built transaction in CommitmentTransaction were correctly built
56 ///
57 /// Eventually we will probably want to expose a variant of this which would essentially
58 /// be what you'd want to run on a hardware wallet.
59 ///
60 /// Note that counterparty signatures on the holder transaction are not checked, but it should
61 /// be in a complete implementation.
62 ///
63 /// Note that before we do so we should ensure its serialization format has backwards- and
64 /// forwards-compatibility prefix/suffixes!
65 #[derive(Clone)]
66 pub struct TestChannelSigner {
67         pub inner: InMemorySigner,
68         /// Channel state used for policy enforcement
69         pub state: Arc<Mutex<EnforcementState>>,
70         pub disable_revocation_policy_check: bool,
71         /// When `true` (the default), the signer will respond immediately with signatures. When `false`,
72         /// the signer will return an error indicating that it is unavailable.
73         pub available: Arc<Mutex<bool>>,
74 }
75
76 impl PartialEq for TestChannelSigner {
77         fn eq(&self, o: &Self) -> bool {
78                 Arc::ptr_eq(&self.state, &o.state)
79         }
80 }
81
82 impl TestChannelSigner {
83         /// Construct an TestChannelSigner
84         pub fn new(inner: InMemorySigner) -> Self {
85                 let state = Arc::new(Mutex::new(EnforcementState::new()));
86                 Self {
87                         inner,
88                         state,
89                         disable_revocation_policy_check: false,
90                         available: Arc::new(Mutex::new(true)),
91                 }
92         }
93
94         /// Construct an TestChannelSigner with externally managed storage
95         ///
96         /// Since there are multiple copies of this struct for each channel, some coordination is needed
97         /// so that all copies are aware of enforcement state.  A pointer to this state is provided
98         /// here, usually by an implementation of KeysInterface.
99         pub fn new_with_revoked(inner: InMemorySigner, state: Arc<Mutex<EnforcementState>>, disable_revocation_policy_check: bool) -> Self {
100                 Self {
101                         inner,
102                         state,
103                         disable_revocation_policy_check,
104                         available: Arc::new(Mutex::new(true)),
105                 }
106         }
107
108         pub fn channel_type_features(&self) -> &ChannelTypeFeatures { self.inner.channel_type_features().unwrap() }
109
110         #[cfg(test)]
111         pub fn get_enforcement_state(&self) -> MutexGuard<EnforcementState> {
112                 self.state.lock().unwrap()
113         }
114
115         /// Marks the signer's availability.
116         ///
117         /// When `true`, methods are forwarded to the underlying signer as normal. When `false`, some
118         /// methods will return `Err` indicating that the signer is unavailable. Intended to be used for
119         /// testing asynchronous signing.
120         pub fn set_available(&self, available: bool) {
121                 *self.available.lock().unwrap() = available;
122         }
123 }
124
125 impl ChannelSigner for TestChannelSigner {
126         fn get_per_commitment_point(&self, idx: u64, secp_ctx: &Secp256k1<secp256k1::All>) -> PublicKey {
127                 self.inner.get_per_commitment_point(idx, secp_ctx)
128         }
129
130         fn release_commitment_secret(&self, idx: u64) -> [u8; 32] {
131                 {
132                         let mut state = self.state.lock().unwrap();
133                         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);
134                         assert!(idx > state.last_holder_commitment, "cannot revoke the last holder commitment - attempted to revoke {} last commitment {}", idx, state.last_holder_commitment);
135                         state.last_holder_revoked_commitment = idx;
136                 }
137                 self.inner.release_commitment_secret(idx)
138         }
139
140         fn validate_holder_commitment(&self, holder_tx: &HolderCommitmentTransaction, _outbound_htlc_preimages: Vec<PaymentPreimage>) -> Result<(), ()> {
141                 let mut state = self.state.lock().unwrap();
142                 let idx = holder_tx.commitment_number();
143                 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);
144                 state.last_holder_commitment = idx;
145                 Ok(())
146         }
147
148         fn validate_counterparty_revocation(&self, idx: u64, _secret: &SecretKey) -> Result<(), ()> {
149                 if !*self.available.lock().unwrap() {
150                         return Err(());
151                 }
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;
155                 Ok(())
156         }
157
158         fn pubkeys(&self) -> &ChannelPublicKeys { self.inner.pubkeys() }
159
160         fn channel_keys_id(&self) -> [u8; 32] { self.inner.channel_keys_id() }
161
162         fn provide_channel_parameters(&mut self, channel_parameters: &ChannelTransactionParameters) {
163                 self.inner.provide_channel_parameters(channel_parameters)
164         }
165 }
166
167 impl EcdsaChannelSigner for TestChannelSigner {
168         fn sign_counterparty_commitment(&self, commitment_tx: &CommitmentTransaction, inbound_htlc_preimages: Vec<PaymentPreimage>, outbound_htlc_preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<(Signature, Vec<Signature>), ()> {
169                 self.verify_counterparty_commitment_tx(commitment_tx, secp_ctx);
170
171                 {
172                         if !*self.available.lock().unwrap() {
173                                 return Err(());
174                         }
175                         let mut state = self.state.lock().unwrap();
176                         let actual_commitment_number = commitment_tx.commitment_number();
177                         let last_commitment_number = state.last_counterparty_commitment;
178                         // These commitment numbers are backwards counting.  We expect either the same as the previously encountered,
179                         // or the next one.
180                         assert!(last_commitment_number == actual_commitment_number || last_commitment_number - 1 == actual_commitment_number, "{} doesn't come after {}", actual_commitment_number, last_commitment_number);
181                         // Ensure that the counterparty doesn't get more than two broadcastable commitments -
182                         // the last and the one we are trying to sign
183                         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);
184                         state.last_counterparty_commitment = cmp::min(last_commitment_number, actual_commitment_number)
185                 }
186
187                 Ok(self.inner.sign_counterparty_commitment(commitment_tx, inbound_htlc_preimages, outbound_htlc_preimages, secp_ctx).unwrap())
188         }
189
190         fn sign_holder_commitment(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
191                 if !*self.available.lock().unwrap() {
192                         return Err(());
193                 }
194                 let trusted_tx = self.verify_holder_commitment_tx(commitment_tx, secp_ctx);
195                 let state = self.state.lock().unwrap();
196                 let commitment_number = trusted_tx.commitment_number();
197                 if state.last_holder_revoked_commitment - 1 != commitment_number && state.last_holder_revoked_commitment - 2 != commitment_number {
198                         if !self.disable_revocation_policy_check {
199                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
200                                        state.last_holder_revoked_commitment, commitment_number, self.inner.commitment_seed[0])
201                         }
202                 }
203                 Ok(self.inner.sign_holder_commitment(commitment_tx, secp_ctx).unwrap())
204         }
205
206         #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
207         fn unsafe_sign_holder_commitment(&self, commitment_tx: &HolderCommitmentTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
208                 Ok(self.inner.unsafe_sign_holder_commitment(commitment_tx, secp_ctx).unwrap())
209         }
210
211         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
212                 if !*self.available.lock().unwrap() {
213                         return Err(());
214                 }
215                 Ok(EcdsaChannelSigner::sign_justice_revoked_output(&self.inner, justice_tx, input, amount, per_commitment_key, secp_ctx).unwrap())
216         }
217
218         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, ()> {
219                 if !*self.available.lock().unwrap() {
220                         return Err(());
221                 }
222                 Ok(EcdsaChannelSigner::sign_justice_revoked_htlc(&self.inner, justice_tx, input, amount, per_commitment_key, htlc, secp_ctx).unwrap())
223         }
224
225         fn sign_holder_htlc_transaction(
226                 &self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor,
227                 secp_ctx: &Secp256k1<secp256k1::All>
228         ) -> Result<Signature, ()> {
229                 if !*self.available.lock().unwrap() {
230                         return Err(());
231                 }
232                 let state = self.state.lock().unwrap();
233                 if state.last_holder_revoked_commitment - 1 != htlc_descriptor.per_commitment_number &&
234                         state.last_holder_revoked_commitment - 2 != htlc_descriptor.per_commitment_number
235                 {
236                         if !self.disable_revocation_policy_check {
237                                 panic!("can only sign the next two unrevoked commitment numbers, revoked={} vs requested={} for {}",
238                                        state.last_holder_revoked_commitment, htlc_descriptor.per_commitment_number, self.inner.commitment_seed[0])
239                         }
240                 }
241                 assert_eq!(htlc_tx.input[input], htlc_descriptor.unsigned_tx_input());
242                 assert_eq!(htlc_tx.output[input], htlc_descriptor.tx_output(secp_ctx));
243                 {
244                         let witness_script = htlc_descriptor.witness_script(secp_ctx);
245                         let sighash_type = if self.channel_type_features().supports_anchors_zero_fee_htlc_tx() {
246                                 EcdsaSighashType::SinglePlusAnyoneCanPay
247                         } else {
248                                 EcdsaSighashType::All
249                         };
250                         let sighash = &sighash::SighashCache::new(&*htlc_tx).segwit_signature_hash(
251                                 input, &witness_script, htlc_descriptor.htlc.amount_msat / 1000, sighash_type
252                         ).unwrap();
253                         let countersignatory_htlc_key = HtlcKey::from_basepoint(
254                                 &secp_ctx, &self.inner.counterparty_pubkeys().unwrap().htlc_basepoint, &htlc_descriptor.per_commitment_point,
255                         );
256
257                         secp_ctx.verify_ecdsa(
258                                 &hash_to_message!(sighash.as_byte_array()), &htlc_descriptor.counterparty_sig, &countersignatory_htlc_key.to_public_key()
259                         ).unwrap();
260                 }
261                 Ok(EcdsaChannelSigner::sign_holder_htlc_transaction(&self.inner, htlc_tx, input, htlc_descriptor, secp_ctx).unwrap())
262         }
263
264         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, ()> {
265                 if !*self.available.lock().unwrap() {
266                         return Err(());
267                 }
268                 Ok(EcdsaChannelSigner::sign_counterparty_htlc_transaction(&self.inner, htlc_tx, input, amount, per_commitment_point, htlc, secp_ctx).unwrap())
269         }
270
271         fn sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<secp256k1::All>) -> Result<Signature, ()> {
272                 closing_tx.verify(self.inner.funding_outpoint().unwrap().into_bitcoin_outpoint())
273                         .expect("derived different closing transaction");
274                 Ok(self.inner.sign_closing_transaction(closing_tx, secp_ctx).unwrap())
275         }
276
277         fn sign_holder_anchor_input(
278                 &self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<secp256k1::All>,
279         ) -> Result<Signature, ()> {
280                 debug_assert!(MIN_CHAN_DUST_LIMIT_SATOSHIS > ANCHOR_OUTPUT_VALUE_SATOSHI);
281                 // As long as our minimum dust limit is enforced and is greater than our anchor output
282                 // value, an anchor output can only have an index within [0, 1].
283                 assert!(anchor_tx.input[input].previous_output.vout == 0 || anchor_tx.input[input].previous_output.vout == 1);
284                 if !*self.available.lock().unwrap() {
285                         return Err(());
286                 }
287                 EcdsaChannelSigner::sign_holder_anchor_input(&self.inner, anchor_tx, input, secp_ctx)
288         }
289
290         fn sign_channel_announcement_with_funding_key(
291                 &self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<secp256k1::All>
292         ) -> Result<Signature, ()> {
293                 self.inner.sign_channel_announcement_with_funding_key(msg, secp_ctx)
294         }
295 }
296
297 impl WriteableEcdsaChannelSigner for TestChannelSigner {}
298
299 #[cfg(taproot)]
300 impl TaprootChannelSigner for TestChannelSigner {
301         fn generate_local_nonce_pair(&self, commitment_number: u64, secp_ctx: &Secp256k1<All>) -> PublicNonce {
302                 todo!()
303         }
304
305         fn partially_sign_counterparty_commitment(&self, counterparty_nonce: PublicNonce, commitment_tx: &CommitmentTransaction, inbound_htlc_preimages: Vec<PaymentPreimage>, outbound_htlc_preimages: Vec<PaymentPreimage>, secp_ctx: &Secp256k1<All>) -> Result<(PartialSignatureWithNonce, Vec<secp256k1::schnorr::Signature>), ()> {
306                 todo!()
307         }
308
309         fn finalize_holder_commitment(&self, commitment_tx: &HolderCommitmentTransaction, counterparty_partial_signature: PartialSignatureWithNonce, secp_ctx: &Secp256k1<All>) -> Result<PartialSignature, ()> {
310                 todo!()
311         }
312
313         fn sign_justice_revoked_output(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, secp_ctx: &Secp256k1<All>) -> Result<secp256k1::schnorr::Signature, ()> {
314                 todo!()
315         }
316
317         fn sign_justice_revoked_htlc(&self, justice_tx: &Transaction, input: usize, amount: u64, per_commitment_key: &SecretKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<All>) -> Result<secp256k1::schnorr::Signature, ()> {
318                 todo!()
319         }
320
321         fn sign_holder_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, htlc_descriptor: &HTLCDescriptor, secp_ctx: &Secp256k1<All>) -> Result<secp256k1::schnorr::Signature, ()> {
322                 todo!()
323         }
324
325         fn sign_counterparty_htlc_transaction(&self, htlc_tx: &Transaction, input: usize, amount: u64, per_commitment_point: &PublicKey, htlc: &HTLCOutputInCommitment, secp_ctx: &Secp256k1<All>) -> Result<secp256k1::schnorr::Signature, ()> {
326                 todo!()
327         }
328
329         fn partially_sign_closing_transaction(&self, closing_tx: &ClosingTransaction, secp_ctx: &Secp256k1<All>) -> Result<PartialSignature, ()> {
330                 todo!()
331         }
332
333         fn sign_holder_anchor_input(&self, anchor_tx: &Transaction, input: usize, secp_ctx: &Secp256k1<All>) -> Result<secp256k1::schnorr::Signature, ()> {
334                 todo!()
335         }
336 }
337
338 impl Writeable for TestChannelSigner {
339         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
340                 // TestChannelSigner has two fields - `inner` ([`InMemorySigner`]) and `state`
341                 // ([`EnforcementState`]). `inner` is serialized here and deserialized by
342                 // [`SignerProvider::read_chan_signer`]. `state` is managed by [`SignerProvider`]
343                 // and will be serialized as needed by the implementation of that trait.
344                 self.inner.write(writer)?;
345                 Ok(())
346         }
347 }
348
349 impl TestChannelSigner {
350         fn verify_counterparty_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
351                 commitment_tx.verify(
352                         &self.inner.get_channel_parameters().unwrap().as_counterparty_broadcastable(),
353                         self.inner.counterparty_pubkeys().unwrap(), self.inner.pubkeys(), secp_ctx
354                 ).expect("derived different per-tx keys or built transaction")
355         }
356
357         fn verify_holder_commitment_tx<'a, T: secp256k1::Signing + secp256k1::Verification>(&self, commitment_tx: &'a CommitmentTransaction, secp_ctx: &Secp256k1<T>) -> TrustedCommitmentTransaction<'a> {
358                 commitment_tx.verify(
359                         &self.inner.get_channel_parameters().unwrap().as_holder_broadcastable(),
360                         self.inner.pubkeys(), self.inner.counterparty_pubkeys().unwrap(), secp_ctx
361                 ).expect("derived different per-tx keys or built transaction")
362         }
363 }
364
365 /// The state used by [`TestChannelSigner`] in order to enforce policy checks
366 ///
367 /// This structure is maintained by KeysInterface since we may have multiple copies of
368 /// the signer and they must coordinate their state.
369 #[derive(Clone)]
370 pub struct EnforcementState {
371         /// The last counterparty commitment number we signed, backwards counting
372         pub last_counterparty_commitment: u64,
373         /// The last counterparty commitment they revoked, backwards counting
374         pub last_counterparty_revoked_commitment: u64,
375         /// The last holder commitment number we revoked, backwards counting
376         pub last_holder_revoked_commitment: u64,
377         /// The last validated holder commitment number, backwards counting
378         pub last_holder_commitment: u64,
379 }
380
381 impl EnforcementState {
382         /// Enforcement state for a new channel
383         pub fn new() -> Self {
384                 EnforcementState {
385                         last_counterparty_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
386                         last_counterparty_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
387                         last_holder_revoked_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
388                         last_holder_commitment: INITIAL_REVOKED_COMMITMENT_NUMBER,
389                 }
390         }
391 }