1 //! keysinterface provides keys into rust-lightning and defines some useful enums which describe
2 //! spendable on-chain outputs which the user owns and is responsible for using just as any other
3 //! on-chain output which is theirs.
5 use bitcoin::blockdata::transaction::{Transaction, OutPoint, TxOut};
6 use bitcoin::blockdata::script::{Script, Builder};
7 use bitcoin::blockdata::opcodes;
8 use bitcoin::network::constants::Network;
9 use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber};
10 use bitcoin::util::bip143;
12 use bitcoin_hashes::{Hash, HashEngine};
13 use bitcoin_hashes::sha256::HashEngine as Sha256State;
14 use bitcoin_hashes::sha256::Hash as Sha256;
15 use bitcoin_hashes::sha256d::Hash as Sha256dHash;
16 use bitcoin_hashes::hash160::Hash as Hash160;
18 use secp256k1::key::{SecretKey, PublicKey};
19 use secp256k1::{Secp256k1, Signature};
23 use util::logger::Logger;
24 use util::ser::Writeable;
27 use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys};
31 use std::sync::atomic::{AtomicUsize, Ordering};
33 /// When on-chain outputs are created by rust-lightning an event is generated which informs the
34 /// user thereof. This enum describes the format of the output and provides the OutPoint.
35 pub enum SpendableOutputDescriptor {
36 /// Outpoint with an output to a script which was provided via KeysInterface, thus you should
37 /// have stored somewhere how to spend script_pubkey!
38 /// Outputs from a justice tx, claim tx or preimage tx
40 /// The outpoint spendable by user wallet
42 /// The output which is referenced by the given outpoint
45 /// Outpoint commits to a P2WSH
46 /// P2WSH should be spend by the following witness :
47 /// <local_delayedsig> 0 <witnessScript>
48 /// With input nSequence set to_self_delay.
49 /// Outputs from a HTLC-Success/Timeout tx/commitment tx
51 /// Outpoint spendable by user wallet
53 /// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint) OR
55 /// witness redeemScript encumbering output.
56 witness_script: Script,
57 /// nSequence input must commit to self_delay to satisfy script's OP_CSV
59 /// The output which is referenced by the given outpoint
62 /// Outpoint commits to a P2WPKH
63 /// P2WPKH should be spend by the following witness :
64 /// <local_sig> <local_pubkey>
65 /// Outputs to_remote from a commitment tx
67 /// Outpoint spendable by user wallet
69 /// localkey = payment_basepoint_secret + SHA256(per_commitment_point || payment_basepoint
71 /// The output which is reference by the given outpoint
76 /// A trait to describe an object which can get user secrets and key material.
77 pub trait KeysInterface: Send + Sync {
78 /// A type which implements ChannelKeys which will be returned by get_channel_keys.
79 type ChanKeySigner : ChannelKeys;
81 /// Get node secret key (aka node_id or network_key)
82 fn get_node_secret(&self) -> SecretKey;
83 /// Get destination redeemScript to encumber static protocol exit points.
84 fn get_destination_script(&self) -> Script;
85 /// Get shutdown_pubkey to use as PublicKey at channel closure
86 fn get_shutdown_pubkey(&self) -> PublicKey;
87 /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you
88 /// restarted with some stale data!
89 fn get_channel_keys(&self, inbound: bool, channel_value_satoshis: u64) -> Self::ChanKeySigner;
90 /// Get a secret and PRNG seed for construting an onion packet
91 fn get_onion_rand(&self) -> (SecretKey, [u8; 32]);
92 /// Get a unique temporary channel id. Channels will be referred to by this until the funding
93 /// transaction is created, at which point they will use the outpoint in the funding
95 fn get_channel_id(&self) -> [u8; 32];
98 /// Set of lightning keys needed to operate a channel as described in BOLT 3.
100 /// Signing services could be implemented on a hardware wallet. In this case,
101 /// the current ChannelKeys would be a front-end on top of a communication
102 /// channel connected to your secure device and lightning key material wouldn't
103 /// reside on a hot server. Nevertheless, a this deployment would still need
104 /// to trust the ChannelManager to avoid loss of funds as this latest component
105 /// could ask to sign commitment transaction with HTLCs paying to attacker pubkeys.
107 /// A more secure iteration would be to use hashlock (or payment points) to pair
108 /// invoice/incoming HTLCs with outgoing HTLCs to implement a no-trust-ChannelManager
109 /// at the price of more state and computation on the hardware wallet side. In the future,
110 /// we are looking forward to design such interface.
112 /// In any case, ChannelMonitor or fallback watchtowers are always going to be trusted
113 /// to act, as liveness and breach reply correctness are always going to be hard requirements
114 /// of LN security model, orthogonal of key management issues.
116 /// If you're implementing a custom signer, you almost certainly want to implement
117 /// Readable/Writable to serialize out a unique reference to this set of keys so
118 /// that you can serialize the full ChannelManager object.
120 /// (TODO: We shouldn't require that, and should have an API to get them at deser time, due mostly
121 /// to the possibility of reentrancy issues by calling the user's code during our deserialization
123 pub trait ChannelKeys : Send {
124 /// Gets the private key for the anchor tx
125 fn funding_key<'a>(&'a self) -> &'a SecretKey;
126 /// Gets the local secret key for blinded revocation pubkey
127 fn revocation_base_key<'a>(&'a self) -> &'a SecretKey;
128 /// Gets the local secret key used in to_remote output of remote commitment tx
129 /// (and also as part of obscured commitment number)
130 fn payment_base_key<'a>(&'a self) -> &'a SecretKey;
131 /// Gets the local secret key used in HTLC-Success/HTLC-Timeout txn and to_local output
132 fn delayed_payment_base_key<'a>(&'a self) -> &'a SecretKey;
133 /// Gets the local htlc secret key used in commitment tx htlc outputs
134 fn htlc_base_key<'a>(&'a self) -> &'a SecretKey;
135 /// Gets the commitment seed
136 fn commitment_seed<'a>(&'a self) -> &'a [u8; 32];
138 /// Create a signature for a remote commitment transaction and associated HTLC transactions.
140 /// Note that if signing fails or is rejected, the channel will be force-closed.
142 /// TODO: Document the things someone using this interface should enforce before signing.
143 /// TODO: Add more input vars to enable better checking (preferably removing commitment_tx and
144 /// making the callee generate it via some util function we expose)!
145 fn sign_remote_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()>;
147 /// Create a signature for a (proposed) closing transaction.
149 /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
150 /// chosen to forgo their output as dust.
151 fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
153 /// Signs a channel announcement message with our funding key, proving it comes from one
154 /// of the channel participants.
156 /// Note that if this fails or is rejected, the channel will not be publicly announced and
157 /// our counterparty may (though likely will not) close the channel on us for violating the
159 fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
161 /// Set the remote channel basepoints. This is done immediately on incoming channels
162 /// and as soon as the channel is accepted on outgoing channels.
164 /// Will be called before any signatures are applied.
165 fn set_remote_channel_pubkeys(&mut self, channel_points: &ChannelPublicKeys);
169 /// A simple implementation of ChannelKeys that just keeps the private keys in memory.
170 pub struct InMemoryChannelKeys {
171 /// Private key of anchor tx
172 pub funding_key: SecretKey,
173 /// Local secret key for blinded revocation pubkey
174 pub revocation_base_key: SecretKey,
175 /// Local secret key used in commitment tx htlc outputs
176 pub payment_base_key: SecretKey,
177 /// Local secret key used in HTLC tx
178 pub delayed_payment_base_key: SecretKey,
179 /// Local htlc secret key used in commitment tx htlc outputs
180 pub htlc_base_key: SecretKey,
182 pub commitment_seed: [u8; 32],
183 /// Remote public keys and base points
184 pub remote_channel_pubkeys: Option<ChannelPublicKeys>,
185 /// The total value of this channel
186 pub channel_value_satoshis: u64,
189 impl ChannelKeys for InMemoryChannelKeys {
190 fn funding_key(&self) -> &SecretKey { &self.funding_key }
191 fn revocation_base_key(&self) -> &SecretKey { &self.revocation_base_key }
192 fn payment_base_key(&self) -> &SecretKey { &self.payment_base_key }
193 fn delayed_payment_base_key(&self) -> &SecretKey { &self.delayed_payment_base_key }
194 fn htlc_base_key(&self) -> &SecretKey { &self.htlc_base_key }
195 fn commitment_seed(&self) -> &[u8; 32] { &self.commitment_seed }
197 fn sign_remote_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
198 if commitment_tx.input.len() != 1 { return Err(()); }
200 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
201 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
202 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
204 let commitment_sighash = hash_to_message!(&bip143::SighashComponents::new(&commitment_tx).sighash_all(&commitment_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
205 let commitment_sig = secp_ctx.sign(&commitment_sighash, &self.funding_key);
207 let commitment_txid = commitment_tx.txid();
209 let mut htlc_sigs = Vec::with_capacity(htlcs.len());
210 for ref htlc in htlcs {
211 if let Some(_) = htlc.transaction_output_index {
212 let htlc_tx = chan_utils::build_htlc_transaction(&commitment_txid, feerate_per_kw, to_self_delay, htlc, &keys.a_delayed_payment_key, &keys.revocation_key);
213 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys);
214 let htlc_sighash = hash_to_message!(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]);
215 let our_htlc_key = match chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key) {
217 Err(_) => return Err(()),
219 htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &our_htlc_key));
223 Ok((commitment_sig, htlc_sigs))
226 fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
227 if closing_tx.input.len() != 1 { return Err(()); }
228 if closing_tx.input[0].witness.len() != 0 { return Err(()); }
229 if closing_tx.output.len() > 2 { return Err(()); }
231 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
232 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
233 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
235 let sighash = hash_to_message!(&bip143::SighashComponents::new(closing_tx)
236 .sighash_all(&closing_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
237 Ok(secp_ctx.sign(&sighash, &self.funding_key))
240 fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
241 let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
242 Ok(secp_ctx.sign(&msghash, &self.funding_key))
245 fn set_remote_channel_pubkeys(&mut self, channel_pubkeys: &ChannelPublicKeys) {
246 assert!(self.remote_channel_pubkeys.is_none(), "Already set remote channel pubkeys");
247 self.remote_channel_pubkeys = Some(channel_pubkeys.clone());
251 impl_writeable!(InMemoryChannelKeys, 0, {
255 delayed_payment_base_key,
258 remote_channel_pubkeys,
259 channel_value_satoshis
262 /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key
263 /// and derives keys from that.
265 /// Your node_id is seed/0'
266 /// ChannelMonitor closes may use seed/1'
267 /// Cooperative closes may use seed/2'
268 /// The two close keys may be needed to claim on-chain funds!
269 pub struct KeysManager {
270 secp_ctx: Secp256k1<secp256k1::SignOnly>,
271 node_secret: SecretKey,
272 destination_script: Script,
273 shutdown_pubkey: PublicKey,
274 channel_master_key: ExtendedPrivKey,
275 channel_child_index: AtomicUsize,
276 session_master_key: ExtendedPrivKey,
277 session_child_index: AtomicUsize,
278 channel_id_master_key: ExtendedPrivKey,
279 channel_id_child_index: AtomicUsize,
281 unique_start: Sha256State,
286 /// Constructs a KeysManager from a 32-byte seed. If the seed is in some way biased (eg your
287 /// RNG is busted) this may panic (but more importantly, you will possibly lose funds).
288 /// starting_time isn't strictly required to actually be a time, but it must absolutely,
289 /// without a doubt, be unique to this instance. ie if you start multiple times with the same
290 /// seed, starting_time must be unique to each run. Thus, the easiest way to achieve this is to
291 /// simply use the current time (with very high precision).
293 /// The seed MUST be backed up safely prior to use so that the keys can be re-created, however,
294 /// obviously, starting_time should be unique every time you reload the library - it is only
295 /// used to generate new ephemeral key data (which will be stored by the individual channel if
298 /// Note that the seed is required to recover certain on-chain funds independent of
299 /// ChannelMonitor data, though a current copy of ChannelMonitor data is also required for any
300 /// channel, and some on-chain during-closing funds.
302 /// Note that until the 0.1 release there is no guarantee of backward compatibility between
303 /// versions. Once the library is more fully supported, the docs will be updated to include a
304 /// detailed description of the guarantee.
305 pub fn new(seed: &[u8; 32], network: Network, logger: Arc<Logger>, starting_time_secs: u64, starting_time_nanos: u32) -> KeysManager {
306 let secp_ctx = Secp256k1::signing_only();
307 match ExtendedPrivKey::new_master(network.clone(), seed) {
309 let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key.key;
310 let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1).unwrap()) {
311 Ok(destination_key) => {
312 let pubkey_hash160 = Hash160::hash(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.key.serialize()[..]);
313 Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
314 .push_slice(&pubkey_hash160.into_inner())
317 Err(_) => panic!("Your RNG is busted"),
319 let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2).unwrap()) {
320 Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key.key,
321 Err(_) => panic!("Your RNG is busted"),
323 let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3).unwrap()).expect("Your RNG is busted");
324 let session_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4).unwrap()).expect("Your RNG is busted");
325 let channel_id_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(5).unwrap()).expect("Your RNG is busted");
327 let mut unique_start = Sha256::engine();
328 unique_start.input(&byte_utils::be64_to_array(starting_time_secs));
329 unique_start.input(&byte_utils::be32_to_array(starting_time_nanos));
330 unique_start.input(seed);
338 channel_child_index: AtomicUsize::new(0),
340 session_child_index: AtomicUsize::new(0),
341 channel_id_master_key,
342 channel_id_child_index: AtomicUsize::new(0),
348 Err(_) => panic!("Your rng is busted"),
353 impl KeysInterface for KeysManager {
354 type ChanKeySigner = InMemoryChannelKeys;
356 fn get_node_secret(&self) -> SecretKey {
357 self.node_secret.clone()
360 fn get_destination_script(&self) -> Script {
361 self.destination_script.clone()
364 fn get_shutdown_pubkey(&self) -> PublicKey {
365 self.shutdown_pubkey.clone()
368 fn get_channel_keys(&self, _inbound: bool, channel_value_satoshis: u64) -> InMemoryChannelKeys {
369 // We only seriously intend to rely on the channel_master_key for true secure
370 // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
371 // starting_time provided in the constructor) to be unique.
372 let mut sha = self.unique_start.clone();
374 let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
375 let child_privkey = self.channel_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
376 sha.input(&child_privkey.private_key.key[..]);
378 let seed = Sha256::from_engine(sha).into_inner();
380 let commitment_seed = {
381 let mut sha = Sha256::engine();
383 sha.input(&b"commitment seed"[..]);
384 Sha256::from_engine(sha).into_inner()
386 macro_rules! key_step {
387 ($info: expr, $prev_key: expr) => {{
388 let mut sha = Sha256::engine();
390 sha.input(&$prev_key[..]);
391 sha.input(&$info[..]);
392 SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("SHA-256 is busted")
395 let funding_key = key_step!(b"funding key", commitment_seed);
396 let revocation_base_key = key_step!(b"revocation base key", funding_key);
397 let payment_base_key = key_step!(b"payment base key", revocation_base_key);
398 let delayed_payment_base_key = key_step!(b"delayed payment base key", payment_base_key);
399 let htlc_base_key = key_step!(b"HTLC base key", delayed_payment_base_key);
401 InMemoryChannelKeys {
405 delayed_payment_base_key,
408 remote_channel_pubkeys: None,
409 channel_value_satoshis,
413 fn get_onion_rand(&self) -> (SecretKey, [u8; 32]) {
414 let mut sha = self.unique_start.clone();
416 let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel);
417 let child_privkey = self.session_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
418 sha.input(&child_privkey.private_key.key[..]);
420 let mut rng_seed = sha.clone();
421 // Not exactly the most ideal construction, but the second value will get fed into
422 // ChaCha so it is another step harder to break.
423 rng_seed.input(b"RNG Seed Salt");
424 sha.input(b"Session Key Salt");
425 (SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted"),
426 Sha256::from_engine(rng_seed).into_inner())
429 fn get_channel_id(&self) -> [u8; 32] {
430 let mut sha = self.unique_start.clone();
432 let child_ix = self.channel_id_child_index.fetch_add(1, Ordering::AcqRel);
433 let child_privkey = self.channel_id_master_key.ckd_priv(&self.secp_ctx, ChildNumber::from_hardened_idx(child_ix as u32).expect("key space exhausted")).expect("Your RNG is busted");
434 sha.input(&child_privkey.private_key.key[..]);
436 (Sha256::from_engine(sha).into_inner())