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};
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) -> 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>(&self, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, absolute_fee: 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, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, 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, ()>;
163 /// A simple implementation of ChannelKeys that just keeps the private keys in memory.
164 pub struct InMemoryChannelKeys {
165 /// Private key of anchor tx
166 pub funding_key: SecretKey,
167 /// Local secret key for blinded revocation pubkey
168 pub revocation_base_key: SecretKey,
169 /// Local secret key used in commitment tx htlc outputs
170 pub payment_base_key: SecretKey,
171 /// Local secret key used in HTLC tx
172 pub delayed_payment_base_key: SecretKey,
173 /// Local htlc secret key used in commitment tx htlc outputs
174 pub htlc_base_key: SecretKey,
176 pub commitment_seed: [u8; 32],
179 impl ChannelKeys for InMemoryChannelKeys {
180 fn funding_key(&self) -> &SecretKey { &self.funding_key }
181 fn revocation_base_key(&self) -> &SecretKey { &self.revocation_base_key }
182 fn payment_base_key(&self) -> &SecretKey { &self.payment_base_key }
183 fn delayed_payment_base_key(&self) -> &SecretKey { &self.delayed_payment_base_key }
184 fn htlc_base_key(&self) -> &SecretKey { &self.htlc_base_key }
185 fn commitment_seed(&self) -> &[u8; 32] { &self.commitment_seed }
187 fn sign_remote_commitment<T: secp256k1::Signing>(&self, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1<T>) -> Result<(Signature, Vec<Signature>), ()> {
188 if commitment_tx.input.len() != 1 { return Err(()); }
189 let commitment_sighash = hash_to_message!(&bip143::SighashComponents::new(&commitment_tx).sighash_all(&commitment_tx.input[0], &channel_funding_redeemscript, channel_value_satoshis)[..]);
190 let commitment_sig = secp_ctx.sign(&commitment_sighash, &self.funding_key);
192 let commitment_txid = commitment_tx.txid();
194 let mut htlc_sigs = Vec::with_capacity(htlcs.len());
195 for ref htlc in htlcs {
196 if let Some(_) = htlc.transaction_output_index {
197 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);
198 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys);
199 let htlc_sighash = hash_to_message!(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]);
200 let our_htlc_key = match chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key) {
202 Err(_) => return Err(()),
204 htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &our_htlc_key));
208 Ok((commitment_sig, htlc_sigs))
211 fn sign_closing_transaction<T: secp256k1::Signing>(&self, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
212 if closing_tx.input.len() != 1 { return Err(()); }
213 if closing_tx.input[0].witness.len() != 0 { return Err(()); }
214 if closing_tx.output.len() > 2 { return Err(()); }
216 let sighash = hash_to_message!(&bip143::SighashComponents::new(closing_tx)
217 .sighash_all(&closing_tx.input[0], &channel_funding_redeemscript, channel_value_satoshis)[..]);
218 Ok(secp_ctx.sign(&sighash, &self.funding_key))
221 fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
222 let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
223 Ok(secp_ctx.sign(&msghash, &self.funding_key))
227 impl_writeable!(InMemoryChannelKeys, 0, {
231 delayed_payment_base_key,
236 /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key
237 /// and derives keys from that.
239 /// Your node_id is seed/0'
240 /// ChannelMonitor closes may use seed/1'
241 /// Cooperative closes may use seed/2'
242 /// The two close keys may be needed to claim on-chain funds!
243 pub struct KeysManager {
244 secp_ctx: Secp256k1<secp256k1::SignOnly>,
245 node_secret: SecretKey,
246 destination_script: Script,
247 shutdown_pubkey: PublicKey,
248 channel_master_key: ExtendedPrivKey,
249 channel_child_index: AtomicUsize,
250 session_master_key: ExtendedPrivKey,
251 session_child_index: AtomicUsize,
252 channel_id_master_key: ExtendedPrivKey,
253 channel_id_child_index: AtomicUsize,
255 unique_start: Sha256State,
260 /// Constructs a KeysManager from a 32-byte seed. If the seed is in some way biased (eg your
261 /// RNG is busted) this may panic (but more importantly, you will possibly lose funds).
262 /// starting_time isn't strictly required to actually be a time, but it must absolutely,
263 /// without a doubt, be unique to this instance. ie if you start multiple times with the same
264 /// seed, starting_time must be unique to each run. Thus, the easiest way to achieve this is to
265 /// simply use the current time (with very high precision).
267 /// The seed MUST be backed up safely prior to use so that the keys can be re-created, however,
268 /// obviously, starting_time should be unique every time you reload the library - it is only
269 /// used to generate new ephemeral key data (which will be stored by the individual channel if
272 /// Note that the seed is required to recover certain on-chain funds independent of
273 /// ChannelMonitor data, though a current copy of ChannelMonitor data is also required for any
274 /// channel, and some on-chain during-closing funds.
276 /// Note that until the 0.1 release there is no guarantee of backward compatibility between
277 /// versions. Once the library is more fully supported, the docs will be updated to include a
278 /// detailed description of the guarantee.
279 pub fn new(seed: &[u8; 32], network: Network, logger: Arc<Logger>, starting_time_secs: u64, starting_time_nanos: u32) -> KeysManager {
280 let secp_ctx = Secp256k1::signing_only();
281 match ExtendedPrivKey::new_master(network.clone(), seed) {
283 let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key.key;
284 let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1).unwrap()) {
285 Ok(destination_key) => {
286 let pubkey_hash160 = Hash160::hash(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.key.serialize()[..]);
287 Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
288 .push_slice(&pubkey_hash160.into_inner())
291 Err(_) => panic!("Your RNG is busted"),
293 let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2).unwrap()) {
294 Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key.key,
295 Err(_) => panic!("Your RNG is busted"),
297 let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3).unwrap()).expect("Your RNG is busted");
298 let session_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4).unwrap()).expect("Your RNG is busted");
299 let channel_id_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(5).unwrap()).expect("Your RNG is busted");
301 let mut unique_start = Sha256::engine();
302 unique_start.input(&byte_utils::be64_to_array(starting_time_secs));
303 unique_start.input(&byte_utils::be32_to_array(starting_time_nanos));
304 unique_start.input(seed);
312 channel_child_index: AtomicUsize::new(0),
314 session_child_index: AtomicUsize::new(0),
315 channel_id_master_key,
316 channel_id_child_index: AtomicUsize::new(0),
322 Err(_) => panic!("Your rng is busted"),
327 impl KeysInterface for KeysManager {
328 type ChanKeySigner = InMemoryChannelKeys;
330 fn get_node_secret(&self) -> SecretKey {
331 self.node_secret.clone()
334 fn get_destination_script(&self) -> Script {
335 self.destination_script.clone()
338 fn get_shutdown_pubkey(&self) -> PublicKey {
339 self.shutdown_pubkey.clone()
342 fn get_channel_keys(&self, _inbound: bool) -> InMemoryChannelKeys {
343 // We only seriously intend to rely on the channel_master_key for true secure
344 // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
345 // starting_time provided in the constructor) to be unique.
346 let mut sha = self.unique_start.clone();
348 let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
349 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");
350 sha.input(&child_privkey.private_key.key[..]);
352 let seed = Sha256::from_engine(sha).into_inner();
354 let commitment_seed = {
355 let mut sha = Sha256::engine();
357 sha.input(&b"commitment seed"[..]);
358 Sha256::from_engine(sha).into_inner()
360 macro_rules! key_step {
361 ($info: expr, $prev_key: expr) => {{
362 let mut sha = Sha256::engine();
364 sha.input(&$prev_key[..]);
365 sha.input(&$info[..]);
366 SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("SHA-256 is busted")
369 let funding_key = key_step!(b"funding key", commitment_seed);
370 let revocation_base_key = key_step!(b"revocation base key", funding_key);
371 let payment_base_key = key_step!(b"payment base key", revocation_base_key);
372 let delayed_payment_base_key = key_step!(b"delayed payment base key", payment_base_key);
373 let htlc_base_key = key_step!(b"HTLC base key", delayed_payment_base_key);
375 InMemoryChannelKeys {
379 delayed_payment_base_key,
385 fn get_onion_rand(&self) -> (SecretKey, [u8; 32]) {
386 let mut sha = self.unique_start.clone();
388 let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel);
389 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");
390 sha.input(&child_privkey.private_key.key[..]);
392 let mut rng_seed = sha.clone();
393 // Not exactly the most ideal construction, but the second value will get fed into
394 // ChaCha so it is another step harder to break.
395 rng_seed.input(b"RNG Seed Salt");
396 sha.input(b"Session Key Salt");
397 (SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted"),
398 Sha256::from_engine(rng_seed).into_inner())
401 fn get_channel_id(&self) -> [u8; 32] {
402 let mut sha = self.unique_start.clone();
404 let child_ix = self.channel_id_child_index.fetch_add(1, Ordering::AcqRel);
405 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");
406 sha.input(&child_privkey.private_key.key[..]);
408 (Sha256::from_engine(sha).into_inner())