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[rust-lightning] / lightning / src / chain / keysinterface.rs
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.
4
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;
11
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::hash_types::WPubkeyHash;
17
18 use bitcoin::secp256k1::key::{SecretKey, PublicKey};
19 use bitcoin::secp256k1::{Secp256k1, Signature, Signing};
20 use bitcoin::secp256k1;
21
22 use util::byte_utils;
23 use util::logger::Logger;
24 use util::ser::{Writeable, Writer, Readable};
25
26 use ln::chan_utils;
27 use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys, LocalCommitmentTransaction};
28 use ln::msgs;
29
30 use std::sync::Arc;
31 use std::sync::atomic::{AtomicUsize, Ordering};
32 use std::io::Error;
33 use ln::msgs::DecodeError;
34
35 /// When on-chain outputs are created by rust-lightning (which our counterparty is not able to
36 /// claim at any point in the future) an event is generated which you must track and be able to
37 /// spend on-chain. The information needed to do this is provided in this enum, including the
38 /// outpoint describing which txid and output index is available, the full output which exists at
39 /// that txid/index, and any keys or other information required to sign.
40 #[derive(Clone, PartialEq)]
41 pub enum SpendableOutputDescriptor {
42         /// An output to a script which was provided via KeysInterface, thus you should already know
43         /// how to spend it. No keys are provided as rust-lightning was never given any keys - only the
44         /// script_pubkey as it appears in the output.
45         /// These may include outputs from a transaction punishing our counterparty or claiming an HTLC
46         /// on-chain using the payment preimage or after it has timed out.
47         StaticOutput {
48                 /// The outpoint which is spendable
49                 outpoint: OutPoint,
50                 /// The output which is referenced by the given outpoint.
51                 output: TxOut,
52         },
53         /// An output to a P2WSH script which can be spent with a single signature after a CSV delay.
54         /// The private key which should be used to sign the transaction is provided, as well as the
55         /// full witness redeemScript which is hashed in the output script_pubkey.
56         /// The witness in the spending input should be:
57         /// <BIP 143 signature generated with the given key> <empty vector> (MINIMALIF standard rule)
58         /// <witness_script as provided>
59         /// Note that the nSequence field in the input must be set to_self_delay (which corresponds to
60         /// the transaction not being broadcastable until at least to_self_delay blocks after the input
61         /// confirms).
62         /// These are generally the result of a "revocable" output to us, spendable only by us unless
63         /// it is an output from us having broadcast an old state (which should never happen).
64         DynamicOutputP2WSH {
65                 /// The outpoint which is spendable
66                 outpoint: OutPoint,
67                 /// The secret key which must be used to sign the spending transaction
68                 key: SecretKey,
69                 /// The witness redeemScript which is hashed to create the script_pubkey in the given output
70                 witness_script: Script,
71                 /// The nSequence value which must be set in the spending input to satisfy the OP_CSV in
72                 /// the witness_script.
73                 to_self_delay: u16,
74                 /// The output which is referenced by the given outpoint
75                 output: TxOut,
76         },
77         // TODO: Note that because key is now static and exactly what is provided by us, we should drop
78         // this in favor of StaticOutput:
79         /// An output to a P2WPKH, spendable exclusively by the given private key.
80         /// The witness in the spending input, is, thus, simply:
81         /// <BIP 143 signature generated with the given key> <public key derived from the given key>
82         /// These are generally the result of our counterparty having broadcast the current state,
83         /// allowing us to claim the non-HTLC-encumbered outputs immediately.
84         DynamicOutputP2WPKH {
85                 /// The outpoint which is spendable
86                 outpoint: OutPoint,
87                 /// The secret key which must be used to sign the spending transaction
88                 key: SecretKey,
89                 /// The output which is reference by the given outpoint
90                 output: TxOut,
91         }
92 }
93
94 impl Writeable for SpendableOutputDescriptor {
95         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
96                 match self {
97                         &SpendableOutputDescriptor::StaticOutput { ref outpoint, ref output } => {
98                                 0u8.write(writer)?;
99                                 outpoint.write(writer)?;
100                                 output.write(writer)?;
101                         },
102                         &SpendableOutputDescriptor::DynamicOutputP2WSH { ref outpoint, ref key, ref witness_script, ref to_self_delay, ref output } => {
103                                 1u8.write(writer)?;
104                                 outpoint.write(writer)?;
105                                 key.write(writer)?;
106                                 witness_script.write(writer)?;
107                                 to_self_delay.write(writer)?;
108                                 output.write(writer)?;
109                         },
110                         &SpendableOutputDescriptor::DynamicOutputP2WPKH { ref outpoint, ref key, ref output } => {
111                                 2u8.write(writer)?;
112                                 outpoint.write(writer)?;
113                                 key.write(writer)?;
114                                 output.write(writer)?;
115                         },
116                 }
117                 Ok(())
118         }
119 }
120
121 impl Readable for SpendableOutputDescriptor {
122         fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
123                 match Readable::read(reader)? {
124                         0u8 => Ok(SpendableOutputDescriptor::StaticOutput {
125                                 outpoint: Readable::read(reader)?,
126                                 output: Readable::read(reader)?,
127                         }),
128                         1u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WSH {
129                                 outpoint: Readable::read(reader)?,
130                                 key: Readable::read(reader)?,
131                                 witness_script: Readable::read(reader)?,
132                                 to_self_delay: Readable::read(reader)?,
133                                 output: Readable::read(reader)?,
134                         }),
135                         2u8 => Ok(SpendableOutputDescriptor::DynamicOutputP2WPKH {
136                                 outpoint: Readable::read(reader)?,
137                                 key: Readable::read(reader)?,
138                                 output: Readable::read(reader)?,
139                         }),
140                         _ => Err(DecodeError::InvalidValue),
141                 }
142         }
143 }
144
145 /// A trait to describe an object which can get user secrets and key material.
146 pub trait KeysInterface: Send + Sync {
147         /// A type which implements ChannelKeys which will be returned by get_channel_keys.
148         type ChanKeySigner : ChannelKeys;
149
150         /// Get node secret key (aka node_id or network_key)
151         fn get_node_secret(&self) -> SecretKey;
152         /// Get destination redeemScript to encumber static protocol exit points.
153         fn get_destination_script(&self) -> Script;
154         /// Get shutdown_pubkey to use as PublicKey at channel closure
155         fn get_shutdown_pubkey(&self) -> PublicKey;
156         /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you
157         /// restarted with some stale data!
158         fn get_channel_keys(&self, inbound: bool, channel_value_satoshis: u64) -> Self::ChanKeySigner;
159         /// Get a secret and PRNG seed for construting an onion packet
160         fn get_onion_rand(&self) -> (SecretKey, [u8; 32]);
161         /// Get a unique temporary channel id. Channels will be referred to by this until the funding
162         /// transaction is created, at which point they will use the outpoint in the funding
163         /// transaction.
164         fn get_channel_id(&self) -> [u8; 32];
165 }
166
167 /// Set of lightning keys needed to operate a channel as described in BOLT 3.
168 ///
169 /// Signing services could be implemented on a hardware wallet. In this case,
170 /// the current ChannelKeys would be a front-end on top of a communication
171 /// channel connected to your secure device and lightning key material wouldn't
172 /// reside on a hot server. Nevertheless, a this deployment would still need
173 /// to trust the ChannelManager to avoid loss of funds as this latest component
174 /// could ask to sign commitment transaction with HTLCs paying to attacker pubkeys.
175 ///
176 /// A more secure iteration would be to use hashlock (or payment points) to pair
177 /// invoice/incoming HTLCs with outgoing HTLCs to implement a no-trust-ChannelManager
178 /// at the price of more state and computation on the hardware wallet side. In the future,
179 /// we are looking forward to design such interface.
180 ///
181 /// In any case, ChannelMonitor or fallback watchtowers are always going to be trusted
182 /// to act, as liveness and breach reply correctness are always going to be hard requirements
183 /// of LN security model, orthogonal of key management issues.
184 ///
185 /// If you're implementing a custom signer, you almost certainly want to implement
186 /// Readable/Writable to serialize out a unique reference to this set of keys so
187 /// that you can serialize the full ChannelManager object.
188 ///
189 // (TODO: We shouldn't require that, and should have an API to get them at deser time, due mostly
190 // to the possibility of reentrancy issues by calling the user's code during our deserialization
191 // routine).
192 // TODO: We should remove Clone by instead requesting a new ChannelKeys copy when we create
193 // ChannelMonitors instead of expecting to clone the one out of the Channel into the monitors.
194 pub trait ChannelKeys : Send+Clone {
195         /// Gets the private key for the anchor tx
196         fn funding_key<'a>(&'a self) -> &'a SecretKey;
197         /// Gets the local secret key for blinded revocation pubkey
198         fn revocation_base_key<'a>(&'a self) -> &'a SecretKey;
199         /// Gets the local secret key used in to_remote output of remote commitment tx
200         /// (and also as part of obscured commitment number)
201         fn payment_base_key<'a>(&'a self) -> &'a SecretKey;
202         /// Gets the local secret key used in HTLC-Success/HTLC-Timeout txn and to_local output
203         fn delayed_payment_base_key<'a>(&'a self) -> &'a SecretKey;
204         /// Gets the local htlc secret key used in commitment tx htlc outputs
205         fn htlc_base_key<'a>(&'a self) -> &'a SecretKey;
206         /// Gets the commitment seed
207         fn commitment_seed<'a>(&'a self) -> &'a [u8; 32];
208         /// Gets the local channel public keys and basepoints
209         fn pubkeys<'a>(&'a self) -> &'a ChannelPublicKeys;
210
211         /// Create a signature for a remote commitment transaction and associated HTLC transactions.
212         ///
213         /// Note that if signing fails or is rejected, the channel will be force-closed.
214         //
215         // TODO: Document the things someone using this interface should enforce before signing.
216         // TODO: Add more input vars to enable better checking (preferably removing commitment_tx and
217         // making the callee generate it via some util function we expose)!
218         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>), ()>;
219
220         /// Create a signature for a local commitment transaction. This will only ever be called with
221         /// the same local_commitment_tx (or a copy thereof), though there are currently no guarantees
222         /// that it will not be called multiple times.
223         //
224         // TODO: Document the things someone using this interface should enforce before signing.
225         // TODO: Add more input vars to enable better checking (preferably removing commitment_tx and
226         fn sign_local_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
227
228         /// Same as sign_local_commitment, but exists only for tests to get access to local commitment
229         /// transactions which will be broadcasted later, after the channel has moved on to a newer
230         /// state. Thus, needs its own method as sign_local_commitment may enforce that we only ever
231         /// get called once.
232         #[cfg(test)]
233         fn unsafe_sign_local_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
234
235         /// Create a signature for each HTLC transaction spending a local commitment transaction.
236         ///
237         /// Unlike sign_local_commitment, this may be called multiple times with *different*
238         /// local_commitment_tx values. While this will never be called with a revoked
239         /// local_commitment_tx, it is possible that it is called with the second-latest
240         /// local_commitment_tx (only if we haven't yet revoked it) if some watchtower/secondary
241         /// ChannelMonitor decided to broadcast before it had been updated to the latest.
242         ///
243         /// Either an Err should be returned, or a Vec with one entry for each HTLC which exists in
244         /// local_commitment_tx. For those HTLCs which have transaction_output_index set to None
245         /// (implying they were considered dust at the time the commitment transaction was negotiated),
246         /// a corresponding None should be included in the return value. All other positions in the
247         /// return value must contain a signature.
248         fn sign_local_commitment_htlc_transactions<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, local_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Vec<Option<Signature>>, ()>;
249
250         /// Create a signature for a (proposed) closing transaction.
251         ///
252         /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have
253         /// chosen to forgo their output as dust.
254         fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
255
256         /// Signs a channel announcement message with our funding key, proving it comes from one
257         /// of the channel participants.
258         ///
259         /// Note that if this fails or is rejected, the channel will not be publicly announced and
260         /// our counterparty may (though likely will not) close the channel on us for violating the
261         /// protocol.
262         fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()>;
263
264         /// Set the remote channel basepoints.  This is done immediately on incoming channels
265         /// and as soon as the channel is accepted on outgoing channels.
266         ///
267         /// Will be called before any signatures are applied.
268         fn set_remote_channel_pubkeys(&mut self, channel_points: &ChannelPublicKeys);
269 }
270
271 #[derive(Clone)]
272 /// A simple implementation of ChannelKeys that just keeps the private keys in memory.
273 pub struct InMemoryChannelKeys {
274         /// Private key of anchor tx
275         funding_key: SecretKey,
276         /// Local secret key for blinded revocation pubkey
277         revocation_base_key: SecretKey,
278         /// Local secret key used in commitment tx htlc outputs
279         payment_base_key: SecretKey,
280         /// Local secret key used in HTLC tx
281         delayed_payment_base_key: SecretKey,
282         /// Local htlc secret key used in commitment tx htlc outputs
283         htlc_base_key: SecretKey,
284         /// Commitment seed
285         commitment_seed: [u8; 32],
286         /// Local public keys and basepoints
287         pub(crate) local_channel_pubkeys: ChannelPublicKeys,
288         /// Remote public keys and base points
289         pub(crate) remote_channel_pubkeys: Option<ChannelPublicKeys>,
290         /// The total value of this channel
291         channel_value_satoshis: u64,
292 }
293
294 impl InMemoryChannelKeys {
295         /// Create a new InMemoryChannelKeys
296         pub fn new<C: Signing>(
297                 secp_ctx: &Secp256k1<C>,
298                 funding_key: SecretKey,
299                 revocation_base_key: SecretKey,
300                 payment_base_key: SecretKey,
301                 delayed_payment_base_key: SecretKey,
302                 htlc_base_key: SecretKey,
303                 commitment_seed: [u8; 32],
304                 channel_value_satoshis: u64) -> InMemoryChannelKeys {
305                 let local_channel_pubkeys =
306                         InMemoryChannelKeys::make_local_keys(secp_ctx, &funding_key, &revocation_base_key,
307                                                              &payment_base_key, &delayed_payment_base_key,
308                                                              &htlc_base_key);
309                 InMemoryChannelKeys {
310                         funding_key,
311                         revocation_base_key,
312                         payment_base_key,
313                         delayed_payment_base_key,
314                         htlc_base_key,
315                         commitment_seed,
316                         channel_value_satoshis,
317                         local_channel_pubkeys,
318                         remote_channel_pubkeys: None,
319                 }
320         }
321
322         fn make_local_keys<C: Signing>(secp_ctx: &Secp256k1<C>,
323                                        funding_key: &SecretKey,
324                                        revocation_base_key: &SecretKey,
325                                        payment_base_key: &SecretKey,
326                                        delayed_payment_base_key: &SecretKey,
327                                        htlc_base_key: &SecretKey) -> ChannelPublicKeys {
328                 let from_secret = |s: &SecretKey| PublicKey::from_secret_key(secp_ctx, s);
329                 ChannelPublicKeys {
330                         funding_pubkey: from_secret(&funding_key),
331                         revocation_basepoint: from_secret(&revocation_base_key),
332                         payment_basepoint: from_secret(&payment_base_key),
333                         delayed_payment_basepoint: from_secret(&delayed_payment_base_key),
334                         htlc_basepoint: from_secret(&htlc_base_key),
335                 }
336         }
337 }
338
339 impl ChannelKeys for InMemoryChannelKeys {
340         fn funding_key(&self) -> &SecretKey { &self.funding_key }
341         fn revocation_base_key(&self) -> &SecretKey { &self.revocation_base_key }
342         fn payment_base_key(&self) -> &SecretKey { &self.payment_base_key }
343         fn delayed_payment_base_key(&self) -> &SecretKey { &self.delayed_payment_base_key }
344         fn htlc_base_key(&self) -> &SecretKey { &self.htlc_base_key }
345         fn commitment_seed(&self) -> &[u8; 32] { &self.commitment_seed }
346         fn pubkeys<'a>(&'a self) -> &'a ChannelPublicKeys { &self.local_channel_pubkeys }
347
348         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>), ()> {
349                 if commitment_tx.input.len() != 1 { return Err(()); }
350
351                 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
352                 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
353                 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
354
355                 let commitment_sighash = hash_to_message!(&bip143::SighashComponents::new(&commitment_tx).sighash_all(&commitment_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
356                 let commitment_sig = secp_ctx.sign(&commitment_sighash, &self.funding_key);
357
358                 let commitment_txid = commitment_tx.txid();
359
360                 let mut htlc_sigs = Vec::with_capacity(htlcs.len());
361                 for ref htlc in htlcs {
362                         if let Some(_) = htlc.transaction_output_index {
363                                 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);
364                                 let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys);
365                                 let htlc_sighash = hash_to_message!(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]);
366                                 let our_htlc_key = match chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key) {
367                                         Ok(s) => s,
368                                         Err(_) => return Err(()),
369                                 };
370                                 htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &our_htlc_key));
371                         }
372                 }
373
374                 Ok((commitment_sig, htlc_sigs))
375         }
376
377         fn sign_local_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
378                 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
379                 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
380                 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
381
382                 Ok(local_commitment_tx.get_local_sig(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
383         }
384
385         #[cfg(test)]
386         fn unsafe_sign_local_commitment<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
387                 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
388                 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
389                 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
390
391                 Ok(local_commitment_tx.get_local_sig(&self.funding_key, &channel_funding_redeemscript, self.channel_value_satoshis, secp_ctx))
392         }
393
394         fn sign_local_commitment_htlc_transactions<T: secp256k1::Signing + secp256k1::Verification>(&self, local_commitment_tx: &LocalCommitmentTransaction, local_csv: u16, secp_ctx: &Secp256k1<T>) -> Result<Vec<Option<Signature>>, ()> {
395                 local_commitment_tx.get_htlc_sigs(&self.htlc_base_key, local_csv, secp_ctx)
396         }
397
398         fn sign_closing_transaction<T: secp256k1::Signing>(&self, closing_tx: &Transaction, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
399                 if closing_tx.input.len() != 1 { return Err(()); }
400                 if closing_tx.input[0].witness.len() != 0 { return Err(()); }
401                 if closing_tx.output.len() > 2 { return Err(()); }
402
403                 let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing");
404                 let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key);
405                 let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey);
406
407                 let sighash = hash_to_message!(&bip143::SighashComponents::new(closing_tx)
408                         .sighash_all(&closing_tx.input[0], &channel_funding_redeemscript, self.channel_value_satoshis)[..]);
409                 Ok(secp_ctx.sign(&sighash, &self.funding_key))
410         }
411
412         fn sign_channel_announcement<T: secp256k1::Signing>(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1<T>) -> Result<Signature, ()> {
413                 let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]);
414                 Ok(secp_ctx.sign(&msghash, &self.funding_key))
415         }
416
417         fn set_remote_channel_pubkeys(&mut self, channel_pubkeys: &ChannelPublicKeys) {
418                 assert!(self.remote_channel_pubkeys.is_none(), "Already set remote channel pubkeys");
419                 self.remote_channel_pubkeys = Some(channel_pubkeys.clone());
420         }
421 }
422
423 impl Writeable for InMemoryChannelKeys {
424         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
425                 self.funding_key.write(writer)?;
426                 self.revocation_base_key.write(writer)?;
427                 self.payment_base_key.write(writer)?;
428                 self.delayed_payment_base_key.write(writer)?;
429                 self.htlc_base_key.write(writer)?;
430                 self.commitment_seed.write(writer)?;
431                 self.remote_channel_pubkeys.write(writer)?;
432                 self.channel_value_satoshis.write(writer)?;
433
434                 Ok(())
435         }
436 }
437
438 impl Readable for InMemoryChannelKeys {
439         fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
440                 let funding_key = Readable::read(reader)?;
441                 let revocation_base_key = Readable::read(reader)?;
442                 let payment_base_key = Readable::read(reader)?;
443                 let delayed_payment_base_key = Readable::read(reader)?;
444                 let htlc_base_key = Readable::read(reader)?;
445                 let commitment_seed = Readable::read(reader)?;
446                 let remote_channel_pubkeys = Readable::read(reader)?;
447                 let channel_value_satoshis = Readable::read(reader)?;
448                 let secp_ctx = Secp256k1::signing_only();
449                 let local_channel_pubkeys =
450                         InMemoryChannelKeys::make_local_keys(&secp_ctx, &funding_key, &revocation_base_key,
451                                                              &payment_base_key, &delayed_payment_base_key,
452                                                              &htlc_base_key);
453
454                 Ok(InMemoryChannelKeys {
455                         funding_key,
456                         revocation_base_key,
457                         payment_base_key,
458                         delayed_payment_base_key,
459                         htlc_base_key,
460                         commitment_seed,
461                         channel_value_satoshis,
462                         local_channel_pubkeys,
463                         remote_channel_pubkeys
464                 })
465         }
466 }
467
468 /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key
469 /// and derives keys from that.
470 ///
471 /// Your node_id is seed/0'
472 /// ChannelMonitor closes may use seed/1'
473 /// Cooperative closes may use seed/2'
474 /// The two close keys may be needed to claim on-chain funds!
475 pub struct KeysManager {
476         secp_ctx: Secp256k1<secp256k1::SignOnly>,
477         node_secret: SecretKey,
478         destination_script: Script,
479         shutdown_pubkey: PublicKey,
480         channel_master_key: ExtendedPrivKey,
481         channel_child_index: AtomicUsize,
482         session_master_key: ExtendedPrivKey,
483         session_child_index: AtomicUsize,
484         channel_id_master_key: ExtendedPrivKey,
485         channel_id_child_index: AtomicUsize,
486
487         unique_start: Sha256State,
488         logger: Arc<Logger>,
489 }
490
491 impl KeysManager {
492         /// Constructs a KeysManager from a 32-byte seed. If the seed is in some way biased (eg your
493         /// RNG is busted) this may panic (but more importantly, you will possibly lose funds).
494         /// starting_time isn't strictly required to actually be a time, but it must absolutely,
495         /// without a doubt, be unique to this instance. ie if you start multiple times with the same
496         /// seed, starting_time must be unique to each run. Thus, the easiest way to achieve this is to
497         /// simply use the current time (with very high precision).
498         ///
499         /// The seed MUST be backed up safely prior to use so that the keys can be re-created, however,
500         /// obviously, starting_time should be unique every time you reload the library - it is only
501         /// used to generate new ephemeral key data (which will be stored by the individual channel if
502         /// necessary).
503         ///
504         /// Note that the seed is required to recover certain on-chain funds independent of
505         /// ChannelMonitor data, though a current copy of ChannelMonitor data is also required for any
506         /// channel, and some on-chain during-closing funds.
507         ///
508         /// Note that until the 0.1 release there is no guarantee of backward compatibility between
509         /// versions. Once the library is more fully supported, the docs will be updated to include a
510         /// detailed description of the guarantee.
511         pub fn new(seed: &[u8; 32], network: Network, logger: Arc<Logger>, starting_time_secs: u64, starting_time_nanos: u32) -> KeysManager {
512                 let secp_ctx = Secp256k1::signing_only();
513                 match ExtendedPrivKey::new_master(network.clone(), seed) {
514                         Ok(master_key) => {
515                                 let node_secret = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(0).unwrap()).expect("Your RNG is busted").private_key.key;
516                                 let destination_script = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(1).unwrap()) {
517                                         Ok(destination_key) => {
518                                                 let wpubkey_hash = WPubkeyHash::hash(&ExtendedPubKey::from_private(&secp_ctx, &destination_key).public_key.to_bytes());
519                                                 Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
520                                                               .push_slice(&wpubkey_hash.into_inner())
521                                                               .into_script()
522                                         },
523                                         Err(_) => panic!("Your RNG is busted"),
524                                 };
525                                 let shutdown_pubkey = match master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(2).unwrap()) {
526                                         Ok(shutdown_key) => ExtendedPubKey::from_private(&secp_ctx, &shutdown_key).public_key.key,
527                                         Err(_) => panic!("Your RNG is busted"),
528                                 };
529                                 let channel_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(3).unwrap()).expect("Your RNG is busted");
530                                 let session_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(4).unwrap()).expect("Your RNG is busted");
531                                 let channel_id_master_key = master_key.ckd_priv(&secp_ctx, ChildNumber::from_hardened_idx(5).unwrap()).expect("Your RNG is busted");
532
533                                 let mut unique_start = Sha256::engine();
534                                 unique_start.input(&byte_utils::be64_to_array(starting_time_secs));
535                                 unique_start.input(&byte_utils::be32_to_array(starting_time_nanos));
536                                 unique_start.input(seed);
537
538                                 KeysManager {
539                                         secp_ctx,
540                                         node_secret,
541                                         destination_script,
542                                         shutdown_pubkey,
543                                         channel_master_key,
544                                         channel_child_index: AtomicUsize::new(0),
545                                         session_master_key,
546                                         session_child_index: AtomicUsize::new(0),
547                                         channel_id_master_key,
548                                         channel_id_child_index: AtomicUsize::new(0),
549
550                                         unique_start,
551                                         logger,
552                                 }
553                         },
554                         Err(_) => panic!("Your rng is busted"),
555                 }
556         }
557 }
558
559 impl KeysInterface for KeysManager {
560         type ChanKeySigner = InMemoryChannelKeys;
561
562         fn get_node_secret(&self) -> SecretKey {
563                 self.node_secret.clone()
564         }
565
566         fn get_destination_script(&self) -> Script {
567                 self.destination_script.clone()
568         }
569
570         fn get_shutdown_pubkey(&self) -> PublicKey {
571                 self.shutdown_pubkey.clone()
572         }
573
574         fn get_channel_keys(&self, _inbound: bool, channel_value_satoshis: u64) -> InMemoryChannelKeys {
575                 // We only seriously intend to rely on the channel_master_key for true secure
576                 // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie
577                 // starting_time provided in the constructor) to be unique.
578                 let mut sha = self.unique_start.clone();
579
580                 let child_ix = self.channel_child_index.fetch_add(1, Ordering::AcqRel);
581                 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");
582                 sha.input(&child_privkey.private_key.key[..]);
583
584                 let seed = Sha256::from_engine(sha).into_inner();
585
586                 let commitment_seed = {
587                         let mut sha = Sha256::engine();
588                         sha.input(&seed);
589                         sha.input(&b"commitment seed"[..]);
590                         Sha256::from_engine(sha).into_inner()
591                 };
592                 macro_rules! key_step {
593                         ($info: expr, $prev_key: expr) => {{
594                                 let mut sha = Sha256::engine();
595                                 sha.input(&seed);
596                                 sha.input(&$prev_key[..]);
597                                 sha.input(&$info[..]);
598                                 SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("SHA-256 is busted")
599                         }}
600                 }
601                 let funding_key = key_step!(b"funding key", commitment_seed);
602                 let revocation_base_key = key_step!(b"revocation base key", funding_key);
603                 let payment_base_key = key_step!(b"payment base key", revocation_base_key);
604                 let delayed_payment_base_key = key_step!(b"delayed payment base key", payment_base_key);
605                 let htlc_base_key = key_step!(b"HTLC base key", delayed_payment_base_key);
606
607                 InMemoryChannelKeys::new(
608                         &self.secp_ctx,
609                         funding_key,
610                         revocation_base_key,
611                         payment_base_key,
612                         delayed_payment_base_key,
613                         htlc_base_key,
614                         commitment_seed,
615                         channel_value_satoshis
616                 )
617         }
618
619         fn get_onion_rand(&self) -> (SecretKey, [u8; 32]) {
620                 let mut sha = self.unique_start.clone();
621
622                 let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel);
623                 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");
624                 sha.input(&child_privkey.private_key.key[..]);
625
626                 let mut rng_seed = sha.clone();
627                 // Not exactly the most ideal construction, but the second value will get fed into
628                 // ChaCha so it is another step harder to break.
629                 rng_seed.input(b"RNG Seed Salt");
630                 sha.input(b"Session Key Salt");
631                 (SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted"),
632                 Sha256::from_engine(rng_seed).into_inner())
633         }
634
635         fn get_channel_id(&self) -> [u8; 32] {
636                 let mut sha = self.unique_start.clone();
637
638                 let child_ix = self.channel_id_child_index.fetch_add(1, Ordering::AcqRel);
639                 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");
640                 sha.input(&child_privkey.private_key.key[..]);
641
642                 Sha256::from_engine(sha).into_inner()
643         }
644 }