X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fchain%2Fkeysinterface.rs;h=689a16603743e228ffff64dfba9ea710474fdc43;hb=9a0211543762ae15ce4a0b7cb5aa3cf295a4b61f;hp=73d320b0f69a6e123deb20d1f6261960d57d2680;hpb=88fef649b15fa030cb91de76d58346a0bc408834;p=rust-lightning diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs index 73d320b0..689a1660 100644 --- a/lightning/src/chain/keysinterface.rs +++ b/lightning/src/chain/keysinterface.rs @@ -2,23 +2,30 @@ //! spendable on-chain outputs which the user owns and is responsible for using just as any other //! on-chain output which is theirs. -use bitcoin::blockdata::transaction::{OutPoint, TxOut}; +use bitcoin::blockdata::transaction::{Transaction, OutPoint, TxOut}; use bitcoin::blockdata::script::{Script, Builder}; use bitcoin::blockdata::opcodes; use bitcoin::network::constants::Network; use bitcoin::util::bip32::{ExtendedPrivKey, ExtendedPubKey, ChildNumber}; +use bitcoin::util::bip143; use bitcoin_hashes::{Hash, HashEngine}; use bitcoin_hashes::sha256::HashEngine as Sha256State; use bitcoin_hashes::sha256::Hash as Sha256; +use bitcoin_hashes::sha256d::Hash as Sha256dHash; use bitcoin_hashes::hash160::Hash as Hash160; use secp256k1::key::{SecretKey, PublicKey}; -use secp256k1::Secp256k1; +use secp256k1::{Secp256k1, Signature}; use secp256k1; use util::byte_utils; use util::logger::Logger; +use util::ser::Writeable; + +use ln::chan_utils; +use ln::chan_utils::{TxCreationKeys, HTLCOutputInCommitment, make_funding_redeemscript, ChannelPublicKeys}; +use ln::msgs; use std::sync::Arc; use std::sync::atomic::{AtomicUsize, Ordering}; @@ -68,6 +75,9 @@ pub enum SpendableOutputDescriptor { /// A trait to describe an object which can get user secrets and key material. pub trait KeysInterface: Send + Sync { + /// A type which implements ChannelKeys which will be returned by get_channel_keys. + type ChanKeySigner : ChannelKeys; + /// Get node secret key (aka node_id or network_key) fn get_node_secret(&self) -> SecretKey; /// Get destination redeemScript to encumber static protocol exit points. @@ -76,18 +86,88 @@ pub trait KeysInterface: Send + Sync { fn get_shutdown_pubkey(&self) -> PublicKey; /// Get a new set of ChannelKeys for per-channel secrets. These MUST be unique even if you /// restarted with some stale data! - fn get_channel_keys(&self, inbound: bool) -> ChannelKeys; - /// Get a secret for construting an onion packet - fn get_session_key(&self) -> SecretKey; + fn get_channel_keys(&self, inbound: bool) -> Self::ChanKeySigner; + /// Get a secret and PRNG seed for construting an onion packet + fn get_onion_rand(&self) -> (SecretKey, [u8; 32]); /// Get a unique temporary channel id. Channels will be referred to by this until the funding /// transaction is created, at which point they will use the outpoint in the funding /// transaction. fn get_channel_id(&self) -> [u8; 32]; } -/// Set of lightning keys needed to operate a channel as described in BOLT 3 +/// Set of lightning keys needed to operate a channel as described in BOLT 3. +/// +/// Signing services could be implemented on a hardware wallet. In this case, +/// the current ChannelKeys would be a front-end on top of a communication +/// channel connected to your secure device and lightning key material wouldn't +/// reside on a hot server. Nevertheless, a this deployment would still need +/// to trust the ChannelManager to avoid loss of funds as this latest component +/// could ask to sign commitment transaction with HTLCs paying to attacker pubkeys. +/// +/// A more secure iteration would be to use hashlock (or payment points) to pair +/// invoice/incoming HTLCs with outgoing HTLCs to implement a no-trust-ChannelManager +/// at the price of more state and computation on the hardware wallet side. In the future, +/// we are looking forward to design such interface. +/// +/// In any case, ChannelMonitor or fallback watchtowers are always going to be trusted +/// to act, as liveness and breach reply correctness are always going to be hard requirements +/// of LN security model, orthogonal of key management issues. +/// +/// If you're implementing a custom signer, you almost certainly want to implement +/// Readable/Writable to serialize out a unique reference to this set of keys so +/// that you can serialize the full ChannelManager object. +/// +/// (TODO: We shouldn't require that, and should have an API to get them at deser time, due mostly +/// to the possibility of reentrancy issues by calling the user's code during our deserialization +/// routine). +pub trait ChannelKeys : Send { + /// Gets the private key for the anchor tx + fn funding_key<'a>(&'a self) -> &'a SecretKey; + /// Gets the local secret key for blinded revocation pubkey + fn revocation_base_key<'a>(&'a self) -> &'a SecretKey; + /// Gets the local secret key used in to_remote output of remote commitment tx + /// (and also as part of obscured commitment number) + fn payment_base_key<'a>(&'a self) -> &'a SecretKey; + /// Gets the local secret key used in HTLC-Success/HTLC-Timeout txn and to_local output + fn delayed_payment_base_key<'a>(&'a self) -> &'a SecretKey; + /// Gets the local htlc secret key used in commitment tx htlc outputs + fn htlc_base_key<'a>(&'a self) -> &'a SecretKey; + /// Gets the commitment seed + fn commitment_seed<'a>(&'a self) -> &'a [u8; 32]; + + /// Create a signature for a remote commitment transaction and associated HTLC transactions. + /// + /// Note that if signing fails or is rejected, the channel will be force-closed. + /// + /// TODO: Document the things someone using this interface should enforce before signing. + /// TODO: Add more input vars to enable better checking (preferably removing commitment_tx and + /// making the callee generate it via some util function we expose)! + fn sign_remote_commitment(&self, channel_value_satoshis: u64, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1) -> Result<(Signature, Vec), ()>; + + /// Create a signature for a (proposed) closing transaction. + /// + /// Note that, due to rounding, there may be one "missing" satoshi, and either party may have + /// chosen to forgo their output as dust. + fn sign_closing_transaction(&self, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, closing_tx: &Transaction, secp_ctx: &Secp256k1) -> Result; + + /// Signs a channel announcement message with our funding key, proving it comes from one + /// of the channel participants. + /// + /// Note that if this fails or is rejected, the channel will not be publicly announced and + /// our counterparty may (though likely will not) close the channel on us for violating the + /// protocol. + fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1) -> Result; + + /// Set the remote channel basepoints. This is done immediately on incoming channels + /// and as soon as the channel is accepted on outgoing channels. + /// + /// Will be called before any signatures are applied. + fn set_remote_channel_pubkeys(&mut self, channel_points: &ChannelPublicKeys); +} + #[derive(Clone)] -pub struct ChannelKeys { +/// A simple implementation of ChannelKeys that just keeps the private keys in memory. +pub struct InMemoryChannelKeys { /// Private key of anchor tx pub funding_key: SecretKey, /// Local secret key for blinded revocation pubkey @@ -100,15 +180,76 @@ pub struct ChannelKeys { pub htlc_base_key: SecretKey, /// Commitment seed pub commitment_seed: [u8; 32], + /// Remote funding pubkey + pub remote_channel_pubkeys: Option, +} + +impl ChannelKeys for InMemoryChannelKeys { + fn funding_key(&self) -> &SecretKey { &self.funding_key } + fn revocation_base_key(&self) -> &SecretKey { &self.revocation_base_key } + fn payment_base_key(&self) -> &SecretKey { &self.payment_base_key } + fn delayed_payment_base_key(&self) -> &SecretKey { &self.delayed_payment_base_key } + fn htlc_base_key(&self) -> &SecretKey { &self.htlc_base_key } + fn commitment_seed(&self) -> &[u8; 32] { &self.commitment_seed } + + fn sign_remote_commitment(&self, channel_value_satoshis: u64, feerate_per_kw: u64, commitment_tx: &Transaction, keys: &TxCreationKeys, htlcs: &[&HTLCOutputInCommitment], to_self_delay: u16, secp_ctx: &Secp256k1) -> Result<(Signature, Vec), ()> { + if commitment_tx.input.len() != 1 { return Err(()); } + + let funding_pubkey = PublicKey::from_secret_key(secp_ctx, &self.funding_key); + let remote_channel_pubkeys = self.remote_channel_pubkeys.as_ref().expect("must set remote channel pubkeys before signing"); + let channel_funding_redeemscript = make_funding_redeemscript(&funding_pubkey, &remote_channel_pubkeys.funding_pubkey); + + let commitment_sighash = hash_to_message!(&bip143::SighashComponents::new(&commitment_tx).sighash_all(&commitment_tx.input[0], &channel_funding_redeemscript, channel_value_satoshis)[..]); + let commitment_sig = secp_ctx.sign(&commitment_sighash, &self.funding_key); + + let commitment_txid = commitment_tx.txid(); + + let mut htlc_sigs = Vec::with_capacity(htlcs.len()); + for ref htlc in htlcs { + if let Some(_) = htlc.transaction_output_index { + 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); + let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys); + let htlc_sighash = hash_to_message!(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]); + let our_htlc_key = match chan_utils::derive_private_key(&secp_ctx, &keys.per_commitment_point, &self.htlc_base_key) { + Ok(s) => s, + Err(_) => return Err(()), + }; + htlc_sigs.push(secp_ctx.sign(&htlc_sighash, &our_htlc_key)); + } + } + + Ok((commitment_sig, htlc_sigs)) + } + + fn sign_closing_transaction(&self, channel_value_satoshis: u64, channel_funding_redeemscript: &Script, closing_tx: &Transaction, secp_ctx: &Secp256k1) -> Result { + if closing_tx.input.len() != 1 { return Err(()); } + if closing_tx.input[0].witness.len() != 0 { return Err(()); } + if closing_tx.output.len() > 2 { return Err(()); } + + let sighash = hash_to_message!(&bip143::SighashComponents::new(closing_tx) + .sighash_all(&closing_tx.input[0], &channel_funding_redeemscript, channel_value_satoshis)[..]); + Ok(secp_ctx.sign(&sighash, &self.funding_key)) + } + + fn sign_channel_announcement(&self, msg: &msgs::UnsignedChannelAnnouncement, secp_ctx: &Secp256k1) -> Result { + let msghash = hash_to_message!(&Sha256dHash::hash(&msg.encode()[..])[..]); + Ok(secp_ctx.sign(&msghash, &self.funding_key)) + } + + fn set_remote_channel_pubkeys(&mut self, channel_pubkeys: &ChannelPublicKeys) { + assert!(self.remote_channel_pubkeys.is_none(), "Already set remote channel pubkeys"); + self.remote_channel_pubkeys = Some(channel_pubkeys.clone()); + } } -impl_writeable!(ChannelKeys, 0, { +impl_writeable!(InMemoryChannelKeys, 0, { funding_key, revocation_base_key, payment_base_key, delayed_payment_base_key, htlc_base_key, - commitment_seed + commitment_seed, + remote_channel_pubkeys }); /// Simple KeysInterface implementor that takes a 32-byte seed for use as a BIP 32 extended key @@ -203,6 +344,8 @@ impl KeysManager { } impl KeysInterface for KeysManager { + type ChanKeySigner = InMemoryChannelKeys; + fn get_node_secret(&self) -> SecretKey { self.node_secret.clone() } @@ -215,7 +358,7 @@ impl KeysInterface for KeysManager { self.shutdown_pubkey.clone() } - fn get_channel_keys(&self, _inbound: bool) -> ChannelKeys { + fn get_channel_keys(&self, _inbound: bool) -> InMemoryChannelKeys { // We only seriously intend to rely on the channel_master_key for true secure // entropy, everything else just ensures uniqueness. We rely on the unique_start (ie // starting_time provided in the constructor) to be unique. @@ -248,23 +391,31 @@ impl KeysInterface for KeysManager { let delayed_payment_base_key = key_step!(b"delayed payment base key", payment_base_key); let htlc_base_key = key_step!(b"HTLC base key", delayed_payment_base_key); - ChannelKeys { + InMemoryChannelKeys { funding_key, revocation_base_key, payment_base_key, delayed_payment_base_key, htlc_base_key, commitment_seed, + remote_channel_pubkeys: None, } } - fn get_session_key(&self) -> SecretKey { + fn get_onion_rand(&self) -> (SecretKey, [u8; 32]) { let mut sha = self.unique_start.clone(); let child_ix = self.session_child_index.fetch_add(1, Ordering::AcqRel); 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"); sha.input(&child_privkey.private_key.key[..]); - SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted") + + let mut rng_seed = sha.clone(); + // Not exactly the most ideal construction, but the second value will get fed into + // ChaCha so it is another step harder to break. + rng_seed.input(b"RNG Seed Salt"); + sha.input(b"Session Key Salt"); + (SecretKey::from_slice(&Sha256::from_engine(sha).into_inner()).expect("Your RNG is busted"), + Sha256::from_engine(rng_seed).into_inner()) } fn get_channel_id(&self) -> [u8; 32] {