X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fchain%2Fkeysinterface.rs;h=b65cd0df77d3a150011d53c321ccb1fec406c96c;hb=30a12759f1608b4891e1a5cf9471a3997efd9411;hp=5ffdc7130f66a37f8e702a36024e1ff658c69708;hpb=f2a2fd0d48be78972ed81481c2dfbfb68ecda44e;p=rust-lightning diff --git a/lightning/src/chain/keysinterface.rs b/lightning/src/chain/keysinterface.rs index 5ffdc713..b65cd0df 100644 --- a/lightning/src/chain/keysinterface.rs +++ b/lightning/src/chain/keysinterface.rs @@ -2,64 +2,84 @@ //! 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}; -/// When on-chain outputs are created by rust-lightning an event is generated which informs the -/// user thereof. This enum describes the format of the output and provides the OutPoint. +/// When on-chain outputs are created by rust-lightning (which our counterparty is not able to +/// claim at any point in the future) an event is generated which you must track and be able to +/// spend on-chain. The information needed to do this is provided in this enum, including the +/// outpoint describing which txid and output index is available, the full output which exists at +/// that txid/index, and any keys or other information required to sign. pub enum SpendableOutputDescriptor { - /// Outpoint with an output to a script which was provided via KeysInterface, thus you should - /// have stored somewhere how to spend script_pubkey! - /// Outputs from a justice tx, claim tx or preimage tx + /// An output to a script which was provided via KeysInterface, thus you should already know + /// how to spend it. No keys are provided as rust-lightning was never given any keys - only the + /// script_pubkey as it appears in the output. + /// These may include outputs from a transaction punishing our counterparty or claiming an HTLC + /// on-chain using the payment preimage or after it has timed out. StaticOutput { - /// The outpoint spendable by user wallet + /// The outpoint which is spendable outpoint: OutPoint, - /// The output which is referenced by the given outpoint + /// The output which is referenced by the given outpoint. output: TxOut, }, - /// Outpoint commits to a P2WSH - /// P2WSH should be spend by the following witness : - /// 0 - /// With input nSequence set to_self_delay. - /// Outputs from a HTLC-Success/Timeout tx/commitment tx + /// An output to a P2WSH script which can be spent with a single signature after a CSV delay. + /// The private key which should be used to sign the transaction is provided, as well as the + /// full witness redeemScript which is hashed in the output script_pubkey. + /// The witness in the spending input should be: + /// + /// + /// Note that the nSequence field in the input must be set to_self_delay (which corresponds to + /// the transaction not being broadcastable until at least to_self_delay blocks after the input + /// confirms). + /// These are generally the result of a "revocable" output to us, spendable only by us unless + /// it is an output from us having broadcast an old state (which should never happen). DynamicOutputP2WSH { - /// Outpoint spendable by user wallet + /// The outpoint which is spendable outpoint: OutPoint, - /// local_delayedkey = delayed_payment_basepoint_secret + SHA256(per_commitment_point || delayed_payment_basepoint) OR + /// The secret key which must be used to sign the spending transaction key: SecretKey, - /// witness redeemScript encumbering output. + /// The witness redeemScript which is hashed to create the script_pubkey in the given output witness_script: Script, - /// nSequence input must commit to self_delay to satisfy script's OP_CSV + /// The nSequence value which must be set in the spending input to satisfy the OP_CSV in + /// the witness_script. to_self_delay: u16, /// The output which is referenced by the given outpoint output: TxOut, }, - /// Outpoint commits to a P2WPKH - /// P2WPKH should be spend by the following witness : - /// - /// Outputs to_remote from a commitment tx + /// An output to a P2WPKH, spendable exclusively by the given private key. + /// The witness in the spending input, is, thus, simply: + /// + /// These are generally the result of our counterparty having broadcast the current state, + /// allowing us to claim the non-HTLC-encumbered outputs immediately. DynamicOutputP2WPKH { - /// Outpoint spendable by user wallet + /// The outpoint which is spendable outpoint: OutPoint, - /// localkey = payment_basepoint_secret + SHA256(per_commitment_point || payment_basepoint + /// The secret key which must be used to sign the spending transaction key: SecretKey, /// The output which is reference by the given outpoint output: TxOut, @@ -90,6 +110,22 @@ pub trait KeysInterface: Send + Sync { /// 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. @@ -102,14 +138,44 @@ pub trait ChannelKeys : Send { 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 commitment tx htlc outputs + /// 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 tx + /// 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)] @@ -127,6 +193,8 @@ pub struct InMemoryChannelKeys { pub htlc_base_key: SecretKey, /// Commitment seed pub commitment_seed: [u8; 32], + /// Remote funding pubkey + pub remote_channel_pubkeys: Option, } impl ChannelKeys for InMemoryChannelKeys { @@ -136,6 +204,55 @@ impl ChannelKeys for InMemoryChannelKeys { 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!(InMemoryChannelKeys, 0, { @@ -144,7 +261,8 @@ impl_writeable!(InMemoryChannelKeys, 0, { 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 @@ -293,6 +411,7 @@ impl KeysInterface for KeysManager { delayed_payment_base_key, htlc_base_key, commitment_seed, + remote_channel_pubkeys: None, } }