X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Fchan_utils.rs;h=a9be581b8f18935eaccbeb42374eea2fee70eb79;hb=51a5a1a50f59ecdddece6e0baeb0ac0ec48d168a;hp=3fd489fa1a94348b1c9bc9d0faac1a6dd1ddff88;hpb=8c69bb11b8e6c53f69e9a27f6657d69bee1b7e5e;p=rust-lightning diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs index 3fd489fa..a9be581b 100644 --- a/lightning/src/ln/chan_utils.rs +++ b/lightning/src/ln/chan_utils.rs @@ -1,3 +1,12 @@ +// This file is Copyright its original authors, visible in version control +// history. +// +// This file is licensed under the Apache License, Version 2.0 or the MIT license +// , at your option. +// You may not use this file except in accordance with one or both of these +// licenses. + //! Various utilities for building scripts and deriving keys related to channels. These are //! largely of interest for those implementing chain::keysinterface::ChannelKeys message signing //! by hand. @@ -5,23 +14,28 @@ use bitcoin::blockdata::script::{Script,Builder}; use bitcoin::blockdata::opcodes; use bitcoin::blockdata::transaction::{TxIn,TxOut,OutPoint,Transaction, SigHashType}; -use bitcoin::consensus::encode::{self, Decodable, Encodable}; +use bitcoin::consensus::encode::{Decodable, Encodable}; +use bitcoin::consensus::encode; use bitcoin::util::bip143; -use bitcoin_hashes::{Hash, HashEngine}; -use bitcoin_hashes::sha256::Hash as Sha256; -use bitcoin_hashes::ripemd160::Hash as Ripemd160; -use bitcoin_hashes::hash160::Hash as Hash160; -use bitcoin_hashes::sha256d::Hash as Sha256dHash; +use bitcoin::hashes::{Hash, HashEngine}; +use bitcoin::hashes::sha256::Hash as Sha256; +use bitcoin::hashes::ripemd160::Hash as Ripemd160; +use bitcoin::hash_types::{Txid, PubkeyHash}; use ln::channelmanager::{PaymentHash, PaymentPreimage}; use ln::msgs::DecodeError; use util::ser::{Readable, Writeable, Writer, WriterWriteAdaptor}; use util::byte_utils; -use secp256k1::key::{SecretKey, PublicKey}; -use secp256k1::{Secp256k1, Signature}; -use secp256k1; +use bitcoin::secp256k1::key::{SecretKey, PublicKey}; +use bitcoin::secp256k1::{Secp256k1, Signature}; +use bitcoin::secp256k1::Error as SecpError; +use bitcoin::secp256k1; + +use std::{cmp, mem}; + +const MAX_ALLOC_SIZE: usize = 64*1024; pub(super) const HTLC_SUCCESS_TX_WEIGHT: u64 = 703; pub(super) const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663; @@ -48,7 +62,8 @@ impl HTLCType { // Various functions for key derivation and transaction creation for use within channels. Primarily // used in Channel and ChannelMonitor. -pub(super) fn build_commitment_secret(commitment_seed: &[u8; 32], idx: u64) -> [u8; 32] { +/// Build the commitment secret from the seed and the commitment number +pub fn build_commitment_secret(commitment_seed: &[u8; 32], idx: u64) -> [u8; 32] { let mut res: [u8; 32] = commitment_seed.clone(); for i in 0..48 { let bitpos = 47 - i; @@ -66,7 +81,7 @@ pub(super) fn build_commitment_secret(commitment_seed: &[u8; 32], idx: u64) -> [ /// Allows us to keep track of all of the revocation secrets of counterarties in just 50*32 bytes /// or so. #[derive(Clone)] -pub(super) struct CounterpartyCommitmentSecrets { +pub(crate) struct CounterpartyCommitmentSecrets { old_secrets: [([u8; 32], u64); 49], } @@ -82,7 +97,7 @@ impl PartialEq for CounterpartyCommitmentSecrets { } impl CounterpartyCommitmentSecrets { - pub(super) fn new() -> Self { + pub(crate) fn new() -> Self { Self { old_secrets: [([0; 32], 1 << 48); 49], } } @@ -96,7 +111,7 @@ impl CounterpartyCommitmentSecrets { 48 } - pub(super) fn get_min_seen_secret(&self) -> u64 { + pub(crate) fn get_min_seen_secret(&self) -> u64 { //TODO This can be optimized? let mut min = 1 << 48; for &(_, idx) in self.old_secrets.iter() { @@ -120,7 +135,7 @@ impl CounterpartyCommitmentSecrets { res } - pub(super) fn provide_secret(&mut self, idx: u64, secret: [u8; 32]) -> Result<(), ()> { + pub(crate) fn provide_secret(&mut self, idx: u64, secret: [u8; 32]) -> Result<(), ()> { let pos = Self::place_secret(idx); for i in 0..pos { let (old_secret, old_idx) = self.old_secrets[i as usize]; @@ -136,7 +151,7 @@ impl CounterpartyCommitmentSecrets { } /// Can only fail if idx is < get_min_seen_secret - pub(super) fn get_secret(&self, idx: u64) -> Option<[u8; 32]> { + pub(crate) fn get_secret(&self, idx: u64) -> Option<[u8; 32]> { for i in 0..self.old_secrets.len() { if (idx & (!((1 << i) - 1))) == self.old_secrets[i].1 { return Some(Self::derive_secret(self.old_secrets[i].0, i as u8, idx)) @@ -156,8 +171,8 @@ impl Writeable for CounterpartyCommitmentSecrets { Ok(()) } } -impl Readable for CounterpartyCommitmentSecrets { - fn read(reader: &mut R) -> Result { +impl Readable for CounterpartyCommitmentSecrets { + fn read(reader: &mut R) -> Result { let mut old_secrets = [([0; 32], 1 << 48); 49]; for &mut (ref mut secret, ref mut idx) in old_secrets.iter_mut() { *secret = Readable::read(reader)?; @@ -168,9 +183,12 @@ impl Readable for CounterpartyCommitmentSecrets { } } -/// Derives a per-commitment-transaction private key (eg an htlc key or payment key) from the base -/// private key for that type of key and the per_commitment_point (available in TxCreationKeys) -pub fn derive_private_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result { +/// Derives a per-commitment-transaction private key (eg an htlc key or delayed_payment key) +/// from the base secret and the per_commitment_point. +/// +/// Note that this is infallible iff we trust that at least one of the two input keys are randomly +/// generated (ie our own). +pub fn derive_private_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_secret: &SecretKey) -> Result { let mut sha = Sha256::engine(); sha.input(&per_commitment_point.serialize()); sha.input(&PublicKey::from_secret_key(&secp_ctx, &base_secret).serialize()); @@ -181,7 +199,13 @@ pub fn derive_private_key(secp_ctx: &Secp256k1, per_co Ok(key) } -pub(super) fn derive_public_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result { +/// Derives a per-commitment-transaction public key (eg an htlc key or a delayed_payment key) +/// from the base point and the per_commitment_key. This is the public equivalent of +/// derive_private_key - using only public keys to derive a public key instead of private keys. +/// +/// Note that this is infallible iff we trust that at least one of the two input keys are randomly +/// generated (ie our own). +pub fn derive_public_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, base_point: &PublicKey) -> Result { let mut sha = Sha256::engine(); sha.input(&per_commitment_point.serialize()); sha.input(&base_point.serialize()); @@ -191,16 +215,22 @@ pub(super) fn derive_public_key(secp_ctx: &Secp256k1, base_point.combine(&hashkey) } -/// Derives a revocation key from its constituent parts. +/// Derives a per-commitment-transaction revocation key from its constituent parts. +/// +/// Only the cheating participant owns a valid witness to propagate a revoked +/// commitment transaction, thus per_commitment_secret always come from cheater +/// and revocation_base_secret always come from punisher, which is the broadcaster +/// of the transaction spending with this key knowledge. +/// /// Note that this is infallible iff we trust that at least one of the two input keys are randomly /// generated (ie our own). -pub(super) fn derive_private_revocation_key(secp_ctx: &Secp256k1, per_commitment_secret: &SecretKey, revocation_base_secret: &SecretKey) -> Result { - let revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &revocation_base_secret); +pub fn derive_private_revocation_key(secp_ctx: &Secp256k1, per_commitment_secret: &SecretKey, countersignatory_revocation_base_secret: &SecretKey) -> Result { + let countersignatory_revocation_base_point = PublicKey::from_secret_key(&secp_ctx, &countersignatory_revocation_base_secret); let per_commitment_point = PublicKey::from_secret_key(&secp_ctx, &per_commitment_secret); let rev_append_commit_hash_key = { let mut sha = Sha256::engine(); - sha.input(&revocation_base_point.serialize()); + sha.input(&countersignatory_revocation_base_point.serialize()); sha.input(&per_commitment_point.serialize()); Sha256::from_engine(sha).into_inner() @@ -208,23 +238,34 @@ pub(super) fn derive_private_revocation_key(secp_ctx: &Se let commit_append_rev_hash_key = { let mut sha = Sha256::engine(); sha.input(&per_commitment_point.serialize()); - sha.input(&revocation_base_point.serialize()); + sha.input(&countersignatory_revocation_base_point.serialize()); Sha256::from_engine(sha).into_inner() }; - let mut part_a = revocation_base_secret.clone(); - part_a.mul_assign(&rev_append_commit_hash_key)?; - let mut part_b = per_commitment_secret.clone(); - part_b.mul_assign(&commit_append_rev_hash_key)?; - part_a.add_assign(&part_b[..])?; - Ok(part_a) + let mut countersignatory_contrib = countersignatory_revocation_base_secret.clone(); + countersignatory_contrib.mul_assign(&rev_append_commit_hash_key)?; + let mut broadcaster_contrib = per_commitment_secret.clone(); + broadcaster_contrib.mul_assign(&commit_append_rev_hash_key)?; + countersignatory_contrib.add_assign(&broadcaster_contrib[..])?; + Ok(countersignatory_contrib) } -pub(super) fn derive_public_revocation_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, revocation_base_point: &PublicKey) -> Result { +/// Derives a per-commitment-transaction revocation public key from its constituent parts. This is +/// the public equivalend of derive_private_revocation_key - using only public keys to derive a +/// public key instead of private keys. +/// +/// Only the cheating participant owns a valid witness to propagate a revoked +/// commitment transaction, thus per_commitment_point always come from cheater +/// and revocation_base_point always come from punisher, which is the broadcaster +/// of the transaction spending with this key knowledge. +/// +/// Note that this is infallible iff we trust that at least one of the two input keys are randomly +/// generated (ie our own). +pub fn derive_public_revocation_key(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, countersignatory_revocation_base_point: &PublicKey) -> Result { let rev_append_commit_hash_key = { let mut sha = Sha256::engine(); - sha.input(&revocation_base_point.serialize()); + sha.input(&countersignatory_revocation_base_point.serialize()); sha.input(&per_commitment_point.serialize()); Sha256::from_engine(sha).into_inner() @@ -232,38 +273,70 @@ pub(super) fn derive_public_revocation_key(secp_ctx: let commit_append_rev_hash_key = { let mut sha = Sha256::engine(); sha.input(&per_commitment_point.serialize()); - sha.input(&revocation_base_point.serialize()); + sha.input(&countersignatory_revocation_base_point.serialize()); Sha256::from_engine(sha).into_inner() }; - let mut part_a = revocation_base_point.clone(); - part_a.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?; - let mut part_b = per_commitment_point.clone(); - part_b.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?; - part_a.combine(&part_b) + let mut countersignatory_contrib = countersignatory_revocation_base_point.clone(); + countersignatory_contrib.mul_assign(&secp_ctx, &rev_append_commit_hash_key)?; + let mut broadcaster_contrib = per_commitment_point.clone(); + broadcaster_contrib.mul_assign(&secp_ctx, &commit_append_rev_hash_key)?; + countersignatory_contrib.combine(&broadcaster_contrib) } /// The set of public keys which are used in the creation of one commitment transaction. /// These are derived from the channel base keys and per-commitment data. +/// +/// A broadcaster key is provided from potential broadcaster of the computed transaction. +/// A countersignatory key is coming from a protocol participant unable to broadcast the +/// transaction. +/// +/// These keys are assumed to be good, either because the code derived them from +/// channel basepoints via the new function, or they were obtained via +/// PreCalculatedTxCreationKeys.trust_key_derivation because we trusted the source of the +/// pre-calculated keys. #[derive(PartialEq, Clone)] pub struct TxCreationKeys { - /// The per-commitment public key which was used to derive the other keys. + /// The broadcaster's per-commitment public key which was used to derive the other keys. pub per_commitment_point: PublicKey, - /// The revocation key which is used to allow the owner of the commitment transaction to - /// provide their counterparty the ability to punish them if they broadcast an old state. - pub(crate) revocation_key: PublicKey, - /// A's HTLC Key - pub(crate) a_htlc_key: PublicKey, - /// B's HTLC Key - pub(crate) b_htlc_key: PublicKey, - /// A's Payment Key (which isn't allowed to be spent from for some delay) - pub(crate) a_delayed_payment_key: PublicKey, - /// B's Payment Key - pub(crate) b_payment_key: PublicKey, + /// The revocation key which is used to allow the broadcaster of the commitment + /// transaction to provide their counterparty the ability to punish them if they broadcast + /// an old state. + pub revocation_key: PublicKey, + /// Broadcaster's HTLC Key + pub broadcaster_htlc_key: PublicKey, + /// Countersignatory's HTLC Key + pub countersignatory_htlc_key: PublicKey, + /// Broadcaster's Payment Key (which isn't allowed to be spent from for some delay) + pub broadcaster_delayed_payment_key: PublicKey, } impl_writeable!(TxCreationKeys, 33*6, - { per_commitment_point, revocation_key, a_htlc_key, b_htlc_key, a_delayed_payment_key, b_payment_key }); + { per_commitment_point, revocation_key, broadcaster_htlc_key, countersignatory_htlc_key, broadcaster_delayed_payment_key }); + +/// The per-commitment point and a set of pre-calculated public keys used for transaction creation +/// in the signer. +/// The pre-calculated keys are an optimization, because ChannelKeys has enough +/// information to re-derive them. +pub struct PreCalculatedTxCreationKeys(TxCreationKeys); + +impl PreCalculatedTxCreationKeys { + /// Create a new PreCalculatedTxCreationKeys from TxCreationKeys + pub fn new(keys: TxCreationKeys) -> Self { + PreCalculatedTxCreationKeys(keys) + } + + /// The pre-calculated transaction creation public keys. + /// An external validating signer should not trust these keys. + pub fn trust_key_derivation(&self) -> &TxCreationKeys { + &self.0 + } + + /// The transaction per-commitment point + pub fn per_commitment_point(&self) -> &PublicKey { + &self.0.per_commitment_point + } +} /// One counterparty's public keys which do not change over the life of a channel. #[derive(Clone, PartialEq)] @@ -272,13 +345,14 @@ pub struct ChannelPublicKeys { /// on-chain channel lock-in 2-of-2 multisig output. pub funding_pubkey: PublicKey, /// The base point which is used (with derive_public_revocation_key) to derive per-commitment - /// revocation keys. The per-commitment revocation private key is then revealed by the owner of - /// a commitment transaction so that their counterparty can claim all available funds if they - /// broadcast an old state. + /// revocation keys. This is combined with the per-commitment-secret generated by the + /// counterparty to create a secret which the counterparty can reveal to revoke previous + /// states. pub revocation_basepoint: PublicKey, - /// The base point which is used (with derive_public_key) to derive a per-commitment payment - /// public key which receives immediately-spendable non-HTLC-encumbered funds. - pub payment_basepoint: PublicKey, + /// The public key on which the non-broadcaster (ie the countersignatory) receives an immediately + /// spendable primary channel balance on the broadcaster's commitment transaction. This key is + /// static across every commitment transaction. + pub payment_point: PublicKey, /// The base point which is used (with derive_public_key) to derive a per-commitment payment /// public key which receives non-HTLC-encumbered funds which are only available for spending /// after some delay (or can be claimed via the revocation path). @@ -291,35 +365,36 @@ pub struct ChannelPublicKeys { impl_writeable!(ChannelPublicKeys, 33*5, { funding_pubkey, revocation_basepoint, - payment_basepoint, + payment_point, delayed_payment_basepoint, htlc_basepoint }); impl TxCreationKeys { - pub(crate) fn new(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, a_delayed_payment_base: &PublicKey, a_htlc_base: &PublicKey, b_revocation_base: &PublicKey, b_payment_base: &PublicKey, b_htlc_base: &PublicKey) -> Result { + /// Create a new TxCreationKeys from channel base points and the per-commitment point + pub fn derive_new(secp_ctx: &Secp256k1, per_commitment_point: &PublicKey, broadcaster_delayed_payment_base: &PublicKey, broadcaster_htlc_base: &PublicKey, countersignatory_revocation_base: &PublicKey, countersignatory_htlc_base: &PublicKey) -> Result { Ok(TxCreationKeys { per_commitment_point: per_commitment_point.clone(), - revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &b_revocation_base)?, - a_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_htlc_base)?, - b_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_htlc_base)?, - a_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &a_delayed_payment_base)?, - b_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &b_payment_base)?, + revocation_key: derive_public_revocation_key(&secp_ctx, &per_commitment_point, &countersignatory_revocation_base)?, + broadcaster_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &broadcaster_htlc_base)?, + countersignatory_htlc_key: derive_public_key(&secp_ctx, &per_commitment_point, &countersignatory_htlc_base)?, + broadcaster_delayed_payment_key: derive_public_key(&secp_ctx, &per_commitment_point, &broadcaster_delayed_payment_base)?, }) } } -/// Gets the "to_local" output redeemscript, ie the script which is time-locked or spendable by -/// the revocation key -pub(super) fn get_revokeable_redeemscript(revocation_key: &PublicKey, to_self_delay: u16, delayed_payment_key: &PublicKey) -> Script { +/// A script either spendable by the revocation +/// key or the broadcaster_delayed_payment_key and satisfying the relative-locktime OP_CSV constrain. +/// Encumbering a `to_holder` output on a commitment transaction or 2nd-stage HTLC transactions. +pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, contest_delay: u16, broadcaster_delayed_payment_key: &PublicKey) -> Script { Builder::new().push_opcode(opcodes::all::OP_IF) .push_slice(&revocation_key.serialize()) .push_opcode(opcodes::all::OP_ELSE) - .push_int(to_self_delay as i64) + .push_int(contest_delay as i64) .push_opcode(opcodes::all::OP_CSV) .push_opcode(opcodes::all::OP_DROP) - .push_slice(&delayed_payment_key.serialize()) + .push_slice(&broadcaster_delayed_payment_key.serialize()) .push_opcode(opcodes::all::OP_ENDIF) .push_opcode(opcodes::all::OP_CHECKSIG) .into_script() @@ -331,7 +406,7 @@ pub struct HTLCOutputInCommitment { /// Whether the HTLC was "offered" (ie outbound in relation to this commitment transaction). /// Note that this is not the same as whether it is ountbound *from us*. To determine that you /// need to compare this value to whether the commitment transaction in question is that of - /// the remote party or our own. + /// the counterparty or our own. pub offered: bool, /// The value, in msat, of the HTLC. The value as it appears in the commitment transaction is /// this divided by 1000. @@ -355,17 +430,17 @@ impl_writeable!(HTLCOutputInCommitment, 1 + 8 + 4 + 32 + 5, { }); #[inline] -pub(super) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, a_htlc_key: &PublicKey, b_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script { +pub(crate) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, broadcaster_htlc_key: &PublicKey, countersignatory_htlc_key: &PublicKey, revocation_key: &PublicKey) -> Script { let payment_hash160 = Ripemd160::hash(&htlc.payment_hash.0[..]).into_inner(); if htlc.offered { Builder::new().push_opcode(opcodes::all::OP_DUP) .push_opcode(opcodes::all::OP_HASH160) - .push_slice(&Hash160::hash(&revocation_key.serialize())[..]) + .push_slice(&PubkeyHash::hash(&revocation_key.serialize())[..]) .push_opcode(opcodes::all::OP_EQUAL) .push_opcode(opcodes::all::OP_IF) .push_opcode(opcodes::all::OP_CHECKSIG) .push_opcode(opcodes::all::OP_ELSE) - .push_slice(&b_htlc_key.serialize()[..]) + .push_slice(&countersignatory_htlc_key.serialize()[..]) .push_opcode(opcodes::all::OP_SWAP) .push_opcode(opcodes::all::OP_SIZE) .push_int(32) @@ -374,7 +449,7 @@ pub(super) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommit .push_opcode(opcodes::all::OP_DROP) .push_int(2) .push_opcode(opcodes::all::OP_SWAP) - .push_slice(&a_htlc_key.serialize()[..]) + .push_slice(&broadcaster_htlc_key.serialize()[..]) .push_int(2) .push_opcode(opcodes::all::OP_CHECKMULTISIG) .push_opcode(opcodes::all::OP_ELSE) @@ -388,12 +463,12 @@ pub(super) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommit } else { Builder::new().push_opcode(opcodes::all::OP_DUP) .push_opcode(opcodes::all::OP_HASH160) - .push_slice(&Hash160::hash(&revocation_key.serialize())[..]) + .push_slice(&PubkeyHash::hash(&revocation_key.serialize())[..]) .push_opcode(opcodes::all::OP_EQUAL) .push_opcode(opcodes::all::OP_IF) .push_opcode(opcodes::all::OP_CHECKSIG) .push_opcode(opcodes::all::OP_ELSE) - .push_slice(&b_htlc_key.serialize()[..]) + .push_slice(&countersignatory_htlc_key.serialize()[..]) .push_opcode(opcodes::all::OP_SWAP) .push_opcode(opcodes::all::OP_SIZE) .push_int(32) @@ -404,7 +479,7 @@ pub(super) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommit .push_opcode(opcodes::all::OP_EQUALVERIFY) .push_int(2) .push_opcode(opcodes::all::OP_SWAP) - .push_slice(&a_htlc_key.serialize()[..]) + .push_slice(&broadcaster_htlc_key.serialize()[..]) .push_int(2) .push_opcode(opcodes::all::OP_CHECKMULTISIG) .push_opcode(opcodes::all::OP_ELSE) @@ -419,31 +494,31 @@ pub(super) fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommit } } -/// note here that 'a_revocation_key' is generated using b_revocation_basepoint and a's -/// commitment secret. 'htlc' does *not* need to have its previous_output_index filled. +/// Gets the witness redeemscript for an HTLC output in a commitment transaction. Note that htlc +/// does not need to have its previous_output_index filled. #[inline] pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Script { - get_htlc_redeemscript_with_explicit_keys(htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key) + get_htlc_redeemscript_with_explicit_keys(htlc, &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key) } /// Gets the redeemscript for a funding output from the two funding public keys. /// Note that the order of funding public keys does not matter. -pub fn make_funding_redeemscript(a: &PublicKey, b: &PublicKey) -> Script { - let our_funding_key = a.serialize(); - let their_funding_key = b.serialize(); +pub fn make_funding_redeemscript(broadcaster: &PublicKey, countersignatory: &PublicKey) -> Script { + let broadcaster_funding_key = broadcaster.serialize(); + let countersignatory_funding_key = countersignatory.serialize(); let builder = Builder::new().push_opcode(opcodes::all::OP_PUSHNUM_2); - if our_funding_key[..] < their_funding_key[..] { - builder.push_slice(&our_funding_key) - .push_slice(&their_funding_key) + if broadcaster_funding_key[..] < countersignatory_funding_key[..] { + builder.push_slice(&broadcaster_funding_key) + .push_slice(&countersignatory_funding_key) } else { - builder.push_slice(&their_funding_key) - .push_slice(&our_funding_key) + builder.push_slice(&countersignatory_funding_key) + .push_slice(&broadcaster_funding_key) }.push_opcode(opcodes::all::OP_PUSHNUM_2).push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script() } /// panics if htlc.transaction_output_index.is_none()! -pub fn build_htlc_transaction(prev_hash: &Sha256dHash, feerate_per_kw: u64, to_self_delay: u16, htlc: &HTLCOutputInCommitment, a_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction { +pub fn build_htlc_transaction(prev_hash: &Txid, feerate_per_kw: u32, contest_delay: u16, htlc: &HTLCOutputInCommitment, broadcaster_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction { let mut txins: Vec = Vec::new(); txins.push(TxIn { previous_output: OutPoint { @@ -456,14 +531,14 @@ pub fn build_htlc_transaction(prev_hash: &Sha256dHash, feerate_per_kw: u64, to_s }); let total_fee = if htlc.offered { - feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000 + feerate_per_kw as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000 } else { - feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000 + feerate_per_kw as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000 }; let mut txouts: Vec = Vec::new(); txouts.push(TxOut { - script_pubkey: get_revokeable_redeemscript(revocation_key, to_self_delay, a_delayed_payment_key).to_v0_p2wsh(), + script_pubkey: get_revokeable_redeemscript(revocation_key, contest_delay, broadcaster_delayed_payment_key).to_v0_p2wsh(), value: htlc.amount_msat / 1000 - total_fee //TODO: BOLT 3 does not specify if we should add amount_msat before dividing or if we should divide by 1000 before subtracting (as we do here) }); @@ -475,153 +550,267 @@ pub fn build_htlc_transaction(prev_hash: &Sha256dHash, feerate_per_kw: u64, to_s } } -/// Signs a transaction created by build_htlc_transaction. If the transaction is an -/// HTLC-Success transaction (ie htlc.offered is false), preimage must be set! -pub(crate) fn sign_htlc_transaction(tx: &mut Transaction, their_sig: &Signature, preimage: &Option, htlc: &HTLCOutputInCommitment, a_htlc_key: &PublicKey, b_htlc_key: &PublicKey, revocation_key: &PublicKey, per_commitment_point: &PublicKey, htlc_base_key: &SecretKey, secp_ctx: &Secp256k1) -> Result<(Signature, Script), ()> { - if tx.input.len() != 1 { return Err(()); } - if tx.input[0].witness.len() != 0 { return Err(()); } - - let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&htlc, a_htlc_key, b_htlc_key, revocation_key); - - let our_htlc_key = derive_private_key(secp_ctx, per_commitment_point, htlc_base_key).map_err(|_| ())?; - let sighash = hash_to_message!(&bip143::SighashComponents::new(&tx).sighash_all(&tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]); - let local_tx = PublicKey::from_secret_key(&secp_ctx, &our_htlc_key) == *a_htlc_key; - let our_sig = secp_ctx.sign(&sighash, &our_htlc_key); - - tx.input[0].witness.push(Vec::new()); // First is the multisig dummy - - if local_tx { // b, then a - tx.input[0].witness.push(their_sig.serialize_der().to_vec()); - tx.input[0].witness.push(our_sig.serialize_der().to_vec()); - } else { - tx.input[0].witness.push(our_sig.serialize_der().to_vec()); - tx.input[0].witness.push(their_sig.serialize_der().to_vec()); - } - tx.input[0].witness[1].push(SigHashType::All as u8); - tx.input[0].witness[2].push(SigHashType::All as u8); - - if htlc.offered { - tx.input[0].witness.push(Vec::new()); - assert!(preimage.is_none()); - } else { - tx.input[0].witness.push(preimage.unwrap().0.to_vec()); - } - - tx.input[0].witness.push(htlc_redeemscript.as_bytes().to_vec()); - - Ok((our_sig, htlc_redeemscript)) -} - #[derive(Clone)] -/// We use this to track local commitment transactions and put off signing them until we are ready -/// to broadcast. Eventually this will require a signer which is possibly external, but for now we -/// just pass in the SecretKeys required. -pub(crate) struct LocalCommitmentTransaction { - tx: Transaction +/// We use this to track holder commitment transactions and put off signing them until we are ready +/// to broadcast. This class can be used inside a signer implementation to generate a signature +/// given the relevant secret key. +pub struct HolderCommitmentTransaction { + // TODO: We should migrate away from providing the transaction, instead providing enough to + // allow the ChannelKeys to construct it from scratch. Luckily we already have HTLC data here, + // so we're probably most of the way there. + /// The commitment transaction itself, in unsigned form. + pub unsigned_tx: Transaction, + /// Our counterparty's signature for the transaction, above. + pub counterparty_sig: Signature, + // Which order the signatures should go in when constructing the final commitment tx witness. + // The user should be able to reconstruc this themselves, so we don't bother to expose it. + holder_sig_first: bool, + pub(crate) keys: TxCreationKeys, + /// The feerate paid per 1000-weight-unit in this commitment transaction. This value is + /// controlled by the channel initiator. + pub feerate_per_kw: u32, + /// The HTLCs and counterparty htlc signatures which were included in this commitment transaction. + /// + /// Note that this includes all HTLCs, including ones which were considered dust and not + /// actually included in the transaction as it appears on-chain, but who's value is burned as + /// fees and not included in the to_holder or to_counterparty outputs. + /// + /// The counterparty HTLC signatures in the second element will always be set for non-dust HTLCs, ie + /// those for which transaction_output_index.is_some(). + pub per_htlc: Vec<(HTLCOutputInCommitment, Option)>, } -impl LocalCommitmentTransaction { +impl HolderCommitmentTransaction { #[cfg(test)] pub fn dummy() -> Self { - Self { tx: Transaction { - version: 2, - input: Vec::new(), - output: Vec::new(), - lock_time: 0, - } } + let dummy_input = TxIn { + previous_output: OutPoint { + txid: Default::default(), + vout: 0, + }, + script_sig: Default::default(), + sequence: 0, + witness: vec![] + }; + let dummy_key = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&[42; 32]).unwrap()); + let dummy_sig = Secp256k1::new().sign(&secp256k1::Message::from_slice(&[42; 32]).unwrap(), &SecretKey::from_slice(&[42; 32]).unwrap()); + Self { + unsigned_tx: Transaction { + version: 2, + input: vec![dummy_input], + output: Vec::new(), + lock_time: 0, + }, + counterparty_sig: dummy_sig, + holder_sig_first: false, + keys: TxCreationKeys { + per_commitment_point: dummy_key.clone(), + revocation_key: dummy_key.clone(), + broadcaster_htlc_key: dummy_key.clone(), + countersignatory_htlc_key: dummy_key.clone(), + broadcaster_delayed_payment_key: dummy_key.clone(), + }, + feerate_per_kw: 0, + per_htlc: Vec::new() + } } - pub fn new_missing_local_sig(mut tx: Transaction, their_sig: &Signature, our_funding_key: &PublicKey, their_funding_key: &PublicKey) -> LocalCommitmentTransaction { - if tx.input.len() != 1 { panic!("Tried to store a commitment transaction that had input count != 1!"); } - if tx.input[0].witness.len() != 0 { panic!("Tried to store a signed commitment transaction?"); } - - tx.input[0].witness.push(Vec::new()); // First is the multisig dummy + /// Generate a new HolderCommitmentTransaction based on a raw commitment transaction, + /// counterparty signature and both parties keys. + /// + /// The unsigned transaction outputs must be consistent with htlc_data. This function + /// only checks that the shape and amounts are consistent, but does not check the scriptPubkey. + pub fn new_missing_holder_sig(unsigned_tx: Transaction, counterparty_sig: Signature, holder_funding_key: &PublicKey, counterparty_funding_key: &PublicKey, keys: TxCreationKeys, feerate_per_kw: u32, htlc_data: Vec<(HTLCOutputInCommitment, Option)>) -> HolderCommitmentTransaction { + if unsigned_tx.input.len() != 1 { panic!("Tried to store a commitment transaction that had input count != 1!"); } + if unsigned_tx.input[0].witness.len() != 0 { panic!("Tried to store a signed commitment transaction?"); } + + for htlc in &htlc_data { + if let Some(index) = htlc.0.transaction_output_index { + let out = &unsigned_tx.output[index as usize]; + if out.value != htlc.0.amount_msat / 1000 { + panic!("HTLC at index {} has incorrect amount", index); + } + if !out.script_pubkey.is_v0_p2wsh() { + panic!("HTLC at index {} doesn't have p2wsh scriptPubkey", index); + } + } + } - if our_funding_key.serialize()[..] < their_funding_key.serialize()[..] { - tx.input[0].witness.push(Vec::new()); - tx.input[0].witness.push(their_sig.serialize_der().to_vec()); - tx.input[0].witness[2].push(SigHashType::All as u8); - } else { - tx.input[0].witness.push(their_sig.serialize_der().to_vec()); - tx.input[0].witness[1].push(SigHashType::All as u8); - tx.input[0].witness.push(Vec::new()); + Self { + unsigned_tx, + counterparty_sig, + holder_sig_first: holder_funding_key.serialize()[..] < counterparty_funding_key.serialize()[..], + keys, + feerate_per_kw, + per_htlc: htlc_data, } + } - Self { tx } + /// The pre-calculated transaction creation public keys. + /// An external validating signer should not trust these keys. + pub fn trust_key_derivation(&self) -> &TxCreationKeys { + &self.keys } - pub fn txid(&self) -> Sha256dHash { - self.tx.txid() + /// Get the txid of the holder commitment transaction contained in this + /// HolderCommitmentTransaction + pub fn txid(&self) -> Txid { + self.unsigned_tx.txid() } - pub fn has_local_sig(&self) -> bool { - if self.tx.input.len() != 1 { panic!("Commitment transactions must have input count == 1!"); } - if self.tx.input[0].witness.len() == 4 { - assert!(!self.tx.input[0].witness[1].is_empty()); - assert!(!self.tx.input[0].witness[2].is_empty()); - true - } else { - assert_eq!(self.tx.input[0].witness.len(), 3); - assert!(self.tx.input[0].witness[0].is_empty()); - assert!(self.tx.input[0].witness[1].is_empty() || self.tx.input[0].witness[2].is_empty()); - false - } + /// Gets holder signature for the contained commitment transaction given holder funding private key. + /// + /// Funding key is your key included in the 2-2 funding_outpoint lock. Should be provided + /// by your ChannelKeys. + /// Funding redeemscript is script locking funding_outpoint. This is the mutlsig script + /// between your own funding key and your counterparty's. Currently, this is provided in + /// ChannelKeys::sign_holder_commitment() calls directly. + /// Channel value is amount locked in funding_outpoint. + pub fn get_holder_sig(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1) -> Signature { + let sighash = hash_to_message!(&bip143::SigHashCache::new(&self.unsigned_tx) + .signature_hash(0, funding_redeemscript, channel_value_satoshis, SigHashType::All)[..]); + secp_ctx.sign(&sighash, funding_key) } - pub fn add_local_sig(&mut self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1) { - if self.has_local_sig() { return; } - let sighash = hash_to_message!(&bip143::SighashComponents::new(&self.tx) - .sighash_all(&self.tx.input[0], funding_redeemscript, channel_value_satoshis)[..]); - let our_sig = secp_ctx.sign(&sighash, funding_key); + pub(crate) fn add_holder_sig(&self, funding_redeemscript: &Script, holder_sig: Signature) -> Transaction { + let mut tx = self.unsigned_tx.clone(); + // First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element. + tx.input[0].witness.push(Vec::new()); - if self.tx.input[0].witness[1].is_empty() { - self.tx.input[0].witness[1] = our_sig.serialize_der().to_vec(); - self.tx.input[0].witness[1].push(SigHashType::All as u8); + if self.holder_sig_first { + tx.input[0].witness.push(holder_sig.serialize_der().to_vec()); + tx.input[0].witness.push(self.counterparty_sig.serialize_der().to_vec()); } else { - self.tx.input[0].witness[2] = our_sig.serialize_der().to_vec(); - self.tx.input[0].witness[2].push(SigHashType::All as u8); + tx.input[0].witness.push(self.counterparty_sig.serialize_der().to_vec()); + tx.input[0].witness.push(holder_sig.serialize_der().to_vec()); } + tx.input[0].witness[1].push(SigHashType::All as u8); + tx.input[0].witness[2].push(SigHashType::All as u8); - self.tx.input[0].witness.push(funding_redeemscript.as_bytes().to_vec()); + tx.input[0].witness.push(funding_redeemscript.as_bytes().to_vec()); + tx } - pub fn without_valid_witness(&self) -> &Transaction { &self.tx } - pub fn with_valid_witness(&self) -> &Transaction { - assert!(self.has_local_sig()); - &self.tx + /// Get a signature for each HTLC which was included in the commitment transaction (ie for + /// which HTLCOutputInCommitment::transaction_output_index.is_some()). + /// + /// The returned Vec has one entry for each HTLC, and in the same order. For HTLCs which were + /// considered dust and not included, a None entry exists, for all others a signature is + /// included. + pub fn get_htlc_sigs(&self, htlc_base_key: &SecretKey, counterparty_selected_contest_delay: u16, secp_ctx: &Secp256k1) -> Result>, ()> { + let txid = self.txid(); + let mut ret = Vec::with_capacity(self.per_htlc.len()); + let holder_htlc_key = derive_private_key(secp_ctx, &self.keys.per_commitment_point, htlc_base_key).map_err(|_| ())?; + + for this_htlc in self.per_htlc.iter() { + if this_htlc.0.transaction_output_index.is_some() { + let htlc_tx = build_htlc_transaction(&txid, self.feerate_per_kw, counterparty_selected_contest_delay, &this_htlc.0, &self.keys.broadcaster_delayed_payment_key, &self.keys.revocation_key); + + let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc.0, &self.keys.broadcaster_htlc_key, &self.keys.countersignatory_htlc_key, &self.keys.revocation_key); + + let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.0.amount_msat / 1000, SigHashType::All)[..]); + ret.push(Some(secp_ctx.sign(&sighash, &holder_htlc_key))); + } else { + ret.push(None); + } + } + Ok(ret) + } + + /// Gets a signed HTLC transaction given a preimage (for !htlc.offered) and the holder HTLC transaction signature. + pub(crate) fn get_signed_htlc_tx(&self, htlc_index: usize, signature: &Signature, preimage: &Option, counterparty_selected_contest_delay: u16) -> Transaction { + let txid = self.txid(); + let this_htlc = &self.per_htlc[htlc_index]; + assert!(this_htlc.0.transaction_output_index.is_some()); + // if we don't have preimage for an HTLC-Success, we can't generate an HTLC transaction. + if !this_htlc.0.offered && preimage.is_none() { unreachable!(); } + // Further, we should never be provided the preimage for an HTLC-Timeout transaction. + if this_htlc.0.offered && preimage.is_some() { unreachable!(); } + + let mut htlc_tx = build_htlc_transaction(&txid, self.feerate_per_kw, counterparty_selected_contest_delay, &this_htlc.0, &self.keys.broadcaster_delayed_payment_key, &self.keys.revocation_key); + // Channel should have checked that we have a counterparty signature for this HTLC at + // creation, and we should have a sensible htlc transaction: + assert!(this_htlc.1.is_some()); + + let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc.0, &self.keys.broadcaster_htlc_key, &self.keys.countersignatory_htlc_key, &self.keys.revocation_key); + + // First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element. + htlc_tx.input[0].witness.push(Vec::new()); + + htlc_tx.input[0].witness.push(this_htlc.1.unwrap().serialize_der().to_vec()); + htlc_tx.input[0].witness.push(signature.serialize_der().to_vec()); + htlc_tx.input[0].witness[1].push(SigHashType::All as u8); + htlc_tx.input[0].witness[2].push(SigHashType::All as u8); + + if this_htlc.0.offered { + // Due to BIP146 (MINIMALIF) this must be a zero-length element to relay. + htlc_tx.input[0].witness.push(Vec::new()); + } else { + htlc_tx.input[0].witness.push(preimage.unwrap().0.to_vec()); + } + + htlc_tx.input[0].witness.push(htlc_redeemscript.as_bytes().to_vec()); + htlc_tx } } -impl PartialEq for LocalCommitmentTransaction { +impl PartialEq for HolderCommitmentTransaction { // We dont care whether we are signed in equality comparison fn eq(&self, o: &Self) -> bool { self.txid() == o.txid() } } -impl Writeable for LocalCommitmentTransaction { +impl Writeable for HolderCommitmentTransaction { fn write(&self, writer: &mut W) -> Result<(), ::std::io::Error> { - if let Err(e) = self.tx.consensus_encode(&mut WriterWriteAdaptor(writer)) { + if let Err(e) = self.unsigned_tx.consensus_encode(&mut WriterWriteAdaptor(writer)) { match e { encode::Error::Io(e) => return Err(e), - _ => panic!("local tx must have been well-formed!"), + _ => panic!("holder tx must have been well-formed!"), } } + self.counterparty_sig.write(writer)?; + self.holder_sig_first.write(writer)?; + self.keys.write(writer)?; + self.feerate_per_kw.write(writer)?; + writer.write_all(&byte_utils::be64_to_array(self.per_htlc.len() as u64))?; + for &(ref htlc, ref sig) in self.per_htlc.iter() { + htlc.write(writer)?; + sig.write(writer)?; + } Ok(()) } } -impl Readable for LocalCommitmentTransaction { - fn read(reader: &mut R) -> Result { - let tx = match Transaction::consensus_decode(reader.by_ref()) { +impl Readable for HolderCommitmentTransaction { + fn read(reader: &mut R) -> Result { + let unsigned_tx = match Transaction::consensus_decode(reader.by_ref()) { Ok(tx) => tx, Err(e) => match e { encode::Error::Io(ioe) => return Err(DecodeError::Io(ioe)), _ => return Err(DecodeError::InvalidValue), }, }; + let counterparty_sig = Readable::read(reader)?; + let holder_sig_first = Readable::read(reader)?; + let keys = Readable::read(reader)?; + let feerate_per_kw = Readable::read(reader)?; + let htlcs_count: u64 = Readable::read(reader)?; + let mut per_htlc = Vec::with_capacity(cmp::min(htlcs_count as usize, MAX_ALLOC_SIZE / mem::size_of::<(HTLCOutputInCommitment, Option)>())); + for _ in 0..htlcs_count { + let htlc: HTLCOutputInCommitment = Readable::read(reader)?; + let sigs = Readable::read(reader)?; + per_htlc.push((htlc, sigs)); + } - if tx.input.len() != 1 { + if unsigned_tx.input.len() != 1 { // Ensure tx didn't hit the 0-input ambiguity case. return Err(DecodeError::InvalidValue); } - Ok(Self { tx }) + Ok(Self { + unsigned_tx, + counterparty_sig, + holder_sig_first, + keys, + feerate_per_kw, + per_htlc, + }) } }