X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Fchan_utils.rs;h=4438579657eecc74e6cf1cb9458b339c2db82292;hb=f24bbd63cc72e32efaa23844f19f4a7952fb22cb;hp=561448c8fbfd34b355b72ea9abfc73bf8656b403;hpb=f1c7fd2ab9b4df5f4b7cad855501d1178b2eb1c6;p=rust-lightning diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs index 561448c8..44385796 100644 --- a/lightning/src/ln/chan_utils.rs +++ b/lightning/src/ln/chan_utils.rs @@ -1,27 +1,51 @@ +// 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. +//! largely of interest for those implementing chain::keysinterface::Sign message signing by hand. 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::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::{PaymentHash, PaymentPreimage}; use ln::msgs::DecodeError; -use util::ser::{Readable, Writeable, Writer, WriterWriteAdaptor}; +use util::ser::{Readable, Writeable, Writer, MAX_BUF_SIZE}; use util::byte_utils; -use secp256k1::key::{SecretKey, PublicKey}; -use secp256k1::{Secp256k1, Signature}; -use secp256k1; +use bitcoin::hash_types::WPubkeyHash; +use bitcoin::secp256k1::key::{SecretKey, PublicKey}; +use bitcoin::secp256k1::{Secp256k1, Signature, Message}; +use bitcoin::secp256k1::Error as SecpError; +use bitcoin::secp256k1; + +use std::cmp; +use ln::chan_utils; +use util::transaction_utils::sort_outputs; +use ln::channel::INITIAL_COMMITMENT_NUMBER; +use std::io::Read; +use std::ops::Deref; +use chain; + +// Maximum size of a serialized HTLCOutputInCommitment +const HTLC_OUTPUT_IN_COMMITMENT_SIZE: usize = 1 + 8 + 4 + 32 + 5; + +pub(crate) const MAX_HTLCS: u16 = 483; + +// This checks that the buffer size is greater than the maximum possible size for serialized HTLCS +const _EXCESS_BUFFER_SIZE: usize = MAX_BUF_SIZE - MAX_HTLCS as usize * HTLC_OUTPUT_IN_COMMITMENT_SIZE; pub(super) const HTLC_SUCCESS_TX_WEIGHT: u64 = 703; pub(super) const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663; @@ -48,7 +72,8 @@ 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 +91,7 @@ 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 +107,7 @@ 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 +121,7 @@ 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() { @@ -108,7 +133,7 @@ impl CounterpartyCommitmentSecrets { } #[inline] - pub(super) fn derive_secret(secret: [u8; 32], bits: u8, idx: u64) -> [u8; 32] { + fn derive_secret(secret: [u8; 32], bits: u8, idx: u64) -> [u8; 32] { let mut res: [u8; 32] = secret; for i in 0..bits { let bitpos = bits - 1 - i; @@ -120,7 +145,7 @@ 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 +161,7 @@ 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)) @@ -168,9 +193,12 @@ 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 +209,13 @@ 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 +225,22 @@ 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 +248,34 @@ 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 +283,47 @@ 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 +/// CommitmentTransaction.trust().keys() 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, -} -impl_writeable!(TxCreationKeys, 33*6, - { per_commitment_point, revocation_key, a_htlc_key, b_htlc_key, a_delayed_payment_key, b_payment_key }); + /// 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*5, + { per_commitment_point, revocation_key, broadcaster_htlc_key, countersignatory_htlc_key, broadcaster_delayed_payment_key }); /// One counterparty's public keys which do not change over the life of a channel. #[derive(Clone, PartialEq)] @@ -272,13 +332,14 @@ 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). @@ -291,38 +352,60 @@ 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 per-state keys from channel base points and the per-commitment point. + /// Key set is asymmetric and can't be used as part of counter-signatory set of transactions. + 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)?, }) } + + /// Generate per-state keys from channel static keys. + /// Key set is asymmetric and can't be used as part of counter-signatory set of transactions. + pub fn from_channel_static_keys(per_commitment_point: &PublicKey, broadcaster_keys: &ChannelPublicKeys, countersignatory_keys: &ChannelPublicKeys, secp_ctx: &Secp256k1) -> Result { + TxCreationKeys::derive_new( + &secp_ctx, + &per_commitment_point, + &broadcaster_keys.delayed_payment_basepoint, + &broadcaster_keys.htlc_basepoint, + &countersignatory_keys.revocation_basepoint, + &countersignatory_keys.htlc_basepoint, + ) + } } -/// 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 { - Builder::new().push_opcode(opcodes::all::OP_IF) +/// The maximum length of a script returned by get_revokeable_redeemscript. +// Calculated as 6 bytes of opcodes, 1 byte push plus 2 bytes for contest_delay, and two public +// keys of 33 bytes (+ 1 push). +pub const REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH: usize = 6 + 3 + 34*2; + +/// 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 { + let res = 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() + .into_script(); + debug_assert!(res.len() <= REVOKEABLE_REDEEMSCRIPT_MAX_LENGTH); + res } #[derive(Clone, PartialEq)] @@ -331,7 +414,7 @@ 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. @@ -346,7 +429,10 @@ pub struct HTLCOutputInCommitment { pub transaction_output_index: Option, } -impl_writeable!(HTLCOutputInCommitment, 1 + 8 + 4 + 32 + 5, { +impl_writeable_len_match!(HTLCOutputInCommitment, { + { HTLCOutputInCommitment { transaction_output_index: None, .. }, HTLC_OUTPUT_IN_COMMITMENT_SIZE - 4 }, + { _, HTLC_OUTPUT_IN_COMMITMENT_SIZE } + }, { offered, amount_msat, cltv_expiry, @@ -355,17 +441,17 @@ 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 +460,7 @@ 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 +474,12 @@ 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 +490,7 @@ 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 +505,31 @@ 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 +542,14 @@ 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) }); @@ -475,154 +561,674 @@ 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(()); } +/// Per-channel data used to build transactions in conjunction with the per-commitment data (CommitmentTransaction). +/// The fields are organized by holder/counterparty. +/// +/// Normally, this is converted to the broadcaster/countersignatory-organized DirectedChannelTransactionParameters +/// before use, via the as_holder_broadcastable and as_counterparty_broadcastable functions. +#[derive(Clone)] +pub struct ChannelTransactionParameters { + /// Holder public keys + pub holder_pubkeys: ChannelPublicKeys, + /// The contest delay selected by the holder, which applies to counterparty-broadcast transactions + pub holder_selected_contest_delay: u16, + /// Whether the holder is the initiator of this channel. + /// This is an input to the commitment number obscure factor computation. + pub is_outbound_from_holder: bool, + /// The late-bound counterparty channel transaction parameters. + /// These parameters are populated at the point in the protocol where the counterparty provides them. + pub counterparty_parameters: Option, + /// The late-bound funding outpoint + pub funding_outpoint: Option, +} - let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&htlc, a_htlc_key, b_htlc_key, revocation_key); +/// Late-bound per-channel counterparty data used to build transactions. +#[derive(Clone)] +pub struct CounterpartyChannelTransactionParameters { + /// Counter-party public keys + pub pubkeys: ChannelPublicKeys, + /// The contest delay selected by the counterparty, which applies to holder-broadcast transactions + pub selected_contest_delay: u16, +} - 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); +impl ChannelTransactionParameters { + /// Whether the late bound parameters are populated. + pub fn is_populated(&self) -> bool { + self.counterparty_parameters.is_some() && self.funding_outpoint.is_some() + } - tx.input[0].witness.push(Vec::new()); // First is the multisig dummy + /// Convert the holder/counterparty parameters to broadcaster/countersignatory-organized parameters, + /// given that the holder is the broadcaster. + /// + /// self.is_populated() must be true before calling this function. + pub fn as_holder_broadcastable(&self) -> DirectedChannelTransactionParameters { + assert!(self.is_populated(), "self.late_parameters must be set before using as_holder_broadcastable"); + DirectedChannelTransactionParameters { + inner: self, + holder_is_broadcaster: true + } + } - 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()); + /// Convert the holder/counterparty parameters to broadcaster/countersignatory-organized parameters, + /// given that the counterparty is the broadcaster. + /// + /// self.is_populated() must be true before calling this function. + pub fn as_counterparty_broadcastable(&self) -> DirectedChannelTransactionParameters { + assert!(self.is_populated(), "self.late_parameters must be set before using as_counterparty_broadcastable"); + DirectedChannelTransactionParameters { + inner: self, + holder_is_broadcaster: false + } } - 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()); +impl_writeable!(CounterpartyChannelTransactionParameters, 0, { + pubkeys, + selected_contest_delay +}); + +impl_writeable!(ChannelTransactionParameters, 0, { + holder_pubkeys, + holder_selected_contest_delay, + is_outbound_from_holder, + counterparty_parameters, + funding_outpoint +}); + +/// Static channel fields used to build transactions given per-commitment fields, organized by +/// broadcaster/countersignatory. +/// +/// This is derived from the holder/counterparty-organized ChannelTransactionParameters via the +/// as_holder_broadcastable and as_counterparty_broadcastable functions. +pub struct DirectedChannelTransactionParameters<'a> { + /// The holder's channel static parameters + inner: &'a ChannelTransactionParameters, + /// Whether the holder is the broadcaster + holder_is_broadcaster: bool, +} + +impl<'a> DirectedChannelTransactionParameters<'a> { + /// Get the channel pubkeys for the broadcaster + pub fn broadcaster_pubkeys(&self) -> &ChannelPublicKeys { + if self.holder_is_broadcaster { + &self.inner.holder_pubkeys + } else { + &self.inner.counterparty_parameters.as_ref().unwrap().pubkeys + } + } + + /// Get the channel pubkeys for the countersignatory + pub fn countersignatory_pubkeys(&self) -> &ChannelPublicKeys { + if self.holder_is_broadcaster { + &self.inner.counterparty_parameters.as_ref().unwrap().pubkeys + } else { + &self.inner.holder_pubkeys + } + } + + /// Get the contest delay applicable to the transactions. + /// Note that the contest delay was selected by the countersignatory. + pub fn contest_delay(&self) -> u16 { + let counterparty_parameters = self.inner.counterparty_parameters.as_ref().unwrap(); + if self.holder_is_broadcaster { counterparty_parameters.selected_contest_delay } else { self.inner.holder_selected_contest_delay } } - tx.input[0].witness.push(htlc_redeemscript.as_bytes().to_vec()); + /// Whether the channel is outbound from the broadcaster. + /// + /// The boolean representing the side that initiated the channel is + /// an input to the commitment number obscure factor computation. + pub fn is_outbound(&self) -> bool { + if self.holder_is_broadcaster { self.inner.is_outbound_from_holder } else { !self.inner.is_outbound_from_holder } + } - Ok((our_sig, htlc_redeemscript)) + /// The funding outpoint + pub fn funding_outpoint(&self) -> OutPoint { + self.inner.funding_outpoint.unwrap().into_bitcoin_outpoint() + } } +/// Information needed to build and sign a holder's commitment transaction. +/// +/// The transaction is only signed once we are ready to broadcast. #[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 +pub struct HolderCommitmentTransaction { + inner: CommitmentTransaction, + /// Our counterparty's signature for the transaction + pub counterparty_sig: Signature, + /// All non-dust counterparty HTLC signatures, in the order they appear in the transaction + pub counterparty_htlc_sigs: Vec, + // Which order the signatures should go in when constructing the final commitment tx witness. + // The user should be able to reconstruct this themselves, so we don't bother to expose it. + holder_sig_first: bool, } -impl LocalCommitmentTransaction { - #[cfg(test)] - pub fn dummy() -> Self { - Self { tx: Transaction { - version: 2, - input: Vec::new(), - output: Vec::new(), - lock_time: 0, - } } - } - - 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 +impl Deref for HolderCommitmentTransaction { + type Target = CommitmentTransaction; - 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()); - } + fn deref(&self) -> &Self::Target { &self.inner } +} - Self { tx } +impl PartialEq for HolderCommitmentTransaction { + // We dont care whether we are signed in equality comparison + fn eq(&self, o: &Self) -> bool { + self.inner == o.inner } +} - pub fn txid(&self) -> Sha256dHash { - self.tx.txid() +impl_writeable!(HolderCommitmentTransaction, 0, { + inner, counterparty_sig, counterparty_htlc_sigs, holder_sig_first +}); + +impl HolderCommitmentTransaction { + #[cfg(test)] + pub fn dummy() -> Self { + let secp_ctx = Secp256k1::new(); + let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap()); + let dummy_sig = secp_ctx.sign(&secp256k1::Message::from_slice(&[42; 32]).unwrap(), &SecretKey::from_slice(&[42; 32]).unwrap()); + + let 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(), + }; + let channel_pubkeys = ChannelPublicKeys { + funding_pubkey: dummy_key.clone(), + revocation_basepoint: dummy_key.clone(), + payment_point: dummy_key.clone(), + delayed_payment_basepoint: dummy_key.clone(), + htlc_basepoint: dummy_key.clone() + }; + let channel_parameters = ChannelTransactionParameters { + holder_pubkeys: channel_pubkeys.clone(), + holder_selected_contest_delay: 0, + is_outbound_from_holder: false, + counterparty_parameters: Some(CounterpartyChannelTransactionParameters { pubkeys: channel_pubkeys.clone(), selected_contest_delay: 0 }), + funding_outpoint: Some(chain::transaction::OutPoint { txid: Default::default(), index: 0 }) + }; + let mut htlcs_with_aux: Vec<(_, ())> = Vec::new(); + let inner = CommitmentTransaction::new_with_auxiliary_htlc_data(0, 0, 0, keys, 0, &mut htlcs_with_aux, &channel_parameters.as_counterparty_broadcastable()); + HolderCommitmentTransaction { + inner, + counterparty_sig: dummy_sig, + counterparty_htlc_sigs: Vec::new(), + holder_sig_first: false + } } - 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 + /// Create a new holder transaction with the given counterparty signatures. + /// The funding keys are used to figure out which signature should go first when building the transaction for broadcast. + pub fn new(commitment_tx: CommitmentTransaction, counterparty_sig: Signature, counterparty_htlc_sigs: Vec, holder_funding_key: &PublicKey, counterparty_funding_key: &PublicKey) -> Self { + Self { + inner: commitment_tx, + counterparty_sig, + counterparty_htlc_sigs, + holder_sig_first: holder_funding_key.serialize()[..] < counterparty_funding_key.serialize()[..], } } - 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 { + // First push the multisig dummy, note that due to BIP147 (NULLDUMMY) it must be a zero-length element. + let mut tx = self.inner.built.transaction.clone(); + 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 } +} + +/// A pre-built Bitcoin commitment transaction and its txid. +#[derive(Clone)] +pub struct BuiltCommitmentTransaction { + /// The commitment transaction + pub transaction: Transaction, + /// The txid for the commitment transaction. + /// + /// This is provided as a performance optimization, instead of calling transaction.txid() + /// multiple times. + pub txid: Txid, +} - pub fn without_valid_witness(&self) -> &Transaction { &self.tx } - pub fn with_valid_witness(&self) -> &Transaction { - assert!(self.has_local_sig()); - &self.tx +impl_writeable!(BuiltCommitmentTransaction, 0, { transaction, txid }); + +impl BuiltCommitmentTransaction { + /// Get the SIGHASH_ALL sighash value of the transaction. + /// + /// This can be used to verify a signature. + pub fn get_sighash_all(&self, funding_redeemscript: &Script, channel_value_satoshis: u64) -> Message { + let sighash = &bip143::SigHashCache::new(&self.transaction).signature_hash(0, funding_redeemscript, channel_value_satoshis, SigHashType::All)[..]; + hash_to_message!(sighash) + } + + /// Sign a transaction, either because we are counter-signing the counterparty's transaction or + /// because we are about to broadcast a holder transaction. + pub fn sign(&self, funding_key: &SecretKey, funding_redeemscript: &Script, channel_value_satoshis: u64, secp_ctx: &Secp256k1) -> Signature { + let sighash = self.get_sighash_all(funding_redeemscript, channel_value_satoshis); + secp_ctx.sign(&sighash, funding_key) } } -impl PartialEq for LocalCommitmentTransaction { - // We dont care whether we are signed in equality comparison + +/// This class tracks the per-transaction information needed to build a commitment transaction and to +/// actually build it and sign. It is used for holder transactions that we sign only when needed +/// and for transactions we sign for the counterparty. +/// +/// This class can be used inside a signer implementation to generate a signature given the relevant +/// secret key. +#[derive(Clone)] +pub struct CommitmentTransaction { + commitment_number: u64, + to_broadcaster_value_sat: u64, + to_countersignatory_value_sat: u64, + feerate_per_kw: u32, + htlcs: Vec, + // A cache of the parties' pubkeys required to construct the transaction, see doc for trust() + keys: TxCreationKeys, + // For access to the pre-built transaction, see doc for trust() + built: BuiltCommitmentTransaction, +} + +impl PartialEq for CommitmentTransaction { fn eq(&self, o: &Self) -> bool { - self.txid() == o.txid() + let eq = self.commitment_number == o.commitment_number && + self.to_broadcaster_value_sat == o.to_broadcaster_value_sat && + self.to_countersignatory_value_sat == o.to_countersignatory_value_sat && + self.feerate_per_kw == o.feerate_per_kw && + self.htlcs == o.htlcs && + self.keys == o.keys; + if eq { + debug_assert_eq!(self.built.transaction, o.built.transaction); + debug_assert_eq!(self.built.txid, o.built.txid); + } + eq } } -impl Writeable for LocalCommitmentTransaction { - fn write(&self, writer: &mut W) -> Result<(), ::std::io::Error> { - if let Err(e) = self.tx.consensus_encode(&mut WriterWriteAdaptor(writer)) { - match e { - encode::Error::Io(e) => return Err(e), - _ => panic!("local tx must have been well-formed!"), - } + +/// (C-not exported) as users never need to call this directly +impl Writeable for Vec { + #[inline] + fn write(&self, w: &mut W) -> Result<(), ::std::io::Error> { + (self.len() as u16).write(w)?; + for e in self.iter() { + e.write(w)?; } Ok(()) } } -impl Readable for LocalCommitmentTransaction { - fn read(reader: &mut R) -> Result { - let 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), + +/// (C-not exported) as users never need to call this directly +impl Readable for Vec { + #[inline] + fn read(r: &mut R) -> Result { + let len: u16 = Readable::read(r)?; + let byte_size = (len as usize) + .checked_mul(HTLC_OUTPUT_IN_COMMITMENT_SIZE) + .ok_or(DecodeError::BadLengthDescriptor)?; + if byte_size > MAX_BUF_SIZE { + return Err(DecodeError::BadLengthDescriptor); + } + let mut ret = Vec::with_capacity(len as usize); + for _ in 0..len { ret.push(HTLCOutputInCommitment::read(r)?); } + Ok(ret) + } +} + +impl_writeable!(CommitmentTransaction, 0, { + commitment_number, + to_broadcaster_value_sat, + to_countersignatory_value_sat, + feerate_per_kw, + htlcs, + keys, + built +}); + +impl CommitmentTransaction { + /// Construct an object of the class while assigning transaction output indices to HTLCs. + /// + /// Populates HTLCOutputInCommitment.transaction_output_index in htlcs_with_aux. + /// + /// The generic T allows the caller to match the HTLC output index with auxiliary data. + /// This auxiliary data is not stored in this object. + /// + /// Only include HTLCs that are above the dust limit for the channel. + /// + /// (C-not exported) due to the generic though we likely should expose a version without + pub fn new_with_auxiliary_htlc_data(commitment_number: u64, to_broadcaster_value_sat: u64, to_countersignatory_value_sat: u64, keys: TxCreationKeys, feerate_per_kw: u32, htlcs_with_aux: &mut Vec<(HTLCOutputInCommitment, T)>, channel_parameters: &DirectedChannelTransactionParameters) -> CommitmentTransaction { + // Sort outputs and populate output indices while keeping track of the auxiliary data + let (outputs, htlcs) = Self::internal_build_outputs(&keys, to_broadcaster_value_sat, to_countersignatory_value_sat, htlcs_with_aux, channel_parameters).unwrap(); + + let (obscured_commitment_transaction_number, txins) = Self::internal_build_inputs(commitment_number, channel_parameters); + let transaction = Self::make_transaction(obscured_commitment_transaction_number, txins, outputs); + let txid = transaction.txid(); + CommitmentTransaction { + commitment_number, + to_broadcaster_value_sat, + to_countersignatory_value_sat, + feerate_per_kw, + htlcs, + keys, + built: BuiltCommitmentTransaction { + transaction, + txid }, + } + } + + fn internal_rebuild_transaction(&self, keys: &TxCreationKeys, channel_parameters: &DirectedChannelTransactionParameters) -> Result { + let (obscured_commitment_transaction_number, txins) = Self::internal_build_inputs(self.commitment_number, channel_parameters); + + let mut htlcs_with_aux = self.htlcs.iter().map(|h| (h.clone(), ())).collect(); + let (outputs, _) = Self::internal_build_outputs(keys, self.to_broadcaster_value_sat, self.to_countersignatory_value_sat, &mut htlcs_with_aux, channel_parameters)?; + + let transaction = Self::make_transaction(obscured_commitment_transaction_number, txins, outputs); + let txid = transaction.txid(); + let built_transaction = BuiltCommitmentTransaction { + transaction, + txid }; + Ok(built_transaction) + } + + fn make_transaction(obscured_commitment_transaction_number: u64, txins: Vec, outputs: Vec) -> Transaction { + Transaction { + version: 2, + lock_time: ((0x20 as u32) << 8 * 3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32), + input: txins, + output: outputs, + } + } + + // This is used in two cases: + // - initial sorting of outputs / HTLCs in the constructor, in which case T is auxiliary data the + // caller needs to have sorted together with the HTLCs so it can keep track of the output index + // - building of a bitcoin transaction during a verify() call, in which case T is just () + fn internal_build_outputs(keys: &TxCreationKeys, to_broadcaster_value_sat: u64, to_countersignatory_value_sat: u64, htlcs_with_aux: &mut Vec<(HTLCOutputInCommitment, T)>, channel_parameters: &DirectedChannelTransactionParameters) -> Result<(Vec, Vec), ()> { + let countersignatory_pubkeys = channel_parameters.countersignatory_pubkeys(); + let contest_delay = channel_parameters.contest_delay(); + + let mut txouts: Vec<(TxOut, Option<&mut HTLCOutputInCommitment>)> = Vec::new(); + + if to_countersignatory_value_sat > 0 { + let script = script_for_p2wpkh(&countersignatory_pubkeys.payment_point); + txouts.push(( + TxOut { + script_pubkey: script.clone(), + value: to_countersignatory_value_sat, + }, + None, + )) + } + + if to_broadcaster_value_sat > 0 { + let redeem_script = get_revokeable_redeemscript( + &keys.revocation_key, + contest_delay, + &keys.broadcaster_delayed_payment_key, + ); + txouts.push(( + TxOut { + script_pubkey: redeem_script.to_v0_p2wsh(), + value: to_broadcaster_value_sat, + }, + None, + )); + } + + let mut htlcs = Vec::with_capacity(htlcs_with_aux.len()); + for (htlc, _) in htlcs_with_aux { + let script = chan_utils::get_htlc_redeemscript(&htlc, &keys); + let txout = TxOut { + script_pubkey: script.to_v0_p2wsh(), + value: htlc.amount_msat / 1000, + }; + txouts.push((txout, Some(htlc))); + } - if tx.input.len() != 1 { - // Ensure tx didn't hit the 0-input ambiguity case. - return Err(DecodeError::InvalidValue); + // Sort output in BIP-69 order (amount, scriptPubkey). Tie-breaks based on HTLC + // CLTV expiration height. + sort_outputs(&mut txouts, |a, b| { + if let &Some(ref a_htlcout) = a { + if let &Some(ref b_htlcout) = b { + a_htlcout.cltv_expiry.cmp(&b_htlcout.cltv_expiry) + // Note that due to hash collisions, we have to have a fallback comparison + // here for fuzztarget mode (otherwise at least chanmon_fail_consistency + // may fail)! + .then(a_htlcout.payment_hash.0.cmp(&b_htlcout.payment_hash.0)) + // For non-HTLC outputs, if they're copying our SPK we don't really care if we + // close the channel due to mismatches - they're doing something dumb: + } else { cmp::Ordering::Equal } + } else { cmp::Ordering::Equal } + }); + + let mut outputs = Vec::with_capacity(txouts.len()); + for (idx, out) in txouts.drain(..).enumerate() { + if let Some(htlc) = out.1 { + htlc.transaction_output_index = Some(idx as u32); + htlcs.push(htlc.clone()); + } + outputs.push(out.0); } - Ok(Self { tx }) + Ok((outputs, htlcs)) + } + + fn internal_build_inputs(commitment_number: u64, channel_parameters: &DirectedChannelTransactionParameters) -> (u64, Vec) { + let broadcaster_pubkeys = channel_parameters.broadcaster_pubkeys(); + let countersignatory_pubkeys = channel_parameters.countersignatory_pubkeys(); + let commitment_transaction_number_obscure_factor = get_commitment_transaction_number_obscure_factor( + &broadcaster_pubkeys.payment_point, + &countersignatory_pubkeys.payment_point, + channel_parameters.is_outbound(), + ); + + let obscured_commitment_transaction_number = + commitment_transaction_number_obscure_factor ^ (INITIAL_COMMITMENT_NUMBER - commitment_number); + + let txins = { + let mut ins: Vec = Vec::new(); + ins.push(TxIn { + previous_output: channel_parameters.funding_outpoint(), + script_sig: Script::new(), + sequence: ((0x80 as u32) << 8 * 3) + | ((obscured_commitment_transaction_number >> 3 * 8) as u32), + witness: Vec::new(), + }); + ins + }; + (obscured_commitment_transaction_number, txins) } + + /// The backwards-counting commitment number + pub fn commitment_number(&self) -> u64 { + self.commitment_number + } + + /// The value to be sent to the broadcaster + pub fn to_broadcaster_value_sat(&self) -> u64 { + self.to_broadcaster_value_sat + } + + /// The value to be sent to the counterparty + pub fn to_countersignatory_value_sat(&self) -> u64 { + self.to_countersignatory_value_sat + } + + /// The feerate paid per 1000-weight-unit in this commitment transaction. + pub fn feerate_per_kw(&self) -> u32 { + self.feerate_per_kw + } + + /// The non-dust HTLCs (direction, amt, height expiration, hash, transaction output index) + /// which were included in this commitment transaction in output order. + /// The transaction index is always populated. + /// + /// (C-not exported) as we cannot currently convert Vec references to/from C, though we should + /// expose a less effecient version which creates a Vec of references in the future. + pub fn htlcs(&self) -> &Vec { + &self.htlcs + } + + /// Trust our pre-built transaction and derived transaction creation public keys. + /// + /// Applies a wrapper which allows access to these fields. + /// + /// This should only be used if you fully trust the builder of this object. It should not + /// be used by an external signer - instead use the verify function. + pub fn trust(&self) -> TrustedCommitmentTransaction { + TrustedCommitmentTransaction { inner: self } + } + + /// Verify our pre-built transaction and derived transaction creation public keys. + /// + /// Applies a wrapper which allows access to these fields. + /// + /// An external validating signer must call this method before signing + /// or using the built transaction. + pub fn verify(&self, channel_parameters: &DirectedChannelTransactionParameters, broadcaster_keys: &ChannelPublicKeys, countersignatory_keys: &ChannelPublicKeys, secp_ctx: &Secp256k1) -> Result { + // This is the only field of the key cache that we trust + let per_commitment_point = self.keys.per_commitment_point; + let keys = TxCreationKeys::from_channel_static_keys(&per_commitment_point, broadcaster_keys, countersignatory_keys, secp_ctx).unwrap(); + if keys != self.keys { + return Err(()); + } + let tx = self.internal_rebuild_transaction(&keys, channel_parameters)?; + if self.built.transaction != tx.transaction || self.built.txid != tx.txid { + return Err(()); + } + Ok(TrustedCommitmentTransaction { inner: self }) + } +} + +/// A wrapper on CommitmentTransaction indicating that the derived fields (the built bitcoin +/// transaction and the transaction creation keys) are trusted. +/// +/// See trust() and verify() functions on CommitmentTransaction. +/// +/// This structure implements Deref. +pub struct TrustedCommitmentTransaction<'a> { + inner: &'a CommitmentTransaction, +} + +impl<'a> Deref for TrustedCommitmentTransaction<'a> { + type Target = CommitmentTransaction; + + fn deref(&self) -> &Self::Target { self.inner } +} + +impl<'a> TrustedCommitmentTransaction<'a> { + /// The transaction ID of the built Bitcoin transaction + pub fn txid(&self) -> Txid { + self.inner.built.txid + } + + /// The pre-built Bitcoin commitment transaction + pub fn built_transaction(&self) -> &BuiltCommitmentTransaction { + &self.inner.built + } + + /// The pre-calculated transaction creation public keys. + pub fn keys(&self) -> &TxCreationKeys { + &self.inner.keys + } + + /// 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. + pub fn get_htlc_sigs(&self, htlc_base_key: &SecretKey, channel_parameters: &DirectedChannelTransactionParameters, secp_ctx: &Secp256k1) -> Result, ()> { + let inner = self.inner; + let keys = &inner.keys; + let txid = inner.built.txid; + let mut ret = Vec::with_capacity(inner.htlcs.len()); + let holder_htlc_key = derive_private_key(secp_ctx, &inner.keys.per_commitment_point, htlc_base_key).map_err(|_| ())?; + + for this_htlc in inner.htlcs.iter() { + assert!(this_htlc.transaction_output_index.is_some()); + let htlc_tx = build_htlc_transaction(&txid, inner.feerate_per_kw, channel_parameters.contest_delay(), &this_htlc, &keys.broadcaster_delayed_payment_key, &keys.revocation_key); + + let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc, &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &keys.revocation_key); + + let sighash = hash_to_message!(&bip143::SigHashCache::new(&htlc_tx).signature_hash(0, &htlc_redeemscript, this_htlc.amount_msat / 1000, SigHashType::All)[..]); + ret.push(secp_ctx.sign(&sighash, &holder_htlc_key)); + } + 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, channel_parameters: &DirectedChannelTransactionParameters, htlc_index: usize, counterparty_signature: &Signature, signature: &Signature, preimage: &Option) -> Transaction { + let inner = self.inner; + let keys = &inner.keys; + let txid = inner.built.txid; + let this_htlc = &inner.htlcs[htlc_index]; + assert!(this_htlc.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.offered && preimage.is_none() { unreachable!(); } + // Further, we should never be provided the preimage for an HTLC-Timeout transaction. + if this_htlc.offered && preimage.is_some() { unreachable!(); } + + let mut htlc_tx = build_htlc_transaction(&txid, inner.feerate_per_kw, channel_parameters.contest_delay(), &this_htlc, &keys.broadcaster_delayed_payment_key, &keys.revocation_key); + + let htlc_redeemscript = get_htlc_redeemscript_with_explicit_keys(&this_htlc, &keys.broadcaster_htlc_key, &keys.countersignatory_htlc_key, &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(counterparty_signature.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.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 + } +} + +/// Get the transaction number obscure factor +pub fn get_commitment_transaction_number_obscure_factor( + broadcaster_payment_basepoint: &PublicKey, + countersignatory_payment_basepoint: &PublicKey, + outbound_from_broadcaster: bool, +) -> u64 { + let mut sha = Sha256::engine(); + + if outbound_from_broadcaster { + sha.input(&broadcaster_payment_basepoint.serialize()); + sha.input(&countersignatory_payment_basepoint.serialize()); + } else { + sha.input(&countersignatory_payment_basepoint.serialize()); + sha.input(&broadcaster_payment_basepoint.serialize()); + } + let res = Sha256::from_engine(sha).into_inner(); + + ((res[26] as u64) << 5 * 8) + | ((res[27] as u64) << 4 * 8) + | ((res[28] as u64) << 3 * 8) + | ((res[29] as u64) << 2 * 8) + | ((res[30] as u64) << 1 * 8) + | ((res[31] as u64) << 0 * 8) +} + +fn script_for_p2wpkh(key: &PublicKey) -> Script { + Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0) + .push_slice(&WPubkeyHash::hash(&key.serialize())[..]) + .into_script() } #[cfg(test)]