X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fln%2Fchan_utils.rs;h=4438579657eecc74e6cf1cb9458b339c2db82292;hb=f24bbd63cc72e32efaa23844f19f4a7952fb22cb;hp=7b7d511d653e0553e2fb41d44cd97c2a31adf445;hpb=52673d480e615b8b5113435e588da24267316c2e;p=rust-lightning diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs index 7b7d511d..44385796 100644 --- a/lightning/src/ln/chan_utils.rs +++ b/lightning/src/ln/chan_utils.rs @@ -8,14 +8,11 @@ // 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::{Decodable, Encodable}; -use bitcoin::consensus::encode; use bitcoin::util::bip143; use bitcoin::hashes::{Hash, HashEngine}; @@ -23,19 +20,32 @@ 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 bitcoin::hash_types::WPubkeyHash; use bitcoin::secp256k1::key::{SecretKey, PublicKey}; -use bitcoin::secp256k1::{Secp256k1, Signature}; +use bitcoin::secp256k1::{Secp256k1, Signature, Message}; use bitcoin::secp256k1::Error as SecpError; use bitcoin::secp256k1; -use std::{cmp, mem}; +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; -const MAX_ALLOC_SIZE: usize = 64*1024; +// 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; @@ -294,7 +304,7 @@ pub fn derive_public_revocation_key(secp_ctx: &Secp2 /// /// 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 +/// CommitmentTransaction.trust().keys() because we trusted the source of the /// pre-calculated keys. #[derive(PartialEq, Clone)] pub struct TxCreationKeys { @@ -311,33 +321,9 @@ pub struct TxCreationKeys { /// 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, 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. -#[derive(PartialEq, Clone)] -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 - } -} +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)] @@ -373,7 +359,8 @@ impl_writeable!(ChannelPublicKeys, 33*5, { impl TxCreationKeys { - /// Create a new TxCreationKeys from channel base points and the per-commitment point + /// 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(), @@ -383,13 +370,31 @@ impl TxCreationKeys { 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, + ) + } } +/// 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 { - Builder::new().push_opcode(opcodes::all::OP_IF) + let res = Builder::new().push_opcode(opcodes::all::OP_IF) .push_slice(&revocation_key.serialize()) .push_opcode(opcodes::all::OP_ELSE) .push_int(contest_delay as i64) @@ -398,7 +403,9 @@ pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, contest_delay: u1 .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)] @@ -422,7 +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, @@ -551,130 +561,216 @@ pub fn build_htlc_transaction(prev_hash: &Txid, feerate_per_kw: u32, contest_del } } +/// 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, +} + +/// 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, +} + +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() + } + + /// 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 + } + } + + /// 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 + } + } +} + +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 } + } + + /// 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 } + } + + /// 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 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. + 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 reconstruc this themselves, so we don't bother to expose it. + // The user should be able to reconstruct 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 Deref for HolderCommitmentTransaction { + type Target = CommitmentTransaction; + + fn deref(&self) -> &Self::Target { &self.inner } +} + +impl PartialEq for HolderCommitmentTransaction { + // We dont care whether we are signed in equality comparison + fn eq(&self, o: &Self) -> bool { + self.inner == o.inner + } +} + +impl_writeable!(HolderCommitmentTransaction, 0, { + inner, counterparty_sig, counterparty_htlc_sigs, holder_sig_first +}); + impl HolderCommitmentTransaction { #[cfg(test)] pub fn dummy() -> Self { - let dummy_input = TxIn { - previous_output: OutPoint { - txid: Default::default(), - vout: 0, - }, - script_sig: Default::default(), - sequence: 0, - witness: vec![] + 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 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, - }, + 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, - 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() + counterparty_htlc_sigs: Vec::new(), + holder_sig_first: false } } - /// 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); - } - } - } - + /// 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 { - unsigned_tx, + inner: commitment_tx, counterparty_sig, + counterparty_htlc_sigs, holder_sig_first: holder_funding_key.serialize()[..] < counterparty_funding_key.serialize()[..], - keys, - feerate_per_kw, - per_htlc: htlc_data, } } - /// 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 - } - - /// Get the txid of the holder commitment transaction contained in this - /// HolderCommitmentTransaction - pub fn txid(&self) -> Txid { - self.unsigned_tx.txid() - } - - /// 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(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. + let mut tx = self.inner.built.transaction.clone(); tx.input[0].witness.push(Vec::new()); if self.holder_sig_first { @@ -690,59 +786,409 @@ impl HolderCommitmentTransaction { 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, +} + +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) + } +} + +/// 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 { + 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 + } +} + +/// (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(()) + } +} + +/// (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))); + } + + // 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((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. 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); - } + /// 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, 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()); + 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.0.offered && preimage.is_none() { unreachable!(); } + if !this_htlc.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!(); } + if this_htlc.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 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.0, &self.keys.broadcaster_htlc_key, &self.keys.countersignatory_htlc_key, &self.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(this_htlc.1.unwrap().serialize_der().to_vec()); + 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.0.offered { + 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 { @@ -753,66 +1199,36 @@ impl HolderCommitmentTransaction { htlc_tx } } -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 HolderCommitmentTransaction { - fn write(&self, writer: &mut W) -> Result<(), ::std::io::Error> { - if let Err(e) = self.unsigned_tx.consensus_encode(&mut WriterWriteAdaptor(writer)) { - match e { - encode::Error::Io(e) => return Err(e), - _ => 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(()) + +/// 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) } -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 unsigned_tx.input.len() != 1 { - // Ensure tx didn't hit the 0-input ambiguity case. - return Err(DecodeError::InvalidValue); - } - Ok(Self { - unsigned_tx, - counterparty_sig, - holder_sig_first, - keys, - feerate_per_kw, - per_htlc, - }) - } +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)]