// 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. //! Structs and traits which allow other parts of rust-lightning to interact with the blockchain. use bitcoin::blockdata::block::{Block, BlockHeader}; use bitcoin::blockdata::constants::genesis_block; use bitcoin::blockdata::script::Script; use bitcoin::blockdata::transaction::TxOut; use bitcoin::hash_types::{BlockHash, Txid}; use bitcoin::network::constants::Network; use bitcoin::secp256k1::PublicKey; use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent}; use chain::keysinterface::Sign; use chain::transaction::{OutPoint, TransactionData}; use prelude::*; pub mod chaininterface; pub mod chainmonitor; pub mod channelmonitor; pub mod transaction; pub mod keysinterface; pub(crate) mod onchaintx; pub(crate) mod package; /// The best known block as identified by its hash and height. #[derive(Clone, Copy, PartialEq)] pub struct BestBlock { block_hash: BlockHash, height: u32, } impl BestBlock { /// Constructs a `BestBlock` that represents the genesis block at height 0 of the given /// network. pub fn from_genesis(network: Network) -> Self { BestBlock { block_hash: genesis_block(network).header.block_hash(), height: 0, } } /// Returns a `BestBlock` as identified by the given block hash and height. pub fn new(block_hash: BlockHash, height: u32) -> Self { BestBlock { block_hash, height } } /// Returns the best block hash. pub fn block_hash(&self) -> BlockHash { self.block_hash } /// Returns the best block height. pub fn height(&self) -> u32 { self.height } } /// An error when accessing the chain via [`Access`]. #[derive(Clone, Debug)] pub enum AccessError { /// The requested chain is unknown. UnknownChain, /// The requested transaction doesn't exist or hasn't confirmed. UnknownTx, } /// The `Access` trait defines behavior for accessing chain data and state, such as blocks and /// UTXOs. pub trait Access { /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`]. /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output /// is unknown. /// /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result; } /// The `Listen` trait is used to notify when blocks have been connected or disconnected from the /// chain. /// /// Useful when needing to replay chain data upon startup or as new chain events occur. Clients /// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`]. /// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers /// when needed. /// /// By using [`Listen::filtered_block_connected`] this interface supports clients fetching the /// entire header chain and only blocks with matching transaction data using BIP 157 filters or /// other similar filtering. pub trait Listen { /// Notifies the listener that a block was added at the given height, with the transaction data /// possibly filtered. fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32); /// Notifies the listener that a block was added at the given height. fn block_connected(&self, block: &Block, height: u32) { let txdata: Vec<_> = block.txdata.iter().enumerate().collect(); self.filtered_block_connected(&block.header, &txdata, height); } /// Notifies the listener that a block was removed at the given height. fn block_disconnected(&self, header: &BlockHeader, height: u32); } /// The `Confirm` trait is used to notify when transactions have been confirmed on chain or /// unconfirmed during a chain reorganization. /// /// Clients sourcing chain data using a transaction-oriented API should prefer this interface over /// [`Listen`]. For instance, an Electrum client may implement [`Filter`] by subscribing to activity /// related to registered transactions and outputs. Upon notification, it would pass along the /// matching transactions using this interface. /// /// # Use /// /// The intended use is as follows: /// - Call [`transactions_confirmed`] to process any on-chain activity of interest. /// - Call [`transaction_unconfirmed`] to process any transaction returned by [`get_relevant_txids`] /// that has been reorganized out of the chain. /// - Call [`best_block_updated`] whenever a new chain tip becomes available. /// /// # Order /// /// Clients must call these methods in chain order. Specifically: /// - Transactions confirmed in a block must be given before transactions confirmed in a later /// block. /// - Dependent transactions within the same block must be given in topological order, possibly in /// separate calls. /// - Unconfirmed transactions must be given after the original confirmations and before any /// reconfirmation. /// /// See individual method documentation for further details. /// /// [`transactions_confirmed`]: Self::transactions_confirmed /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed /// [`best_block_updated`]: Self::best_block_updated /// [`get_relevant_txids`]: Self::get_relevant_txids pub trait Confirm { /// Processes transactions confirmed in a block with a given header and height. /// /// Should be called for any transactions registered by [`Filter::register_tx`] or any /// transactions spending an output registered by [`Filter::register_output`]. Such transactions /// appearing in the same block do not need to be included in the same call; instead, multiple /// calls with additional transactions may be made so long as they are made in [chain order]. /// /// May be called before or after [`best_block_updated`] for the corresponding block. However, /// in the event of a chain reorganization, it must not be called with a `header` that is no /// longer in the chain as of the last call to [`best_block_updated`]. /// /// [chain order]: Confirm#order /// [`best_block_updated`]: Self::best_block_updated fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32); /// Processes a transaction that is no longer confirmed as result of a chain reorganization. /// /// Should be called for any transaction returned by [`get_relevant_txids`] if it has been /// reorganized out of the best chain. Once called, the given transaction will not be returned /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`]. /// /// [`get_relevant_txids`]: Self::get_relevant_txids /// [`transactions_confirmed`]: Self::transactions_confirmed fn transaction_unconfirmed(&self, txid: &Txid); /// Processes an update to the best header connected at the given height. /// /// Should be called when a new header is available but may be skipped for intermediary blocks /// if they become available at the same time. fn best_block_updated(&self, header: &BlockHeader, height: u32); /// Returns transactions that should be monitored for reorganization out of the chain. /// /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient /// confirmations to be safe from a chain reorganization. Will not include any transactions /// passed to [`transaction_unconfirmed`], unless later reconfirmed. /// /// May be called to determine the subset of transactions that must still be monitored for /// reorganization. Will be idempotent between calls but may change as a result of calls to the /// other interface methods. Thus, this is useful to determine which transactions may need to be /// given to [`transaction_unconfirmed`]. /// /// [`transactions_confirmed`]: Self::transactions_confirmed /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed fn get_relevant_txids(&self) -> Vec; } /// An error enum representing a failure to persist a channel monitor update. #[derive(Clone, Copy, Debug, PartialEq)] pub enum ChannelMonitorUpdateErr { /// Used to indicate a temporary failure (eg connection to a watchtower or remote backup of /// our state failed, but is expected to succeed at some point in the future). /// /// Such a failure will "freeze" a channel, preventing us from revoking old states or /// submitting new commitment transactions to the counterparty. Once the update(s) that failed /// have been successfully applied, a [`MonitorEvent::UpdateCompleted`] event should be returned /// via [`Watch::release_pending_monitor_events`] which will then restore the channel to an /// operational state. /// /// Note that a given ChannelManager will *never* re-generate a given ChannelMonitorUpdate. If /// you return a TemporaryFailure you must ensure that it is written to disk safely before /// writing out the latest ChannelManager state. /// /// Even when a channel has been "frozen" updates to the ChannelMonitor can continue to occur /// (eg if an inbound HTLC which we forwarded was claimed upstream resulting in us attempting /// to claim it on this channel) and those updates must be applied wherever they can be. At /// least one such updated ChannelMonitor must be persisted otherwise PermanentFailure should /// be returned to get things on-chain ASAP using only the in-memory copy. Obviously updates to /// the channel which would invalidate previous ChannelMonitors are not made when a channel has /// been "frozen". /// /// Note that even if updates made after TemporaryFailure succeed you must still provide a /// [`MonitorEvent::UpdateCompleted`] to ensure you have the latest monitor and re-enable /// normal channel operation. Note that this is normally generated through a call to /// [`ChainMonitor::channel_monitor_updated`]. /// /// Note that the update being processed here will not be replayed for you when you return a /// [`MonitorEvent::UpdateCompleted`] event via [`Watch::release_pending_monitor_events`], so /// you must store the update itself on your own local disk prior to returning a /// TemporaryFailure. You may, of course, employ a journaling approach, storing only the /// ChannelMonitorUpdate on disk without updating the monitor itself, replaying the journal at /// reload-time. /// /// For deployments where a copy of ChannelMonitors and other local state are backed up in a /// remote location (with local copies persisted immediately), it is anticipated that all /// updates will return TemporaryFailure until the remote copies could be updated. /// /// [`ChainMonitor::channel_monitor_updated`]: chainmonitor::ChainMonitor::channel_monitor_updated TemporaryFailure, /// Used to indicate no further channel monitor updates will be allowed (eg we've moved on to a /// different watchtower and cannot update with all watchtowers that were previously informed /// of this channel). /// /// At reception of this error, ChannelManager will force-close the channel and return at /// least a final ChannelMonitorUpdate::ChannelForceClosed which must be delivered to at /// least one ChannelMonitor copy. Revocation secret MUST NOT be released and offchain channel /// update must be rejected. /// /// This failure may also signal a failure to update the local persisted copy of one of /// the channel monitor instance. /// /// Note that even when you fail a holder commitment transaction update, you must store the /// update to ensure you can claim from it in case of a duplicate copy of this ChannelMonitor /// broadcasts it (e.g distributed channel-monitor deployment) /// /// In case of distributed watchtowers deployment, the new version must be written to disk, as /// state may have been stored but rejected due to a block forcing a commitment broadcast. This /// storage is used to claim outputs of rejected state confirmed onchain by another watchtower, /// lagging behind on block processing. PermanentFailure, } /// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as /// blocks are connected and disconnected. /// /// Each channel is associated with a [`ChannelMonitor`]. Implementations of this trait are /// responsible for maintaining a set of monitors such that they can be updated accordingly as /// channel state changes and HTLCs are resolved. See method documentation for specific /// requirements. /// /// Implementations **must** ensure that updates are successfully applied and persisted upon method /// completion. If an update fails with a [`PermanentFailure`], then it must immediately shut down /// without taking any further action such as persisting the current state. /// /// If an implementation maintains multiple instances of a channel's monitor (e.g., by storing /// backup copies), then it must ensure that updates are applied across all instances. Otherwise, it /// could result in a revoked transaction being broadcast, allowing the counterparty to claim all /// funds in the channel. See [`ChannelMonitorUpdateErr`] for more details about how to handle /// multiple instances. /// /// [`PermanentFailure`]: ChannelMonitorUpdateErr::PermanentFailure pub trait Watch { /// Watches a channel identified by `funding_txo` using `monitor`. /// /// Implementations are responsible for watching the chain for the funding transaction along /// with any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means /// calling [`block_connected`] and [`block_disconnected`] on the monitor. /// /// Note: this interface MUST error with `ChannelMonitorUpdateErr::PermanentFailure` if /// the given `funding_txo` has previously been registered via `watch_channel`. /// /// [`get_outputs_to_watch`]: channelmonitor::ChannelMonitor::get_outputs_to_watch /// [`block_connected`]: channelmonitor::ChannelMonitor::block_connected /// [`block_disconnected`]: channelmonitor::ChannelMonitor::block_disconnected fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor) -> Result<(), ChannelMonitorUpdateErr>; /// Updates a channel identified by `funding_txo` by applying `update` to its monitor. /// /// Implementations must call [`update_monitor`] with the given update. See /// [`ChannelMonitorUpdateErr`] for invariants around returning an error. /// /// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr>; /// Returns any monitor events since the last call. Subsequent calls must only return new /// events. /// /// Note that after any block- or transaction-connection calls to a [`ChannelMonitor`], no /// further events may be returned here until the [`ChannelMonitor`] has been fully persisted /// to disk. /// /// For details on asynchronous [`ChannelMonitor`] updating and returning /// [`MonitorEvent::UpdateCompleted`] here, see [`ChannelMonitorUpdateErr::TemporaryFailure`]. fn release_pending_monitor_events(&self) -> Vec<(OutPoint, Vec, Option)>; } /// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to /// channels. /// /// This is useful in order to have a [`Watch`] implementation convey to a chain source which /// transactions to be notified of. Notification may take the form of pre-filtering blocks or, in /// the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If /// receiving full blocks from a chain source, any further filtering is unnecessary. /// /// After an output has been registered, subsequent block retrievals from the chain source must not /// exclude any transactions matching the new criteria nor any in-block descendants of such /// transactions. /// /// Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter` /// should not block on I/O. Implementations should instead queue the newly monitored data to be /// processed later. Then, in order to block until the data has been processed, any [`Watch`] /// invocation that has called the `Filter` must return [`TemporaryFailure`]. /// /// [`TemporaryFailure`]: ChannelMonitorUpdateErr::TemporaryFailure /// [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki /// [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki pub trait Filter { /// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as /// a spending condition. fn register_tx(&self, txid: &Txid, script_pubkey: &Script); /// Registers interest in spends of a transaction output. /// /// Note that this method might be called during processing of a new block. You therefore need /// to ensure that also dependent output spents within an already connected block are correctly /// handled, e.g., by re-scanning the block in question whenever new outputs have been /// registered mid-processing. fn register_output(&self, output: WatchedOutput); } /// A transaction output watched by a [`ChannelMonitor`] for spends on-chain. /// /// Used to convey to a [`Filter`] such an output with a given spending condition. Any transaction /// spending the output must be given to [`ChannelMonitor::block_connected`] either directly or via /// [`Confirm::transactions_confirmed`]. /// /// If `block_hash` is `Some`, this indicates the output was created in the corresponding block and /// may have been spent there. See [`Filter::register_output`] for details. /// /// [`ChannelMonitor`]: channelmonitor::ChannelMonitor /// [`ChannelMonitor::block_connected`]: channelmonitor::ChannelMonitor::block_connected #[derive(Clone, PartialEq, Hash)] pub struct WatchedOutput { /// First block where the transaction output may have been spent. pub block_hash: Option, /// Outpoint identifying the transaction output. pub outpoint: OutPoint, /// Spending condition of the transaction output. pub script_pubkey: Script, } impl Listen for core::ops::Deref { fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) { (**self).filtered_block_connected(header, txdata, height); } fn block_disconnected(&self, header: &BlockHeader, height: u32) { (**self).block_disconnected(header, height); } } impl Listen for (T, U) where T::Target: Listen, U::Target: Listen, { fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) { self.0.filtered_block_connected(header, txdata, height); self.1.filtered_block_connected(header, txdata, height); } fn block_disconnected(&self, header: &BlockHeader, height: u32) { self.0.block_disconnected(header, height); self.1.block_disconnected(header, height); } }