_ Git - rust-lightning/blob - lightning-transaction-sync/src/electrum.rs

   1 use crate::common::{ConfirmedTx, SyncState, FilterQueue};
   2 use crate::error::{TxSyncError, InternalError};
   3
   4 use electrum_client::Client as ElectrumClient;
   5 use electrum_client::ElectrumApi;
   6 use electrum_client::GetMerkleRes;
   7
   8 use lightning::util::logger::Logger;
   9 use lightning::{log_error, log_debug, log_trace};
  10 use lightning::chain::WatchedOutput;
  11 use lightning::chain::{Confirm, Filter};
  12
  13 use bitcoin::{BlockHash, Script, Transaction, Txid};
  14 use bitcoin::block::Header;
  15 use bitcoin::hash_types::TxMerkleNode;
  16 use bitcoin::hashes::Hash;
  17 use bitcoin::hashes::sha256d::Hash as Sha256d;
  18
  19 use std::ops::Deref;
  20 use std::sync::Mutex;
  21 use std::collections::HashSet;
  22 use std::time::Instant;
  23
  24 /// Synchronizes LDK with a given Electrum server.
  25 ///
  26 /// Needs to be registered with a [`ChainMonitor`] via the [`Filter`] interface to be informed of
  27 /// transactions and outputs to monitor for on-chain confirmation, unconfirmation, and
  28 /// reconfirmation.
  29 ///
  30 /// Note that registration via [`Filter`] needs to happen before any calls to
  31 /// [`Watch::watch_channel`] to ensure we get notified of the items to monitor.
  32 ///
  33 /// [`ChainMonitor`]: lightning::chain::chainmonitor::ChainMonitor
  34 /// [`Watch::watch_channel`]: lightning::chain::Watch::watch_channel
  35 /// [`Filter`]: lightning::chain::Filter
  36 pub struct ElectrumSyncClient<L: Deref>
  37 where
  38         L::Target: Logger,
  39 {
  40         sync_state: Mutex<SyncState>,
  41         queue: Mutex<FilterQueue>,
  42         client: ElectrumClient,
  43         logger: L,
  44 }
  45
  46 impl<L: Deref> ElectrumSyncClient<L>
  47 where
  48         L::Target: Logger,
  49 {
  50         /// Returns a new [`ElectrumSyncClient`] object.
  51         pub fn new(server_url: String, logger: L) -> Result<Self, TxSyncError> {
  52                 let client = ElectrumClient::new(&server_url).map_err(|e| {
  53                         log_error!(logger, "Failed to connect to electrum server '{}': {}", server_url, e);
  54                         e
  55                 })?;
  56
  57                 Self::from_client(client, logger)
  58         }
  59
  60         /// Returns a new [`ElectrumSyncClient`] object using the given Electrum client.
  61         pub fn from_client(client: ElectrumClient, logger: L) -> Result<Self, TxSyncError> {
  62                 let sync_state = Mutex::new(SyncState::new());
  63                 let queue = Mutex::new(FilterQueue::new());
  64
  65                 Ok(Self {
  66                         sync_state,
  67                         queue,
  68                         client,
  69                         logger,
  70                 })
  71         }
  72
  73         /// Synchronizes the given `confirmables` via their [`Confirm`] interface implementations. This
  74         /// method should be called regularly to keep LDK up-to-date with current chain data.
  75         ///
  76         /// For example, instances of [`ChannelManager`] and [`ChainMonitor`] can be informed about the
  77         /// newest on-chain activity related to the items previously registered via the [`Filter`]
  78         /// interface.
  79         ///
  80         /// [`Confirm`]: lightning::chain::Confirm
  81         /// [`ChainMonitor`]: lightning::chain::chainmonitor::ChainMonitor
  82         /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
  83         /// [`Filter`]: lightning::chain::Filter
  84         pub fn sync(&self, confirmables: Vec<&(dyn Confirm + Sync + Send)>) -> Result<(), TxSyncError> {
  85                 // This lock makes sure we're syncing once at a time.
  86                 let mut sync_state = self.sync_state.lock().unwrap();
  87
  88                 log_trace!(self.logger, "Starting transaction sync.");
  89                 let start_time = Instant::now();
  90                 let mut num_confirmed = 0;
  91                 let mut num_unconfirmed = 0;
  92
  93                 // Clear any header notifications we might have gotten to keep the queue count low.
  94                 while let Some(_) = self.client.block_headers_pop()? {}
  95
  96                 let tip_notification = self.client.block_headers_subscribe()?;
  97                 let mut tip_header = tip_notification.header;
  98                 let mut tip_height = tip_notification.height as u32;
  99
 100                 loop {
 101                         let pending_registrations = self.queue.lock().unwrap().process_queues(&mut sync_state);
 102                         let tip_is_new = Some(tip_header.block_hash()) != sync_state.last_sync_hash;
 103
 104                         // We loop until any registered transactions have been processed at least once, or the
 105                         // tip hasn't been updated during the last iteration.
 106                         if !sync_state.pending_sync && !pending_registrations && !tip_is_new {
 107                                 // Nothing to do.
 108                                 break;
 109                         } else {
 110                                 // Update the known tip to the newest one.
 111                                 if tip_is_new {
 112                                         // First check for any unconfirmed transactions and act on it immediately.
 113                                         match self.get_unconfirmed_transactions(&confirmables) {
 114                                                 Ok(unconfirmed_txs) => {
 115                                                         // Double-check the tip hash. If it changed, a reorg happened since
 116                                                         // we started syncing and we need to restart last-minute.
 117                                                         match self.check_update_tip(&mut tip_header, &mut tip_height) {
 118                                                                 Ok(false) => {
 119                                                                         num_unconfirmed += unconfirmed_txs.len();
 120                                                                         sync_state.sync_unconfirmed_transactions(
 121                                                                                 &confirmables,
 122                                                                                 unconfirmed_txs
 123                                                                         );
 124                                                                 }
 125                                                                 Ok(true) => {
 126                                                                         log_debug!(self.logger,
 127                                                                                 "Encountered inconsistency during transaction sync, restarting.");
 128                                                                         sync_state.pending_sync = true;
 129                                                                         continue;
 130                                                                 }
 131                                                                 Err(err) => {
 132                                                                         // (Semi-)permanent failure, retry later.
 133                                                                         log_error!(self.logger,
 134                                                                                 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 135                                                                                 num_confirmed,
 136                                                                                 num_unconfirmed
 137                                                                         );
 138                                                                         sync_state.pending_sync = true;
 139                                                                         return Err(TxSyncError::from(err));
 140                                                                 }
 141                                                         }
 142                                                 },
 143                                                 Err(err) => {
 144                                                         // (Semi-)permanent failure, retry later.
 145                                                         log_error!(self.logger,
 146                                                                 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 147                                                                 num_confirmed,
 148                                                                 num_unconfirmed
 149                                                         );
 150                                                         sync_state.pending_sync = true;
 151                                                         return Err(TxSyncError::from(err));
 152                                                 }
 153                                         }
 154
 155                                         // Update the best block.
 156                                         for c in &confirmables {
 157                                                 c.best_block_updated(&tip_header, tip_height);
 158                                         }
 159                                 }
 160
 161                                 match self.get_confirmed_transactions(&sync_state) {
 162                                         Ok(confirmed_txs) => {
 163                                                 // Double-check the tip hash. If it changed, a reorg happened since
 164                                                 // we started syncing and we need to restart last-minute.
 165                                                 match self.check_update_tip(&mut tip_header, &mut tip_height) {
 166                                                         Ok(false) => {
 167                                                                 num_confirmed += confirmed_txs.len();
 168                                                                 sync_state.sync_confirmed_transactions(
 169                                                                         &confirmables,
 170                                                                         confirmed_txs
 171                                                                 );
 172                                                         }
 173                                                         Ok(true) => {
 174                                                                 log_debug!(self.logger,
 175                                                                         "Encountered inconsistency during transaction sync, restarting.");
 176                                                                 sync_state.pending_sync = true;
 177                                                                 continue;
 178                                                         }
 179                                                         Err(err) => {
 180                                                                 // (Semi-)permanent failure, retry later.
 181                                                                 log_error!(self.logger,
 182                                                                         "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 183                                                                         num_confirmed,
 184                                                                         num_unconfirmed
 185                                                                 );
 186                                                                 sync_state.pending_sync = true;
 187                                                                 return Err(TxSyncError::from(err));
 188                                                         }
 189                                                 }
 190                                         }
 191                                         Err(InternalError::Inconsistency) => {
 192                                                 // Immediately restart syncing when we encounter any inconsistencies.
 193                                                 log_debug!(self.logger,
 194                                                         "Encountered inconsistency during transaction sync, restarting.");
 195                                                 sync_state.pending_sync = true;
 196                                                 continue;
 197                                         }
 198                                         Err(err) => {
 199                                                 // (Semi-)permanent failure, retry later.
 200                                                 log_error!(self.logger,
 201                                                         "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 202                                                         num_confirmed,
 203                                                         num_unconfirmed
 204                                                 );
 205                                                 sync_state.pending_sync = true;
 206                                                 return Err(TxSyncError::from(err));
 207                                         }
 208                                 }
 209                                 sync_state.last_sync_hash = Some(tip_header.block_hash());
 210                                 sync_state.pending_sync = false;
 211                         }
 212                 }
 213                 log_debug!(self.logger,
 214                         "Finished transaction sync at tip {} in {}ms: {} confirmed, {} unconfirmed.",
 215                         tip_header.block_hash(), start_time.elapsed().as_millis(), num_confirmed,
 216                         num_unconfirmed);
 217                 Ok(())
 218         }
 219
 220         fn check_update_tip(&self, cur_tip_header: &mut Header, cur_tip_height: &mut u32)
 221                 -> Result<bool, InternalError>
 222         {
 223                 let check_notification = self.client.block_headers_subscribe()?;
 224                 let check_tip_hash = check_notification.header.block_hash();
 225
 226                 // Restart if either the tip changed or we got some divergent tip
 227                 // change notification since we started. In the latter case we
 228                 // make sure we clear the queue before continuing.
 229                 let mut restart_sync = check_tip_hash != cur_tip_header.block_hash();
 230                 while let Some(queued_notif) = self.client.block_headers_pop()? {
 231                         if queued_notif.header.block_hash() != check_tip_hash {
 232                                 restart_sync = true
 233                         }
 234                 }
 235
 236                 if restart_sync {
 237                         *cur_tip_header = check_notification.header;
 238                         *cur_tip_height = check_notification.height as u32;
 239                         Ok(true)
 240                 } else {
 241                         Ok(false)
 242                 }
 243         }
 244
 245         fn get_confirmed_transactions(
 246                 &self, sync_state: &SyncState,
 247         ) -> Result<Vec<ConfirmedTx>, InternalError> {
 248
 249                 // First, check the confirmation status of registered transactions as well as the
 250                 // status of dependent transactions of registered outputs.
 251                 let mut confirmed_txs = Vec::new();
 252                 let mut watched_script_pubkeys = Vec::with_capacity(
 253                         sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
 254                 let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
 255
 256                 for txid in &sync_state.watched_transactions {
 257                         match self.client.transaction_get(&txid) {
 258                                 Ok(tx) => {
 259                                         watched_txs.push((txid, tx.clone()));
 260                                         if let Some(tx_out) = tx.output.first() {
 261                                                 // We watch an arbitrary output of the transaction of interest in order to
 262                                                 // retrieve the associated script history, before narrowing down our search
 263                                                 // through `filter`ing by `txid` below.
 264                                                 watched_script_pubkeys.push(tx_out.script_pubkey.clone());
 265                                         } else {
 266                                                 debug_assert!(false, "Failed due to retrieving invalid tx data.");
 267                                                 log_error!(self.logger, "Failed due to retrieving invalid tx data.");
 268                                                 return Err(InternalError::Failed);
 269                                         }
 270                                 }
 271                                 Err(electrum_client::Error::Protocol(_)) => {
 272                                         // We couldn't find the tx, do nothing.
 273                                 }
 274                                 Err(e) => {
 275                                         log_error!(self.logger, "Failed to look up transaction {}: {}.", txid, e);
 276                                         return Err(InternalError::Failed);
 277                                 }
 278                         }
 279                 }
 280
 281                 let num_tx_lookups = watched_script_pubkeys.len();
 282                 debug_assert_eq!(num_tx_lookups, watched_txs.len());
 283
 284                 for output in sync_state.watched_outputs.values() {
 285                         watched_script_pubkeys.push(output.script_pubkey.clone());
 286                 }
 287
 288                 let num_output_spend_lookups = watched_script_pubkeys.len() - num_tx_lookups;
 289                 debug_assert_eq!(num_output_spend_lookups, sync_state.watched_outputs.len());
 290
 291                 match self.client.batch_script_get_history(watched_script_pubkeys.iter().map(|s| s.deref()))
 292                 {
 293                         Ok(results) => {
 294                                 let (tx_results, output_results) = results.split_at(num_tx_lookups);
 295                                 debug_assert_eq!(num_output_spend_lookups, output_results.len());
 296
 297                                 for (i, script_history) in tx_results.iter().enumerate() {
 298                                         let (txid, tx) = &watched_txs[i];
 299                                         let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
 300                                         if let Some(history) = filtered_history.next()
 301                                         {
 302                                                 let prob_conf_height = history.height as u32;
 303                                                 let confirmed_tx = self.get_confirmed_tx(tx, prob_conf_height)?;
 304                                                 confirmed_txs.push(confirmed_tx);
 305                                         }
 306                                         debug_assert!(filtered_history.next().is_none());
 307                                 }
 308
 309                                 for (watched_output, script_history) in sync_state.watched_outputs.values()
 310                                         .zip(output_results)
 311                                 {
 312                                         for possible_output_spend in script_history {
 313                                                 if possible_output_spend.height <= 0 {
 314                                                         continue;
 315                                                 }
 316
 317                                                 let txid = possible_output_spend.tx_hash;
 318                                                 match self.client.transaction_get(&txid) {
 319                                                         Ok(tx) => {
 320                                                                 let mut is_spend = false;
 321                                                                 for txin in &tx.input {
 322                                                                         let watched_outpoint = watched_output.outpoint
 323                                                                                 .into_bitcoin_outpoint();
 324                                                                         if txin.previous_output == watched_outpoint {
 325                                                                                 is_spend = true;
 326                                                                                 break;
 327                                                                         }
 328                                                                 }
 329
 330                                                                 if !is_spend {
 331                                                                         continue;
 332                                                                 }
 333
 334                                                                 let prob_conf_height = possible_output_spend.height as u32;
 335                                                                 let confirmed_tx = self.get_confirmed_tx(&tx, prob_conf_height)?;
 336                                                                 confirmed_txs.push(confirmed_tx);
 337                                                         }
 338                                                         Err(e) => {
 339                                                                 log_trace!(self.logger,
 340                                                                         "Inconsistency: Tx {} was unconfirmed during syncing: {}",
 341                                                                         txid, e);
 342                                                                 return Err(InternalError::Inconsistency);
 343                                                         }
 344                                                 }
 345                                         }
 346                                 }
 347                         }
 348                         Err(e) => {
 349                                 log_error!(self.logger, "Failed to look up script histories: {}.", e);
 350                                 return Err(InternalError::Failed);
 351                         }
 352                 }
 353
 354                 // Sort all confirmed transactions first by block height, then by in-block
 355                 // position, and finally feed them to the interface in order.
 356                 confirmed_txs.sort_unstable_by(|tx1, tx2| {
 357                         tx1.block_height.cmp(&tx2.block_height).then_with(|| tx1.pos.cmp(&tx2.pos))
 358                 });
 359
 360                 Ok(confirmed_txs)
 361         }
 362
 363         fn get_unconfirmed_transactions(
 364                 &self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>,
 365         ) -> Result<Vec<Txid>, InternalError> {
 366                 // Query the interface for relevant txids and check whether the relevant blocks are still
 367                 // in the best chain, mark them unconfirmed otherwise
 368                 let relevant_txids = confirmables
 369                         .iter()
 370                         .flat_map(|c| c.get_relevant_txids())
 371                         .collect::<HashSet<(Txid, u32, Option<BlockHash>)>>();
 372
 373                 let mut unconfirmed_txs = Vec::new();
 374
 375                 for (txid, conf_height, block_hash_opt) in relevant_txids {
 376                         if let Some(block_hash) = block_hash_opt {
 377                                 let block_header = self.client.block_header(conf_height as usize)?;
 378                                 if block_header.block_hash() == block_hash {
 379                                         // Skip if the tx is still confirmed in the block in question.
 380                                         continue;
 381                                 }
 382
 383                                 unconfirmed_txs.push(txid);
 384                         } else {
 385                                 log_error!(self.logger,
 386                                         "Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
 387                                 panic!("Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
 388                         }
 389                 }
 390                 Ok(unconfirmed_txs)
 391         }
 392
 393         fn get_confirmed_tx(&self, tx: &Transaction, prob_conf_height: u32)
 394                 -> Result<ConfirmedTx, InternalError>
 395         {
 396                 let txid = tx.txid();
 397                 match self.client.transaction_get_merkle(&txid, prob_conf_height as usize) {
 398                         Ok(merkle_res) => {
 399                                 debug_assert_eq!(prob_conf_height, merkle_res.block_height as u32);
 400                                 match self.client.block_header(prob_conf_height as usize) {
 401                                         Ok(block_header) => {
 402                                                 let pos = merkle_res.pos;
 403                                                 if !self.validate_merkle_proof(&txid,
 404                                                         &block_header.merkle_root, merkle_res)?
 405                                                 {
 406                                                         log_trace!(self.logger,
 407                                                                 "Inconsistency: Block {} was unconfirmed during syncing.",
 408                                                                 block_header.block_hash());
 409                                                         return Err(InternalError::Inconsistency);
 410                                                 }
 411                                                 let confirmed_tx = ConfirmedTx {
 412                                                         tx: tx.clone(),
 413                                                         block_header, block_height: prob_conf_height,
 414                                                         pos,
 415                                                 };
 416                                                 Ok(confirmed_tx)
 417                                         }
 418                                         Err(e) => {
 419                                                 log_error!(self.logger,
 420                                                         "Failed to retrieve block header for height {}: {}.",
 421                                                         prob_conf_height, e);
 422                                                 Err(InternalError::Failed)
 423                                         }
 424                                 }
 425                         }
 426                         Err(e) => {
 427                                 log_trace!(self.logger,
 428                                         "Inconsistency: Tx {} was unconfirmed during syncing: {}",
 429                                         txid, e);
 430                                 Err(InternalError::Inconsistency)
 431                         }
 432                 }
 433         }
 434
 435         /// Returns a reference to the underlying Electrum client.
 436         pub fn client(&self) -> &ElectrumClient {
 437                 &self.client
 438         }
 439
 440         fn validate_merkle_proof(&self, txid: &Txid, merkle_root: &TxMerkleNode,
 441                 merkle_res: GetMerkleRes) -> Result<bool, InternalError>
 442         {
 443                 let mut index = merkle_res.pos;
 444                 let mut cur = txid.to_raw_hash();
 445                 for mut bytes in merkle_res.merkle {
 446                         bytes.reverse();
 447                         // unwrap() safety: `bytes` has len 32 so `from_slice` can never fail.
 448                         let next_hash = Sha256d::from_slice(&bytes).unwrap();
 449                         let (left, right) = if index % 2 == 0 {
 450                                 (cur, next_hash)
 451                         } else {
 452                                 (next_hash, cur)
 453                         };
 454
 455                         let data = [&left[..], &right[..]].concat();
 456                         cur = Sha256d::hash(&data);
 457                         index /= 2;
 458                 }
 459
 460                 Ok(cur == merkle_root.to_raw_hash())
 461         }
 462 }
 463
 464 impl<L: Deref> Filter for ElectrumSyncClient<L>
 465 where
 466         L::Target: Logger,
 467 {
 468         fn register_tx(&self, txid: &Txid, _script_pubkey: &Script) {
 469                 let mut locked_queue = self.queue.lock().unwrap();
 470                 locked_queue.transactions.insert(*txid);
 471         }
 472
 473         fn register_output(&self, output: WatchedOutput) {
 474                 let mut locked_queue = self.queue.lock().unwrap();
 475                 locked_queue.outputs.insert(output.outpoint.into_bitcoin_outpoint(), output);
 476         }
 477 }