_ 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         ///
  62         /// This is not exported to bindings users as the underlying client from BDK is not exported.
  63         pub fn from_client(client: ElectrumClient, logger: L) -> Result<Self, TxSyncError> {
  64                 let sync_state = Mutex::new(SyncState::new());
  65                 let queue = Mutex::new(FilterQueue::new());
  66
  67                 Ok(Self {
  68                         sync_state,
  69                         queue,
  70                         client,
  71                         logger,
  72                 })
  73         }
  74
  75         /// Synchronizes the given `confirmables` via their [`Confirm`] interface implementations. This
  76         /// method should be called regularly to keep LDK up-to-date with current chain data.
  77         ///
  78         /// For example, instances of [`ChannelManager`] and [`ChainMonitor`] can be informed about the
  79         /// newest on-chain activity related to the items previously registered via the [`Filter`]
  80         /// interface.
  81         ///
  82         /// [`Confirm`]: lightning::chain::Confirm
  83         /// [`ChainMonitor`]: lightning::chain::chainmonitor::ChainMonitor
  84         /// [`ChannelManager`]: lightning::ln::channelmanager::ChannelManager
  85         /// [`Filter`]: lightning::chain::Filter
  86         pub fn sync(&self, confirmables: Vec<&(dyn Confirm + Sync + Send)>) -> Result<(), TxSyncError> {
  87                 // This lock makes sure we're syncing once at a time.
  88                 let mut sync_state = self.sync_state.lock().unwrap();
  89
  90                 log_trace!(self.logger, "Starting transaction sync.");
  91                 #[cfg(feature = "time")]
  92                 let start_time = Instant::now();
  93                 let mut num_confirmed = 0;
  94                 let mut num_unconfirmed = 0;
  95
  96                 // Clear any header notifications we might have gotten to keep the queue count low.
  97                 while let Some(_) = self.client.block_headers_pop()? {}
  98
  99                 let tip_notification = self.client.block_headers_subscribe()?;
 100                 let mut tip_header = tip_notification.header;
 101                 let mut tip_height = tip_notification.height as u32;
 102
 103                 loop {
 104                         let pending_registrations = self.queue.lock().unwrap().process_queues(&mut sync_state);
 105                         let tip_is_new = Some(tip_header.block_hash()) != sync_state.last_sync_hash;
 106
 107                         // We loop until any registered transactions have been processed at least once, or the
 108                         // tip hasn't been updated during the last iteration.
 109                         if !sync_state.pending_sync && !pending_registrations && !tip_is_new {
 110                                 // Nothing to do.
 111                                 break;
 112                         } else {
 113                                 // Update the known tip to the newest one.
 114                                 if tip_is_new {
 115                                         // First check for any unconfirmed transactions and act on it immediately.
 116                                         match self.get_unconfirmed_transactions(&confirmables) {
 117                                                 Ok(unconfirmed_txs) => {
 118                                                         // Double-check the tip hash. If it changed, a reorg happened since
 119                                                         // we started syncing and we need to restart last-minute.
 120                                                         match self.check_update_tip(&mut tip_header, &mut tip_height) {
 121                                                                 Ok(false) => {
 122                                                                         num_unconfirmed += unconfirmed_txs.len();
 123                                                                         sync_state.sync_unconfirmed_transactions(
 124                                                                                 &confirmables,
 125                                                                                 unconfirmed_txs
 126                                                                         );
 127                                                                 }
 128                                                                 Ok(true) => {
 129                                                                         log_debug!(self.logger,
 130                                                                                 "Encountered inconsistency during transaction sync, restarting.");
 131                                                                         sync_state.pending_sync = true;
 132                                                                         continue;
 133                                                                 }
 134                                                                 Err(err) => {
 135                                                                         // (Semi-)permanent failure, retry later.
 136                                                                         log_error!(self.logger,
 137                                                                                 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 138                                                                                 num_confirmed,
 139                                                                                 num_unconfirmed
 140                                                                         );
 141                                                                         sync_state.pending_sync = true;
 142                                                                         return Err(TxSyncError::from(err));
 143                                                                 }
 144                                                         }
 145                                                 },
 146                                                 Err(err) => {
 147                                                         // (Semi-)permanent failure, retry later.
 148                                                         log_error!(self.logger,
 149                                                                 "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 150                                                                 num_confirmed,
 151                                                                 num_unconfirmed
 152                                                         );
 153                                                         sync_state.pending_sync = true;
 154                                                         return Err(TxSyncError::from(err));
 155                                                 }
 156                                         }
 157
 158                                         // Update the best block.
 159                                         for c in &confirmables {
 160                                                 c.best_block_updated(&tip_header, tip_height);
 161                                         }
 162
 163                                         // Prune any sufficiently confirmed output spends
 164                                         sync_state.prune_output_spends(tip_height);
 165                                 }
 166
 167                                 match self.get_confirmed_transactions(&sync_state) {
 168                                         Ok(confirmed_txs) => {
 169                                                 // Double-check the tip hash. If it changed, a reorg happened since
 170                                                 // we started syncing and we need to restart last-minute.
 171                                                 match self.check_update_tip(&mut tip_header, &mut tip_height) {
 172                                                         Ok(false) => {
 173                                                                 num_confirmed += confirmed_txs.len();
 174                                                                 sync_state.sync_confirmed_transactions(
 175                                                                         &confirmables,
 176                                                                         confirmed_txs
 177                                                                 );
 178                                                         }
 179                                                         Ok(true) => {
 180                                                                 log_debug!(self.logger,
 181                                                                         "Encountered inconsistency during transaction sync, restarting.");
 182                                                                 sync_state.pending_sync = true;
 183                                                                 continue;
 184                                                         }
 185                                                         Err(err) => {
 186                                                                 // (Semi-)permanent failure, retry later.
 187                                                                 log_error!(self.logger,
 188                                                                         "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 189                                                                         num_confirmed,
 190                                                                         num_unconfirmed
 191                                                                 );
 192                                                                 sync_state.pending_sync = true;
 193                                                                 return Err(TxSyncError::from(err));
 194                                                         }
 195                                                 }
 196                                         }
 197                                         Err(InternalError::Inconsistency) => {
 198                                                 // Immediately restart syncing when we encounter any inconsistencies.
 199                                                 log_debug!(self.logger,
 200                                                         "Encountered inconsistency during transaction sync, restarting.");
 201                                                 sync_state.pending_sync = true;
 202                                                 continue;
 203                                         }
 204                                         Err(err) => {
 205                                                 // (Semi-)permanent failure, retry later.
 206                                                 log_error!(self.logger,
 207                                                         "Failed during transaction sync, aborting. Synced so far: {} confirmed, {} unconfirmed.",
 208                                                         num_confirmed,
 209                                                         num_unconfirmed
 210                                                 );
 211                                                 sync_state.pending_sync = true;
 212                                                 return Err(TxSyncError::from(err));
 213                                         }
 214                                 }
 215                                 sync_state.last_sync_hash = Some(tip_header.block_hash());
 216                                 sync_state.pending_sync = false;
 217                         }
 218                 }
 219                 #[cfg(feature = "time")]
 220                 log_debug!(self.logger,
 221                         "Finished transaction sync at tip {} in {}ms: {} confirmed, {} unconfirmed.",
 222                         tip_header.block_hash(), start_time.elapsed().as_millis(), num_confirmed,
 223                         num_unconfirmed);
 224                 #[cfg(not(feature = "time"))]
 225                 log_debug!(self.logger,
 226                         "Finished transaction sync at tip {}: {} confirmed, {} unconfirmed.",
 227                         tip_header.block_hash(), num_confirmed, num_unconfirmed);
 228                 Ok(())
 229         }
 230
 231         fn check_update_tip(&self, cur_tip_header: &mut Header, cur_tip_height: &mut u32)
 232                 -> Result<bool, InternalError>
 233         {
 234                 let check_notification = self.client.block_headers_subscribe()?;
 235                 let check_tip_hash = check_notification.header.block_hash();
 236
 237                 // Restart if either the tip changed or we got some divergent tip
 238                 // change notification since we started. In the latter case we
 239                 // make sure we clear the queue before continuing.
 240                 let mut restart_sync = check_tip_hash != cur_tip_header.block_hash();
 241                 while let Some(queued_notif) = self.client.block_headers_pop()? {
 242                         if queued_notif.header.block_hash() != check_tip_hash {
 243                                 restart_sync = true
 244                         }
 245                 }
 246
 247                 if restart_sync {
 248                         *cur_tip_header = check_notification.header;
 249                         *cur_tip_height = check_notification.height as u32;
 250                         Ok(true)
 251                 } else {
 252                         Ok(false)
 253                 }
 254         }
 255
 256         fn get_confirmed_transactions(
 257                 &self, sync_state: &SyncState,
 258         ) -> Result<Vec<ConfirmedTx>, InternalError> {
 259
 260                 // First, check the confirmation status of registered transactions as well as the
 261                 // status of dependent transactions of registered outputs.
 262                 let mut confirmed_txs: Vec<ConfirmedTx> = Vec::new();
 263                 let mut watched_script_pubkeys = Vec::with_capacity(
 264                         sync_state.watched_transactions.len() + sync_state.watched_outputs.len());
 265                 let mut watched_txs = Vec::with_capacity(sync_state.watched_transactions.len());
 266
 267                 for txid in &sync_state.watched_transactions {
 268                         match self.client.transaction_get(&txid) {
 269                                 Ok(tx) => {
 270                                         watched_txs.push((txid, tx.clone()));
 271                                         if let Some(tx_out) = tx.output.first() {
 272                                                 // We watch an arbitrary output of the transaction of interest in order to
 273                                                 // retrieve the associated script history, before narrowing down our search
 274                                                 // through `filter`ing by `txid` below.
 275                                                 watched_script_pubkeys.push(tx_out.script_pubkey.clone());
 276                                         } else {
 277                                                 debug_assert!(false, "Failed due to retrieving invalid tx data.");
 278                                                 log_error!(self.logger, "Failed due to retrieving invalid tx data.");
 279                                                 return Err(InternalError::Failed);
 280                                         }
 281                                 }
 282                                 Err(electrum_client::Error::Protocol(_)) => {
 283                                         // We couldn't find the tx, do nothing.
 284                                 }
 285                                 Err(e) => {
 286                                         log_error!(self.logger, "Failed to look up transaction {}: {}.", txid, e);
 287                                         return Err(InternalError::Failed);
 288                                 }
 289                         }
 290                 }
 291
 292                 let num_tx_lookups = watched_script_pubkeys.len();
 293                 debug_assert_eq!(num_tx_lookups, watched_txs.len());
 294
 295                 for output in sync_state.watched_outputs.values() {
 296                         watched_script_pubkeys.push(output.script_pubkey.clone());
 297                 }
 298
 299                 let num_output_spend_lookups = watched_script_pubkeys.len() - num_tx_lookups;
 300                 debug_assert_eq!(num_output_spend_lookups, sync_state.watched_outputs.len());
 301
 302                 match self.client.batch_script_get_history(watched_script_pubkeys.iter().map(|s| s.deref()))
 303                 {
 304                         Ok(results) => {
 305                                 let (tx_results, output_results) = results.split_at(num_tx_lookups);
 306                                 debug_assert_eq!(num_output_spend_lookups, output_results.len());
 307
 308                                 for (i, script_history) in tx_results.iter().enumerate() {
 309                                         let (txid, tx) = &watched_txs[i];
 310                                         if confirmed_txs.iter().any(|ctx| ctx.txid == **txid) {
 311                                                 continue;
 312                                         }
 313                                         let mut filtered_history = script_history.iter().filter(|h| h.tx_hash == **txid);
 314                                         if let Some(history) = filtered_history.next()
 315                                         {
 316                                                 let prob_conf_height = history.height as u32;
 317                                                 let confirmed_tx = self.get_confirmed_tx(tx, prob_conf_height)?;
 318                                                 confirmed_txs.push(confirmed_tx);
 319                                         }
 320                                         debug_assert!(filtered_history.next().is_none());
 321                                 }
 322
 323                                 for (watched_output, script_history) in sync_state.watched_outputs.values()
 324                                         .zip(output_results)
 325                                 {
 326                                         for possible_output_spend in script_history {
 327                                                 if possible_output_spend.height <= 0 {
 328                                                         continue;
 329                                                 }
 330
 331                                                 let txid = possible_output_spend.tx_hash;
 332                                                 if confirmed_txs.iter().any(|ctx| ctx.txid == txid) {
 333                                                         continue;
 334                                                 }
 335
 336                                                 match self.client.transaction_get(&txid) {
 337                                                         Ok(tx) => {
 338                                                                 let mut is_spend = false;
 339                                                                 for txin in &tx.input {
 340                                                                         let watched_outpoint = watched_output.outpoint
 341                                                                                 .into_bitcoin_outpoint();
 342                                                                         if txin.previous_output == watched_outpoint {
 343                                                                                 is_spend = true;
 344                                                                                 break;
 345                                                                         }
 346                                                                 }
 347
 348                                                                 if !is_spend {
 349                                                                         continue;
 350                                                                 }
 351
 352                                                                 let prob_conf_height = possible_output_spend.height as u32;
 353                                                                 let confirmed_tx = self.get_confirmed_tx(&tx, prob_conf_height)?;
 354                                                                 confirmed_txs.push(confirmed_tx);
 355                                                         }
 356                                                         Err(e) => {
 357                                                                 log_trace!(self.logger,
 358                                                                         "Inconsistency: Tx {} was unconfirmed during syncing: {}",
 359                                                                         txid, e);
 360                                                                 return Err(InternalError::Inconsistency);
 361                                                         }
 362                                                 }
 363                                         }
 364                                 }
 365                         }
 366                         Err(e) => {
 367                                 log_error!(self.logger, "Failed to look up script histories: {}.", e);
 368                                 return Err(InternalError::Failed);
 369                         }
 370                 }
 371
 372                 // Sort all confirmed transactions first by block height, then by in-block
 373                 // position, and finally feed them to the interface in order.
 374                 confirmed_txs.sort_unstable_by(|tx1, tx2| {
 375                         tx1.block_height.cmp(&tx2.block_height).then_with(|| tx1.pos.cmp(&tx2.pos))
 376                 });
 377
 378                 Ok(confirmed_txs)
 379         }
 380
 381         fn get_unconfirmed_transactions(
 382                 &self, confirmables: &Vec<&(dyn Confirm + Sync + Send)>,
 383         ) -> Result<Vec<Txid>, InternalError> {
 384                 // Query the interface for relevant txids and check whether the relevant blocks are still
 385                 // in the best chain, mark them unconfirmed otherwise
 386                 let relevant_txids = confirmables
 387                         .iter()
 388                         .flat_map(|c| c.get_relevant_txids())
 389                         .collect::<HashSet<(Txid, u32, Option<BlockHash>)>>();
 390
 391                 let mut unconfirmed_txs = Vec::new();
 392
 393                 for (txid, conf_height, block_hash_opt) in relevant_txids {
 394                         if let Some(block_hash) = block_hash_opt {
 395                                 let block_header = self.client.block_header(conf_height as usize)?;
 396                                 if block_header.block_hash() == block_hash {
 397                                         // Skip if the tx is still confirmed in the block in question.
 398                                         continue;
 399                                 }
 400
 401                                 unconfirmed_txs.push(txid);
 402                         } else {
 403                                 log_error!(self.logger,
 404                                         "Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
 405                                 panic!("Untracked confirmation of funding transaction. Please ensure none of your channels had been created with LDK prior to version 0.0.113!");
 406                         }
 407                 }
 408                 Ok(unconfirmed_txs)
 409         }
 410
 411         fn get_confirmed_tx(&self, tx: &Transaction, prob_conf_height: u32)
 412                 -> Result<ConfirmedTx, InternalError>
 413         {
 414                 let txid = tx.txid();
 415                 match self.client.transaction_get_merkle(&txid, prob_conf_height as usize) {
 416                         Ok(merkle_res) => {
 417                                 debug_assert_eq!(prob_conf_height, merkle_res.block_height as u32);
 418                                 match self.client.block_header(prob_conf_height as usize) {
 419                                         Ok(block_header) => {
 420                                                 let pos = merkle_res.pos;
 421                                                 if !self.validate_merkle_proof(&txid,
 422                                                         &block_header.merkle_root, merkle_res)?
 423                                                 {
 424                                                         log_trace!(self.logger,
 425                                                                 "Inconsistency: Block {} was unconfirmed during syncing.",
 426                                                                 block_header.block_hash());
 427                                                         return Err(InternalError::Inconsistency);
 428                                                 }
 429                                                 let confirmed_tx = ConfirmedTx {
 430                                                         tx: tx.clone(),
 431                                                         txid,
 432                                                         block_header, block_height: prob_conf_height,
 433                                                         pos,
 434                                                 };
 435                                                 Ok(confirmed_tx)
 436                                         }
 437                                         Err(e) => {
 438                                                 log_error!(self.logger,
 439                                                         "Failed to retrieve block header for height {}: {}.",
 440                                                         prob_conf_height, e);
 441                                                 Err(InternalError::Failed)
 442                                         }
 443                                 }
 444                         }
 445                         Err(e) => {
 446                                 log_trace!(self.logger,
 447                                         "Inconsistency: Tx {} was unconfirmed during syncing: {}",
 448                                         txid, e);
 449                                 Err(InternalError::Inconsistency)
 450                         }
 451                 }
 452         }
 453
 454         /// Returns a reference to the underlying Electrum client.
 455         ///
 456         /// This is not exported to bindings users as the underlying client from BDK is not exported.
 457         pub fn client(&self) -> &ElectrumClient {
 458                 &self.client
 459         }
 460
 461         fn validate_merkle_proof(&self, txid: &Txid, merkle_root: &TxMerkleNode,
 462                 merkle_res: GetMerkleRes) -> Result<bool, InternalError>
 463         {
 464                 let mut index = merkle_res.pos;
 465                 let mut cur = txid.to_raw_hash();
 466                 for mut bytes in merkle_res.merkle {
 467                         bytes.reverse();
 468                         // unwrap() safety: `bytes` has len 32 so `from_slice` can never fail.
 469                         let next_hash = Sha256d::from_slice(&bytes).unwrap();
 470                         let (left, right) = if index % 2 == 0 {
 471                                 (cur, next_hash)
 472                         } else {
 473                                 (next_hash, cur)
 474                         };
 475
 476                         let data = [&left[..], &right[..]].concat();
 477                         cur = Sha256d::hash(&data);
 478                         index /= 2;
 479                 }
 480
 481                 Ok(cur == merkle_root.to_raw_hash())
 482         }
 483 }
 484
 485 impl<L: Deref> Filter for ElectrumSyncClient<L>
 486 where
 487         L::Target: Logger,
 488 {
 489         fn register_tx(&self, txid: &Txid, _script_pubkey: &Script) {
 490                 let mut locked_queue = self.queue.lock().unwrap();
 491                 locked_queue.transactions.insert(*txid);
 492         }
 493
 494         fn register_output(&self, output: WatchedOutput) {
 495                 let mut locked_queue = self.queue.lock().unwrap();
 496                 locked_queue.outputs.insert(output.outpoint.into_bitcoin_outpoint(), output);
 497         }
 498 }