_ Git - rust-lightning/blob - lightning/src/routing/utxo.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! This module contains traits for LDK to access UTXOs to check gossip data is correct.
  11 //!
  12 //! When lightning nodes gossip channel information, they resist DoS attacks by checking that each
  13 //! channel matches a UTXO on-chain, requiring at least some marginal on-chain transacting in
  14 //! order to announce a channel. This module handles that checking.
  15
  16 use bitcoin::{BlockHash, TxOut};
  17 use bitcoin::hashes::hex::ToHex;
  18
  19 use crate::ln::chan_utils::make_funding_redeemscript_from_slices;
  20 use crate::ln::msgs::{self, LightningError, ErrorAction};
  21 use crate::routing::gossip::{NetworkGraph, NodeId};
  22 use crate::util::logger::{Level, Logger};
  23 use crate::util::ser::Writeable;
  24
  25 use crate::prelude::*;
  26
  27 use alloc::sync::{Arc, Weak};
  28 use crate::sync::Mutex;
  29 use core::ops::Deref;
  30
  31 /// An error when accessing the chain via [`UtxoLookup`].
  32 #[derive(Clone, Debug)]
  33 pub enum UtxoLookupError {
  34         /// The requested chain is unknown.
  35         UnknownChain,
  36
  37         /// The requested transaction doesn't exist or hasn't confirmed.
  38         UnknownTx,
  39 }
  40
  41 /// The result of a [`UtxoLookup::get_utxo`] call. A call may resolve either synchronously,
  42 /// returning the `Sync` variant, or asynchronously, returning an [`UtxoFuture`] in the `Async`
  43 /// variant.
  44 pub enum UtxoResult {
  45         /// A result which was resolved synchronously. It either includes a [`TxOut`] for the output
  46         /// requested or a [`UtxoLookupError`].
  47         Sync(Result<TxOut, UtxoLookupError>),
  48         /// A result which will be resolved asynchronously. It includes a [`UtxoFuture`], a `clone` of
  49         /// which you must keep locally and call [`UtxoFuture::resolve`] on once the lookup completes.
  50         ///
  51         /// Note that in order to avoid runaway memory usage, the number of parallel checks is limited,
  52         /// but only fairly loosely. Because a pending checks block all message processing, leaving
  53         /// checks pending for an extended time may cause DoS of other functions. It is recommended you
  54         /// keep a tight timeout on lookups, on the order of a few seconds.
  55         Async(UtxoFuture),
  56 }
  57
  58 /// The `UtxoLookup` trait defines behavior for accessing on-chain UTXOs.
  59 pub trait UtxoLookup {
  60         /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
  61         /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
  62         /// is unknown.
  63         ///
  64         /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
  65         fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> UtxoResult;
  66 }
  67
  68 enum ChannelAnnouncement {
  69         Full(msgs::ChannelAnnouncement),
  70         Unsigned(msgs::UnsignedChannelAnnouncement),
  71 }
  72 impl ChannelAnnouncement {
  73         fn node_id_1(&self) -> &NodeId {
  74                 match self {
  75                         ChannelAnnouncement::Full(msg) => &msg.contents.node_id_1,
  76                         ChannelAnnouncement::Unsigned(msg) => &msg.node_id_1,
  77                 }
  78         }
  79 }
  80
  81 enum NodeAnnouncement {
  82         Full(msgs::NodeAnnouncement),
  83         Unsigned(msgs::UnsignedNodeAnnouncement),
  84 }
  85 impl NodeAnnouncement {
  86         fn timestamp(&self) -> u32 {
  87                 match self {
  88                         NodeAnnouncement::Full(msg) => msg.contents.timestamp,
  89                         NodeAnnouncement::Unsigned(msg) => msg.timestamp,
  90                 }
  91         }
  92 }
  93
  94 enum ChannelUpdate {
  95         Full(msgs::ChannelUpdate),
  96         Unsigned(msgs::UnsignedChannelUpdate),
  97 }
  98 impl ChannelUpdate {
  99         fn timestamp(&self) -> u32 {
 100                 match self {
 101                         ChannelUpdate::Full(msg) => msg.contents.timestamp,
 102                         ChannelUpdate::Unsigned(msg) => msg.timestamp,
 103                 }
 104         }
 105 }
 106
 107 struct UtxoMessages {
 108         complete: Option<Result<TxOut, UtxoLookupError>>,
 109         channel_announce: Option<ChannelAnnouncement>,
 110         latest_node_announce_a: Option<NodeAnnouncement>,
 111         latest_node_announce_b: Option<NodeAnnouncement>,
 112         latest_channel_update_a: Option<ChannelUpdate>,
 113         latest_channel_update_b: Option<ChannelUpdate>,
 114 }
 115
 116 /// Represents a future resolution of a [`UtxoLookup::get_utxo`] query resolving async.
 117 ///
 118 /// See [`UtxoResult::Async`] and [`UtxoFuture::resolve`] for more info.
 119 #[derive(Clone)]
 120 pub struct UtxoFuture {
 121         state: Arc<Mutex<UtxoMessages>>,
 122 }
 123
 124 /// A trivial implementation of [`UtxoLookup`] which is used to call back into the network graph
 125 /// once we have a concrete resolution of a request.
 126 struct UtxoResolver(Result<TxOut, UtxoLookupError>);
 127 impl UtxoLookup for UtxoResolver {
 128         fn get_utxo(&self, _genesis_hash: &BlockHash, _short_channel_id: u64) -> UtxoResult {
 129                 UtxoResult::Sync(self.0.clone())
 130         }
 131 }
 132
 133 impl UtxoFuture {
 134         /// Builds a new future for later resolution.
 135         pub fn new() -> Self {
 136                 Self { state: Arc::new(Mutex::new(UtxoMessages {
 137                         complete: None,
 138                         channel_announce: None,
 139                         latest_node_announce_a: None,
 140                         latest_node_announce_b: None,
 141                         latest_channel_update_a: None,
 142                         latest_channel_update_b: None,
 143                 }))}
 144         }
 145
 146         /// Resolves this future against the given `graph` and with the given `result`.
 147         pub fn resolve<L: Deref>(&self, graph: &NetworkGraph<L>, result: Result<TxOut, UtxoLookupError>)
 148         where L::Target: Logger {
 149                 let (announcement, node_a, node_b, update_a, update_b) = {
 150                         let mut pending_checks = graph.pending_checks.internal.lock().unwrap();
 151                         let mut async_messages = self.state.lock().unwrap();
 152
 153                         if async_messages.channel_announce.is_none() {
 154                                 // We raced returning to `check_channel_announcement` which hasn't updated
 155                                 // `channel_announce` yet. That's okay, we can set the `complete` field which it will
 156                                 // check once it gets control again.
 157                                 async_messages.complete = Some(result);
 158                                 return;
 159                         }
 160
 161                         let announcement_msg = match async_messages.channel_announce.as_ref().unwrap() {
 162                                 ChannelAnnouncement::Full(signed_msg) => &signed_msg.contents,
 163                                 ChannelAnnouncement::Unsigned(msg) => &msg,
 164                         };
 165
 166                         pending_checks.lookup_completed(announcement_msg, &Arc::downgrade(&self.state));
 167
 168                         (async_messages.channel_announce.take().unwrap(),
 169                                 async_messages.latest_node_announce_a.take(),
 170                                 async_messages.latest_node_announce_b.take(),
 171                                 async_messages.latest_channel_update_a.take(),
 172                                 async_messages.latest_channel_update_b.take())
 173                 };
 174
 175                 // Now that we've updated our internal state, pass the pending messages back through the
 176                 // network graph with a different `UtxoLookup` which will resolve immediately.
 177                 // Note that we ignore errors as we don't disconnect peers anyway, so there's nothing to do
 178                 // with them.
 179                 let resolver = UtxoResolver(result);
 180                 match announcement {
 181                         ChannelAnnouncement::Full(signed_msg) => {
 182                                 let _ = graph.update_channel_from_announcement(&signed_msg, &Some(&resolver));
 183                         },
 184                         ChannelAnnouncement::Unsigned(msg) => {
 185                                 let _ = graph.update_channel_from_unsigned_announcement(&msg, &Some(&resolver));
 186                         },
 187                 }
 188
 189                 for announce in core::iter::once(node_a).chain(core::iter::once(node_b)) {
 190                         match announce {
 191                                 Some(NodeAnnouncement::Full(signed_msg)) => {
 192                                         let _ = graph.update_node_from_announcement(&signed_msg);
 193                                 },
 194                                 Some(NodeAnnouncement::Unsigned(msg)) => {
 195                                         let _ = graph.update_node_from_unsigned_announcement(&msg);
 196                                 },
 197                                 None => {},
 198                         }
 199                 }
 200
 201                 for update in core::iter::once(update_a).chain(core::iter::once(update_b)) {
 202                         match update {
 203                                 Some(ChannelUpdate::Full(signed_msg)) => {
 204                                         let _ = graph.update_channel(&signed_msg);
 205                                 },
 206                                 Some(ChannelUpdate::Unsigned(msg)) => {
 207                                         let _ = graph.update_channel_unsigned(&msg);
 208                                 },
 209                                 None => {},
 210                         }
 211                 }
 212         }
 213 }
 214
 215 struct PendingChecksContext {
 216         channels: HashMap<u64, Weak<Mutex<UtxoMessages>>>,
 217         nodes: HashMap<NodeId, Vec<Weak<Mutex<UtxoMessages>>>>,
 218 }
 219
 220 impl PendingChecksContext {
 221         fn lookup_completed(&mut self,
 222                 msg: &msgs::UnsignedChannelAnnouncement, completed_state: &Weak<Mutex<UtxoMessages>>
 223         ) {
 224                 if let hash_map::Entry::Occupied(e) = self.channels.entry(msg.short_channel_id) {
 225                         if Weak::ptr_eq(e.get(), &completed_state) {
 226                                 e.remove();
 227                         }
 228                 }
 229
 230                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_1) {
 231                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 232                         if e.get().is_empty() { e.remove(); }
 233                 }
 234                 if let hash_map::Entry::Occupied(mut e) = self.nodes.entry(msg.node_id_2) {
 235                         e.get_mut().retain(|elem| !Weak::ptr_eq(&elem, &completed_state));
 236                         if e.get().is_empty() { e.remove(); }
 237                 }
 238         }
 239 }
 240
 241 /// A set of messages which are pending UTXO lookups for processing.
 242 pub(super) struct PendingChecks {
 243         internal: Mutex<PendingChecksContext>,
 244 }
 245
 246 impl PendingChecks {
 247         pub(super) fn new() -> Self {
 248                 PendingChecks { internal: Mutex::new(PendingChecksContext {
 249                         channels: HashMap::new(), nodes: HashMap::new(),
 250                 }) }
 251         }
 252
 253         /// Checks if there is a pending `channel_update` UTXO validation for the given channel,
 254         /// and, if so, stores the channel message for handling later and returns an `Err`.
 255         pub(super) fn check_hold_pending_channel_update(
 256                 &self, msg: &msgs::UnsignedChannelUpdate, full_msg: Option<&msgs::ChannelUpdate>
 257         ) -> Result<(), LightningError> {
 258                 let mut pending_checks = self.internal.lock().unwrap();
 259                 if let hash_map::Entry::Occupied(e) = pending_checks.channels.entry(msg.short_channel_id) {
 260                         let is_from_a = (msg.flags & 1) == 1;
 261                         match Weak::upgrade(e.get()) {
 262                                 Some(msgs_ref) => {
 263                                         let mut messages = msgs_ref.lock().unwrap();
 264                                         let latest_update = if is_from_a {
 265                                                         &mut messages.latest_channel_update_a
 266                                                 } else {
 267                                                         &mut messages.latest_channel_update_b
 268                                                 };
 269                                         if latest_update.is_none() || latest_update.as_ref().unwrap().timestamp() < msg.timestamp {
 270                                                 // If the messages we got has a higher timestamp, just blindly assume the
 271                                                 // signatures on the new message are correct and drop the old message. This
 272                                                 // may cause us to end up dropping valid `channel_update`s if a peer is
 273                                                 // malicious, but we should get the correct ones when the node updates them.
 274                                                 *latest_update = Some(
 275                                                         if let Some(msg) = full_msg { ChannelUpdate::Full(msg.clone()) }
 276                                                         else { ChannelUpdate::Unsigned(msg.clone()) });
 277                                         }
 278                                         return Err(LightningError {
 279                                                 err: "Awaiting channel_announcement validation to accept channel_update".to_owned(),
 280                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 281                                         });
 282                                 },
 283                                 None => { e.remove(); },
 284                         }
 285                 }
 286                 Ok(())
 287         }
 288
 289         /// Checks if there is a pending `node_announcement` UTXO validation for a channel with the
 290         /// given node and, if so, stores the channel message for handling later and returns an `Err`.
 291         pub(super) fn check_hold_pending_node_announcement(
 292                 &self, msg: &msgs::UnsignedNodeAnnouncement, full_msg: Option<&msgs::NodeAnnouncement>
 293         ) -> Result<(), LightningError> {
 294                 let mut pending_checks = self.internal.lock().unwrap();
 295                 if let hash_map::Entry::Occupied(mut e) = pending_checks.nodes.entry(msg.node_id) {
 296                         let mut found_at_least_one_chan = false;
 297                         e.get_mut().retain(|node_msgs| {
 298                                 match Weak::upgrade(&node_msgs) {
 299                                         Some(chan_mtx) => {
 300                                                 let mut chan_msgs = chan_mtx.lock().unwrap();
 301                                                 if let Some(chan_announce) = &chan_msgs.channel_announce {
 302                                                         let latest_announce =
 303                                                                 if *chan_announce.node_id_1() == msg.node_id {
 304                                                                         &mut chan_msgs.latest_node_announce_a
 305                                                                 } else {
 306                                                                         &mut chan_msgs.latest_node_announce_b
 307                                                                 };
 308                                                         if latest_announce.is_none() ||
 309                                                                 latest_announce.as_ref().unwrap().timestamp() < msg.timestamp
 310                                                         {
 311                                                                 // If the messages we got has a higher timestamp, just blindly
 312                                                                 // assume the signatures on the new message are correct and drop
 313                                                                 // the old message. This may cause us to end up dropping valid
 314                                                                 // `node_announcement`s if a peer is malicious, but we should get
 315                                                                 // the correct ones when the node updates them.
 316                                                                 *latest_announce = Some(
 317                                                                         if let Some(msg) = full_msg { NodeAnnouncement::Full(msg.clone()) }
 318                                                                         else { NodeAnnouncement::Unsigned(msg.clone()) });
 319                                                         }
 320                                                         found_at_least_one_chan = true;
 321                                                         true
 322                                                 } else {
 323                                                         debug_assert!(false, "channel_announce is set before struct is added to node map");
 324                                                         false
 325                                                 }
 326                                         },
 327                                         None => false,
 328                                 }
 329                         });
 330                         if e.get().is_empty() { e.remove(); }
 331                         if found_at_least_one_chan {
 332                                 return Err(LightningError {
 333                                         err: "Awaiting channel_announcement validation to accept node_announcement".to_owned(),
 334                                         action: ErrorAction::IgnoreAndLog(Level::Gossip),
 335                                 });
 336                         }
 337                 }
 338                 Ok(())
 339         }
 340
 341         fn check_replace_previous_entry(msg: &msgs::UnsignedChannelAnnouncement,
 342                 full_msg: Option<&msgs::ChannelAnnouncement>, replacement: Option<Weak<Mutex<UtxoMessages>>>,
 343                 pending_channels: &mut HashMap<u64, Weak<Mutex<UtxoMessages>>>
 344         ) -> Result<(), msgs::LightningError> {
 345                 match pending_channels.entry(msg.short_channel_id) {
 346                         hash_map::Entry::Occupied(mut e) => {
 347                                 // There's already a pending lookup for the given SCID. Check if the messages
 348                                 // are the same and, if so, return immediately (don't bother spawning another
 349                                 // lookup if we haven't gotten that far yet).
 350                                 match Weak::upgrade(&e.get()) {
 351                                         Some(pending_msgs) => {
 352                                                 let pending_matches = match &pending_msgs.lock().unwrap().channel_announce {
 353                                                         Some(ChannelAnnouncement::Full(pending_msg)) => Some(pending_msg) == full_msg,
 354                                                         Some(ChannelAnnouncement::Unsigned(pending_msg)) => pending_msg == msg,
 355                                                         None => {
 356                                                                 // This shouldn't actually be reachable. We set the
 357                                                                 // `channel_announce` field under the same lock as setting the
 358                                                                 // channel map entry. Still, we can just treat it as
 359                                                                 // non-matching and let the new request fly.
 360                                                                 debug_assert!(false);
 361                                                                 false
 362                                                         },
 363                                                 };
 364                                                 if pending_matches {
 365                                                         return Err(LightningError {
 366                                                                 err: "Channel announcement is already being checked".to_owned(),
 367                                                                 action: ErrorAction::IgnoreDuplicateGossip,
 368                                                         });
 369                                                 } else {
 370                                                         // The earlier lookup is a different message. If we have another
 371                                                         // request in-flight now replace the original.
 372                                                         // Note that in the replace case whether to replace is somewhat
 373                                                         // arbitrary - both results will be handled, we're just updating the
 374                                                         // value that will be compared to future lookups with the same SCID.
 375                                                         if let Some(item) = replacement {
 376                                                                 *e.get_mut() = item;
 377                                                         }
 378                                                 }
 379                                         },
 380                                         None => {
 381                                                 // The earlier lookup already resolved. We can't be sure its the same
 382                                                 // so just remove/replace it and move on.
 383                                                 if let Some(item) = replacement {
 384                                                         *e.get_mut() = item;
 385                                                 } else { e.remove(); }
 386                                         },
 387                                 }
 388                         },
 389                         hash_map::Entry::Vacant(v) => {
 390                                 if let Some(item) = replacement { v.insert(item); }
 391                         },
 392                 }
 393                 Ok(())
 394         }
 395
 396         pub(super) fn check_channel_announcement<U: Deref>(&self,
 397                 utxo_lookup: &Option<U>, msg: &msgs::UnsignedChannelAnnouncement,
 398                 full_msg: Option<&msgs::ChannelAnnouncement>
 399         ) -> Result<Option<u64>, msgs::LightningError> where U::Target: UtxoLookup {
 400                 let handle_result = |res| {
 401                         match res {
 402                                 Ok(TxOut { value, script_pubkey }) => {
 403                                         let expected_script =
 404                                                 make_funding_redeemscript_from_slices(msg.bitcoin_key_1.as_slice(), msg.bitcoin_key_2.as_slice()).to_v0_p2wsh();
 405                                         if script_pubkey != expected_script {
 406                                                 return Err(LightningError{
 407                                                         err: format!("Channel announcement key ({}) didn't match on-chain script ({})",
 408                                                                 expected_script.to_hex(), script_pubkey.to_hex()),
 409                                                         action: ErrorAction::IgnoreError
 410                                                 });
 411                                         }
 412                                         Ok(Some(value))
 413                                 },
 414                                 Err(UtxoLookupError::UnknownChain) => {
 415                                         Err(LightningError {
 416                                                 err: format!("Channel announced on an unknown chain ({})",
 417                                                         msg.chain_hash.encode().to_hex()),
 418                                                 action: ErrorAction::IgnoreError
 419                                         })
 420                                 },
 421                                 Err(UtxoLookupError::UnknownTx) => {
 422                                         Err(LightningError {
 423                                                 err: "Channel announced without corresponding UTXO entry".to_owned(),
 424                                                 action: ErrorAction::IgnoreError
 425                                         })
 426                                 },
 427                         }
 428                 };
 429
 430                 Self::check_replace_previous_entry(msg, full_msg, None,
 431                         &mut self.internal.lock().unwrap().channels)?;
 432
 433                 match utxo_lookup {
 434                         &None => {
 435                                 // Tentatively accept, potentially exposing us to DoS attacks
 436                                 Ok(None)
 437                         },
 438                         &Some(ref utxo_lookup) => {
 439                                 match utxo_lookup.get_utxo(&msg.chain_hash, msg.short_channel_id) {
 440                                         UtxoResult::Sync(res) => handle_result(res),
 441                                         UtxoResult::Async(future) => {
 442                                                 let mut pending_checks = self.internal.lock().unwrap();
 443                                                 let mut async_messages = future.state.lock().unwrap();
 444                                                 if let Some(res) = async_messages.complete.take() {
 445                                                         // In the unlikely event the future resolved before we managed to get it,
 446                                                         // handle the result in-line.
 447                                                         handle_result(res)
 448                                                 } else {
 449                                                         Self::check_replace_previous_entry(msg, full_msg,
 450                                                                 Some(Arc::downgrade(&future.state)), &mut pending_checks.channels)?;
 451                                                         async_messages.channel_announce = Some(
 452                                                                 if let Some(msg) = full_msg { ChannelAnnouncement::Full(msg.clone()) }
 453                                                                 else { ChannelAnnouncement::Unsigned(msg.clone()) });
 454                                                         pending_checks.nodes.entry(msg.node_id_1)
 455                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 456                                                         pending_checks.nodes.entry(msg.node_id_2)
 457                                                                 .or_insert(Vec::new()).push(Arc::downgrade(&future.state));
 458                                                         Err(LightningError {
 459                                                                 err: "Channel being checked async".to_owned(),
 460                                                                 action: ErrorAction::IgnoreAndLog(Level::Gossip),
 461                                                         })
 462                                                 }
 463                                         },
 464                                 }
 465                         }
 466                 }
 467         }
 468 }