_ 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::util::ser::Writeable;
  22
  23 use crate::prelude::*;
  24
  25 use core::ops::Deref;
  26
  27 /// An error when accessing the chain via [`UtxoLookup`].
  28 #[derive(Clone, Debug)]
  29 pub enum UtxoLookupError {
  30         /// The requested chain is unknown.
  31         UnknownChain,
  32
  33         /// The requested transaction doesn't exist or hasn't confirmed.
  34         UnknownTx,
  35 }
  36
  37 /// The `UtxoLookup` trait defines behavior for accessing on-chain UTXOs.
  38 pub trait UtxoLookup {
  39         /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
  40         /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
  41         /// is unknown.
  42         ///
  43         /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
  44         fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result<TxOut, UtxoLookupError>;
  45 }
  46
  47 pub(crate) fn check_channel_announcement<U: Deref>(
  48         utxo_lookup: &Option<U>, msg: &msgs::UnsignedChannelAnnouncement
  49 ) -> Result<Option<u64>, msgs::LightningError> where U::Target: UtxoLookup {
  50         match utxo_lookup {
  51                 &None => {
  52                         // Tentatively accept, potentially exposing us to DoS attacks
  53                         Ok(None)
  54                 },
  55                 &Some(ref utxo_lookup) => {
  56                         match utxo_lookup.get_utxo(&msg.chain_hash, msg.short_channel_id) {
  57                                 Ok(TxOut { value, script_pubkey }) => {
  58                                         let expected_script =
  59                                                 make_funding_redeemscript_from_slices(msg.bitcoin_key_1.as_slice(), msg.bitcoin_key_2.as_slice()).to_v0_p2wsh();
  60                                         if script_pubkey != expected_script {
  61                                                 return Err(LightningError{
  62                                                         err: format!("Channel announcement key ({}) didn't match on-chain script ({})",
  63                                                                 expected_script.to_hex(), script_pubkey.to_hex()),
  64                                                         action: ErrorAction::IgnoreError
  65                                                 });
  66                                         }
  67                                         Ok(Some(value))
  68                                 },
  69                                 Err(UtxoLookupError::UnknownChain) => {
  70                                         Err(LightningError {
  71                                                 err: format!("Channel announced on an unknown chain ({})",
  72                                                         msg.chain_hash.encode().to_hex()),
  73                                                 action: ErrorAction::IgnoreError
  74                                         })
  75                                 },
  76                                 Err(UtxoLookupError::UnknownTx) => {
  77                                         Err(LightningError {
  78                                                 err: "Channel announced without corresponding UTXO entry".to_owned(),
  79                                                 action: ErrorAction::IgnoreError
  80                                         })
  81                                 },
  82                         }
  83                 }
  84         }
  85 }