Move logic to check a ChannelAnnouncement to gossip_checking

This commit is deliberately move-only, though the code being moved
is somewhat crufty.

Author: TheBlueMatt

lightning/src/routing/gossip.rs

@@ -16,16 +16,14 @@ use bitcoin::secp256k1;
 
 use bitcoin::hashes::sha256d::Hash as Sha256dHash;
 use bitcoin::hashes::Hash;
-use bitcoin::blockdata::transaction::TxOut;
 use bitcoin::hash_types::BlockHash;
 
-use crate::ln::chan_utils::make_funding_redeemscript;
 use crate::ln::features::{ChannelFeatures, NodeFeatures, InitFeatures};
 use crate::ln::msgs::{DecodeError, ErrorAction, Init, LightningError, RoutingMessageHandler, NetAddress, MAX_VALUE_MSAT};
 use crate::ln::msgs::{ChannelAnnouncement, ChannelUpdate, NodeAnnouncement, GossipTimestampFilter};
 use crate::ln::msgs::{QueryChannelRange, ReplyChannelRange, QueryShortChannelIds, ReplyShortChannelIdsEnd};
 use crate::ln::msgs;
-use crate::routing::gossip_checking::{ChainAccess, ChainAccessError};
+use crate::routing::gossip_checking::{self, ChainAccess};
 use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer, MaybeReadable};
 use crate::util::logger::{Logger, Level};
 use crate::util::events::{MessageSendEvent, MessageSendEventsProvider};
@@ -42,7 +40,6 @@ use crate::sync::{RwLock, RwLockReadGuard};
 use core::sync::atomic::{AtomicUsize, Ordering};
 use crate::sync::Mutex;
 use core::ops::{Bound, Deref};
-use bitcoin::hashes::hex::ToHex;
 
 #[cfg(feature = "std")]
 use std::time::{SystemTime, UNIX_EPOCH};
@@ -1481,32 +1478,7 @@ impl<L: Deref> NetworkGraph<L> where L::Target: Logger {
 			}
 		}
 
-		let utxo_value = match &chain_access {
-			&None => {
-				// Tentatively accept, potentially exposing us to DoS attacks
-				None
-			},
-			&Some(ref chain_access) => {
-				match chain_access.get_utxo(&msg.chain_hash, msg.short_channel_id) {
-					Ok(TxOut { value, script_pubkey }) => {
-						let expected_script =
-							make_funding_redeemscript(&msg.bitcoin_key_1, &msg.bitcoin_key_2).to_v0_p2wsh();
-						if script_pubkey != expected_script {
-							return Err(LightningError{err: format!("Channel announcement key ({}) didn't match on-chain script ({})", expected_script.to_hex(), script_pubkey.to_hex()), action: ErrorAction::IgnoreError});
-						}
-						//TODO: Check if value is worth storing, use it to inform routing, and compare it
-						//to the new HTLC max field in channel_update
-						Some(value)
-					},
-					Err(ChainAccessError::UnknownChain) => {
-						return Err(LightningError{err: format!("Channel announced on an unknown chain ({})", msg.chain_hash.encode().to_hex()), action: ErrorAction::IgnoreError});
-					},
-					Err(ChainAccessError::UnknownTx) => {
-						return Err(LightningError{err: "Channel announced without corresponding UTXO entry".to_owned(), action: ErrorAction::IgnoreError});
-					},
-				}
-			},
-		};
+		let utxo_value = gossip_checking::check_channel_announcement(chain_access, msg)?;
 
 		#[allow(unused_mut, unused_assignments)]
 		let mut announcement_received_time = 0;

lightning/src/routing/gossip_checking.rs

@@ -5,6 +5,13 @@
 //! This module contains traits for LDK to access these UTXOs to check gossip data is correct.
 
 use bitcoin::{BlockHash, TxOut};
+use bitcoin::hashes::hex::ToHex;
+
+use crate::ln::chan_utils::make_funding_redeemscript;
+use crate::ln::msgs::{self, LightningError, ErrorAction};
+use crate::util::ser::Writeable;
+
+use core::ops::Deref;
 
 /// An error when accessing the chain via [`ChainAccess`].
 #[derive(Clone, Debug)]
@@ -26,3 +33,35 @@ pub trait ChainAccess {
 	/// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
 	fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result<TxOut, ChainAccessError>;
 }
+
+pub(crate) fn check_channel_announcement<A: Deref>(
+	chain_access: &Option<A>, msg: &msgs::UnsignedChannelAnnouncement
+) -> Result<Option<u64>, msgs::LightningError> where A::Target: ChainAccess {
+	let utxo_value = match chain_access {
+		&None => {
+			// Tentatively accept, potentially exposing us to DoS attacks
+			None
+		},
+		&Some(ref chain_access) => {
+			match chain_access.get_utxo(&msg.chain_hash, msg.short_channel_id) {
+				Ok(TxOut { value, script_pubkey }) => {
+					let expected_script =
+						make_funding_redeemscript(&msg.bitcoin_key_1, &msg.bitcoin_key_2).to_v0_p2wsh();
+					if script_pubkey != expected_script {
+						return Err(LightningError{err: format!("Channel announcement key ({}) didn't match on-chain script ({})", expected_script.to_hex(), script_pubkey.to_hex()), action: ErrorAction::IgnoreError});
+					}
+					//TODO: Check if value is worth storing, use it to inform routing, and compare it
+					//to the new HTLC max field in channel_update
+					Some(value)
+				},
+				Err(ChainAccessError::UnknownChain) => {
+					return Err(LightningError{err: format!("Channel announced on an unknown chain ({})", msg.chain_hash.encode().to_hex()), action: ErrorAction::IgnoreError});
+				},
+				Err(ChainAccessError::UnknownTx) => {
+					return Err(LightningError{err: "Channel announced without corresponding UTXO entry".to_owned(), action: ErrorAction::IgnoreError});
+				},
+			}
+		}
+	};
+	Ok(utxo_value)
+}