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Check htlc_maximum_msat on channel update
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lightning/src/routing/network_graph.rs

Lines changed: 56 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@ use bitcoin::blockdata::opcodes;
1111

1212
use chain::chaininterface::{ChainError, ChainWatchInterface};
1313
use ln::features::{ChannelFeatures, NodeFeatures};
14-
use ln::msgs::{DecodeError, ErrorAction, LightningError, RoutingMessageHandler, NetAddress, OptionalField};
14+
use ln::msgs::{DecodeError, ErrorAction, LightningError, RoutingMessageHandler, NetAddress, OptionalField, MAX_VALUE_MSAT};
1515
use ln::msgs;
1616
use util::ser::{Writeable, Readable, Writer};
1717
use util::logger::Logger;
@@ -665,6 +665,21 @@ impl NetworkGraph {
665665
match self.channels.get_mut(&msg.contents.short_channel_id) {
666666
None => return Err(LightningError{err: "Couldn't find channel for update", action: ErrorAction::IgnoreError}),
667667
Some(channel) => {
668+
if let OptionalField::Present(htlc_maximum_msat) = msg.contents.htlc_maximum_msat {
669+
if htlc_maximum_msat > MAX_VALUE_MSAT {
670+
return Err(LightningError{err: "htlc_maximum_msat is larger than maximum possible msats", action: ErrorAction::IgnoreError});
671+
}
672+
673+
if let Some(capacity_sats) = channel.capacity_sats {
674+
// It's possible channel capacity is available now, although it wasn't available at announcement (so the field is None).
675+
// Don't query UTXO set here to reduce DoS risks.
676+
if htlc_maximum_msat > capacity_sats * 1000 {
677+
return Err(LightningError{err: "htlc_maximum_msat is larger than channel capacity", action: ErrorAction::IgnoreError});
678+
}
679+
}
680+
681+
// TODO check that htlc_maximum_msat is less than max_htlc_value_in_flight_msat
682+
}
668683
macro_rules! maybe_update_channel_info {
669684
( $target: expr, $src_node: expr) => {
670685
if let Some(existing_chan_info) = $target.as_ref() {
@@ -782,7 +797,8 @@ mod tests {
782797
use ln::features::{ChannelFeatures, NodeFeatures};
783798
use routing::network_graph::{NetGraphMsgHandler, NetworkGraph};
784799
use ln::msgs::{OptionalField, RoutingMessageHandler, UnsignedNodeAnnouncement, NodeAnnouncement,
785-
UnsignedChannelAnnouncement, ChannelAnnouncement, UnsignedChannelUpdate, ChannelUpdate, HTLCFailChannelUpdate};
800+
UnsignedChannelAnnouncement, ChannelAnnouncement, UnsignedChannelUpdate, ChannelUpdate, HTLCFailChannelUpdate,
801+
MAX_VALUE_MSAT};
786802
use util::test_utils;
787803
use util::logger::Logger;
788804
use util::ser::{Readable, Writeable};
@@ -1117,7 +1133,11 @@ mod tests {
11171133

11181134
#[test]
11191135
fn handling_channel_update() {
1120-
let (secp_ctx, net_graph_msg_handler) = create_net_graph_msg_handler();
1136+
let secp_ctx = Secp256k1::new();
1137+
let logger: Arc<Logger> = Arc::new(test_utils::TestLogger::new());
1138+
let chain_monitor = Arc::new(test_utils::TestChainWatcher::new());
1139+
let net_graph_msg_handler = NetGraphMsgHandler::new(chain_monitor.clone(), Arc::clone(&logger));
1140+
11211141
let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
11221142
let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
11231143
let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
@@ -1128,8 +1148,16 @@ mod tests {
11281148
let zero_hash = Sha256dHash::hash(&[0; 32]);
11291149
let short_channel_id = 0;
11301150
let chain_hash = genesis_block(Network::Testnet).header.bitcoin_hash();
1151+
let amount_sats = 1000_000;
1152+
11311153
{
11321154
// Announce a channel we will update
1155+
let good_script = Builder::new().push_opcode(opcodes::all::OP_PUSHNUM_2)
1156+
.push_slice(&PublicKey::from_secret_key(&secp_ctx, node_1_btckey).serialize())
1157+
.push_slice(&PublicKey::from_secret_key(&secp_ctx, node_2_btckey).serialize())
1158+
.push_opcode(opcodes::all::OP_PUSHNUM_2)
1159+
.push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script().to_v0_p2wsh();
1160+
*chain_monitor.utxo_ret.lock().unwrap() = Ok((good_script.clone(), amount_sats));
11331161
let unsigned_announcement = UnsignedChannelAnnouncement {
11341162
features: ChannelFeatures::empty(),
11351163
chain_hash,
@@ -1217,6 +1245,31 @@ mod tests {
12171245
};
12181246
unsigned_channel_update.short_channel_id = short_channel_id;
12191247

1248+
unsigned_channel_update.htlc_maximum_msat = OptionalField::Present(MAX_VALUE_MSAT + 1);
1249+
let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_channel_update.encode()[..])[..]);
1250+
let valid_channel_update = ChannelUpdate {
1251+
signature: secp_ctx.sign(&msghash, node_1_privkey),
1252+
contents: unsigned_channel_update.clone()
1253+
};
1254+
1255+
match net_graph_msg_handler.handle_channel_update(&valid_channel_update) {
1256+
Ok(_) => panic!(),
1257+
Err(e) => assert_eq!(e.err, "htlc_maximum_msat is larger than maximum possible msats")
1258+
};
1259+
unsigned_channel_update.htlc_maximum_msat = OptionalField::Absent;
1260+
1261+
unsigned_channel_update.htlc_maximum_msat = OptionalField::Present(amount_sats * 1000 + 1);
1262+
let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_channel_update.encode()[..])[..]);
1263+
let valid_channel_update = ChannelUpdate {
1264+
signature: secp_ctx.sign(&msghash, node_1_privkey),
1265+
contents: unsigned_channel_update.clone()
1266+
};
1267+
1268+
match net_graph_msg_handler.handle_channel_update(&valid_channel_update) {
1269+
Ok(_) => panic!(),
1270+
Err(e) => assert_eq!(e.err, "htlc_maximum_msat is larger than channel capacity")
1271+
};
1272+
unsigned_channel_update.htlc_maximum_msat = OptionalField::Absent;
12201273

12211274
// Even though previous update was not relayed further, we still accepted it,
12221275
// so we now won't accept update before the previous one.

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