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Allow forwarding HTLCs that were constructed for previous config
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@wpaulino
wpaulino committed Jun 16, 2022
1 parent 14c8c4c commit bb0901a
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Showing 3 changed files with 91 additions and 21 deletions.
57 changes: 46 additions & 11 deletions lightning/src/ln/channelmanager.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2096,6 +2096,26 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
})
}

fn check_htlc_forward(
&self, htlc: &msgs::UpdateAddHTLC, amt_to_forward: u64, outgoing_cltv_value: u32, config: &ChannelConfig,
) -> Option<(&'static str, u16)> {
let fee = amt_to_forward.checked_mul(config.forwarding_fee_proportional_millionths as u64)
.and_then(|prop_fee| (prop_fee / 1000000).checked_add(config.forwarding_fee_base_msat as u64));
if fee.is_none() || htlc.amount_msat < fee.unwrap() || (htlc.amount_msat - fee.unwrap()) < amt_to_forward {
return Some((
"Prior hop has deviated from specified fees parameters or origin node has obsolete ones",
0x1000 | 12, // fee_insufficient
));
}
if (htlc.cltv_expiry as u64) < outgoing_cltv_value as u64 + config.cltv_expiry_delta as u64 {
return Some((
"Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
0x1000 | 13, // incorrect_cltv_expiry
));
}
None
}

fn decode_update_add_htlc_onion(&self, msg: &msgs::UpdateAddHTLC) -> (PendingHTLCStatus, MutexGuard<ChannelHolder<Signer>>) {
macro_rules! return_malformed_err {
($msg: expr, $err_code: expr) => {
Expand Down Expand Up @@ -2230,7 +2250,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
},
Some(id) => Some(id.clone()),
};
let (chan_update_opt, forwardee_cltv_expiry_delta) = if let Some(forwarding_id) = forwarding_id_opt {
let chan_update_opt = if let Some(forwarding_id) = forwarding_id_opt {
let chan = channel_state.as_mut().unwrap().by_id.get_mut(&forwarding_id).unwrap();
if !chan.should_announce() && !self.default_configuration.accept_forwards_to_priv_channels {
// Note that the behavior here should be identical to the above block - we
Expand All @@ -2246,6 +2266,14 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
}
let chan_update_opt = self.get_channel_update_for_onion(*short_channel_id, chan).ok();

// We attempt to forward the HTLC with the current policy, or the previous
// for a short period of time.
if let Some(prev_config) = chan.get_prev_config() {
if chan.get_update_time_counter() > prev_config.1 + 1 {
chan.clear_prev_config();
}
}

// Note that we could technically not return an error yet here and just hope
// that the connection is reestablished or monitor updated by the time we get
// around to doing the actual forward, but better to fail early if we can and
Expand All @@ -2257,18 +2285,25 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
if *amt_to_forward < chan.get_counterparty_htlc_minimum_msat() { // amount_below_minimum
break Some(("HTLC amount was below the htlc_minimum_msat", 0x1000 | 11, chan_update_opt));
}
let fee = amt_to_forward.checked_mul(chan.get_fee_proportional_millionths() as u64)
.and_then(|prop_fee| { (prop_fee / 1000000)
.checked_add(chan.get_outbound_forwarding_fee_base_msat() as u64) });
if fee.is_none() || msg.amount_msat < fee.unwrap() || (msg.amount_msat - fee.unwrap()) < *amt_to_forward { // fee_insufficient
break Some(("Prior hop has deviated from specified fees parameters or origin node has obsolete ones", 0x1000 | 12, chan_update_opt));
match self.check_htlc_forward(
&msg, *amt_to_forward, *outgoing_cltv_value, &chan.get_config(),
) {
Some((err, code)) => {
if let Some(prev_config) = chan.get_prev_config() {
if let Some((err, code)) = self.check_htlc_forward(
&msg, *amt_to_forward, *outgoing_cltv_value, &prev_config.0
) {
break Some((err, code, chan_update_opt));
}
} else {
break Some((err, code, chan_update_opt));
}
},
None => {},
}
(chan_update_opt, chan.get_cltv_expiry_delta())
} else { (None, MIN_CLTV_EXPIRY_DELTA) };
chan_update_opt
} else { None };

if (msg.cltv_expiry as u64) < (*outgoing_cltv_value) as u64 + forwardee_cltv_expiry_delta as u64 { // incorrect_cltv_expiry
break Some(("Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta", 0x1000 | 13, chan_update_opt));
}
let cur_height = self.best_block.read().unwrap().height() + 1;
// Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
// but we want to be robust wrt to counterparty packet sanitization (see
Expand Down
13 changes: 10 additions & 3 deletions lightning/src/ln/functional_test_utils.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1689,9 +1689,16 @@ pub fn do_claim_payment_along_route<'a, 'b, 'c>(origin_node: &Node<'a, 'b, 'c>,
($node: expr, $prev_node: expr, $next_node: expr, $new_msgs: expr) => {
{
$node.node.handle_update_fulfill_htlc(&$prev_node.node.get_our_node_id(), &next_msgs.as_ref().unwrap().0);
let fee = $node.node.channel_state.lock().unwrap()
.by_id.get(&next_msgs.as_ref().unwrap().0.channel_id).unwrap()
.config.options.forwarding_fee_base_msat;
let fee = {
let channel_state = $node.node.channel_state.lock().unwrap();
let channel = channel_state
.by_id.get(&next_msgs.as_ref().unwrap().0.channel_id).unwrap();
if let Some(prev_config) = channel.get_prev_config() {
prev_config.0.forwarding_fee_base_msat
} else {
channel.get_config().forwarding_fee_base_msat
}
};
expect_payment_forwarded!($node, $next_node, $prev_node, Some(fee as u64), false, false);
expected_total_fee_msat += fee as u64;
check_added_monitors!($node, 1);
Expand Down
42 changes: 35 additions & 7 deletions lightning/src/ln/onion_route_tests.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -616,9 +616,25 @@ fn test_onion_failure_stale_channel_update() {
const PAYMENT_AMT: u64 = 40000;
send_payment(&nodes[0], &[&nodes[1], &nodes[2]], PAYMENT_AMT);

// Closure to connect a block with a timestamp that will increase a channel's
// `update_time_counter`.
let connect_block = |timestamp: u32| {
connect_block(&nodes[1], &bitcoin::Block {
header: bitcoin::BlockHeader {
version: 2,
prev_blockhash: nodes[1].best_block_hash(),
merkle_root: Default::default(),
time: timestamp,
bits: 42,
nonce: 42,
},
txdata: vec![],
});
};

// Closure to update and retrieve the latest ChannelUpdate.
let update_and_get_channel_update = |config: &ChannelConfig, expect_new_update: bool,
prev_update: Option<&msgs::ChannelUpdate>| -> Option<msgs::ChannelUpdate> {
prev_update: Option<&msgs::ChannelUpdate>, expire_prev_config: bool| -> Option<msgs::ChannelUpdate> {
nodes[1].node.update_channel_config(
channel_to_update_counterparty, &[channel_to_update.2], config,
).unwrap();
Expand All @@ -634,13 +650,16 @@ fn test_onion_failure_stale_channel_update() {
if prev_update.is_some() {
assert!(new_update.contents.timestamp > prev_update.unwrap().contents.timestamp)
}
if expire_prev_config {
connect_block(new_update.contents.timestamp + 1);
}
Some(new_update)
};

// We'll be attempting to route payments using the default ChannelUpdate for channels. This will
// lead to onion failures at the first hop once we update the HTLC relay parameters for the
// second hop.
let (route, payment_hash, _, payment_secret) = get_route_and_payment_hash!(
let (route, payment_hash, payment_preimage, payment_secret) = get_route_and_payment_hash!(
nodes[0], nodes[2], PAYMENT_AMT
);
let expect_onion_failure = |name: &str, error_code: u16, channel_update: &msgs::ChannelUpdate| {
Expand All @@ -667,28 +686,37 @@ fn test_onion_failure_stale_channel_update() {
.find(|channel| channel.channel_id == channel_to_update.2).unwrap()
.config.unwrap();
config.forwarding_fee_base_msat = u32::max_value();
let msg = update_and_get_channel_update(&config, true, None).unwrap();
let msg = update_and_get_channel_update(&config, true, None, false).unwrap();

// The old policy should still be in effect until a new block is connected.
send_along_route_with_secret(&nodes[0], route.clone(), &[&[&nodes[1], &nodes[2]]], PAYMENT_AMT,
payment_hash, payment_secret);
claim_payment(&nodes[0], &[&nodes[1], &nodes[2]], payment_preimage);

// Connect a block, which should expire the previous config, leading to a failure when
// forwarding the HTLC.
connect_block(msg.contents.timestamp + 1);
expect_onion_failure("fee_insufficient", UPDATE|12, &msg);

// Redundant updates should not trigger a new ChannelUpdate.
assert!(update_and_get_channel_update(&config, false, None).is_none());
assert!(update_and_get_channel_update(&config, false, None, false).is_none());

// Similarly, updates that do not have an affect on ChannelUpdate should not trigger a new one.
config.force_close_avoidance_max_fee_satoshis *= 2;
assert!(update_and_get_channel_update(&config, false, None).is_none());
assert!(update_and_get_channel_update(&config, false, None, false).is_none());

// Reset the base fee to the default and increase the proportional fee which should trigger a
// new ChannelUpdate.
config.forwarding_fee_base_msat = default_config.forwarding_fee_base_msat;
config.cltv_expiry_delta = u16::max_value();
let msg = update_and_get_channel_update(&config, true, Some(&msg)).unwrap();
let msg = update_and_get_channel_update(&config, true, Some(&msg), true).unwrap();
expect_onion_failure("incorrect_cltv_expiry", UPDATE|13, &msg);

// Reset the proportional fee and increase the CLTV expiry delta which should trigger a new
// ChannelUpdate.
config.cltv_expiry_delta = default_config.cltv_expiry_delta;
config.forwarding_fee_proportional_millionths = u32::max_value();
let msg = update_and_get_channel_update(&config, true, Some(&msg)).unwrap();
let msg = update_and_get_channel_update(&config, true, Some(&msg), true).unwrap();
expect_onion_failure("fee_insufficient", UPDATE|12, &msg);

// To test persistence of the updated config, we'll re-initialize the ChannelManager.
Expand Down

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