Add option to accept or reject inbound channels
authorViktor Tigerström <viktortigerstrom@hotmail.com>
Tue, 25 Jan 2022 23:21:22 +0000 (00:21 +0100)
committerViktor Tigerström <viktortigerstrom@hotmail.com>
Sun, 13 Feb 2022 20:04:19 +0000 (21:04 +0100)
Add a new config flag `UserConfig::manually_accept_inbound_channels`,
which when set to true allows the node operator to accept or reject new
channel requests.

When set to true, `Event::OpenChannelRequest` will be triggered once a
request to open a new inbound channel is received. When accepting the
request, `ChannelManager::accept_inbound_channel` should be called.
Rejecting the request is done through
`ChannelManager::force_close_channel`.

lightning/src/ln/channel.rs
lightning/src/ln/channelmanager.rs
lightning/src/util/config.rs
lightning/src/util/events.rs

index e76656e75ce38e9ee9b65c513ebc8c916e7b4ac7..0ba92af44855f42674bff6a7513ad95ff47bdd80 100644 (file)
@@ -584,6 +584,19 @@ pub(super) struct Channel<Signer: Sign> {
        #[cfg(not(test))]
        closing_fee_limits: Option<(u64, u64)>,
 
+       /// Flag that ensures that `accept_inbound_channel` must be called before `funding_created`
+       /// is executed successfully. The reason for this flag is that when the
+       /// `UserConfig::manually_accept_inbound_channels` config flag is set to true, inbound channels
+       /// are required to be manually accepted by the node operator before the `msgs::AcceptChannel`
+       /// message is created and sent out. During the manual accept process, `accept_inbound_channel`
+       /// is called by `ChannelManager::accept_inbound_channel`.
+       ///
+       /// The flag counteracts that a counterparty node could theoretically send a
+       /// `msgs::FundingCreated` message before the node operator has manually accepted an inbound
+       /// channel request made by the counterparty node. That would execute `funding_created` before
+       /// `accept_inbound_channel`, and `funding_created` should therefore not execute successfully.
+       inbound_awaiting_accept: bool,
+
        /// The hash of the block in which the funding transaction was included.
        funding_tx_confirmed_in: Option<BlockHash>,
        funding_tx_confirmation_height: u32,
@@ -883,6 +896,8 @@ impl<Signer: Sign> Channel<Signer> {
                        closing_fee_limits: None,
                        target_closing_feerate_sats_per_kw: None,
 
+                       inbound_awaiting_accept: false,
+
                        funding_tx_confirmed_in: None,
                        funding_tx_confirmation_height: 0,
                        short_channel_id: None,
@@ -1182,6 +1197,8 @@ impl<Signer: Sign> Channel<Signer> {
                        closing_fee_limits: None,
                        target_closing_feerate_sats_per_kw: None,
 
+                       inbound_awaiting_accept: true,
+
                        funding_tx_confirmed_in: None,
                        funding_tx_confirmation_height: 0,
                        short_channel_id: None,
@@ -1973,6 +1990,9 @@ impl<Signer: Sign> Channel<Signer> {
                        // channel.
                        return Err(ChannelError::Close("Received funding_created after we got the channel!".to_owned()));
                }
+               if self.inbound_awaiting_accept {
+                       return Err(ChannelError::Close("FundingCreated message received before the channel was accepted".to_owned()));
+               }
                if self.commitment_secrets.get_min_seen_secret() != (1 << 48) ||
                                self.cur_counterparty_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER ||
                                self.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
@@ -4645,7 +4665,15 @@ impl<Signer: Sign> Channel<Signer> {
                }
        }
 
-       pub fn get_accept_channel(&self) -> msgs::AcceptChannel {
+       pub fn inbound_is_awaiting_accept(&self) -> bool {
+               self.inbound_awaiting_accept
+       }
+
+       /// Marks an inbound channel as accepted and generates a [`msgs::AcceptChannel`] message which
+       /// should be sent back to the counterparty node.
+       ///
+       /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
+       pub fn accept_inbound_channel(&mut self) -> msgs::AcceptChannel {
                if self.is_outbound() {
                        panic!("Tried to send accept_channel for an outbound channel?");
                }
@@ -4655,7 +4683,21 @@ impl<Signer: Sign> Channel<Signer> {
                if self.cur_holder_commitment_transaction_number != INITIAL_COMMITMENT_NUMBER {
                        panic!("Tried to send an accept_channel for a channel that has already advanced");
                }
+               if !self.inbound_awaiting_accept {
+                       panic!("The inbound channel has already been accepted");
+               }
+
+               self.inbound_awaiting_accept = false;
+
+               self.generate_accept_channel_message()
+       }
 
+       /// This function is used to explicitly generate a [`msgs::AcceptChannel`] message for an
+       /// inbound channel. If the intention is to accept an inbound channel, use
+       /// [`Channel::accept_inbound_channel`] instead.
+       ///
+       /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
+       fn generate_accept_channel_message(&self) -> msgs::AcceptChannel {
                let first_per_commitment_point = self.holder_signer.get_per_commitment_point(self.cur_holder_commitment_transaction_number, &self.secp_ctx);
                let keys = self.get_holder_pubkeys();
 
@@ -6064,6 +6106,8 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<(&'a K, u32)> for Channel<Signer>
                        closing_fee_limits: None,
                        target_closing_feerate_sats_per_kw,
 
+                       inbound_awaiting_accept: false,
+
                        funding_tx_confirmed_in,
                        funding_tx_confirmation_height,
                        short_channel_id,
@@ -6281,10 +6325,10 @@ mod tests {
                // Make sure A's dust limit is as we expect.
                let open_channel_msg = node_a_chan.get_open_channel(genesis_block(network).header.block_hash());
                let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[7; 32]).unwrap());
-               let node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), &open_channel_msg, 7, &config, 0, &&logger).unwrap();
+               let mut node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), &open_channel_msg, 7, &config, 0, &&logger).unwrap();
 
                // Node B --> Node A: accept channel, explicitly setting B's dust limit.
-               let mut accept_channel_msg = node_b_chan.get_accept_channel();
+               let mut accept_channel_msg = node_b_chan.accept_inbound_channel();
                accept_channel_msg.dust_limit_satoshis = 546;
                node_a_chan.accept_channel(&accept_channel_msg, &config.peer_channel_config_limits, &InitFeatures::known()).unwrap();
                node_a_chan.holder_dust_limit_satoshis = 1560;
@@ -6402,7 +6446,7 @@ mod tests {
                let mut node_b_chan = Channel::<EnforcingSigner>::new_from_req(&&feeest, &&keys_provider, node_b_node_id, &InitFeatures::known(), &open_channel_msg, 7, &config, 0, &&logger).unwrap();
 
                // Node B --> Node A: accept channel
-               let accept_channel_msg = node_b_chan.get_accept_channel();
+               let accept_channel_msg = node_b_chan.accept_inbound_channel();
                node_a_chan.accept_channel(&accept_channel_msg, &config.peer_channel_config_limits, &InitFeatures::known()).unwrap();
 
                // Node A --> Node B: funding created
index 9268afc66f7e97cf1a3f2829093f88d1f5b9be40..0ae0f8c3e8096e34970bd6f2e42452365d86c1cf 100644 (file)
@@ -4081,6 +4081,34 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                }
        }
 
+       /// Called to accept a request to open a channel after [`Event::OpenChannelRequest`] has been
+       /// triggered.
+       ///
+       /// The `temporary_channel_id` parameter indicates which inbound channel should be accepted.
+       ///
+       /// [`Event::OpenChannelRequest`]: crate::util::events::Event::OpenChannelRequest
+       pub fn accept_inbound_channel(&self, temporary_channel_id: &[u8; 32]) -> Result<(), APIError> {
+               let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(&self.total_consistency_lock, &self.persistence_notifier);
+
+               let mut channel_state_lock = self.channel_state.lock().unwrap();
+               let channel_state = &mut *channel_state_lock;
+               match channel_state.by_id.entry(temporary_channel_id.clone()) {
+                       hash_map::Entry::Occupied(mut channel) => {
+                               if !channel.get().inbound_is_awaiting_accept() {
+                                       return Err(APIError::APIMisuseError { err: "The channel isn't currently awaiting to be accepted.".to_owned() });
+                               }
+                               channel_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
+                                       node_id: channel.get().get_counterparty_node_id(),
+                                       msg: channel.get_mut().accept_inbound_channel(),
+                               });
+                       }
+                       hash_map::Entry::Vacant(_) => {
+                               return Err(APIError::ChannelUnavailable { err: "Can't accept a channel that doesn't exist".to_owned() });
+                       }
+               }
+               Ok(())
+       }
+
        fn internal_open_channel(&self, counterparty_node_id: &PublicKey, their_features: InitFeatures, msg: &msgs::OpenChannel) -> Result<(), MsgHandleErrInternal> {
                if msg.chain_hash != self.genesis_hash {
                        return Err(MsgHandleErrInternal::send_err_msg_no_close("Unknown genesis block hash".to_owned(), msg.temporary_channel_id.clone()));
@@ -4090,7 +4118,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                        return Err(MsgHandleErrInternal::send_err_msg_no_close("No inbound channels accepted".to_owned(), msg.temporary_channel_id.clone()));
                }
 
-               let channel = Channel::new_from_req(&self.fee_estimator, &self.keys_manager, counterparty_node_id.clone(),
+               let mut channel = Channel::new_from_req(&self.fee_estimator, &self.keys_manager, counterparty_node_id.clone(),
                                &their_features, msg, 0, &self.default_configuration, self.best_block.read().unwrap().height(), &self.logger)
                        .map_err(|e| MsgHandleErrInternal::from_chan_no_close(e, msg.temporary_channel_id))?;
                let mut channel_state_lock = self.channel_state.lock().unwrap();
@@ -4098,10 +4126,23 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                match channel_state.by_id.entry(channel.channel_id()) {
                        hash_map::Entry::Occupied(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close("temporary_channel_id collision!".to_owned(), msg.temporary_channel_id.clone())),
                        hash_map::Entry::Vacant(entry) => {
-                               channel_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
-                                       node_id: counterparty_node_id.clone(),
-                                       msg: channel.get_accept_channel(),
-                               });
+                               if !self.default_configuration.manually_accept_inbound_channels {
+                                       channel_state.pending_msg_events.push(events::MessageSendEvent::SendAcceptChannel {
+                                               node_id: counterparty_node_id.clone(),
+                                               msg: channel.accept_inbound_channel(),
+                                       });
+                               } else {
+                                       let mut pending_events = self.pending_events.lock().unwrap();
+                                       pending_events.push(
+                                               events::Event::OpenChannelRequest {
+                                                       temporary_channel_id: msg.temporary_channel_id.clone(),
+                                                       counterparty_node_id: counterparty_node_id.clone(),
+                                                       funding_satoshis: msg.funding_satoshis,
+                                                       push_msat: msg.push_msat,
+                                               }
+                                       );
+                               }
+
                                entry.insert(channel);
                        }
                }
index c591cacb3463fd6e216a24da8390bdce6ddde1f9..55d506e79f145a386919ecce11f54ea7adbb432f 100644 (file)
@@ -305,6 +305,20 @@ pub struct UserConfig {
        /// If this is set to false, we do not accept inbound requests to open a new channel.
        /// Default value: true.
        pub accept_inbound_channels: bool,
+       /// If this is set to true, the user needs to manually accept inbound requests to open a new
+       /// channel.
+       ///
+       /// When set to true, [`Event::OpenChannelRequest`] will be triggered once a request to open a
+       /// new inbound channel is received through a [`msgs::OpenChannel`] message. In that case, a
+       /// [`msgs::AcceptChannel`] message will not be sent back to the counterparty node unless the
+       /// user explicitly chooses to accept the request.
+       ///
+       /// Default value: false.
+       ///
+       /// [`Event::OpenChannelRequest`]: crate::util::events::Event::OpenChannelRequest
+       /// [`msgs::OpenChannel`]: crate::ln::msgs::OpenChannel
+       /// [`msgs::AcceptChannel`]: crate::ln::msgs::AcceptChannel
+       pub manually_accept_inbound_channels: bool,
 }
 
 impl Default for UserConfig {
@@ -315,6 +329,7 @@ impl Default for UserConfig {
                        channel_options: ChannelConfig::default(),
                        accept_forwards_to_priv_channels: false,
                        accept_inbound_channels: true,
+                       manually_accept_inbound_channels: false,
                }
        }
 }
index a4a733c8e503eff05212d6570ada728a4cb95c1e..8c9f5af4c0bf52cd9c2ea51cb2432373bea3b457 100644 (file)
@@ -29,7 +29,6 @@ use bitcoin::blockdata::script::Script;
 use bitcoin::hashes::Hash;
 use bitcoin::hashes::sha256::Hash as Sha256;
 use bitcoin::secp256k1::key::PublicKey;
-
 use io;
 use prelude::*;
 use core::time::Duration;
@@ -403,6 +402,34 @@ pub enum Event {
                /// May contain a closed channel if the HTLC sent along the path was fulfilled on chain.
                path: Vec<RouteHop>,
        },
+       /// Indicates a request to open a new channel by a peer.
+       ///
+       /// To accept the request, call [`ChannelManager::accept_inbound_channel`]. To reject the
+       /// request, call [`ChannelManager::force_close_channel`].
+       ///
+       /// The event is only triggered when a new open channel request is received and the
+       /// [`UserConfig::manually_accept_inbound_channels`] config flag is set to true.
+       ///
+       /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
+       /// [`ChannelManager::force_close_channel`]: crate::ln::channelmanager::ChannelManager::force_close_channel
+       /// [`UserConfig::manually_accept_inbound_channels`]: crate::util::config::UserConfig::manually_accept_inbound_channels
+       OpenChannelRequest {
+               /// The temporary channel ID of the channel requested to be opened.
+               ///
+               /// When responding to the request, the `temporary_channel_id` should be passed
+               /// back to the ChannelManager with [`ChannelManager::accept_inbound_channel`] to accept,
+               /// or to [`ChannelManager::force_close_channel`] to reject.
+               ///
+               /// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
+               /// [`ChannelManager::force_close_channel`]: crate::ln::channelmanager::ChannelManager::force_close_channel
+               temporary_channel_id: [u8; 32],
+               /// The node_id of the counterparty requesting to open the channel.
+               counterparty_node_id: PublicKey,
+               /// The channel value of the requested channel.
+               funding_satoshis: u64,
+               /// Our starting balance in the channel if the request is accepted, in milli-satoshi.
+               push_msat: u64,
+       },
 }
 
 impl Writeable for Event {
@@ -515,6 +542,11 @@ impl Writeable for Event {
                                        (2, payment_hash, required),
                                })
                        },
+                       &Event::OpenChannelRequest { .. } => {
+                               17u8.write(writer)?;
+                               // We never write the OpenChannelRequest events as, upon disconnection, peers
+                               // drop any channels which have not yet exchanged funding_signed.
+                       },
                        // Note that, going forward, all new events must only write data inside of
                        // `write_tlv_fields`. Versions 0.0.101+ will ignore odd-numbered events that write
                        // data via `write_tlv_fields`.
@@ -707,6 +739,10 @@ impl MaybeReadable for Event {
                                };
                                f()
                        },
+                       17u8 => {
+                               // Value 17 is used for `Event::OpenChannelRequest`.
+                               Ok(None)
+                       },
                        // Versions prior to 0.0.100 did not ignore odd types, instead returning InvalidValue.
                        // Version 0.0.100 failed to properly ignore odd types, possibly resulting in corrupt
                        // reads.