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Make channel_type required #3896

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70be9bc
Make channel_type required
elnosh Jun 19, 2025
b525e38
f - feature bit in fuzz test and test case for rejecting channel
elnosh Jul 3, 2025
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26 changes: 13 additions & 13 deletions fuzz/src/full_stack.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1066,8 +1066,8 @@ fn two_peer_forwarding_seed() -> Vec<u8> {
ext_from_hex("0010 03000000000000000000000000000000", &mut test);
// inbound read from peer id 0 of len 32
ext_from_hex("030020", &mut test);
// init message (type 16) with static_remotekey required, no channel_type/anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa208aa2a0a9aaa 03000000000000000000000000000000", &mut test);
// init message (type 16) with static_remotekey required, no anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa210aa2a0a9aaa 03000000000000000000000000000000", &mut test);

// inbound read from peer id 0 of len 18
ext_from_hex("030012", &mut test);
Expand Down Expand Up @@ -1167,8 +1167,8 @@ fn two_peer_forwarding_seed() -> Vec<u8> {
ext_from_hex("0010 01000000000000000000000000000000", &mut test);
// inbound read from peer id 1 of len 32
ext_from_hex("030120", &mut test);
// init message (type 16) with static_remotekey required, no channel_type/anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa208aa2a0a9aaa 01000000000000000000000000000000", &mut test);
// init message (type 16) with static_remotekey required, no anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa210aa2a0a9aaa 01000000000000000000000000000000", &mut test);

// create outbound channel to peer 1 for 50k sat
ext_from_hex(
Expand All @@ -1180,17 +1180,17 @@ fn two_peer_forwarding_seed() -> Vec<u8> {

// inbound read from peer id 1 of len 18
ext_from_hex("030112", &mut test);
// message header indicating message length 274
ext_from_hex("0112 01000000000000000000000000000000", &mut test);
// message header indicating message length 278
ext_from_hex("0116 01000000000000000000000000000000", &mut test);
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Some of these comments need an update?

// inbound read from peer id 1 of len 255
ext_from_hex("0301ff", &mut test);
// beginning of accept_channel
ext_from_hex("0021 0000000000000000000000000000000000000000000000000000000000000e12 0000000000000162 00000000004c4b40 00000000000003e8 00000000000003e8 00000002 03f0 0005 030000000000000000000000000000000000000000000000000000000000000100 030000000000000000000000000000000000000000000000000000000000000200 030000000000000000000000000000000000000000000000000000000000000300 030000000000000000000000000000000000000000000000000000000000000400 030000000000000000000000000000000000000000000000000000000000000500 02660000000000000000000000000000", &mut test);
// inbound read from peer id 1 of len 35
ext_from_hex("030123", &mut test);
// inbound read from peer id 1 of len 39
ext_from_hex("030127", &mut test);
// rest of accept_channel and mac
ext_from_hex(
"0000000000000000000000000000000000 0000 01000000000000000000000000000000",
"0000000000000000000000000000000000 0000 01021000 01000000000000000000000000000000",
&mut test,
);

Expand Down Expand Up @@ -1582,8 +1582,8 @@ fn gossip_exchange_seed() -> Vec<u8> {
ext_from_hex("0010 03000000000000000000000000000000", &mut test);
// inbound read from peer id 0 of len 32
ext_from_hex("030020", &mut test);
// init message (type 16) with static_remotekey required, no channel_type/anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa20aaa2a0a9aaa 03000000000000000000000000000000", &mut test);
// init message (type 16) with static_remotekey required, no anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa210aa2a0a9aaa 03000000000000000000000000000000", &mut test);

// new inbound connection with id 1
ext_from_hex("01", &mut test);
Expand All @@ -1602,8 +1602,8 @@ fn gossip_exchange_seed() -> Vec<u8> {
ext_from_hex("0010 01000000000000000000000000000000", &mut test);
// inbound read from peer id 1 of len 32
ext_from_hex("030120", &mut test);
// init message (type 16) with static_remotekey required, no channel_type/anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa20aaa2a0a9aaa 01000000000000000000000000000000", &mut test);
// init message (type 16) with static_remotekey required, no anchors/taproot, and other bits optional and mac
ext_from_hex("0010 00021aaa 0008aaa210aa2a0a9aaa 01000000000000000000000000000000", &mut test);

// inbound read from peer id 0 of len 18
ext_from_hex("030012", &mut test);
Expand Down
76 changes: 28 additions & 48 deletions lightning/src/ln/channel.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3838,18 +3838,10 @@ where
return Err(ChannelError::close("Got an accept_channel message at a strange time".to_owned()));
}

if let Some(ty) = &common_fields.channel_type {
if ty != funding.get_channel_type() {
return Err(ChannelError::close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
}
} else if their_features.supports_channel_type() {
// Assume they've accepted the channel type as they said they understand it.
} else {
let channel_type = ChannelTypeFeatures::from_init(&their_features);
if channel_type != ChannelTypeFeatures::only_static_remote_key() {
return Err(ChannelError::close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
}
funding.channel_transaction_parameters.channel_type_features = channel_type;
let channel_type = common_fields.channel_type.as_ref()
.ok_or_else(|| ChannelError::close("option_channel_type assumed to be supported".to_owned()))?;
if channel_type != funding.get_channel_type() {
return Err(ChannelError::close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
}

if common_fields.dust_limit_satoshis > 21000000 * 100000000 {
Expand Down Expand Up @@ -11542,37 +11534,31 @@ where
/// [`msgs::CommonOpenChannelFields`].
#[rustfmt::skip]
pub(super) fn channel_type_from_open_channel(
common_fields: &msgs::CommonOpenChannelFields, their_features: &InitFeatures,
our_supported_features: &ChannelTypeFeatures
common_fields: &msgs::CommonOpenChannelFields, our_supported_features: &ChannelTypeFeatures
) -> Result<ChannelTypeFeatures, ChannelError> {
if let Some(channel_type) = &common_fields.channel_type {
if channel_type.supports_any_optional_bits() {
return Err(ChannelError::close("Channel Type field contained optional bits - this is not allowed".to_owned()));
}
let channel_type = common_fields.channel_type.as_ref()
.ok_or_else(|| ChannelError::close("option_channel_type assumed to be supported".to_owned()))?;

// We only support the channel types defined by the `ChannelManager` in
// `provided_channel_type_features`. The channel type must always support
// `static_remote_key`, either implicitly with `option_zero_fee_commitments`
// or explicitly.
if !channel_type.requires_static_remote_key() && !channel_type.requires_anchor_zero_fee_commitments() {
return Err(ChannelError::close("Channel Type was not understood - we require static remote key".to_owned()));
}
// Make sure we support all of the features behind the channel type.
if channel_type.requires_unknown_bits_from(&our_supported_features) {
return Err(ChannelError::close("Channel Type contains unsupported features".to_owned()));
}
let announce_for_forwarding = if (common_fields.channel_flags & 1) == 1 { true } else { false };
if channel_type.requires_scid_privacy() && announce_for_forwarding {
return Err(ChannelError::close("SCID Alias/Privacy Channel Type cannot be set on a public channel".to_owned()));
}
Ok(channel_type.clone())
} else {
let channel_type = ChannelTypeFeatures::from_init(&their_features);
if channel_type != ChannelTypeFeatures::only_static_remote_key() {
return Err(ChannelError::close("Only static_remote_key is supported for non-negotiated channel types".to_owned()));
}
Ok(channel_type)
if channel_type.supports_any_optional_bits() {
return Err(ChannelError::close("Channel Type field contained optional bits - this is not allowed".to_owned()));
}

// We only support the channel types defined by the `ChannelManager` in
// `provided_channel_type_features`. The channel type must always support
// `static_remote_key`, either implicitly with `option_zero_fee_commitments`
// or explicitly.
if !channel_type.requires_static_remote_key() && !channel_type.requires_anchor_zero_fee_commitments() {
return Err(ChannelError::close("Channel Type was not understood - we require static remote key".to_owned()));
}
// Make sure we support all of the features behind the channel type.
if channel_type.requires_unknown_bits_from(&our_supported_features) {
return Err(ChannelError::close("Channel Type contains unsupported features".to_owned()));
}
let announce_for_forwarding = if (common_fields.channel_flags & 1) == 1 { true } else { false };
if channel_type.requires_scid_privacy() && announce_for_forwarding {
return Err(ChannelError::close("SCID Alias/Privacy Channel Type cannot be set on a public channel".to_owned()));
}
Ok(channel_type.clone())
}

impl<SP: Deref> InboundV1Channel<SP>
Expand All @@ -11596,7 +11582,7 @@ where

// First check the channel type is known, failing before we do anything else if we don't
// support this channel type.
let channel_type = channel_type_from_open_channel(&msg.common_fields, their_features, our_supported_features)?;
let channel_type = channel_type_from_open_channel(&msg.common_fields, our_supported_features)?;

let holder_selected_channel_reserve_satoshis = get_holder_selected_channel_reserve_satoshis(msg.common_fields.funding_satoshis, config);
let counterparty_pubkeys = ChannelPublicKeys {
Expand Down Expand Up @@ -11993,13 +11979,7 @@ where
let holder_selected_channel_reserve_satoshis = get_v2_channel_reserve_satoshis(
channel_value_satoshis, MIN_CHAN_DUST_LIMIT_SATOSHIS);

// First check the channel type is known, failing before we do anything else if we don't
// support this channel type.
if msg.common_fields.channel_type.is_none() {
return Err(ChannelError::close(format!("Rejecting V2 channel {} missing channel_type",
msg.common_fields.temporary_channel_id)))
}
let channel_type = channel_type_from_open_channel(&msg.common_fields, their_features, our_supported_features)?;
let channel_type = channel_type_from_open_channel(&msg.common_fields, our_supported_features)?;
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Directly above there is already a check for non channel type. Is that redundant now?

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ah, yeah seems that can be removed, thanks


let counterparty_pubkeys = ChannelPublicKeys {
funding_pubkey: msg.common_fields.funding_pubkey,
Expand Down
117 changes: 103 additions & 14 deletions lightning/src/ln/channel_type_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -295,9 +295,9 @@ fn do_test_supports_channel_type(config: UserConfig, expected_channel_type: Chan
}

#[test]
fn test_rejects_implicit_simple_anchors() {
// Tests that if `option_anchors` is being negotiated implicitly through the intersection of
// each side's `InitFeatures`, it is rejected.
fn test_rejects_if_channel_type_not_set() {
// Tests that if `channel_type` is not set in `open_channel` and `accept_channel`, it is
// rejected.
let secp_ctx = Secp256k1::new();
let test_est = TestFeeEstimator::new(15000);
let fee_estimator = LowerBoundedFeeEstimator::new(&test_est);
Expand All @@ -312,13 +312,6 @@ fn test_rejects_implicit_simple_anchors() {

let config = UserConfig::default();

// See feature bit assignments: https://github.com/lightning/bolts/blob/master/09-features.md
let static_remote_key_required: u64 = 1 << 12;
let simple_anchors_required: u64 = 1 << 20;
let raw_init_features = static_remote_key_required | simple_anchors_required;
let init_features_with_simple_anchors =
InitFeatures::from_le_bytes(raw_init_features.to_le_bytes().to_vec());

let mut channel_a = OutboundV1Channel::<&TestKeysInterface>::new(
&fee_estimator,
&&keys_provider,
Expand All @@ -336,20 +329,18 @@ fn test_rejects_implicit_simple_anchors() {
)
.unwrap();

// Set `channel_type` to `None` to force the implicit feature negotiation.
// Set `channel_type` to `None` to cause failure.
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Shouldn't this coverage be kept?

// Since A supports both `static_remote_key` and `option_anchors`, but B only accepts
// `static_remote_key`, it will fail the channel.

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I thought no since the code doing that implicit negotiation will be removed

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I agree this can be removed - we have test_rejects_simple_anchors_channel_type that ensures we don't accept old anchors, now that we're assuming the feature there's no possibility that somebody can try to make us infer it (because we require channel_type).

let mut open_channel_msg =
channel_a.get_open_channel(ChainHash::using_genesis_block(network), &&logger).unwrap();
open_channel_msg.common_fields.channel_type = None;

// Since A supports both `static_remote_key` and `option_anchors`, but B only accepts
// `static_remote_key`, it will fail the channel.
let channel_b = InboundV1Channel::<&TestKeysInterface>::new(
&fee_estimator,
&&keys_provider,
&&keys_provider,
node_id_a,
&channelmanager::provided_channel_type_features(&config),
&init_features_with_simple_anchors,
&channelmanager::provided_init_features(&config),
&open_channel_msg,
7,
&config,
Expand All @@ -358,6 +349,104 @@ fn test_rejects_implicit_simple_anchors() {
/*is_0conf=*/ false,
);
assert!(channel_b.is_err());

open_channel_msg.common_fields.channel_type =
Some(channel_a.funding.get_channel_type().clone());
let mut channel_b = InboundV1Channel::<&TestKeysInterface>::new(
&fee_estimator,
&&keys_provider,
&&keys_provider,
node_id_a,
&channelmanager::provided_channel_type_features(&config),
&channelmanager::provided_init_features(&config),
&open_channel_msg,
7,
&config,
0,
&&logger,
/*is_0conf=*/ false,
)
.unwrap();

// Set `channel_type` to `None` in `accept_channel` to cause failure.
let mut accept_channel_msg = channel_b.get_accept_channel_message(&&logger).unwrap();
accept_channel_msg.common_fields.channel_type = None;

let res = channel_a.accept_channel(
&accept_channel_msg,
&config.channel_handshake_limits,
&channelmanager::provided_init_features(&config),
);
assert!(res.is_err());
}

#[test]
fn test_rejects_if_channel_type_differ() {
// Tests that if the `channel_type` in `accept_channel` does not match the one set in
// `open_channel` it rejects the channel.
let secp_ctx = Secp256k1::new();
let test_est = TestFeeEstimator::new(15000);
let fee_estimator = LowerBoundedFeeEstimator::new(&test_est);
let network = Network::Testnet;
let keys_provider = TestKeysInterface::new(&[42; 32], network);
let logger = TestLogger::new();

let node_id_a =
PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[1; 32]).unwrap());
let node_id_b =
PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[2; 32]).unwrap());

let config = UserConfig::default();

let mut channel_a = OutboundV1Channel::<&TestKeysInterface>::new(
&fee_estimator,
&&keys_provider,
&&keys_provider,
node_id_b,
&channelmanager::provided_init_features(&config),
10000000,
100000,
42,
&config,
0,
42,
None,
&logger,
)
.unwrap();

let open_channel_msg =
channel_a.get_open_channel(ChainHash::using_genesis_block(network), &&logger).unwrap();

let mut channel_b = InboundV1Channel::<&TestKeysInterface>::new(
&fee_estimator,
&&keys_provider,
&&keys_provider,
node_id_a,
&channelmanager::provided_channel_type_features(&config),
&channelmanager::provided_init_features(&config),
&open_channel_msg,
7,
&config,
0,
&&logger,
/*is_0conf=*/ false,
)
.unwrap();

// Change the `channel_type` in `accept_channel` msg to make it different from the one set in
// `open_channel` to cause failure.
let mut accept_channel_msg = channel_b.get_accept_channel_message(&&logger).unwrap();
let mut channel_type = channelmanager::provided_channel_type_features(&config);
channel_type.set_zero_conf_required();
accept_channel_msg.common_fields.channel_type = Some(channel_type.clone());

let res = channel_a.accept_channel(
&accept_channel_msg,
&config.channel_handshake_limits,
&channelmanager::provided_init_features(&config),
);
assert!(res.is_err());
}

#[test]
Expand Down
4 changes: 2 additions & 2 deletions lightning/src/ln/channelmanager.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8593,7 +8593,7 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
// We can get the channel type at this point already as we'll need it immediately in both the
// manual and the automatic acceptance cases.
let channel_type = channel::channel_type_from_open_channel(
common_fields, &peer_state.latest_features, &self.channel_type_features()
common_fields, &self.channel_type_features()
).map_err(|e| MsgHandleErrInternal::from_chan_no_close(e, common_fields.temporary_channel_id))?;

// If we're doing manual acceptance checks on the channel, then defer creation until we're sure we want to accept.
Expand Down Expand Up @@ -13694,7 +13694,7 @@ pub fn provided_init_features(config: &UserConfig) -> InitFeatures {
features.set_basic_mpp_optional();
features.set_wumbo_optional();
features.set_shutdown_any_segwit_optional();
features.set_channel_type_optional();
features.set_channel_type_required();
features.set_scid_privacy_optional();
features.set_zero_conf_optional();
features.set_route_blinding_optional();
Expand Down
11 changes: 4 additions & 7 deletions lightning/src/ln/msgs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -242,10 +242,8 @@ pub struct CommonOpenChannelFields {
/// Optionally, a request to pre-set the to-channel-initiator output's scriptPubkey for when we
/// collaboratively close
pub shutdown_scriptpubkey: Option<ScriptBuf>,
/// The channel type that this channel will represent
///
/// If this is `None`, we derive the channel type from the intersection of our
/// feature bits with our counterparty's feature bits from the [`Init`] message.
/// The channel type that this channel will represent. As defined in the latest
/// specification, this field is required. However, it is an `Option` for legacy reasons.
pub channel_type: Option<ChannelTypeFeatures>,
}

Expand Down Expand Up @@ -356,9 +354,8 @@ pub struct CommonAcceptChannelFields {
/// Optionally, a request to pre-set the to-channel-acceptor output's scriptPubkey for when we
/// collaboratively close
pub shutdown_scriptpubkey: Option<ScriptBuf>,
/// The channel type that this channel will represent. If none is set, we derive the channel
/// type from the intersection of our feature bits with our counterparty's feature bits from
/// the Init message.
/// The channel type that this channel will represent. As defined in the latest
/// specification, this field is required. However, it is an `Option` for legacy reasons.
///
/// This is required to match the equivalent field in [`OpenChannel`] or [`OpenChannelV2`]'s
/// [`CommonOpenChannelFields::channel_type`].
Expand Down
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