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public static peel_onion method on OnionMessenger
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@Evanfeenstra
Evanfeenstra committed Oct 14, 2023
1 parent 989304e commit be9206c
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Showing 2 changed files with 109 additions and 78 deletions.
185 changes: 108 additions & 77 deletions lightning/src/onion_message/messenger.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -246,6 +246,16 @@ pub trait CustomOnionMessageHandler {
fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
}

/// A processed incoming onion message, containing either a Forward (another onion message)
/// or a Receive payload with decrypted contents.
pub enum PeeledOnion<CMH: Deref> where
CMH::Target: CustomOnionMessageHandler,
{
/// Forwarded onion, with the next node id and a new onion
Forward(PublicKey, msgs::OnionMessage),
/// Received onion message, with decrypted contents, path_id, and reply path
Receive(OnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>, Option<[u8; 32]>, Option<BlindedPath>)
}

/// Create an onion message with contents `message` to the destination of `path`.
/// Returns (introduction_node_id, onion_msg)
Expand Down Expand Up @@ -357,6 +367,96 @@ where
}
}

/// Decode one layer of an incoming onion message
/// Returns either a Forward (another onion message), or Receive (decrypted content)
pub fn peel_onion<T: CustomOnionMessageContents>(
node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>, logger: &L, custom_handler: &CMH,
msg: &msgs::OnionMessage,
) -> Result<PeeledOnion<CMH>, ()> {
let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
Ok(ss) => ss,
Err(e) => {
log_error!(logger, "Failed to retrieve node secret: {:?}", e);
return Err(());
}
};
let onion_decode_ss = {
let blinding_factor = {
let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
hmac.input(control_tlvs_ss.as_ref());
Hmac::from_engine(hmac).into_inner()
};
match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
{
Ok(ss) => ss.secret_bytes(),
Err(()) => {
log_trace!(logger, "Failed to compute onion packet shared secret");
return Err(());
}
}
};
match onion_utils::decode_next_untagged_hop(
onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
(control_tlvs_ss, custom_handler.deref(), logger.deref())
) {
Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
}, None)) => {
Ok(PeeledOnion::Receive(message, path_id, reply_path))
},
Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
next_node_id, next_blinding_override
})), Some((next_hop_hmac, new_packet_bytes)))) => {
// TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
// blinded hop and this onion message is destined for us. In this situation, we should keep
// unwrapping the onion layers to get to the final payload. Since we don't have the option
// of creating blinded paths with dummy hops currently, we should be ok to not handle this
// for now.
let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
Ok(pk) => pk,
Err(e) => {
log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
return Err(())
}
};
let outgoing_packet = Packet {
version: 0,
public_key: new_pubkey,
hop_data: new_packet_bytes,
hmac: next_hop_hmac,
};
let onion_message = msgs::OnionMessage {
blinding_point: match next_blinding_override {
Some(blinding_point) => blinding_point,
None => {
match onion_utils::next_hop_pubkey(
&secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
) {
Ok(bp) => bp,
Err(e) => {
log_trace!(logger, "Failed to compute next blinding point: {}", e);
return Err(())
}
}
}
},
onion_routing_packet: outgoing_packet,
};

Ok(PeeledOnion::Forward(next_node_id, onion_message))
},
Err(e) => {
log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
Err(())
},
_ => {
log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
Err(())
},
}
}

fn respond_with_onion_message<T: CustomOnionMessageContents>(
&self, response: OnionMessageContents<T>, path_id: Option<[u8; 32]>,
reply_path: Option<BlindedPath>
Expand Down Expand Up @@ -457,40 +557,13 @@ where
/// soon we'll delegate the onion message to a handler that can generate invoices or send
/// payments.
fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
let control_tlvs_ss = match self.node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
Ok(ss) => ss,
Err(e) => {
log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
return
}
};
let onion_decode_ss = {
let blinding_factor = {
let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
hmac.input(control_tlvs_ss.as_ref());
Hmac::from_engine(hmac).into_inner()
};
match self.node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
{
Ok(ss) => ss.secret_bytes(),
Err(()) => {
log_trace!(self.logger, "Failed to compute onion packet shared secret");
return
}
}
};
match onion_utils::decode_next_untagged_hop(
onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
(control_tlvs_ss, &*self.custom_handler, &*self.logger)
match Self::peel_onion::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>(
&self.node_signer, &self.secp_ctx, &self.logger, &self.custom_handler, msg
) {
Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
}, None)) => {
Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
log_trace!(self.logger,
"Received an onion message with path_id {:02x?} and {} reply_path",
path_id, if reply_path.is_some() { "a" } else { "no" });

let response = match message {
OnionMessageContents::Offers(msg) => {
self.offers_handler.handle_message(msg)
Expand All @@ -501,50 +574,11 @@ where
.map(|msg| OnionMessageContents::Custom(msg))
},
};

if let Some(response) = response {
self.respond_with_onion_message(response, path_id, reply_path);
}
},
Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
next_node_id, next_blinding_override
})), Some((next_hop_hmac, new_packet_bytes)))) => {
// TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
// blinded hop and this onion message is destined for us. In this situation, we should keep
// unwrapping the onion layers to get to the final payload. Since we don't have the option
// of creating blinded paths with dummy hops currently, we should be ok to not handle this
// for now.
let new_pubkey = match onion_utils::next_hop_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
Ok(pk) => pk,
Err(e) => {
log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
return
}
};
let outgoing_packet = Packet {
version: 0,
public_key: new_pubkey,
hop_data: new_packet_bytes,
hmac: next_hop_hmac,
};
let onion_message = msgs::OnionMessage {
blinding_point: match next_blinding_override {
Some(blinding_point) => blinding_point,
None => {
match onion_utils::next_hop_pubkey(
&self.secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
) {
Ok(bp) => bp,
Err(e) => {
log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
return
}
}
}
},
onion_routing_packet: outgoing_packet,
};

Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
if outbound_buffer_full(&next_node_id, &pending_per_peer_msgs) {
log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
Expand All @@ -563,15 +597,12 @@ where
e.get_mut().push_back(onion_message);
log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
}
};
}
},
Err(e) => {
log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
},
_ => {
log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
},
};
log_error!(self.logger, "Failed to process onion message {:?}", e);
}
}
}

fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
Expand Down
2 changes: 1 addition & 1 deletion lightning/src/onion_message/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ mod packet;
mod functional_tests;

// Re-export structs so they can be imported with just the `onion_message::` module prefix.
pub use self::messenger::{CustomOnionMessageContents, CustomOnionMessageHandler, DefaultMessageRouter, Destination, MessageRouter, OnionMessageContents, OnionMessagePath, OnionMessenger, SendError, SimpleArcOnionMessenger, SimpleRefOnionMessenger};
pub use self::messenger::{CustomOnionMessageContents, CustomOnionMessageHandler, DefaultMessageRouter, Destination, MessageRouter, OnionMessageContents, OnionMessagePath, OnionMessenger, PeeledOnion, SendError, SimpleArcOnionMessenger, SimpleRefOnionMessenger};
pub use self::offers::{OffersMessage, OffersMessageHandler};
pub use self::packet::Packet;
pub(crate) use self::packet::ControlTlvs;

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