rgb_lightning/onion_message/
messenger.rs

1// This file is Copyright its original authors, visible in version control
2// history.
3//
4// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7// You may not use this file except in accordance with one or both of these
8// licenses.
9
10//! LDK sends, receives, and forwards onion messages via the [`OnionMessenger`]. See its docs for
11//! more information.
12
13use bitcoin::hashes::{Hash, HashEngine};
14use bitcoin::hashes::hmac::{Hmac, HmacEngine};
15use bitcoin::hashes::sha256::Hash as Sha256;
16use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
17
18use crate::chain::keysinterface::{KeysInterface, KeysManager, Recipient};
19use crate::ln::features::{InitFeatures, NodeFeatures};
20use crate::ln::msgs::{self, OnionMessageHandler};
21use crate::ln::onion_utils;
22use crate::ln::peer_handler::IgnoringMessageHandler;
23use super::blinded_path::{BlindedPath, ForwardTlvs, ReceiveTlvs};
24pub use super::packet::{CustomOnionMessageContents, OnionMessageContents};
25use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload, ReceiveControlTlvs, SMALL_PACKET_HOP_DATA_LEN};
26use super::utils;
27use crate::util::events::OnionMessageProvider;
28use crate::util::logger::Logger;
29use crate::util::ser::Writeable;
30
31use core::ops::Deref;
32use crate::io;
33use crate::sync::{Arc, Mutex};
34use crate::prelude::*;
35
36/// A sender, receiver and forwarder of onion messages. In upcoming releases, this object will be
37/// used to retrieve invoices and fulfill invoice requests from [offers]. Currently, only sending
38/// and receiving custom onion messages is supported.
39///
40/// # Example
41///
42/// ```
43/// # extern crate bitcoin;
44/// # use bitcoin::hashes::_export::_core::time::Duration;
45/// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
46/// # use lightning::chain::keysinterface::{InMemorySigner, KeysManager, KeysInterface};
47/// # use lightning::ln::msgs::DecodeError;
48/// # use lightning::ln::peer_handler::IgnoringMessageHandler;
49/// # use lightning::onion_message::{BlindedPath, CustomOnionMessageContents, Destination, OnionMessageContents, OnionMessenger};
50/// # use lightning::util::logger::{Logger, Record};
51/// # use lightning::util::ser::{Writeable, Writer};
52/// # use lightning::io;
53/// # use std::sync::Arc;
54/// # struct FakeLogger {};
55/// # impl Logger for FakeLogger {
56/// #     fn log(&self, record: &Record) { unimplemented!() }
57/// # }
58/// # let seed = [42u8; 32];
59/// # let time = Duration::from_secs(123456);
60/// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
61/// # let logger = Arc::new(FakeLogger {});
62/// # let node_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
63/// # let secp_ctx = Secp256k1::new();
64/// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
65/// # let (hop_node_id2, hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1, hop_node_id1);
66/// # let destination_node_id = hop_node_id1;
67/// # let your_custom_message_handler = IgnoringMessageHandler {};
68/// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
69/// // ChannelManager.
70/// let onion_messenger = OnionMessenger::new(&keys_manager, logger, your_custom_message_handler);
71///
72/// # struct YourCustomMessage {}
73/// impl Writeable for YourCustomMessage {
74/// 	fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
75/// 		# Ok(())
76/// 		// Write your custom onion message to `w`
77/// 	}
78/// }
79/// impl CustomOnionMessageContents for YourCustomMessage {
80/// 	fn tlv_type(&self) -> u64 {
81/// 		# let your_custom_message_type = 42;
82/// 		your_custom_message_type
83/// 	}
84/// }
85/// // Send a custom onion message to a node id.
86/// let intermediate_hops = [hop_node_id1, hop_node_id2];
87/// let reply_path = None;
88/// # let your_custom_message = YourCustomMessage {};
89/// let message = OnionMessageContents::Custom(your_custom_message);
90/// onion_messenger.send_onion_message(&intermediate_hops, Destination::Node(destination_node_id), message, reply_path);
91///
92/// // Create a blinded path to yourself, for someone to send an onion message to.
93/// # let your_node_id = hop_node_id1;
94/// let hops = [hop_node_id3, hop_node_id4, your_node_id];
95/// let blinded_path = BlindedPath::new(&hops, &keys_manager, &secp_ctx).unwrap();
96///
97/// // Send a custom onion message to a blinded path.
98/// # let intermediate_hops = [hop_node_id1, hop_node_id2];
99/// let reply_path = None;
100/// # let your_custom_message = YourCustomMessage {};
101/// let message = OnionMessageContents::Custom(your_custom_message);
102/// onion_messenger.send_onion_message(&intermediate_hops, Destination::BlindedPath(blinded_path), message, reply_path);
103/// ```
104///
105/// [offers]: <https://github.com/lightning/bolts/pull/798>
106/// [`OnionMessenger`]: crate::onion_message::OnionMessenger
107pub struct OnionMessenger<K: Deref, L: Deref, CMH: Deref>
108	where K::Target: KeysInterface,
109	      L::Target: Logger,
110	      CMH:: Target: CustomOnionMessageHandler,
111{
112	keys_manager: K,
113	logger: L,
114	pending_messages: Mutex<HashMap<PublicKey, VecDeque<msgs::OnionMessage>>>,
115	secp_ctx: Secp256k1<secp256k1::All>,
116	custom_handler: CMH,
117	// Coming soon:
118	// invoice_handler: InvoiceHandler,
119}
120
121/// The destination of an onion message.
122pub enum Destination {
123	/// We're sending this onion message to a node.
124	Node(PublicKey),
125	/// We're sending this onion message to a blinded path.
126	BlindedPath(BlindedPath),
127}
128
129impl Destination {
130	pub(super) fn num_hops(&self) -> usize {
131		match self {
132			Destination::Node(_) => 1,
133			Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
134		}
135	}
136}
137
138/// Errors that may occur when [sending an onion message].
139///
140/// [sending an onion message]: OnionMessenger::send_onion_message
141#[derive(Debug, PartialEq, Eq)]
142pub enum SendError {
143	/// Errored computing onion message packet keys.
144	Secp256k1(secp256k1::Error),
145	/// Because implementations such as Eclair will drop onion messages where the message packet
146	/// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
147	TooBigPacket,
148	/// The provided [`Destination`] was an invalid [`BlindedPath`], due to having fewer than two
149	/// blinded hops.
150	TooFewBlindedHops,
151	/// Our next-hop peer was offline or does not support onion message forwarding.
152	InvalidFirstHop,
153	/// Onion message contents must have a TLV type >= 64.
154	InvalidMessage,
155	/// Our next-hop peer's buffer was full or our total outbound buffer was full.
156	BufferFull,
157	/// Failed to retrieve our node id from the provided [`KeysInterface`].
158	///
159	/// [`KeysInterface`]: crate::chain::keysinterface::KeysInterface
160	GetNodeIdFailed,
161	/// We attempted to send to a blinded path where we are the introduction node, and failed to
162	/// advance the blinded path to make the second hop the new introduction node. Either
163	/// [`KeysInterface::ecdh`] failed, we failed to tweak the current blinding point to get the
164	/// new blinding point, or we were attempting to send to ourselves.
165	BlindedPathAdvanceFailed,
166}
167
168/// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
169/// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
170/// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
171/// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
172/// message types.
173///
174/// See [`OnionMessenger`] for example usage.
175///
176/// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
177/// [`CustomMessage`]: Self::CustomMessage
178pub trait CustomOnionMessageHandler {
179	/// The message known to the handler. To support multiple message types, you may want to make this
180	/// an enum with a variant for each supported message.
181	type CustomMessage: CustomOnionMessageContents;
182	/// Called with the custom message that was received.
183	fn handle_custom_message(&self, msg: Self::CustomMessage);
184	/// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
185	/// message type is unknown.
186	fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
187}
188
189impl<K: Deref, L: Deref, CMH: Deref> OnionMessenger<K, L, CMH>
190	where K::Target: KeysInterface,
191	      L::Target: Logger,
192	      CMH::Target: CustomOnionMessageHandler,
193{
194	/// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
195	/// their respective handlers.
196	pub fn new(keys_manager: K, logger: L, custom_handler: CMH) -> Self {
197		let mut secp_ctx = Secp256k1::new();
198		secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
199		OnionMessenger {
200			keys_manager,
201			pending_messages: Mutex::new(HashMap::new()),
202			secp_ctx,
203			logger,
204			custom_handler,
205		}
206	}
207
208	/// Send an onion message with contents `message` to `destination`, routing it through `intermediate_nodes`.
209	/// See [`OnionMessenger`] for example usage.
210	pub fn send_onion_message<T: CustomOnionMessageContents>(&self, intermediate_nodes: &[PublicKey], mut destination: Destination, message: OnionMessageContents<T>, reply_path: Option<BlindedPath>) -> Result<(), SendError> {
211		if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
212			if blinded_hops.len() < 2 {
213				return Err(SendError::TooFewBlindedHops);
214			}
215		}
216		let OnionMessageContents::Custom(ref msg) = message;
217		if msg.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
218
219		// If we are sending straight to a blinded path and we are the introduction node, we need to
220		// advance the blinded path by 1 hop so the second hop is the new introduction node.
221		if intermediate_nodes.len() == 0 {
222			if let Destination::BlindedPath(ref mut blinded_path) = destination {
223				let our_node_id = self.keys_manager.get_node_id(Recipient::Node)
224					.map_err(|()| SendError::GetNodeIdFailed)?;
225				if blinded_path.introduction_node_id == our_node_id {
226					blinded_path.advance_by_one(&self.keys_manager, &self.secp_ctx)
227						.map_err(|()| SendError::BlindedPathAdvanceFailed)?;
228				}
229			}
230		}
231
232		let blinding_secret_bytes = self.keys_manager.get_secure_random_bytes();
233		let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
234		let (introduction_node_id, blinding_point) = if intermediate_nodes.len() != 0 {
235			(intermediate_nodes[0], PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret))
236		} else {
237			match destination {
238				Destination::Node(pk) => (pk, PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret)),
239				Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
240					(introduction_node_id, blinding_point),
241			}
242		};
243		let (packet_payloads, packet_keys) = packet_payloads_and_keys(
244			&self.secp_ctx, intermediate_nodes, destination, message, reply_path, &blinding_secret)
245			.map_err(|e| SendError::Secp256k1(e))?;
246
247		let prng_seed = self.keys_manager.get_secure_random_bytes();
248		let onion_routing_packet = construct_onion_message_packet(
249			packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
250
251		let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
252		if outbound_buffer_full(&introduction_node_id, &pending_per_peer_msgs) { return Err(SendError::BufferFull) }
253		match pending_per_peer_msgs.entry(introduction_node_id) {
254			hash_map::Entry::Vacant(_) => Err(SendError::InvalidFirstHop),
255			hash_map::Entry::Occupied(mut e) => {
256				e.get_mut().push_back(msgs::OnionMessage { blinding_point, onion_routing_packet });
257				Ok(())
258			}
259		}
260	}
261
262	#[cfg(test)]
263	pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<msgs::OnionMessage>> {
264		let mut pending_msgs = self.pending_messages.lock().unwrap();
265		let mut msgs = HashMap::new();
266		// We don't want to disconnect the peers by removing them entirely from the original map, so we
267		// swap the pending message buffers individually.
268		for (peer_node_id, pending_messages) in &mut *pending_msgs {
269			msgs.insert(*peer_node_id, core::mem::take(pending_messages));
270		}
271		msgs
272	}
273}
274
275fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, VecDeque<msgs::OnionMessage>>) -> bool {
276	const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
277	const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
278	let mut total_buffered_bytes = 0;
279	let mut peer_buffered_bytes = 0;
280	for (pk, peer_buf) in buffer {
281		for om in peer_buf {
282			let om_len = om.serialized_length();
283			if pk == peer_node_id {
284				peer_buffered_bytes += om_len;
285			}
286			total_buffered_bytes += om_len;
287
288			if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
289				peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
290			{
291				return true
292			}
293		}
294	}
295	false
296}
297
298impl<K: Deref, L: Deref, CMH: Deref> OnionMessageHandler for OnionMessenger<K, L, CMH>
299	where K::Target: KeysInterface,
300	      L::Target: Logger,
301	      CMH::Target: CustomOnionMessageHandler + Sized,
302{
303	/// Handle an incoming onion message. Currently, if a message was destined for us we will log, but
304	/// soon we'll delegate the onion message to a handler that can generate invoices or send
305	/// payments.
306	fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
307		let control_tlvs_ss = match self.keys_manager.ecdh(Recipient::Node, &msg.blinding_point, None) {
308			Ok(ss) => ss,
309			Err(e) =>  {
310				log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
311				return
312			}
313		};
314		let onion_decode_ss = {
315			let blinding_factor = {
316				let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
317				hmac.input(control_tlvs_ss.as_ref());
318				Hmac::from_engine(hmac).into_inner()
319			};
320			match self.keys_manager.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
321				Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
322			{
323				Ok(ss) => ss.secret_bytes(),
324				Err(()) => {
325					log_trace!(self.logger, "Failed to compute onion packet shared secret");
326					return
327				}
328			}
329		};
330		match onion_utils::decode_next_untagged_hop(onion_decode_ss, &msg.onion_routing_packet.hop_data[..],
331			msg.onion_routing_packet.hmac, (control_tlvs_ss, &*self.custom_handler))
332		{
333			Ok((Payload::Receive::<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage> {
334				message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
335			}, None)) => {
336				log_info!(self.logger,
337					"Received an onion message with path_id {:02x?} and {} reply_path",
338						path_id, if reply_path.is_some() { "a" } else { "no" });
339				match message {
340					OnionMessageContents::Custom(msg) => self.custom_handler.handle_custom_message(msg),
341				}
342			},
343			Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
344				next_node_id, next_blinding_override
345			})), Some((next_hop_hmac, new_packet_bytes)))) => {
346				// TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
347				// blinded hop and this onion message is destined for us. In this situation, we should keep
348				// unwrapping the onion layers to get to the final payload. Since we don't have the option
349				// of creating blinded paths with dummy hops currently, we should be ok to not handle this
350				// for now.
351				let new_pubkey = match onion_utils::next_hop_packet_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
352					Ok(pk) => pk,
353					Err(e) => {
354						log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
355						return
356					}
357				};
358				let outgoing_packet = Packet {
359					version: 0,
360					public_key: new_pubkey,
361					hop_data: new_packet_bytes,
362					hmac: next_hop_hmac,
363				};
364				let onion_message = msgs::OnionMessage {
365					blinding_point: match next_blinding_override {
366						Some(blinding_point) => blinding_point,
367						None => {
368							let blinding_factor = {
369								let mut sha = Sha256::engine();
370								sha.input(&msg.blinding_point.serialize()[..]);
371								sha.input(control_tlvs_ss.as_ref());
372								Sha256::from_engine(sha).into_inner()
373							};
374							let next_blinding_point = msg.blinding_point;
375							match next_blinding_point.mul_tweak(&self.secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap()) {
376								Ok(bp) => bp,
377								Err(e) => {
378									log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
379									return
380								}
381							}
382						},
383					},
384					onion_routing_packet: outgoing_packet,
385				};
386
387				let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
388				if outbound_buffer_full(&next_node_id, &pending_per_peer_msgs) {
389					log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
390					return
391				}
392
393				#[cfg(fuzzing)]
394				pending_per_peer_msgs.entry(next_node_id).or_insert_with(VecDeque::new);
395
396				match pending_per_peer_msgs.entry(next_node_id) {
397					hash_map::Entry::Vacant(_) => {
398						log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
399						return
400					},
401					hash_map::Entry::Occupied(mut e) => {
402						e.get_mut().push_back(onion_message);
403						log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
404					}
405				};
406			},
407			Err(e) => {
408				log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
409			},
410			_ => {
411				log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
412			},
413		};
414	}
415
416	fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init) -> Result<(), ()> {
417		if init.features.supports_onion_messages() {
418			let mut peers = self.pending_messages.lock().unwrap();
419			peers.insert(their_node_id.clone(), VecDeque::new());
420		}
421		Ok(())
422	}
423
424	fn peer_disconnected(&self, their_node_id: &PublicKey, _no_connection_possible: bool) {
425		let mut pending_msgs = self.pending_messages.lock().unwrap();
426		pending_msgs.remove(their_node_id);
427	}
428
429	fn provided_node_features(&self) -> NodeFeatures {
430		let mut features = NodeFeatures::empty();
431		features.set_onion_messages_optional();
432		features
433	}
434
435	fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
436		let mut features = InitFeatures::empty();
437		features.set_onion_messages_optional();
438		features
439	}
440}
441
442impl<K: Deref, L: Deref, CMH: Deref> OnionMessageProvider for OnionMessenger<K, L, CMH>
443	where K::Target: KeysInterface,
444	      L::Target: Logger,
445	      CMH::Target: CustomOnionMessageHandler,
446{
447	fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<msgs::OnionMessage> {
448		let mut pending_msgs = self.pending_messages.lock().unwrap();
449		if let Some(msgs) = pending_msgs.get_mut(&peer_node_id) {
450			return msgs.pop_front()
451		}
452		None
453	}
454}
455
456// TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
457// produces
458/// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
459/// [`SimpleArcPeerManager`]. See their docs for more details.
460///
461/// (C-not exported) as `Arc`s don't make sense in bindings.
462///
463/// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
464/// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
465pub type SimpleArcOnionMessenger<L> = OnionMessenger<Arc<KeysManager>, Arc<L>, IgnoringMessageHandler>;
466/// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
467/// [`SimpleRefPeerManager`]. See their docs for more details.
468///
469/// (C-not exported) as general type aliases don't make sense in bindings.
470///
471/// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
472/// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
473pub type SimpleRefOnionMessenger<'a, 'b, L> = OnionMessenger<&'a KeysManager, &'b L, IgnoringMessageHandler>;
474
475/// Construct onion packet payloads and keys for sending an onion message along the given
476/// `unblinded_path` to the given `destination`.
477fn packet_payloads_and_keys<T: CustomOnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
478	secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination,
479	message: OnionMessageContents<T>, mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
480) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
481	let num_hops = unblinded_path.len() + destination.num_hops();
482	let mut payloads = Vec::with_capacity(num_hops);
483	let mut onion_packet_keys = Vec::with_capacity(num_hops);
484
485	let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedPath(BlindedPath {
486		introduction_node_id, blinding_point, blinded_hops }) = &destination {
487		(Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
488	let num_unblinded_hops = num_hops - num_blinded_hops;
489
490	let mut unblinded_path_idx = 0;
491	let mut blinded_path_idx = 0;
492	let mut prev_control_tlvs_ss = None;
493	let mut final_control_tlvs = None;
494	utils::construct_keys_callback(secp_ctx, unblinded_path, Some(destination), session_priv, |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
495		if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
496			if let Some(ss) = prev_control_tlvs_ss.take() {
497				payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
498					ForwardTlvs {
499						next_node_id: unblinded_pk_opt.unwrap(),
500						next_blinding_override: None,
501					}
502				)), ss));
503			}
504			prev_control_tlvs_ss = Some(control_tlvs_ss);
505			unblinded_path_idx += 1;
506		} else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
507			if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
508				payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
509					next_node_id: intro_node_id,
510					next_blinding_override: Some(blinding_pt),
511				})), control_tlvs_ss));
512			}
513		}
514		if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
515			payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
516				control_tlvs_ss));
517			blinded_path_idx += 1;
518		} else if let Some(encrypted_payload) = enc_payload_opt {
519			final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
520			prev_control_tlvs_ss = Some(control_tlvs_ss);
521		}
522
523		let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
524		onion_packet_keys.push(onion_utils::OnionKeys {
525			#[cfg(test)]
526			shared_secret: onion_packet_ss,
527			#[cfg(test)]
528			blinding_factor: [0; 32],
529			ephemeral_pubkey,
530			rho,
531			mu,
532		});
533	})?;
534
535	if let Some(control_tlvs) = final_control_tlvs {
536		payloads.push((Payload::Receive {
537			control_tlvs,
538			reply_path: reply_path.take(),
539			message,
540		}, prev_control_tlvs_ss.unwrap()));
541	} else {
542		payloads.push((Payload::Receive {
543			control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
544			reply_path: reply_path.take(),
545			message,
546		}, prev_control_tlvs_ss.unwrap()));
547	}
548
549	Ok((payloads, onion_packet_keys))
550}
551
552/// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
553fn construct_onion_message_packet<T: CustomOnionMessageContents>(payloads: Vec<(Payload<T>, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Result<Packet, ()> {
554	// Spec rationale:
555	// "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
556	// onion, but this should be used sparingly as it is reduces anonymity set, hence the
557	// recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
558	let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
559	let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
560		SMALL_PACKET_HOP_DATA_LEN
561	} else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
562		BIG_PACKET_HOP_DATA_LEN
563	} else { return Err(()) };
564
565	Ok(onion_utils::construct_onion_message_packet::<_, _>(
566		payloads, onion_keys, prng_seed, hop_data_len))
567}
rgb_lightning/onion_message/messenger.rs

rgb_lightning/onion_message/
messenger.rs
