_ Git - rust-lightning/blob - lightning/src/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
  13 use bitcoin::hashes::{Hash, HashEngine};
  14 use bitcoin::hashes::hmac::{Hmac, HmacEngine};
  15 use bitcoin::hashes::sha256::Hash as Sha256;
  16 use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
  17
  18 use crate::blinded_path::BlindedPath;
  19 use crate::blinded_path::message::{advance_path_by_one, ForwardTlvs, ReceiveTlvs};
  20 use crate::blinded_path::utils;
  21 use crate::events::{Event, EventHandler, EventsProvider};
  22 use crate::sign::{EntropySource, KeysManager, NodeSigner, Recipient};
  23 #[cfg(not(c_bindings))]
  24 use crate::ln::channelmanager::{SimpleArcChannelManager, SimpleRefChannelManager};
  25 use crate::ln::features::{InitFeatures, NodeFeatures};
  26 use crate::ln::msgs::{self, OnionMessage, OnionMessageHandler, SocketAddress};
  27 use crate::ln::onion_utils;
  28 use crate::ln::peer_handler::IgnoringMessageHandler;
  29 use crate::routing::gossip::{NetworkGraph, NodeId};
  30 pub use super::packet::OnionMessageContents;
  31 use super::packet::ParsedOnionMessageContents;
  32 use super::offers::OffersMessageHandler;
  33 use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload, ReceiveControlTlvs, SMALL_PACKET_HOP_DATA_LEN};
  34 use crate::util::logger::Logger;
  35 use crate::util::ser::Writeable;
  36
  37 use core::fmt;
  38 use core::ops::Deref;
  39 use crate::io;
  40 use crate::sync::{Arc, Mutex};
  41 use crate::prelude::*;
  42
  43 /// A sender, receiver and forwarder of [`OnionMessage`]s.
  44 ///
  45 /// # Handling Messages
  46 ///
  47 /// `OnionMessenger` implements [`OnionMessageHandler`], making it responsible for either forwarding
  48 /// messages to peers or delegating to the appropriate handler for the message type. Currently, the
  49 /// available handlers are:
  50 /// * [`OffersMessageHandler`], for responding to [`InvoiceRequest`]s and paying [`Bolt12Invoice`]s
  51 /// * [`CustomOnionMessageHandler`], for handling user-defined message types
  52 ///
  53 /// # Sending Messages
  54 ///
  55 /// [`OnionMessage`]s are sent initially using [`OnionMessenger::send_onion_message`]. When handling
  56 /// a message, the matched handler may return a response message which `OnionMessenger` will send
  57 /// on its behalf.
  58 ///
  59 /// # Example
  60 ///
  61 /// ```
  62 /// # extern crate bitcoin;
  63 /// # use bitcoin::hashes::_export::_core::time::Duration;
  64 /// # use bitcoin::hashes::hex::FromHex;
  65 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
  66 /// # use lightning::blinded_path::BlindedPath;
  67 /// # use lightning::sign::KeysManager;
  68 /// # use lightning::ln::peer_handler::IgnoringMessageHandler;
  69 /// # use lightning::onion_message::{OnionMessageContents, Destination, MessageRouter, OnionMessagePath, OnionMessenger};
  70 /// # use lightning::util::logger::{Logger, Record};
  71 /// # use lightning::util::ser::{Writeable, Writer};
  72 /// # use lightning::io;
  73 /// # use std::sync::Arc;
  74 /// # struct FakeLogger;
  75 /// # impl Logger for FakeLogger {
  76 /// #     fn log(&self, record: Record) { println!("{:?}" , record); }
  77 /// # }
  78 /// # struct FakeMessageRouter {}
  79 /// # impl MessageRouter for FakeMessageRouter {
  80 /// #     fn find_path(&self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination) -> Result<OnionMessagePath, ()> {
  81 /// #         let secp_ctx = Secp256k1::new();
  82 /// #         let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
  83 /// #         let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
  84 /// #         let hop_node_id2 = hop_node_id1;
  85 /// #         Ok(OnionMessagePath {
  86 /// #             intermediate_nodes: vec![hop_node_id1, hop_node_id2],
  87 /// #             destination,
  88 /// #             addresses: None,
  89 /// #         })
  90 /// #     }
  91 /// # }
  92 /// # let seed = [42u8; 32];
  93 /// # let time = Duration::from_secs(123456);
  94 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
  95 /// # let logger = Arc::new(FakeLogger {});
  96 /// # let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
  97 /// # let secp_ctx = Secp256k1::new();
  98 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
  99 /// # let (hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1);
 100 /// # let destination_node_id = hop_node_id1;
 101 /// # let message_router = Arc::new(FakeMessageRouter {});
 102 /// # let custom_message_handler = IgnoringMessageHandler {};
 103 /// # let offers_message_handler = IgnoringMessageHandler {};
 104 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
 105 /// // ChannelManager.
 106 /// let onion_messenger = OnionMessenger::new(
 107 ///     &keys_manager, &keys_manager, logger, message_router, &offers_message_handler,
 108 ///     &custom_message_handler
 109 /// );
 110
 111 /// # #[derive(Debug)]
 112 /// # struct YourCustomMessage {}
 113 /// impl Writeable for YourCustomMessage {
 114 ///     fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 115 ///             # Ok(())
 116 ///             // Write your custom onion message to `w`
 117 ///     }
 118 /// }
 119 /// impl OnionMessageContents for YourCustomMessage {
 120 ///     fn tlv_type(&self) -> u64 {
 121 ///             # let your_custom_message_type = 42;
 122 ///             your_custom_message_type
 123 ///     }
 124 /// }
 125 /// // Send a custom onion message to a node id.
 126 /// let destination = Destination::Node(destination_node_id);
 127 /// let reply_path = None;
 128 /// # let message = YourCustomMessage {};
 129 /// onion_messenger.send_onion_message(message, destination, reply_path);
 130 ///
 131 /// // Create a blinded path to yourself, for someone to send an onion message to.
 132 /// # let your_node_id = hop_node_id1;
 133 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
 134 /// let blinded_path = BlindedPath::new_for_message(&hops, &keys_manager, &secp_ctx).unwrap();
 135 ///
 136 /// // Send a custom onion message to a blinded path.
 137 /// let destination = Destination::BlindedPath(blinded_path);
 138 /// let reply_path = None;
 139 /// # let message = YourCustomMessage {};
 140 /// onion_messenger.send_onion_message(message, destination, reply_path);
 141 /// ```
 142 ///
 143 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 144 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 145 pub struct OnionMessenger<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 146 where
 147         ES::Target: EntropySource,
 148         NS::Target: NodeSigner,
 149         L::Target: Logger,
 150         MR::Target: MessageRouter,
 151         OMH::Target: OffersMessageHandler,
 152         CMH:: Target: CustomOnionMessageHandler,
 153 {
 154         entropy_source: ES,
 155         node_signer: NS,
 156         logger: L,
 157         message_buffers: Mutex<HashMap<PublicKey, OnionMessageBuffer>>,
 158         secp_ctx: Secp256k1<secp256k1::All>,
 159         message_router: MR,
 160         offers_handler: OMH,
 161         custom_handler: CMH,
 162 }
 163
 164 /// [`OnionMessage`]s buffered to be sent.
 165 enum OnionMessageBuffer {
 166         /// Messages for a node connected as a peer.
 167         ConnectedPeer(VecDeque<OnionMessage>),
 168
 169         /// Messages for a node that is not yet connected, which are dropped after a certain number of
 170         /// timer ticks defined in [`OnionMessenger::timer_tick_occurred`] and tracked here.
 171         PendingConnection(VecDeque<OnionMessage>, Option<Vec<SocketAddress>>, usize),
 172 }
 173
 174 impl OnionMessageBuffer {
 175         fn pending_connection(addresses: Vec<SocketAddress>) -> Self {
 176                 Self::PendingConnection(VecDeque::new(), Some(addresses), 0)
 177         }
 178
 179         fn pending_messages(&self) -> &VecDeque<OnionMessage> {
 180                 match self {
 181                         OnionMessageBuffer::ConnectedPeer(pending_messages) => pending_messages,
 182                         OnionMessageBuffer::PendingConnection(pending_messages, _, _) => pending_messages,
 183                 }
 184         }
 185
 186         fn enqueue_message(&mut self, message: OnionMessage) {
 187                 let pending_messages = match self {
 188                         OnionMessageBuffer::ConnectedPeer(pending_messages) => pending_messages,
 189                         OnionMessageBuffer::PendingConnection(pending_messages, _, _) => pending_messages,
 190                 };
 191
 192                 pending_messages.push_back(message);
 193         }
 194
 195         fn dequeue_message(&mut self) -> Option<OnionMessage> {
 196                 let pending_messages = match self {
 197                         OnionMessageBuffer::ConnectedPeer(pending_messages) => pending_messages,
 198                         OnionMessageBuffer::PendingConnection(pending_messages, _, _) => {
 199                                 debug_assert!(false);
 200                                 pending_messages
 201                         },
 202                 };
 203
 204                 pending_messages.pop_front()
 205         }
 206
 207         #[cfg(test)]
 208         fn release_pending_messages(&mut self) -> VecDeque<OnionMessage> {
 209                 let pending_messages = match self {
 210                         OnionMessageBuffer::ConnectedPeer(pending_messages) => pending_messages,
 211                         OnionMessageBuffer::PendingConnection(pending_messages, _, _) => pending_messages,
 212                 };
 213
 214                 core::mem::take(pending_messages)
 215         }
 216
 217         fn mark_connected(&mut self) {
 218                 if let OnionMessageBuffer::PendingConnection(pending_messages, _, _) = self {
 219                         let mut new_pending_messages = VecDeque::new();
 220                         core::mem::swap(pending_messages, &mut new_pending_messages);
 221                         *self = OnionMessageBuffer::ConnectedPeer(new_pending_messages);
 222                 }
 223         }
 224 }
 225
 226 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 227 ///
 228 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 229 /// enqueued for sending.
 230 #[cfg(not(c_bindings))]
 231 pub struct PendingOnionMessage<T: OnionMessageContents> {
 232         /// The message contents to send in an [`OnionMessage`].
 233         pub contents: T,
 234
 235         /// The destination of the message.
 236         pub destination: Destination,
 237
 238         /// A reply path to include in the [`OnionMessage`] for a response.
 239         pub reply_path: Option<BlindedPath>,
 240 }
 241
 242 #[cfg(c_bindings)]
 243 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 244 ///
 245 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 246 /// enqueued for sending.
 247 pub type PendingOnionMessage<T: OnionMessageContents> = (T, Destination, Option<BlindedPath>);
 248
 249 pub(crate) fn new_pending_onion_message<T: OnionMessageContents>(
 250         contents: T, destination: Destination, reply_path: Option<BlindedPath>
 251 ) -> PendingOnionMessage<T> {
 252         #[cfg(not(c_bindings))]
 253         return PendingOnionMessage { contents, destination, reply_path };
 254         #[cfg(c_bindings)]
 255         return (contents, destination, reply_path);
 256 }
 257
 258 /// A trait defining behavior for routing an [`OnionMessage`].
 259 pub trait MessageRouter {
 260         /// Returns a route for sending an [`OnionMessage`] to the given [`Destination`].
 261         fn find_path(
 262                 &self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 263         ) -> Result<OnionMessagePath, ()>;
 264 }
 265
 266 /// A [`MessageRouter`] that can only route to a directly connected [`Destination`].
 267 pub struct DefaultMessageRouter<G: Deref<Target=NetworkGraph<L>>, L: Deref>
 268 where
 269         L::Target: Logger,
 270 {
 271         network_graph: G,
 272 }
 273
 274 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> DefaultMessageRouter<G, L>
 275 where
 276         L::Target: Logger,
 277 {
 278         /// Creates a [`DefaultMessageRouter`] using the given [`NetworkGraph`].
 279         pub fn new(network_graph: G) -> Self {
 280                 Self { network_graph }
 281         }
 282 }
 283
 284 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> MessageRouter for DefaultMessageRouter<G, L>
 285 where
 286         L::Target: Logger,
 287 {
 288         fn find_path(
 289                 &self, _sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 290         ) -> Result<OnionMessagePath, ()> {
 291                 let first_node = destination.first_node();
 292                 if peers.contains(&first_node) {
 293                         Ok(OnionMessagePath { intermediate_nodes: vec![], destination, addresses: None })
 294                 } else {
 295                         let network_graph = self.network_graph.deref().read_only();
 296                         let node_announcement = network_graph
 297                                 .node(&NodeId::from_pubkey(&first_node))
 298                                 .and_then(|node_info| node_info.announcement_info.as_ref())
 299                                 .and_then(|announcement_info| announcement_info.announcement_message.as_ref())
 300                                 .map(|node_announcement| &node_announcement.contents);
 301
 302                         match node_announcement {
 303                                 Some(node_announcement) if node_announcement.features.supports_onion_messages() => {
 304                                         let addresses = Some(node_announcement.addresses.clone());
 305                                         Ok(OnionMessagePath { intermediate_nodes: vec![], destination, addresses })
 306                                 },
 307                                 _ => Err(()),
 308                         }
 309                 }
 310         }
 311 }
 312
 313 /// A path for sending an [`OnionMessage`].
 314 #[derive(Clone)]
 315 pub struct OnionMessagePath {
 316         /// Nodes on the path between the sender and the destination.
 317         pub intermediate_nodes: Vec<PublicKey>,
 318
 319         /// The recipient of the message.
 320         pub destination: Destination,
 321
 322         /// Addresses that may be used to connect to [`OnionMessagePath::first_node`].
 323         ///
 324         /// Only needs to be set if a connection to the node is required. [`OnionMessenger`] may use
 325         /// this to initiate such a connection.
 326         pub addresses: Option<Vec<SocketAddress>>,
 327 }
 328
 329 impl OnionMessagePath {
 330         /// Returns the first node in the path.
 331         pub fn first_node(&self) -> PublicKey {
 332                 self.intermediate_nodes
 333                         .first()
 334                         .copied()
 335                         .unwrap_or_else(|| self.destination.first_node())
 336         }
 337 }
 338
 339 /// The destination of an onion message.
 340 #[derive(Clone)]
 341 pub enum Destination {
 342         /// We're sending this onion message to a node.
 343         Node(PublicKey),
 344         /// We're sending this onion message to a blinded path.
 345         BlindedPath(BlindedPath),
 346 }
 347
 348 impl Destination {
 349         pub(super) fn num_hops(&self) -> usize {
 350                 match self {
 351                         Destination::Node(_) => 1,
 352                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
 353                 }
 354         }
 355
 356         fn first_node(&self) -> PublicKey {
 357                 match self {
 358                         Destination::Node(node_id) => *node_id,
 359                         Destination::BlindedPath(BlindedPath { introduction_node_id: node_id, .. }) => *node_id,
 360                 }
 361         }
 362 }
 363
 364 /// Result of successfully [sending an onion message].
 365 ///
 366 /// [sending an onion message]: OnionMessenger::send_onion_message
 367 #[derive(Debug, PartialEq, Eq)]
 368 pub enum SendSuccess {
 369         /// The message was buffered and will be sent once it is processed by
 370         /// [`OnionMessageHandler::next_onion_message_for_peer`].
 371         Buffered,
 372         /// The message was buffered and will be sent once the node is connected as a peer and it is
 373         /// processed by [`OnionMessageHandler::next_onion_message_for_peer`].
 374         BufferedAwaitingConnection(PublicKey),
 375 }
 376
 377 /// Errors that may occur when [sending an onion message].
 378 ///
 379 /// [sending an onion message]: OnionMessenger::send_onion_message
 380 #[derive(Debug, PartialEq, Eq)]
 381 pub enum SendError {
 382         /// Errored computing onion message packet keys.
 383         Secp256k1(secp256k1::Error),
 384         /// Because implementations such as Eclair will drop onion messages where the message packet
 385         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
 386         TooBigPacket,
 387         /// The provided [`Destination`] was an invalid [`BlindedPath`] due to not having any blinded
 388         /// hops.
 389         TooFewBlindedHops,
 390         /// The first hop is not a peer and doesn't have a known [`SocketAddress`].
 391         InvalidFirstHop(PublicKey),
 392         /// A path from the sender to the destination could not be found by the [`MessageRouter`].
 393         PathNotFound,
 394         /// Onion message contents must have a TLV type >= 64.
 395         InvalidMessage,
 396         /// Our next-hop peer's buffer was full or our total outbound buffer was full.
 397         BufferFull,
 398         /// Failed to retrieve our node id from the provided [`NodeSigner`].
 399         ///
 400         /// [`NodeSigner`]: crate::sign::NodeSigner
 401         GetNodeIdFailed,
 402         /// We attempted to send to a blinded path where we are the introduction node, and failed to
 403         /// advance the blinded path to make the second hop the new introduction node. Either
 404         /// [`NodeSigner::ecdh`] failed, we failed to tweak the current blinding point to get the
 405         /// new blinding point, or we were attempting to send to ourselves.
 406         BlindedPathAdvanceFailed,
 407 }
 408
 409 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
 410 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
 411 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
 412 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
 413 /// message types.
 414 ///
 415 /// See [`OnionMessenger`] for example usage.
 416 ///
 417 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
 418 /// [`CustomMessage`]: Self::CustomMessage
 419 pub trait CustomOnionMessageHandler {
 420         /// The message known to the handler. To support multiple message types, you may want to make this
 421         /// an enum with a variant for each supported message.
 422         type CustomMessage: OnionMessageContents;
 423
 424         /// Called with the custom message that was received, returning a response to send, if any.
 425         ///
 426         /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
 427         fn handle_custom_message(&self, msg: Self::CustomMessage) -> Option<Self::CustomMessage>;
 428
 429         /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
 430         /// message type is unknown.
 431         fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 432
 433         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 434         ///
 435         /// Typically, this is used for messages initiating a message flow rather than in response to
 436         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 437         #[cfg(not(c_bindings))]
 438         fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
 439
 440         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 441         ///
 442         /// Typically, this is used for messages initiating a message flow rather than in response to
 443         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 444         #[cfg(c_bindings)]
 445         fn release_pending_custom_messages(&self) -> Vec<(Self::CustomMessage, Destination, Option<BlindedPath>)>;
 446 }
 447
 448 /// A processed incoming onion message, containing either a Forward (another onion message)
 449 /// or a Receive payload with decrypted contents.
 450 pub enum PeeledOnion<T: OnionMessageContents> {
 451         /// Forwarded onion, with the next node id and a new onion
 452         Forward(PublicKey, OnionMessage),
 453         /// Received onion message, with decrypted contents, path_id, and reply path
 454         Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
 455 }
 456
 457 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 458 /// `path`.
 459 ///
 460 /// Returns both the node id of the peer to send the message to and the message itself.
 461 pub fn create_onion_message<ES: Deref, NS: Deref, T: OnionMessageContents>(
 462         entropy_source: &ES, node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>,
 463         path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 464 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 465 where
 466         ES::Target: EntropySource,
 467         NS::Target: NodeSigner,
 468 {
 469         let OnionMessagePath { intermediate_nodes, mut destination, addresses } = path;
 470         if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
 471                 if blinded_hops.is_empty() {
 472                         return Err(SendError::TooFewBlindedHops);
 473                 }
 474         }
 475
 476         if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
 477
 478         // If we are sending straight to a blinded path and we are the introduction node, we need to
 479         // advance the blinded path by 1 hop so the second hop is the new introduction node.
 480         if intermediate_nodes.len() == 0 {
 481                 if let Destination::BlindedPath(ref mut blinded_path) = destination {
 482                         let our_node_id = node_signer.get_node_id(Recipient::Node)
 483                                 .map_err(|()| SendError::GetNodeIdFailed)?;
 484                         if blinded_path.introduction_node_id == our_node_id {
 485                                 advance_path_by_one(blinded_path, node_signer, &secp_ctx)
 486                                         .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
 487                         }
 488                 }
 489         }
 490
 491         let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 492         let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 493         let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
 494                 (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
 495         } else {
 496                 match destination {
 497                         Destination::Node(pk) => (pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
 498                         Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
 499                                 (introduction_node_id, blinding_point),
 500                 }
 501         };
 502         let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 503                 &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret)
 504                 .map_err(|e| SendError::Secp256k1(e))?;
 505
 506         let prng_seed = entropy_source.get_secure_random_bytes();
 507         let onion_routing_packet = construct_onion_message_packet(
 508                 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
 509
 510         let message = OnionMessage { blinding_point, onion_routing_packet };
 511         Ok((first_node_id, message, addresses))
 512 }
 513
 514 /// Decode one layer of an incoming [`OnionMessage`].
 515 ///
 516 /// Returns either the next layer of the onion for forwarding or the decrypted content for the
 517 /// receiver.
 518 pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
 519         msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
 520         custom_handler: CMH,
 521 ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
 522 where
 523         NS::Target: NodeSigner,
 524         L::Target: Logger,
 525         CMH::Target: CustomOnionMessageHandler,
 526 {
 527         let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
 528                 Ok(ss) => ss,
 529                 Err(e) =>  {
 530                         log_error!(logger, "Failed to retrieve node secret: {:?}", e);
 531                         return Err(());
 532                 }
 533         };
 534         let onion_decode_ss = {
 535                 let blinding_factor = {
 536                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 537                         hmac.input(control_tlvs_ss.as_ref());
 538                         Hmac::from_engine(hmac).to_byte_array()
 539                 };
 540                 match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 541                         Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
 542                 {
 543                         Ok(ss) => ss.secret_bytes(),
 544                         Err(()) => {
 545                                 log_trace!(logger, "Failed to compute onion packet shared secret");
 546                                 return Err(());
 547                         }
 548                 }
 549         };
 550         match onion_utils::decode_next_untagged_hop(
 551                 onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 552                 (control_tlvs_ss, custom_handler.deref(), logger.deref())
 553         ) {
 554                 Ok((Payload::Receive::<ParsedOnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>> {
 555                         message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
 556                 }, None)) => {
 557                         Ok(PeeledOnion::Receive(message, path_id, reply_path))
 558                 },
 559                 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 560                         next_node_id, next_blinding_override
 561                 })), Some((next_hop_hmac, new_packet_bytes)))) => {
 562                         // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 563                         // blinded hop and this onion message is destined for us. In this situation, we should keep
 564                         // unwrapping the onion layers to get to the final payload. Since we don't have the option
 565                         // of creating blinded paths with dummy hops currently, we should be ok to not handle this
 566                         // for now.
 567                         let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 568                                 Ok(pk) => pk,
 569                                 Err(e) => {
 570                                         log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
 571                                         return Err(())
 572                                 }
 573                         };
 574                         let outgoing_packet = Packet {
 575                                 version: 0,
 576                                 public_key: new_pubkey,
 577                                 hop_data: new_packet_bytes,
 578                                 hmac: next_hop_hmac,
 579                         };
 580                         let onion_message = OnionMessage {
 581                                 blinding_point: match next_blinding_override {
 582                                         Some(blinding_point) => blinding_point,
 583                                         None => {
 584                                                 match onion_utils::next_hop_pubkey(
 585                                                         &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
 586                                                 ) {
 587                                                         Ok(bp) => bp,
 588                                                         Err(e) => {
 589                                                                 log_trace!(logger, "Failed to compute next blinding point: {}", e);
 590                                                                 return Err(())
 591                                                         }
 592                                                 }
 593                                         }
 594                                 },
 595                                 onion_routing_packet: outgoing_packet,
 596                         };
 597
 598                         Ok(PeeledOnion::Forward(next_node_id, onion_message))
 599                 },
 600                 Err(e) => {
 601                         log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
 602                         Err(())
 603                 },
 604                 _ => {
 605                         log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 606                         Err(())
 607                 },
 608         }
 609 }
 610
 611 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 612 OnionMessenger<ES, NS, L, MR, OMH, CMH>
 613 where
 614         ES::Target: EntropySource,
 615         NS::Target: NodeSigner,
 616         L::Target: Logger,
 617         MR::Target: MessageRouter,
 618         OMH::Target: OffersMessageHandler,
 619         CMH::Target: CustomOnionMessageHandler,
 620 {
 621         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
 622         /// their respective handlers.
 623         pub fn new(
 624                 entropy_source: ES, node_signer: NS, logger: L, message_router: MR, offers_handler: OMH,
 625                 custom_handler: CMH
 626         ) -> Self {
 627                 let mut secp_ctx = Secp256k1::new();
 628                 secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 629                 OnionMessenger {
 630                         entropy_source,
 631                         node_signer,
 632                         message_buffers: Mutex::new(HashMap::new()),
 633                         secp_ctx,
 634                         logger,
 635                         message_router,
 636                         offers_handler,
 637                         custom_handler,
 638                 }
 639         }
 640
 641         /// Sends an [`OnionMessage`] with the given `contents` to `destination`.
 642         ///
 643         /// See [`OnionMessenger`] for example usage.
 644         pub fn send_onion_message<T: OnionMessageContents>(
 645                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>
 646         ) -> Result<SendSuccess, SendError> {
 647                 self.find_path_and_enqueue_onion_message(
 648                         contents, destination, reply_path, format_args!("")
 649                 )
 650         }
 651
 652         fn find_path_and_enqueue_onion_message<T: OnionMessageContents>(
 653                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>,
 654                 log_suffix: fmt::Arguments
 655         ) -> Result<SendSuccess, SendError> {
 656                 let result = self.find_path(destination)
 657                         .and_then(|path| self.enqueue_onion_message(path, contents, reply_path, log_suffix));
 658
 659                 match result.as_ref() {
 660                         Err(SendError::GetNodeIdFailed) => {
 661                                 log_warn!(self.logger, "Unable to retrieve node id {}", log_suffix);
 662                         },
 663                         Err(SendError::PathNotFound) => {
 664                                 log_trace!(self.logger, "Failed to find path {}", log_suffix);
 665                         },
 666                         Err(e) => {
 667                                 log_trace!(self.logger, "Failed sending onion message {}: {:?}", log_suffix, e);
 668                         },
 669                         Ok(SendSuccess::Buffered) => {
 670                                 log_trace!(self.logger, "Buffered onion message {}", log_suffix);
 671                         },
 672                         Ok(SendSuccess::BufferedAwaitingConnection(node_id)) => {
 673                                 log_trace!(
 674                                         self.logger, "Buffered onion message waiting on peer connection {}: {:?}",
 675                                         log_suffix, node_id
 676                                 );
 677                         },
 678                 }
 679
 680                 result
 681         }
 682
 683         fn find_path(&self, destination: Destination) -> Result<OnionMessagePath, SendError> {
 684                 let sender = self.node_signer
 685                         .get_node_id(Recipient::Node)
 686                         .map_err(|_| SendError::GetNodeIdFailed)?;
 687
 688                 let peers = self.message_buffers.lock().unwrap()
 689                         .iter()
 690                         .filter(|(_, buffer)| matches!(buffer, OnionMessageBuffer::ConnectedPeer(_)))
 691                         .map(|(node_id, _)| *node_id)
 692                         .collect();
 693
 694                 self.message_router
 695                         .find_path(sender, peers, destination)
 696                         .map_err(|_| SendError::PathNotFound)
 697         }
 698
 699         fn enqueue_onion_message<T: OnionMessageContents>(
 700                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 701                 log_suffix: fmt::Arguments
 702         ) -> Result<SendSuccess, SendError> {
 703                 log_trace!(self.logger, "Constructing onion message {}: {:?}", log_suffix, contents);
 704
 705                 let (first_node_id, onion_message, addresses) = create_onion_message(
 706                         &self.entropy_source, &self.node_signer, &self.secp_ctx, path, contents, reply_path
 707                 )?;
 708
 709                 let mut message_buffers = self.message_buffers.lock().unwrap();
 710                 if outbound_buffer_full(&first_node_id, &message_buffers) {
 711                         return Err(SendError::BufferFull);
 712                 }
 713
 714                 match message_buffers.entry(first_node_id) {
 715                         hash_map::Entry::Vacant(e) => match addresses {
 716                                 None => Err(SendError::InvalidFirstHop(first_node_id)),
 717                                 Some(addresses) => {
 718                                         e.insert(OnionMessageBuffer::pending_connection(addresses))
 719                                                 .enqueue_message(onion_message);
 720                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 721                                 },
 722                         },
 723                         hash_map::Entry::Occupied(mut e) => {
 724                                 e.get_mut().enqueue_message(onion_message);
 725                                 Ok(SendSuccess::Buffered)
 726                         },
 727                 }
 728         }
 729
 730         #[cfg(test)]
 731         pub(super) fn send_onion_message_using_path<T: OnionMessageContents>(
 732                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
 733         ) -> Result<SendSuccess, SendError> {
 734                 self.enqueue_onion_message(path, contents, reply_path, format_args!(""))
 735         }
 736
 737         fn handle_onion_message_response<T: OnionMessageContents>(
 738                 &self, response: Option<T>, reply_path: Option<BlindedPath>, log_suffix: fmt::Arguments
 739         ) {
 740                 if let Some(response) = response {
 741                         match reply_path {
 742                                 Some(reply_path) => {
 743                                         let _ = self.find_path_and_enqueue_onion_message(
 744                                                 response, Destination::BlindedPath(reply_path), None, log_suffix
 745                                         );
 746                                 },
 747                                 None => {
 748                                         log_trace!(self.logger, "Missing reply path {}", log_suffix);
 749                                 },
 750                         }
 751                 }
 752         }
 753
 754         #[cfg(test)]
 755         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<OnionMessage>> {
 756                 let mut message_buffers = self.message_buffers.lock().unwrap();
 757                 let mut msgs = HashMap::new();
 758                 // We don't want to disconnect the peers by removing them entirely from the original map, so we
 759                 // release the pending message buffers individually.
 760                 for (peer_node_id, buffer) in &mut *message_buffers {
 761                         msgs.insert(*peer_node_id, buffer.release_pending_messages());
 762                 }
 763                 msgs
 764         }
 765 }
 766
 767 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageBuffer>) -> bool {
 768         const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
 769         const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
 770         let mut total_buffered_bytes = 0;
 771         let mut peer_buffered_bytes = 0;
 772         for (pk, peer_buf) in buffer {
 773                 for om in peer_buf.pending_messages() {
 774                         let om_len = om.serialized_length();
 775                         if pk == peer_node_id {
 776                                 peer_buffered_bytes += om_len;
 777                         }
 778                         total_buffered_bytes += om_len;
 779
 780                         if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
 781                                 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
 782                         {
 783                                 return true
 784                         }
 785                 }
 786         }
 787         false
 788 }
 789
 790 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> EventsProvider
 791 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 792 where
 793         ES::Target: EntropySource,
 794         NS::Target: NodeSigner,
 795         L::Target: Logger,
 796         MR::Target: MessageRouter,
 797         OMH::Target: OffersMessageHandler,
 798         CMH::Target: CustomOnionMessageHandler,
 799 {
 800         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
 801                 for (node_id, recipient) in self.message_buffers.lock().unwrap().iter_mut() {
 802                         if let OnionMessageBuffer::PendingConnection(_, addresses, _) = recipient {
 803                                 if let Some(addresses) = addresses.take() {
 804                                         handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
 805                                 }
 806                         }
 807                 }
 808         }
 809 }
 810
 811 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> OnionMessageHandler
 812 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 813 where
 814         ES::Target: EntropySource,
 815         NS::Target: NodeSigner,
 816         L::Target: Logger,
 817         MR::Target: MessageRouter,
 818         OMH::Target: OffersMessageHandler,
 819         CMH::Target: CustomOnionMessageHandler,
 820 {
 821         fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &OnionMessage) {
 822                 match peel_onion_message(
 823                         msg, &self.secp_ctx, &*self.node_signer, &*self.logger, &*self.custom_handler
 824                 ) {
 825                         Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
 826                                 log_trace!(
 827                                         self.logger,
 828                                    "Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
 829                                         path_id, if reply_path.is_some() { "a" } else { "no" }, message);
 830
 831                                 match message {
 832                                         ParsedOnionMessageContents::Offers(msg) => {
 833                                                 let response = self.offers_handler.handle_message(msg);
 834                                                 self.handle_onion_message_response(
 835                                                         response, reply_path, format_args!(
 836                                                                 "when responding to Offers onion message with path_id {:02x?}",
 837                                                                 path_id
 838                                                         )
 839                                                 );
 840                                         },
 841                                         ParsedOnionMessageContents::Custom(msg) => {
 842                                                 let response = self.custom_handler.handle_custom_message(msg);
 843                                                 self.handle_onion_message_response(
 844                                                         response, reply_path, format_args!(
 845                                                                 "when responding to Custom onion message with path_id {:02x?}",
 846                                                                 path_id
 847                                                         )
 848                                                 );
 849                                         },
 850                                 }
 851                         },
 852                         Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
 853                                 let mut message_buffers = self.message_buffers.lock().unwrap();
 854                                 if outbound_buffer_full(&next_node_id, &message_buffers) {
 855                                         log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
 856                                         return
 857                                 }
 858
 859                                 #[cfg(fuzzing)]
 860                                 message_buffers
 861                                         .entry(next_node_id)
 862                                         .or_insert_with(|| OnionMessageBuffer::ConnectedPeer(VecDeque::new()));
 863
 864                                 match message_buffers.entry(next_node_id) {
 865                                         hash_map::Entry::Occupied(mut e) if matches!(
 866                                                 e.get(), OnionMessageBuffer::ConnectedPeer(..)
 867                                         ) => {
 868                                                 e.get_mut().enqueue_message(onion_message);
 869                                                 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
 870                                         },
 871                                         _ => {
 872                                                 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
 873                                                 return
 874                                         },
 875                                 }
 876                         },
 877                         Err(e) => {
 878                                 log_error!(self.logger, "Failed to process onion message {:?}", e);
 879                         }
 880                 }
 881         }
 882
 883         fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
 884                 if init.features.supports_onion_messages() {
 885                         self.message_buffers.lock().unwrap()
 886                                 .entry(*their_node_id)
 887                                 .or_insert_with(|| OnionMessageBuffer::ConnectedPeer(VecDeque::new()))
 888                                 .mark_connected();
 889                 } else {
 890                         self.message_buffers.lock().unwrap().remove(their_node_id);
 891                 }
 892
 893                 Ok(())
 894         }
 895
 896         fn peer_disconnected(&self, their_node_id: &PublicKey) {
 897                 match self.message_buffers.lock().unwrap().remove(their_node_id) {
 898                         Some(OnionMessageBuffer::ConnectedPeer(..)) => {},
 899                         _ => debug_assert!(false),
 900                 }
 901         }
 902
 903         fn timer_tick_occurred(&self) {
 904                 const MAX_TIMER_TICKS: usize = 2;
 905                 let mut message_buffers = self.message_buffers.lock().unwrap();
 906
 907                 // Drop any pending recipients since the last call to avoid retaining buffered messages for
 908                 // too long.
 909                 message_buffers.retain(|_, recipient| match recipient {
 910                         OnionMessageBuffer::PendingConnection(_, None, ticks) => *ticks < MAX_TIMER_TICKS,
 911                         OnionMessageBuffer::PendingConnection(_, Some(_), _) => true,
 912                         _ => true,
 913                 });
 914
 915                 // Increment a timer tick for pending recipients so that their buffered messages are dropped
 916                 // at MAX_TIMER_TICKS.
 917                 for recipient in message_buffers.values_mut() {
 918                         if let OnionMessageBuffer::PendingConnection(_, None, ticks) = recipient {
 919                                 *ticks += 1;
 920                         }
 921                 }
 922         }
 923
 924         fn provided_node_features(&self) -> NodeFeatures {
 925                 let mut features = NodeFeatures::empty();
 926                 features.set_onion_messages_optional();
 927                 features
 928         }
 929
 930         fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
 931                 let mut features = InitFeatures::empty();
 932                 features.set_onion_messages_optional();
 933                 features
 934         }
 935
 936         // Before returning any messages to send for the peer, this method will see if any messages were
 937         // enqueued in the handler by users, find a path to the corresponding blinded path's introduction
 938         // node, and then enqueue the message for sending to the first peer in the full path.
 939         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<OnionMessage> {
 940                 // Enqueue any initiating `OffersMessage`s to send.
 941                 for message in self.offers_handler.release_pending_messages() {
 942                         #[cfg(not(c_bindings))]
 943                         let PendingOnionMessage { contents, destination, reply_path } = message;
 944                         #[cfg(c_bindings)]
 945                         let (contents, destination, reply_path) = message;
 946                         let _ = self.find_path_and_enqueue_onion_message(
 947                                 contents, destination, reply_path, format_args!("when sending OffersMessage")
 948                         );
 949                 }
 950
 951                 // Enqueue any initiating `CustomMessage`s to send.
 952                 for message in self.custom_handler.release_pending_custom_messages() {
 953                         #[cfg(not(c_bindings))]
 954                         let PendingOnionMessage { contents, destination, reply_path } = message;
 955                         #[cfg(c_bindings)]
 956                         let (contents, destination, reply_path) = message;
 957                         let _ = self.find_path_and_enqueue_onion_message(
 958                                 contents, destination, reply_path, format_args!("when sending CustomMessage")
 959                         );
 960                 }
 961
 962                 self.message_buffers.lock().unwrap()
 963                         .get_mut(&peer_node_id)
 964                         .and_then(|buffer| buffer.dequeue_message())
 965         }
 966 }
 967
 968 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
 969 // produces
 970 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
 971 /// [`SimpleArcPeerManager`]. See their docs for more details.
 972 ///
 973 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 974 ///
 975 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 976 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
 977 #[cfg(not(c_bindings))]
 978 pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
 979         Arc<KeysManager>,
 980         Arc<KeysManager>,
 981         Arc<L>,
 982         Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>>>,
 983         Arc<SimpleArcChannelManager<M, T, F, L>>,
 984         IgnoringMessageHandler
 985 >;
 986
 987 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
 988 /// [`SimpleRefPeerManager`]. See their docs for more details.
 989 ///
 990 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 991 ///
 992 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
 993 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
 994 #[cfg(not(c_bindings))]
 995 pub type SimpleRefOnionMessenger<
 996         'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, M, T, F, L
 997 > = OnionMessenger<
 998         &'a KeysManager,
 999         &'a KeysManager,
1000         &'b L,
1001         &'i DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L>,
1002         &'j SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1003         IgnoringMessageHandler
1004 >;
1005
1006 /// Construct onion packet payloads and keys for sending an onion message along the given
1007 /// `unblinded_path` to the given `destination`.
1008 fn packet_payloads_and_keys<T: OnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
1009         secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination, message: T,
1010         mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
1011 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
1012         let num_hops = unblinded_path.len() + destination.num_hops();
1013         let mut payloads = Vec::with_capacity(num_hops);
1014         let mut onion_packet_keys = Vec::with_capacity(num_hops);
1015
1016         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedPath(BlindedPath {
1017                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
1018                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
1019         let num_unblinded_hops = num_hops - num_blinded_hops;
1020
1021         let mut unblinded_path_idx = 0;
1022         let mut blinded_path_idx = 0;
1023         let mut prev_control_tlvs_ss = None;
1024         let mut final_control_tlvs = None;
1025         utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), Some(destination), session_priv,
1026                 |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
1027                         if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
1028                                 if let Some(ss) = prev_control_tlvs_ss.take() {
1029                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
1030                                                 ForwardTlvs {
1031                                                         next_node_id: unblinded_pk_opt.unwrap(),
1032                                                         next_blinding_override: None,
1033                                                 }
1034                                         )), ss));
1035                                 }
1036                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1037                                 unblinded_path_idx += 1;
1038                         } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
1039                                 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
1040                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
1041                                                 next_node_id: intro_node_id,
1042                                                 next_blinding_override: Some(blinding_pt),
1043                                         })), control_tlvs_ss));
1044                                 }
1045                         }
1046                         if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
1047                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
1048                                         control_tlvs_ss));
1049                                 blinded_path_idx += 1;
1050                         } else if let Some(encrypted_payload) = enc_payload_opt {
1051                                 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
1052                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1053                         }
1054
1055                         let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
1056                         onion_packet_keys.push(onion_utils::OnionKeys {
1057                                 #[cfg(test)]
1058                                 shared_secret: onion_packet_ss,
1059                                 #[cfg(test)]
1060                                 blinding_factor: [0; 32],
1061                                 ephemeral_pubkey,
1062                                 rho,
1063                                 mu,
1064                         });
1065                 }
1066         )?;
1067
1068         if let Some(control_tlvs) = final_control_tlvs {
1069                 payloads.push((Payload::Receive {
1070                         control_tlvs,
1071                         reply_path: reply_path.take(),
1072                         message,
1073                 }, prev_control_tlvs_ss.unwrap()));
1074         } else {
1075                 payloads.push((Payload::Receive {
1076                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
1077                         reply_path: reply_path.take(),
1078                         message,
1079                 }, prev_control_tlvs_ss.unwrap()));
1080         }
1081
1082         Ok((payloads, onion_packet_keys))
1083 }
1084
1085 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
1086 fn construct_onion_message_packet<T: OnionMessageContents>(payloads: Vec<(Payload<T>, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Result<Packet, ()> {
1087         // Spec rationale:
1088         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
1089         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
1090         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
1091         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
1092         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
1093                 SMALL_PACKET_HOP_DATA_LEN
1094         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
1095                 BIG_PACKET_HOP_DATA_LEN
1096         } else { return Err(()) };
1097
1098         onion_utils::construct_onion_message_packet::<_, _>(
1099                 payloads, onion_keys, prng_seed, hop_data_len)
1100 }