_ 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 pub(super) const MAX_TIMER_TICKS: usize = 2;
  44
  45 /// A sender, receiver and forwarder of [`OnionMessage`]s.
  46 ///
  47 /// # Handling Messages
  48 ///
  49 /// `OnionMessenger` implements [`OnionMessageHandler`], making it responsible for either forwarding
  50 /// messages to peers or delegating to the appropriate handler for the message type. Currently, the
  51 /// available handlers are:
  52 /// * [`OffersMessageHandler`], for responding to [`InvoiceRequest`]s and paying [`Bolt12Invoice`]s
  53 /// * [`CustomOnionMessageHandler`], for handling user-defined message types
  54 ///
  55 /// # Sending Messages
  56 ///
  57 /// [`OnionMessage`]s are sent initially using [`OnionMessenger::send_onion_message`]. When handling
  58 /// a message, the matched handler may return a response message which `OnionMessenger` will send
  59 /// on its behalf.
  60 ///
  61 /// # Example
  62 ///
  63 /// ```
  64 /// # extern crate bitcoin;
  65 /// # use bitcoin::hashes::_export::_core::time::Duration;
  66 /// # use bitcoin::hashes::hex::FromHex;
  67 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
  68 /// # use lightning::blinded_path::BlindedPath;
  69 /// # use lightning::sign::KeysManager;
  70 /// # use lightning::ln::peer_handler::IgnoringMessageHandler;
  71 /// # use lightning::onion_message::{OnionMessageContents, Destination, MessageRouter, OnionMessagePath, OnionMessenger};
  72 /// # use lightning::util::logger::{Logger, Record};
  73 /// # use lightning::util::ser::{Writeable, Writer};
  74 /// # use lightning::io;
  75 /// # use std::sync::Arc;
  76 /// # struct FakeLogger;
  77 /// # impl Logger for FakeLogger {
  78 /// #     fn log(&self, record: Record) { println!("{:?}" , record); }
  79 /// # }
  80 /// # struct FakeMessageRouter {}
  81 /// # impl MessageRouter for FakeMessageRouter {
  82 /// #     fn find_path(&self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination) -> Result<OnionMessagePath, ()> {
  83 /// #         let secp_ctx = Secp256k1::new();
  84 /// #         let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
  85 /// #         let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
  86 /// #         let hop_node_id2 = hop_node_id1;
  87 /// #         Ok(OnionMessagePath {
  88 /// #             intermediate_nodes: vec![hop_node_id1, hop_node_id2],
  89 /// #             destination,
  90 /// #             addresses: None,
  91 /// #         })
  92 /// #     }
  93 /// # }
  94 /// # let seed = [42u8; 32];
  95 /// # let time = Duration::from_secs(123456);
  96 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
  97 /// # let logger = Arc::new(FakeLogger {});
  98 /// # let node_secret = SecretKey::from_slice(&<Vec<u8>>::from_hex("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
  99 /// # let secp_ctx = Secp256k1::new();
 100 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
 101 /// # let (hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1);
 102 /// # let destination_node_id = hop_node_id1;
 103 /// # let message_router = Arc::new(FakeMessageRouter {});
 104 /// # let custom_message_handler = IgnoringMessageHandler {};
 105 /// # let offers_message_handler = IgnoringMessageHandler {};
 106 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
 107 /// // ChannelManager.
 108 /// let onion_messenger = OnionMessenger::new(
 109 ///     &keys_manager, &keys_manager, logger, message_router, &offers_message_handler,
 110 ///     &custom_message_handler
 111 /// );
 112
 113 /// # #[derive(Debug)]
 114 /// # struct YourCustomMessage {}
 115 /// impl Writeable for YourCustomMessage {
 116 ///     fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 117 ///             # Ok(())
 118 ///             // Write your custom onion message to `w`
 119 ///     }
 120 /// }
 121 /// impl OnionMessageContents for YourCustomMessage {
 122 ///     fn tlv_type(&self) -> u64 {
 123 ///             # let your_custom_message_type = 42;
 124 ///             your_custom_message_type
 125 ///     }
 126 /// }
 127 /// // Send a custom onion message to a node id.
 128 /// let destination = Destination::Node(destination_node_id);
 129 /// let reply_path = None;
 130 /// # let message = YourCustomMessage {};
 131 /// onion_messenger.send_onion_message(message, destination, reply_path);
 132 ///
 133 /// // Create a blinded path to yourself, for someone to send an onion message to.
 134 /// # let your_node_id = hop_node_id1;
 135 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
 136 /// let blinded_path = BlindedPath::new_for_message(&hops, &keys_manager, &secp_ctx).unwrap();
 137 ///
 138 /// // Send a custom onion message to a blinded path.
 139 /// let destination = Destination::BlindedPath(blinded_path);
 140 /// let reply_path = None;
 141 /// # let message = YourCustomMessage {};
 142 /// onion_messenger.send_onion_message(message, destination, reply_path);
 143 /// ```
 144 ///
 145 /// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
 146 /// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
 147 pub struct OnionMessenger<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 148 where
 149         ES::Target: EntropySource,
 150         NS::Target: NodeSigner,
 151         L::Target: Logger,
 152         MR::Target: MessageRouter,
 153         OMH::Target: OffersMessageHandler,
 154         CMH::Target: CustomOnionMessageHandler,
 155 {
 156         entropy_source: ES,
 157         node_signer: NS,
 158         logger: L,
 159         message_recipients: Mutex<HashMap<PublicKey, OnionMessageRecipient>>,
 160         secp_ctx: Secp256k1<secp256k1::All>,
 161         message_router: MR,
 162         offers_handler: OMH,
 163         custom_handler: CMH,
 164 }
 165
 166 /// [`OnionMessage`]s buffered to be sent.
 167 enum OnionMessageRecipient {
 168         /// Messages for a node connected as a peer.
 169         ConnectedPeer(VecDeque<OnionMessage>),
 170
 171         /// Messages for a node that is not yet connected, which are dropped after [`MAX_TIMER_TICKS`]
 172         /// and tracked here.
 173         PendingConnection(VecDeque<OnionMessage>, Option<Vec<SocketAddress>>, usize),
 174 }
 175
 176 impl OnionMessageRecipient {
 177         fn pending_connection(addresses: Vec<SocketAddress>) -> Self {
 178                 Self::PendingConnection(VecDeque::new(), Some(addresses), 0)
 179         }
 180
 181         fn pending_messages(&self) -> &VecDeque<OnionMessage> {
 182                 match self {
 183                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 184                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 185                 }
 186         }
 187
 188         fn enqueue_message(&mut self, message: OnionMessage) {
 189                 let pending_messages = match self {
 190                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 191                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 192                 };
 193
 194                 pending_messages.push_back(message);
 195         }
 196
 197         fn dequeue_message(&mut self) -> Option<OnionMessage> {
 198                 let pending_messages = match self {
 199                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 200                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => {
 201                                 debug_assert!(false);
 202                                 pending_messages
 203                         },
 204                 };
 205
 206                 pending_messages.pop_front()
 207         }
 208
 209         #[cfg(test)]
 210         fn release_pending_messages(&mut self) -> VecDeque<OnionMessage> {
 211                 let pending_messages = match self {
 212                         OnionMessageRecipient::ConnectedPeer(pending_messages) => pending_messages,
 213                         OnionMessageRecipient::PendingConnection(pending_messages, _, _) => pending_messages,
 214                 };
 215
 216                 core::mem::take(pending_messages)
 217         }
 218
 219         fn mark_connected(&mut self) {
 220                 if let OnionMessageRecipient::PendingConnection(pending_messages, _, _) = self {
 221                         let mut new_pending_messages = VecDeque::new();
 222                         core::mem::swap(pending_messages, &mut new_pending_messages);
 223                         *self = OnionMessageRecipient::ConnectedPeer(new_pending_messages);
 224                 }
 225         }
 226 }
 227
 228 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 229 ///
 230 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 231 /// enqueued for sending.
 232 #[cfg(not(c_bindings))]
 233 pub struct PendingOnionMessage<T: OnionMessageContents> {
 234         /// The message contents to send in an [`OnionMessage`].
 235         pub contents: T,
 236
 237         /// The destination of the message.
 238         pub destination: Destination,
 239
 240         /// A reply path to include in the [`OnionMessage`] for a response.
 241         pub reply_path: Option<BlindedPath>,
 242 }
 243
 244 #[cfg(c_bindings)]
 245 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 246 ///
 247 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 248 /// enqueued for sending.
 249 pub type PendingOnionMessage<T: OnionMessageContents> = (T, Destination, Option<BlindedPath>);
 250
 251 pub(crate) fn new_pending_onion_message<T: OnionMessageContents>(
 252         contents: T, destination: Destination, reply_path: Option<BlindedPath>
 253 ) -> PendingOnionMessage<T> {
 254         #[cfg(not(c_bindings))]
 255         return PendingOnionMessage { contents, destination, reply_path };
 256         #[cfg(c_bindings)]
 257         return (contents, destination, reply_path);
 258 }
 259
 260 /// A trait defining behavior for routing an [`OnionMessage`].
 261 pub trait MessageRouter {
 262         /// Returns a route for sending an [`OnionMessage`] to the given [`Destination`].
 263         fn find_path(
 264                 &self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 265         ) -> Result<OnionMessagePath, ()>;
 266 }
 267
 268 /// A [`MessageRouter`] that can only route to a directly connected [`Destination`].
 269 pub struct DefaultMessageRouter<G: Deref<Target=NetworkGraph<L>>, L: Deref>
 270 where
 271         L::Target: Logger,
 272 {
 273         network_graph: G,
 274 }
 275
 276 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> DefaultMessageRouter<G, L>
 277 where
 278         L::Target: Logger,
 279 {
 280         /// Creates a [`DefaultMessageRouter`] using the given [`NetworkGraph`].
 281         pub fn new(network_graph: G) -> Self {
 282                 Self { network_graph }
 283         }
 284 }
 285
 286 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> MessageRouter for DefaultMessageRouter<G, L>
 287 where
 288         L::Target: Logger,
 289 {
 290         fn find_path(
 291                 &self, _sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 292         ) -> Result<OnionMessagePath, ()> {
 293                 let first_node = destination.first_node();
 294                 if peers.contains(&first_node) {
 295                         Ok(OnionMessagePath { intermediate_nodes: vec![], destination, addresses: None })
 296                 } else {
 297                         let network_graph = self.network_graph.deref().read_only();
 298                         let node_announcement = network_graph
 299                                 .node(&NodeId::from_pubkey(&first_node))
 300                                 .and_then(|node_info| node_info.announcement_info.as_ref())
 301                                 .and_then(|announcement_info| announcement_info.announcement_message.as_ref())
 302                                 .map(|node_announcement| &node_announcement.contents);
 303
 304                         match node_announcement {
 305                                 Some(node_announcement) if node_announcement.features.supports_onion_messages() => {
 306                                         let addresses = Some(node_announcement.addresses.clone());
 307                                         Ok(OnionMessagePath { intermediate_nodes: vec![], destination, addresses })
 308                                 },
 309                                 _ => Err(()),
 310                         }
 311                 }
 312         }
 313 }
 314
 315 /// A path for sending an [`OnionMessage`].
 316 #[derive(Clone)]
 317 pub struct OnionMessagePath {
 318         /// Nodes on the path between the sender and the destination.
 319         pub intermediate_nodes: Vec<PublicKey>,
 320
 321         /// The recipient of the message.
 322         pub destination: Destination,
 323
 324         /// Addresses that may be used to connect to [`OnionMessagePath::first_node`].
 325         ///
 326         /// Only needs to be set if a connection to the node is required. [`OnionMessenger`] may use
 327         /// this to initiate such a connection.
 328         pub addresses: Option<Vec<SocketAddress>>,
 329 }
 330
 331 impl OnionMessagePath {
 332         /// Returns the first node in the path.
 333         pub fn first_node(&self) -> PublicKey {
 334                 self.intermediate_nodes
 335                         .first()
 336                         .copied()
 337                         .unwrap_or_else(|| self.destination.first_node())
 338         }
 339 }
 340
 341 /// The destination of an onion message.
 342 #[derive(Clone)]
 343 pub enum Destination {
 344         /// We're sending this onion message to a node.
 345         Node(PublicKey),
 346         /// We're sending this onion message to a blinded path.
 347         BlindedPath(BlindedPath),
 348 }
 349
 350 impl Destination {
 351         pub(super) fn num_hops(&self) -> usize {
 352                 match self {
 353                         Destination::Node(_) => 1,
 354                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
 355                 }
 356         }
 357
 358         fn first_node(&self) -> PublicKey {
 359                 match self {
 360                         Destination::Node(node_id) => *node_id,
 361                         Destination::BlindedPath(BlindedPath { introduction_node_id: node_id, .. }) => *node_id,
 362                 }
 363         }
 364 }
 365
 366 /// Result of successfully [sending an onion message].
 367 ///
 368 /// [sending an onion message]: OnionMessenger::send_onion_message
 369 #[derive(Debug, PartialEq, Eq)]
 370 pub enum SendSuccess {
 371         /// The message was buffered and will be sent once it is processed by
 372         /// [`OnionMessageHandler::next_onion_message_for_peer`].
 373         Buffered,
 374         /// The message was buffered and will be sent once the node is connected as a peer and it is
 375         /// processed by [`OnionMessageHandler::next_onion_message_for_peer`].
 376         BufferedAwaitingConnection(PublicKey),
 377 }
 378
 379 /// Errors that may occur when [sending an onion message].
 380 ///
 381 /// [sending an onion message]: OnionMessenger::send_onion_message
 382 #[derive(Debug, PartialEq, Eq)]
 383 pub enum SendError {
 384         /// Errored computing onion message packet keys.
 385         Secp256k1(secp256k1::Error),
 386         /// Because implementations such as Eclair will drop onion messages where the message packet
 387         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
 388         TooBigPacket,
 389         /// The provided [`Destination`] was an invalid [`BlindedPath`] due to not having any blinded
 390         /// hops.
 391         TooFewBlindedHops,
 392         /// The first hop is not a peer and doesn't have a known [`SocketAddress`].
 393         InvalidFirstHop(PublicKey),
 394         /// A path from the sender to the destination could not be found by the [`MessageRouter`].
 395         PathNotFound,
 396         /// Onion message contents must have a TLV type >= 64.
 397         InvalidMessage,
 398         /// Our next-hop peer's buffer was full or our total outbound buffer was full.
 399         BufferFull,
 400         /// Failed to retrieve our node id from the provided [`NodeSigner`].
 401         ///
 402         /// [`NodeSigner`]: crate::sign::NodeSigner
 403         GetNodeIdFailed,
 404         /// We attempted to send to a blinded path where we are the introduction node, and failed to
 405         /// advance the blinded path to make the second hop the new introduction node. Either
 406         /// [`NodeSigner::ecdh`] failed, we failed to tweak the current blinding point to get the
 407         /// new blinding point, or we were attempting to send to ourselves.
 408         BlindedPathAdvanceFailed,
 409 }
 410
 411 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
 412 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
 413 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
 414 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
 415 /// message types.
 416 ///
 417 /// See [`OnionMessenger`] for example usage.
 418 ///
 419 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
 420 /// [`CustomMessage`]: Self::CustomMessage
 421 pub trait CustomOnionMessageHandler {
 422         /// The message known to the handler. To support multiple message types, you may want to make this
 423         /// an enum with a variant for each supported message.
 424         type CustomMessage: OnionMessageContents;
 425
 426         /// Called with the custom message that was received, returning a response to send, if any.
 427         ///
 428         /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
 429         fn handle_custom_message(&self, msg: Self::CustomMessage) -> Option<Self::CustomMessage>;
 430
 431         /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
 432         /// message type is unknown.
 433         fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 434
 435         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 436         ///
 437         /// Typically, this is used for messages initiating a message flow rather than in response to
 438         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 439         #[cfg(not(c_bindings))]
 440         fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
 441
 442         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 443         ///
 444         /// Typically, this is used for messages initiating a message flow rather than in response to
 445         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 446         #[cfg(c_bindings)]
 447         fn release_pending_custom_messages(&self) -> Vec<(Self::CustomMessage, Destination, Option<BlindedPath>)>;
 448 }
 449
 450 /// A processed incoming onion message, containing either a Forward (another onion message)
 451 /// or a Receive payload with decrypted contents.
 452 pub enum PeeledOnion<T: OnionMessageContents> {
 453         /// Forwarded onion, with the next node id and a new onion
 454         Forward(PublicKey, OnionMessage),
 455         /// Received onion message, with decrypted contents, path_id, and reply path
 456         Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
 457 }
 458
 459 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 460 /// `path`.
 461 ///
 462 /// Returns the node id of the peer to send the message to, the message itself, and any addresses
 463 /// need to connect to the first node.
 464 pub fn create_onion_message<ES: Deref, NS: Deref, T: OnionMessageContents>(
 465         entropy_source: &ES, node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>,
 466         path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 467 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 468 where
 469         ES::Target: EntropySource,
 470         NS::Target: NodeSigner,
 471 {
 472         let OnionMessagePath { intermediate_nodes, mut destination, addresses } = path;
 473         if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
 474                 if blinded_hops.is_empty() {
 475                         return Err(SendError::TooFewBlindedHops);
 476                 }
 477         }
 478
 479         if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
 480
 481         // If we are sending straight to a blinded path and we are the introduction node, we need to
 482         // advance the blinded path by 1 hop so the second hop is the new introduction node.
 483         if intermediate_nodes.len() == 0 {
 484                 if let Destination::BlindedPath(ref mut blinded_path) = destination {
 485                         let our_node_id = node_signer.get_node_id(Recipient::Node)
 486                                 .map_err(|()| SendError::GetNodeIdFailed)?;
 487                         if blinded_path.introduction_node_id == our_node_id {
 488                                 advance_path_by_one(blinded_path, node_signer, &secp_ctx)
 489                                         .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
 490                         }
 491                 }
 492         }
 493
 494         let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 495         let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 496         let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
 497                 (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
 498         } else {
 499                 match destination {
 500                         Destination::Node(pk) => (pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
 501                         Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
 502                                 (introduction_node_id, blinding_point),
 503                 }
 504         };
 505         let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 506                 &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret)
 507                 .map_err(|e| SendError::Secp256k1(e))?;
 508
 509         let prng_seed = entropy_source.get_secure_random_bytes();
 510         let onion_routing_packet = construct_onion_message_packet(
 511                 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
 512
 513         let message = OnionMessage { blinding_point, onion_routing_packet };
 514         Ok((first_node_id, message, addresses))
 515 }
 516
 517 /// Decode one layer of an incoming [`OnionMessage`].
 518 ///
 519 /// Returns either the next layer of the onion for forwarding or the decrypted content for the
 520 /// receiver.
 521 pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
 522         msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
 523         custom_handler: CMH,
 524 ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
 525 where
 526         NS::Target: NodeSigner,
 527         L::Target: Logger,
 528         CMH::Target: CustomOnionMessageHandler,
 529 {
 530         let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
 531                 Ok(ss) => ss,
 532                 Err(e) =>  {
 533                         log_error!(logger, "Failed to retrieve node secret: {:?}", e);
 534                         return Err(());
 535                 }
 536         };
 537         let onion_decode_ss = {
 538                 let blinding_factor = {
 539                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 540                         hmac.input(control_tlvs_ss.as_ref());
 541                         Hmac::from_engine(hmac).to_byte_array()
 542                 };
 543                 match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 544                         Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
 545                 {
 546                         Ok(ss) => ss.secret_bytes(),
 547                         Err(()) => {
 548                                 log_trace!(logger, "Failed to compute onion packet shared secret");
 549                                 return Err(());
 550                         }
 551                 }
 552         };
 553         match onion_utils::decode_next_untagged_hop(
 554                 onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 555                 (control_tlvs_ss, custom_handler.deref(), logger.deref())
 556         ) {
 557                 Ok((Payload::Receive::<ParsedOnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>> {
 558                         message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
 559                 }, None)) => {
 560                         Ok(PeeledOnion::Receive(message, path_id, reply_path))
 561                 },
 562                 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 563                         next_node_id, next_blinding_override
 564                 })), Some((next_hop_hmac, new_packet_bytes)))) => {
 565                         // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 566                         // blinded hop and this onion message is destined for us. In this situation, we should keep
 567                         // unwrapping the onion layers to get to the final payload. Since we don't have the option
 568                         // of creating blinded paths with dummy hops currently, we should be ok to not handle this
 569                         // for now.
 570                         let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 571                                 Ok(pk) => pk,
 572                                 Err(e) => {
 573                                         log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
 574                                         return Err(())
 575                                 }
 576                         };
 577                         let outgoing_packet = Packet {
 578                                 version: 0,
 579                                 public_key: new_pubkey,
 580                                 hop_data: new_packet_bytes,
 581                                 hmac: next_hop_hmac,
 582                         };
 583                         let onion_message = OnionMessage {
 584                                 blinding_point: match next_blinding_override {
 585                                         Some(blinding_point) => blinding_point,
 586                                         None => {
 587                                                 match onion_utils::next_hop_pubkey(
 588                                                         &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
 589                                                 ) {
 590                                                         Ok(bp) => bp,
 591                                                         Err(e) => {
 592                                                                 log_trace!(logger, "Failed to compute next blinding point: {}", e);
 593                                                                 return Err(())
 594                                                         }
 595                                                 }
 596                                         }
 597                                 },
 598                                 onion_routing_packet: outgoing_packet,
 599                         };
 600
 601                         Ok(PeeledOnion::Forward(next_node_id, onion_message))
 602                 },
 603                 Err(e) => {
 604                         log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
 605                         Err(())
 606                 },
 607                 _ => {
 608                         log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 609                         Err(())
 610                 },
 611         }
 612 }
 613
 614 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 615 OnionMessenger<ES, NS, L, MR, OMH, CMH>
 616 where
 617         ES::Target: EntropySource,
 618         NS::Target: NodeSigner,
 619         L::Target: Logger,
 620         MR::Target: MessageRouter,
 621         OMH::Target: OffersMessageHandler,
 622         CMH::Target: CustomOnionMessageHandler,
 623 {
 624         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
 625         /// their respective handlers.
 626         pub fn new(
 627                 entropy_source: ES, node_signer: NS, logger: L, message_router: MR, offers_handler: OMH,
 628                 custom_handler: CMH
 629         ) -> Self {
 630                 let mut secp_ctx = Secp256k1::new();
 631                 secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 632                 OnionMessenger {
 633                         entropy_source,
 634                         node_signer,
 635                         message_recipients: Mutex::new(HashMap::new()),
 636                         secp_ctx,
 637                         logger,
 638                         message_router,
 639                         offers_handler,
 640                         custom_handler,
 641                 }
 642         }
 643
 644         /// Sends an [`OnionMessage`] with the given `contents` to `destination`.
 645         ///
 646         /// See [`OnionMessenger`] for example usage.
 647         pub fn send_onion_message<T: OnionMessageContents>(
 648                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>
 649         ) -> Result<SendSuccess, SendError> {
 650                 self.find_path_and_enqueue_onion_message(
 651                         contents, destination, reply_path, format_args!("")
 652                 )
 653         }
 654
 655         fn find_path_and_enqueue_onion_message<T: OnionMessageContents>(
 656                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>,
 657                 log_suffix: fmt::Arguments
 658         ) -> Result<SendSuccess, SendError> {
 659                 let result = self.find_path(destination)
 660                         .and_then(|path| self.enqueue_onion_message(path, contents, reply_path, log_suffix));
 661
 662                 match result.as_ref() {
 663                         Err(SendError::GetNodeIdFailed) => {
 664                                 log_warn!(self.logger, "Unable to retrieve node id {}", log_suffix);
 665                         },
 666                         Err(SendError::PathNotFound) => {
 667                                 log_trace!(self.logger, "Failed to find path {}", log_suffix);
 668                         },
 669                         Err(e) => {
 670                                 log_trace!(self.logger, "Failed sending onion message {}: {:?}", log_suffix, e);
 671                         },
 672                         Ok(SendSuccess::Buffered) => {
 673                                 log_trace!(self.logger, "Buffered onion message {}", log_suffix);
 674                         },
 675                         Ok(SendSuccess::BufferedAwaitingConnection(node_id)) => {
 676                                 log_trace!(
 677                                         self.logger, "Buffered onion message waiting on peer connection {}: {:?}",
 678                                         log_suffix, node_id
 679                                 );
 680                         },
 681                 }
 682
 683                 result
 684         }
 685
 686         fn find_path(&self, destination: Destination) -> Result<OnionMessagePath, SendError> {
 687                 let sender = self.node_signer
 688                         .get_node_id(Recipient::Node)
 689                         .map_err(|_| SendError::GetNodeIdFailed)?;
 690
 691                 let peers = self.message_recipients.lock().unwrap()
 692                         .iter()
 693                         .filter(|(_, recipient)| matches!(recipient, OnionMessageRecipient::ConnectedPeer(_)))
 694                         .map(|(node_id, _)| *node_id)
 695                         .collect();
 696
 697                 self.message_router
 698                         .find_path(sender, peers, destination)
 699                         .map_err(|_| SendError::PathNotFound)
 700         }
 701
 702         fn enqueue_onion_message<T: OnionMessageContents>(
 703                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 704                 log_suffix: fmt::Arguments
 705         ) -> Result<SendSuccess, SendError> {
 706                 log_trace!(self.logger, "Constructing onion message {}: {:?}", log_suffix, contents);
 707
 708                 let (first_node_id, onion_message, addresses) = create_onion_message(
 709                         &self.entropy_source, &self.node_signer, &self.secp_ctx, path, contents, reply_path
 710                 )?;
 711
 712                 let mut message_recipients = self.message_recipients.lock().unwrap();
 713                 if outbound_buffer_full(&first_node_id, &message_recipients) {
 714                         return Err(SendError::BufferFull);
 715                 }
 716
 717                 match message_recipients.entry(first_node_id) {
 718                         hash_map::Entry::Vacant(e) => match addresses {
 719                                 None => Err(SendError::InvalidFirstHop(first_node_id)),
 720                                 Some(addresses) => {
 721                                         e.insert(OnionMessageRecipient::pending_connection(addresses))
 722                                                 .enqueue_message(onion_message);
 723                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 724                                 },
 725                         },
 726                         hash_map::Entry::Occupied(mut e) => {
 727                                 e.get_mut().enqueue_message(onion_message);
 728                                 Ok(SendSuccess::Buffered)
 729                         },
 730                 }
 731         }
 732
 733         #[cfg(test)]
 734         pub(super) fn send_onion_message_using_path<T: OnionMessageContents>(
 735                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
 736         ) -> Result<SendSuccess, SendError> {
 737                 self.enqueue_onion_message(path, contents, reply_path, format_args!(""))
 738         }
 739
 740         fn handle_onion_message_response<T: OnionMessageContents>(
 741                 &self, response: Option<T>, reply_path: Option<BlindedPath>, log_suffix: fmt::Arguments
 742         ) {
 743                 if let Some(response) = response {
 744                         match reply_path {
 745                                 Some(reply_path) => {
 746                                         let _ = self.find_path_and_enqueue_onion_message(
 747                                                 response, Destination::BlindedPath(reply_path), None, log_suffix
 748                                         );
 749                                 },
 750                                 None => {
 751                                         log_trace!(self.logger, "Missing reply path {}", log_suffix);
 752                                 },
 753                         }
 754                 }
 755         }
 756
 757         #[cfg(test)]
 758         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<OnionMessage>> {
 759                 let mut message_recipients = self.message_recipients.lock().unwrap();
 760                 let mut msgs = HashMap::new();
 761                 // We don't want to disconnect the peers by removing them entirely from the original map, so we
 762                 // release the pending message buffers individually.
 763                 for (node_id, recipient) in &mut *message_recipients {
 764                         msgs.insert(*node_id, recipient.release_pending_messages());
 765                 }
 766                 msgs
 767         }
 768 }
 769
 770 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageRecipient>) -> bool {
 771         const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
 772         const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
 773         let mut total_buffered_bytes = 0;
 774         let mut peer_buffered_bytes = 0;
 775         for (pk, peer_buf) in buffer {
 776                 for om in peer_buf.pending_messages() {
 777                         let om_len = om.serialized_length();
 778                         if pk == peer_node_id {
 779                                 peer_buffered_bytes += om_len;
 780                         }
 781                         total_buffered_bytes += om_len;
 782
 783                         if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
 784                                 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
 785                         {
 786                                 return true
 787                         }
 788                 }
 789         }
 790         false
 791 }
 792
 793 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> EventsProvider
 794 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 795 where
 796         ES::Target: EntropySource,
 797         NS::Target: NodeSigner,
 798         L::Target: Logger,
 799         MR::Target: MessageRouter,
 800         OMH::Target: OffersMessageHandler,
 801         CMH::Target: CustomOnionMessageHandler,
 802 {
 803         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
 804                 for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
 805                         if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
 806                                 if let Some(addresses) = addresses.take() {
 807                                         handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
 808                                 }
 809                         }
 810                 }
 811         }
 812 }
 813
 814 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> OnionMessageHandler
 815 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 816 where
 817         ES::Target: EntropySource,
 818         NS::Target: NodeSigner,
 819         L::Target: Logger,
 820         MR::Target: MessageRouter,
 821         OMH::Target: OffersMessageHandler,
 822         CMH::Target: CustomOnionMessageHandler,
 823 {
 824         fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &OnionMessage) {
 825                 match peel_onion_message(
 826                         msg, &self.secp_ctx, &*self.node_signer, &*self.logger, &*self.custom_handler
 827                 ) {
 828                         Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
 829                                 log_trace!(
 830                                         self.logger,
 831                                    "Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
 832                                         path_id, if reply_path.is_some() { "a" } else { "no" }, message);
 833
 834                                 match message {
 835                                         ParsedOnionMessageContents::Offers(msg) => {
 836                                                 let response = self.offers_handler.handle_message(msg);
 837                                                 self.handle_onion_message_response(
 838                                                         response, reply_path, format_args!(
 839                                                                 "when responding to Offers onion message with path_id {:02x?}",
 840                                                                 path_id
 841                                                         )
 842                                                 );
 843                                         },
 844                                         ParsedOnionMessageContents::Custom(msg) => {
 845                                                 let response = self.custom_handler.handle_custom_message(msg);
 846                                                 self.handle_onion_message_response(
 847                                                         response, reply_path, format_args!(
 848                                                                 "when responding to Custom onion message with path_id {:02x?}",
 849                                                                 path_id
 850                                                         )
 851                                                 );
 852                                         },
 853                                 }
 854                         },
 855                         Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
 856                                 let mut message_recipients = self.message_recipients.lock().unwrap();
 857                                 if outbound_buffer_full(&next_node_id, &message_recipients) {
 858                                         log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
 859                                         return
 860                                 }
 861
 862                                 #[cfg(fuzzing)]
 863                                 message_recipients
 864                                         .entry(next_node_id)
 865                                         .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()));
 866
 867                                 match message_recipients.entry(next_node_id) {
 868                                         hash_map::Entry::Occupied(mut e) if matches!(
 869                                                 e.get(), OnionMessageRecipient::ConnectedPeer(..)
 870                                         ) => {
 871                                                 e.get_mut().enqueue_message(onion_message);
 872                                                 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
 873                                         },
 874                                         _ => {
 875                                                 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
 876                                                 return
 877                                         },
 878                                 }
 879                         },
 880                         Err(e) => {
 881                                 log_error!(self.logger, "Failed to process onion message {:?}", e);
 882                         }
 883                 }
 884         }
 885
 886         fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
 887                 if init.features.supports_onion_messages() {
 888                         self.message_recipients.lock().unwrap()
 889                                 .entry(*their_node_id)
 890                                 .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()))
 891                                 .mark_connected();
 892                 } else {
 893                         self.message_recipients.lock().unwrap().remove(their_node_id);
 894                 }
 895
 896                 Ok(())
 897         }
 898
 899         fn peer_disconnected(&self, their_node_id: &PublicKey) {
 900                 match self.message_recipients.lock().unwrap().remove(their_node_id) {
 901                         Some(OnionMessageRecipient::ConnectedPeer(..)) => {},
 902                         _ => debug_assert!(false),
 903                 }
 904         }
 905
 906         fn timer_tick_occurred(&self) {
 907                 let mut message_recipients = self.message_recipients.lock().unwrap();
 908
 909                 // Drop any pending recipients since the last call to avoid retaining buffered messages for
 910                 // too long.
 911                 message_recipients.retain(|_, recipient| match recipient {
 912                         OnionMessageRecipient::PendingConnection(_, None, ticks) => *ticks < MAX_TIMER_TICKS,
 913                         OnionMessageRecipient::PendingConnection(_, Some(_), _) => true,
 914                         _ => true,
 915                 });
 916
 917                 // Increment a timer tick for pending recipients so that their buffered messages are dropped
 918                 // at MAX_TIMER_TICKS.
 919                 for recipient in message_recipients.values_mut() {
 920                         if let OnionMessageRecipient::PendingConnection(_, None, ticks) = recipient {
 921                                 *ticks += 1;
 922                         }
 923                 }
 924         }
 925
 926         fn provided_node_features(&self) -> NodeFeatures {
 927                 let mut features = NodeFeatures::empty();
 928                 features.set_onion_messages_optional();
 929                 features
 930         }
 931
 932         fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
 933                 let mut features = InitFeatures::empty();
 934                 features.set_onion_messages_optional();
 935                 features
 936         }
 937
 938         // Before returning any messages to send for the peer, this method will see if any messages were
 939         // enqueued in the handler by users, find a path to the corresponding blinded path's introduction
 940         // node, and then enqueue the message for sending to the first peer in the full path.
 941         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<OnionMessage> {
 942                 // Enqueue any initiating `OffersMessage`s to send.
 943                 for message in self.offers_handler.release_pending_messages() {
 944                         #[cfg(not(c_bindings))]
 945                         let PendingOnionMessage { contents, destination, reply_path } = message;
 946                         #[cfg(c_bindings)]
 947                         let (contents, destination, reply_path) = message;
 948                         let _ = self.find_path_and_enqueue_onion_message(
 949                                 contents, destination, reply_path, format_args!("when sending OffersMessage")
 950                         );
 951                 }
 952
 953                 // Enqueue any initiating `CustomMessage`s to send.
 954                 for message in self.custom_handler.release_pending_custom_messages() {
 955                         #[cfg(not(c_bindings))]
 956                         let PendingOnionMessage { contents, destination, reply_path } = message;
 957                         #[cfg(c_bindings)]
 958                         let (contents, destination, reply_path) = message;
 959                         let _ = self.find_path_and_enqueue_onion_message(
 960                                 contents, destination, reply_path, format_args!("when sending CustomMessage")
 961                         );
 962                 }
 963
 964                 self.message_recipients.lock().unwrap()
 965                         .get_mut(&peer_node_id)
 966                         .and_then(|buffer| buffer.dequeue_message())
 967         }
 968 }
 969
 970 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
 971 // produces
 972 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
 973 /// [`SimpleArcPeerManager`]. See their docs for more details.
 974 ///
 975 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 976 ///
 977 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 978 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
 979 #[cfg(not(c_bindings))]
 980 pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
 981         Arc<KeysManager>,
 982         Arc<KeysManager>,
 983         Arc<L>,
 984         Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>>>,
 985         Arc<SimpleArcChannelManager<M, T, F, L>>,
 986         IgnoringMessageHandler
 987 >;
 988
 989 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
 990 /// [`SimpleRefPeerManager`]. See their docs for more details.
 991 ///
 992 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 993 ///
 994 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
 995 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
 996 #[cfg(not(c_bindings))]
 997 pub type SimpleRefOnionMessenger<
 998         'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, M, T, F, L
 999 > = OnionMessenger<
1000         &'a KeysManager,
1001         &'a KeysManager,
1002         &'b L,
1003         &'i DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L>,
1004         &'j SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1005         IgnoringMessageHandler
1006 >;
1007
1008 /// Construct onion packet payloads and keys for sending an onion message along the given
1009 /// `unblinded_path` to the given `destination`.
1010 fn packet_payloads_and_keys<T: OnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
1011         secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination, message: T,
1012         mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
1013 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
1014         let num_hops = unblinded_path.len() + destination.num_hops();
1015         let mut payloads = Vec::with_capacity(num_hops);
1016         let mut onion_packet_keys = Vec::with_capacity(num_hops);
1017
1018         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedPath(BlindedPath {
1019                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
1020                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
1021         let num_unblinded_hops = num_hops - num_blinded_hops;
1022
1023         let mut unblinded_path_idx = 0;
1024         let mut blinded_path_idx = 0;
1025         let mut prev_control_tlvs_ss = None;
1026         let mut final_control_tlvs = None;
1027         utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), Some(destination), session_priv,
1028                 |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
1029                         if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
1030                                 if let Some(ss) = prev_control_tlvs_ss.take() {
1031                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
1032                                                 ForwardTlvs {
1033                                                         next_node_id: unblinded_pk_opt.unwrap(),
1034                                                         next_blinding_override: None,
1035                                                 }
1036                                         )), ss));
1037                                 }
1038                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1039                                 unblinded_path_idx += 1;
1040                         } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
1041                                 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
1042                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
1043                                                 next_node_id: intro_node_id,
1044                                                 next_blinding_override: Some(blinding_pt),
1045                                         })), control_tlvs_ss));
1046                                 }
1047                         }
1048                         if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
1049                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
1050                                         control_tlvs_ss));
1051                                 blinded_path_idx += 1;
1052                         } else if let Some(encrypted_payload) = enc_payload_opt {
1053                                 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
1054                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1055                         }
1056
1057                         let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
1058                         onion_packet_keys.push(onion_utils::OnionKeys {
1059                                 #[cfg(test)]
1060                                 shared_secret: onion_packet_ss,
1061                                 #[cfg(test)]
1062                                 blinding_factor: [0; 32],
1063                                 ephemeral_pubkey,
1064                                 rho,
1065                                 mu,
1066                         });
1067                 }
1068         )?;
1069
1070         if let Some(control_tlvs) = final_control_tlvs {
1071                 payloads.push((Payload::Receive {
1072                         control_tlvs,
1073                         reply_path: reply_path.take(),
1074                         message,
1075                 }, prev_control_tlvs_ss.unwrap()));
1076         } else {
1077                 payloads.push((Payload::Receive {
1078                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
1079                         reply_path: reply_path.take(),
1080                         message,
1081                 }, prev_control_tlvs_ss.unwrap()));
1082         }
1083
1084         Ok((payloads, onion_packet_keys))
1085 }
1086
1087 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
1088 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, ()> {
1089         // Spec rationale:
1090         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
1091         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
1092         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
1093         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
1094         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
1095                 SMALL_PACKET_HOP_DATA_LEN
1096         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
1097                 BIG_PACKET_HOP_DATA_LEN
1098         } else { return Err(()) };
1099
1100         onion_utils::construct_onion_message_packet::<_, _>(
1101                 payloads, onion_keys, prng_seed, hop_data_len)
1102 }