_ 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 /// #             first_node_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 {
 296                                 intermediate_nodes: vec![], destination, first_node_addresses: None
 297                         })
 298                 } else {
 299                         let network_graph = self.network_graph.deref().read_only();
 300                         let node_announcement = network_graph
 301                                 .node(&NodeId::from_pubkey(&first_node))
 302                                 .and_then(|node_info| node_info.announcement_info.as_ref())
 303                                 .and_then(|announcement_info| announcement_info.announcement_message.as_ref())
 304                                 .map(|node_announcement| &node_announcement.contents);
 305
 306                         match node_announcement {
 307                                 Some(node_announcement) if node_announcement.features.supports_onion_messages() => {
 308                                         let first_node_addresses = Some(node_announcement.addresses.clone());
 309                                         Ok(OnionMessagePath {
 310                                                 intermediate_nodes: vec![], destination, first_node_addresses
 311                                         })
 312                                 },
 313                                 _ => Err(()),
 314                         }
 315                 }
 316         }
 317 }
 318
 319 /// A path for sending an [`OnionMessage`].
 320 #[derive(Clone)]
 321 pub struct OnionMessagePath {
 322         /// Nodes on the path between the sender and the destination.
 323         pub intermediate_nodes: Vec<PublicKey>,
 324
 325         /// The recipient of the message.
 326         pub destination: Destination,
 327
 328         /// Addresses that may be used to connect to [`OnionMessagePath::first_node`].
 329         ///
 330         /// Only needs to be set if a connection to the node is required. [`OnionMessenger`] may use
 331         /// this to initiate such a connection.
 332         pub first_node_addresses: Option<Vec<SocketAddress>>,
 333 }
 334
 335 impl OnionMessagePath {
 336         /// Returns the first node in the path.
 337         pub fn first_node(&self) -> PublicKey {
 338                 self.intermediate_nodes
 339                         .first()
 340                         .copied()
 341                         .unwrap_or_else(|| self.destination.first_node())
 342         }
 343 }
 344
 345 /// The destination of an onion message.
 346 #[derive(Clone)]
 347 pub enum Destination {
 348         /// We're sending this onion message to a node.
 349         Node(PublicKey),
 350         /// We're sending this onion message to a blinded path.
 351         BlindedPath(BlindedPath),
 352 }
 353
 354 impl Destination {
 355         pub(super) fn num_hops(&self) -> usize {
 356                 match self {
 357                         Destination::Node(_) => 1,
 358                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
 359                 }
 360         }
 361
 362         fn first_node(&self) -> PublicKey {
 363                 match self {
 364                         Destination::Node(node_id) => *node_id,
 365                         Destination::BlindedPath(BlindedPath { introduction_node_id: node_id, .. }) => *node_id,
 366                 }
 367         }
 368 }
 369
 370 /// Result of successfully [sending an onion message].
 371 ///
 372 /// [sending an onion message]: OnionMessenger::send_onion_message
 373 #[derive(Debug, PartialEq, Eq)]
 374 pub enum SendSuccess {
 375         /// The message was buffered and will be sent once it is processed by
 376         /// [`OnionMessageHandler::next_onion_message_for_peer`].
 377         Buffered,
 378         /// The message was buffered and will be sent once the node is connected as a peer and it is
 379         /// processed by [`OnionMessageHandler::next_onion_message_for_peer`].
 380         BufferedAwaitingConnection(PublicKey),
 381 }
 382
 383 /// Errors that may occur when [sending an onion message].
 384 ///
 385 /// [sending an onion message]: OnionMessenger::send_onion_message
 386 #[derive(Debug, PartialEq, Eq)]
 387 pub enum SendError {
 388         /// Errored computing onion message packet keys.
 389         Secp256k1(secp256k1::Error),
 390         /// Because implementations such as Eclair will drop onion messages where the message packet
 391         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
 392         TooBigPacket,
 393         /// The provided [`Destination`] was an invalid [`BlindedPath`] due to not having any blinded
 394         /// hops.
 395         TooFewBlindedHops,
 396         /// The first hop is not a peer and doesn't have a known [`SocketAddress`].
 397         InvalidFirstHop(PublicKey),
 398         /// A path from the sender to the destination could not be found by the [`MessageRouter`].
 399         PathNotFound,
 400         /// Onion message contents must have a TLV type >= 64.
 401         InvalidMessage,
 402         /// Our next-hop peer's buffer was full or our total outbound buffer was full.
 403         BufferFull,
 404         /// Failed to retrieve our node id from the provided [`NodeSigner`].
 405         ///
 406         /// [`NodeSigner`]: crate::sign::NodeSigner
 407         GetNodeIdFailed,
 408         /// We attempted to send to a blinded path where we are the introduction node, and failed to
 409         /// advance the blinded path to make the second hop the new introduction node. Either
 410         /// [`NodeSigner::ecdh`] failed, we failed to tweak the current blinding point to get the
 411         /// new blinding point, or we were attempting to send to ourselves.
 412         BlindedPathAdvanceFailed,
 413 }
 414
 415 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
 416 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
 417 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
 418 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
 419 /// message types.
 420 ///
 421 /// See [`OnionMessenger`] for example usage.
 422 ///
 423 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
 424 /// [`CustomMessage`]: Self::CustomMessage
 425 pub trait CustomOnionMessageHandler {
 426         /// The message known to the handler. To support multiple message types, you may want to make this
 427         /// an enum with a variant for each supported message.
 428         type CustomMessage: OnionMessageContents;
 429
 430         /// Called with the custom message that was received, returning a response to send, if any.
 431         ///
 432         /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
 433         fn handle_custom_message(&self, msg: Self::CustomMessage) -> Option<Self::CustomMessage>;
 434
 435         /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
 436         /// message type is unknown.
 437         fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 438
 439         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 440         ///
 441         /// Typically, this is used for messages initiating a message flow rather than in response to
 442         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 443         #[cfg(not(c_bindings))]
 444         fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
 445
 446         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 447         ///
 448         /// Typically, this is used for messages initiating a message flow rather than in response to
 449         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 450         #[cfg(c_bindings)]
 451         fn release_pending_custom_messages(&self) -> Vec<(Self::CustomMessage, Destination, Option<BlindedPath>)>;
 452 }
 453
 454 /// A processed incoming onion message, containing either a Forward (another onion message)
 455 /// or a Receive payload with decrypted contents.
 456 pub enum PeeledOnion<T: OnionMessageContents> {
 457         /// Forwarded onion, with the next node id and a new onion
 458         Forward(PublicKey, OnionMessage),
 459         /// Received onion message, with decrypted contents, path_id, and reply path
 460         Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
 461 }
 462
 463 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 464 /// `path`.
 465 ///
 466 /// Returns the node id of the peer to send the message to, the message itself, and any addresses
 467 /// need to connect to the first node.
 468 pub fn create_onion_message<ES: Deref, NS: Deref, T: OnionMessageContents>(
 469         entropy_source: &ES, node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>,
 470         path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 471 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 472 where
 473         ES::Target: EntropySource,
 474         NS::Target: NodeSigner,
 475 {
 476         let OnionMessagePath { intermediate_nodes, mut destination, first_node_addresses } = path;
 477         if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
 478                 if blinded_hops.is_empty() {
 479                         return Err(SendError::TooFewBlindedHops);
 480                 }
 481         }
 482
 483         if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
 484
 485         // If we are sending straight to a blinded path and we are the introduction node, we need to
 486         // advance the blinded path by 1 hop so the second hop is the new introduction node.
 487         if intermediate_nodes.len() == 0 {
 488                 if let Destination::BlindedPath(ref mut blinded_path) = destination {
 489                         let our_node_id = node_signer.get_node_id(Recipient::Node)
 490                                 .map_err(|()| SendError::GetNodeIdFailed)?;
 491                         if blinded_path.introduction_node_id == our_node_id {
 492                                 advance_path_by_one(blinded_path, node_signer, &secp_ctx)
 493                                         .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
 494                         }
 495                 }
 496         }
 497
 498         let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 499         let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 500         let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
 501                 (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
 502         } else {
 503                 match destination {
 504                         Destination::Node(pk) => (pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
 505                         Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
 506                                 (introduction_node_id, blinding_point),
 507                 }
 508         };
 509         let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 510                 &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret)
 511                 .map_err(|e| SendError::Secp256k1(e))?;
 512
 513         let prng_seed = entropy_source.get_secure_random_bytes();
 514         let onion_routing_packet = construct_onion_message_packet(
 515                 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
 516
 517         let message = OnionMessage { blinding_point, onion_routing_packet };
 518         Ok((first_node_id, message, first_node_addresses))
 519 }
 520
 521 /// Decode one layer of an incoming [`OnionMessage`].
 522 ///
 523 /// Returns either the next layer of the onion for forwarding or the decrypted content for the
 524 /// receiver.
 525 pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
 526         msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
 527         custom_handler: CMH,
 528 ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
 529 where
 530         NS::Target: NodeSigner,
 531         L::Target: Logger,
 532         CMH::Target: CustomOnionMessageHandler,
 533 {
 534         let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
 535                 Ok(ss) => ss,
 536                 Err(e) =>  {
 537                         log_error!(logger, "Failed to retrieve node secret: {:?}", e);
 538                         return Err(());
 539                 }
 540         };
 541         let onion_decode_ss = {
 542                 let blinding_factor = {
 543                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 544                         hmac.input(control_tlvs_ss.as_ref());
 545                         Hmac::from_engine(hmac).to_byte_array()
 546                 };
 547                 match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 548                         Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
 549                 {
 550                         Ok(ss) => ss.secret_bytes(),
 551                         Err(()) => {
 552                                 log_trace!(logger, "Failed to compute onion packet shared secret");
 553                                 return Err(());
 554                         }
 555                 }
 556         };
 557         match onion_utils::decode_next_untagged_hop(
 558                 onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 559                 (control_tlvs_ss, custom_handler.deref(), logger.deref())
 560         ) {
 561                 Ok((Payload::Receive::<ParsedOnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>> {
 562                         message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
 563                 }, None)) => {
 564                         Ok(PeeledOnion::Receive(message, path_id, reply_path))
 565                 },
 566                 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 567                         next_node_id, next_blinding_override
 568                 })), Some((next_hop_hmac, new_packet_bytes)))) => {
 569                         // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 570                         // blinded hop and this onion message is destined for us. In this situation, we should keep
 571                         // unwrapping the onion layers to get to the final payload. Since we don't have the option
 572                         // of creating blinded paths with dummy hops currently, we should be ok to not handle this
 573                         // for now.
 574                         let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 575                                 Ok(pk) => pk,
 576                                 Err(e) => {
 577                                         log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
 578                                         return Err(())
 579                                 }
 580                         };
 581                         let outgoing_packet = Packet {
 582                                 version: 0,
 583                                 public_key: new_pubkey,
 584                                 hop_data: new_packet_bytes,
 585                                 hmac: next_hop_hmac,
 586                         };
 587                         let onion_message = OnionMessage {
 588                                 blinding_point: match next_blinding_override {
 589                                         Some(blinding_point) => blinding_point,
 590                                         None => {
 591                                                 match onion_utils::next_hop_pubkey(
 592                                                         &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
 593                                                 ) {
 594                                                         Ok(bp) => bp,
 595                                                         Err(e) => {
 596                                                                 log_trace!(logger, "Failed to compute next blinding point: {}", e);
 597                                                                 return Err(())
 598                                                         }
 599                                                 }
 600                                         }
 601                                 },
 602                                 onion_routing_packet: outgoing_packet,
 603                         };
 604
 605                         Ok(PeeledOnion::Forward(next_node_id, onion_message))
 606                 },
 607                 Err(e) => {
 608                         log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
 609                         Err(())
 610                 },
 611                 _ => {
 612                         log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 613                         Err(())
 614                 },
 615         }
 616 }
 617
 618 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 619 OnionMessenger<ES, NS, L, MR, OMH, CMH>
 620 where
 621         ES::Target: EntropySource,
 622         NS::Target: NodeSigner,
 623         L::Target: Logger,
 624         MR::Target: MessageRouter,
 625         OMH::Target: OffersMessageHandler,
 626         CMH::Target: CustomOnionMessageHandler,
 627 {
 628         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
 629         /// their respective handlers.
 630         pub fn new(
 631                 entropy_source: ES, node_signer: NS, logger: L, message_router: MR, offers_handler: OMH,
 632                 custom_handler: CMH
 633         ) -> Self {
 634                 let mut secp_ctx = Secp256k1::new();
 635                 secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 636                 OnionMessenger {
 637                         entropy_source,
 638                         node_signer,
 639                         message_recipients: Mutex::new(HashMap::new()),
 640                         secp_ctx,
 641                         logger,
 642                         message_router,
 643                         offers_handler,
 644                         custom_handler,
 645                 }
 646         }
 647
 648         /// Sends an [`OnionMessage`] with the given `contents` to `destination`.
 649         ///
 650         /// See [`OnionMessenger`] for example usage.
 651         pub fn send_onion_message<T: OnionMessageContents>(
 652                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>
 653         ) -> Result<SendSuccess, SendError> {
 654                 self.find_path_and_enqueue_onion_message(
 655                         contents, destination, reply_path, format_args!("")
 656                 )
 657         }
 658
 659         fn find_path_and_enqueue_onion_message<T: OnionMessageContents>(
 660                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>,
 661                 log_suffix: fmt::Arguments
 662         ) -> Result<SendSuccess, SendError> {
 663                 let result = self.find_path(destination)
 664                         .and_then(|path| self.enqueue_onion_message(path, contents, reply_path, log_suffix));
 665
 666                 match result.as_ref() {
 667                         Err(SendError::GetNodeIdFailed) => {
 668                                 log_warn!(self.logger, "Unable to retrieve node id {}", log_suffix);
 669                         },
 670                         Err(SendError::PathNotFound) => {
 671                                 log_trace!(self.logger, "Failed to find path {}", log_suffix);
 672                         },
 673                         Err(e) => {
 674                                 log_trace!(self.logger, "Failed sending onion message {}: {:?}", log_suffix, e);
 675                         },
 676                         Ok(SendSuccess::Buffered) => {
 677                                 log_trace!(self.logger, "Buffered onion message {}", log_suffix);
 678                         },
 679                         Ok(SendSuccess::BufferedAwaitingConnection(node_id)) => {
 680                                 log_trace!(
 681                                         self.logger, "Buffered onion message waiting on peer connection {}: {:?}",
 682                                         log_suffix, node_id
 683                                 );
 684                         },
 685                 }
 686
 687                 result
 688         }
 689
 690         fn find_path(&self, destination: Destination) -> Result<OnionMessagePath, SendError> {
 691                 let sender = self.node_signer
 692                         .get_node_id(Recipient::Node)
 693                         .map_err(|_| SendError::GetNodeIdFailed)?;
 694
 695                 let peers = self.message_recipients.lock().unwrap()
 696                         .iter()
 697                         .filter(|(_, recipient)| matches!(recipient, OnionMessageRecipient::ConnectedPeer(_)))
 698                         .map(|(node_id, _)| *node_id)
 699                         .collect();
 700
 701                 self.message_router
 702                         .find_path(sender, peers, destination)
 703                         .map_err(|_| SendError::PathNotFound)
 704         }
 705
 706         fn enqueue_onion_message<T: OnionMessageContents>(
 707                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 708                 log_suffix: fmt::Arguments
 709         ) -> Result<SendSuccess, SendError> {
 710                 log_trace!(self.logger, "Constructing onion message {}: {:?}", log_suffix, contents);
 711
 712                 let (first_node_id, onion_message, addresses) = create_onion_message(
 713                         &self.entropy_source, &self.node_signer, &self.secp_ctx, path, contents, reply_path
 714                 )?;
 715
 716                 let mut message_recipients = self.message_recipients.lock().unwrap();
 717                 if outbound_buffer_full(&first_node_id, &message_recipients) {
 718                         return Err(SendError::BufferFull);
 719                 }
 720
 721                 match message_recipients.entry(first_node_id) {
 722                         hash_map::Entry::Vacant(e) => match addresses {
 723                                 None => Err(SendError::InvalidFirstHop(first_node_id)),
 724                                 Some(addresses) => {
 725                                         e.insert(OnionMessageRecipient::pending_connection(addresses))
 726                                                 .enqueue_message(onion_message);
 727                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 728                                 },
 729                         },
 730                         hash_map::Entry::Occupied(mut e) => {
 731                                 e.get_mut().enqueue_message(onion_message);
 732                                 Ok(SendSuccess::Buffered)
 733                         },
 734                 }
 735         }
 736
 737         #[cfg(test)]
 738         pub(super) fn send_onion_message_using_path<T: OnionMessageContents>(
 739                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
 740         ) -> Result<SendSuccess, SendError> {
 741                 self.enqueue_onion_message(path, contents, reply_path, format_args!(""))
 742         }
 743
 744         fn handle_onion_message_response<T: OnionMessageContents>(
 745                 &self, response: Option<T>, reply_path: Option<BlindedPath>, log_suffix: fmt::Arguments
 746         ) {
 747                 if let Some(response) = response {
 748                         match reply_path {
 749                                 Some(reply_path) => {
 750                                         let _ = self.find_path_and_enqueue_onion_message(
 751                                                 response, Destination::BlindedPath(reply_path), None, log_suffix
 752                                         );
 753                                 },
 754                                 None => {
 755                                         log_trace!(self.logger, "Missing reply path {}", log_suffix);
 756                                 },
 757                         }
 758                 }
 759         }
 760
 761         #[cfg(test)]
 762         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<OnionMessage>> {
 763                 let mut message_recipients = self.message_recipients.lock().unwrap();
 764                 let mut msgs = HashMap::new();
 765                 // We don't want to disconnect the peers by removing them entirely from the original map, so we
 766                 // release the pending message buffers individually.
 767                 for (node_id, recipient) in &mut *message_recipients {
 768                         msgs.insert(*node_id, recipient.release_pending_messages());
 769                 }
 770                 msgs
 771         }
 772 }
 773
 774 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageRecipient>) -> bool {
 775         const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
 776         const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
 777         let mut total_buffered_bytes = 0;
 778         let mut peer_buffered_bytes = 0;
 779         for (pk, peer_buf) in buffer {
 780                 for om in peer_buf.pending_messages() {
 781                         let om_len = om.serialized_length();
 782                         if pk == peer_node_id {
 783                                 peer_buffered_bytes += om_len;
 784                         }
 785                         total_buffered_bytes += om_len;
 786
 787                         if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
 788                                 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
 789                         {
 790                                 return true
 791                         }
 792                 }
 793         }
 794         false
 795 }
 796
 797 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> EventsProvider
 798 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 799 where
 800         ES::Target: EntropySource,
 801         NS::Target: NodeSigner,
 802         L::Target: Logger,
 803         MR::Target: MessageRouter,
 804         OMH::Target: OffersMessageHandler,
 805         CMH::Target: CustomOnionMessageHandler,
 806 {
 807         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
 808                 for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
 809                         if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
 810                                 if let Some(addresses) = addresses.take() {
 811                                         handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
 812                                 }
 813                         }
 814                 }
 815         }
 816 }
 817
 818 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> OnionMessageHandler
 819 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 820 where
 821         ES::Target: EntropySource,
 822         NS::Target: NodeSigner,
 823         L::Target: Logger,
 824         MR::Target: MessageRouter,
 825         OMH::Target: OffersMessageHandler,
 826         CMH::Target: CustomOnionMessageHandler,
 827 {
 828         fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &OnionMessage) {
 829                 match peel_onion_message(
 830                         msg, &self.secp_ctx, &*self.node_signer, &*self.logger, &*self.custom_handler
 831                 ) {
 832                         Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
 833                                 log_trace!(
 834                                         self.logger,
 835                                    "Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
 836                                         path_id, if reply_path.is_some() { "a" } else { "no" }, message);
 837
 838                                 match message {
 839                                         ParsedOnionMessageContents::Offers(msg) => {
 840                                                 let response = self.offers_handler.handle_message(msg);
 841                                                 self.handle_onion_message_response(
 842                                                         response, reply_path, format_args!(
 843                                                                 "when responding to Offers onion message with path_id {:02x?}",
 844                                                                 path_id
 845                                                         )
 846                                                 );
 847                                         },
 848                                         ParsedOnionMessageContents::Custom(msg) => {
 849                                                 let response = self.custom_handler.handle_custom_message(msg);
 850                                                 self.handle_onion_message_response(
 851                                                         response, reply_path, format_args!(
 852                                                                 "when responding to Custom onion message with path_id {:02x?}",
 853                                                                 path_id
 854                                                         )
 855                                                 );
 856                                         },
 857                                 }
 858                         },
 859                         Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
 860                                 let mut message_recipients = self.message_recipients.lock().unwrap();
 861                                 if outbound_buffer_full(&next_node_id, &message_recipients) {
 862                                         log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
 863                                         return
 864                                 }
 865
 866                                 #[cfg(fuzzing)]
 867                                 message_recipients
 868                                         .entry(next_node_id)
 869                                         .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()));
 870
 871                                 match message_recipients.entry(next_node_id) {
 872                                         hash_map::Entry::Occupied(mut e) if matches!(
 873                                                 e.get(), OnionMessageRecipient::ConnectedPeer(..)
 874                                         ) => {
 875                                                 e.get_mut().enqueue_message(onion_message);
 876                                                 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
 877                                         },
 878                                         _ => {
 879                                                 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
 880                                                 return
 881                                         },
 882                                 }
 883                         },
 884                         Err(e) => {
 885                                 log_error!(self.logger, "Failed to process onion message {:?}", e);
 886                         }
 887                 }
 888         }
 889
 890         fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
 891                 if init.features.supports_onion_messages() {
 892                         self.message_recipients.lock().unwrap()
 893                                 .entry(*their_node_id)
 894                                 .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()))
 895                                 .mark_connected();
 896                 } else {
 897                         self.message_recipients.lock().unwrap().remove(their_node_id);
 898                 }
 899
 900                 Ok(())
 901         }
 902
 903         fn peer_disconnected(&self, their_node_id: &PublicKey) {
 904                 match self.message_recipients.lock().unwrap().remove(their_node_id) {
 905                         Some(OnionMessageRecipient::ConnectedPeer(..)) => {},
 906                         _ => debug_assert!(false),
 907                 }
 908         }
 909
 910         fn timer_tick_occurred(&self) {
 911                 let mut message_recipients = self.message_recipients.lock().unwrap();
 912
 913                 // Drop any pending recipients since the last call to avoid retaining buffered messages for
 914                 // too long.
 915                 message_recipients.retain(|_, recipient| match recipient {
 916                         OnionMessageRecipient::PendingConnection(_, None, ticks) => *ticks < MAX_TIMER_TICKS,
 917                         OnionMessageRecipient::PendingConnection(_, Some(_), _) => true,
 918                         _ => true,
 919                 });
 920
 921                 // Increment a timer tick for pending recipients so that their buffered messages are dropped
 922                 // at MAX_TIMER_TICKS.
 923                 for recipient in message_recipients.values_mut() {
 924                         if let OnionMessageRecipient::PendingConnection(_, None, ticks) = recipient {
 925                                 *ticks += 1;
 926                         }
 927                 }
 928         }
 929
 930         fn provided_node_features(&self) -> NodeFeatures {
 931                 let mut features = NodeFeatures::empty();
 932                 features.set_onion_messages_optional();
 933                 features
 934         }
 935
 936         fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
 937                 let mut features = InitFeatures::empty();
 938                 features.set_onion_messages_optional();
 939                 features
 940         }
 941
 942         // Before returning any messages to send for the peer, this method will see if any messages were
 943         // enqueued in the handler by users, find a path to the corresponding blinded path's introduction
 944         // node, and then enqueue the message for sending to the first peer in the full path.
 945         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<OnionMessage> {
 946                 // Enqueue any initiating `OffersMessage`s to send.
 947                 for message in self.offers_handler.release_pending_messages() {
 948                         #[cfg(not(c_bindings))]
 949                         let PendingOnionMessage { contents, destination, reply_path } = message;
 950                         #[cfg(c_bindings)]
 951                         let (contents, destination, reply_path) = message;
 952                         let _ = self.find_path_and_enqueue_onion_message(
 953                                 contents, destination, reply_path, format_args!("when sending OffersMessage")
 954                         );
 955                 }
 956
 957                 // Enqueue any initiating `CustomMessage`s to send.
 958                 for message in self.custom_handler.release_pending_custom_messages() {
 959                         #[cfg(not(c_bindings))]
 960                         let PendingOnionMessage { contents, destination, reply_path } = message;
 961                         #[cfg(c_bindings)]
 962                         let (contents, destination, reply_path) = message;
 963                         let _ = self.find_path_and_enqueue_onion_message(
 964                                 contents, destination, reply_path, format_args!("when sending CustomMessage")
 965                         );
 966                 }
 967
 968                 self.message_recipients.lock().unwrap()
 969                         .get_mut(&peer_node_id)
 970                         .and_then(|buffer| buffer.dequeue_message())
 971         }
 972 }
 973
 974 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
 975 // produces
 976 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
 977 /// [`SimpleArcPeerManager`]. See their docs for more details.
 978 ///
 979 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 980 ///
 981 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 982 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
 983 #[cfg(not(c_bindings))]
 984 pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
 985         Arc<KeysManager>,
 986         Arc<KeysManager>,
 987         Arc<L>,
 988         Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>>>,
 989         Arc<SimpleArcChannelManager<M, T, F, L>>,
 990         IgnoringMessageHandler
 991 >;
 992
 993 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
 994 /// [`SimpleRefPeerManager`]. See their docs for more details.
 995 ///
 996 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 997 ///
 998 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
 999 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
1000 #[cfg(not(c_bindings))]
1001 pub type SimpleRefOnionMessenger<
1002         'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, M, T, F, L
1003 > = OnionMessenger<
1004         &'a KeysManager,
1005         &'a KeysManager,
1006         &'b L,
1007         &'i DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L>,
1008         &'j SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1009         IgnoringMessageHandler
1010 >;
1011
1012 /// Construct onion packet payloads and keys for sending an onion message along the given
1013 /// `unblinded_path` to the given `destination`.
1014 fn packet_payloads_and_keys<T: OnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
1015         secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination, message: T,
1016         mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
1017 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
1018         let num_hops = unblinded_path.len() + destination.num_hops();
1019         let mut payloads = Vec::with_capacity(num_hops);
1020         let mut onion_packet_keys = Vec::with_capacity(num_hops);
1021
1022         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedPath(BlindedPath {
1023                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
1024                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
1025         let num_unblinded_hops = num_hops - num_blinded_hops;
1026
1027         let mut unblinded_path_idx = 0;
1028         let mut blinded_path_idx = 0;
1029         let mut prev_control_tlvs_ss = None;
1030         let mut final_control_tlvs = None;
1031         utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), Some(destination), session_priv,
1032                 |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
1033                         if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
1034                                 if let Some(ss) = prev_control_tlvs_ss.take() {
1035                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
1036                                                 ForwardTlvs {
1037                                                         next_node_id: unblinded_pk_opt.unwrap(),
1038                                                         next_blinding_override: None,
1039                                                 }
1040                                         )), ss));
1041                                 }
1042                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1043                                 unblinded_path_idx += 1;
1044                         } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
1045                                 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
1046                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
1047                                                 next_node_id: intro_node_id,
1048                                                 next_blinding_override: Some(blinding_pt),
1049                                         })), control_tlvs_ss));
1050                                 }
1051                         }
1052                         if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
1053                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
1054                                         control_tlvs_ss));
1055                                 blinded_path_idx += 1;
1056                         } else if let Some(encrypted_payload) = enc_payload_opt {
1057                                 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
1058                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1059                         }
1060
1061                         let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
1062                         onion_packet_keys.push(onion_utils::OnionKeys {
1063                                 #[cfg(test)]
1064                                 shared_secret: onion_packet_ss,
1065                                 #[cfg(test)]
1066                                 blinding_factor: [0; 32],
1067                                 ephemeral_pubkey,
1068                                 rho,
1069                                 mu,
1070                         });
1071                 }
1072         )?;
1073
1074         if let Some(control_tlvs) = final_control_tlvs {
1075                 payloads.push((Payload::Receive {
1076                         control_tlvs,
1077                         reply_path: reply_path.take(),
1078                         message,
1079                 }, prev_control_tlvs_ss.unwrap()));
1080         } else {
1081                 payloads.push((Payload::Receive {
1082                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
1083                         reply_path: reply_path.take(),
1084                         message,
1085                 }, prev_control_tlvs_ss.unwrap()));
1086         }
1087
1088         Ok((payloads, onion_packet_keys))
1089 }
1090
1091 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
1092 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, ()> {
1093         // Spec rationale:
1094         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
1095         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
1096         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
1097         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
1098         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
1099                 SMALL_PACKET_HOP_DATA_LEN
1100         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
1101                 BIG_PACKET_HOP_DATA_LEN
1102         } else { return Err(()) };
1103
1104         onion_utils::construct_onion_message_packet::<_, _>(
1105                 payloads, onion_keys, prng_seed, hop_data_len)
1106 }