_ 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         fn is_connected(&self) -> bool {
 228                 match self {
 229                         OnionMessageRecipient::ConnectedPeer(..) => true,
 230                         OnionMessageRecipient::PendingConnection(..) => false,
 231                 }
 232         }
 233 }
 234
 235 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 236 ///
 237 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 238 /// enqueued for sending.
 239 #[cfg(not(c_bindings))]
 240 pub struct PendingOnionMessage<T: OnionMessageContents> {
 241         /// The message contents to send in an [`OnionMessage`].
 242         pub contents: T,
 243
 244         /// The destination of the message.
 245         pub destination: Destination,
 246
 247         /// A reply path to include in the [`OnionMessage`] for a response.
 248         pub reply_path: Option<BlindedPath>,
 249 }
 250
 251 #[cfg(c_bindings)]
 252 /// An [`OnionMessage`] for [`OnionMessenger`] to send.
 253 ///
 254 /// These are obtained when released from [`OnionMessenger`]'s handlers after which they are
 255 /// enqueued for sending.
 256 pub type PendingOnionMessage<T: OnionMessageContents> = (T, Destination, Option<BlindedPath>);
 257
 258 pub(crate) fn new_pending_onion_message<T: OnionMessageContents>(
 259         contents: T, destination: Destination, reply_path: Option<BlindedPath>
 260 ) -> PendingOnionMessage<T> {
 261         #[cfg(not(c_bindings))]
 262         return PendingOnionMessage { contents, destination, reply_path };
 263         #[cfg(c_bindings)]
 264         return (contents, destination, reply_path);
 265 }
 266
 267 /// A trait defining behavior for routing an [`OnionMessage`].
 268 pub trait MessageRouter {
 269         /// Returns a route for sending an [`OnionMessage`] to the given [`Destination`].
 270         fn find_path(
 271                 &self, sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 272         ) -> Result<OnionMessagePath, ()>;
 273 }
 274
 275 /// A [`MessageRouter`] that can only route to a directly connected [`Destination`].
 276 pub struct DefaultMessageRouter<G: Deref<Target=NetworkGraph<L>>, L: Deref>
 277 where
 278         L::Target: Logger,
 279 {
 280         network_graph: G,
 281 }
 282
 283 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> DefaultMessageRouter<G, L>
 284 where
 285         L::Target: Logger,
 286 {
 287         /// Creates a [`DefaultMessageRouter`] using the given [`NetworkGraph`].
 288         pub fn new(network_graph: G) -> Self {
 289                 Self { network_graph }
 290         }
 291 }
 292
 293 impl<G: Deref<Target=NetworkGraph<L>>, L: Deref> MessageRouter for DefaultMessageRouter<G, L>
 294 where
 295         L::Target: Logger,
 296 {
 297         fn find_path(
 298                 &self, _sender: PublicKey, peers: Vec<PublicKey>, destination: Destination
 299         ) -> Result<OnionMessagePath, ()> {
 300                 let first_node = destination.first_node();
 301                 if peers.contains(&first_node) {
 302                         Ok(OnionMessagePath {
 303                                 intermediate_nodes: vec![], destination, first_node_addresses: None
 304                         })
 305                 } else {
 306                         let network_graph = self.network_graph.deref().read_only();
 307                         let node_announcement = network_graph
 308                                 .node(&NodeId::from_pubkey(&first_node))
 309                                 .and_then(|node_info| node_info.announcement_info.as_ref())
 310                                 .and_then(|announcement_info| announcement_info.announcement_message.as_ref())
 311                                 .map(|node_announcement| &node_announcement.contents);
 312
 313                         match node_announcement {
 314                                 Some(node_announcement) if node_announcement.features.supports_onion_messages() => {
 315                                         let first_node_addresses = Some(node_announcement.addresses.clone());
 316                                         Ok(OnionMessagePath {
 317                                                 intermediate_nodes: vec![], destination, first_node_addresses
 318                                         })
 319                                 },
 320                                 _ => Err(()),
 321                         }
 322                 }
 323         }
 324 }
 325
 326 /// A path for sending an [`OnionMessage`].
 327 #[derive(Clone)]
 328 pub struct OnionMessagePath {
 329         /// Nodes on the path between the sender and the destination.
 330         pub intermediate_nodes: Vec<PublicKey>,
 331
 332         /// The recipient of the message.
 333         pub destination: Destination,
 334
 335         /// Addresses that may be used to connect to [`OnionMessagePath::first_node`].
 336         ///
 337         /// Only needs to be set if a connection to the node is required. [`OnionMessenger`] may use
 338         /// this to initiate such a connection.
 339         pub first_node_addresses: Option<Vec<SocketAddress>>,
 340 }
 341
 342 impl OnionMessagePath {
 343         /// Returns the first node in the path.
 344         pub fn first_node(&self) -> PublicKey {
 345                 self.intermediate_nodes
 346                         .first()
 347                         .copied()
 348                         .unwrap_or_else(|| self.destination.first_node())
 349         }
 350 }
 351
 352 /// The destination of an onion message.
 353 #[derive(Clone)]
 354 pub enum Destination {
 355         /// We're sending this onion message to a node.
 356         Node(PublicKey),
 357         /// We're sending this onion message to a blinded path.
 358         BlindedPath(BlindedPath),
 359 }
 360
 361 impl Destination {
 362         pub(super) fn num_hops(&self) -> usize {
 363                 match self {
 364                         Destination::Node(_) => 1,
 365                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => blinded_hops.len(),
 366                 }
 367         }
 368
 369         fn first_node(&self) -> PublicKey {
 370                 match self {
 371                         Destination::Node(node_id) => *node_id,
 372                         Destination::BlindedPath(BlindedPath { introduction_node_id: node_id, .. }) => *node_id,
 373                 }
 374         }
 375 }
 376
 377 /// Result of successfully [sending an onion message].
 378 ///
 379 /// [sending an onion message]: OnionMessenger::send_onion_message
 380 #[derive(Debug, PartialEq, Eq)]
 381 pub enum SendSuccess {
 382         /// The message was buffered and will be sent once it is processed by
 383         /// [`OnionMessageHandler::next_onion_message_for_peer`].
 384         Buffered,
 385         /// The message was buffered and will be sent once the node is connected as a peer and it is
 386         /// processed by [`OnionMessageHandler::next_onion_message_for_peer`].
 387         BufferedAwaitingConnection(PublicKey),
 388 }
 389
 390 /// Errors that may occur when [sending an onion message].
 391 ///
 392 /// [sending an onion message]: OnionMessenger::send_onion_message
 393 #[derive(Debug, PartialEq, Eq)]
 394 pub enum SendError {
 395         /// Errored computing onion message packet keys.
 396         Secp256k1(secp256k1::Error),
 397         /// Because implementations such as Eclair will drop onion messages where the message packet
 398         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
 399         TooBigPacket,
 400         /// The provided [`Destination`] was an invalid [`BlindedPath`] due to not having any blinded
 401         /// hops.
 402         TooFewBlindedHops,
 403         /// The first hop is not a peer and doesn't have a known [`SocketAddress`].
 404         InvalidFirstHop(PublicKey),
 405         /// A path from the sender to the destination could not be found by the [`MessageRouter`].
 406         PathNotFound,
 407         /// Onion message contents must have a TLV type >= 64.
 408         InvalidMessage,
 409         /// Our next-hop peer's buffer was full or our total outbound buffer was full.
 410         BufferFull,
 411         /// Failed to retrieve our node id from the provided [`NodeSigner`].
 412         ///
 413         /// [`NodeSigner`]: crate::sign::NodeSigner
 414         GetNodeIdFailed,
 415         /// We attempted to send to a blinded path where we are the introduction node, and failed to
 416         /// advance the blinded path to make the second hop the new introduction node. Either
 417         /// [`NodeSigner::ecdh`] failed, we failed to tweak the current blinding point to get the
 418         /// new blinding point, or we were attempting to send to ourselves.
 419         BlindedPathAdvanceFailed,
 420 }
 421
 422 /// Handler for custom onion messages. If you are using [`SimpleArcOnionMessenger`],
 423 /// [`SimpleRefOnionMessenger`], or prefer to ignore inbound custom onion messages,
 424 /// [`IgnoringMessageHandler`] must be provided to [`OnionMessenger::new`]. Otherwise, a custom
 425 /// implementation of this trait must be provided, with [`CustomMessage`] specifying the supported
 426 /// message types.
 427 ///
 428 /// See [`OnionMessenger`] for example usage.
 429 ///
 430 /// [`IgnoringMessageHandler`]: crate::ln::peer_handler::IgnoringMessageHandler
 431 /// [`CustomMessage`]: Self::CustomMessage
 432 pub trait CustomOnionMessageHandler {
 433         /// The message known to the handler. To support multiple message types, you may want to make this
 434         /// an enum with a variant for each supported message.
 435         type CustomMessage: OnionMessageContents;
 436
 437         /// Called with the custom message that was received, returning a response to send, if any.
 438         ///
 439         /// The returned [`Self::CustomMessage`], if any, is enqueued to be sent by [`OnionMessenger`].
 440         fn handle_custom_message(&self, msg: Self::CustomMessage) -> Option<Self::CustomMessage>;
 441
 442         /// Read a custom message of type `message_type` from `buffer`, returning `Ok(None)` if the
 443         /// message type is unknown.
 444         fn read_custom_message<R: io::Read>(&self, message_type: u64, buffer: &mut R) -> Result<Option<Self::CustomMessage>, msgs::DecodeError>;
 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(not(c_bindings))]
 451         fn release_pending_custom_messages(&self) -> Vec<PendingOnionMessage<Self::CustomMessage>>;
 452
 453         /// Releases any [`Self::CustomMessage`]s that need to be sent.
 454         ///
 455         /// Typically, this is used for messages initiating a message flow rather than in response to
 456         /// another message. The latter should use the return value of [`Self::handle_custom_message`].
 457         #[cfg(c_bindings)]
 458         fn release_pending_custom_messages(&self) -> Vec<(Self::CustomMessage, Destination, Option<BlindedPath>)>;
 459 }
 460
 461 /// A processed incoming onion message, containing either a Forward (another onion message)
 462 /// or a Receive payload with decrypted contents.
 463 pub enum PeeledOnion<T: OnionMessageContents> {
 464         /// Forwarded onion, with the next node id and a new onion
 465         Forward(PublicKey, OnionMessage),
 466         /// Received onion message, with decrypted contents, path_id, and reply path
 467         Receive(ParsedOnionMessageContents<T>, Option<[u8; 32]>, Option<BlindedPath>)
 468 }
 469
 470 /// Creates an [`OnionMessage`] with the given `contents` for sending to the destination of
 471 /// `path`.
 472 ///
 473 /// Returns the node id of the peer to send the message to, the message itself, and any addresses
 474 /// need to connect to the first node.
 475 pub fn create_onion_message<ES: Deref, NS: Deref, T: OnionMessageContents>(
 476         entropy_source: &ES, node_signer: &NS, secp_ctx: &Secp256k1<secp256k1::All>,
 477         path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 478 ) -> Result<(PublicKey, OnionMessage, Option<Vec<SocketAddress>>), SendError>
 479 where
 480         ES::Target: EntropySource,
 481         NS::Target: NodeSigner,
 482 {
 483         let OnionMessagePath { intermediate_nodes, mut destination, first_node_addresses } = path;
 484         if let Destination::BlindedPath(BlindedPath { ref blinded_hops, .. }) = destination {
 485                 if blinded_hops.is_empty() {
 486                         return Err(SendError::TooFewBlindedHops);
 487                 }
 488         }
 489
 490         if contents.tlv_type() < 64 { return Err(SendError::InvalidMessage) }
 491
 492         // If we are sending straight to a blinded path and we are the introduction node, we need to
 493         // advance the blinded path by 1 hop so the second hop is the new introduction node.
 494         if intermediate_nodes.len() == 0 {
 495                 if let Destination::BlindedPath(ref mut blinded_path) = destination {
 496                         let our_node_id = node_signer.get_node_id(Recipient::Node)
 497                                 .map_err(|()| SendError::GetNodeIdFailed)?;
 498                         if blinded_path.introduction_node_id == our_node_id {
 499                                 advance_path_by_one(blinded_path, node_signer, &secp_ctx)
 500                                         .map_err(|()| SendError::BlindedPathAdvanceFailed)?;
 501                         }
 502                 }
 503         }
 504
 505         let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
 506         let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
 507         let (first_node_id, blinding_point) = if let Some(first_node_id) = intermediate_nodes.first() {
 508                 (*first_node_id, PublicKey::from_secret_key(&secp_ctx, &blinding_secret))
 509         } else {
 510                 match destination {
 511                         Destination::Node(pk) => (pk, PublicKey::from_secret_key(&secp_ctx, &blinding_secret)),
 512                         Destination::BlindedPath(BlindedPath { introduction_node_id, blinding_point, .. }) =>
 513                                 (introduction_node_id, blinding_point),
 514                 }
 515         };
 516         let (packet_payloads, packet_keys) = packet_payloads_and_keys(
 517                 &secp_ctx, &intermediate_nodes, destination, contents, reply_path, &blinding_secret)
 518                 .map_err(|e| SendError::Secp256k1(e))?;
 519
 520         let prng_seed = entropy_source.get_secure_random_bytes();
 521         let onion_routing_packet = construct_onion_message_packet(
 522                 packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
 523
 524         let message = OnionMessage { blinding_point, onion_routing_packet };
 525         Ok((first_node_id, message, first_node_addresses))
 526 }
 527
 528 /// Decode one layer of an incoming [`OnionMessage`].
 529 ///
 530 /// Returns either the next layer of the onion for forwarding or the decrypted content for the
 531 /// receiver.
 532 pub fn peel_onion_message<NS: Deref, L: Deref, CMH: Deref>(
 533         msg: &OnionMessage, secp_ctx: &Secp256k1<secp256k1::All>, node_signer: NS, logger: L,
 534         custom_handler: CMH,
 535 ) -> Result<PeeledOnion<<<CMH>::Target as CustomOnionMessageHandler>::CustomMessage>, ()>
 536 where
 537         NS::Target: NodeSigner,
 538         L::Target: Logger,
 539         CMH::Target: CustomOnionMessageHandler,
 540 {
 541         let control_tlvs_ss = match node_signer.ecdh(Recipient::Node, &msg.blinding_point, None) {
 542                 Ok(ss) => ss,
 543                 Err(e) =>  {
 544                         log_error!(logger, "Failed to retrieve node secret: {:?}", e);
 545                         return Err(());
 546                 }
 547         };
 548         let onion_decode_ss = {
 549                 let blinding_factor = {
 550                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 551                         hmac.input(control_tlvs_ss.as_ref());
 552                         Hmac::from_engine(hmac).to_byte_array()
 553                 };
 554                 match node_signer.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 555                         Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
 556                 {
 557                         Ok(ss) => ss.secret_bytes(),
 558                         Err(()) => {
 559                                 log_trace!(logger, "Failed to compute onion packet shared secret");
 560                                 return Err(());
 561                         }
 562                 }
 563         };
 564         match onion_utils::decode_next_untagged_hop(
 565                 onion_decode_ss, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 566                 (control_tlvs_ss, custom_handler.deref(), logger.deref())
 567         ) {
 568                 Ok((Payload::Receive::<ParsedOnionMessageContents<<<CMH as Deref>::Target as CustomOnionMessageHandler>::CustomMessage>> {
 569                         message, control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
 570                 }, None)) => {
 571                         Ok(PeeledOnion::Receive(message, path_id, reply_path))
 572                 },
 573                 Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 574                         next_node_id, next_blinding_override
 575                 })), Some((next_hop_hmac, new_packet_bytes)))) => {
 576                         // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 577                         // blinded hop and this onion message is destined for us. In this situation, we should keep
 578                         // unwrapping the onion layers to get to the final payload. Since we don't have the option
 579                         // of creating blinded paths with dummy hops currently, we should be ok to not handle this
 580                         // for now.
 581                         let new_pubkey = match onion_utils::next_hop_pubkey(&secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 582                                 Ok(pk) => pk,
 583                                 Err(e) => {
 584                                         log_trace!(logger, "Failed to compute next hop packet pubkey: {}", e);
 585                                         return Err(())
 586                                 }
 587                         };
 588                         let outgoing_packet = Packet {
 589                                 version: 0,
 590                                 public_key: new_pubkey,
 591                                 hop_data: new_packet_bytes,
 592                                 hmac: next_hop_hmac,
 593                         };
 594                         let onion_message = OnionMessage {
 595                                 blinding_point: match next_blinding_override {
 596                                         Some(blinding_point) => blinding_point,
 597                                         None => {
 598                                                 match onion_utils::next_hop_pubkey(
 599                                                         &secp_ctx, msg.blinding_point, control_tlvs_ss.as_ref()
 600                                                 ) {
 601                                                         Ok(bp) => bp,
 602                                                         Err(e) => {
 603                                                                 log_trace!(logger, "Failed to compute next blinding point: {}", e);
 604                                                                 return Err(())
 605                                                         }
 606                                                 }
 607                                         }
 608                                 },
 609                                 onion_routing_packet: outgoing_packet,
 610                         };
 611
 612                         Ok(PeeledOnion::Forward(next_node_id, onion_message))
 613                 },
 614                 Err(e) => {
 615                         log_trace!(logger, "Errored decoding onion message packet: {:?}", e);
 616                         Err(())
 617                 },
 618                 _ => {
 619                         log_trace!(logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 620                         Err(())
 621                 },
 622         }
 623 }
 624
 625 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref>
 626 OnionMessenger<ES, NS, L, MR, OMH, CMH>
 627 where
 628         ES::Target: EntropySource,
 629         NS::Target: NodeSigner,
 630         L::Target: Logger,
 631         MR::Target: MessageRouter,
 632         OMH::Target: OffersMessageHandler,
 633         CMH::Target: CustomOnionMessageHandler,
 634 {
 635         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
 636         /// their respective handlers.
 637         pub fn new(
 638                 entropy_source: ES, node_signer: NS, logger: L, message_router: MR, offers_handler: OMH,
 639                 custom_handler: CMH
 640         ) -> Self {
 641                 let mut secp_ctx = Secp256k1::new();
 642                 secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());
 643                 OnionMessenger {
 644                         entropy_source,
 645                         node_signer,
 646                         message_recipients: Mutex::new(HashMap::new()),
 647                         secp_ctx,
 648                         logger,
 649                         message_router,
 650                         offers_handler,
 651                         custom_handler,
 652                 }
 653         }
 654
 655         /// Sends an [`OnionMessage`] with the given `contents` to `destination`.
 656         ///
 657         /// See [`OnionMessenger`] for example usage.
 658         pub fn send_onion_message<T: OnionMessageContents>(
 659                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>
 660         ) -> Result<SendSuccess, SendError> {
 661                 self.find_path_and_enqueue_onion_message(
 662                         contents, destination, reply_path, format_args!("")
 663                 )
 664         }
 665
 666         fn find_path_and_enqueue_onion_message<T: OnionMessageContents>(
 667                 &self, contents: T, destination: Destination, reply_path: Option<BlindedPath>,
 668                 log_suffix: fmt::Arguments
 669         ) -> Result<SendSuccess, SendError> {
 670                 let result = self.find_path(destination)
 671                         .and_then(|path| self.enqueue_onion_message(path, contents, reply_path, log_suffix));
 672
 673                 match result.as_ref() {
 674                         Err(SendError::GetNodeIdFailed) => {
 675                                 log_warn!(self.logger, "Unable to retrieve node id {}", log_suffix);
 676                         },
 677                         Err(SendError::PathNotFound) => {
 678                                 log_trace!(self.logger, "Failed to find path {}", log_suffix);
 679                         },
 680                         Err(e) => {
 681                                 log_trace!(self.logger, "Failed sending onion message {}: {:?}", log_suffix, e);
 682                         },
 683                         Ok(SendSuccess::Buffered) => {
 684                                 log_trace!(self.logger, "Buffered onion message {}", log_suffix);
 685                         },
 686                         Ok(SendSuccess::BufferedAwaitingConnection(node_id)) => {
 687                                 log_trace!(
 688                                         self.logger, "Buffered onion message waiting on peer connection {}: {:?}",
 689                                         log_suffix, node_id
 690                                 );
 691                         },
 692                 }
 693
 694                 result
 695         }
 696
 697         fn find_path(&self, destination: Destination) -> Result<OnionMessagePath, SendError> {
 698                 let sender = self.node_signer
 699                         .get_node_id(Recipient::Node)
 700                         .map_err(|_| SendError::GetNodeIdFailed)?;
 701
 702                 let peers = self.message_recipients.lock().unwrap()
 703                         .iter()
 704                         .filter(|(_, recipient)| matches!(recipient, OnionMessageRecipient::ConnectedPeer(_)))
 705                         .map(|(node_id, _)| *node_id)
 706                         .collect();
 707
 708                 self.message_router
 709                         .find_path(sender, peers, destination)
 710                         .map_err(|_| SendError::PathNotFound)
 711         }
 712
 713         fn enqueue_onion_message<T: OnionMessageContents>(
 714                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>,
 715                 log_suffix: fmt::Arguments
 716         ) -> Result<SendSuccess, SendError> {
 717                 log_trace!(self.logger, "Constructing onion message {}: {:?}", log_suffix, contents);
 718
 719                 let (first_node_id, onion_message, addresses) = create_onion_message(
 720                         &self.entropy_source, &self.node_signer, &self.secp_ctx, path, contents, reply_path
 721                 )?;
 722
 723                 let mut message_recipients = self.message_recipients.lock().unwrap();
 724                 if outbound_buffer_full(&first_node_id, &message_recipients) {
 725                         return Err(SendError::BufferFull);
 726                 }
 727
 728                 match message_recipients.entry(first_node_id) {
 729                         hash_map::Entry::Vacant(e) => match addresses {
 730                                 None => Err(SendError::InvalidFirstHop(first_node_id)),
 731                                 Some(addresses) => {
 732                                         e.insert(OnionMessageRecipient::pending_connection(addresses))
 733                                                 .enqueue_message(onion_message);
 734                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 735                                 },
 736                         },
 737                         hash_map::Entry::Occupied(mut e) => {
 738                                 e.get_mut().enqueue_message(onion_message);
 739                                 if e.get().is_connected() {
 740                                         Ok(SendSuccess::Buffered)
 741                                 } else {
 742                                         Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 743                                 }
 744                         },
 745                 }
 746         }
 747
 748         #[cfg(test)]
 749         pub(super) fn send_onion_message_using_path<T: OnionMessageContents>(
 750                 &self, path: OnionMessagePath, contents: T, reply_path: Option<BlindedPath>
 751         ) -> Result<SendSuccess, SendError> {
 752                 self.enqueue_onion_message(path, contents, reply_path, format_args!(""))
 753         }
 754
 755         fn handle_onion_message_response<T: OnionMessageContents>(
 756                 &self, response: Option<T>, reply_path: Option<BlindedPath>, log_suffix: fmt::Arguments
 757         ) {
 758                 if let Some(response) = response {
 759                         match reply_path {
 760                                 Some(reply_path) => {
 761                                         let _ = self.find_path_and_enqueue_onion_message(
 762                                                 response, Destination::BlindedPath(reply_path), None, log_suffix
 763                                         );
 764                                 },
 765                                 None => {
 766                                         log_trace!(self.logger, "Missing reply path {}", log_suffix);
 767                                 },
 768                         }
 769                 }
 770         }
 771
 772         #[cfg(test)]
 773         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<OnionMessage>> {
 774                 let mut message_recipients = self.message_recipients.lock().unwrap();
 775                 let mut msgs = HashMap::new();
 776                 // We don't want to disconnect the peers by removing them entirely from the original map, so we
 777                 // release the pending message buffers individually.
 778                 for (node_id, recipient) in &mut *message_recipients {
 779                         msgs.insert(*node_id, recipient.release_pending_messages());
 780                 }
 781                 msgs
 782         }
 783 }
 784
 785 fn outbound_buffer_full(peer_node_id: &PublicKey, buffer: &HashMap<PublicKey, OnionMessageRecipient>) -> bool {
 786         const MAX_TOTAL_BUFFER_SIZE: usize = (1 << 20) * 128;
 787         const MAX_PER_PEER_BUFFER_SIZE: usize = (1 << 10) * 256;
 788         let mut total_buffered_bytes = 0;
 789         let mut peer_buffered_bytes = 0;
 790         for (pk, peer_buf) in buffer {
 791                 for om in peer_buf.pending_messages() {
 792                         let om_len = om.serialized_length();
 793                         if pk == peer_node_id {
 794                                 peer_buffered_bytes += om_len;
 795                         }
 796                         total_buffered_bytes += om_len;
 797
 798                         if total_buffered_bytes >= MAX_TOTAL_BUFFER_SIZE ||
 799                                 peer_buffered_bytes >= MAX_PER_PEER_BUFFER_SIZE
 800                         {
 801                                 return true
 802                         }
 803                 }
 804         }
 805         false
 806 }
 807
 808 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> EventsProvider
 809 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 810 where
 811         ES::Target: EntropySource,
 812         NS::Target: NodeSigner,
 813         L::Target: Logger,
 814         MR::Target: MessageRouter,
 815         OMH::Target: OffersMessageHandler,
 816         CMH::Target: CustomOnionMessageHandler,
 817 {
 818         fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
 819                 for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
 820                         if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
 821                                 if let Some(addresses) = addresses.take() {
 822                                         handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
 823                                 }
 824                         }
 825                 }
 826         }
 827 }
 828
 829 impl<ES: Deref, NS: Deref, L: Deref, MR: Deref, OMH: Deref, CMH: Deref> OnionMessageHandler
 830 for OnionMessenger<ES, NS, L, MR, OMH, CMH>
 831 where
 832         ES::Target: EntropySource,
 833         NS::Target: NodeSigner,
 834         L::Target: Logger,
 835         MR::Target: MessageRouter,
 836         OMH::Target: OffersMessageHandler,
 837         CMH::Target: CustomOnionMessageHandler,
 838 {
 839         fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &OnionMessage) {
 840                 match peel_onion_message(
 841                         msg, &self.secp_ctx, &*self.node_signer, &*self.logger, &*self.custom_handler
 842                 ) {
 843                         Ok(PeeledOnion::Receive(message, path_id, reply_path)) => {
 844                                 log_trace!(
 845                                         self.logger,
 846                                    "Received an onion message with path_id {:02x?} and {} reply_path: {:?}",
 847                                         path_id, if reply_path.is_some() { "a" } else { "no" }, message);
 848
 849                                 match message {
 850                                         ParsedOnionMessageContents::Offers(msg) => {
 851                                                 let response = self.offers_handler.handle_message(msg);
 852                                                 self.handle_onion_message_response(
 853                                                         response, reply_path, format_args!(
 854                                                                 "when responding to Offers onion message with path_id {:02x?}",
 855                                                                 path_id
 856                                                         )
 857                                                 );
 858                                         },
 859                                         ParsedOnionMessageContents::Custom(msg) => {
 860                                                 let response = self.custom_handler.handle_custom_message(msg);
 861                                                 self.handle_onion_message_response(
 862                                                         response, reply_path, format_args!(
 863                                                                 "when responding to Custom onion message with path_id {:02x?}",
 864                                                                 path_id
 865                                                         )
 866                                                 );
 867                                         },
 868                                 }
 869                         },
 870                         Ok(PeeledOnion::Forward(next_node_id, onion_message)) => {
 871                                 let mut message_recipients = self.message_recipients.lock().unwrap();
 872                                 if outbound_buffer_full(&next_node_id, &message_recipients) {
 873                                         log_trace!(self.logger, "Dropping forwarded onion message to peer {:?}: outbound buffer full", next_node_id);
 874                                         return
 875                                 }
 876
 877                                 #[cfg(fuzzing)]
 878                                 message_recipients
 879                                         .entry(next_node_id)
 880                                         .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()));
 881
 882                                 match message_recipients.entry(next_node_id) {
 883                                         hash_map::Entry::Occupied(mut e) if matches!(
 884                                                 e.get(), OnionMessageRecipient::ConnectedPeer(..)
 885                                         ) => {
 886                                                 e.get_mut().enqueue_message(onion_message);
 887                                                 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
 888                                         },
 889                                         _ => {
 890                                                 log_trace!(self.logger, "Dropping forwarded onion message to disconnected peer {:?}", next_node_id);
 891                                                 return
 892                                         },
 893                                 }
 894                         },
 895                         Err(e) => {
 896                                 log_error!(self.logger, "Failed to process onion message {:?}", e);
 897                         }
 898                 }
 899         }
 900
 901         fn peer_connected(&self, their_node_id: &PublicKey, init: &msgs::Init, _inbound: bool) -> Result<(), ()> {
 902                 if init.features.supports_onion_messages() {
 903                         self.message_recipients.lock().unwrap()
 904                                 .entry(*their_node_id)
 905                                 .or_insert_with(|| OnionMessageRecipient::ConnectedPeer(VecDeque::new()))
 906                                 .mark_connected();
 907                 } else {
 908                         self.message_recipients.lock().unwrap().remove(their_node_id);
 909                 }
 910
 911                 Ok(())
 912         }
 913
 914         fn peer_disconnected(&self, their_node_id: &PublicKey) {
 915                 match self.message_recipients.lock().unwrap().remove(their_node_id) {
 916                         Some(OnionMessageRecipient::ConnectedPeer(..)) => {},
 917                         Some(_) => debug_assert!(false),
 918                         None => {},
 919                 }
 920         }
 921
 922         fn timer_tick_occurred(&self) {
 923                 let mut message_recipients = self.message_recipients.lock().unwrap();
 924
 925                 // Drop any pending recipients since the last call to avoid retaining buffered messages for
 926                 // too long.
 927                 message_recipients.retain(|_, recipient| match recipient {
 928                         OnionMessageRecipient::PendingConnection(_, None, ticks) => *ticks < MAX_TIMER_TICKS,
 929                         OnionMessageRecipient::PendingConnection(_, Some(_), _) => true,
 930                         _ => true,
 931                 });
 932
 933                 // Increment a timer tick for pending recipients so that their buffered messages are dropped
 934                 // at MAX_TIMER_TICKS.
 935                 for recipient in message_recipients.values_mut() {
 936                         if let OnionMessageRecipient::PendingConnection(_, None, ticks) = recipient {
 937                                 *ticks += 1;
 938                         }
 939                 }
 940         }
 941
 942         fn provided_node_features(&self) -> NodeFeatures {
 943                 let mut features = NodeFeatures::empty();
 944                 features.set_onion_messages_optional();
 945                 features
 946         }
 947
 948         fn provided_init_features(&self, _their_node_id: &PublicKey) -> InitFeatures {
 949                 let mut features = InitFeatures::empty();
 950                 features.set_onion_messages_optional();
 951                 features
 952         }
 953
 954         // Before returning any messages to send for the peer, this method will see if any messages were
 955         // enqueued in the handler by users, find a path to the corresponding blinded path's introduction
 956         // node, and then enqueue the message for sending to the first peer in the full path.
 957         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<OnionMessage> {
 958                 // Enqueue any initiating `OffersMessage`s to send.
 959                 for message in self.offers_handler.release_pending_messages() {
 960                         #[cfg(not(c_bindings))]
 961                         let PendingOnionMessage { contents, destination, reply_path } = message;
 962                         #[cfg(c_bindings)]
 963                         let (contents, destination, reply_path) = message;
 964                         let _ = self.find_path_and_enqueue_onion_message(
 965                                 contents, destination, reply_path, format_args!("when sending OffersMessage")
 966                         );
 967                 }
 968
 969                 // Enqueue any initiating `CustomMessage`s to send.
 970                 for message in self.custom_handler.release_pending_custom_messages() {
 971                         #[cfg(not(c_bindings))]
 972                         let PendingOnionMessage { contents, destination, reply_path } = message;
 973                         #[cfg(c_bindings)]
 974                         let (contents, destination, reply_path) = message;
 975                         let _ = self.find_path_and_enqueue_onion_message(
 976                                 contents, destination, reply_path, format_args!("when sending CustomMessage")
 977                         );
 978                 }
 979
 980                 self.message_recipients.lock().unwrap()
 981                         .get_mut(&peer_node_id)
 982                         .and_then(|buffer| buffer.dequeue_message())
 983         }
 984 }
 985
 986 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
 987 // produces
 988 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
 989 /// [`SimpleArcPeerManager`]. See their docs for more details.
 990 ///
 991 /// This is not exported to bindings users as type aliases aren't supported in most languages.
 992 ///
 993 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 994 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
 995 #[cfg(not(c_bindings))]
 996 pub type SimpleArcOnionMessenger<M, T, F, L> = OnionMessenger<
 997         Arc<KeysManager>,
 998         Arc<KeysManager>,
 999         Arc<L>,
1000         Arc<DefaultMessageRouter<Arc<NetworkGraph<Arc<L>>>, Arc<L>>>,
1001         Arc<SimpleArcChannelManager<M, T, F, L>>,
1002         IgnoringMessageHandler
1003 >;
1004
1005 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
1006 /// [`SimpleRefPeerManager`]. See their docs for more details.
1007 ///
1008 /// This is not exported to bindings users as type aliases aren't supported in most languages.
1009 ///
1010 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
1011 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
1012 #[cfg(not(c_bindings))]
1013 pub type SimpleRefOnionMessenger<
1014         'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, M, T, F, L
1015 > = OnionMessenger<
1016         &'a KeysManager,
1017         &'a KeysManager,
1018         &'b L,
1019         &'i DefaultMessageRouter<&'g NetworkGraph<&'b L>, &'b L>,
1020         &'j SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, M, T, F, L>,
1021         IgnoringMessageHandler
1022 >;
1023
1024 /// Construct onion packet payloads and keys for sending an onion message along the given
1025 /// `unblinded_path` to the given `destination`.
1026 fn packet_payloads_and_keys<T: OnionMessageContents, S: secp256k1::Signing + secp256k1::Verification>(
1027         secp_ctx: &Secp256k1<S>, unblinded_path: &[PublicKey], destination: Destination, message: T,
1028         mut reply_path: Option<BlindedPath>, session_priv: &SecretKey
1029 ) -> Result<(Vec<(Payload<T>, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
1030         let num_hops = unblinded_path.len() + destination.num_hops();
1031         let mut payloads = Vec::with_capacity(num_hops);
1032         let mut onion_packet_keys = Vec::with_capacity(num_hops);
1033
1034         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedPath(BlindedPath {
1035                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
1036                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
1037         let num_unblinded_hops = num_hops - num_blinded_hops;
1038
1039         let mut unblinded_path_idx = 0;
1040         let mut blinded_path_idx = 0;
1041         let mut prev_control_tlvs_ss = None;
1042         let mut final_control_tlvs = None;
1043         utils::construct_keys_callback(secp_ctx, unblinded_path.iter(), Some(destination), session_priv,
1044                 |_, onion_packet_ss, ephemeral_pubkey, control_tlvs_ss, unblinded_pk_opt, enc_payload_opt| {
1045                         if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
1046                                 if let Some(ss) = prev_control_tlvs_ss.take() {
1047                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
1048                                                 ForwardTlvs {
1049                                                         next_node_id: unblinded_pk_opt.unwrap(),
1050                                                         next_blinding_override: None,
1051                                                 }
1052                                         )), ss));
1053                                 }
1054                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1055                                 unblinded_path_idx += 1;
1056                         } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
1057                                 if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
1058                                         payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
1059                                                 next_node_id: intro_node_id,
1060                                                 next_blinding_override: Some(blinding_pt),
1061                                         })), control_tlvs_ss));
1062                                 }
1063                         }
1064                         if blinded_path_idx < num_blinded_hops.saturating_sub(1) && enc_payload_opt.is_some() {
1065                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
1066                                         control_tlvs_ss));
1067                                 blinded_path_idx += 1;
1068                         } else if let Some(encrypted_payload) = enc_payload_opt {
1069                                 final_control_tlvs = Some(ReceiveControlTlvs::Blinded(encrypted_payload));
1070                                 prev_control_tlvs_ss = Some(control_tlvs_ss);
1071                         }
1072
1073                         let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
1074                         onion_packet_keys.push(onion_utils::OnionKeys {
1075                                 #[cfg(test)]
1076                                 shared_secret: onion_packet_ss,
1077                                 #[cfg(test)]
1078                                 blinding_factor: [0; 32],
1079                                 ephemeral_pubkey,
1080                                 rho,
1081                                 mu,
1082                         });
1083                 }
1084         )?;
1085
1086         if let Some(control_tlvs) = final_control_tlvs {
1087                 payloads.push((Payload::Receive {
1088                         control_tlvs,
1089                         reply_path: reply_path.take(),
1090                         message,
1091                 }, prev_control_tlvs_ss.unwrap()));
1092         } else {
1093                 payloads.push((Payload::Receive {
1094                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
1095                         reply_path: reply_path.take(),
1096                         message,
1097                 }, prev_control_tlvs_ss.unwrap()));
1098         }
1099
1100         Ok((payloads, onion_packet_keys))
1101 }
1102
1103 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
1104 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, ()> {
1105         // Spec rationale:
1106         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
1107         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
1108         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
1109         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
1110         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
1111                 SMALL_PACKET_HOP_DATA_LEN
1112         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
1113                 BIG_PACKET_HOP_DATA_LEN
1114         } else { return Err(()) };
1115
1116         onion_utils::construct_onion_message_packet::<_, _>(
1117                 payloads, onion_keys, prng_seed, hop_data_len)
1118 }