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