_ 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, Secp256k1, SecretKey};
  17
  18 use chain::keysinterface::{InMemorySigner, KeysInterface, KeysManager, Recipient, Sign};
  19 use ln::msgs;
  20 use ln::onion_utils;
  21 use super::blinded_route::{BlindedRoute, ForwardTlvs, ReceiveTlvs};
  22 use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload, ReceiveControlTlvs, SMALL_PACKET_HOP_DATA_LEN};
  23 use super::utils;
  24 use util::logger::Logger;
  25
  26 use core::ops::Deref;
  27 use sync::{Arc, Mutex};
  28 use prelude::*;
  29
  30 /// A sender, receiver and forwarder of onion messages. In upcoming releases, this object will be
  31 /// used to retrieve invoices and fulfill invoice requests from [offers].
  32 ///
  33 /// [offers]: <https://github.com/lightning/bolts/pull/798>
  34 pub struct OnionMessenger<Signer: Sign, K: Deref, L: Deref>
  35         where K::Target: KeysInterface<Signer = Signer>,
  36               L::Target: Logger,
  37 {
  38         keys_manager: K,
  39         logger: L,
  40         pending_messages: Mutex<HashMap<PublicKey, Vec<msgs::OnionMessage>>>,
  41         secp_ctx: Secp256k1<secp256k1::All>,
  42         // Coming soon:
  43         // invoice_handler: InvoiceHandler,
  44         // custom_handler: CustomHandler, // handles custom onion messages
  45 }
  46
  47 /// The destination of an onion message.
  48 pub enum Destination {
  49         /// We're sending this onion message to a node.
  50         Node(PublicKey),
  51         /// We're sending this onion message to a blinded route.
  52         BlindedRoute(BlindedRoute),
  53 }
  54
  55 impl Destination {
  56         pub(super) fn num_hops(&self) -> usize {
  57                 match self {
  58                         Destination::Node(_) => 1,
  59                         Destination::BlindedRoute(BlindedRoute { blinded_hops, .. }) => blinded_hops.len(),
  60                 }
  61         }
  62 }
  63
  64 impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
  65         where K::Target: KeysInterface<Signer = Signer>,
  66               L::Target: Logger,
  67 {
  68         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
  69         /// their respective handlers.
  70         pub fn new(keys_manager: K, logger: L) -> Self {
  71                 let mut secp_ctx = Secp256k1::new();
  72                 secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
  73                 OnionMessenger {
  74                         keys_manager,
  75                         pending_messages: Mutex::new(HashMap::new()),
  76                         secp_ctx,
  77                         logger,
  78                 }
  79         }
  80
  81         /// Send an empty onion message to `destination`, routing it through `intermediate_nodes`.
  82         pub fn send_onion_message(&self, intermediate_nodes: &[PublicKey], destination: Destination) -> Result<(), secp256k1::Error> {
  83                 let blinding_secret_bytes = self.keys_manager.get_secure_random_bytes();
  84                 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
  85                 let (introduction_node_id, blinding_point) = if intermediate_nodes.len() != 0 {
  86                         (intermediate_nodes[0], PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret))
  87                 } else {
  88                         match destination {
  89                                 Destination::Node(pk) => (pk, PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret)),
  90                                 Destination::BlindedRoute(BlindedRoute { introduction_node_id, blinding_point, .. }) =>
  91                                         (introduction_node_id, blinding_point),
  92                         }
  93                 };
  94                 let (packet_payloads, packet_keys) = packet_payloads_and_keys(
  95                         &self.secp_ctx, intermediate_nodes, destination, &blinding_secret)?;
  96
  97                 let prng_seed = self.keys_manager.get_secure_random_bytes();
  98                 let onion_packet = construct_onion_message_packet(packet_payloads, packet_keys, prng_seed);
  99
 100                 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
 101                 let pending_msgs = pending_per_peer_msgs.entry(introduction_node_id).or_insert(Vec::new());
 102                 pending_msgs.push(
 103                         msgs::OnionMessage {
 104                                 blinding_point,
 105                                 onion_routing_packet: onion_packet,
 106                         }
 107                 );
 108                 Ok(())
 109         }
 110
 111         /// Handle an incoming onion message. Currently, if a message was destined for us we will log, but
 112         /// soon we'll delegate the onion message to a handler that can generate invoices or send
 113         /// payments.
 114         pub fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
 115                 let control_tlvs_ss = match self.keys_manager.ecdh(Recipient::Node, &msg.blinding_point, None) {
 116                         Ok(ss) => ss,
 117                         Err(e) =>  {
 118                                 log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
 119                                 return
 120                         }
 121                 };
 122                 let onion_decode_ss = {
 123                         let blinding_factor = {
 124                                 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 125                                 hmac.input(control_tlvs_ss.as_ref());
 126                                 Hmac::from_engine(hmac).into_inner()
 127                         };
 128                         match self.keys_manager.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
 129                                 Some(&blinding_factor))
 130                         {
 131                                 Ok(ss) => ss.secret_bytes(),
 132                                 Err(()) => {
 133                                         log_trace!(self.logger, "Failed to compute onion packet shared secret");
 134                                         return
 135                                 }
 136                         }
 137                 };
 138                 match onion_utils::decode_next_hop(onion_decode_ss, &msg.onion_routing_packet.hop_data[..],
 139                         msg.onion_routing_packet.hmac, control_tlvs_ss)
 140                 {
 141                         Ok((Payload::Receive {
 142                                 control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id })
 143                         }, None)) => {
 144                                 log_info!(self.logger, "Received an onion message with path_id: {:02x?}", path_id);
 145                         },
 146                         Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 147                                 next_node_id, next_blinding_override
 148                         })), Some((next_hop_hmac, new_packet_bytes)))) => {
 149                                 // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
 150                                 // blinded hop and this onion message is destined for us. In this situation, we should keep
 151                                 // unwrapping the onion layers to get to the final payload. Since we don't have the option
 152                                 // of creating blinded routes with dummy hops currently, we should be ok to not handle this
 153                                 // for now.
 154                                 let new_pubkey = match onion_utils::next_hop_packet_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
 155                                         Ok(pk) => pk,
 156                                         Err(e) => {
 157                                                 log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
 158                                                 return
 159                                         }
 160                                 };
 161                                 let outgoing_packet = Packet {
 162                                         version: 0,
 163                                         public_key: new_pubkey,
 164                                         hop_data: new_packet_bytes,
 165                                         hmac: next_hop_hmac,
 166                                 };
 167
 168                                 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
 169                                 let pending_msgs = pending_per_peer_msgs.entry(next_node_id).or_insert(Vec::new());
 170                                 pending_msgs.push(
 171                                         msgs::OnionMessage {
 172                                                 blinding_point: match next_blinding_override {
 173                                                         Some(blinding_point) => blinding_point,
 174                                                         None => {
 175                                                                 let blinding_factor = {
 176                                                                         let mut sha = Sha256::engine();
 177                                                                         sha.input(&msg.blinding_point.serialize()[..]);
 178                                                                         sha.input(control_tlvs_ss.as_ref());
 179                                                                         Sha256::from_engine(sha).into_inner()
 180                                                                 };
 181                                                                 let mut next_blinding_point = msg.blinding_point;
 182                                                                 if let Err(e) = next_blinding_point.mul_assign(&self.secp_ctx, &blinding_factor[..]) {
 183                                                                         log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
 184                                                                         return
 185                                                                 }
 186                                                                 next_blinding_point
 187                                                         },
 188                                                 },
 189                                                 onion_routing_packet: outgoing_packet,
 190                                         },
 191                                 );
 192                         },
 193                         Err(e) => {
 194                                 log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
 195                         },
 196                         _ => {
 197                                 log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
 198                         },
 199                 };
 200         }
 201 }
 202
 203 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
 204 // produces
 205 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
 206 /// [`SimpleArcPeerManager`]. See their docs for more details.
 207 ///
 208 ///[`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 209 ///[`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
 210 pub type SimpleArcOnionMessenger<L> = OnionMessenger<InMemorySigner, Arc<KeysManager>, Arc<L>>;
 211 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
 212 /// [`SimpleRefPeerManager`]. See their docs for more details.
 213 ///
 214 ///[`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
 215 ///[`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
 216 pub type SimpleRefOnionMessenger<'a, 'b, L> = OnionMessenger<InMemorySigner, &'a KeysManager, &'b L>;
 217
 218 /// Construct onion packet payloads and keys for sending an onion message along the given
 219 /// `unblinded_path` to the given `destination`.
 220 fn packet_payloads_and_keys<T: secp256k1::Signing + secp256k1::Verification>(
 221         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Destination, session_priv: &SecretKey
 222 ) -> Result<(Vec<(Payload, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
 223         let num_hops = unblinded_path.len() + destination.num_hops();
 224         let mut payloads = Vec::with_capacity(num_hops);
 225         let mut onion_packet_keys = Vec::with_capacity(num_hops);
 226
 227         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedRoute(BlindedRoute {
 228                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
 229                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
 230         let num_unblinded_hops = num_hops - num_blinded_hops;
 231
 232         let mut unblinded_path_idx = 0;
 233         let mut blinded_path_idx = 0;
 234         let mut prev_control_tlvs_ss = None;
 235         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| {
 236                 if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
 237                         if let Some(ss) = prev_control_tlvs_ss.take() {
 238                                 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
 239                                         ForwardTlvs {
 240                                                 next_node_id: unblinded_pk_opt.unwrap(),
 241                                                 next_blinding_override: None,
 242                                         }
 243                                 )), ss));
 244                         }
 245                         prev_control_tlvs_ss = Some(control_tlvs_ss);
 246                         unblinded_path_idx += 1;
 247                 } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
 248                         if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
 249                                 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
 250                                         next_node_id: intro_node_id,
 251                                         next_blinding_override: Some(blinding_pt),
 252                                 })), control_tlvs_ss));
 253                         }
 254                         if let Some(encrypted_payload) = enc_payload_opt {
 255                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(encrypted_payload)),
 256                                         control_tlvs_ss));
 257                         } else { debug_assert!(false); }
 258                         blinded_path_idx += 1;
 259                 } else if blinded_path_idx < num_blinded_hops - 1 && enc_payload_opt.is_some() {
 260                         payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
 261                                 control_tlvs_ss));
 262                         blinded_path_idx += 1;
 263                 } else if let Some(encrypted_payload) = enc_payload_opt {
 264                         payloads.push((Payload::Receive {
 265                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_payload),
 266                         }, control_tlvs_ss));
 267                 }
 268
 269                 let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
 270                 onion_packet_keys.push(onion_utils::OnionKeys {
 271                         #[cfg(test)]
 272                         shared_secret: onion_packet_ss,
 273                         #[cfg(test)]
 274                         blinding_factor: [0; 32],
 275                         ephemeral_pubkey,
 276                         rho,
 277                         mu,
 278                 });
 279         })?;
 280
 281         if let Some(control_tlvs_ss) = prev_control_tlvs_ss {
 282                 payloads.push((Payload::Receive {
 283                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, })
 284                 }, control_tlvs_ss));
 285         }
 286
 287         Ok((payloads, onion_packet_keys))
 288 }
 289
 290 fn construct_onion_message_packet(payloads: Vec<(Payload, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Packet {
 291         // Spec rationale:
 292         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
 293         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
 294         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
 295         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
 296         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
 297                 SMALL_PACKET_HOP_DATA_LEN
 298         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
 299                 BIG_PACKET_HOP_DATA_LEN
 300         } else { payloads_ser_len };
 301
 302         onion_utils::construct_onion_message_packet::<_, _>(payloads, onion_keys, prng_seed, hop_data_len)
 303 }