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Expose onion message module as public
[rust-lightning] / 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 chain::keysinterface::{InMemorySigner, KeysInterface, KeysManager, Recipient, Sign};
19 use ln::msgs::{self, OnionMessageHandler};
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::events::OnionMessageProvider;
25 use util::logger::Logger;
26
27 use core::ops::Deref;
28 use sync::{Arc, Mutex};
29 use prelude::*;
30
31 /// A sender, receiver and forwarder of onion messages. In upcoming releases, this object will be
32 /// used to retrieve invoices and fulfill invoice requests from [offers]. Currently, only sending
33 /// and receiving empty onion messages is supported.
34 ///
35 /// # Example
36 ///
37 /// ```
38 /// # extern crate bitcoin;
39 /// # use bitcoin::hashes::_export::_core::time::Duration;
40 /// # use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
41 /// # use lightning::chain::keysinterface::{InMemorySigner, KeysManager, KeysInterface};
42 /// # use lightning::onion_message::{BlindedRoute, Destination, OnionMessenger};
43 /// # use lightning::util::logger::{Logger, Record};
44 /// # use std::sync::Arc;
45 /// # struct FakeLogger {};
46 /// # impl Logger for FakeLogger {
47 /// #     fn log(&self, record: &Record) { unimplemented!() }
48 /// # }
49 /// # let seed = [42u8; 32];
50 /// # let time = Duration::from_secs(123456);
51 /// # let keys_manager = KeysManager::new(&seed, time.as_secs(), time.subsec_nanos());
52 /// # let logger = Arc::new(FakeLogger {});
53 /// # let node_secret = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
54 /// # let secp_ctx = Secp256k1::new();
55 /// # let hop_node_id1 = PublicKey::from_secret_key(&secp_ctx, &node_secret);
56 /// # let (hop_node_id2, hop_node_id3, hop_node_id4) = (hop_node_id1, hop_node_id1,
57 /// hop_node_id1);
58 /// # let destination_node_id = hop_node_id1;
59 /// #
60 /// // Create the onion messenger. This must use the same `keys_manager` as is passed to your
61 /// // ChannelManager.
62 /// let onion_messenger = OnionMessenger::new(&keys_manager, logger);
63 ///
64 /// // Send an empty onion message to a node id.
65 /// let intermediate_hops = [hop_node_id1, hop_node_id2];
66 /// let reply_path = None;
67 /// onion_messenger.send_onion_message(&intermediate_hops, Destination::Node(destination_node_id), reply_path);
68 ///
69 /// // Create a blinded route to yourself, for someone to send an onion message to.
70 /// # let your_node_id = hop_node_id1;
71 /// let hops = [hop_node_id3, hop_node_id4, your_node_id];
72 /// let blinded_route = BlindedRoute::new::<InMemorySigner, _, _>(&hops, &keys_manager, &secp_ctx).unwrap();
73 ///
74 /// // Send an empty onion message to a blinded route.
75 /// # let intermediate_hops = [hop_node_id1, hop_node_id2];
76 /// let reply_path = None;
77 /// onion_messenger.send_onion_message(&intermediate_hops, Destination::BlindedRoute(blinded_route), reply_path);
78 /// ```
79 ///
80 /// [offers]: <https://github.com/lightning/bolts/pull/798>
81 /// [`OnionMessenger`]: crate::onion_message::OnionMessenger
82 pub struct OnionMessenger<Signer: Sign, K: Deref, L: Deref>
83         where K::Target: KeysInterface<Signer = Signer>,
84               L::Target: Logger,
85 {
86         keys_manager: K,
87         logger: L,
88         pending_messages: Mutex<HashMap<PublicKey, VecDeque<msgs::OnionMessage>>>,
89         secp_ctx: Secp256k1<secp256k1::All>,
90         // Coming soon:
91         // invoice_handler: InvoiceHandler,
92         // custom_handler: CustomHandler, // handles custom onion messages
93 }
94
95 /// The destination of an onion message.
96 pub enum Destination {
97         /// We're sending this onion message to a node.
98         Node(PublicKey),
99         /// We're sending this onion message to a blinded route.
100         BlindedRoute(BlindedRoute),
101 }
102
103 impl Destination {
104         pub(super) fn num_hops(&self) -> usize {
105                 match self {
106                         Destination::Node(_) => 1,
107                         Destination::BlindedRoute(BlindedRoute { blinded_hops, .. }) => blinded_hops.len(),
108                 }
109         }
110 }
111
112 /// Errors that may occur when [sending an onion message].
113 ///
114 /// [sending an onion message]: OnionMessenger::send_onion_message
115 #[derive(Debug, PartialEq)]
116 pub enum SendError {
117         /// Errored computing onion message packet keys.
118         Secp256k1(secp256k1::Error),
119         /// Because implementations such as Eclair will drop onion messages where the message packet
120         /// exceeds 32834 bytes, we refuse to send messages where the packet exceeds this size.
121         TooBigPacket,
122         /// The provided [`Destination`] was an invalid [`BlindedRoute`], due to having fewer than two
123         /// blinded hops.
124         TooFewBlindedHops,
125 }
126
127 impl<Signer: Sign, K: Deref, L: Deref> OnionMessenger<Signer, K, L>
128         where K::Target: KeysInterface<Signer = Signer>,
129               L::Target: Logger,
130 {
131         /// Constructs a new `OnionMessenger` to send, forward, and delegate received onion messages to
132         /// their respective handlers.
133         pub fn new(keys_manager: K, logger: L) -> Self {
134                 let mut secp_ctx = Secp256k1::new();
135                 secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());
136                 OnionMessenger {
137                         keys_manager,
138                         pending_messages: Mutex::new(HashMap::new()),
139                         secp_ctx,
140                         logger,
141                 }
142         }
143
144         /// Send an empty onion message to `destination`, routing it through `intermediate_nodes`.
145         /// See [`OnionMessenger`] for example usage.
146         pub fn send_onion_message(&self, intermediate_nodes: &[PublicKey], destination: Destination, reply_path: Option<BlindedRoute>) -> Result<(), SendError> {
147                 if let Destination::BlindedRoute(BlindedRoute { ref blinded_hops, .. }) = destination {
148                         if blinded_hops.len() < 2 {
149                                 return Err(SendError::TooFewBlindedHops);
150                         }
151                 }
152                 let blinding_secret_bytes = self.keys_manager.get_secure_random_bytes();
153                 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
154                 let (introduction_node_id, blinding_point) = if intermediate_nodes.len() != 0 {
155                         (intermediate_nodes[0], PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret))
156                 } else {
157                         match destination {
158                                 Destination::Node(pk) => (pk, PublicKey::from_secret_key(&self.secp_ctx, &blinding_secret)),
159                                 Destination::BlindedRoute(BlindedRoute { introduction_node_id, blinding_point, .. }) =>
160                                         (introduction_node_id, blinding_point),
161                         }
162                 };
163                 let (packet_payloads, packet_keys) = packet_payloads_and_keys(
164                         &self.secp_ctx, intermediate_nodes, destination, reply_path, &blinding_secret)
165                         .map_err(|e| SendError::Secp256k1(e))?;
166
167                 let prng_seed = self.keys_manager.get_secure_random_bytes();
168                 let onion_packet = construct_onion_message_packet(
169                         packet_payloads, packet_keys, prng_seed).map_err(|()| SendError::TooBigPacket)?;
170
171                 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
172                 let pending_msgs = pending_per_peer_msgs.entry(introduction_node_id).or_insert_with(VecDeque::new);
173                 pending_msgs.push_back(
174                         msgs::OnionMessage {
175                                 blinding_point,
176                                 onion_routing_packet: onion_packet,
177                         }
178                 );
179                 Ok(())
180         }
181
182         #[cfg(test)]
183         pub(super) fn release_pending_msgs(&self) -> HashMap<PublicKey, VecDeque<msgs::OnionMessage>> {
184                 let mut pending_msgs = self.pending_messages.lock().unwrap();
185                 let mut msgs = HashMap::new();
186                 core::mem::swap(&mut *pending_msgs, &mut msgs);
187                 msgs
188         }
189 }
190
191 impl<Signer: Sign, K: Deref, L: Deref> OnionMessageHandler for OnionMessenger<Signer, K, L>
192         where K::Target: KeysInterface<Signer = Signer>,
193               L::Target: Logger,
194 {
195         /// Handle an incoming onion message. Currently, if a message was destined for us we will log, but
196         /// soon we'll delegate the onion message to a handler that can generate invoices or send
197         /// payments.
198         fn handle_onion_message(&self, _peer_node_id: &PublicKey, msg: &msgs::OnionMessage) {
199                 let control_tlvs_ss = match self.keys_manager.ecdh(Recipient::Node, &msg.blinding_point, None) {
200                         Ok(ss) => ss,
201                         Err(e) =>  {
202                                 log_error!(self.logger, "Failed to retrieve node secret: {:?}", e);
203                                 return
204                         }
205                 };
206                 let onion_decode_ss = {
207                         let blinding_factor = {
208                                 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
209                                 hmac.input(control_tlvs_ss.as_ref());
210                                 Hmac::from_engine(hmac).into_inner()
211                         };
212                         match self.keys_manager.ecdh(Recipient::Node, &msg.onion_routing_packet.public_key,
213                                 Some(&Scalar::from_be_bytes(blinding_factor).unwrap()))
214                         {
215                                 Ok(ss) => ss.secret_bytes(),
216                                 Err(()) => {
217                                         log_trace!(self.logger, "Failed to compute onion packet shared secret");
218                                         return
219                                 }
220                         }
221                 };
222                 match onion_utils::decode_next_hop(onion_decode_ss, &msg.onion_routing_packet.hop_data[..],
223                         msg.onion_routing_packet.hmac, control_tlvs_ss)
224                 {
225                         Ok((Payload::Receive {
226                                 control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id }), reply_path,
227                         }, None)) => {
228                                 log_info!(self.logger,
229                                         "Received an onion message with path_id: {:02x?} and {}reply_path",
230                                                 path_id, if reply_path.is_some() { "" } else { "no " });
231                         },
232                         Ok((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
233                                 next_node_id, next_blinding_override
234                         })), Some((next_hop_hmac, new_packet_bytes)))) => {
235                                 // TODO: we need to check whether `next_node_id` is our node, in which case this is a dummy
236                                 // blinded hop and this onion message is destined for us. In this situation, we should keep
237                                 // unwrapping the onion layers to get to the final payload. Since we don't have the option
238                                 // of creating blinded routes with dummy hops currently, we should be ok to not handle this
239                                 // for now.
240                                 let new_pubkey = match onion_utils::next_hop_packet_pubkey(&self.secp_ctx, msg.onion_routing_packet.public_key, &onion_decode_ss) {
241                                         Ok(pk) => pk,
242                                         Err(e) => {
243                                                 log_trace!(self.logger, "Failed to compute next hop packet pubkey: {}", e);
244                                                 return
245                                         }
246                                 };
247                                 let outgoing_packet = Packet {
248                                         version: 0,
249                                         public_key: new_pubkey,
250                                         hop_data: new_packet_bytes,
251                                         hmac: next_hop_hmac,
252                                 };
253
254                                 let mut pending_per_peer_msgs = self.pending_messages.lock().unwrap();
255                                 let pending_msgs = pending_per_peer_msgs.entry(next_node_id).or_insert_with(VecDeque::new);
256                                 pending_msgs.push_back(
257                                         msgs::OnionMessage {
258                                                 blinding_point: match next_blinding_override {
259                                                         Some(blinding_point) => blinding_point,
260                                                         None => {
261                                                                 let blinding_factor = {
262                                                                         let mut sha = Sha256::engine();
263                                                                         sha.input(&msg.blinding_point.serialize()[..]);
264                                                                         sha.input(control_tlvs_ss.as_ref());
265                                                                         Sha256::from_engine(sha).into_inner()
266                                                                 };
267                                                                 let next_blinding_point = msg.blinding_point;
268                                                                 match next_blinding_point.mul_tweak(&self.secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap()) {
269                                                                         Ok(bp) => bp,
270                                                                         Err(e) => {
271                                                                                 log_trace!(self.logger, "Failed to compute next blinding point: {}", e);
272                                                                                 return
273                                                                         }
274                                                                 }
275                                                         },
276                                                 },
277                                                 onion_routing_packet: outgoing_packet,
278                                         },
279                                 );
280                                 log_trace!(self.logger, "Forwarding an onion message to peer {}", next_node_id);
281                         },
282                         Err(e) => {
283                                 log_trace!(self.logger, "Errored decoding onion message packet: {:?}", e);
284                         },
285                         _ => {
286                                 log_trace!(self.logger, "Received bogus onion message packet, either the sender encoded a final hop as a forwarding hop or vice versa");
287                         },
288                 };
289         }
290 }
291
292 impl<Signer: Sign, K: Deref, L: Deref> OnionMessageProvider for OnionMessenger<Signer, K, L>
293         where K::Target: KeysInterface<Signer = Signer>,
294               L::Target: Logger,
295 {
296         fn next_onion_message_for_peer(&self, peer_node_id: PublicKey) -> Option<msgs::OnionMessage> {
297                 let mut pending_msgs = self.pending_messages.lock().unwrap();
298                 if let Some(msgs) = pending_msgs.get_mut(&peer_node_id) {
299                         return msgs.pop_front()
300                 }
301                 None
302         }
303 }
304
305 // TODO: parameterize the below Simple* types with OnionMessenger and handle the messages it
306 // produces
307 /// Useful for simplifying the parameters of [`SimpleArcChannelManager`] and
308 /// [`SimpleArcPeerManager`]. See their docs for more details.
309 ///
310 ///[`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
311 ///[`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
312 pub type SimpleArcOnionMessenger<L> = OnionMessenger<InMemorySigner, Arc<KeysManager>, Arc<L>>;
313 /// Useful for simplifying the parameters of [`SimpleRefChannelManager`] and
314 /// [`SimpleRefPeerManager`]. See their docs for more details.
315 ///
316 ///[`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
317 ///[`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
318 pub type SimpleRefOnionMessenger<'a, 'b, L> = OnionMessenger<InMemorySigner, &'a KeysManager, &'b L>;
319
320 /// Construct onion packet payloads and keys for sending an onion message along the given
321 /// `unblinded_path` to the given `destination`.
322 fn packet_payloads_and_keys<T: secp256k1::Signing + secp256k1::Verification>(
323         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Destination, mut reply_path:
324         Option<BlindedRoute>, session_priv: &SecretKey
325 ) -> Result<(Vec<(Payload, [u8; 32])>, Vec<onion_utils::OnionKeys>), secp256k1::Error> {
326         let num_hops = unblinded_path.len() + destination.num_hops();
327         let mut payloads = Vec::with_capacity(num_hops);
328         let mut onion_packet_keys = Vec::with_capacity(num_hops);
329
330         let (mut intro_node_id_blinding_pt, num_blinded_hops) = if let Destination::BlindedRoute(BlindedRoute {
331                 introduction_node_id, blinding_point, blinded_hops }) = &destination {
332                 (Some((*introduction_node_id, *blinding_point)), blinded_hops.len()) } else { (None, 0) };
333         let num_unblinded_hops = num_hops - num_blinded_hops;
334
335         let mut unblinded_path_idx = 0;
336         let mut blinded_path_idx = 0;
337         let mut prev_control_tlvs_ss = None;
338         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| {
339                 if num_unblinded_hops != 0 && unblinded_path_idx < num_unblinded_hops {
340                         if let Some(ss) = prev_control_tlvs_ss.take() {
341                                 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(
342                                         ForwardTlvs {
343                                                 next_node_id: unblinded_pk_opt.unwrap(),
344                                                 next_blinding_override: None,
345                                         }
346                                 )), ss));
347                         }
348                         prev_control_tlvs_ss = Some(control_tlvs_ss);
349                         unblinded_path_idx += 1;
350                 } else if let Some((intro_node_id, blinding_pt)) = intro_node_id_blinding_pt.take() {
351                         if let Some(control_tlvs_ss) = prev_control_tlvs_ss.take() {
352                                 payloads.push((Payload::Forward(ForwardControlTlvs::Unblinded(ForwardTlvs {
353                                         next_node_id: intro_node_id,
354                                         next_blinding_override: Some(blinding_pt),
355                                 })), control_tlvs_ss));
356                         }
357                         if let Some(encrypted_payload) = enc_payload_opt {
358                                 payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(encrypted_payload)),
359                                         control_tlvs_ss));
360                         } else { debug_assert!(false); }
361                         blinded_path_idx += 1;
362                 } else if blinded_path_idx < num_blinded_hops - 1 && enc_payload_opt.is_some() {
363                         payloads.push((Payload::Forward(ForwardControlTlvs::Blinded(enc_payload_opt.unwrap())),
364                                 control_tlvs_ss));
365                         blinded_path_idx += 1;
366                 } else if let Some(encrypted_payload) = enc_payload_opt {
367                         payloads.push((Payload::Receive {
368                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_payload),
369                                 reply_path: reply_path.take(),
370                         }, control_tlvs_ss));
371                 }
372
373                 let (rho, mu) = onion_utils::gen_rho_mu_from_shared_secret(onion_packet_ss.as_ref());
374                 onion_packet_keys.push(onion_utils::OnionKeys {
375                         #[cfg(test)]
376                         shared_secret: onion_packet_ss,
377                         #[cfg(test)]
378                         blinding_factor: [0; 32],
379                         ephemeral_pubkey,
380                         rho,
381                         mu,
382                 });
383         })?;
384
385         if let Some(control_tlvs_ss) = prev_control_tlvs_ss {
386                 payloads.push((Payload::Receive {
387                         control_tlvs: ReceiveControlTlvs::Unblinded(ReceiveTlvs { path_id: None, }),
388                         reply_path: reply_path.take(),
389                 }, control_tlvs_ss));
390         }
391
392         Ok((payloads, onion_packet_keys))
393 }
394
395 /// Errors if the serialized payload size exceeds onion_message::BIG_PACKET_HOP_DATA_LEN
396 fn construct_onion_message_packet(payloads: Vec<(Payload, [u8; 32])>, onion_keys: Vec<onion_utils::OnionKeys>, prng_seed: [u8; 32]) -> Result<Packet, ()> {
397         // Spec rationale:
398         // "`len` allows larger messages to be sent than the standard 1300 bytes allowed for an HTLC
399         // onion, but this should be used sparingly as it is reduces anonymity set, hence the
400         // recommendation that it either look like an HTLC onion, or if larger, be a fixed size."
401         let payloads_ser_len = onion_utils::payloads_serialized_length(&payloads);
402         let hop_data_len = if payloads_ser_len <= SMALL_PACKET_HOP_DATA_LEN {
403                 SMALL_PACKET_HOP_DATA_LEN
404         } else if payloads_ser_len <= BIG_PACKET_HOP_DATA_LEN {
405                 BIG_PACKET_HOP_DATA_LEN
406         } else { return Err(()) };
407
408         Ok(onion_utils::construct_onion_message_packet::<_, _>(
409                 payloads, onion_keys, prng_seed, hop_data_len))
410 }