_ Git - rust-lightning/blob - lightning/src/onion_message/packet.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 //! Structs and enums useful for constructing and reading an onion message packet.
  11
  12 use bitcoin::secp256k1::PublicKey;
  13 use bitcoin::secp256k1::ecdh::SharedSecret;
  14
  15 use crate::blinded_path::{BlindedPath, NextMessageHop};
  16 use crate::blinded_path::message::{ForwardTlvs, ReceiveTlvs};
  17 use crate::blinded_path::utils::Padding;
  18 use crate::ln::msgs::DecodeError;
  19 use crate::ln::onion_utils;
  20 use super::messenger::CustomOnionMessageHandler;
  21 use super::offers::OffersMessage;
  22 use crate::crypto::streams::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
  23 use crate::util::logger::Logger;
  24 use crate::util::ser::{BigSize, FixedLengthReader, LengthRead, LengthReadable, LengthReadableArgs, Readable, ReadableArgs, Writeable, Writer};
  25
  26 use core::cmp;
  27 use crate::io::{self, Read};
  28 use crate::prelude::*;
  29
  30 // Per the spec, an onion message packet's `hop_data` field length should be
  31 // SMALL_PACKET_HOP_DATA_LEN if it fits, else BIG_PACKET_HOP_DATA_LEN if it fits.
  32 pub(super) const SMALL_PACKET_HOP_DATA_LEN: usize = 1300;
  33 pub(super) const BIG_PACKET_HOP_DATA_LEN: usize = 32768;
  34
  35 /// Packet of hop data for next peer
  36 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
  37 pub struct Packet {
  38         /// Bolt 04 version number
  39         pub version: u8,
  40         /// A random sepc256k1 point, used to build the ECDH shared secret to decrypt hop_data
  41         pub public_key: PublicKey,
  42         /// Encrypted payload for the next hop
  43         //
  44         // Unlike the onion packets used for payments, onion message packets can have payloads greater
  45         // than 1300 bytes.
  46         // TODO: if 1300 ends up being the most common size, optimize this to be:
  47         // enum { ThirteenHundred([u8; 1300]), VarLen(Vec<u8>) }
  48         pub hop_data: Vec<u8>,
  49         /// HMAC to verify the integrity of hop_data
  50         pub hmac: [u8; 32],
  51 }
  52
  53 impl onion_utils::Packet for Packet {
  54         type Data = Vec<u8>;
  55         fn new(public_key: PublicKey, hop_data: Vec<u8>, hmac: [u8; 32]) -> Packet {
  56                 Self {
  57                         version: 0,
  58                         public_key,
  59                         hop_data,
  60                         hmac,
  61                 }
  62         }
  63 }
  64
  65 impl Writeable for Packet {
  66         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
  67                 self.version.write(w)?;
  68                 self.public_key.write(w)?;
  69                 w.write_all(&self.hop_data)?;
  70                 self.hmac.write(w)?;
  71                 Ok(())
  72         }
  73 }
  74
  75 impl LengthReadable for Packet {
  76         fn read<R: LengthRead>(r: &mut R) -> Result<Self, DecodeError> {
  77                 const READ_BUFFER_SIZE: usize = 4096;
  78
  79                 let version = Readable::read(r)?;
  80                 let public_key = Readable::read(r)?;
  81
  82                 let mut hop_data = Vec::new();
  83                 let hop_data_len = r.total_bytes().saturating_sub(66) as usize; // 1 (version) + 33 (pubkey) + 32 (HMAC) = 66
  84                 let mut read_idx = 0;
  85                 while read_idx < hop_data_len {
  86                         let mut read_buffer = [0; READ_BUFFER_SIZE];
  87                         let read_amt = cmp::min(hop_data_len - read_idx, READ_BUFFER_SIZE);
  88                         r.read_exact(&mut read_buffer[..read_amt])?;
  89                         hop_data.extend_from_slice(&read_buffer[..read_amt]);
  90                         read_idx += read_amt;
  91                 }
  92
  93                 let hmac = Readable::read(r)?;
  94                 Ok(Packet {
  95                         version,
  96                         public_key,
  97                         hop_data,
  98                         hmac,
  99                 })
 100         }
 101 }
 102
 103 /// Onion message payloads contain "control" TLVs and "data" TLVs. Control TLVs are used to route
 104 /// the onion message from hop to hop and for path verification, whereas data TLVs contain the onion
 105 /// message content itself, such as an invoice request.
 106 pub(super) enum Payload<T: OnionMessageContents> {
 107         /// This payload is for an intermediate hop.
 108         Forward(ForwardControlTlvs),
 109         /// This payload is for the final hop.
 110         Receive {
 111                 control_tlvs: ReceiveControlTlvs,
 112                 reply_path: Option<BlindedPath>,
 113                 message: T,
 114         }
 115 }
 116
 117 /// The contents of an [`OnionMessage`] as read from the wire.
 118 ///
 119 /// [`OnionMessage`]: crate::ln::msgs::OnionMessage
 120 #[derive(Clone, Debug)]
 121 pub enum ParsedOnionMessageContents<T: OnionMessageContents> {
 122         /// A message related to BOLT 12 Offers.
 123         Offers(OffersMessage),
 124         /// A custom onion message specified by the user.
 125         Custom(T),
 126 }
 127
 128 impl<T: OnionMessageContents> OnionMessageContents for ParsedOnionMessageContents<T> {
 129         /// Returns the type that was used to decode the message payload.
 130         ///
 131         /// This is not exported to bindings users as methods on non-cloneable enums are not currently exportable
 132         fn tlv_type(&self) -> u64 {
 133                 match self {
 134                         &ParsedOnionMessageContents::Offers(ref msg) => msg.tlv_type(),
 135                         &ParsedOnionMessageContents::Custom(ref msg) => msg.tlv_type(),
 136                 }
 137         }
 138         fn msg_type(&self) -> &'static str {
 139                 match self {
 140                         ParsedOnionMessageContents::Offers(ref msg) => msg.msg_type(),
 141                         ParsedOnionMessageContents::Custom(ref msg) => msg.msg_type(),
 142                 }
 143         }
 144 }
 145
 146 impl<T: OnionMessageContents> Writeable for ParsedOnionMessageContents<T> {
 147         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 148                 match self {
 149                         ParsedOnionMessageContents::Offers(msg) => Ok(msg.write(w)?),
 150                         ParsedOnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 151                 }
 152         }
 153 }
 154
 155 /// The contents of an onion message.
 156 pub trait OnionMessageContents: Writeable + core::fmt::Debug {
 157         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 158         fn tlv_type(&self) -> u64;
 159
 160         /// Returns the message type
 161         fn msg_type(&self) -> &'static str;
 162 }
 163
 164 /// Forward control TLVs in their blinded and unblinded form.
 165 pub(super) enum ForwardControlTlvs {
 166         /// If we're sending to a blinded path, the node that constructed the blinded path has provided
 167         /// this hop's control TLVs, already encrypted into bytes.
 168         Blinded(Vec<u8>),
 169         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 170         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 171         /// them into an intermediate Vec. See [`crate::blinded_path::message::ForwardTlvs`] for more
 172         /// info.
 173         Unblinded(ForwardTlvs),
 174 }
 175
 176 /// Receive control TLVs in their blinded and unblinded form.
 177 pub(super) enum ReceiveControlTlvs {
 178         /// See [`ForwardControlTlvs::Blinded`].
 179         Blinded(Vec<u8>),
 180         /// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::message::ReceiveTlvs`].
 181         Unblinded(ReceiveTlvs),
 182 }
 183
 184 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 185 impl<T: OnionMessageContents> Writeable for (Payload<T>, [u8; 32]) {
 186         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 187                 match &self.0 {
 188                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 189                                 _encode_varint_length_prefixed_tlv!(w, {
 190                                         (4, *encrypted_bytes, required_vec)
 191                                 })
 192                         },
 193                         Payload::Receive {
 194                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path, message,
 195                         } => {
 196                                 _encode_varint_length_prefixed_tlv!(w, {
 197                                         (2, reply_path, option),
 198                                         (4, *encrypted_bytes, required_vec),
 199                                         (message.tlv_type(), message, required)
 200                                 })
 201                         },
 202                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 203                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 204                                 _encode_varint_length_prefixed_tlv!(w, {
 205                                         (4, write_adapter, required)
 206                                 })
 207                         },
 208                         Payload::Receive {
 209                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path, message,
 210                         } => {
 211                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 212                                 _encode_varint_length_prefixed_tlv!(w, {
 213                                         (2, reply_path, option),
 214                                         (4, write_adapter, required),
 215                                         (message.tlv_type(), message, required)
 216                                 })
 217                         },
 218                 }
 219                 Ok(())
 220         }
 221 }
 222
 223 // Uses the provided secret to simultaneously decode and decrypt the control TLVs and data TLV.
 224 impl<H: CustomOnionMessageHandler + ?Sized, L: Logger + ?Sized> ReadableArgs<(SharedSecret, &H, &L)>
 225 for Payload<ParsedOnionMessageContents<<H as CustomOnionMessageHandler>::CustomMessage>> {
 226         fn read<R: Read>(r: &mut R, args: (SharedSecret, &H, &L)) -> Result<Self, DecodeError> {
 227                 let (encrypted_tlvs_ss, handler, logger) = args;
 228
 229                 let v: BigSize = Readable::read(r)?;
 230                 let mut rd = FixedLengthReader::new(r, v.0);
 231                 let mut reply_path: Option<BlindedPath> = None;
 232                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 233                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 234                 let mut message_type: Option<u64> = None;
 235                 let mut message = None;
 236                 decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
 237                         (2, reply_path, option),
 238                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 239                 }, |msg_type, msg_reader| {
 240                         if msg_type < 64 { return Ok(false) }
 241                         // Don't allow reading more than one data TLV from an onion message.
 242                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 243
 244                         message_type = Some(msg_type);
 245                         match msg_type {
 246                                 tlv_type if OffersMessage::is_known_type(tlv_type) => {
 247                                         let msg = OffersMessage::read(msg_reader, (tlv_type, logger))?;
 248                                         message = Some(ParsedOnionMessageContents::Offers(msg));
 249                                         Ok(true)
 250                                 },
 251                                 _ => match handler.read_custom_message(msg_type, msg_reader)? {
 252                                         Some(msg) => {
 253                                                 message = Some(ParsedOnionMessageContents::Custom(msg));
 254                                                 Ok(true)
 255                                         },
 256                                         None => Ok(false),
 257                                 },
 258                         }
 259                 });
 260                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 261
 262                 match read_adapter {
 263                         None => return Err(DecodeError::InvalidValue),
 264                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 265                                 if message_type.is_some() {
 266                                         return Err(DecodeError::InvalidValue)
 267                                 }
 268                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 269                         },
 270                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 271                                 Ok(Payload::Receive {
 272                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 273                                         reply_path,
 274                                         message: message.ok_or(DecodeError::InvalidValue)?,
 275                                 })
 276                         },
 277                 }
 278         }
 279 }
 280
 281 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 282 /// or received. Thus we read a `ControlTlvs` rather than reading a [`ForwardTlvs`] or
 283 /// [`ReceiveTlvs`] directly. Also useful on the encoding side to keep forward and receive TLVs in
 284 /// the same iterator.
 285 pub(crate) enum ControlTlvs {
 286         /// This onion message is intended to be forwarded.
 287         Forward(ForwardTlvs),
 288         /// This onion message is intended to be received.
 289         Receive(ReceiveTlvs),
 290 }
 291
 292 impl Readable for ControlTlvs {
 293         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 294                 _init_and_read_tlv_stream!(r, {
 295                         (1, _padding, option),
 296                         (2, short_channel_id, option),
 297                         (4, next_node_id, option),
 298                         (6, path_id, option),
 299                         (8, next_blinding_override, option),
 300                 });
 301                 let _padding: Option<Padding> = _padding;
 302
 303                 let next_hop = match (short_channel_id, next_node_id) {
 304                         (Some(_), Some(_)) => return Err(DecodeError::InvalidValue),
 305                         (Some(scid), None) => Some(NextMessageHop::ShortChannelId(scid)),
 306                         (None, Some(pubkey)) => Some(NextMessageHop::NodeId(pubkey)),
 307                         (None, None) => None,
 308                 };
 309
 310                 let valid_fwd_fmt = next_hop.is_some() && path_id.is_none();
 311                 let valid_recv_fmt = next_hop.is_none() && next_blinding_override.is_none();
 312
 313                 let payload_fmt = if valid_fwd_fmt {
 314                         ControlTlvs::Forward(ForwardTlvs {
 315                                 next_hop: next_hop.unwrap(),
 316                                 next_blinding_override,
 317                         })
 318                 } else if valid_recv_fmt {
 319                         ControlTlvs::Receive(ReceiveTlvs {
 320                                 path_id,
 321                         })
 322                 } else {
 323                         return Err(DecodeError::InvalidValue)
 324                 };
 325
 326                 Ok(payload_fmt)
 327         }
 328 }
 329
 330 impl Writeable for ControlTlvs {
 331         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 332                 match self {
 333                         Self::Forward(tlvs) => tlvs.write(w),
 334                         Self::Receive(tlvs) => tlvs.write(w),
 335                 }
 336         }
 337 }