_ 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;
  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(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 }
 139
 140 impl<T: OnionMessageContents> Writeable for ParsedOnionMessageContents<T> {
 141         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 142                 match self {
 143                         ParsedOnionMessageContents::Offers(msg) => Ok(msg.write(w)?),
 144                         ParsedOnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 145                 }
 146         }
 147 }
 148
 149 /// The contents of an onion message.
 150 pub trait OnionMessageContents: Writeable + core::fmt::Debug {
 151         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 152         fn tlv_type(&self) -> u64;
 153 }
 154
 155 /// Forward control TLVs in their blinded and unblinded form.
 156 pub(super) enum ForwardControlTlvs {
 157         /// If we're sending to a blinded path, the node that constructed the blinded path has provided
 158         /// this hop's control TLVs, already encrypted into bytes.
 159         Blinded(Vec<u8>),
 160         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 161         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 162         /// them into an intermediate Vec. See [`crate::blinded_path::message::ForwardTlvs`] for more
 163         /// info.
 164         Unblinded(ForwardTlvs),
 165 }
 166
 167 /// Receive control TLVs in their blinded and unblinded form.
 168 pub(super) enum ReceiveControlTlvs {
 169         /// See [`ForwardControlTlvs::Blinded`].
 170         Blinded(Vec<u8>),
 171         /// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::message::ReceiveTlvs`].
 172         Unblinded(ReceiveTlvs),
 173 }
 174
 175 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 176 impl<T: OnionMessageContents> Writeable for (Payload<T>, [u8; 32]) {
 177         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 178                 match &self.0 {
 179                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 180                                 _encode_varint_length_prefixed_tlv!(w, {
 181                                         (4, *encrypted_bytes, required_vec)
 182                                 })
 183                         },
 184                         Payload::Receive {
 185                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path, message,
 186                         } => {
 187                                 _encode_varint_length_prefixed_tlv!(w, {
 188                                         (2, reply_path, option),
 189                                         (4, *encrypted_bytes, required_vec),
 190                                         (message.tlv_type(), message, required)
 191                                 })
 192                         },
 193                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 194                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 195                                 _encode_varint_length_prefixed_tlv!(w, {
 196                                         (4, write_adapter, required)
 197                                 })
 198                         },
 199                         Payload::Receive {
 200                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path, message,
 201                         } => {
 202                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 203                                 _encode_varint_length_prefixed_tlv!(w, {
 204                                         (2, reply_path, option),
 205                                         (4, write_adapter, required),
 206                                         (message.tlv_type(), message, required)
 207                                 })
 208                         },
 209                 }
 210                 Ok(())
 211         }
 212 }
 213
 214 // Uses the provided secret to simultaneously decode and decrypt the control TLVs and data TLV.
 215 impl<H: CustomOnionMessageHandler + ?Sized, L: Logger + ?Sized> ReadableArgs<(SharedSecret, &H, &L)>
 216 for Payload<ParsedOnionMessageContents<<H as CustomOnionMessageHandler>::CustomMessage>> {
 217         fn read<R: Read>(r: &mut R, args: (SharedSecret, &H, &L)) -> Result<Self, DecodeError> {
 218                 let (encrypted_tlvs_ss, handler, logger) = args;
 219
 220                 let v: BigSize = Readable::read(r)?;
 221                 let mut rd = FixedLengthReader::new(r, v.0);
 222                 let mut reply_path: Option<BlindedPath> = None;
 223                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 224                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 225                 let mut message_type: Option<u64> = None;
 226                 let mut message = None;
 227                 decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
 228                         (2, reply_path, option),
 229                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 230                 }, |msg_type, msg_reader| {
 231                         if msg_type < 64 { return Ok(false) }
 232                         // Don't allow reading more than one data TLV from an onion message.
 233                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 234
 235                         message_type = Some(msg_type);
 236                         match msg_type {
 237                                 tlv_type if OffersMessage::is_known_type(tlv_type) => {
 238                                         let msg = OffersMessage::read(msg_reader, (tlv_type, logger))?;
 239                                         message = Some(ParsedOnionMessageContents::Offers(msg));
 240                                         Ok(true)
 241                                 },
 242                                 _ => match handler.read_custom_message(msg_type, msg_reader)? {
 243                                         Some(msg) => {
 244                                                 message = Some(ParsedOnionMessageContents::Custom(msg));
 245                                                 Ok(true)
 246                                         },
 247                                         None => Ok(false),
 248                                 },
 249                         }
 250                 });
 251                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 252
 253                 match read_adapter {
 254                         None => return Err(DecodeError::InvalidValue),
 255                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 256                                 if message_type.is_some() {
 257                                         return Err(DecodeError::InvalidValue)
 258                                 }
 259                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 260                         },
 261                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 262                                 Ok(Payload::Receive {
 263                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 264                                         reply_path,
 265                                         message: message.ok_or(DecodeError::InvalidValue)?,
 266                                 })
 267                         },
 268                 }
 269         }
 270 }
 271
 272 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 273 /// or received. Thus we read a `ControlTlvs` rather than reading a [`ForwardTlvs`] or
 274 /// [`ReceiveTlvs`] directly. Also useful on the encoding side to keep forward and receive TLVs in
 275 /// the same iterator.
 276 pub(crate) enum ControlTlvs {
 277         /// This onion message is intended to be forwarded.
 278         Forward(ForwardTlvs),
 279         /// This onion message is intended to be received.
 280         Receive(ReceiveTlvs),
 281 }
 282
 283 impl Readable for ControlTlvs {
 284         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 285                 _init_and_read_tlv_stream!(r, {
 286                         (1, _padding, option),
 287                         (2, _short_channel_id, option),
 288                         (4, next_node_id, option),
 289                         (6, path_id, option),
 290                         (8, next_blinding_override, option),
 291                 });
 292                 let _padding: Option<Padding> = _padding;
 293                 let _short_channel_id: Option<u64> = _short_channel_id;
 294
 295                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 296                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 297
 298                 let payload_fmt = if valid_fwd_fmt {
 299                         ControlTlvs::Forward(ForwardTlvs {
 300                                 next_node_id: next_node_id.unwrap(),
 301                                 next_blinding_override,
 302                         })
 303                 } else if valid_recv_fmt {
 304                         ControlTlvs::Receive(ReceiveTlvs {
 305                                 path_id,
 306                         })
 307                 } else {
 308                         return Err(DecodeError::InvalidValue)
 309                 };
 310
 311                 Ok(payload_fmt)
 312         }
 313 }
 314
 315 impl Writeable for ControlTlvs {
 316         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 317                 match self {
 318                         Self::Forward(tlvs) => tlvs.write(w),
 319                         Self::Receive(tlvs) => tlvs.write(w),
 320                 }
 321         }
 322 }