_ 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::util::chacha20poly1305rfc::{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, 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: CustomOnionMessageContents> {
 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: ParsedOnionMessageContents<T>,
 114         }
 115 }
 116
 117 /// The contents of an onion message as read from the wire.
 118 #[derive(Debug)]
 119 pub enum ParsedOnionMessageContents<T: CustomOnionMessageContents> {
 120         /// A message related to BOLT 12 Offers.
 121         Offers(OffersMessage),
 122         /// A custom onion message specified by the user.
 123         Custom(T),
 124 }
 125
 126 impl<T: CustomOnionMessageContents> ParsedOnionMessageContents<T> {
 127         /// Returns the type that was used to decode the message payload.
 128         ///
 129         /// This is not exported to bindings users as methods on non-cloneable enums are not currently exportable
 130         pub fn tlv_type(&self) -> u64 {
 131                 match self {
 132                         &ParsedOnionMessageContents::Offers(ref msg) => msg.tlv_type(),
 133                         &ParsedOnionMessageContents::Custom(ref msg) => msg.tlv_type(),
 134                 }
 135         }
 136 }
 137
 138 /// This is not exported to bindings users as methods on non-cloneable enums are not currently exportable
 139 impl<T: CustomOnionMessageContents> Writeable for ParsedOnionMessageContents<T> {
 140         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 141                 match self {
 142                         ParsedOnionMessageContents::Offers(msg) => Ok(msg.write(w)?),
 143                         ParsedOnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 144                 }
 145         }
 146 }
 147
 148 /// The contents of a custom onion message.
 149 pub trait CustomOnionMessageContents: Writeable {
 150         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 151         fn tlv_type(&self) -> u64;
 152 }
 153
 154 /// Forward control TLVs in their blinded and unblinded form.
 155 pub(super) enum ForwardControlTlvs {
 156         /// If we're sending to a blinded path, the node that constructed the blinded path has provided
 157         /// this hop's control TLVs, already encrypted into bytes.
 158         Blinded(Vec<u8>),
 159         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 160         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 161         /// them into an intermediate Vec. See [`crate::blinded_path::message::ForwardTlvs`] for more
 162         /// info.
 163         Unblinded(ForwardTlvs),
 164 }
 165
 166 /// Receive control TLVs in their blinded and unblinded form.
 167 pub(super) enum ReceiveControlTlvs {
 168         /// See [`ForwardControlTlvs::Blinded`].
 169         Blinded(Vec<u8>),
 170         /// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::message::ReceiveTlvs`].
 171         Unblinded(ReceiveTlvs),
 172 }
 173
 174 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 175 impl<T: CustomOnionMessageContents> Writeable for (Payload<T>, [u8; 32]) {
 176         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 177                 match &self.0 {
 178                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 179                                 _encode_varint_length_prefixed_tlv!(w, {
 180                                         (4, *encrypted_bytes, required_vec)
 181                                 })
 182                         },
 183                         Payload::Receive {
 184                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path, message,
 185                         } => {
 186                                 _encode_varint_length_prefixed_tlv!(w, {
 187                                         (2, reply_path, option),
 188                                         (4, *encrypted_bytes, required_vec),
 189                                         (message.tlv_type(), message, required)
 190                                 })
 191                         },
 192                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 193                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 194                                 _encode_varint_length_prefixed_tlv!(w, {
 195                                         (4, write_adapter, required)
 196                                 })
 197                         },
 198                         Payload::Receive {
 199                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path, message,
 200                         } => {
 201                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 202                                 _encode_varint_length_prefixed_tlv!(w, {
 203                                         (2, reply_path, option),
 204                                         (4, write_adapter, required),
 205                                         (message.tlv_type(), message, required)
 206                                 })
 207                         },
 208                 }
 209                 Ok(())
 210         }
 211 }
 212
 213 // Uses the provided secret to simultaneously decode and decrypt the control TLVs and data TLV.
 214 impl<H: CustomOnionMessageHandler + ?Sized, L: Logger + ?Sized>
 215 ReadableArgs<(SharedSecret, &H, &L)> for Payload<<H as CustomOnionMessageHandler>::CustomMessage> {
 216         fn read<R: Read>(r: &mut R, args: (SharedSecret, &H, &L)) -> Result<Self, DecodeError> {
 217                 let (encrypted_tlvs_ss, handler, logger) = args;
 218
 219                 let v: BigSize = Readable::read(r)?;
 220                 let mut rd = FixedLengthReader::new(r, v.0);
 221                 let mut reply_path: Option<BlindedPath> = None;
 222                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 223                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 224                 let mut message_type: Option<u64> = None;
 225                 let mut message = None;
 226                 decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
 227                         (2, reply_path, option),
 228                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 229                 }, |msg_type, msg_reader| {
 230                         if msg_type < 64 { return Ok(false) }
 231                         // Don't allow reading more than one data TLV from an onion message.
 232                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 233
 234                         message_type = Some(msg_type);
 235                         match msg_type {
 236                                 tlv_type if OffersMessage::is_known_type(tlv_type) => {
 237                                         let msg = OffersMessage::read(msg_reader, (tlv_type, logger))?;
 238                                         message = Some(ParsedOnionMessageContents::Offers(msg));
 239                                         Ok(true)
 240                                 },
 241                                 _ => match handler.read_custom_message(msg_type, msg_reader)? {
 242                                         Some(msg) => {
 243                                                 message = Some(ParsedOnionMessageContents::Custom(msg));
 244                                                 Ok(true)
 245                                         },
 246                                         None => Ok(false),
 247                                 },
 248                         }
 249                 });
 250                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 251
 252                 match read_adapter {
 253                         None => return Err(DecodeError::InvalidValue),
 254                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 255                                 if message_type.is_some() {
 256                                         return Err(DecodeError::InvalidValue)
 257                                 }
 258                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 259                         },
 260                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 261                                 Ok(Payload::Receive {
 262                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 263                                         reply_path,
 264                                         message: message.ok_or(DecodeError::InvalidValue)?,
 265                                 })
 266                         },
 267                 }
 268         }
 269 }
 270
 271 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 272 /// or received. Thus we read a `ControlTlvs` rather than reading a [`ForwardTlvs`] or
 273 /// [`ReceiveTlvs`] directly. Also useful on the encoding side to keep forward and receive TLVs in
 274 /// the same iterator.
 275 pub(crate) enum ControlTlvs {
 276         /// This onion message is intended to be forwarded.
 277         Forward(ForwardTlvs),
 278         /// This onion message is intended to be received.
 279         Receive(ReceiveTlvs),
 280 }
 281
 282 impl Readable for ControlTlvs {
 283         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 284                 _init_and_read_tlv_stream!(r, {
 285                         (1, _padding, option),
 286                         (2, _short_channel_id, option),
 287                         (4, next_node_id, option),
 288                         (6, path_id, option),
 289                         (8, next_blinding_override, option),
 290                 });
 291                 let _padding: Option<Padding> = _padding;
 292                 let _short_channel_id: Option<u64> = _short_channel_id;
 293
 294                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 295                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 296
 297                 let payload_fmt = if valid_fwd_fmt {
 298                         ControlTlvs::Forward(ForwardTlvs {
 299                                 next_node_id: next_node_id.unwrap(),
 300                                 next_blinding_override,
 301                         })
 302                 } else if valid_recv_fmt {
 303                         ControlTlvs::Receive(ReceiveTlvs {
 304                                 path_id,
 305                         })
 306                 } else {
 307                         return Err(DecodeError::InvalidValue)
 308                 };
 309
 310                 Ok(payload_fmt)
 311         }
 312 }
 313
 314 impl Writeable for ControlTlvs {
 315         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 316                 match self {
 317                         Self::Forward(tlvs) => tlvs.write(w),
 318                         Self::Receive(tlvs) => tlvs.write(w),
 319                 }
 320         }
 321 }