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