_ 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, ForwardTlvs, ReceiveTlvs};
  16 use crate::ln::msgs::DecodeError;
  17 use crate::ln::onion_utils;
  18 use super::messenger::CustomOnionMessageHandler;
  19 use crate::util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
  20 use crate::util::logger::Logger;
  21 use crate::util::ser::{BigSize, FixedLengthReader, LengthRead, LengthReadable, LengthReadableArgs, Readable, ReadableArgs, Writeable, Writer};
  22
  23 use core::cmp;
  24 use crate::io::{self, Read};
  25 use crate::prelude::*;
  26
  27 // Per the spec, an onion message packet's `hop_data` field length should be
  28 // SMALL_PACKET_HOP_DATA_LEN if it fits, else BIG_PACKET_HOP_DATA_LEN if it fits.
  29 pub(super) const SMALL_PACKET_HOP_DATA_LEN: usize = 1300;
  30 pub(super) const BIG_PACKET_HOP_DATA_LEN: usize = 32768;
  31
  32 #[derive(Clone, Debug, PartialEq, Eq)]
  33 pub(crate) struct Packet {
  34         pub(super) version: u8,
  35         pub(super) public_key: PublicKey,
  36         // Unlike the onion packets used for payments, onion message packets can have payloads greater
  37         // than 1300 bytes.
  38         // TODO: if 1300 ends up being the most common size, optimize this to be:
  39         // enum { ThirteenHundred([u8; 1300]), VarLen(Vec<u8>) }
  40         pub(super) hop_data: Vec<u8>,
  41         pub(super) hmac: [u8; 32],
  42 }
  43
  44 impl onion_utils::Packet for Packet {
  45         type Data = Vec<u8>;
  46         fn new(public_key: PublicKey, hop_data: Vec<u8>, hmac: [u8; 32]) -> Packet {
  47                 Self {
  48                         version: 0,
  49                         public_key,
  50                         hop_data,
  51                         hmac,
  52                 }
  53         }
  54 }
  55
  56 impl Writeable for Packet {
  57         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
  58                 self.version.write(w)?;
  59                 self.public_key.write(w)?;
  60                 w.write_all(&self.hop_data)?;
  61                 self.hmac.write(w)?;
  62                 Ok(())
  63         }
  64 }
  65
  66 impl LengthReadable for Packet {
  67         fn read<R: LengthRead>(r: &mut R) -> Result<Self, DecodeError> {
  68                 const READ_BUFFER_SIZE: usize = 4096;
  69
  70                 let version = Readable::read(r)?;
  71                 let public_key = Readable::read(r)?;
  72
  73                 let mut hop_data = Vec::new();
  74                 let hop_data_len = r.total_bytes().saturating_sub(66) as usize; // 1 (version) + 33 (pubkey) + 32 (HMAC) = 66
  75                 let mut read_idx = 0;
  76                 while read_idx < hop_data_len {
  77                         let mut read_buffer = [0; READ_BUFFER_SIZE];
  78                         let read_amt = cmp::min(hop_data_len - read_idx, READ_BUFFER_SIZE);
  79                         r.read_exact(&mut read_buffer[..read_amt])?;
  80                         hop_data.extend_from_slice(&read_buffer[..read_amt]);
  81                         read_idx += read_amt;
  82                 }
  83
  84                 let hmac = Readable::read(r)?;
  85                 Ok(Packet {
  86                         version,
  87                         public_key,
  88                         hop_data,
  89                         hmac,
  90                 })
  91         }
  92 }
  93
  94 /// Onion message payloads contain "control" TLVs and "data" TLVs. Control TLVs are used to route
  95 /// the onion message from hop to hop and for path verification, whereas data TLVs contain the onion
  96 /// message content itself, such as an invoice request.
  97 pub(super) enum Payload<T: CustomOnionMessageContents> {
  98         /// This payload is for an intermediate hop.
  99         Forward(ForwardControlTlvs),
 100         /// This payload is for the final hop.
 101         Receive {
 102                 control_tlvs: ReceiveControlTlvs,
 103                 reply_path: Option<BlindedPath>,
 104                 message: OnionMessageContents<T>,
 105         }
 106 }
 107
 108 #[derive(Debug)]
 109 /// The contents of an onion message. In the context of offers, this would be the invoice, invoice
 110 /// request, or invoice error.
 111 pub enum OnionMessageContents<T: CustomOnionMessageContents> {
 112         // Coming soon:
 113         // Invoice,
 114         // InvoiceRequest,
 115         // InvoiceError,
 116         /// A custom onion message specified by the user.
 117         Custom(T),
 118 }
 119
 120 impl<T: CustomOnionMessageContents> OnionMessageContents<T> {
 121         /// Returns the type that was used to decode the message payload.
 122         ///
 123         /// This is not exported to bindings users as methods on non-cloneable enums are not currently exportable
 124         pub fn tlv_type(&self) -> u64 {
 125                 match self {
 126                         &OnionMessageContents::Custom(ref msg) => msg.tlv_type(),
 127                 }
 128         }
 129 }
 130
 131 /// This is not exported to bindings users as methods on non-cloneable enums are not currently exportable
 132 impl<T: CustomOnionMessageContents> Writeable for OnionMessageContents<T> {
 133         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 134                 match self {
 135                         OnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 136                 }
 137         }
 138 }
 139
 140 /// The contents of a custom onion message.
 141 pub trait CustomOnionMessageContents: Writeable {
 142         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 143         fn tlv_type(&self) -> u64;
 144 }
 145
 146 /// Forward control TLVs in their blinded and unblinded form.
 147 pub(super) enum ForwardControlTlvs {
 148         /// If we're sending to a blinded path, the node that constructed the blinded path has provided
 149         /// this hop's control TLVs, already encrypted into bytes.
 150         Blinded(Vec<u8>),
 151         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 152         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 153         /// them into an intermediate Vec. See [`crate::blinded_path::ForwardTlvs`] for more info.
 154         Unblinded(ForwardTlvs),
 155 }
 156
 157 /// Receive control TLVs in their blinded and unblinded form.
 158 pub(super) enum ReceiveControlTlvs {
 159         /// See [`ForwardControlTlvs::Blinded`].
 160         Blinded(Vec<u8>),
 161         /// See [`ForwardControlTlvs::Unblinded`] and [`crate::blinded_path::ReceiveTlvs`].
 162         Unblinded(ReceiveTlvs),
 163 }
 164
 165 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 166 impl<T: CustomOnionMessageContents> Writeable for (Payload<T>, [u8; 32]) {
 167         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 168                 match &self.0 {
 169                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 170                                 _encode_varint_length_prefixed_tlv!(w, {
 171                                         (4, *encrypted_bytes, vec_type)
 172                                 })
 173                         },
 174                         Payload::Receive {
 175                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path, message,
 176                         } => {
 177                                 _encode_varint_length_prefixed_tlv!(w, {
 178                                         (2, reply_path, option),
 179                                         (4, *encrypted_bytes, vec_type),
 180                                         (message.tlv_type(), message, required)
 181                                 })
 182                         },
 183                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 184                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 185                                 _encode_varint_length_prefixed_tlv!(w, {
 186                                         (4, write_adapter, required)
 187                                 })
 188                         },
 189                         Payload::Receive {
 190                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path, message,
 191                         } => {
 192                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 193                                 _encode_varint_length_prefixed_tlv!(w, {
 194                                         (2, reply_path, option),
 195                                         (4, write_adapter, required),
 196                                         (message.tlv_type(), message, required)
 197                                 })
 198                         },
 199                 }
 200                 Ok(())
 201         }
 202 }
 203
 204 // Uses the provided secret to simultaneously decode and decrypt the control TLVs and data TLV.
 205 impl<H: CustomOnionMessageHandler, L: Logger>
 206 ReadableArgs<(SharedSecret, &H, &L)> for Payload<<H as CustomOnionMessageHandler>::CustomMessage> {
 207         fn read<R: Read>(r: &mut R, args: (SharedSecret, &H, &L)) -> Result<Self, DecodeError> {
 208                 let (encrypted_tlvs_ss, handler, _logger) = args;
 209
 210                 let v: BigSize = Readable::read(r)?;
 211                 let mut rd = FixedLengthReader::new(r, v.0);
 212                 let mut reply_path: Option<BlindedPath> = None;
 213                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 214                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 215                 let mut message_type: Option<u64> = None;
 216                 let mut message = None;
 217                 decode_tlv_stream_with_custom_tlv_decode!(&mut rd, {
 218                         (2, reply_path, option),
 219                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 220                 }, |msg_type, msg_reader| {
 221                         if msg_type < 64 { return Ok(false) }
 222                         // Don't allow reading more than one data TLV from an onion message.
 223                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 224
 225                         message_type = Some(msg_type);
 226                         match handler.read_custom_message(msg_type, msg_reader) {
 227                                 Ok(Some(msg)) => {
 228                                         message = Some(msg);
 229                                         Ok(true)
 230                                 },
 231                                 Ok(None) => Ok(false),
 232                                 Err(e) => Err(e),
 233                         }
 234                 });
 235                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 236
 237                 match read_adapter {
 238                         None => return Err(DecodeError::InvalidValue),
 239                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 240                                 if message_type.is_some() {
 241                                         return Err(DecodeError::InvalidValue)
 242                                 }
 243                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 244                         },
 245                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 246                                 if message.is_none() { return Err(DecodeError::InvalidValue) }
 247                                 Ok(Payload::Receive {
 248                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 249                                         reply_path,
 250                                         message: OnionMessageContents::Custom(message.unwrap()),
 251                                 })
 252                         }
 253                 }
 254         }
 255 }
 256
 257 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 258 /// or received. Thus we read a ControlTlvs rather than reading a ForwardControlTlvs or
 259 /// ReceiveControlTlvs directly.
 260 pub(crate) enum ControlTlvs {
 261         /// This onion message is intended to be forwarded.
 262         Forward(ForwardTlvs),
 263         /// This onion message is intended to be received.
 264         Receive(ReceiveTlvs),
 265 }
 266
 267 impl Readable for ControlTlvs {
 268         fn read<R: Read>(mut r: &mut R) -> Result<Self, DecodeError> {
 269                 let mut _padding: Option<Padding> = None;
 270                 let mut _short_channel_id: Option<u64> = None;
 271                 let mut next_node_id: Option<PublicKey> = None;
 272                 let mut path_id: Option<[u8; 32]> = None;
 273                 let mut next_blinding_override: Option<PublicKey> = None;
 274                 decode_tlv_stream!(&mut r, {
 275                         (1, _padding, option),
 276                         (2, _short_channel_id, option),
 277                         (4, next_node_id, option),
 278                         (6, path_id, option),
 279                         (8, next_blinding_override, option),
 280                 });
 281
 282                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 283                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 284
 285                 let payload_fmt = if valid_fwd_fmt {
 286                         ControlTlvs::Forward(ForwardTlvs {
 287                                 next_node_id: next_node_id.unwrap(),
 288                                 next_blinding_override,
 289                         })
 290                 } else if valid_recv_fmt {
 291                         ControlTlvs::Receive(ReceiveTlvs {
 292                                 path_id,
 293                         })
 294                 } else {
 295                         return Err(DecodeError::InvalidValue)
 296                 };
 297
 298                 Ok(payload_fmt)
 299         }
 300 }
 301
 302 /// Reads padding to the end, ignoring what's read.
 303 pub(crate) struct Padding {}
 304 impl Readable for Padding {
 305         #[inline]
 306         fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
 307                 loop {
 308                         let mut buf = [0; 8192];
 309                         if reader.read(&mut buf[..])? == 0 { break; }
 310                 }
 311                 Ok(Self {})
 312         }
 313 }