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