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_route::{BlindedRoute, 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<BlindedRoute>,
 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         pub fn tlv_type(&self) -> u64 {
 122                 match self {
 123                         &OnionMessageContents::Custom(ref msg) => msg.tlv_type(),
 124                 }
 125         }
 126 }
 127
 128 impl<T: CustomOnionMessageContents> Writeable for OnionMessageContents<T> {
 129         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 130                 match self {
 131                         OnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 132                 }
 133         }
 134 }
 135
 136 /// The contents of a custom onion message.
 137 pub trait CustomOnionMessageContents: Writeable {
 138         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 139         fn tlv_type(&self) -> u64;
 140 }
 141
 142 /// Forward control TLVs in their blinded and unblinded form.
 143 pub(super) enum ForwardControlTlvs {
 144         /// If we're sending to a blinded route, the node that constructed the blinded route has provided
 145         /// this hop's control TLVs, already encrypted into bytes.
 146         Blinded(Vec<u8>),
 147         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 148         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 149         /// them into an intermediate Vec. See [`super::blinded_route::ForwardTlvs`] for more info.
 150         Unblinded(ForwardTlvs),
 151 }
 152
 153 /// Receive control TLVs in their blinded and unblinded form.
 154 pub(super) enum ReceiveControlTlvs {
 155         /// See [`ForwardControlTlvs::Blinded`].
 156         Blinded(Vec<u8>),
 157         /// See [`ForwardControlTlvs::Unblinded`] and [`super::blinded_route::ReceiveTlvs`].
 158         Unblinded(ReceiveTlvs),
 159 }
 160
 161 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 162 impl<T: CustomOnionMessageContents> Writeable for (Payload<T>, [u8; 32]) {
 163         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 164                 match &self.0 {
 165                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 166                                 encode_varint_length_prefixed_tlv!(w, {
 167                                         (4, *encrypted_bytes, vec_type)
 168                                 })
 169                         },
 170                         Payload::Receive {
 171                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path, message,
 172                         } => {
 173                                 encode_varint_length_prefixed_tlv!(w, {
 174                                         (2, reply_path, option),
 175                                         (4, *encrypted_bytes, vec_type),
 176                                         (message.tlv_type(), message, required)
 177                                 })
 178                         },
 179                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 180                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 181                                 encode_varint_length_prefixed_tlv!(w, {
 182                                         (4, write_adapter, required)
 183                                 })
 184                         },
 185                         Payload::Receive {
 186                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path, message,
 187                         } => {
 188                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 189                                 encode_varint_length_prefixed_tlv!(w, {
 190                                         (2, reply_path, option),
 191                                         (4, write_adapter, required),
 192                                         (message.tlv_type(), message, required)
 193                                 })
 194                         },
 195                 }
 196                 Ok(())
 197         }
 198 }
 199
 200 // Uses the provided secret to simultaneously decode and decrypt the control TLVs and data TLV.
 201 impl<H: CustomOnionMessageHandler> ReadableArgs<(SharedSecret, &H)> for Payload<<H as CustomOnionMessageHandler>::CustomMessage> {
 202         fn read<R: Read>(r: &mut R, args: (SharedSecret, &H)) -> Result<Self, DecodeError> {
 203                 let (encrypted_tlvs_ss, handler) = args;
 204
 205                 let v: BigSize = Readable::read(r)?;
 206                 let mut rd = FixedLengthReader::new(r, v.0);
 207                 let mut reply_path: Option<BlindedRoute> = None;
 208                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 209                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 210                 let mut message_type: Option<u64> = None;
 211                 let mut message = None;
 212                 decode_tlv_stream!(&mut rd, {
 213                         (2, reply_path, option),
 214                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 215                 }, |msg_type, msg_reader| {
 216                         if msg_type < 64 { return Ok(false) }
 217                         // Don't allow reading more than one data TLV from an onion message.
 218                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 219
 220                         message_type = Some(msg_type);
 221                         match handler.read_custom_message(msg_type, msg_reader) {
 222                                 Ok(Some(msg)) => {
 223                                         message = Some(msg);
 224                                         Ok(true)
 225                                 },
 226                                 Ok(None) => Ok(false),
 227                                 Err(e) => Err(e),
 228                         }
 229                 });
 230                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 231
 232                 match read_adapter {
 233                         None => return Err(DecodeError::InvalidValue),
 234                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 235                                 if message_type.is_some() {
 236                                         return Err(DecodeError::InvalidValue)
 237                                 }
 238                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 239                         },
 240                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 241                                 if message.is_none() { return Err(DecodeError::InvalidValue) }
 242                                 Ok(Payload::Receive {
 243                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 244                                         reply_path,
 245                                         message: OnionMessageContents::Custom(message.unwrap()),
 246                                 })
 247                         }
 248                 }
 249         }
 250 }
 251
 252 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 253 /// or received. Thus we read a ControlTlvs rather than reading a ForwardControlTlvs or
 254 /// ReceiveControlTlvs directly.
 255 pub(super) enum ControlTlvs {
 256         /// This onion message is intended to be forwarded.
 257         Forward(ForwardTlvs),
 258         /// This onion message is intended to be received.
 259         Receive(ReceiveTlvs),
 260 }
 261
 262 impl Readable for ControlTlvs {
 263         fn read<R: Read>(mut r: &mut R) -> Result<Self, DecodeError> {
 264                 let mut _padding: Option<Padding> = None;
 265                 let mut _short_channel_id: Option<u64> = None;
 266                 let mut next_node_id: Option<PublicKey> = None;
 267                 let mut path_id: Option<[u8; 32]> = None;
 268                 let mut next_blinding_override: Option<PublicKey> = None;
 269                 decode_tlv_stream!(&mut r, {
 270                         (1, _padding, option),
 271                         (2, _short_channel_id, option),
 272                         (4, next_node_id, option),
 273                         (6, path_id, option),
 274                         (8, next_blinding_override, option),
 275                 });
 276
 277                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 278                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 279
 280                 let payload_fmt = if valid_fwd_fmt {
 281                         ControlTlvs::Forward(ForwardTlvs {
 282                                 next_node_id: next_node_id.unwrap(),
 283                                 next_blinding_override,
 284                         })
 285                 } else if valid_recv_fmt {
 286                         ControlTlvs::Receive(ReceiveTlvs {
 287                                 path_id,
 288                         })
 289                 } else {
 290                         return Err(DecodeError::InvalidValue)
 291                 };
 292
 293                 Ok(payload_fmt)
 294         }
 295 }
 296
 297 /// Reads padding to the end, ignoring what's read.
 298 pub(crate) struct Padding {}
 299 impl Readable for Padding {
 300         #[inline]
 301         fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
 302                 loop {
 303                         let mut buf = [0; 8192];
 304                         if reader.read(&mut buf[..])? == 0 { break; }
 305                 }
 306                 Ok(Self {})
 307         }
 308 }