_ 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 ln::msgs::DecodeError;
  16 use ln::onion_utils;
  17 use super::blinded_route::{BlindedRoute, ForwardTlvs, ReceiveTlvs};
  18 use util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
  19 use util::ser::{BigSize, FixedLengthReader, LengthRead, LengthReadable, LengthReadableArgs, MaybeReadableArgs, Readable, ReadableArgs, Writeable, Writer};
  20
  21 use core::cmp;
  22 use io::{self, Read};
  23 use prelude::*;
  24
  25 // Per the spec, an onion message packet's `hop_data` field length should be
  26 // SMALL_PACKET_HOP_DATA_LEN if it fits, else BIG_PACKET_HOP_DATA_LEN if it fits.
  27 pub(super) const SMALL_PACKET_HOP_DATA_LEN: usize = 1300;
  28 pub(super) const BIG_PACKET_HOP_DATA_LEN: usize = 32768;
  29
  30 #[derive(Clone, Debug, PartialEq)]
  31 pub(crate) struct Packet {
  32         pub(super) version: u8,
  33         pub(super) public_key: PublicKey,
  34         // Unlike the onion packets used for payments, onion message packets can have payloads greater
  35         // than 1300 bytes.
  36         // TODO: if 1300 ends up being the most common size, optimize this to be:
  37         // enum { ThirteenHundred([u8; 1300]), VarLen(Vec<u8>) }
  38         pub(super) hop_data: Vec<u8>,
  39         pub(super) hmac: [u8; 32],
  40 }
  41
  42 impl onion_utils::Packet for Packet {
  43         type Data = Vec<u8>;
  44         fn new(public_key: PublicKey, hop_data: Vec<u8>, hmac: [u8; 32]) -> Packet {
  45                 Self {
  46                         version: 0,
  47                         public_key,
  48                         hop_data,
  49                         hmac,
  50                 }
  51         }
  52 }
  53
  54 impl Writeable for Packet {
  55         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
  56                 self.version.write(w)?;
  57                 self.public_key.write(w)?;
  58                 w.write_all(&self.hop_data)?;
  59                 self.hmac.write(w)?;
  60                 Ok(())
  61         }
  62 }
  63
  64 impl LengthReadable for Packet {
  65         fn read<R: LengthRead>(r: &mut R) -> Result<Self, DecodeError> {
  66                 const READ_BUFFER_SIZE: usize = 4096;
  67
  68                 let version = Readable::read(r)?;
  69                 let public_key = Readable::read(r)?;
  70
  71                 let mut hop_data = Vec::new();
  72                 let hop_data_len = r.total_bytes().saturating_sub(66) as usize; // 1 (version) + 33 (pubkey) + 32 (HMAC) = 66
  73                 let mut read_idx = 0;
  74                 while read_idx < hop_data_len {
  75                         let mut read_buffer = [0; READ_BUFFER_SIZE];
  76                         let read_amt = cmp::min(hop_data_len - read_idx, READ_BUFFER_SIZE);
  77                         r.read_exact(&mut read_buffer[..read_amt])?;
  78                         hop_data.extend_from_slice(&read_buffer[..read_amt]);
  79                         read_idx += read_amt;
  80                 }
  81
  82                 let hmac = Readable::read(r)?;
  83                 Ok(Packet {
  84                         version,
  85                         public_key,
  86                         hop_data,
  87                         hmac,
  88                 })
  89         }
  90 }
  91
  92 /// Onion message payloads contain "control" TLVs and "data" TLVs. Control TLVs are used to route
  93 /// the onion message from hop to hop and for path verification, whereas data TLVs contain the onion
  94 /// message content itself, such as an invoice request.
  95 pub(super) enum Payload<T: CustomOnionMessageContents> {
  96         /// This payload is for an intermediate hop.
  97         Forward(ForwardControlTlvs),
  98         /// This payload is for the final hop.
  99         Receive {
 100                 control_tlvs: ReceiveControlTlvs,
 101                 reply_path: Option<BlindedRoute>,
 102                 message: OnionMessageContents<T>,
 103         }
 104 }
 105
 106 #[derive(Debug)]
 107 /// The contents of an onion message. In the context of offers, this would be the invoice, invoice
 108 /// request, or invoice error.
 109 pub enum OnionMessageContents<T> where T: CustomOnionMessageContents {
 110         // Coming soon:
 111         // Invoice,
 112         // InvoiceRequest,
 113         // InvoiceError,
 114         /// A custom onion message specified by the user.
 115         Custom(T),
 116 }
 117
 118 impl<T> OnionMessageContents<T> where T: CustomOnionMessageContents {
 119         /// Returns the type that was used to decode the message payload.
 120         pub fn tlv_type(&self) -> u64 {
 121                 match self {
 122                         &OnionMessageContents::Custom(ref msg) => msg.tlv_type(),
 123                 }
 124         }
 125 }
 126
 127 impl<T: CustomOnionMessageContents> Writeable for OnionMessageContents<T> {
 128         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 129                 match self {
 130                         OnionMessageContents::Custom(msg) => Ok(msg.write(w)?),
 131                 }
 132         }
 133 }
 134
 135 /// The contents of a custom onion message. Must implement `MaybeReadableArgs<u64>` where the `u64`
 136 /// is the custom TLV type attempting to be read, and return `Ok(None)` if the TLV type is unknown.
 137 pub trait CustomOnionMessageContents: Writeable + MaybeReadableArgs<u64> {
 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<T: CustomOnionMessageContents> ReadableArgs<SharedSecret> for Payload<T> {
 202         fn read<R: Read>(r: &mut R, encrypted_tlvs_ss: SharedSecret) -> Result<Self, DecodeError> {
 203                 let v: BigSize = Readable::read(r)?;
 204                 let mut rd = FixedLengthReader::new(r, v.0);
 205                 let mut reply_path: Option<BlindedRoute> = None;
 206                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 207                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 208                 let mut message_type: Option<u64> = None;
 209                 let mut message = None;
 210                 decode_tlv_stream!(&mut rd, {
 211                         (2, reply_path, option),
 212                         (4, read_adapter, (option: LengthReadableArgs, rho)),
 213                 }, |msg_type, msg_reader| {
 214                         if msg_type < 64 { return Ok(false) }
 215                         // Don't allow reading more than one data TLV from an onion message.
 216                         if message_type.is_some() { return Err(DecodeError::InvalidValue) }
 217
 218                         message_type = Some(msg_type);
 219                         match T::read(msg_reader, msg_type) {
 220                                 Ok(Some(msg)) => {
 221                                         message = Some(msg);
 222                                         Ok(true)
 223                                 },
 224                                 Ok(None) => Ok(false),
 225                                 Err(e) => Err(e),
 226                         }
 227                 });
 228                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 229
 230                 match read_adapter {
 231                         None => return Err(DecodeError::InvalidValue),
 232                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 233                                 if message_type.is_some() {
 234                                         return Err(DecodeError::InvalidValue)
 235                                 }
 236                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 237                         },
 238                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 239                                 if message.is_none() { return Err(DecodeError::InvalidValue) }
 240                                 Ok(Payload::Receive {
 241                                         control_tlvs: ReceiveControlTlvs::Unblinded(tlvs),
 242                                         reply_path,
 243                                         message: OnionMessageContents::Custom(message.unwrap()),
 244                                 })
 245                         }
 246                 }
 247         }
 248 }
 249
 250 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 251 /// or received. Thus we read a ControlTlvs rather than reading a ForwardControlTlvs or
 252 /// ReceiveControlTlvs directly.
 253 pub(super) enum ControlTlvs {
 254         /// This onion message is intended to be forwarded.
 255         Forward(ForwardTlvs),
 256         /// This onion message is intended to be received.
 257         Receive(ReceiveTlvs),
 258 }
 259
 260 impl Readable for ControlTlvs {
 261         fn read<R: Read>(mut r: &mut R) -> Result<Self, DecodeError> {
 262                 let mut _padding: Option<Padding> = None;
 263                 let mut _short_channel_id: Option<u64> = None;
 264                 let mut next_node_id: Option<PublicKey> = None;
 265                 let mut path_id: Option<[u8; 32]> = None;
 266                 let mut next_blinding_override: Option<PublicKey> = None;
 267                 decode_tlv_stream!(&mut r, {
 268                         (1, _padding, option),
 269                         (2, _short_channel_id, option),
 270                         (4, next_node_id, option),
 271                         (6, path_id, option),
 272                         (8, next_blinding_override, option),
 273                 });
 274
 275                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 276                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 277
 278                 let payload_fmt = if valid_fwd_fmt {
 279                         ControlTlvs::Forward(ForwardTlvs {
 280                                 next_node_id: next_node_id.unwrap(),
 281                                 next_blinding_override,
 282                         })
 283                 } else if valid_recv_fmt {
 284                         ControlTlvs::Receive(ReceiveTlvs {
 285                                 path_id,
 286                         })
 287                 } else {
 288                         return Err(DecodeError::InvalidValue)
 289                 };
 290
 291                 Ok(payload_fmt)
 292         }
 293 }
 294
 295 /// Reads padding to the end, ignoring what's read.
 296 pub(crate) struct Padding {}
 297 impl Readable for Padding {
 298         #[inline]
 299         fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
 300                 loop {
 301                         let mut buf = [0; 8192];
 302                         if reader.read(&mut buf[..])? == 0 { break; }
 303                 }
 304                 Ok(Self {})
 305         }
 306 }