_ 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 {
  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                 // Coming soon:
 103                 // message: Message,
 104         }
 105 }
 106
 107 // Coming soon:
 108 // enum Message {
 109 //      InvoiceRequest(InvoiceRequest),
 110 //      Invoice(Invoice),
 111 //      InvoiceError(InvoiceError),
 112 //      CustomMessage<T>,
 113 // }
 114
 115 /// The contents of a custom onion message. Must implement `MaybeReadableArgs<u64>` where the `u64`
 116 /// is the custom TLV type attempting to be read, and return `Ok(None)` if the TLV type is unknown.
 117 pub trait CustomOnionMessageContents: Writeable + MaybeReadableArgs<u64> {
 118         /// Returns the TLV type identifying the message contents. MUST be >= 64.
 119         fn tlv_type(&self) -> u64;
 120 }
 121
 122 /// Forward control TLVs in their blinded and unblinded form.
 123 pub(super) enum ForwardControlTlvs {
 124         /// If we're sending to a blinded route, the node that constructed the blinded route has provided
 125         /// this hop's control TLVs, already encrypted into bytes.
 126         Blinded(Vec<u8>),
 127         /// If we're constructing an onion message hop through an intermediate unblinded node, we'll need
 128         /// to construct the intermediate hop's control TLVs in their unblinded state to avoid encoding
 129         /// them into an intermediate Vec. See [`super::blinded_route::ForwardTlvs`] for more info.
 130         Unblinded(ForwardTlvs),
 131 }
 132
 133 /// Receive control TLVs in their blinded and unblinded form.
 134 pub(super) enum ReceiveControlTlvs {
 135         /// See [`ForwardControlTlvs::Blinded`].
 136         Blinded(Vec<u8>),
 137         /// See [`ForwardControlTlvs::Unblinded`] and [`super::blinded_route::ReceiveTlvs`].
 138         Unblinded(ReceiveTlvs),
 139 }
 140
 141 // Uses the provided secret to simultaneously encode and encrypt the unblinded control TLVs.
 142 impl Writeable for (Payload, [u8; 32]) {
 143         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 144                 match &self.0 {
 145                         Payload::Forward(ForwardControlTlvs::Blinded(encrypted_bytes)) => {
 146                                 encode_varint_length_prefixed_tlv!(w, {
 147                                         (4, encrypted_bytes, vec_type)
 148                                 })
 149                         },
 150                         Payload::Receive {
 151                                 control_tlvs: ReceiveControlTlvs::Blinded(encrypted_bytes), reply_path
 152                         } => {
 153                                 encode_varint_length_prefixed_tlv!(w, {
 154                                         (2, reply_path, option),
 155                                         (4, encrypted_bytes, vec_type)
 156                                 })
 157                         },
 158                         Payload::Forward(ForwardControlTlvs::Unblinded(control_tlvs)) => {
 159                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 160                                 encode_varint_length_prefixed_tlv!(w, {
 161                                         (4, write_adapter, required)
 162                                 })
 163                         },
 164                         Payload::Receive {
 165                                 control_tlvs: ReceiveControlTlvs::Unblinded(control_tlvs), reply_path,
 166                         } => {
 167                                 let write_adapter = ChaChaPolyWriteAdapter::new(self.1, &control_tlvs);
 168                                 encode_varint_length_prefixed_tlv!(w, {
 169                                         (2, reply_path, option),
 170                                         (4, write_adapter, required)
 171                                 })
 172                         },
 173                 }
 174                 Ok(())
 175         }
 176 }
 177
 178 // Uses the provided secret to simultaneously decode and decrypt the control TLVs.
 179 impl ReadableArgs<SharedSecret> for Payload {
 180         fn read<R: Read>(r: &mut R, encrypted_tlvs_ss: SharedSecret) -> Result<Self, DecodeError> {
 181                 let v: BigSize = Readable::read(r)?;
 182                 let mut rd = FixedLengthReader::new(r, v.0);
 183                 let mut reply_path: Option<BlindedRoute> = None;
 184                 let mut read_adapter: Option<ChaChaPolyReadAdapter<ControlTlvs>> = None;
 185                 let rho = onion_utils::gen_rho_from_shared_secret(&encrypted_tlvs_ss.secret_bytes());
 186                 decode_tlv_stream!(&mut rd, {
 187                         (2, reply_path, option),
 188                         (4, read_adapter, (option: LengthReadableArgs, rho))
 189                 });
 190                 rd.eat_remaining().map_err(|_| DecodeError::ShortRead)?;
 191
 192                 match read_adapter {
 193                         None => return Err(DecodeError::InvalidValue),
 194                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(tlvs)}) => {
 195                                 Ok(Payload::Forward(ForwardControlTlvs::Unblinded(tlvs)))
 196                         },
 197                         Some(ChaChaPolyReadAdapter { readable: ControlTlvs::Receive(tlvs)}) => {
 198                                 Ok(Payload::Receive { control_tlvs: ReceiveControlTlvs::Unblinded(tlvs), reply_path })
 199                         },
 200                 }
 201         }
 202 }
 203
 204 /// When reading a packet off the wire, we don't know a priori whether the packet is to be forwarded
 205 /// or received. Thus we read a ControlTlvs rather than reading a ForwardControlTlvs or
 206 /// ReceiveControlTlvs directly.
 207 pub(super) enum ControlTlvs {
 208         /// This onion message is intended to be forwarded.
 209         Forward(ForwardTlvs),
 210         /// This onion message is intended to be received.
 211         Receive(ReceiveTlvs),
 212 }
 213
 214 impl Readable for ControlTlvs {
 215         fn read<R: Read>(mut r: &mut R) -> Result<Self, DecodeError> {
 216                 let mut _padding: Option<Padding> = None;
 217                 let mut _short_channel_id: Option<u64> = None;
 218                 let mut next_node_id: Option<PublicKey> = None;
 219                 let mut path_id: Option<[u8; 32]> = None;
 220                 let mut next_blinding_override: Option<PublicKey> = None;
 221                 decode_tlv_stream!(&mut r, {
 222                         (1, _padding, option),
 223                         (2, _short_channel_id, option),
 224                         (4, next_node_id, option),
 225                         (6, path_id, option),
 226                         (8, next_blinding_override, option),
 227                 });
 228
 229                 let valid_fwd_fmt  = next_node_id.is_some() && path_id.is_none();
 230                 let valid_recv_fmt = next_node_id.is_none() && next_blinding_override.is_none();
 231
 232                 let payload_fmt = if valid_fwd_fmt {
 233                         ControlTlvs::Forward(ForwardTlvs {
 234                                 next_node_id: next_node_id.unwrap(),
 235                                 next_blinding_override,
 236                         })
 237                 } else if valid_recv_fmt {
 238                         ControlTlvs::Receive(ReceiveTlvs {
 239                                 path_id,
 240                         })
 241                 } else {
 242                         return Err(DecodeError::InvalidValue)
 243                 };
 244
 245                 Ok(payload_fmt)
 246         }
 247 }
 248
 249 /// Reads padding to the end, ignoring what's read.
 250 pub(crate) struct Padding {}
 251 impl Readable for Padding {
 252         #[inline]
 253         fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
 254                 loop {
 255                         let mut buf = [0; 8192];
 256                         if reader.read(&mut buf[..])? == 0 { break; }
 257                 }
 258                 Ok(Self {})
 259         }
 260 }