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