1 // This file is Copyright its original authors, visible in version control
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
10 //! Creating blinded routes and related utilities live here.
12 use bitcoin::hashes::{Hash, HashEngine};
13 use bitcoin::hashes::sha256::Hash as Sha256;
14 use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
16 use crate::chain::keysinterface::{KeysInterface, Recipient};
17 use super::packet::ControlTlvs;
19 use crate::ln::msgs::DecodeError;
20 use crate::ln::onion_utils;
21 use crate::util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
22 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Readable, VecWriter, Writeable, Writer};
26 use crate::io::{self, Cursor};
27 use crate::prelude::*;
29 /// Onion messages can be sent and received to blinded routes, which serve to hide the identity of
31 pub struct BlindedRoute {
32 /// To send to a blinded route, the sender first finds a route to the unblinded
33 /// `introduction_node_id`, which can unblind its [`encrypted_payload`] to find out the onion
34 /// message's next hop and forward it along.
36 /// [`encrypted_payload`]: BlindedHop::encrypted_payload
37 pub(super) introduction_node_id: PublicKey,
38 /// Used by the introduction node to decrypt its [`encrypted_payload`] to forward the onion
41 /// [`encrypted_payload`]: BlindedHop::encrypted_payload
42 pub(super) blinding_point: PublicKey,
43 /// The hops composing the blinded route.
44 pub(super) blinded_hops: Vec<BlindedHop>,
47 /// Used to construct the blinded hops portion of a blinded route. These hops cannot be identified
48 /// by outside observers and thus can be used to hide the identity of the recipient.
49 pub struct BlindedHop {
50 /// The blinded node id of this hop in a blinded route.
51 pub(super) blinded_node_id: PublicKey,
52 /// The encrypted payload intended for this hop in a blinded route.
53 // The node sending to this blinded route will later encode this payload into the onion packet for
55 pub(super) encrypted_payload: Vec<u8>,
59 /// Create a blinded route to be forwarded along `node_pks`. The last node pubkey in `node_pks`
60 /// will be the destination node.
62 /// Errors if less than two hops are provided or if `node_pk`(s) are invalid.
63 // TODO: make all payloads the same size with padding + add dummy hops
64 pub fn new<K: KeysInterface, T: secp256k1::Signing + secp256k1::Verification>
65 (node_pks: &[PublicKey], keys_manager: &K, secp_ctx: &Secp256k1<T>) -> Result<Self, ()>
67 if node_pks.len() < 2 { return Err(()) }
68 let blinding_secret_bytes = keys_manager.get_secure_random_bytes();
69 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
70 let introduction_node_id = node_pks[0];
74 blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
75 blinded_hops: blinded_hops(secp_ctx, node_pks, &blinding_secret).map_err(|_| ())?,
79 // Advance the blinded route by one hop, so make the second hop into the new introduction node.
80 pub(super) fn advance_by_one<K: Deref, T: secp256k1::Signing + secp256k1::Verification>
81 (&mut self, keys_manager: &K, secp_ctx: &Secp256k1<T>) -> Result<(), ()>
82 where K::Target: KeysInterface
84 let control_tlvs_ss = keys_manager.ecdh(Recipient::Node, &self.blinding_point, None)?;
85 let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
86 let encrypted_control_tlvs = self.blinded_hops.remove(0).encrypted_payload;
87 let mut s = Cursor::new(&encrypted_control_tlvs);
88 let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
89 match ChaChaPolyReadAdapter::read(&mut reader, rho) {
90 Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(ForwardTlvs {
91 mut next_node_id, next_blinding_override,
93 let mut new_blinding_point = match next_blinding_override {
94 Some(blinding_point) => blinding_point,
96 let blinding_factor = {
97 let mut sha = Sha256::engine();
98 sha.input(&self.blinding_point.serialize()[..]);
99 sha.input(control_tlvs_ss.as_ref());
100 Sha256::from_engine(sha).into_inner()
102 self.blinding_point.mul_tweak(secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap())
106 mem::swap(&mut self.blinding_point, &mut new_blinding_point);
107 mem::swap(&mut self.introduction_node_id, &mut next_node_id);
115 /// Construct blinded hops for the given `unblinded_path`.
116 fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
117 secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
118 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
119 let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
121 let mut prev_ss_and_blinded_node_id = None;
122 utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
123 if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
124 if let Some(pk) = unblinded_pk {
125 let payload = ForwardTlvs {
127 next_blinding_override: None,
129 blinded_hops.push(BlindedHop {
130 blinded_node_id: prev_blinded_node_id,
131 encrypted_payload: encrypt_payload(payload, prev_ss),
133 } else { debug_assert!(false); }
135 prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
138 if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
139 let final_payload = ReceiveTlvs { path_id: None };
140 blinded_hops.push(BlindedHop {
141 blinded_node_id: final_blinded_node_id,
142 encrypted_payload: encrypt_payload(final_payload, final_ss),
144 } else { debug_assert!(false) }
149 /// Encrypt TLV payload to be used as a [`BlindedHop::encrypted_payload`].
150 fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
151 let mut writer = VecWriter(Vec::new());
152 let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
153 write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
157 impl Writeable for BlindedRoute {
158 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
159 self.introduction_node_id.write(w)?;
160 self.blinding_point.write(w)?;
161 (self.blinded_hops.len() as u8).write(w)?;
162 for hop in &self.blinded_hops {
169 impl Readable for BlindedRoute {
170 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
171 let introduction_node_id = Readable::read(r)?;
172 let blinding_point = Readable::read(r)?;
173 let num_hops: u8 = Readable::read(r)?;
174 if num_hops == 0 { return Err(DecodeError::InvalidValue) }
175 let mut blinded_hops: Vec<BlindedHop> = Vec::with_capacity(num_hops.into());
176 for _ in 0..num_hops {
177 blinded_hops.push(Readable::read(r)?);
180 introduction_node_id,
187 impl_writeable!(BlindedHop, {
192 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
193 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
194 pub(crate) struct ForwardTlvs {
195 /// The node id of the next hop in the onion message's path.
196 pub(super) next_node_id: PublicKey,
197 /// Senders to a blinded route use this value to concatenate the route they find to the
198 /// introduction node with the blinded route.
199 pub(super) next_blinding_override: Option<PublicKey>,
202 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
203 pub(crate) struct ReceiveTlvs {
204 /// If `path_id` is `Some`, it is used to identify the blinded route that this onion message is
205 /// sending to. This is useful for receivers to check that said blinded route is being used in
206 /// the right context.
207 pub(super) path_id: Option<[u8; 32]>,
210 impl Writeable for ForwardTlvs {
211 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
212 // TODO: write padding
213 encode_tlv_stream!(writer, {
214 (4, self.next_node_id, required),
215 (8, self.next_blinding_override, option)
221 impl Writeable for ReceiveTlvs {
222 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
223 // TODO: write padding
224 encode_tlv_stream!(writer, {
225 (6, self.path_id, option),