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 paths and related utilities live here.
14 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
16 use crate::sign::{EntropySource, NodeSigner, Recipient};
17 use crate::onion_message::ControlTlvs;
18 use crate::ln::msgs::DecodeError;
19 use crate::ln::onion_utils;
20 use crate::util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
21 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Readable, VecWriter, Writeable, Writer};
25 use crate::io::{self, Cursor};
26 use crate::prelude::*;
28 /// Onion messages and payments can be sent and received to blinded paths, which serve to hide the
29 /// identity of the recipient.
30 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
31 pub struct BlindedPath {
32 /// To send to a blinded path, 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 or payment's next hop and forward it along.
36 /// [`encrypted_payload`]: BlindedHop::encrypted_payload
37 pub introduction_node_id: PublicKey,
38 /// Used by the introduction node to decrypt its [`encrypted_payload`] to forward the onion
39 /// message or payment.
41 /// [`encrypted_payload`]: BlindedHop::encrypted_payload
42 pub blinding_point: PublicKey,
43 /// The hops composing the blinded path.
44 pub blinded_hops: Vec<BlindedHop>,
47 /// Used to construct the blinded hops portion of a blinded path. These hops cannot be identified
48 /// by outside observers and thus can be used to hide the identity of the recipient.
49 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
50 pub struct BlindedHop {
51 /// The blinded node id of this hop in a blinded path.
52 pub blinded_node_id: PublicKey,
53 /// The encrypted payload intended for this hop in a blinded path.
54 // The node sending to this blinded path will later encode this payload into the onion packet for
56 pub encrypted_payload: Vec<u8>,
60 /// Create a blinded path for an onion message, to be forwarded along `node_pks`. The last node
61 /// pubkey in `node_pks` will be the destination node.
63 /// Errors if less than two hops are provided or if `node_pk`(s) are invalid.
64 // TODO: make all payloads the same size with padding + add dummy hops
65 pub fn new_for_message<ES: EntropySource, T: secp256k1::Signing + secp256k1::Verification>
66 (node_pks: &[PublicKey], entropy_source: &ES, secp_ctx: &Secp256k1<T>) -> Result<Self, ()>
68 if node_pks.len() < 2 { return Err(()) }
69 let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
70 let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
71 let introduction_node_id = node_pks[0];
75 blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
76 blinded_hops: blinded_message_hops(secp_ctx, node_pks, &blinding_secret).map_err(|_| ())?,
80 // Advance the blinded onion message path by one hop, so make the second hop into the new
82 pub(super) fn advance_message_path_by_one<NS: Deref, T: secp256k1::Signing + secp256k1::Verification>
83 (&mut self, node_signer: &NS, secp_ctx: &Secp256k1<T>) -> Result<(), ()>
84 where NS::Target: NodeSigner
86 let control_tlvs_ss = node_signer.ecdh(Recipient::Node, &self.blinding_point, None)?;
87 let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
88 let encrypted_control_tlvs = self.blinded_hops.remove(0).encrypted_payload;
89 let mut s = Cursor::new(&encrypted_control_tlvs);
90 let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
91 match ChaChaPolyReadAdapter::read(&mut reader, rho) {
92 Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(ForwardTlvs {
93 mut next_node_id, next_blinding_override,
95 let mut new_blinding_point = match next_blinding_override {
96 Some(blinding_point) => blinding_point,
98 onion_utils::next_hop_pubkey(secp_ctx, self.blinding_point,
99 control_tlvs_ss.as_ref()).map_err(|_| ())?
102 mem::swap(&mut self.blinding_point, &mut new_blinding_point);
103 mem::swap(&mut self.introduction_node_id, &mut next_node_id);
111 /// Construct blinded onion message hops for the given `unblinded_path`.
112 fn blinded_message_hops<T: secp256k1::Signing + secp256k1::Verification>(
113 secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
114 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
115 let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
117 let mut prev_ss_and_blinded_node_id = None;
118 utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
119 if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
120 if let Some(pk) = unblinded_pk {
121 let payload = ForwardTlvs {
123 next_blinding_override: None,
125 blinded_hops.push(BlindedHop {
126 blinded_node_id: prev_blinded_node_id,
127 encrypted_payload: encrypt_payload(payload, prev_ss),
129 } else { debug_assert!(false); }
131 prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
134 if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
135 let final_payload = ReceiveTlvs { path_id: None };
136 blinded_hops.push(BlindedHop {
137 blinded_node_id: final_blinded_node_id,
138 encrypted_payload: encrypt_payload(final_payload, final_ss),
140 } else { debug_assert!(false) }
145 /// Encrypt TLV payload to be used as a [`BlindedHop::encrypted_payload`].
146 fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
147 let mut writer = VecWriter(Vec::new());
148 let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
149 write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
153 impl Writeable for BlindedPath {
154 fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
155 self.introduction_node_id.write(w)?;
156 self.blinding_point.write(w)?;
157 (self.blinded_hops.len() as u8).write(w)?;
158 for hop in &self.blinded_hops {
165 impl Readable for BlindedPath {
166 fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
167 let introduction_node_id = Readable::read(r)?;
168 let blinding_point = Readable::read(r)?;
169 let num_hops: u8 = Readable::read(r)?;
170 if num_hops == 0 { return Err(DecodeError::InvalidValue) }
171 let mut blinded_hops: Vec<BlindedHop> = Vec::with_capacity(num_hops.into());
172 for _ in 0..num_hops {
173 blinded_hops.push(Readable::read(r)?);
176 introduction_node_id,
183 impl_writeable!(BlindedHop, {
188 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
189 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
190 pub(crate) struct ForwardTlvs {
191 /// The node id of the next hop in the onion message's path.
192 pub(super) next_node_id: PublicKey,
193 /// Senders to a blinded path use this value to concatenate the route they find to the
194 /// introduction node with the blinded path.
195 pub(super) next_blinding_override: Option<PublicKey>,
198 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
199 pub(crate) struct ReceiveTlvs {
200 /// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
201 /// sending to. This is useful for receivers to check that said blinded path is being used in
202 /// the right context.
203 pub(super) path_id: Option<[u8; 32]>,
206 impl Writeable for ForwardTlvs {
207 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
208 // TODO: write padding
209 encode_tlv_stream!(writer, {
210 (4, self.next_node_id, required),
211 (8, self.next_blinding_override, option)
217 impl Writeable for ReceiveTlvs {
218 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
219 // TODO: write padding
220 encode_tlv_stream!(writer, {
221 (6, self.path_id, option),