_ Git - rust-lightning/blob - lightning/src/blinded_path/utils.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 //! Onion message utility methods live here.
  11
  12 use bitcoin::hashes::{Hash, HashEngine};
  13 use bitcoin::hashes::hmac::{Hmac, HmacEngine};
  14 use bitcoin::hashes::sha256::Hash as Sha256;
  15 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey, Scalar};
  16 use bitcoin::secp256k1::ecdh::SharedSecret;
  17
  18 use super::BlindedPath;
  19 use crate::ln::onion_utils;
  20 use crate::onion_message::Destination;
  21 use crate::util::chacha20poly1305rfc::ChaChaPolyWriteAdapter;
  22 use crate::util::ser::{VecWriter, Writeable};
  23
  24 use crate::prelude::*;
  25
  26 // TODO: DRY with onion_utils::construct_onion_keys_callback
  27 #[inline]
  28 pub(crate) fn construct_keys_callback<T: secp256k1::Signing + secp256k1::Verification,
  29         FType: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>, Option<Vec<u8>>)>(
  30         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Option<Destination>,
  31         session_priv: &SecretKey, mut callback: FType
  32 ) -> Result<(), secp256k1::Error> {
  33         let mut msg_blinding_point_priv = session_priv.clone();
  34         let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  35         let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
  36         let mut onion_packet_pubkey = msg_blinding_point.clone();
  37
  38         macro_rules! build_keys {
  39                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {{
  40                         let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
  41
  42                         let blinded_hop_pk = if $blinded { $pk } else {
  43                                 let hop_pk_blinding_factor = {
  44                                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
  45                                         hmac.input(encrypted_data_ss.as_ref());
  46                                         Hmac::from_engine(hmac).into_inner()
  47                                 };
  48                                 $pk.mul_tweak(secp_ctx, &Scalar::from_be_bytes(hop_pk_blinding_factor).unwrap())?
  49                         };
  50                         let onion_packet_ss = SharedSecret::new(&blinded_hop_pk, &onion_packet_pubkey_priv);
  51
  52                         let rho = onion_utils::gen_rho_from_shared_secret(encrypted_data_ss.as_ref());
  53                         let unblinded_pk_opt = if $blinded { None } else { Some($pk) };
  54                         callback(blinded_hop_pk, onion_packet_ss, onion_packet_pubkey, rho, unblinded_pk_opt, $encrypted_payload);
  55                         (encrypted_data_ss, onion_packet_ss)
  56                 }}
  57         }
  58
  59         macro_rules! build_keys_in_loop {
  60                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {
  61                         let (encrypted_data_ss, onion_packet_ss) = build_keys!($pk, $blinded, $encrypted_payload);
  62
  63                         let msg_blinding_point_blinding_factor = {
  64                                 let mut sha = Sha256::engine();
  65                                 sha.input(&msg_blinding_point.serialize()[..]);
  66                                 sha.input(encrypted_data_ss.as_ref());
  67                                 Sha256::from_engine(sha).into_inner()
  68                         };
  69
  70                         msg_blinding_point_priv = msg_blinding_point_priv.mul_tweak(&Scalar::from_be_bytes(msg_blinding_point_blinding_factor).unwrap())?;
  71                         msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  72
  73                         let onion_packet_pubkey_blinding_factor = {
  74                                 let mut sha = Sha256::engine();
  75                                 sha.input(&onion_packet_pubkey.serialize()[..]);
  76                                 sha.input(onion_packet_ss.as_ref());
  77                                 Sha256::from_engine(sha).into_inner()
  78                         };
  79                         onion_packet_pubkey_priv = onion_packet_pubkey_priv.mul_tweak(&Scalar::from_be_bytes(onion_packet_pubkey_blinding_factor).unwrap())?;
  80                         onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
  81                 };
  82         }
  83
  84         for pk in unblinded_path {
  85                 build_keys_in_loop!(*pk, false, None);
  86         }
  87         if let Some(dest) = destination {
  88                 match dest {
  89                         Destination::Node(pk) => {
  90                                 build_keys!(pk, false, None);
  91                         },
  92                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => {
  93                                 for hop in blinded_hops {
  94                                         build_keys_in_loop!(hop.blinded_node_id, true, Some(hop.encrypted_payload));
  95                                 }
  96                         },
  97                 }
  98         }
  99         Ok(())
 100 }
 101
 102 /// Encrypt TLV payload to be used as a [`crate::blinded_path::BlindedHop::encrypted_payload`].
 103 pub(super) fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
 104         let mut writer = VecWriter(Vec::new());
 105         let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
 106         write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
 107         writer.0
 108 }
 109