_ Git - rust-lightning/blob - lightning/src/onion_message/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};
  16 use bitcoin::secp256k1::ecdh::SharedSecret;
  17
  18 use ln::onion_utils;
  19
  20 use prelude::*;
  21
  22 // TODO: DRY with onion_utils::construct_onion_keys_callback
  23 #[inline]
  24 pub(super) fn construct_keys_callback<T: secp256k1::Signing + secp256k1::Verification,
  25         FType: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>)>(
  26         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey],
  27         session_priv: &SecretKey, mut callback: FType
  28 ) -> Result<(), secp256k1::Error> {
  29         let mut msg_blinding_point_priv = session_priv.clone();
  30         let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  31         let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
  32         let mut onion_packet_pubkey = msg_blinding_point.clone();
  33
  34         macro_rules! build_keys {
  35                 ($pk: expr, $blinded: expr) => {
  36                         let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
  37
  38                         let blinded_hop_pk = if $blinded { $pk } else {
  39                                 let hop_pk_blinding_factor = {
  40                                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
  41                                         hmac.input(encrypted_data_ss.as_ref());
  42                                         Hmac::from_engine(hmac).into_inner()
  43                                 };
  44                                 let mut unblinded_pk = $pk;
  45                                 unblinded_pk.mul_assign(secp_ctx, &hop_pk_blinding_factor)?;
  46                                 unblinded_pk
  47                         };
  48                         let onion_packet_ss = SharedSecret::new(&blinded_hop_pk, &onion_packet_pubkey_priv);
  49
  50                         let rho = onion_utils::gen_rho_from_shared_secret(encrypted_data_ss.as_ref());
  51                         let unblinded_pk_opt = if $blinded { None } else { Some($pk) };
  52                         callback(blinded_hop_pk, onion_packet_ss, onion_packet_pubkey, rho, unblinded_pk_opt);
  53
  54                         let msg_blinding_point_blinding_factor = {
  55                                 let mut sha = Sha256::engine();
  56                                 sha.input(&msg_blinding_point.serialize()[..]);
  57                                 sha.input(encrypted_data_ss.as_ref());
  58                                 Sha256::from_engine(sha).into_inner()
  59                         };
  60
  61                         msg_blinding_point_priv.mul_assign(&msg_blinding_point_blinding_factor)?;
  62                         msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  63
  64                         let onion_packet_pubkey_blinding_factor = {
  65                                 let mut sha = Sha256::engine();
  66                                 sha.input(&onion_packet_pubkey.serialize()[..]);
  67                                 sha.input(onion_packet_ss.as_ref());
  68                                 Sha256::from_engine(sha).into_inner()
  69                         };
  70                         onion_packet_pubkey_priv.mul_assign(&onion_packet_pubkey_blinding_factor)?;
  71                         onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
  72                 };
  73         }
  74
  75         for pk in unblinded_path {
  76                 build_keys!(*pk, false);
  77         }
  78         Ok(())
  79 }