git.bitcoin.ninja 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, Scalar};
  16 use bitcoin::secp256k1::ecdh::SharedSecret;
  17
  18 use crate::ln::onion_utils;
  19 use super::blinded_path::BlindedPath;
  20 use super::messenger::Destination;
  21
  22 use crate::prelude::*;
  23
  24 // TODO: DRY with onion_utils::construct_onion_keys_callback
  25 #[inline]
  26 pub(super) fn construct_keys_callback<T: secp256k1::Signing + secp256k1::Verification,
  27         FType: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>, Option<Vec<u8>>)>(
  28         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Option<Destination>,
  29         session_priv: &SecretKey, mut callback: FType
  30 ) -> Result<(), secp256k1::Error> {
  31         let mut msg_blinding_point_priv = session_priv.clone();
  32         let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  33         let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
  34         let mut onion_packet_pubkey = msg_blinding_point.clone();
  35
  36         macro_rules! build_keys {
  37                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {{
  38                         let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
  39
  40                         let blinded_hop_pk = if $blinded { $pk } else {
  41                                 let hop_pk_blinding_factor = {
  42                                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
  43                                         hmac.input(encrypted_data_ss.as_ref());
  44                                         Hmac::from_engine(hmac).into_inner()
  45                                 };
  46                                 $pk.mul_tweak(secp_ctx, &Scalar::from_be_bytes(hop_pk_blinding_factor).unwrap())?
  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, $encrypted_payload);
  53                         (encrypted_data_ss, onion_packet_ss)
  54                 }}
  55         }
  56
  57         macro_rules! build_keys_in_loop {
  58                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {
  59                         let (encrypted_data_ss, onion_packet_ss) = build_keys!($pk, $blinded, $encrypted_payload);
  60
  61                         let msg_blinding_point_blinding_factor = {
  62                                 let mut sha = Sha256::engine();
  63                                 sha.input(&msg_blinding_point.serialize()[..]);
  64                                 sha.input(encrypted_data_ss.as_ref());
  65                                 Sha256::from_engine(sha).into_inner()
  66                         };
  67
  68                         msg_blinding_point_priv = msg_blinding_point_priv.mul_tweak(&Scalar::from_be_bytes(msg_blinding_point_blinding_factor).unwrap())?;
  69                         msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  70
  71                         let onion_packet_pubkey_blinding_factor = {
  72                                 let mut sha = Sha256::engine();
  73                                 sha.input(&onion_packet_pubkey.serialize()[..]);
  74                                 sha.input(onion_packet_ss.as_ref());
  75                                 Sha256::from_engine(sha).into_inner()
  76                         };
  77                         onion_packet_pubkey_priv = onion_packet_pubkey_priv.mul_tweak(&Scalar::from_be_bytes(onion_packet_pubkey_blinding_factor).unwrap())?;
  78                         onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
  79                 };
  80         }
  81
  82         for pk in unblinded_path {
  83                 build_keys_in_loop!(*pk, false, None);
  84         }
  85         if let Some(dest) = destination {
  86                 match dest {
  87                         Destination::Node(pk) => {
  88                                 build_keys!(pk, false, None);
  89                         },
  90                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => {
  91                                 for hop in blinded_hops {
  92                                         build_keys_in_loop!(hop.blinded_node_id, true, Some(hop.encrypted_payload));
  93                                 }
  94                         },
  95                 }
  96         }
  97         Ok(())
  98 }