git.bitcoin.ninja 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::{BlindedHop, BlindedPath};
  19 use crate::ln::msgs::DecodeError;
  20 use crate::ln::onion_utils;
  21 use crate::onion_message::Destination;
  22 use crate::util::chacha20poly1305rfc::ChaChaPolyWriteAdapter;
  23 use crate::util::ser::{Readable, Writeable};
  24
  25 use crate::io;
  26 use crate::prelude::*;
  27
  28 // TODO: DRY with onion_utils::construct_onion_keys_callback
  29 #[inline]
  30 pub(crate) fn construct_keys_callback<'a, T, I, F>(
  31         secp_ctx: &Secp256k1<T>, unblinded_path: I, destination: Option<Destination>,
  32         session_priv: &SecretKey, mut callback: F
  33 ) -> Result<(), secp256k1::Error>
  34 where
  35         T: secp256k1::Signing + secp256k1::Verification,
  36         I: Iterator<Item=&'a PublicKey>,
  37         F: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>, Option<Vec<u8>>),
  38 {
  39         let mut msg_blinding_point_priv = session_priv.clone();
  40         let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  41         let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
  42         let mut onion_packet_pubkey = msg_blinding_point.clone();
  43
  44         macro_rules! build_keys {
  45                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {{
  46                         let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
  47
  48                         let blinded_hop_pk = if $blinded { $pk } else {
  49                                 let hop_pk_blinding_factor = {
  50                                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
  51                                         hmac.input(encrypted_data_ss.as_ref());
  52                                         Hmac::from_engine(hmac).to_byte_array()
  53                                 };
  54                                 $pk.mul_tweak(secp_ctx, &Scalar::from_be_bytes(hop_pk_blinding_factor).unwrap())?
  55                         };
  56                         let onion_packet_ss = SharedSecret::new(&blinded_hop_pk, &onion_packet_pubkey_priv);
  57
  58                         let rho = onion_utils::gen_rho_from_shared_secret(encrypted_data_ss.as_ref());
  59                         let unblinded_pk_opt = if $blinded { None } else { Some($pk) };
  60                         callback(blinded_hop_pk, onion_packet_ss, onion_packet_pubkey, rho, unblinded_pk_opt, $encrypted_payload);
  61                         (encrypted_data_ss, onion_packet_ss)
  62                 }}
  63         }
  64
  65         macro_rules! build_keys_in_loop {
  66                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {
  67                         let (encrypted_data_ss, onion_packet_ss) = build_keys!($pk, $blinded, $encrypted_payload);
  68
  69                         let msg_blinding_point_blinding_factor = {
  70                                 let mut sha = Sha256::engine();
  71                                 sha.input(&msg_blinding_point.serialize()[..]);
  72                                 sha.input(encrypted_data_ss.as_ref());
  73                                 Sha256::from_engine(sha).to_byte_array()
  74                         };
  75
  76                         msg_blinding_point_priv = msg_blinding_point_priv.mul_tweak(&Scalar::from_be_bytes(msg_blinding_point_blinding_factor).unwrap())?;
  77                         msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  78
  79                         let onion_packet_pubkey_blinding_factor = {
  80                                 let mut sha = Sha256::engine();
  81                                 sha.input(&onion_packet_pubkey.serialize()[..]);
  82                                 sha.input(onion_packet_ss.as_ref());
  83                                 Sha256::from_engine(sha).to_byte_array()
  84                         };
  85                         onion_packet_pubkey_priv = onion_packet_pubkey_priv.mul_tweak(&Scalar::from_be_bytes(onion_packet_pubkey_blinding_factor).unwrap())?;
  86                         onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
  87                 };
  88         }
  89
  90         for pk in unblinded_path {
  91                 build_keys_in_loop!(*pk, false, None);
  92         }
  93         if let Some(dest) = destination {
  94                 match dest {
  95                         Destination::Node(pk) => {
  96                                 build_keys!(pk, false, None);
  97                         },
  98                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => {
  99                                 for hop in blinded_hops {
 100                                         build_keys_in_loop!(hop.blinded_node_id, true, Some(hop.encrypted_payload));
 101                                 }
 102                         },
 103                 }
 104         }
 105         Ok(())
 106 }
 107
 108 // Panics if `unblinded_tlvs` length is less than `unblinded_pks` length
 109 pub(super) fn construct_blinded_hops<'a, T, I1, I2>(
 110         secp_ctx: &Secp256k1<T>, unblinded_pks: I1, mut unblinded_tlvs: I2, session_priv: &SecretKey
 111 ) -> Result<Vec<BlindedHop>, secp256k1::Error>
 112 where
 113         T: secp256k1::Signing + secp256k1::Verification,
 114         I1: Iterator<Item=&'a PublicKey>,
 115         I2: Iterator,
 116         I2::Item: Writeable
 117 {
 118         let mut blinded_hops = Vec::with_capacity(unblinded_pks.size_hint().0);
 119         construct_keys_callback(
 120                 secp_ctx, unblinded_pks, None, session_priv,
 121                 |blinded_node_id, _, _, encrypted_payload_rho, _, _| {
 122                         blinded_hops.push(BlindedHop {
 123                                 blinded_node_id,
 124                                 encrypted_payload: encrypt_payload(unblinded_tlvs.next().unwrap(), encrypted_payload_rho),
 125                         });
 126                 })?;
 127         Ok(blinded_hops)
 128 }
 129
 130 /// Encrypt TLV payload to be used as a [`crate::blinded_path::BlindedHop::encrypted_payload`].
 131 fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_rho: [u8; 32]) -> Vec<u8> {
 132         let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_rho, &payload);
 133         write_adapter.encode()
 134 }
 135
 136 /// Blinded path encrypted payloads may be padded to ensure they are equal length.
 137 ///
 138 /// Reads padding to the end, ignoring what's read.
 139 pub(crate) struct Padding {}
 140 impl Readable for Padding {
 141         #[inline]
 142         fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 143                 loop {
 144                         let mut buf = [0; 8192];
 145                         if reader.read(&mut buf[..])? == 0 { break; }
 146                 }
 147                 Ok(Self {})
 148         }
 149 }