_ 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::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, VecWriter, 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<T: secp256k1::Signing + secp256k1::Verification,
  31         FType: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>, Option<Vec<u8>>)>(
  32         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Option<Destination>,
  33         session_priv: &SecretKey, mut callback: FType
  34 ) -> Result<(), secp256k1::Error> {
  35         let mut msg_blinding_point_priv = session_priv.clone();
  36         let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  37         let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
  38         let mut onion_packet_pubkey = msg_blinding_point.clone();
  39
  40         macro_rules! build_keys {
  41                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {{
  42                         let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
  43
  44                         let blinded_hop_pk = if $blinded { $pk } else {
  45                                 let hop_pk_blinding_factor = {
  46                                         let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
  47                                         hmac.input(encrypted_data_ss.as_ref());
  48                                         Hmac::from_engine(hmac).into_inner()
  49                                 };
  50                                 $pk.mul_tweak(secp_ctx, &Scalar::from_be_bytes(hop_pk_blinding_factor).unwrap())?
  51                         };
  52                         let onion_packet_ss = SharedSecret::new(&blinded_hop_pk, &onion_packet_pubkey_priv);
  53
  54                         let rho = onion_utils::gen_rho_from_shared_secret(encrypted_data_ss.as_ref());
  55                         let unblinded_pk_opt = if $blinded { None } else { Some($pk) };
  56                         callback(blinded_hop_pk, onion_packet_ss, onion_packet_pubkey, rho, unblinded_pk_opt, $encrypted_payload);
  57                         (encrypted_data_ss, onion_packet_ss)
  58                 }}
  59         }
  60
  61         macro_rules! build_keys_in_loop {
  62                 ($pk: expr, $blinded: expr, $encrypted_payload: expr) => {
  63                         let (encrypted_data_ss, onion_packet_ss) = build_keys!($pk, $blinded, $encrypted_payload);
  64
  65                         let msg_blinding_point_blinding_factor = {
  66                                 let mut sha = Sha256::engine();
  67                                 sha.input(&msg_blinding_point.serialize()[..]);
  68                                 sha.input(encrypted_data_ss.as_ref());
  69                                 Sha256::from_engine(sha).into_inner()
  70                         };
  71
  72                         msg_blinding_point_priv = msg_blinding_point_priv.mul_tweak(&Scalar::from_be_bytes(msg_blinding_point_blinding_factor).unwrap())?;
  73                         msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
  74
  75                         let onion_packet_pubkey_blinding_factor = {
  76                                 let mut sha = Sha256::engine();
  77                                 sha.input(&onion_packet_pubkey.serialize()[..]);
  78                                 sha.input(onion_packet_ss.as_ref());
  79                                 Sha256::from_engine(sha).into_inner()
  80                         };
  81                         onion_packet_pubkey_priv = onion_packet_pubkey_priv.mul_tweak(&Scalar::from_be_bytes(onion_packet_pubkey_blinding_factor).unwrap())?;
  82                         onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
  83                 };
  84         }
  85
  86         for pk in unblinded_path {
  87                 build_keys_in_loop!(*pk, false, None);
  88         }
  89         if let Some(dest) = destination {
  90                 match dest {
  91                         Destination::Node(pk) => {
  92                                 build_keys!(pk, false, None);
  93                         },
  94                         Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => {
  95                                 for hop in blinded_hops {
  96                                         build_keys_in_loop!(hop.blinded_node_id, true, Some(hop.encrypted_payload));
  97                                 }
  98                         },
  99                 }
 100         }
 101         Ok(())
 102 }
 103
 104 /// Encrypt TLV payload to be used as a [`crate::blinded_path::BlindedHop::encrypted_payload`].
 105 pub(super) fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
 106         let mut writer = VecWriter(Vec::new());
 107         let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
 108         write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
 109         writer.0
 110 }
 111
 112 /// Blinded path encrypted payloads may be padded to ensure they are equal length.
 113 ///
 114 /// Reads padding to the end, ignoring what's read.
 115 pub(crate) struct Padding {}
 116 impl Readable for Padding {
 117         #[inline]
 118         fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 119                 loop {
 120                         let mut buf = [0; 8192];
 121                         if reader.read(&mut buf[..])? == 0 { break; }
 122                 }
 123                 Ok(Self {})
 124         }
 125 }