_ Git - rust-lightning/blob - lightning/src/blinded_path/message.rs

   1 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
   2
   3 use crate::blinded_path::{BlindedHop, BlindedPath};
   4 use crate::blinded_path::utils;
   5 use crate::io;
   6 use crate::io::Cursor;
   7 use crate::ln::onion_utils;
   8 use crate::onion_message::packet::ControlTlvs;
   9 use crate::prelude::*;
  10 use crate::sign::{NodeSigner, Recipient};
  11 use crate::util::chacha20poly1305rfc::ChaChaPolyReadAdapter;
  12 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Writeable, Writer};
  13
  14 use core::mem;
  15 use core::ops::Deref;
  16
  17 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
  18 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
  19 pub(crate) struct ForwardTlvs {
  20         /// The node id of the next hop in the onion message's path.
  21         pub(crate) next_node_id: PublicKey,
  22         /// Senders to a blinded path use this value to concatenate the route they find to the
  23         /// introduction node with the blinded path.
  24         pub(crate) next_blinding_override: Option<PublicKey>,
  25 }
  26
  27 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
  28 pub(crate) struct ReceiveTlvs {
  29         /// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
  30         /// sending to. This is useful for receivers to check that said blinded path is being used in
  31         /// the right context.
  32         pub(crate) path_id: Option<[u8; 32]>,
  33 }
  34
  35 impl Writeable for ForwardTlvs {
  36         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  37                 // TODO: write padding
  38                 encode_tlv_stream!(writer, {
  39                         (4, self.next_node_id, required),
  40                         (8, self.next_blinding_override, option)
  41                 });
  42                 Ok(())
  43         }
  44 }
  45
  46 impl Writeable for ReceiveTlvs {
  47         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  48                 // TODO: write padding
  49                 encode_tlv_stream!(writer, {
  50                         (6, self.path_id, option),
  51                 });
  52                 Ok(())
  53         }
  54 }
  55
  56 /// Construct blinded onion message hops for the given `unblinded_path`.
  57 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
  58         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
  59 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
  60         let blinded_tlvs = unblinded_path.iter()
  61                 .skip(1) // The first node's TLVs contains the next node's pubkey
  62                 .map(|pk| {
  63                         ControlTlvs::Forward(ForwardTlvs { next_node_id: *pk, next_blinding_override: None })
  64                 })
  65                 .chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs { path_id: None })));
  66
  67         utils::construct_blinded_hops(secp_ctx, unblinded_path.iter(), blinded_tlvs, session_priv)
  68 }
  69
  70 // Advance the blinded onion message path by one hop, so make the second hop into the new
  71 // introduction node.
  72 pub(crate) fn advance_path_by_one<NS: Deref, T: secp256k1::Signing + secp256k1::Verification>(
  73         path: &mut BlindedPath, node_signer: &NS, secp_ctx: &Secp256k1<T>
  74 ) -> Result<(), ()> where NS::Target: NodeSigner {
  75         let control_tlvs_ss = node_signer.ecdh(Recipient::Node, &path.blinding_point, None)?;
  76         let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
  77         let encrypted_control_tlvs = path.blinded_hops.remove(0).encrypted_payload;
  78         let mut s = Cursor::new(&encrypted_control_tlvs);
  79         let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
  80         match ChaChaPolyReadAdapter::read(&mut reader, rho) {
  81                 Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(ForwardTlvs {
  82                         mut next_node_id, next_blinding_override,
  83                 })}) => {
  84                         let mut new_blinding_point = match next_blinding_override {
  85                                 Some(blinding_point) => blinding_point,
  86                                 None => {
  87                                         onion_utils::next_hop_pubkey(secp_ctx, path.blinding_point,
  88                                                 control_tlvs_ss.as_ref()).map_err(|_| ())?
  89                                 }
  90                         };
  91                         mem::swap(&mut path.blinding_point, &mut new_blinding_point);
  92                         mem::swap(&mut path.introduction_node_id, &mut next_node_id);
  93                         Ok(())
  94                 },
  95                 _ => Err(())
  96         }
  97 }