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

   1 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
   2
   3 #[allow(unused_imports)]
   4 use crate::prelude::*;
   5
   6 use crate::blinded_path::{BlindedHop, BlindedPath, IntroductionNode, NodeIdLookUp};
   7 use crate::blinded_path::utils;
   8 use crate::io;
   9 use crate::io::Cursor;
  10 use crate::ln::onion_utils;
  11 use crate::onion_message::packet::ControlTlvs;
  12 use crate::sign::{NodeSigner, Recipient};
  13 use crate::crypto::streams::ChaChaPolyReadAdapter;
  14 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Writeable, Writer};
  15
  16 use core::mem;
  17 use core::ops::Deref;
  18
  19 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
  20 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
  21 pub(crate) struct ForwardTlvs {
  22         /// The next hop in the onion message's path.
  23         pub(crate) next_hop: NextHop,
  24         /// Senders to a blinded path use this value to concatenate the route they find to the
  25         /// introduction node with the blinded path.
  26         pub(crate) next_blinding_override: Option<PublicKey>,
  27 }
  28
  29 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
  30 pub(crate) struct ReceiveTlvs {
  31         /// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
  32         /// sending to. This is useful for receivers to check that said blinded path is being used in
  33         /// the right context.
  34         pub(crate) path_id: Option<[u8; 32]>,
  35 }
  36
  37 /// The next hop to forward the onion message along its path.
  38 #[derive(Debug)]
  39 pub enum NextHop {
  40         /// The node id of the next hop.
  41         NodeId(PublicKey),
  42         /// The short channel id leading to the next hop.
  43         ShortChannelId(u64),
  44 }
  45
  46 impl Writeable for ForwardTlvs {
  47         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  48                 let (next_node_id, short_channel_id) = match self.next_hop {
  49                         NextHop::NodeId(pubkey) => (Some(pubkey), None),
  50                         NextHop::ShortChannelId(scid) => (None, Some(scid)),
  51                 };
  52                 // TODO: write padding
  53                 encode_tlv_stream!(writer, {
  54                         (2, short_channel_id, option),
  55                         (4, next_node_id, option),
  56                         (8, self.next_blinding_override, option)
  57                 });
  58                 Ok(())
  59         }
  60 }
  61
  62 impl Writeable for ReceiveTlvs {
  63         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  64                 // TODO: write padding
  65                 encode_tlv_stream!(writer, {
  66                         (6, self.path_id, option),
  67                 });
  68                 Ok(())
  69         }
  70 }
  71
  72 /// Construct blinded onion message hops for the given `unblinded_path`.
  73 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
  74         secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
  75 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
  76         let blinded_tlvs = unblinded_path.iter()
  77                 .skip(1) // The first node's TLVs contains the next node's pubkey
  78                 .map(|pk| ForwardTlvs { next_hop: NextHop::NodeId(*pk), next_blinding_override: None })
  79                 .map(|tlvs| ControlTlvs::Forward(tlvs))
  80                 .chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs { path_id: None })));
  81
  82         utils::construct_blinded_hops(secp_ctx, unblinded_path.iter(), blinded_tlvs, session_priv)
  83 }
  84
  85 // Advance the blinded onion message path by one hop, so make the second hop into the new
  86 // introduction node.
  87 pub(crate) fn advance_path_by_one<NS: Deref, NL: Deref, T>(
  88         path: &mut BlindedPath, node_signer: &NS, node_id_lookup: &NL, secp_ctx: &Secp256k1<T>
  89 ) -> Result<(), ()>
  90 where
  91         NS::Target: NodeSigner,
  92         NL::Target: NodeIdLookUp,
  93         T: secp256k1::Signing + secp256k1::Verification,
  94 {
  95         let control_tlvs_ss = node_signer.ecdh(Recipient::Node, &path.blinding_point, None)?;
  96         let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
  97         let encrypted_control_tlvs = path.blinded_hops.remove(0).encrypted_payload;
  98         let mut s = Cursor::new(&encrypted_control_tlvs);
  99         let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
 100         match ChaChaPolyReadAdapter::read(&mut reader, rho) {
 101                 Ok(ChaChaPolyReadAdapter {
 102                         readable: ControlTlvs::Forward(ForwardTlvs { next_hop, next_blinding_override })
 103                 }) => {
 104                         let next_node_id = match next_hop {
 105                                 NextHop::NodeId(pubkey) => pubkey,
 106                                 NextHop::ShortChannelId(scid) => match node_id_lookup.next_node_id(scid) {
 107                                         Some(pubkey) => pubkey,
 108                                         None => return Err(()),
 109                                 },
 110                         };
 111                         let mut new_blinding_point = match next_blinding_override {
 112                                 Some(blinding_point) => blinding_point,
 113                                 None => {
 114                                         onion_utils::next_hop_pubkey(secp_ctx, path.blinding_point,
 115                                                 control_tlvs_ss.as_ref()).map_err(|_| ())?
 116                                 }
 117                         };
 118                         mem::swap(&mut path.blinding_point, &mut new_blinding_point);
 119                         path.introduction_node = IntroductionNode::NodeId(next_node_id);
 120                         Ok(())
 121                 },
 122                 _ => Err(())
 123         }
 124 }