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

   1 //! Data structures and methods for constructing [`BlindedPath`]s to send a message over.
   2 //!
   3 //! [`BlindedPath`]: crate::blinded_path::BlindedPath
   4
   5 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
   6
   7 #[allow(unused_imports)]
   8 use crate::prelude::*;
   9
  10 use crate::blinded_path::{BlindedHop, BlindedPath, IntroductionNode, NextMessageHop, NodeIdLookUp};
  11 use crate::blinded_path::utils;
  12 use crate::io;
  13 use crate::io::Cursor;
  14 use crate::ln::onion_utils;
  15 use crate::onion_message::packet::ControlTlvs;
  16 use crate::sign::{NodeSigner, Recipient};
  17 use crate::crypto::streams::ChaChaPolyReadAdapter;
  18 use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Writeable, Writer};
  19
  20 use core::mem;
  21 use core::ops::Deref;
  22
  23 /// An intermediate node, and possibly a short channel id leading to the next node.
  24 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
  25 pub struct ForwardNode {
  26         /// This node's pubkey.
  27         pub node_id: PublicKey,
  28         /// The channel between `node_id` and the next hop. If set, the constructed [`BlindedHop`]'s
  29         /// `encrypted_payload` will use this instead of the next [`ForwardNode::node_id`] for a more
  30         /// compact representation.
  31         pub short_channel_id: Option<u64>,
  32 }
  33
  34 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
  35 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
  36 pub(crate) struct ForwardTlvs {
  37         /// The next hop in the onion message's path.
  38         pub(crate) next_hop: NextMessageHop,
  39         /// Senders to a blinded path use this value to concatenate the route they find to the
  40         /// introduction node with the blinded path.
  41         pub(crate) next_blinding_override: Option<PublicKey>,
  42 }
  43
  44 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
  45 pub(crate) struct ReceiveTlvs {
  46         /// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
  47         /// sending to. This is useful for receivers to check that said blinded path is being used in
  48         /// the right context.
  49         pub(crate) path_id: Option<[u8; 32]>,
  50 }
  51
  52 impl Writeable for ForwardTlvs {
  53         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  54                 let (next_node_id, short_channel_id) = match self.next_hop {
  55                         NextMessageHop::NodeId(pubkey) => (Some(pubkey), None),
  56                         NextMessageHop::ShortChannelId(scid) => (None, Some(scid)),
  57                 };
  58                 // TODO: write padding
  59                 encode_tlv_stream!(writer, {
  60                         (2, short_channel_id, option),
  61                         (4, next_node_id, option),
  62                         (8, self.next_blinding_override, option)
  63                 });
  64                 Ok(())
  65         }
  66 }
  67
  68 impl Writeable for ReceiveTlvs {
  69         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
  70                 // TODO: write padding
  71                 encode_tlv_stream!(writer, {
  72                         (6, self.path_id, option),
  73                 });
  74                 Ok(())
  75         }
  76 }
  77
  78 /// Construct blinded onion message hops for the given `intermediate_nodes` and `recipient_node_id`.
  79 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
  80         secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode], recipient_node_id: PublicKey,
  81         session_priv: &SecretKey
  82 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
  83         let pks = intermediate_nodes.iter().map(|node| &node.node_id)
  84                 .chain(core::iter::once(&recipient_node_id));
  85         let tlvs = pks.clone()
  86                 .skip(1) // The first node's TLVs contains the next node's pubkey
  87                 .zip(intermediate_nodes.iter().map(|node| node.short_channel_id))
  88                 .map(|(pubkey, scid)| match scid {
  89                         Some(scid) => NextMessageHop::ShortChannelId(scid),
  90                         None => NextMessageHop::NodeId(*pubkey),
  91                 })
  92                 .map(|next_hop| ControlTlvs::Forward(ForwardTlvs { next_hop, next_blinding_override: None }))
  93                 .chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs { path_id: None })));
  94
  95         utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
  96 }
  97
  98 // Advance the blinded onion message path by one hop, so make the second hop into the new
  99 // introduction node.
 100 pub(crate) fn advance_path_by_one<NS: Deref, NL: Deref, T>(
 101         path: &mut BlindedPath, node_signer: &NS, node_id_lookup: &NL, secp_ctx: &Secp256k1<T>
 102 ) -> Result<(), ()>
 103 where
 104         NS::Target: NodeSigner,
 105         NL::Target: NodeIdLookUp,
 106         T: secp256k1::Signing + secp256k1::Verification,
 107 {
 108         let control_tlvs_ss = node_signer.ecdh(Recipient::Node, &path.blinding_point, None)?;
 109         let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
 110         let encrypted_control_tlvs = path.blinded_hops.remove(0).encrypted_payload;
 111         let mut s = Cursor::new(&encrypted_control_tlvs);
 112         let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
 113         match ChaChaPolyReadAdapter::read(&mut reader, rho) {
 114                 Ok(ChaChaPolyReadAdapter {
 115                         readable: ControlTlvs::Forward(ForwardTlvs { next_hop, next_blinding_override })
 116                 }) => {
 117                         let next_node_id = match next_hop {
 118                                 NextMessageHop::NodeId(pubkey) => pubkey,
 119                                 NextMessageHop::ShortChannelId(scid) => match node_id_lookup.next_node_id(scid) {
 120                                         Some(pubkey) => pubkey,
 121                                         None => return Err(()),
 122                                 },
 123                         };
 124                         let mut new_blinding_point = match next_blinding_override {
 125                                 Some(blinding_point) => blinding_point,
 126                                 None => {
 127                                         onion_utils::next_hop_pubkey(secp_ctx, path.blinding_point,
 128                                                 control_tlvs_ss.as_ref()).map_err(|_| ())?
 129                                 }
 130                         };
 131                         mem::swap(&mut path.blinding_point, &mut new_blinding_point);
 132                         path.introduction_node = IntroductionNode::NodeId(next_node_id);
 133                         Ok(())
 134                 },
 135                 _ => Err(())
 136         }
 137 }