1 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
2 use crate::blinded_path::BlindedHop;
3 use crate::blinded_path::utils;
6 use crate::util::ser::{Writeable, Writer};
8 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
9 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
10 pub(crate) struct ForwardTlvs {
11 /// The node id of the next hop in the onion message's path.
12 pub(crate) next_node_id: PublicKey,
13 /// Senders to a blinded path use this value to concatenate the route they find to the
14 /// introduction node with the blinded path.
15 pub(crate) next_blinding_override: Option<PublicKey>,
18 /// Similar to [`ForwardTlvs`], but these TLVs are for the final node.
19 pub(crate) struct ReceiveTlvs {
20 /// If `path_id` is `Some`, it is used to identify the blinded path that this onion message is
21 /// sending to. This is useful for receivers to check that said blinded path is being used in
22 /// the right context.
23 pub(crate) path_id: Option<[u8; 32]>,
26 impl Writeable for ForwardTlvs {
27 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
28 // TODO: write padding
29 encode_tlv_stream!(writer, {
30 (4, self.next_node_id, required),
31 (8, self.next_blinding_override, option)
37 impl Writeable for ReceiveTlvs {
38 fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
39 // TODO: write padding
40 encode_tlv_stream!(writer, {
41 (6, self.path_id, option),
47 /// Construct blinded onion message hops for the given `unblinded_path`.
48 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
49 secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
50 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
51 let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
53 let mut prev_ss_and_blinded_node_id = None;
54 utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
55 if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
56 if let Some(pk) = unblinded_pk {
57 let payload = ForwardTlvs {
59 next_blinding_override: None,
61 blinded_hops.push(BlindedHop {
62 blinded_node_id: prev_blinded_node_id,
63 encrypted_payload: utils::encrypt_payload(payload, prev_ss),
65 } else { debug_assert!(false); }
67 prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
70 if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
71 let final_payload = ReceiveTlvs { path_id: None };
72 blinded_hops.push(BlindedHop {
73 blinded_node_id: final_blinded_node_id,
74 encrypted_payload: utils::encrypt_payload(final_payload, final_ss),
76 } else { debug_assert!(false) }