+
+ // Advance the blinded route by one hop, so make the second hop into the new introduction node.
+ pub(super) fn advance_by_one<K: Deref, T: secp256k1::Signing + secp256k1::Verification>
+ (&mut self, keys_manager: &K, secp_ctx: &Secp256k1<T>) -> Result<(), ()>
+ where K::Target: KeysInterface
+ {
+ let control_tlvs_ss = keys_manager.ecdh(Recipient::Node, &self.blinding_point, None)?;
+ let rho = onion_utils::gen_rho_from_shared_secret(&control_tlvs_ss.secret_bytes());
+ let encrypted_control_tlvs = self.blinded_hops.remove(0).encrypted_payload;
+ let mut s = Cursor::new(&encrypted_control_tlvs);
+ let mut reader = FixedLengthReader::new(&mut s, encrypted_control_tlvs.len() as u64);
+ match ChaChaPolyReadAdapter::read(&mut reader, rho) {
+ Ok(ChaChaPolyReadAdapter { readable: ControlTlvs::Forward(ForwardTlvs {
+ mut next_node_id, next_blinding_override,
+ })}) => {
+ let mut new_blinding_point = match next_blinding_override {
+ Some(blinding_point) => blinding_point,
+ None => {
+ let blinding_factor = {
+ let mut sha = Sha256::engine();
+ sha.input(&self.blinding_point.serialize()[..]);
+ sha.input(control_tlvs_ss.as_ref());
+ Sha256::from_engine(sha).into_inner()
+ };
+ self.blinding_point.mul_tweak(secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap())
+ .map_err(|_| ())?
+ }
+ };
+ mem::swap(&mut self.blinding_point, &mut new_blinding_point);
+ mem::swap(&mut self.introduction_node_id, &mut next_node_id);
+ Ok(())
+ },
+ _ => Err(())
+ }
+ }