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use bitcoin::hashes::{Hash, HashEngine};
use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1, SecretKey};
use crate::chain::keysinterface::{EntropySource, NodeSigner, Recipient};
use super::packet::ControlTlvs;
use super::utils;
use crate::ln::msgs::DecodeError;
use crate::ln::onion_utils;
use crate::util::chacha20poly1305rfc::{ChaChaPolyReadAdapter, ChaChaPolyWriteAdapter};
use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Readable, VecWriter, Writeable, Writer};
use core::mem;
use core::ops::Deref;
use crate::io::{self, Cursor};
use crate::prelude::*;
#[derive(Clone, Debug, PartialEq)]
pub struct BlindedPath {
pub(crate) introduction_node_id: PublicKey,
pub(crate) blinding_point: PublicKey,
pub(crate) blinded_hops: Vec<BlindedHop>,
}
#[derive(Clone, Debug, PartialEq)]
pub struct BlindedHop {
pub(crate) blinded_node_id: PublicKey,
pub(crate) encrypted_payload: Vec<u8>,
}
impl BlindedPath {
pub fn new<ES: EntropySource, T: secp256k1::Signing + secp256k1::Verification>
(node_pks: &[PublicKey], entropy_source: &ES, secp_ctx: &Secp256k1<T>) -> Result<Self, ()>
{
if node_pks.len() < 2 { return Err(()) }
let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
let introduction_node_id = node_pks[0];
Ok(BlindedPath {
introduction_node_id,
blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
blinded_hops: blinded_hops(secp_ctx, node_pks, &blinding_secret).map_err(|_| ())?,
})
}
pub(super) fn advance_by_one<NS: Deref, T: secp256k1::Signing + secp256k1::Verification>
(&mut self, node_signer: &NS, secp_ctx: &Secp256k1<T>) -> Result<(), ()>
where NS::Target: NodeSigner
{
let control_tlvs_ss = node_signer.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(())
}
}
}
fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
) -> Result<Vec<BlindedHop>, secp256k1::Error> {
let mut blinded_hops = Vec::with_capacity(unblinded_path.len());
let mut prev_ss_and_blinded_node_id = None;
utils::construct_keys_callback(secp_ctx, unblinded_path, None, session_priv, |blinded_node_id, _, _, encrypted_payload_ss, unblinded_pk, _| {
if let Some((prev_ss, prev_blinded_node_id)) = prev_ss_and_blinded_node_id {
if let Some(pk) = unblinded_pk {
let payload = ForwardTlvs {
next_node_id: pk,
next_blinding_override: None,
};
blinded_hops.push(BlindedHop {
blinded_node_id: prev_blinded_node_id,
encrypted_payload: encrypt_payload(payload, prev_ss),
});
} else { debug_assert!(false); }
}
prev_ss_and_blinded_node_id = Some((encrypted_payload_ss, blinded_node_id));
})?;
if let Some((final_ss, final_blinded_node_id)) = prev_ss_and_blinded_node_id {
let final_payload = ReceiveTlvs { path_id: None };
blinded_hops.push(BlindedHop {
blinded_node_id: final_blinded_node_id,
encrypted_payload: encrypt_payload(final_payload, final_ss),
});
} else { debug_assert!(false) }
Ok(blinded_hops)
}
fn encrypt_payload<P: Writeable>(payload: P, encrypted_tlvs_ss: [u8; 32]) -> Vec<u8> {
let mut writer = VecWriter(Vec::new());
let write_adapter = ChaChaPolyWriteAdapter::new(encrypted_tlvs_ss, &payload);
write_adapter.write(&mut writer).expect("In-memory writes cannot fail");
writer.0
}
impl Writeable for BlindedPath {
fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
self.introduction_node_id.write(w)?;
self.blinding_point.write(w)?;
(self.blinded_hops.len() as u8).write(w)?;
for hop in &self.blinded_hops {
hop.write(w)?;
}
Ok(())
}
}
impl Readable for BlindedPath {
fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
let introduction_node_id = Readable::read(r)?;
let blinding_point = Readable::read(r)?;
let num_hops: u8 = Readable::read(r)?;
if num_hops == 0 { return Err(DecodeError::InvalidValue) }
let mut blinded_hops: Vec<BlindedHop> = Vec::with_capacity(num_hops.into());
for _ in 0..num_hops {
blinded_hops.push(Readable::read(r)?);
}
Ok(BlindedPath {
introduction_node_id,
blinding_point,
blinded_hops,
})
}
}
impl_writeable!(BlindedHop, {
blinded_node_id,
encrypted_payload
});
pub(crate) struct ForwardTlvs {
pub(super) next_node_id: PublicKey,
pub(super) next_blinding_override: Option<PublicKey>,
}
pub(crate) struct ReceiveTlvs {
pub(super) path_id: Option<[u8; 32]>,
}
impl Writeable for ForwardTlvs {
fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
encode_tlv_stream!(writer, {
(4, self.next_node_id, required),
(8, self.next_blinding_override, option)
});
Ok(())
}
}
impl Writeable for ReceiveTlvs {
fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
encode_tlv_stream!(writer, {
(6, self.path_id, option),
});
Ok(())
}
}