X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;ds=sidebyside;f=lightning%2Fsrc%2Fblinded_path%2Futils.rs;fp=lightning%2Fsrc%2Fblinded_path%2Futils.rs;h=1993ad932267db8f2d2c8a98f999f2726530b833;hb=607727fae793e86f23249afddb0c10018312607f;hp=0000000000000000000000000000000000000000;hpb=bc544414247af4ceeaa53c0b3f204d7fad85d4b8;p=rust-lightning

diff --git a/lightning/src/blinded_path/utils.rs b/lightning/src/blinded_path/utils.rs
new file mode 100644
index 00000000..1993ad93
--- /dev/null
+++ b/lightning/src/blinded_path/utils.rs
@@ -0,0 +1,98 @@
+// This file is Copyright its original authors, visible in version control
+// history.
+//
+// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
+// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
+// You may not use this file except in accordance with one or both of these
+// licenses.
+
+//! Onion message utility methods live here.
+
+use bitcoin::hashes::{Hash, HashEngine};
+use bitcoin::hashes::hmac::{Hmac, HmacEngine};
+use bitcoin::hashes::sha256::Hash as Sha256;
+use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey, Scalar};
+use bitcoin::secp256k1::ecdh::SharedSecret;
+
+use super::BlindedPath;
+use crate::ln::onion_utils;
+use crate::onion_message::Destination;
+
+use crate::prelude::*;
+
+// TODO: DRY with onion_utils::construct_onion_keys_callback
+#[inline]
+pub(crate) fn construct_keys_callback<T: secp256k1::Signing + secp256k1::Verification,
+	FType: FnMut(PublicKey, SharedSecret, PublicKey, [u8; 32], Option<PublicKey>, Option<Vec<u8>>)>(
+	secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], destination: Option<Destination>,
+	session_priv: &SecretKey, mut callback: FType
+) -> Result<(), secp256k1::Error> {
+	let mut msg_blinding_point_priv = session_priv.clone();
+	let mut msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
+	let mut onion_packet_pubkey_priv = msg_blinding_point_priv.clone();
+	let mut onion_packet_pubkey = msg_blinding_point.clone();
+
+	macro_rules! build_keys {
+		($pk: expr, $blinded: expr, $encrypted_payload: expr) => {{
+			let encrypted_data_ss = SharedSecret::new(&$pk, &msg_blinding_point_priv);
+
+			let blinded_hop_pk = if $blinded { $pk } else {
+				let hop_pk_blinding_factor = {
+					let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
+					hmac.input(encrypted_data_ss.as_ref());
+					Hmac::from_engine(hmac).into_inner()
+				};
+				$pk.mul_tweak(secp_ctx, &Scalar::from_be_bytes(hop_pk_blinding_factor).unwrap())?
+			};
+			let onion_packet_ss = SharedSecret::new(&blinded_hop_pk, &onion_packet_pubkey_priv);
+
+			let rho = onion_utils::gen_rho_from_shared_secret(encrypted_data_ss.as_ref());
+			let unblinded_pk_opt = if $blinded { None } else { Some($pk) };
+			callback(blinded_hop_pk, onion_packet_ss, onion_packet_pubkey, rho, unblinded_pk_opt, $encrypted_payload);
+			(encrypted_data_ss, onion_packet_ss)
+		}}
+	}
+
+	macro_rules! build_keys_in_loop {
+		($pk: expr, $blinded: expr, $encrypted_payload: expr) => {
+			let (encrypted_data_ss, onion_packet_ss) = build_keys!($pk, $blinded, $encrypted_payload);
+
+			let msg_blinding_point_blinding_factor = {
+				let mut sha = Sha256::engine();
+				sha.input(&msg_blinding_point.serialize()[..]);
+				sha.input(encrypted_data_ss.as_ref());
+				Sha256::from_engine(sha).into_inner()
+			};
+
+			msg_blinding_point_priv = msg_blinding_point_priv.mul_tweak(&Scalar::from_be_bytes(msg_blinding_point_blinding_factor).unwrap())?;
+			msg_blinding_point = PublicKey::from_secret_key(secp_ctx, &msg_blinding_point_priv);
+
+			let onion_packet_pubkey_blinding_factor = {
+				let mut sha = Sha256::engine();
+				sha.input(&onion_packet_pubkey.serialize()[..]);
+				sha.input(onion_packet_ss.as_ref());
+				Sha256::from_engine(sha).into_inner()
+			};
+			onion_packet_pubkey_priv = onion_packet_pubkey_priv.mul_tweak(&Scalar::from_be_bytes(onion_packet_pubkey_blinding_factor).unwrap())?;
+			onion_packet_pubkey = PublicKey::from_secret_key(secp_ctx, &onion_packet_pubkey_priv);
+		};
+	}
+
+	for pk in unblinded_path {
+		build_keys_in_loop!(*pk, false, None);
+	}
+	if let Some(dest) = destination {
+		match dest {
+			Destination::Node(pk) => {
+				build_keys!(pk, false, None);
+			},
+			Destination::BlindedPath(BlindedPath { blinded_hops, .. }) => {
+				for hop in blinded_hops {
+					build_keys_in_loop!(hop.blinded_node_id, true, Some(hop.encrypted_payload));
+				}
+			},
+		}
+	}
+	Ok(())
+}