lightning/ln/

onion_utils.rs

// 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.

use crate::blinded_path::BlindedHop;
use crate::crypto::chacha20::ChaCha20;
use crate::crypto::streams::ChaChaReader;
use crate::ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
use crate::ln::channelmanager::{HTLCSource, RecipientOnionFields};
use crate::ln::msgs;
use crate::offers::invoice_request::InvoiceRequest;
use crate::routing::gossip::NetworkUpdate;
use crate::routing::router::{Path, RouteHop, RouteParameters};
use crate::sign::NodeSigner;
use crate::types::features::{ChannelFeatures, NodeFeatures};
use crate::types::payment::{PaymentHash, PaymentPreimage};
use crate::util::errors::{self, APIError};
use crate::util::logger::Logger;
use crate::util::ser::{LengthCalculatingWriter, Readable, ReadableArgs, Writeable, Writer};

use bitcoin::hashes::cmp::fixed_time_eq;
use bitcoin::hashes::hmac::{Hmac, HmacEngine};
use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hashes::{Hash, HashEngine};

use bitcoin::secp256k1;
use bitcoin::secp256k1::ecdh::SharedSecret;
use bitcoin::secp256k1::{PublicKey, Scalar, Secp256k1, SecretKey};

use crate::io::{Cursor, Read};
use core::ops::Deref;

#[allow(unused_imports)]
use crate::prelude::*;

pub(crate) struct OnionKeys {
	#[cfg(test)]
	pub(crate) shared_secret: SharedSecret,
	#[cfg(test)]
	pub(crate) blinding_factor: [u8; 32],
	pub(crate) ephemeral_pubkey: PublicKey,
	pub(crate) rho: [u8; 32],
	pub(crate) mu: [u8; 32],
}

#[inline]
pub(crate) fn gen_rho_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
	assert_eq!(shared_secret.len(), 32);
	let mut hmac = HmacEngine::<Sha256>::new(&[0x72, 0x68, 0x6f]); // rho
	hmac.input(&shared_secret);
	Hmac::from_engine(hmac).to_byte_array()
}

#[inline]
pub(crate) fn gen_rho_mu_from_shared_secret(shared_secret: &[u8]) -> ([u8; 32], [u8; 32]) {
	assert_eq!(shared_secret.len(), 32);
	let mut engine_rho = HmacEngine::<Sha256>::new(b"rho");
	engine_rho.input(&shared_secret);
	let hmac_rho = Hmac::from_engine(engine_rho).to_byte_array();

	let mut engine_mu = HmacEngine::<Sha256>::new(b"mu");
	engine_mu.input(&shared_secret);
	let hmac_mu = Hmac::from_engine(engine_mu).to_byte_array();

	(hmac_rho, hmac_mu)
}

#[inline]
pub(super) fn gen_um_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
	assert_eq!(shared_secret.len(), 32);
	let mut hmac = HmacEngine::<Sha256>::new(&[0x75, 0x6d]); // um
	hmac.input(&shared_secret);
	Hmac::from_engine(hmac).to_byte_array()
}

#[inline]
pub(super) fn gen_ammag_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
	assert_eq!(shared_secret.len(), 32);
	let mut hmac = HmacEngine::<Sha256>::new(&[0x61, 0x6d, 0x6d, 0x61, 0x67]); // ammag
	hmac.input(&shared_secret);
	Hmac::from_engine(hmac).to_byte_array()
}

#[cfg(test)]
#[inline]
pub(super) fn gen_pad_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
	assert_eq!(shared_secret.len(), 32);
	let mut hmac = HmacEngine::<Sha256>::new(&[0x70, 0x61, 0x64]); // pad
	hmac.input(&shared_secret);
	Hmac::from_engine(hmac).to_byte_array()
}

/// Calculates a pubkey for the next hop, such as the next hop's packet pubkey or blinding point.
pub(crate) fn next_hop_pubkey<T: secp256k1::Verification>(
	secp_ctx: &Secp256k1<T>, curr_pubkey: PublicKey, shared_secret: &[u8],
) -> Result<PublicKey, secp256k1::Error> {
	let blinding_factor = {
		let mut sha = Sha256::engine();
		sha.input(&curr_pubkey.serialize()[..]);
		sha.input(shared_secret);
		Sha256::from_engine(sha).to_byte_array()
	};

	curr_pubkey.mul_tweak(secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap())
}

// can only fail if an intermediary hop has an invalid public key or session_priv is invalid
#[inline]
pub(super) fn construct_onion_keys_callback<T, FType>(
	secp_ctx: &Secp256k1<T>, path: &Path, session_priv: &SecretKey, mut callback: FType,
) -> Result<(), secp256k1::Error>
where
	T: secp256k1::Signing,
	FType: FnMut(SharedSecret, [u8; 32], PublicKey, Option<&RouteHop>, usize),
{
	let mut blinded_priv = session_priv.clone();
	let mut blinded_pub = PublicKey::from_secret_key(secp_ctx, &blinded_priv);

	let unblinded_hops_iter = path.hops.iter().map(|h| (&h.pubkey, Some(h)));
	let blinded_pks_iter = path
		.blinded_tail
		.as_ref()
		.map(|t| t.hops.iter())
		.unwrap_or([].iter())
		.skip(1) // Skip the intro node because it's included in the unblinded hops
		.map(|h| (&h.blinded_node_id, None));
	for (idx, (pubkey, route_hop_opt)) in unblinded_hops_iter.chain(blinded_pks_iter).enumerate() {
		let shared_secret = SharedSecret::new(pubkey, &blinded_priv);

		let mut sha = Sha256::engine();
		sha.input(&blinded_pub.serialize()[..]);
		sha.input(shared_secret.as_ref());
		let blinding_factor = Sha256::from_engine(sha).to_byte_array();

		let ephemeral_pubkey = blinded_pub;

		blinded_priv = blinded_priv.mul_tweak(&Scalar::from_be_bytes(blinding_factor).unwrap())?;
		blinded_pub = PublicKey::from_secret_key(secp_ctx, &blinded_priv);

		callback(shared_secret, blinding_factor, ephemeral_pubkey, route_hop_opt, idx);
	}

	Ok(())
}

// can only fail if an intermediary hop has an invalid public key or session_priv is invalid
pub(super) fn construct_onion_keys<T: secp256k1::Signing>(
	secp_ctx: &Secp256k1<T>, path: &Path, session_priv: &SecretKey,
) -> Result<Vec<OnionKeys>, secp256k1::Error> {
	let mut res = Vec::with_capacity(path.hops.len());

	construct_onion_keys_callback(
		secp_ctx,
		&path,
		session_priv,
		|shared_secret, _blinding_factor, ephemeral_pubkey, _, _| {
			let (rho, mu) = gen_rho_mu_from_shared_secret(shared_secret.as_ref());

			res.push(OnionKeys {
				#[cfg(test)]
				shared_secret,
				#[cfg(test)]
				blinding_factor: _blinding_factor,
				ephemeral_pubkey,
				rho,
				mu,
			});
		},
	)?;

	Ok(res)
}

/// returns the hop data, as well as the first-hop value_msat and CLTV value we should send.
pub(super) fn build_onion_payloads<'a>(
	path: &'a Path, total_msat: u64, recipient_onion: &'a RecipientOnionFields,
	starting_htlc_offset: u32, keysend_preimage: &Option<PaymentPreimage>,
	invoice_request: Option<&'a InvoiceRequest>,
) -> Result<(Vec<msgs::OutboundOnionPayload<'a>>, u64, u32), APIError> {
	let mut res: Vec<msgs::OutboundOnionPayload> = Vec::with_capacity(
		path.hops.len() + path.blinded_tail.as_ref().map_or(0, |t| t.hops.len()),
	);
	let blinded_tail_with_hop_iter = path.blinded_tail.as_ref().map(|bt| BlindedTailHopIter {
		hops: bt.hops.iter(),
		blinding_point: bt.blinding_point,
		final_value_msat: bt.final_value_msat,
		excess_final_cltv_expiry_delta: bt.excess_final_cltv_expiry_delta,
	});

	let (value_msat, cltv) = build_onion_payloads_callback(
		path.hops.iter(),
		blinded_tail_with_hop_iter,
		total_msat,
		recipient_onion,
		starting_htlc_offset,
		keysend_preimage,
		invoice_request,
		|action, payload| match action {
			PayloadCallbackAction::PushBack => res.push(payload),
			PayloadCallbackAction::PushFront => res.insert(0, payload),
		},
	)?;
	Ok((res, value_msat, cltv))
}

struct BlindedTailHopIter<'a, I: Iterator<Item = &'a BlindedHop>> {
	hops: I,
	blinding_point: PublicKey,
	final_value_msat: u64,
	excess_final_cltv_expiry_delta: u32,
}
enum PayloadCallbackAction {
	PushBack,
	PushFront,
}
fn build_onion_payloads_callback<'a, H, B, F>(
	hops: H, mut blinded_tail: Option<BlindedTailHopIter<'a, B>>, total_msat: u64,
	recipient_onion: &'a RecipientOnionFields, starting_htlc_offset: u32,
	keysend_preimage: &Option<PaymentPreimage>, invoice_request: Option<&'a InvoiceRequest>,
	mut callback: F,
) -> Result<(u64, u32), APIError>
where
	H: DoubleEndedIterator<Item = &'a RouteHop>,
	B: ExactSizeIterator<Item = &'a BlindedHop>,
	F: FnMut(PayloadCallbackAction, msgs::OutboundOnionPayload<'a>),
{
	let mut cur_value_msat = 0u64;
	let mut cur_cltv = starting_htlc_offset;
	let mut last_short_channel_id = 0;

	for (idx, hop) in hops.rev().enumerate() {
		// First hop gets special values so that it can check, on receipt, that everything is
		// exactly as it should be (and the next hop isn't trying to probe to find out if we're
		// the intended recipient).
		let value_msat = if cur_value_msat == 0 { hop.fee_msat } else { cur_value_msat };
		let cltv = if cur_cltv == starting_htlc_offset {
			hop.cltv_expiry_delta.saturating_add(starting_htlc_offset)
		} else {
			cur_cltv
		};
		if idx == 0 {
			if let Some(BlindedTailHopIter {
				blinding_point,
				hops,
				final_value_msat,
				excess_final_cltv_expiry_delta,
				..
			}) = blinded_tail.take()
			{
				let mut blinding_point = Some(blinding_point);
				let hops_len = hops.len();
				for (i, blinded_hop) in hops.enumerate() {
					if i == hops_len - 1 {
						cur_value_msat += final_value_msat;
						callback(
							PayloadCallbackAction::PushBack,
							msgs::OutboundOnionPayload::BlindedReceive {
								sender_intended_htlc_amt_msat: final_value_msat,
								total_msat,
								cltv_expiry_height: cur_cltv + excess_final_cltv_expiry_delta,
								encrypted_tlvs: &blinded_hop.encrypted_payload,
								intro_node_blinding_point: blinding_point.take(),
								keysend_preimage: *keysend_preimage,
								invoice_request,
								custom_tlvs: &recipient_onion.custom_tlvs,
							},
						);
					} else {
						callback(
							PayloadCallbackAction::PushBack,
							msgs::OutboundOnionPayload::BlindedForward {
								encrypted_tlvs: &blinded_hop.encrypted_payload,
								intro_node_blinding_point: blinding_point.take(),
							},
						);
					}
				}
			} else {
				callback(
					PayloadCallbackAction::PushBack,
					msgs::OutboundOnionPayload::Receive {
						payment_data: recipient_onion.payment_secret.map(|payment_secret| {
							msgs::FinalOnionHopData { payment_secret, total_msat }
						}),
						payment_metadata: recipient_onion.payment_metadata.as_ref(),
						keysend_preimage: *keysend_preimage,
						custom_tlvs: &recipient_onion.custom_tlvs,
						sender_intended_htlc_amt_msat: value_msat,
						cltv_expiry_height: cltv,
					},
				);
			}
		} else {
			let payload = msgs::OutboundOnionPayload::Forward {
				short_channel_id: last_short_channel_id,
				amt_to_forward: value_msat,
				outgoing_cltv_value: cltv,
			};
			callback(PayloadCallbackAction::PushFront, payload);
		}
		cur_value_msat += hop.fee_msat;
		if cur_value_msat >= 21000000 * 100000000 * 1000 {
			return Err(APIError::InvalidRoute { err: "Channel fees overflowed?".to_owned() });
		}
		cur_cltv = cur_cltv.saturating_add(hop.cltv_expiry_delta as u32);
		if cur_cltv >= 500000000 {
			return Err(APIError::InvalidRoute { err: "Channel CLTV overflowed?".to_owned() });
		}
		last_short_channel_id = hop.short_channel_id;
	}
	Ok((cur_value_msat, cur_cltv))
}

pub(crate) const MIN_FINAL_VALUE_ESTIMATE_WITH_OVERPAY: u64 = 100_000_000;

pub(crate) fn set_max_path_length(
	route_params: &mut RouteParameters, recipient_onion: &RecipientOnionFields,
	keysend_preimage: Option<PaymentPreimage>, invoice_request: Option<&InvoiceRequest>,
	best_block_height: u32,
) -> Result<(), ()> {
	const PAYLOAD_HMAC_LEN: usize = 32;
	let unblinded_intermed_payload_len = msgs::OutboundOnionPayload::Forward {
		short_channel_id: 42,
		amt_to_forward: TOTAL_BITCOIN_SUPPLY_SATOSHIS,
		outgoing_cltv_value: route_params.payment_params.max_total_cltv_expiry_delta,
	}
	.serialized_length()
	.saturating_add(PAYLOAD_HMAC_LEN);

	const OVERPAY_ESTIMATE_MULTIPLER: u64 = 3;
	let final_value_msat_with_overpay_buffer = route_params
		.final_value_msat
		.saturating_mul(OVERPAY_ESTIMATE_MULTIPLER)
		.clamp(MIN_FINAL_VALUE_ESTIMATE_WITH_OVERPAY, 0x1000_0000);

	let blinded_tail_opt = route_params
		.payment_params
		.payee
		.blinded_route_hints()
		.iter()
		.max_by_key(|path| path.inner_blinded_path().serialized_length())
		.map(|largest_path| BlindedTailHopIter {
			hops: largest_path.blinded_hops().iter(),
			blinding_point: largest_path.blinding_point(),
			final_value_msat: final_value_msat_with_overpay_buffer,
			excess_final_cltv_expiry_delta: 0,
		});

	let cltv_expiry_delta =
		core::cmp::min(route_params.payment_params.max_total_cltv_expiry_delta, 0x1000_0000);
	let unblinded_route_hop = RouteHop {
		pubkey: PublicKey::from_slice(&[2; 33]).unwrap(),
		node_features: NodeFeatures::empty(),
		short_channel_id: 42,
		channel_features: ChannelFeatures::empty(),
		fee_msat: final_value_msat_with_overpay_buffer,
		cltv_expiry_delta,
		maybe_announced_channel: false,
	};
	let mut num_reserved_bytes: usize = 0;
	let build_payloads_res = build_onion_payloads_callback(
		core::iter::once(&unblinded_route_hop),
		blinded_tail_opt,
		final_value_msat_with_overpay_buffer,
		&recipient_onion,
		best_block_height,
		&keysend_preimage,
		invoice_request,
		|_, payload| {
			num_reserved_bytes = num_reserved_bytes
				.saturating_add(payload.serialized_length())
				.saturating_add(PAYLOAD_HMAC_LEN);
		},
	);
	debug_assert!(build_payloads_res.is_ok());

	let max_path_length = 1300usize
		.checked_sub(num_reserved_bytes)
		.map(|p| p / unblinded_intermed_payload_len)
		.and_then(|l| u8::try_from(l.saturating_add(1)).ok())
		.ok_or(())?;

	route_params.payment_params.max_path_length =
		core::cmp::min(max_path_length, route_params.payment_params.max_path_length);
	Ok(())
}

/// Length of the onion data packet. Before TLV-based onions this was 20 65-byte hops, though now
/// the hops can be of variable length.
pub(crate) const ONION_DATA_LEN: usize = 20 * 65;

pub(super) const INVALID_ONION_BLINDING: u16 = 0x8000 | 0x4000 | 24;

#[inline]
fn shift_slice_right(arr: &mut [u8], amt: usize) {
	for i in (amt..arr.len()).rev() {
		arr[i] = arr[i - amt];
	}
	for i in 0..amt {
		arr[i] = 0;
	}
}

pub(super) fn construct_onion_packet(
	payloads: Vec<msgs::OutboundOnionPayload>, onion_keys: Vec<OnionKeys>, prng_seed: [u8; 32],
	associated_data: &PaymentHash,
) -> Result<msgs::OnionPacket, ()> {
	let mut packet_data = [0; ONION_DATA_LEN];

	let mut chacha = ChaCha20::new(&prng_seed, &[0; 8]);
	chacha.process(&[0; ONION_DATA_LEN], &mut packet_data);

	let packet = FixedSizeOnionPacket(packet_data);
	construct_onion_packet_with_init_noise::<_, _>(
		payloads,
		onion_keys,
		packet,
		Some(associated_data),
	)
}

#[allow(unused)]
pub(super) fn construct_trampoline_onion_packet(
	payloads: Vec<msgs::OutboundTrampolinePayload>, onion_keys: Vec<OnionKeys>,
	prng_seed: [u8; 32], associated_data: &PaymentHash, length: u16,
) -> Result<msgs::TrampolineOnionPacket, ()> {
	let mut packet_data = vec![0u8; length as usize];

	let mut chacha = ChaCha20::new(&prng_seed, &[0; 8]);
	chacha.process(&vec![0u8; length as usize], &mut packet_data);

	construct_onion_packet_with_init_noise::<_, _>(
		payloads,
		onion_keys,
		packet_data,
		Some(associated_data),
	)
}

#[cfg(test)]
/// Used in testing to write bogus `BogusOnionHopData` as well as `RawOnionHopData`, which is
/// otherwise not representable in `msgs::OnionHopData`.
pub(super) fn construct_onion_packet_with_writable_hopdata<HD: Writeable>(
	payloads: Vec<HD>, onion_keys: Vec<OnionKeys>, prng_seed: [u8; 32],
	associated_data: &PaymentHash,
) -> Result<msgs::OnionPacket, ()> {
	let mut packet_data = [0; ONION_DATA_LEN];

	let mut chacha = ChaCha20::new(&prng_seed, &[0; 8]);
	chacha.process(&[0; ONION_DATA_LEN], &mut packet_data);

	let packet = FixedSizeOnionPacket(packet_data);
	construct_onion_packet_with_init_noise::<_, _>(
		payloads,
		onion_keys,
		packet,
		Some(associated_data),
	)
}

/// Since onion message packets and onion payment packets have different lengths but are otherwise
/// identical, we use this trait to allow `construct_onion_packet_with_init_noise` to return either
/// type.
pub(crate) trait Packet {
	type Data: AsMut<[u8]>;
	fn new(pubkey: PublicKey, hop_data: Self::Data, hmac: [u8; 32]) -> Self;
}

// Needed for rustc versions older than 1.47 to avoid E0277: "arrays only have std trait
// implementations for lengths 0..=32".
pub(crate) struct FixedSizeOnionPacket(pub(crate) [u8; ONION_DATA_LEN]);

impl AsMut<[u8]> for FixedSizeOnionPacket {
	fn as_mut(&mut self) -> &mut [u8] {
		&mut self.0
	}
}

pub(crate) fn payloads_serialized_length<HD: Writeable>(payloads: &Vec<HD>) -> usize {
	payloads.iter().map(|p| p.serialized_length() + 32 /* HMAC */).sum()
}

pub(crate) fn construct_onion_message_packet<HD: Writeable, P: Packet<Data = Vec<u8>>>(
	payloads: Vec<HD>, onion_keys: Vec<OnionKeys>, prng_seed: [u8; 32], packet_data_len: usize,
) -> Result<P, ()> {
	let mut packet_data = vec![0; packet_data_len];

	let mut chacha = ChaCha20::new(&prng_seed, &[0; 8]);
	chacha.process_in_place(&mut packet_data);

	construct_onion_packet_with_init_noise::<_, _>(payloads, onion_keys, packet_data, None)
}

fn construct_onion_packet_with_init_noise<HD: Writeable, P: Packet>(
	mut payloads: Vec<HD>, onion_keys: Vec<OnionKeys>, mut packet_data: P::Data,
	associated_data: Option<&PaymentHash>,
) -> Result<P, ()> {
	let filler = {
		let packet_data = packet_data.as_mut();
		const ONION_HOP_DATA_LEN: usize = 65; // We may decrease this eventually after TLV is common
		let mut res = Vec::with_capacity(ONION_HOP_DATA_LEN * (payloads.len() - 1));

		let mut pos = 0;
		for (i, (payload, keys)) in payloads.iter().zip(onion_keys.iter()).enumerate() {
			let mut chacha = ChaCha20::new(&keys.rho, &[0u8; 8]);
			// TODO: Batch this.
			for _ in 0..(packet_data.len() - pos) {
				let mut dummy = [0; 1];
				chacha.process_in_place(&mut dummy); // We don't have a seek function :(
			}

			let mut payload_len = LengthCalculatingWriter(0);
			payload.write(&mut payload_len).expect("Failed to calculate length");
			pos += payload_len.0 + 32;
			if pos > packet_data.len() {
				return Err(());
			}

			if i == payloads.len() - 1 {
				break;
			}

			res.resize(pos, 0u8);
			chacha.process_in_place(&mut res);
		}
		res
	};

	let mut hmac_res = [0; 32];
	for (i, (payload, keys)) in payloads.iter_mut().zip(onion_keys.iter()).rev().enumerate() {
		let mut payload_len = LengthCalculatingWriter(0);
		payload.write(&mut payload_len).expect("Failed to calculate length");

		let packet_data = packet_data.as_mut();
		shift_slice_right(packet_data, payload_len.0 + 32);
		packet_data[0..payload_len.0].copy_from_slice(&payload.encode()[..]);
		packet_data[payload_len.0..(payload_len.0 + 32)].copy_from_slice(&hmac_res);

		let mut chacha = ChaCha20::new(&keys.rho, &[0u8; 8]);
		chacha.process_in_place(packet_data);

		if i == 0 {
			let stop_index = packet_data.len();
			let start_index = stop_index.checked_sub(filler.len()).ok_or(())?;
			packet_data[start_index..stop_index].copy_from_slice(&filler[..]);
		}

		let mut hmac = HmacEngine::<Sha256>::new(&keys.mu);
		hmac.input(packet_data);
		if let Some(associated_data) = associated_data {
			hmac.input(&associated_data.0[..]);
		}
		hmac_res = Hmac::from_engine(hmac).to_byte_array();
	}

	Ok(P::new(onion_keys.first().unwrap().ephemeral_pubkey, packet_data, hmac_res))
}

/// Encrypts a failure packet. raw_packet can either be a
/// msgs::DecodedOnionErrorPacket.encode() result or a msgs::OnionErrorPacket.data element.
pub(super) fn encrypt_failure_packet(
	shared_secret: &[u8], raw_packet: &[u8],
) -> msgs::OnionErrorPacket {
	let ammag = gen_ammag_from_shared_secret(&shared_secret);

	let mut packet_crypted = Vec::with_capacity(raw_packet.len());
	packet_crypted.resize(raw_packet.len(), 0);
	let mut chacha = ChaCha20::new(&ammag, &[0u8; 8]);
	chacha.process(&raw_packet, &mut packet_crypted[..]);
	msgs::OnionErrorPacket { data: packet_crypted }
}

pub(super) fn build_failure_packet(
	shared_secret: &[u8], failure_type: u16, failure_data: &[u8],
) -> msgs::DecodedOnionErrorPacket {
	assert_eq!(shared_secret.len(), 32);
	assert!(failure_data.len() <= 256 - 2);

	let um = gen_um_from_shared_secret(&shared_secret);

	let failuremsg = {
		let mut res = Vec::with_capacity(2 + failure_data.len());
		res.push(((failure_type >> 8) & 0xff) as u8);
		res.push(((failure_type >> 0) & 0xff) as u8);
		res.extend_from_slice(&failure_data[..]);
		res
	};
	let pad = {
		let mut res = Vec::with_capacity(256 - 2 - failure_data.len());
		res.resize(256 - 2 - failure_data.len(), 0);
		res
	};
	let mut packet = msgs::DecodedOnionErrorPacket { hmac: [0; 32], failuremsg, pad };

	let mut hmac = HmacEngine::<Sha256>::new(&um);
	hmac.input(&packet.encode()[32..]);
	packet.hmac = Hmac::from_engine(hmac).to_byte_array();

	packet
}

#[cfg(test)]
pub(super) fn build_first_hop_failure_packet(
	shared_secret: &[u8], failure_type: u16, failure_data: &[u8],
) -> msgs::OnionErrorPacket {
	let failure_packet = build_failure_packet(shared_secret, failure_type, failure_data);
	encrypt_failure_packet(shared_secret, &failure_packet.encode()[..])
}

pub(crate) struct DecodedOnionFailure {
	pub(crate) network_update: Option<NetworkUpdate>,
	pub(crate) short_channel_id: Option<u64>,
	pub(crate) payment_failed_permanently: bool,
	pub(crate) failed_within_blinded_path: bool,
	#[cfg(test)]
	pub(crate) onion_error_code: Option<u16>,
	#[cfg(test)]
	pub(crate) onion_error_data: Option<Vec<u8>>,
}

/// Note that we always decrypt `packet` in-place here even if the deserialization into
/// [`msgs::DecodedOnionErrorPacket`] ultimately fails.
fn decrypt_onion_error_packet(
	packet: &mut Vec<u8>, shared_secret: SharedSecret,
) -> Result<msgs::DecodedOnionErrorPacket, msgs::DecodeError> {
	let ammag = gen_ammag_from_shared_secret(shared_secret.as_ref());
	let mut chacha = ChaCha20::new(&ammag, &[0u8; 8]);
	chacha.process_in_place(packet);
	msgs::DecodedOnionErrorPacket::read(&mut Cursor::new(packet))
}

/// Process failure we got back from upstream on a payment we sent (implying htlc_source is an
/// OutboundRoute).
#[inline]
pub(super) fn process_onion_failure<T: secp256k1::Signing, L: Deref>(
	secp_ctx: &Secp256k1<T>, logger: &L, htlc_source: &HTLCSource, mut encrypted_packet: Vec<u8>,
) -> DecodedOnionFailure
where
	L::Target: Logger,
{
	let (path, session_priv, first_hop_htlc_msat) = match htlc_source {
		HTLCSource::OutboundRoute {
			ref path, ref session_priv, ref first_hop_htlc_msat, ..
		} => (path, session_priv, first_hop_htlc_msat),
		_ => {
			unreachable!()
		},
	};

	// Learnings from the HTLC failure to inform future payment retries and scoring.
	struct FailureLearnings {
		network_update: Option<NetworkUpdate>,
		short_channel_id: Option<u64>,
		payment_failed_permanently: bool,
		failed_within_blinded_path: bool,
	}
	let mut res: Option<FailureLearnings> = None;
	let mut htlc_msat = *first_hop_htlc_msat;
	let mut error_code_ret = None;
	let mut error_packet_ret = None;
	let mut is_from_final_node = false;

	const BADONION: u16 = 0x8000;
	const PERM: u16 = 0x4000;
	const NODE: u16 = 0x2000;
	const UPDATE: u16 = 0x1000;

	// Handle packed channel/node updates for passing back for the route handler
	let callback = |shared_secret, _, _, route_hop_opt: Option<&RouteHop>, route_hop_idx| {
		if res.is_some() {
			return;
		}

		let route_hop = match route_hop_opt {
			Some(hop) => hop,
			None => {
				// Got an error from within a blinded route.
				error_code_ret = Some(BADONION | PERM | 24); // invalid_onion_blinding
				error_packet_ret = Some(vec![0; 32]);
				res = Some(FailureLearnings {
					network_update: None,
					short_channel_id: None,
					payment_failed_permanently: false,
					failed_within_blinded_path: true,
				});
				return;
			},
		};

		// The failing hop includes either the inbound channel to the recipient or the outbound channel
		// from the current hop (i.e., the next hop's inbound channel).
		let num_blinded_hops = path.blinded_tail.as_ref().map_or(0, |bt| bt.hops.len());
		// For 1-hop blinded paths, the final `path.hops` entry is the recipient.
		is_from_final_node = route_hop_idx + 1 == path.hops.len() && num_blinded_hops <= 1;
		let failing_route_hop = if is_from_final_node {
			route_hop
		} else {
			match path.hops.get(route_hop_idx + 1) {
				Some(hop) => hop,
				None => {
					// The failing hop is within a multi-hop blinded path.
					#[cfg(not(test))]
					{
						error_code_ret = Some(BADONION | PERM | 24); // invalid_onion_blinding
						error_packet_ret = Some(vec![0; 32]);
					}
					#[cfg(test)]
					{
						// Actually parse the onion error data in tests so we can check that blinded hops fail
						// back correctly.
						let err_packet =
							decrypt_onion_error_packet(&mut encrypted_packet, shared_secret)
								.unwrap();
						error_code_ret = Some(u16::from_be_bytes(
							err_packet.failuremsg.get(0..2).unwrap().try_into().unwrap(),
						));
						error_packet_ret = Some(err_packet.failuremsg[2..].to_vec());
					}

					res = Some(FailureLearnings {
						network_update: None,
						short_channel_id: None,
						payment_failed_permanently: false,
						failed_within_blinded_path: true,
					});
					return;
				},
			}
		};

		let amt_to_forward = htlc_msat - route_hop.fee_msat;
		htlc_msat = amt_to_forward;

		let err_packet = match decrypt_onion_error_packet(&mut encrypted_packet, shared_secret) {
			Ok(p) => p,
			Err(_) => return,
		};
		let um = gen_um_from_shared_secret(shared_secret.as_ref());
		let mut hmac = HmacEngine::<Sha256>::new(&um);
		hmac.input(&err_packet.encode()[32..]);

		if !fixed_time_eq(&Hmac::from_engine(hmac).to_byte_array(), &err_packet.hmac) {
			return;
		}
		let error_code_slice = match err_packet.failuremsg.get(0..2) {
			Some(s) => s,
			None => {
				// Useless packet that we can't use but it passed HMAC, so it definitely came from the peer
				// in question
				let network_update = Some(NetworkUpdate::NodeFailure {
					node_id: route_hop.pubkey,
					is_permanent: true,
				});
				let short_channel_id = Some(route_hop.short_channel_id);
				res = Some(FailureLearnings {
					network_update,
					short_channel_id,
					payment_failed_permanently: is_from_final_node,
					failed_within_blinded_path: false,
				});
				return;
			},
		};

		let error_code = u16::from_be_bytes(error_code_slice.try_into().expect("len is 2"));
		error_code_ret = Some(error_code);
		error_packet_ret = Some(err_packet.failuremsg[2..].to_vec());

		let (debug_field, debug_field_size) = errors::get_onion_debug_field(error_code);

		// indicate that payment parameter has failed and no need to update Route object
		let payment_failed = match error_code & 0xff {
			15 | 16 | 17 | 18 | 19 | 23 => true,
			_ => false,
		} && is_from_final_node; // PERM bit observed below even if this error is from the intermediate nodes

		let mut network_update = None;
		let mut short_channel_id = None;

		if error_code & BADONION == BADONION {
			// If the error code has the BADONION bit set, always blame the channel from the node
			// "originating" the error to its next hop. The "originator" is ultimately actually claiming
			// that its counterparty is the one who is failing the HTLC.
			// If the "originator" here isn't lying we should really mark the next-hop node as failed
			// entirely, but we can't be confident in that, as it would allow any node to get us to
			// completely ban one of its counterparties. Instead, we simply remove the channel in
			// question.
			network_update = Some(NetworkUpdate::ChannelFailure {
				short_channel_id: failing_route_hop.short_channel_id,
				is_permanent: true,
			});
		} else if error_code & NODE == NODE {
			let is_permanent = error_code & PERM == PERM;
			network_update =
				Some(NetworkUpdate::NodeFailure { node_id: route_hop.pubkey, is_permanent });
			short_channel_id = Some(route_hop.short_channel_id);
		} else if error_code & PERM == PERM {
			if !payment_failed {
				network_update = Some(NetworkUpdate::ChannelFailure {
					short_channel_id: failing_route_hop.short_channel_id,
					is_permanent: true,
				});
				short_channel_id = Some(failing_route_hop.short_channel_id);
			}
		} else if error_code & UPDATE == UPDATE {
			if let Some(update_len_slice) =
				err_packet.failuremsg.get(debug_field_size + 2..debug_field_size + 4)
			{
				let update_len =
					u16::from_be_bytes(update_len_slice.try_into().expect("len is 2")) as usize;
				if err_packet
					.failuremsg
					.get(debug_field_size + 4..debug_field_size + 4 + update_len)
					.is_some()
				{
					network_update = Some(NetworkUpdate::ChannelFailure {
						short_channel_id: failing_route_hop.short_channel_id,
						is_permanent: false,
					});
					short_channel_id = Some(failing_route_hop.short_channel_id);
				}
			}
			if network_update.is_none() {
				// They provided an UPDATE which was obviously bogus, not worth
				// trying to relay through them anymore.
				network_update = Some(NetworkUpdate::NodeFailure {
					node_id: route_hop.pubkey,
					is_permanent: true,
				});
			}
			if short_channel_id.is_none() {
				short_channel_id = Some(route_hop.short_channel_id);
			}
		} else if payment_failed {
			// Only blame the hop when a value in the HTLC doesn't match the corresponding value in the
			// onion.
			short_channel_id = match error_code & 0xff {
				18 | 19 => Some(route_hop.short_channel_id),
				_ => None,
			};
		} else {
			// We can't understand their error messages and they failed to forward...they probably can't
			// understand our forwards so it's really not worth trying any further.
			network_update =
				Some(NetworkUpdate::NodeFailure { node_id: route_hop.pubkey, is_permanent: true });
			short_channel_id = Some(route_hop.short_channel_id);
		}

		res = Some(FailureLearnings {
			network_update,
			short_channel_id,
			payment_failed_permanently: error_code & PERM == PERM && is_from_final_node,
			failed_within_blinded_path: false,
		});

		let (description, title) = errors::get_onion_error_description(error_code);
		if debug_field_size > 0 && err_packet.failuremsg.len() >= 4 + debug_field_size {
			log_info!(
				logger,
				"Onion Error[from {}: {}({:#x}) {}({})] {}",
				route_hop.pubkey,
				title,
				error_code,
				debug_field,
				log_bytes!(&err_packet.failuremsg[4..4 + debug_field_size]),
				description
			);
		} else {
			log_info!(
				logger,
				"Onion Error[from {}: {}({:#x})] {}",
				route_hop.pubkey,
				title,
				error_code,
				description
			);
		}
	};

	construct_onion_keys_callback(secp_ctx, &path, session_priv, callback)
		.expect("Route that we sent via spontaneously grew invalid keys in the middle of it?");

	if let Some(FailureLearnings {
		network_update,
		short_channel_id,
		payment_failed_permanently,
		failed_within_blinded_path,
	}) = res
	{
		DecodedOnionFailure {
			network_update,
			short_channel_id,
			payment_failed_permanently,
			failed_within_blinded_path,
			#[cfg(test)]
			onion_error_code: error_code_ret,
			#[cfg(test)]
			onion_error_data: error_packet_ret,
		}
	} else {
		// only not set either packet unparseable or hmac does not match with any
		// payment not retryable only when garbage is from the final node
		DecodedOnionFailure {
			network_update: None,
			short_channel_id: None,
			payment_failed_permanently: is_from_final_node,
			failed_within_blinded_path: false,
			#[cfg(test)]
			onion_error_code: None,
			#[cfg(test)]
			onion_error_data: None,
		}
	}
}

#[derive(Clone)] // See Channel::revoke_and_ack for why, tl;dr: Rust bug
#[cfg_attr(test, derive(PartialEq))]
pub(super) struct HTLCFailReason(HTLCFailReasonRepr);

#[derive(Clone)] // See Channel::revoke_and_ack for why, tl;dr: Rust bug
#[cfg_attr(test, derive(PartialEq))]
enum HTLCFailReasonRepr {
	LightningError { err: msgs::OnionErrorPacket },
	Reason { failure_code: u16, data: Vec<u8> },
}

impl core::fmt::Debug for HTLCFailReason {
	fn fmt(&self, f: &mut core::fmt::Formatter) -> Result<(), core::fmt::Error> {
		match self.0 {
			HTLCFailReasonRepr::Reason { ref failure_code, .. } => {
				write!(f, "HTLC error code {}", failure_code)
			},
			HTLCFailReasonRepr::LightningError { .. } => {
				write!(f, "pre-built LightningError")
			},
		}
	}
}

impl Writeable for HTLCFailReason {
	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), crate::io::Error> {
		self.0.write(writer)
	}
}
impl Readable for HTLCFailReason {
	fn read<R: Read>(reader: &mut R) -> Result<Self, msgs::DecodeError> {
		Ok(Self(Readable::read(reader)?))
	}
}

impl_writeable_tlv_based_enum!(HTLCFailReasonRepr,
	(0, LightningError) => {
		(0, err, required),
	},
	(1, Reason) => {
		(0, failure_code, required),
		(2, data, required_vec),
	},
);

impl HTLCFailReason {
	#[rustfmt::skip]
	pub(super) fn reason(failure_code: u16, data: Vec<u8>) -> Self {
		const BADONION: u16 = 0x8000;
		const PERM: u16 = 0x4000;
		const NODE: u16 = 0x2000;
		const UPDATE: u16 = 0x1000;

		     if failure_code == 1  | PERM { debug_assert!(data.is_empty()) }
		else if failure_code == 2  | NODE { debug_assert!(data.is_empty()) }
		else if failure_code == 2  | PERM | NODE { debug_assert!(data.is_empty()) }
		else if failure_code == 3  | PERM | NODE { debug_assert!(data.is_empty()) }
		else if failure_code == 4  | BADONION | PERM { debug_assert_eq!(data.len(), 32) }
		else if failure_code == 5  | BADONION | PERM { debug_assert_eq!(data.len(), 32) }
		else if failure_code == 6  | BADONION | PERM { debug_assert_eq!(data.len(), 32) }
		else if failure_code == 7  | UPDATE {
			debug_assert_eq!(data.len() - 2, u16::from_be_bytes(data[0..2].try_into().unwrap()) as usize) }
		else if failure_code == 8  | PERM { debug_assert!(data.is_empty()) }
		else if failure_code == 9  | PERM { debug_assert!(data.is_empty()) }
		else if failure_code == 10 | PERM { debug_assert!(data.is_empty()) }
		else if failure_code == 11 | UPDATE {
			debug_assert_eq!(data.len() - 2 - 8, u16::from_be_bytes(data[8..10].try_into().unwrap()) as usize) }
		else if failure_code == 12 | UPDATE {
			debug_assert_eq!(data.len() - 2 - 8, u16::from_be_bytes(data[8..10].try_into().unwrap()) as usize) }
		else if failure_code == 13 | UPDATE {
			debug_assert_eq!(data.len() - 2 - 4, u16::from_be_bytes(data[4..6].try_into().unwrap()) as usize) }
		else if failure_code == 14 | UPDATE {
			debug_assert_eq!(data.len() - 2, u16::from_be_bytes(data[0..2].try_into().unwrap()) as usize) }
		else if failure_code == 15 | PERM { debug_assert_eq!(data.len(), 12) }
		else if failure_code == 18 { debug_assert_eq!(data.len(), 4) }
		else if failure_code == 19 { debug_assert_eq!(data.len(), 8) }
		else if failure_code == 20 | UPDATE {
			debug_assert_eq!(data.len() - 2 - 2, u16::from_be_bytes(data[2..4].try_into().unwrap()) as usize) }
		else if failure_code == 21 { debug_assert!(data.is_empty()) }
		else if failure_code == 22 | PERM { debug_assert!(data.len() <= 11) }
		else if failure_code == 23 { debug_assert!(data.is_empty()) }
		else if failure_code & BADONION != 0 {
			// We set some bogus BADONION failure codes in test, so ignore unknown ones.
		}
		else { debug_assert!(false, "Unknown failure code: {}", failure_code) }

		Self(HTLCFailReasonRepr::Reason { failure_code, data })
	}

	pub(super) fn from_failure_code(failure_code: u16) -> Self {
		Self::reason(failure_code, Vec::new())
	}

	pub(super) fn from_msg(msg: &msgs::UpdateFailHTLC) -> Self {
		Self(HTLCFailReasonRepr::LightningError { err: msg.reason.clone() })
	}

	pub(super) fn get_encrypted_failure_packet(
		&self, incoming_packet_shared_secret: &[u8; 32], phantom_shared_secret: &Option<[u8; 32]>,
	) -> msgs::OnionErrorPacket {
		match self.0 {
			HTLCFailReasonRepr::Reason { ref failure_code, ref data } => {
				if let Some(phantom_ss) = phantom_shared_secret {
					let phantom_packet =
						build_failure_packet(phantom_ss, *failure_code, &data[..]).encode();
					let encrypted_phantom_packet =
						encrypt_failure_packet(phantom_ss, &phantom_packet);
					encrypt_failure_packet(
						incoming_packet_shared_secret,
						&encrypted_phantom_packet.data[..],
					)
				} else {
					let packet = build_failure_packet(
						incoming_packet_shared_secret,
						*failure_code,
						&data[..],
					)
					.encode();
					encrypt_failure_packet(incoming_packet_shared_secret, &packet)
				}
			},
			HTLCFailReasonRepr::LightningError { ref err } => {
				encrypt_failure_packet(incoming_packet_shared_secret, &err.data)
			},
		}
	}

	pub(super) fn decode_onion_failure<T: secp256k1::Signing, L: Deref>(
		&self, secp_ctx: &Secp256k1<T>, logger: &L, htlc_source: &HTLCSource,
	) -> DecodedOnionFailure
	where
		L::Target: Logger,
	{
		match self.0 {
			HTLCFailReasonRepr::LightningError { ref err } => {
				process_onion_failure(secp_ctx, logger, &htlc_source, err.data.clone())
			},
			#[allow(unused)]
			HTLCFailReasonRepr::Reason { ref failure_code, ref data, .. } => {
				// we get a fail_malformed_htlc from the first hop
				// TODO: We'd like to generate a NetworkUpdate for temporary
				// failures here, but that would be insufficient as find_route
				// generally ignores its view of our own channels as we provide them via
				// ChannelDetails.
				if let &HTLCSource::OutboundRoute { ref path, .. } = htlc_source {
					DecodedOnionFailure {
						network_update: None,
						payment_failed_permanently: false,
						short_channel_id: Some(path.hops[0].short_channel_id),
						failed_within_blinded_path: false,
						#[cfg(test)]
						onion_error_code: Some(*failure_code),
						#[cfg(test)]
						onion_error_data: Some(data.clone()),
					}
				} else {
					unreachable!();
				}
			},
		}
	}
}

/// Allows `decode_next_hop` to return the next hop packet bytes for either payments or onion
/// message forwards.
pub(crate) trait NextPacketBytes: AsMut<[u8]> {
	fn new(len: usize) -> Self;
}

impl NextPacketBytes for FixedSizeOnionPacket {
	fn new(_len: usize) -> Self {
		Self([0 as u8; ONION_DATA_LEN])
	}
}

impl NextPacketBytes for Vec<u8> {
	fn new(len: usize) -> Self {
		vec![0 as u8; len]
	}
}

/// Data decrypted from a payment's onion payload.
pub(crate) enum Hop {
	/// This onion payload was for us, not for forwarding to a next-hop. Contains information for
	/// verifying the incoming payment.
	Receive(msgs::InboundOnionPayload),
	/// This onion payload needs to be forwarded to a next-hop.
	Forward {
		/// Onion payload data used in forwarding the payment.
		next_hop_data: msgs::InboundOnionPayload,
		/// HMAC of the next hop's onion packet.
		next_hop_hmac: [u8; 32],
		/// Bytes of the onion packet we're forwarding.
		new_packet_bytes: [u8; ONION_DATA_LEN],
	},
}

impl Hop {
	pub(crate) fn is_intro_node_blinded_forward(&self) -> bool {
		match self {
			Self::Forward {
				next_hop_data:
					msgs::InboundOnionPayload::BlindedForward {
						intro_node_blinding_point: Some(_), ..
					},
				..
			} => true,
			_ => false,
		}
	}
}

/// Error returned when we fail to decode the onion packet.
#[derive(Debug)]
pub(crate) enum OnionDecodeErr {
	/// The HMAC of the onion packet did not match the hop data.
	Malformed { err_msg: &'static str, err_code: u16 },
	/// We failed to decode the onion payload.
	Relay { err_msg: &'static str, err_code: u16 },
}

pub(crate) fn decode_next_payment_hop<NS: Deref>(
	shared_secret: [u8; 32], hop_data: &[u8], hmac_bytes: [u8; 32], payment_hash: PaymentHash,
	blinding_point: Option<PublicKey>, node_signer: NS,
) -> Result<Hop, OnionDecodeErr>
where
	NS::Target: NodeSigner,
{
	match decode_next_hop(
		shared_secret,
		hop_data,
		hmac_bytes,
		Some(payment_hash),
		(blinding_point, node_signer),
	) {
		Ok((next_hop_data, None)) => Ok(Hop::Receive(next_hop_data)),
		Ok((next_hop_data, Some((next_hop_hmac, FixedSizeOnionPacket(new_packet_bytes))))) => {
			Ok(Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes })
		},
		Err(e) => Err(e),
	}
}

/// Build a payment onion, returning the first hop msat and cltv values as well.
/// `cur_block_height` should be set to the best known block height + 1.
pub fn create_payment_onion<T: secp256k1::Signing>(
	secp_ctx: &Secp256k1<T>, path: &Path, session_priv: &SecretKey, total_msat: u64,
	recipient_onion: &RecipientOnionFields, cur_block_height: u32, payment_hash: &PaymentHash,
	keysend_preimage: &Option<PaymentPreimage>, invoice_request: Option<&InvoiceRequest>,
	prng_seed: [u8; 32],
) -> Result<(msgs::OnionPacket, u64, u32), APIError> {
	let onion_keys = construct_onion_keys(&secp_ctx, &path, &session_priv).map_err(|_| {
		APIError::InvalidRoute { err: "Pubkey along hop was maliciously selected".to_owned() }
	})?;
	let (onion_payloads, htlc_msat, htlc_cltv) = build_onion_payloads(
		&path,
		total_msat,
		recipient_onion,
		cur_block_height,
		keysend_preimage,
		invoice_request,
	)?;
	let onion_packet = construct_onion_packet(onion_payloads, onion_keys, prng_seed, payment_hash)
		.map_err(|_| APIError::InvalidRoute {
			err: "Route size too large considering onion data".to_owned(),
		})?;
	Ok((onion_packet, htlc_msat, htlc_cltv))
}

pub(crate) fn decode_next_untagged_hop<T, R: ReadableArgs<T>, N: NextPacketBytes>(
	shared_secret: [u8; 32], hop_data: &[u8], hmac_bytes: [u8; 32], read_args: T,
) -> Result<(R, Option<([u8; 32], N)>), OnionDecodeErr> {
	decode_next_hop(shared_secret, hop_data, hmac_bytes, None, read_args)
}

fn decode_next_hop<T, R: ReadableArgs<T>, N: NextPacketBytes>(
	shared_secret: [u8; 32], hop_data: &[u8], hmac_bytes: [u8; 32],
	payment_hash: Option<PaymentHash>, read_args: T,
) -> Result<(R, Option<([u8; 32], N)>), OnionDecodeErr> {
	let (rho, mu) = gen_rho_mu_from_shared_secret(&shared_secret);
	let mut hmac = HmacEngine::<Sha256>::new(&mu);
	hmac.input(hop_data);
	if let Some(tag) = payment_hash {
		hmac.input(&tag.0[..]);
	}
	if !fixed_time_eq(&Hmac::from_engine(hmac).to_byte_array(), &hmac_bytes) {
		return Err(OnionDecodeErr::Malformed {
			err_msg: "HMAC Check failed",
			err_code: 0x8000 | 0x4000 | 5,
		});
	}

	let mut chacha = ChaCha20::new(&rho, &[0u8; 8]);
	let mut chacha_stream = ChaChaReader { chacha: &mut chacha, read: Cursor::new(&hop_data[..]) };
	match R::read(&mut chacha_stream, read_args) {
		Err(err) => {
			let error_code = match err {
				// Unknown realm byte
				msgs::DecodeError::UnknownVersion => 0x4000 | 1,
				// invalid_onion_payload
				msgs::DecodeError::UnknownRequiredFeature
				| msgs::DecodeError::InvalidValue
				| msgs::DecodeError::ShortRead => 0x4000 | 22,
				// Should never happen
				_ => 0x2000 | 2,
			};
			return Err(OnionDecodeErr::Relay {
				err_msg: "Unable to decode our hop data",
				err_code: error_code,
			});
		},
		Ok(msg) => {
			let mut hmac = [0; 32];
			if let Err(_) = chacha_stream.read_exact(&mut hmac[..]) {
				return Err(OnionDecodeErr::Relay {
					err_msg: "Unable to decode our hop data",
					err_code: 0x4000 | 22,
				});
			}
			if hmac == [0; 32] {
				#[cfg(test)]
				{
					if chacha_stream.read.position() < hop_data.len() as u64 - 64 {
						// In tests, make sure that the initial onion packet data is, at least, non-0.
						// We could do some fancy randomness test here, but, ehh, whatever.
						// This checks for the issue where you can calculate the path length given the
						// onion data as all the path entries that the originator sent will be here
						// as-is (and were originally 0s).
						// Of course reverse path calculation is still pretty easy given naive routing
						// algorithms, but this fixes the most-obvious case.
						let mut next_bytes = [0; 32];
						chacha_stream.read_exact(&mut next_bytes).unwrap();
						assert_ne!(next_bytes[..], [0; 32][..]);
						chacha_stream.read_exact(&mut next_bytes).unwrap();
						assert_ne!(next_bytes[..], [0; 32][..]);
					}
				}
				return Ok((msg, None)); // We are the final destination for this packet
			} else {
				let mut new_packet_bytes = N::new(hop_data.len());
				let read_pos = hop_data.len() - chacha_stream.read.position() as usize;
				chacha_stream.read_exact(&mut new_packet_bytes.as_mut()[..read_pos]).unwrap();
				#[cfg(debug_assertions)]
				{
					// Check two things:
					// a) that the behavior of our stream here will return Ok(0) even if the TLV
					//    read above emptied out our buffer and the unwrap() wont needlessly panic
					// b) that we didn't somehow magically end up with extra data.
					let mut t = [0; 1];
					debug_assert!(chacha_stream.read(&mut t).unwrap() == 0);
				}
				// Once we've emptied the set of bytes our peer gave us, encrypt 0 bytes until we
				// fill the onion hop data we'll forward to our next-hop peer.
				chacha_stream.chacha.process_in_place(&mut new_packet_bytes.as_mut()[read_pos..]);
				return Ok((msg, Some((hmac, new_packet_bytes)))); // This packet needs forwarding
			}
		},
	}
}

#[cfg(test)]
mod tests {
	use crate::io;
	use crate::ln::msgs;
	use crate::routing::router::{Path, PaymentParameters, Route, RouteHop};
	use crate::types::features::{ChannelFeatures, NodeFeatures};
	use crate::types::payment::PaymentHash;
	use crate::util::ser::{VecWriter, Writeable, Writer};

	#[allow(unused_imports)]
	use crate::prelude::*;

	use bitcoin::hex::FromHex;
	use bitcoin::secp256k1::Secp256k1;
	use bitcoin::secp256k1::{PublicKey, SecretKey};

	use super::*;

	fn get_test_session_key() -> SecretKey {
		let hex = "4141414141414141414141414141414141414141414141414141414141414141";
		SecretKey::from_slice(&<Vec<u8>>::from_hex(hex).unwrap()[..]).unwrap()
	}

	fn build_test_onion_keys() -> Vec<OnionKeys> {
		// Keys from BOLT 4, used in both test vector tests
		let secp_ctx = Secp256k1::new();

		let route = Route {
			paths: vec![Path { hops: vec![
					RouteHop {
						pubkey: PublicKey::from_slice(&<Vec<u8>>::from_hex("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
						channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
						short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0, maybe_announced_channel: true, // We fill in the payloads manually instead of generating them from RouteHops.
					},
					RouteHop {
						pubkey: PublicKey::from_slice(&<Vec<u8>>::from_hex("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
						channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
						short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0, maybe_announced_channel: true, // We fill in the payloads manually instead of generating them from RouteHops.
					},
					RouteHop {
						pubkey: PublicKey::from_slice(&<Vec<u8>>::from_hex("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007").unwrap()[..]).unwrap(),
						channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
						short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0, maybe_announced_channel: true, // We fill in the payloads manually instead of generating them from RouteHops.
					},
					RouteHop {
						pubkey: PublicKey::from_slice(&<Vec<u8>>::from_hex("032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991").unwrap()[..]).unwrap(),
						channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
						short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0, maybe_announced_channel: true, // We fill in the payloads manually instead of generating them from RouteHops.
					},
					RouteHop {
						pubkey: PublicKey::from_slice(&<Vec<u8>>::from_hex("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145").unwrap()[..]).unwrap(),
						channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
						short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0, maybe_announced_channel: true, // We fill in the payloads manually instead of generating them from RouteHops.
					},
			], blinded_tail: None }],
			route_params: None,
		};

		let onion_keys =
			super::construct_onion_keys(&secp_ctx, &route.paths[0], &get_test_session_key())
				.unwrap();
		assert_eq!(onion_keys.len(), route.paths[0].hops.len());
		onion_keys
	}

	#[test]
	fn onion_vectors() {
		let onion_keys = build_test_onion_keys();

		// Test generation of ephemeral keys and secrets. These values used to be part of the BOLT4
		// test vectors, but have since been removed. We keep them as they provide test coverage.
		let hex = "53eb63ea8a3fec3b3cd433b85cd62a4b145e1dda09391b348c4e1cd36a03ea66";
		assert_eq!(
			onion_keys[0].shared_secret.secret_bytes(),
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "2ec2e5da605776054187180343287683aa6a51b4b1c04d6dd49c45d8cffb3c36";
		assert_eq!(onion_keys[0].blinding_factor[..], <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619";
		assert_eq!(
			onion_keys[0].ephemeral_pubkey.serialize()[..],
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "ce496ec94def95aadd4bec15cdb41a740c9f2b62347c4917325fcc6fb0453986";
		assert_eq!(onion_keys[0].rho, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "b57061dc6d0a2b9f261ac410c8b26d64ac5506cbba30267a649c28c179400eba";
		assert_eq!(onion_keys[0].mu, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "a6519e98832a0b179f62123b3567c106db99ee37bef036e783263602f3488fae";
		assert_eq!(
			onion_keys[1].shared_secret.secret_bytes(),
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "bf66c28bc22e598cfd574a1931a2bafbca09163df2261e6d0056b2610dab938f";
		assert_eq!(onion_keys[1].blinding_factor[..], <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "028f9438bfbf7feac2e108d677e3a82da596be706cc1cf342b75c7b7e22bf4e6e2";
		assert_eq!(
			onion_keys[1].ephemeral_pubkey.serialize()[..],
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "450ffcabc6449094918ebe13d4f03e433d20a3d28a768203337bc40b6e4b2c59";
		assert_eq!(onion_keys[1].rho, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "05ed2b4a3fb023c2ff5dd6ed4b9b6ea7383f5cfe9d59c11d121ec2c81ca2eea9";
		assert_eq!(onion_keys[1].mu, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "3a6b412548762f0dbccce5c7ae7bb8147d1caf9b5471c34120b30bc9c04891cc";
		assert_eq!(
			onion_keys[2].shared_secret.secret_bytes(),
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "a1f2dadd184eb1627049673f18c6325814384facdee5bfd935d9cb031a1698a5";
		assert_eq!(onion_keys[2].blinding_factor[..], <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "03bfd8225241ea71cd0843db7709f4c222f62ff2d4516fd38b39914ab6b83e0da0";
		assert_eq!(
			onion_keys[2].ephemeral_pubkey.serialize()[..],
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "11bf5c4f960239cb37833936aa3d02cea82c0f39fd35f566109c41f9eac8deea";
		assert_eq!(onion_keys[2].rho, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "caafe2820fa00eb2eeb78695ae452eba38f5a53ed6d53518c5c6edf76f3f5b78";
		assert_eq!(onion_keys[2].mu, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "21e13c2d7cfe7e18836df50872466117a295783ab8aab0e7ecc8c725503ad02d";
		assert_eq!(
			onion_keys[3].shared_secret.secret_bytes(),
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "7cfe0b699f35525029ae0fa437c69d0f20f7ed4e3916133f9cacbb13c82ff262";
		assert_eq!(onion_keys[3].blinding_factor[..], <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "031dde6926381289671300239ea8e57ffaf9bebd05b9a5b95beaf07af05cd43595";
		assert_eq!(
			onion_keys[3].ephemeral_pubkey.serialize()[..],
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "cbe784ab745c13ff5cffc2fbe3e84424aa0fd669b8ead4ee562901a4a4e89e9e";
		assert_eq!(onion_keys[3].rho, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "5052aa1b3d9f0655a0932e50d42f0c9ba0705142c25d225515c45f47c0036ee9";
		assert_eq!(onion_keys[3].mu, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "b5756b9b542727dbafc6765a49488b023a725d631af688fc031217e90770c328";
		assert_eq!(
			onion_keys[4].shared_secret.secret_bytes(),
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "c96e00dddaf57e7edcd4fb5954be5b65b09f17cb6d20651b4e90315be5779205";
		assert_eq!(onion_keys[4].blinding_factor[..], <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "03a214ebd875aab6ddfd77f22c5e7311d7f77f17a169e599f157bbcdae8bf071f4";
		assert_eq!(
			onion_keys[4].ephemeral_pubkey.serialize()[..],
			<Vec<u8>>::from_hex(hex).unwrap()[..]
		);

		let hex = "034e18b8cc718e8af6339106e706c52d8df89e2b1f7e9142d996acf88df8799b";
		assert_eq!(onion_keys[4].rho, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		let hex = "8e45e5c61c2b24cb6382444db6698727afb063adecd72aada233d4bf273d975a";
		assert_eq!(onion_keys[4].mu, <Vec<u8>>::from_hex(hex).unwrap()[..]);

		// Packet creation test vectors from BOLT 4 (see
		// https://github.com/lightning/bolts/blob/16973e2b857e853308cafd59e42fa830d75b1642/bolt04/onion-test.json).
		// Note that we represent the test vector payloads 2 and 5 through RawOnionHopData::data
		// with raw hex instead of our in-memory enums, as the payloads contains custom types, and
		// we have no way of representing that with our enums.
		let payloads = vec!(
			RawOnionHopData::new(msgs::OutboundOnionPayload::Forward {
				short_channel_id: 1,
				amt_to_forward: 15000,
				outgoing_cltv_value: 1500,
			}),
			/*
			The second payload is represented by raw hex as it contains custom type data. Content:
			1. length "52" (payload_length 82).

			The first part of the payload has the `NonFinalNode` format, with content as follows:
			2. amt_to_forward "020236b0"
			   02 (type amt_to_forward) 02 (length 2) 36b0 (value 14000)
			3. outgoing_cltv_value "04020578"
			   04 (type outgoing_cltv_value) 02 (length 2) 0578 (value 1400)
			4. short_channel_id "06080000000000000002"
			   06 (type short_channel_id) 08 (length 8) 0000000000000002 (value 2)

			The rest of the payload is custom type data:
			5. custom_record "fd02013c0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f"
			*/
			RawOnionHopData {
				data: <Vec<u8>>::from_hex("52020236b00402057806080000000000000002fd02013c0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f0102030405060708090a0b0c0d0e0f").unwrap(),
			},
			RawOnionHopData::new(msgs::OutboundOnionPayload::Forward {
				short_channel_id: 3,
				amt_to_forward: 12500,
				outgoing_cltv_value: 1250,
			}),
			RawOnionHopData::new(msgs::OutboundOnionPayload::Forward {
				short_channel_id: 4,
				amt_to_forward: 10000,
				outgoing_cltv_value: 1000,
			}),
			/*
			The fifth payload is represented by raw hex as it contains custom type data. Content:
			1. length "fd0110" (payload_length 272).

			The first part of the payload has the `FinalNode` format, with content as follows:
			1. amt_to_forward "02022710"
			   02 (type amt_to_forward) 02 (length 2) 2710 (value 10000)
			2. outgoing_cltv_value "040203e8"
			   04 (type outgoing_cltv_value) 02 (length 2) 03e8 (value 1000)
			3. payment_data "082224a33562c54507a9334e79f0dc4f17d407e6d7c61f0e2f3d0d38599502f617042710"
			   08 (type short_channel_id) 22 (length 34) 24a33562c54507a9334e79f0dc4f17d407e6d7c61f0e2f3d0d38599502f61704 (payment_secret) 2710 (total_msat value 10000)

			The rest of the payload is custom type data:
			4. custom_record "fd012de02a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a"
			*/
			RawOnionHopData {
				data: <Vec<u8>>::from_hex("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").unwrap(),
			},
		);

		// Verify that the serialized OnionHopDataFormat::NonFinalNode tlv payloads matches the test vectors
		let mut w = VecWriter(Vec::new());
		payloads[0].write(&mut w).unwrap();
		let hop_1_serialized_payload = w.0;
		let hex = "1202023a98040205dc06080000000000000001";
		let expected_serialized_hop_1_payload = &<Vec<u8>>::from_hex(hex).unwrap()[..];
		assert_eq!(hop_1_serialized_payload, expected_serialized_hop_1_payload);

		w = VecWriter(Vec::new());
		payloads[2].write(&mut w).unwrap();
		let hop_3_serialized_payload = w.0;
		let hex = "12020230d4040204e206080000000000000003";
		let expected_serialized_hop_3_payload = &<Vec<u8>>::from_hex(hex).unwrap()[..];
		assert_eq!(hop_3_serialized_payload, expected_serialized_hop_3_payload);

		w = VecWriter(Vec::new());
		payloads[3].write(&mut w).unwrap();
		let hop_4_serialized_payload = w.0;
		let hex = "1202022710040203e806080000000000000004";
		let expected_serialized_hop_4_payload = &<Vec<u8>>::from_hex(hex).unwrap()[..];
		assert_eq!(hop_4_serialized_payload, expected_serialized_hop_4_payload);

		let pad_keytype_seed =
			super::gen_pad_from_shared_secret(&get_test_session_key().secret_bytes());

		let packet: msgs::OnionPacket = super::construct_onion_packet_with_writable_hopdata::<_>(
			payloads,
			onion_keys,
			pad_keytype_seed,
			&PaymentHash([0x42; 32]),
		)
		.unwrap();

		let hex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
		assert_eq!(packet.encode(), <Vec<u8>>::from_hex(hex).unwrap());
	}

	#[test]
	fn test_failure_packet_onion() {
		// Returning Errors test vectors from BOLT 4

		let onion_keys = build_test_onion_keys();
		let onion_error =
			super::build_failure_packet(onion_keys[4].shared_secret.as_ref(), 0x2002, &[0; 0]);
		let hex = "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";
		assert_eq!(onion_error.encode(), <Vec<u8>>::from_hex(hex).unwrap());

		let onion_packet_1 = super::encrypt_failure_packet(
			onion_keys[4].shared_secret.as_ref(),
			&onion_error.encode()[..],
		);
		let hex = "a5e6bd0c74cb347f10cce367f949098f2457d14c046fd8a22cb96efb30b0fdcda8cb9168b50f2fd45edd73c1b0c8b33002df376801ff58aaa94000bf8a86f92620f343baef38a580102395ae3abf9128d1047a0736ff9b83d456740ebbb4aeb3aa9737f18fb4afb4aa074fb26c4d702f42968888550a3bded8c05247e045b866baef0499f079fdaeef6538f31d44deafffdfd3afa2fb4ca9082b8f1c465371a9894dd8c243fb4847e004f5256b3e90e2edde4c9fb3082ddfe4d1e734cacd96ef0706bf63c9984e22dc98851bcccd1c3494351feb458c9c6af41c0044bea3c47552b1d992ae542b17a2d0bba1a096c78d169034ecb55b6e3a7263c26017f033031228833c1daefc0dedb8cf7c3e37c9c37ebfe42f3225c326e8bcfd338804c145b16e34e4";
		assert_eq!(onion_packet_1.data, <Vec<u8>>::from_hex(hex).unwrap());

		let onion_packet_2 = super::encrypt_failure_packet(
			onion_keys[3].shared_secret.as_ref(),
			&onion_packet_1.data[..],
		);
		let hex = "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";
		assert_eq!(onion_packet_2.data, <Vec<u8>>::from_hex(hex).unwrap());

		let onion_packet_3 = super::encrypt_failure_packet(
			onion_keys[2].shared_secret.as_ref(),
			&onion_packet_2.data[..],
		);
		let hex = "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";
		assert_eq!(onion_packet_3.data, <Vec<u8>>::from_hex(hex).unwrap());

		let onion_packet_4 = super::encrypt_failure_packet(
			onion_keys[1].shared_secret.as_ref(),
			&onion_packet_3.data[..],
		);
		let hex = "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";
		assert_eq!(onion_packet_4.data, <Vec<u8>>::from_hex(hex).unwrap());

		let onion_packet_5 = super::encrypt_failure_packet(
			onion_keys[0].shared_secret.as_ref(),
			&onion_packet_4.data[..],
		);
		let hex = "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";
		assert_eq!(onion_packet_5.data, <Vec<u8>>::from_hex(hex).unwrap());
	}

	struct RawOnionHopData {
		data: Vec<u8>,
	}
	impl RawOnionHopData {
		fn new(orig: msgs::OutboundOnionPayload) -> Self {
			Self { data: orig.encode() }
		}
	}
	impl Writeable for RawOnionHopData {
		fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
			writer.write_all(&self.data[..])
		}
	}

	#[test]
	fn max_length_with_no_cltv_limit() {
		// While users generally shouldn't do this, we shouldn't overflow when
		// `max_total_cltv_expiry_delta` is `u32::MAX`.
		let recipient = PublicKey::from_slice(&[2; 33]).unwrap();
		let mut route_params = RouteParameters {
			payment_params: PaymentParameters::for_keysend(recipient, u32::MAX, true),
			final_value_msat: u64::MAX,
			max_total_routing_fee_msat: Some(u64::MAX),
		};
		route_params.payment_params.max_total_cltv_expiry_delta = u32::MAX;
		let recipient_onion = RecipientOnionFields::spontaneous_empty();
		set_max_path_length(&mut route_params, &recipient_onion, None, None, 42).unwrap();
	}
}