Struct-ify onion util internal result type

[rust-lightning] / lightning / src / 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::ln::{PaymentHash, PaymentPreimage};
use crate::ln::channelmanager::{HTLCSource, RecipientOnionFields};
use crate::ln::msgs;
use crate::ln::wire::Encode;
use crate::routing::gossip::NetworkUpdate;
use crate::routing::router::{BlindedTail, Path, RouteHop};
use crate::sign::NodeSigner;
use crate::util::chacha20::{ChaCha20, ChaChaReader};
use crate::util::errors::{self, APIError};
use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer, LengthCalculatingWriter};
use crate::util::logger::Logger;

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

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

use crate::prelude::*;
use crate::io::{Cursor, Read};
use core::convert::{AsMut, TryInto};
use core::ops::Deref;

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).into_inner()
}

#[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 hmac = HmacEngine::<Sha256>::new(&[0x72, 0x68, 0x6f]); // rho
                hmac.input(&shared_secret);
                Hmac::from_engine(hmac).into_inner()
        },
        {
                let mut hmac = HmacEngine::<Sha256>::new(&[0x6d, 0x75]); // mu
                hmac.input(&shared_secret);
                Hmac::from_engine(hmac).into_inner()
        })
}

#[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).into_inner()
}

#[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).into_inner()
}

#[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).into_inner()
}

/// 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::Signing + 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).into_inner()
        };

        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).into_inner();

                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(path: &Path, total_msat: u64, mut recipient_onion: RecipientOnionFields, starting_htlc_offset: u32, keysend_preimage: &Option<PaymentPreimage>) -> Result<(Vec<msgs::OutboundOnionPayload>, u64, u32), APIError> {
        let mut cur_value_msat = 0u64;
        let mut cur_cltv = starting_htlc_offset;
        let mut last_short_channel_id = 0;
        let mut res: Vec<msgs::OutboundOnionPayload> = Vec::with_capacity(
                path.hops.len() + path.blinded_tail.as_ref().map_or(0, |t| t.hops.len())
        );

        for (idx, hop) in path.hops.iter().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 + starting_htlc_offset } else { cur_cltv };
                if idx == 0 {
                        if let Some(BlindedTail {
                                blinding_point, hops, final_value_msat, excess_final_cltv_expiry_delta, ..
                        }) = &path.blinded_tail {
                                let mut blinding_point = Some(*blinding_point);
                                for (i, blinded_hop) in hops.iter().enumerate() {
                                        if i == hops.len() - 1 {
                                                cur_value_msat += final_value_msat;
                                                cur_cltv += excess_final_cltv_expiry_delta;
                                                res.push(msgs::OutboundOnionPayload::BlindedReceive {
                                                        amt_msat: *final_value_msat,
                                                        total_msat,
                                                        outgoing_cltv_value: cltv,
                                                        encrypted_tlvs: blinded_hop.encrypted_payload.clone(),
                                                        intro_node_blinding_point: blinding_point.take(),
                                                });
                                        } else {
                                                res.push(msgs::OutboundOnionPayload::BlindedForward {
                                                        encrypted_tlvs: blinded_hop.encrypted_payload.clone(),
                                                        intro_node_blinding_point: blinding_point.take(),
                                                });
                                        }
                                }
                        } else {
                                res.push(msgs::OutboundOnionPayload::Receive {
                                        payment_data: if let Some(secret) = recipient_onion.payment_secret.take() {
                                                Some(msgs::FinalOnionHopData {
                                                        payment_secret: secret,
                                                        total_msat,
                                                })
                                        } else { None },
                                        payment_metadata: recipient_onion.payment_metadata.take(),
                                        keysend_preimage: *keysend_preimage,
                                        custom_tlvs: recipient_onion.custom_tlvs.clone(),
                                        amt_msat: value_msat,
                                        outgoing_cltv_value: cltv,
                                });
                        }
                } else {
                        res.insert(0, msgs::OutboundOnionPayload::Forward {
                                short_channel_id: last_short_channel_id,
                                amt_to_forward: value_msat,
                                outgoing_cltv_value: cltv,
                        });
                }
                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 += 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((res, cur_value_msat, cur_cltv))
}

/// 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;

#[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);

        construct_onion_packet_with_init_noise::<_, _>(
                payloads, onion_keys, FixedSizeOnionPacket(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);

        construct_onion_packet_with_init_noise::<_, _>(
                payloads, onion_keys, FixedSizeOnionPacket(packet_data), 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() {
                        if i == payloads.len() - 1 { break; }

                        let mut chacha = ChaCha20::new(&keys.rho, &[0u8; 8]);
                        for _ in 0..(packet_data.len() - pos) { // TODO: Batch this.
                                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(());
                        }

                        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).into_inner();
        }

        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).into_inner();

        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_retryable: bool,
        #[cfg(test)]
        pub(crate) onion_error_code: Option<u16>,
        #[cfg(test)]
        pub(crate) onion_error_data: Option<Vec<u8>>,
}

/// 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 packet_decrypted: Vec<u8>
) -> DecodedOnionFailure where L::Target: Logger {
        let (path, session_priv, first_hop_htlc_msat) = if let &HTLCSource::OutboundRoute {
                ref path, ref session_priv, ref first_hop_htlc_msat, ..
        } = htlc_source {
                (path, session_priv, first_hop_htlc_msat)
        } else { 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,
        }
        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
        construct_onion_keys_callback(secp_ctx, &path, session_priv,
                |shared_secret, _, _, route_hop_opt, 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]);
                                is_from_final_node = false;
                                return
                        },
                };

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

                let ammag = gen_ammag_from_shared_secret(shared_secret.as_ref());

                let mut decryption_tmp = Vec::with_capacity(packet_decrypted.len());
                decryption_tmp.resize(packet_decrypted.len(), 0);
                let mut chacha = ChaCha20::new(&ammag, &[0u8; 8]);
                chacha.process(&packet_decrypted, &mut decryption_tmp[..]);
                packet_decrypted = decryption_tmp;

                // 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).
                is_from_final_node = route_hop_idx + 1 == path.hops.len();
                let failing_route_hop = if is_from_final_node { route_hop } else { &path.hops[route_hop_idx + 1] };

                let err_packet = match msgs::DecodedOnionErrorPacket::read(&mut Cursor::new(&packet_decrypted)) {
                        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).into_inner(), &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
                                });
                                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 let Some(mut update_slice) = err_packet.failuremsg.get(debug_field_size + 4..debug_field_size + 4 + update_len) {
                                        // Historically, the BOLTs were unclear if the message type
                                        // bytes should be included here or not. The BOLTs have now
                                        // been updated to indicate that they *are* included, but many
                                        // nodes still send messages without the type bytes, so we
                                        // support both here.
                                        // TODO: Switch to hard require the type prefix, as the current
                                        // permissiveness introduces the (although small) possibility
                                        // that we fail to decode legitimate channel updates that
                                        // happen to start with ChannelUpdate::TYPE, i.e., [0x01, 0x02].
                                        if update_slice.len() > 2 && update_slice[0..2] == msgs::ChannelUpdate::TYPE.to_be_bytes() {
                                                update_slice = &update_slice[2..];
                                        } else {
                                                log_trace!(logger, "Failure provided features a channel update without type prefix. Deprecated, but allowing for now.");
                                        }
                                        let update_opt = msgs::ChannelUpdate::read(&mut Cursor::new(&update_slice));
                                        if update_opt.is_ok() || update_slice.is_empty() {
                                                // if channel_update should NOT have caused the failure:
                                                // MAY treat the channel_update as invalid.
                                                let is_chan_update_invalid = match error_code & 0xff {
                                                        7 => false,
                                                        11 => update_opt.is_ok() &&
                                                                amt_to_forward >
                                                                        update_opt.as_ref().unwrap().contents.htlc_minimum_msat,
                                                        12 => update_opt.is_ok() && amt_to_forward
                                                                .checked_mul(update_opt.as_ref().unwrap()
                                                                        .contents.fee_proportional_millionths as u64)
                                                                .map(|prop_fee| prop_fee / 1_000_000)
                                                                .and_then(|prop_fee| prop_fee.checked_add(
                                                                        update_opt.as_ref().unwrap().contents.fee_base_msat as u64))
                                                                .map(|fee_msats| route_hop.fee_msat >= fee_msats)
                                                                .unwrap_or(false),
                                                        13 => update_opt.is_ok() &&
                                                                route_hop.cltv_expiry_delta as u16 >=
                                                                        update_opt.as_ref().unwrap().contents.cltv_expiry_delta,
                                                        14 => false, // expiry_too_soon; always valid?
                                                        20 => update_opt.as_ref().unwrap().contents.flags & 2 == 0,
                                                        _ => false, // unknown error code; take channel_update as valid
                                                };
                                                if is_chan_update_invalid {
                                                        // This probably indicates the node which forwarded
                                                        // to the node in question corrupted something.
                                                        network_update = Some(NetworkUpdate::ChannelFailure {
                                                                short_channel_id: route_hop.short_channel_id,
                                                                is_permanent: true,
                                                        });
                                                } else {
                                                        if let Ok(chan_update) = update_opt {
                                                                // Make sure the ChannelUpdate contains the expected
                                                                // short channel id.
                                                                if failing_route_hop.short_channel_id == chan_update.contents.short_channel_id {
                                                                        short_channel_id = Some(failing_route_hop.short_channel_id);
                                                                } else {
                                                                        log_info!(logger, "Node provided a channel_update for which it was not authoritative, ignoring.");
                                                                }
                                                                network_update = Some(NetworkUpdate::ChannelUpdateMessage {
                                                                        msg: chan_update,
                                                                })
                                                        } else {
                                                                // The node in question intentionally encoded a 0-length channel update. This is
                                                                // likely due to https://github.com/ElementsProject/lightning/issues/6200.
                                                                network_update = Some(NetworkUpdate::ChannelFailure {
                                                                        short_channel_id: route_hop.short_channel_id,
                                                                        is_permanent: false,
                                                                });
                                                        }
                                                };
                                        } else {
                                                // If the channel_update had a non-zero length (i.e. was
                                                // present) but we couldn't read it, treat it as a total
                                                // node failure.
                                                log_info!(logger,
                                                        "Failed to read a channel_update of len {} in an onion",
                                                        update_slice.len());
                                        }
                                }
                        }
                        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
                });

                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);
                }
        }).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
        }) = res {
                DecodedOnionFailure {
                        network_update, short_channel_id, payment_retryable: !payment_failed_permanently,
                        #[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_retryable: !is_from_final_node,
                        #[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
pub(super) struct HTLCFailReason(HTLCFailReasonRepr);

#[derive(Clone)] // See Channel::revoke_and_ack for why, tl;dr: Rust bug
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 {
        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_retryable: true,
                                                short_channel_id: Some(path.hops[0].short_channel_id),
                                                #[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],
        },
}

/// 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,
        node_signer: &NS,
) -> Result<Hop, OnionDecodeErr> where NS::Target: NodeSigner {
        match decode_next_hop(shared_secret, hop_data, hmac_bytes, Some(payment_hash), 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),
        }
}

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).into_inner(), &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 {
                                msgs::DecodeError::UnknownVersion => 0x4000 | 1, // unknown realm byte
                                msgs::DecodeError::UnknownRequiredFeature|
                                msgs::DecodeError::InvalidValue|
                                msgs::DecodeError::ShortRead => 0x4000 | 22, // invalid_onion_payload
                                _ => 0x2000 | 2, // Should never happen
                        };
                        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)]
                                {
                                        // 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::prelude::*;
        use crate::ln::PaymentHash;
        use crate::ln::features::{ChannelFeatures, NodeFeatures};
        use crate::routing::router::{Path, Route, RouteHop};
        use crate::ln::msgs;
        use crate::util::ser::{Writeable, Writer, VecWriter};

        use hex;

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

        use super::OnionKeys;

        fn get_test_session_key() -> SecretKey {
                SecretKey::from_slice(&hex::decode("4141414141414141414141414141414141414141414141414141414141414141").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(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
                                                channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
                                                short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0 // We fill in the payloads manually instead of generating them from RouteHops.
                                        },
                                        RouteHop {
                                                pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
                                                channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
                                                short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0 // We fill in the payloads manually instead of generating them from RouteHops.
                                        },
                                        RouteHop {
                                                pubkey: PublicKey::from_slice(&hex::decode("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007").unwrap()[..]).unwrap(),
                                                channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
                                                short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0 // We fill in the payloads manually instead of generating them from RouteHops.
                                        },
                                        RouteHop {
                                                pubkey: PublicKey::from_slice(&hex::decode("032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991").unwrap()[..]).unwrap(),
                                                channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
                                                short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0 // We fill in the payloads manually instead of generating them from RouteHops.
                                        },
                                        RouteHop {
                                                pubkey: PublicKey::from_slice(&hex::decode("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145").unwrap()[..]).unwrap(),
                                                channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
                                                short_channel_id: 0, fee_msat: 0, cltv_expiry_delta: 0 // 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.
                assert_eq!(onion_keys[0].shared_secret.secret_bytes(), hex::decode("53eb63ea8a3fec3b3cd433b85cd62a4b145e1dda09391b348c4e1cd36a03ea66").unwrap()[..]);
                assert_eq!(onion_keys[0].blinding_factor[..], hex::decode("2ec2e5da605776054187180343287683aa6a51b4b1c04d6dd49c45d8cffb3c36").unwrap()[..]);
                assert_eq!(onion_keys[0].ephemeral_pubkey.serialize()[..], hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]);
                assert_eq!(onion_keys[0].rho, hex::decode("ce496ec94def95aadd4bec15cdb41a740c9f2b62347c4917325fcc6fb0453986").unwrap()[..]);
                assert_eq!(onion_keys[0].mu, hex::decode("b57061dc6d0a2b9f261ac410c8b26d64ac5506cbba30267a649c28c179400eba").unwrap()[..]);

                assert_eq!(onion_keys[1].shared_secret.secret_bytes(), hex::decode("a6519e98832a0b179f62123b3567c106db99ee37bef036e783263602f3488fae").unwrap()[..]);
                assert_eq!(onion_keys[1].blinding_factor[..], hex::decode("bf66c28bc22e598cfd574a1931a2bafbca09163df2261e6d0056b2610dab938f").unwrap()[..]);
                assert_eq!(onion_keys[1].ephemeral_pubkey.serialize()[..], hex::decode("028f9438bfbf7feac2e108d677e3a82da596be706cc1cf342b75c7b7e22bf4e6e2").unwrap()[..]);
                assert_eq!(onion_keys[1].rho, hex::decode("450ffcabc6449094918ebe13d4f03e433d20a3d28a768203337bc40b6e4b2c59").unwrap()[..]);
                assert_eq!(onion_keys[1].mu, hex::decode("05ed2b4a3fb023c2ff5dd6ed4b9b6ea7383f5cfe9d59c11d121ec2c81ca2eea9").unwrap()[..]);

                assert_eq!(onion_keys[2].shared_secret.secret_bytes(), hex::decode("3a6b412548762f0dbccce5c7ae7bb8147d1caf9b5471c34120b30bc9c04891cc").unwrap()[..]);
                assert_eq!(onion_keys[2].blinding_factor[..], hex::decode("a1f2dadd184eb1627049673f18c6325814384facdee5bfd935d9cb031a1698a5").unwrap()[..]);
                assert_eq!(onion_keys[2].ephemeral_pubkey.serialize()[..], hex::decode("03bfd8225241ea71cd0843db7709f4c222f62ff2d4516fd38b39914ab6b83e0da0").unwrap()[..]);
                assert_eq!(onion_keys[2].rho, hex::decode("11bf5c4f960239cb37833936aa3d02cea82c0f39fd35f566109c41f9eac8deea").unwrap()[..]);
                assert_eq!(onion_keys[2].mu, hex::decode("caafe2820fa00eb2eeb78695ae452eba38f5a53ed6d53518c5c6edf76f3f5b78").unwrap()[..]);

                assert_eq!(onion_keys[3].shared_secret.secret_bytes(), hex::decode("21e13c2d7cfe7e18836df50872466117a295783ab8aab0e7ecc8c725503ad02d").unwrap()[..]);
                assert_eq!(onion_keys[3].blinding_factor[..], hex::decode("7cfe0b699f35525029ae0fa437c69d0f20f7ed4e3916133f9cacbb13c82ff262").unwrap()[..]);
                assert_eq!(onion_keys[3].ephemeral_pubkey.serialize()[..], hex::decode("031dde6926381289671300239ea8e57ffaf9bebd05b9a5b95beaf07af05cd43595").unwrap()[..]);
                assert_eq!(onion_keys[3].rho, hex::decode("cbe784ab745c13ff5cffc2fbe3e84424aa0fd669b8ead4ee562901a4a4e89e9e").unwrap()[..]);
                assert_eq!(onion_keys[3].mu, hex::decode("5052aa1b3d9f0655a0932e50d42f0c9ba0705142c25d225515c45f47c0036ee9").unwrap()[..]);

                assert_eq!(onion_keys[4].shared_secret.secret_bytes(), hex::decode("b5756b9b542727dbafc6765a49488b023a725d631af688fc031217e90770c328").unwrap()[..]);
                assert_eq!(onion_keys[4].blinding_factor[..], hex::decode("c96e00dddaf57e7edcd4fb5954be5b65b09f17cb6d20651b4e90315be5779205").unwrap()[..]);
                assert_eq!(onion_keys[4].ephemeral_pubkey.serialize()[..], hex::decode("03a214ebd875aab6ddfd77f22c5e7311d7f77f17a169e599f157bbcdae8bf071f4").unwrap()[..]);
                assert_eq!(onion_keys[4].rho, hex::decode("034e18b8cc718e8af6339106e706c52d8df89e2b1f7e9142d996acf88df8799b").unwrap()[..]);
                assert_eq!(onion_keys[4].mu, hex::decode("8e45e5c61c2b24cb6382444db6698727afb063adecd72aada233d4bf273d975a").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: hex::decode("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: hex::decode("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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 expected_serialized_hop_1_payload = &hex::decode("1202023a98040205dc06080000000000000001").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 expected_serialized_hop_3_payload = &hex::decode("12020230d4040204e206080000000000000003").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 expected_serialized_hop_4_payload = &hex::decode("1202022710040203e806080000000000000004").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();

                assert_eq!(packet.encode(), hex::decode("0002EEC7245D6B7D2CCB30380BFBE2A3648CD7A942653F5AA340EDCEA1F283686619F7F3416A5AA36DC7EEB3EC6D421E9615471AB870A33AC07FA5D5A51DF0A8823AABE3FEA3F90D387529D4F72837F9E687230371CCD8D263072206DBED0234F6505E21E282ABD8C0E4F5B9FF8042800BBAB065036EADD0149B37F27DDE664725A49866E052E809D2B0198AB9610FAA656BBF4EC516763A59F8F42C171B179166BA38958D4F51B39B3E98706E2D14A2DAFD6A5DF808093ABFCA5AEAACA16EDED5DB7D21FB0294DD1A163EDF0FB445D5C8D7D688D6DD9C541762BF5A5123BF9939D957FE648416E88F1B0928BFA034982B22548E1A4D922690EECF546275AFB233ACF4323974680779F1A964CFE687456035CC0FBA8A5428430B390F0057B6D1FE9A8875BFA89693EEB838CE59F09D207A503EE6F6299C92D6361BC335FCBF9B5CD44747AADCE2CE6069CFDC3D671DAEF9F8AE590CF93D957C9E873E9A1BC62D9640DC8FC39C14902D49A1C80239B6C5B7FD91D05878CBF5FFC7DB2569F47C43D6C0D27C438ABFF276E87364DEB8858A37E5A62C446AF95D8B786EAF0B5FCF78D98B41496794F8DCAAC4EEF34B2ACFB94C7E8C32A9E9866A8FA0B6F2A06F00A1CCDE569F97EEC05C803BA7500ACC96691D8898D73D8E6A47B8F43C3D5DE74458D20EDA61474C426359677001FBD75A74D7D5DB6CB4FEB83122F133206203E4E2D293F838BF8C8B3A29ACB321315100B87E80E0EDB272EE80FDA944E3FB6084ED4D7F7C7D21C69D9DA43D31A90B70693F9B0CC3EAC74C11AB8FF655905688916CFA4EF0BD04135F2E50B7C689A21D04E8E981E74C6058188B9B1F9DFC3EEC6838E9FFBCF22CE738D8A177C19318DFFEF090CEE67E12DE1A3E2A39F61247547BA5257489CBC11D7D91ED34617FCC42F7A9DA2E3CF31A94A210A1018143173913C38F60E62B24BF0D7518F38B5BAB3E6A1F8AEB35E31D6442C8ABB5178EFC892D2E787D79C6AD9E2FC271792983FA9955AC4D1D84A36C024071BC6E431B625519D556AF38185601F70E29035EA6A09C8B676C9D88CF7E05E0F17098B584C4168735940263F940033A220F40BE4C85344128B14BEB9E75696DB37014107801A59B13E89CD9D2258C169D523BE6D31552C44C82FF4BB18EC9F099F3BF0E5B1BB2BA9A87D7E26F98D294927B600B5529C47E04D98956677CBCEE8FA2B60F49776D8B8C367465B7C626DA53700684FB6C918EAD0EAB8360E4F60EDD25B4F43816A75ECF70F909301825B512469F8389D79402311D8AECB7B3EF8599E79485A4388D87744D899F7C47EE644361E17040A7958C8911BE6F463AB6A9B2AFACD688EC55EF517B38F1339EFC54487232798BB25522FF4572FF68567FE830F92F7B8113EFCE3E98C3FFFBAEDCE4FD8B50E41DA97C0C08E423A72689CC68E68F752A5E3A9003E64E35C957CA2E1C48BB6F64B05F56B70B575AD2F278D57850A7AD568C24A4D32A3D74B29F03DC125488BC7C637DA582357F40B0A52D16B3B40BB2C2315D03360BC24209E20972C200566BCF3BBE5C5B0AEDD83132A8A4D5B4242BA370B6D67D9B67EB01052D132C7866B9CB502E44796D9D356E4E3CB47CC527322CD24976FE7C9257A2864151A38E568EF7A79F10D6EF27CC04CE382347A2488B1F404FDBF407FE1CA1C9D0D5649E34800E25E18951C98CAE9F43555EEF65FEE1EA8F15828807366C3B612CD5753BF9FB8FCED08855F742CDDD6F765F74254F03186683D646E6F09AC2805586C7CF11998357CAFC5DF3F285329366F475130C928B2DCEBA4AA383758E7A9D20705C4BB9DB619E2992F608A1BA65DB254BB389468741D0502E2588AEB54390AC600C19AF5C8E61383FC1BEBE0029E4474051E4EF908828DB9CCA13277EF65DB3FD47CCC2179126AAEFB627719F421E20").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]);
                assert_eq!(onion_error.encode(), hex::decode("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").unwrap());

                let onion_packet_1 = super::encrypt_failure_packet(onion_keys[4].shared_secret.as_ref(), &onion_error.encode()[..]);
                assert_eq!(onion_packet_1.data, hex::decode("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").unwrap());

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

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

                let onion_packet_4 = super::encrypt_failure_packet(onion_keys[1].shared_secret.as_ref(), &onion_packet_3.data[..]);
                assert_eq!(onion_packet_4.data, hex::decode("aac3200c4968f56b21f53e5e374e3a2383ad2b1b6501bbcc45abc31e59b26881b7dfadbb56ec8dae8857add94e6702fb4c3a4de22e2e669e1ed926b04447fc73034bb730f4932acd62727b75348a648a1128744657ca6a4e713b9b646c3ca66cac02cdab44dd3439890ef3aaf61708714f7375349b8da541b2548d452d84de7084bb95b3ac2345201d624d31f4d52078aa0fa05a88b4e20202bd2b86ac5b52919ea305a8949de95e935eed0319cf3cf19ebea61d76ba92532497fcdc9411d06bcd4275094d0a4a3c5d3a945e43305a5a9256e333e1f64dbca5fcd4e03a39b9012d197506e06f29339dfee3331995b21615337ae060233d39befea925cc262873e0530408e6990f1cbd233a150ef7b004ff6166c70c68d9f8c853c1abca640b8660db2921").unwrap());

                let onion_packet_5 = super::encrypt_failure_packet(onion_keys[0].shared_secret.as_ref(), &onion_packet_4.data[..]);
                assert_eq!(onion_packet_5.data, hex::decode("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").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[..])
                }
        }
}