_ Git - rust-lightning/blob - lightning/src/ln/onion_payment.rs

   1 //! Utilities for channelmanager.rs
   2 //!
   3 //! Includes a public [`peel_payment_onion`] function for use by external projects or libraries.
   4
   5 use bitcoin::hashes::Hash;
   6 use bitcoin::hashes::sha256::Hash as Sha256;
   7 use bitcoin::secp256k1::{self, Secp256k1, PublicKey};
   8
   9 use crate::chain::channelmonitor::{HTLC_FAIL_BACK_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS};
  10 use crate::ln::PaymentHash;
  11 use crate::ln::channelmanager::{CLTV_FAR_FAR_AWAY, HTLCFailureMsg, MIN_CLTV_EXPIRY_DELTA, PendingHTLCInfo, PendingHTLCRouting};
  12 use crate::ln::msgs;
  13 use crate::ln::onion_utils;
  14 use crate::ln::onion_utils::{HTLCFailReason, INVALID_ONION_BLINDING};
  15 use crate::sign::{NodeSigner, Recipient};
  16 use crate::util::logger::Logger;
  17
  18 use crate::prelude::*;
  19 use core::ops::Deref;
  20
  21 /// Invalid inbound onion payment.
  22 pub struct InboundOnionErr {
  23         /// BOLT 4 error code.
  24         pub err_code: u16,
  25         /// Data attached to this error.
  26         pub err_data: Vec<u8>,
  27         /// Error message text.
  28         pub msg: &'static str,
  29 }
  30
  31 pub(super) fn create_fwd_pending_htlc_info(
  32         msg: &msgs::UpdateAddHTLC, hop_data: msgs::InboundOnionPayload, hop_hmac: [u8; 32],
  33         new_packet_bytes: [u8; onion_utils::ONION_DATA_LEN], shared_secret: [u8; 32],
  34         next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
  35 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
  36         debug_assert!(next_packet_pubkey_opt.is_some());
  37         let outgoing_packet = msgs::OnionPacket {
  38                 version: 0,
  39                 public_key: next_packet_pubkey_opt.unwrap_or(Err(secp256k1::Error::InvalidPublicKey)),
  40                 hop_data: new_packet_bytes,
  41                 hmac: hop_hmac,
  42         };
  43
  44         let (short_channel_id, amt_to_forward, outgoing_cltv_value) = match hop_data {
  45                 msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
  46                         (short_channel_id, amt_to_forward, outgoing_cltv_value),
  47                 msgs::InboundOnionPayload::BlindedForward { .. } => todo!(),
  48                 msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
  49                         return Err(InboundOnionErr {
  50                                 msg: "Final Node OnionHopData provided for us as an intermediary node",
  51                                 err_code: 0x4000 | 22,
  52                                 err_data: Vec::new(),
  53                         }),
  54         };
  55
  56         Ok(PendingHTLCInfo {
  57                 routing: PendingHTLCRouting::Forward {
  58                         onion_packet: outgoing_packet,
  59                         short_channel_id,
  60                         blinded: None,
  61                 },
  62                 payment_hash: msg.payment_hash,
  63                 incoming_shared_secret: shared_secret,
  64                 incoming_amt_msat: Some(msg.amount_msat),
  65                 outgoing_amt_msat: amt_to_forward,
  66                 outgoing_cltv_value,
  67                 skimmed_fee_msat: None,
  68         })
  69 }
  70
  71 pub(super) fn create_recv_pending_htlc_info(
  72         hop_data: msgs::InboundOnionPayload, shared_secret: [u8; 32], payment_hash: PaymentHash,
  73         amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
  74         counterparty_skimmed_fee_msat: Option<u64>, current_height: u32, accept_mpp_keysend: bool,
  75 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
  76         let (payment_data, keysend_preimage, custom_tlvs, onion_amt_msat, outgoing_cltv_value, payment_metadata) = match hop_data {
  77                 msgs::InboundOnionPayload::Receive {
  78                         payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata, ..
  79                 } =>
  80                         (payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata),
  81                 msgs::InboundOnionPayload::BlindedReceive {
  82                         amt_msat, total_msat, outgoing_cltv_value, payment_secret, ..
  83                 } => {
  84                         let payment_data = msgs::FinalOnionHopData { payment_secret, total_msat };
  85                         (Some(payment_data), None, Vec::new(), amt_msat, outgoing_cltv_value, None)
  86                 }
  87                 msgs::InboundOnionPayload::Forward { .. } => {
  88                         return Err(InboundOnionErr {
  89                                 err_code: 0x4000|22,
  90                                 err_data: Vec::new(),
  91                                 msg: "Got non final data with an HMAC of 0",
  92                         })
  93                 },
  94                 msgs::InboundOnionPayload::BlindedForward { .. } => {
  95                         return Err(InboundOnionErr {
  96                                 err_code: INVALID_ONION_BLINDING,
  97                                 err_data: vec![0; 32],
  98                                 msg: "Got blinded non final data with an HMAC of 0",
  99                         })
 100                 }
 101         };
 102         // final_incorrect_cltv_expiry
 103         if outgoing_cltv_value > cltv_expiry {
 104                 return Err(InboundOnionErr {
 105                         msg: "Upstream node set CLTV to less than the CLTV set by the sender",
 106                         err_code: 18,
 107                         err_data: cltv_expiry.to_be_bytes().to_vec()
 108                 })
 109         }
 110         // final_expiry_too_soon
 111         // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
 112         // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
 113         //
 114         // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
 115         // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
 116         // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
 117         if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
 118                 let mut err_data = Vec::with_capacity(12);
 119                 err_data.extend_from_slice(&amt_msat.to_be_bytes());
 120                 err_data.extend_from_slice(&current_height.to_be_bytes());
 121                 return Err(InboundOnionErr {
 122                         err_code: 0x4000 | 15, err_data,
 123                         msg: "The final CLTV expiry is too soon to handle",
 124                 });
 125         }
 126         if (!allow_underpay && onion_amt_msat > amt_msat) ||
 127                 (allow_underpay && onion_amt_msat >
 128                  amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
 129         {
 130                 return Err(InboundOnionErr {
 131                         err_code: 19,
 132                         err_data: amt_msat.to_be_bytes().to_vec(),
 133                         msg: "Upstream node sent less than we were supposed to receive in payment",
 134                 });
 135         }
 136
 137         let routing = if let Some(payment_preimage) = keysend_preimage {
 138                 // We need to check that the sender knows the keysend preimage before processing this
 139                 // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
 140                 // could discover the final destination of X, by probing the adjacent nodes on the route
 141                 // with a keysend payment of identical payment hash to X and observing the processing
 142                 // time discrepancies due to a hash collision with X.
 143                 let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).to_byte_array());
 144                 if hashed_preimage != payment_hash {
 145                         return Err(InboundOnionErr {
 146                                 err_code: 0x4000|22,
 147                                 err_data: Vec::new(),
 148                                 msg: "Payment preimage didn't match payment hash",
 149                         });
 150                 }
 151                 if !accept_mpp_keysend && payment_data.is_some() {
 152                         return Err(InboundOnionErr {
 153                                 err_code: 0x4000|22,
 154                                 err_data: Vec::new(),
 155                                 msg: "We don't support MPP keysend payments",
 156                         });
 157                 }
 158                 PendingHTLCRouting::ReceiveKeysend {
 159                         payment_data,
 160                         payment_preimage,
 161                         payment_metadata,
 162                         incoming_cltv_expiry: outgoing_cltv_value,
 163                         custom_tlvs,
 164                 }
 165         } else if let Some(data) = payment_data {
 166                 PendingHTLCRouting::Receive {
 167                         payment_data: data,
 168                         payment_metadata,
 169                         incoming_cltv_expiry: outgoing_cltv_value,
 170                         phantom_shared_secret,
 171                         custom_tlvs,
 172                 }
 173         } else {
 174                 return Err(InboundOnionErr {
 175                         err_code: 0x4000|0x2000|3,
 176                         err_data: Vec::new(),
 177                         msg: "We require payment_secrets",
 178                 });
 179         };
 180         Ok(PendingHTLCInfo {
 181                 routing,
 182                 payment_hash,
 183                 incoming_shared_secret: shared_secret,
 184                 incoming_amt_msat: Some(amt_msat),
 185                 outgoing_amt_msat: onion_amt_msat,
 186                 outgoing_cltv_value,
 187                 skimmed_fee_msat: counterparty_skimmed_fee_msat,
 188         })
 189 }
 190
 191 /// Peel one layer off an incoming onion, returning [`PendingHTLCInfo`] (either Forward or Receive).
 192 /// This does all the relevant context-free checks that LDK requires for payment relay or
 193 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
 194 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
 195 /// channel, will generate an [`Event::PaymentClaimable`].
 196 ///
 197 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
 198 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 199         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 200         cur_height: u32, accept_mpp_keysend: bool,
 201 ) -> Result<PendingHTLCInfo, InboundOnionErr>
 202 where
 203         NS::Target: NodeSigner,
 204         L::Target: Logger,
 205 {
 206         let (hop, shared_secret, next_packet_details_opt) =
 207                 decode_incoming_update_add_htlc_onion(msg, node_signer, logger, secp_ctx
 208         ).map_err(|e| {
 209                 let (err_code, err_data) = match e {
 210                         HTLCFailureMsg::Malformed(m) => (m.failure_code, Vec::new()),
 211                         HTLCFailureMsg::Relay(r) => (0x4000 | 22, r.reason.data),
 212                 };
 213                 let msg = "Failed to decode update add htlc onion";
 214                 InboundOnionErr { msg, err_code, err_data }
 215         })?;
 216         Ok(match hop {
 217                 onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
 218                         let NextPacketDetails {
 219                                 next_packet_pubkey, outgoing_amt_msat: _, outgoing_scid: _, outgoing_cltv_value
 220                         } = match next_packet_details_opt {
 221                                 Some(next_packet_details) => next_packet_details,
 222                                 // Forward should always include the next hop details
 223                                 None => return Err(InboundOnionErr {
 224                                         msg: "Failed to decode update add htlc onion",
 225                                         err_code: 0x4000 | 22,
 226                                         err_data: Vec::new(),
 227                                 }),
 228                         };
 229
 230                         if let Err((err_msg, code)) = check_incoming_htlc_cltv(
 231                                 cur_height, outgoing_cltv_value, msg.cltv_expiry
 232                         ) {
 233                                 return Err(InboundOnionErr {
 234                                         msg: err_msg,
 235                                         err_code: code,
 236                                         err_data: Vec::new(),
 237                                 });
 238                         }
 239                         create_fwd_pending_htlc_info(
 240                                 msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
 241                                 Some(next_packet_pubkey)
 242                         )?
 243                 },
 244                 onion_utils::Hop::Receive(received_data) => {
 245                         create_recv_pending_htlc_info(
 246                                 received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
 247                                 None, false, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
 248                         )?
 249                 }
 250         })
 251 }
 252
 253 pub(super) struct NextPacketDetails {
 254         pub(super) next_packet_pubkey: Result<PublicKey, secp256k1::Error>,
 255         pub(super) outgoing_scid: u64,
 256         pub(super) outgoing_amt_msat: u64,
 257         pub(super) outgoing_cltv_value: u32,
 258 }
 259
 260 pub(super) fn decode_incoming_update_add_htlc_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 261         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 262 ) -> Result<(onion_utils::Hop, [u8; 32], Option<NextPacketDetails>), HTLCFailureMsg>
 263 where
 264         NS::Target: NodeSigner,
 265         L::Target: Logger,
 266 {
 267         macro_rules! return_malformed_err {
 268                 ($msg: expr, $err_code: expr) => {
 269                         {
 270                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 271                                 return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
 272                                         channel_id: msg.channel_id,
 273                                         htlc_id: msg.htlc_id,
 274                                         sha256_of_onion: Sha256::hash(&msg.onion_routing_packet.hop_data).to_byte_array(),
 275                                         failure_code: $err_code,
 276                                 }));
 277                         }
 278                 }
 279         }
 280
 281         if let Err(_) = msg.onion_routing_packet.public_key {
 282                 return_malformed_err!("invalid ephemeral pubkey", 0x8000 | 0x4000 | 6);
 283         }
 284
 285         let shared_secret = node_signer.ecdh(
 286                 Recipient::Node, &msg.onion_routing_packet.public_key.unwrap(), None
 287         ).unwrap().secret_bytes();
 288
 289         if msg.onion_routing_packet.version != 0 {
 290                 //TODO: Spec doesn't indicate if we should only hash hop_data here (and in other
 291                 //sha256_of_onion error data packets), or the entire onion_routing_packet. Either way,
 292                 //the hash doesn't really serve any purpose - in the case of hashing all data, the
 293                 //receiving node would have to brute force to figure out which version was put in the
 294                 //packet by the node that send us the message, in the case of hashing the hop_data, the
 295                 //node knows the HMAC matched, so they already know what is there...
 296                 return_malformed_err!("Unknown onion packet version", 0x8000 | 0x4000 | 4);
 297         }
 298         macro_rules! return_err {
 299                 ($msg: expr, $err_code: expr, $data: expr) => {
 300                         {
 301                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 302                                 return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
 303                                         channel_id: msg.channel_id,
 304                                         htlc_id: msg.htlc_id,
 305                                         reason: HTLCFailReason::reason($err_code, $data.to_vec())
 306                                                 .get_encrypted_failure_packet(&shared_secret, &None),
 307                                 }));
 308                         }
 309                 }
 310         }
 311
 312         let next_hop = match onion_utils::decode_next_payment_hop(
 313                 shared_secret, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 314                 msg.payment_hash, node_signer
 315         ) {
 316                 Ok(res) => res,
 317                 Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
 318                         return_malformed_err!(err_msg, err_code);
 319                 },
 320                 Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
 321                         return_err!(err_msg, err_code, &[0; 0]);
 322                 },
 323         };
 324
 325         let next_packet_details = match next_hop {
 326                 onion_utils::Hop::Forward {
 327                         next_hop_data: msgs::InboundOnionPayload::Forward {
 328                                 short_channel_id, amt_to_forward, outgoing_cltv_value
 329                         }, ..
 330                 } => {
 331                         let next_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
 332                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 333                         NextPacketDetails {
 334                                 next_packet_pubkey, outgoing_scid: short_channel_id,
 335                                 outgoing_amt_msat: amt_to_forward, outgoing_cltv_value
 336                         }
 337                 },
 338                 onion_utils::Hop::Forward {
 339                         next_hop_data: msgs::InboundOnionPayload::BlindedForward { .. }, ..
 340                 } => {
 341                         todo!()
 342                 },
 343                 onion_utils::Hop::Receive { .. } => return Ok((next_hop, shared_secret, None)),
 344                 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::Receive { .. }, .. } |
 345                         onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::BlindedReceive { .. }, .. } =>
 346                 {
 347                         return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0; 0]);
 348                 }
 349         };
 350
 351         Ok((next_hop, shared_secret, Some(next_packet_details)))
 352 }
 353
 354 pub(super) fn check_incoming_htlc_cltv(
 355         cur_height: u32, outgoing_cltv_value: u32, cltv_expiry: u32
 356 ) -> Result<(), (&'static str, u16)> {
 357         if (cltv_expiry as u64) < (outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
 358                 return Err((
 359                         "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
 360                         0x1000 | 13, // incorrect_cltv_expiry
 361                 ));
 362         }
 363         // Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
 364         // but we want to be robust wrt to counterparty packet sanitization (see
 365         // HTLC_FAIL_BACK_BUFFER rationale).
 366         if cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
 367                 return Err(("CLTV expiry is too close", 0x1000 | 14));
 368         }
 369         if cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
 370                 return Err(("CLTV expiry is too far in the future", 21));
 371         }
 372         // If the HTLC expires ~now, don't bother trying to forward it to our
 373         // counterparty. They should fail it anyway, but we don't want to bother with
 374         // the round-trips or risk them deciding they definitely want the HTLC and
 375         // force-closing to ensure they get it if we're offline.
 376         // We previously had a much more aggressive check here which tried to ensure
 377         // our counterparty receives an HTLC which has *our* risk threshold met on it,
 378         // but there is no need to do that, and since we're a bit conservative with our
 379         // risk threshold it just results in failing to forward payments.
 380         if (outgoing_cltv_value) as u64 <= (cur_height + LATENCY_GRACE_PERIOD_BLOCKS) as u64 {
 381                 return Err(("Outgoing CLTV value is too soon", 0x1000 | 14));
 382         }
 383
 384         Ok(())
 385 }
 386
 387 #[cfg(test)]
 388 mod tests {
 389         use bitcoin::hashes::Hash;
 390         use bitcoin::hashes::sha256::Hash as Sha256;
 391         use bitcoin::secp256k1::{PublicKey, SecretKey};
 392         use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 393         use crate::ln::ChannelId;
 394         use crate::ln::channelmanager::RecipientOnionFields;
 395         use crate::ln::features::{ChannelFeatures, NodeFeatures};
 396         use crate::ln::msgs;
 397         use crate::ln::onion_utils::create_payment_onion;
 398         use crate::routing::router::{Path, RouteHop};
 399         use crate::util::test_utils;
 400
 401         #[test]
 402         fn test_peel_payment_onion() {
 403                 use super::*;
 404                 let secp_ctx = Secp256k1::new();
 405
 406                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 407                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 408                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 409                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 410
 411                 let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 412                         prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
 413
 414                 let path = Path {
 415                         hops: hops,
 416                         blinded_tail: None,
 417                 };
 418
 419                 let (onion, amount_msat, cltv_expiry) = create_payment_onion(
 420                         &secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
 421                         &payment_hash, &Some(preimage), prng_seed
 422                 ).unwrap();
 423
 424                 let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
 425                 let logger = test_utils::TestLogger::with_id("bob".to_string());
 426
 427                 let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true)
 428                         .map_err(|e| e.msg).unwrap();
 429
 430                 let next_onion = match peeled.routing {
 431                         PendingHTLCRouting::Forward { onion_packet, .. } => {
 432                                 onion_packet
 433                         },
 434                         _ => panic!("expected a forwarded onion"),
 435                 };
 436
 437                 let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
 438                 let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true)
 439                         .map_err(|e| e.msg).unwrap();
 440
 441                 match peeled2.routing {
 442                         PendingHTLCRouting::ReceiveKeysend { payment_preimage, payment_data, incoming_cltv_expiry, .. } => {
 443                                 assert_eq!(payment_preimage, preimage);
 444                                 assert_eq!(peeled2.outgoing_amt_msat, recipient_amount);
 445                                 assert_eq!(incoming_cltv_expiry, peeled2.outgoing_cltv_value);
 446                                 let msgs::FinalOnionHopData{total_msat, payment_secret} = payment_data.unwrap();
 447                                 assert_eq!(total_msat, total_amt_msat);
 448                                 assert_eq!(payment_secret, pay_secret);
 449                         },
 450                         _ => panic!("expected a received keysend"),
 451                 };
 452         }
 453
 454         fn make_update_add_msg(
 455                 amount_msat: u64, cltv_expiry: u32, payment_hash: PaymentHash,
 456                 onion_routing_packet: msgs::OnionPacket
 457         ) -> msgs::UpdateAddHTLC {
 458                 msgs::UpdateAddHTLC {
 459                         channel_id: ChannelId::from_bytes([0; 32]),
 460                         htlc_id: 0,
 461                         amount_msat,
 462                         cltv_expiry,
 463                         payment_hash,
 464                         onion_routing_packet,
 465                         skimmed_fee_msat: None,
 466                         blinding_point: None,
 467                 }
 468         }
 469
 470         fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
 471                 SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
 472                 Vec<RouteHop>, u64, PaymentSecret,
 473         ) {
 474                 let session_priv_bytes = [42; 32];
 475                 let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
 476                 let total_amt_msat = 1000;
 477                 let cur_height = 1000;
 478                 let pay_secret = PaymentSecret([99; 32]);
 479                 let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
 480                 let preimage_bytes = [43; 32];
 481                 let preimage = PaymentPreimage(preimage_bytes);
 482                 let rhash_bytes = Sha256::hash(&preimage_bytes).to_byte_array();
 483                 let payment_hash = PaymentHash(rhash_bytes);
 484                 let prng_seed = [44; 32];
 485
 486                 // make a route alice -> bob -> charlie
 487                 let hop_fee = 1;
 488                 let recipient_amount = total_amt_msat - hop_fee;
 489                 let hops = vec![
 490                         RouteHop {
 491                                 pubkey: hop_pk,
 492                                 fee_msat: hop_fee,
 493                                 cltv_expiry_delta: 42,
 494                                 short_channel_id: 1,
 495                                 node_features: NodeFeatures::empty(),
 496                                 channel_features: ChannelFeatures::empty(),
 497                                 maybe_announced_channel: false,
 498                         },
 499                         RouteHop {
 500                                 pubkey: recipient_pk,
 501                                 fee_msat: recipient_amount,
 502                                 cltv_expiry_delta: 42,
 503                                 short_channel_id: 2,
 504                                 node_features: NodeFeatures::empty(),
 505                                 channel_features: ChannelFeatures::empty(),
 506                                 maybe_announced_channel: false,
 507                         }
 508                 ];
 509
 510                 (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 511                         prng_seed, hops, recipient_amount, pay_secret)
 512         }
 513
 514 }