git.bitcoin.ninja Git - rust-lightning/blob - lightning/src/ln/onion_payment.rs

   1 //! Utilities to decode payment onions and do contextless validation of incoming payments.
   2 //!
   3 //! Primarily features [`peel_payment_onion`], which allows the decoding of an onion statelessly
   4 //! and can be used to predict whether we'd accept a payment.
   5
   6 use bitcoin::hashes::{Hash, HashEngine};
   7 use bitcoin::hashes::hmac::{Hmac, HmacEngine};
   8 use bitcoin::hashes::sha256::Hash as Sha256;
   9 use bitcoin::secp256k1::{self, PublicKey, Scalar, Secp256k1};
  10
  11 use crate::blinded_path;
  12 use crate::blinded_path::payment::{PaymentConstraints, PaymentRelay};
  13 use crate::chain::channelmonitor::{HTLC_FAIL_BACK_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS};
  14 use crate::ln::PaymentHash;
  15 use crate::ln::channelmanager::{BlindedForward, CLTV_FAR_FAR_AWAY, HTLCFailureMsg, MIN_CLTV_EXPIRY_DELTA, PendingHTLCInfo, PendingHTLCRouting};
  16 use crate::ln::features::BlindedHopFeatures;
  17 use crate::ln::msgs;
  18 use crate::ln::onion_utils;
  19 use crate::ln::onion_utils::{HTLCFailReason, INVALID_ONION_BLINDING};
  20 use crate::sign::{NodeSigner, Recipient};
  21 use crate::util::logger::Logger;
  22
  23 use crate::prelude::*;
  24 use core::ops::Deref;
  25
  26 /// Invalid inbound onion payment.
  27 pub struct InboundOnionErr {
  28         /// BOLT 4 error code.
  29         pub err_code: u16,
  30         /// Data attached to this error.
  31         pub err_data: Vec<u8>,
  32         /// Error message text.
  33         pub msg: &'static str,
  34 }
  35
  36 fn check_blinded_payment_constraints(
  37         amt_msat: u64, cltv_expiry: u32, constraints: &PaymentConstraints
  38 ) -> Result<(), ()> {
  39         if amt_msat < constraints.htlc_minimum_msat ||
  40                 cltv_expiry > constraints.max_cltv_expiry
  41         { return Err(()) }
  42         Ok(())
  43 }
  44
  45 fn check_blinded_forward(
  46         inbound_amt_msat: u64, inbound_cltv_expiry: u32, payment_relay: &PaymentRelay,
  47         payment_constraints: &PaymentConstraints, features: &BlindedHopFeatures
  48 ) -> Result<(u64, u32), ()> {
  49         let amt_to_forward = blinded_path::payment::amt_to_forward_msat(
  50                 inbound_amt_msat, payment_relay
  51         ).ok_or(())?;
  52         let outgoing_cltv_value = inbound_cltv_expiry.checked_sub(
  53                 payment_relay.cltv_expiry_delta as u32
  54         ).ok_or(())?;
  55         check_blinded_payment_constraints(inbound_amt_msat, outgoing_cltv_value, payment_constraints)?;
  56
  57         if features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
  58         Ok((amt_to_forward, outgoing_cltv_value))
  59 }
  60
  61 pub(super) fn create_fwd_pending_htlc_info(
  62         msg: &msgs::UpdateAddHTLC, hop_data: msgs::InboundOnionPayload, hop_hmac: [u8; 32],
  63         new_packet_bytes: [u8; onion_utils::ONION_DATA_LEN], shared_secret: [u8; 32],
  64         next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
  65 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
  66         debug_assert!(next_packet_pubkey_opt.is_some());
  67         let outgoing_packet = msgs::OnionPacket {
  68                 version: 0,
  69                 public_key: next_packet_pubkey_opt.unwrap_or(Err(secp256k1::Error::InvalidPublicKey)),
  70                 hop_data: new_packet_bytes,
  71                 hmac: hop_hmac,
  72         };
  73
  74         let (
  75                 short_channel_id, amt_to_forward, outgoing_cltv_value, inbound_blinding_point
  76         ) = match hop_data {
  77                 msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
  78                         (short_channel_id, amt_to_forward, outgoing_cltv_value, None),
  79                 msgs::InboundOnionPayload::BlindedForward {
  80                         short_channel_id, payment_relay, payment_constraints, intro_node_blinding_point, features,
  81                 } => {
  82                         let (amt_to_forward, outgoing_cltv_value) = check_blinded_forward(
  83                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
  84                         ).map_err(|()| {
  85                                 // We should be returning malformed here if `msg.blinding_point` is set, but this is
  86                                 // unreachable right now since we checked it in `decode_update_add_htlc_onion`.
  87                                 InboundOnionErr {
  88                                         msg: "Underflow calculating outbound amount or cltv value for blinded forward",
  89                                         err_code: INVALID_ONION_BLINDING,
  90                                         err_data: vec![0; 32],
  91                                 }
  92                         })?;
  93                         (short_channel_id, amt_to_forward, outgoing_cltv_value, Some(intro_node_blinding_point))
  94                 },
  95                 msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
  96                         return Err(InboundOnionErr {
  97                                 msg: "Final Node OnionHopData provided for us as an intermediary node",
  98                                 err_code: 0x4000 | 22,
  99                                 err_data: Vec::new(),
 100                         }),
 101         };
 102
 103         Ok(PendingHTLCInfo {
 104                 routing: PendingHTLCRouting::Forward {
 105                         onion_packet: outgoing_packet,
 106                         short_channel_id,
 107                         blinded: inbound_blinding_point.map(|bp| BlindedForward { inbound_blinding_point: bp }),
 108                 },
 109                 payment_hash: msg.payment_hash,
 110                 incoming_shared_secret: shared_secret,
 111                 incoming_amt_msat: Some(msg.amount_msat),
 112                 outgoing_amt_msat: amt_to_forward,
 113                 outgoing_cltv_value,
 114                 skimmed_fee_msat: None,
 115         })
 116 }
 117
 118 pub(super) fn create_recv_pending_htlc_info(
 119         hop_data: msgs::InboundOnionPayload, shared_secret: [u8; 32], payment_hash: PaymentHash,
 120         amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
 121         counterparty_skimmed_fee_msat: Option<u64>, current_height: u32, accept_mpp_keysend: bool,
 122 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
 123         let (
 124                 payment_data, keysend_preimage, custom_tlvs, onion_amt_msat, outgoing_cltv_value,
 125                 payment_metadata, requires_blinded_error
 126         ) = match hop_data {
 127                 msgs::InboundOnionPayload::Receive {
 128                         payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata, ..
 129                 } =>
 130                         (payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata,
 131                          false),
 132                 msgs::InboundOnionPayload::BlindedReceive {
 133                         amt_msat, total_msat, outgoing_cltv_value, payment_secret, intro_node_blinding_point,
 134                         payment_constraints, ..
 135                 } => {
 136                         check_blinded_payment_constraints(amt_msat, cltv_expiry, &payment_constraints)
 137                                 .map_err(|()| {
 138                                         InboundOnionErr {
 139                                                 err_code: INVALID_ONION_BLINDING,
 140                                                 err_data: vec![0; 32],
 141                                                 msg: "Amount or cltv_expiry violated blinded payment constraints",
 142                                         }
 143                                 })?;
 144                         let payment_data = msgs::FinalOnionHopData { payment_secret, total_msat };
 145                         (Some(payment_data), None, Vec::new(), amt_msat, outgoing_cltv_value, None,
 146                          intro_node_blinding_point.is_none())
 147                 }
 148                 msgs::InboundOnionPayload::Forward { .. } => {
 149                         return Err(InboundOnionErr {
 150                                 err_code: 0x4000|22,
 151                                 err_data: Vec::new(),
 152                                 msg: "Got non final data with an HMAC of 0",
 153                         })
 154                 },
 155                 msgs::InboundOnionPayload::BlindedForward { .. } => {
 156                         return Err(InboundOnionErr {
 157                                 err_code: INVALID_ONION_BLINDING,
 158                                 err_data: vec![0; 32],
 159                                 msg: "Got blinded non final data with an HMAC of 0",
 160                         })
 161                 }
 162         };
 163         // final_incorrect_cltv_expiry
 164         if outgoing_cltv_value > cltv_expiry {
 165                 return Err(InboundOnionErr {
 166                         msg: "Upstream node set CLTV to less than the CLTV set by the sender",
 167                         err_code: 18,
 168                         err_data: cltv_expiry.to_be_bytes().to_vec()
 169                 })
 170         }
 171         // final_expiry_too_soon
 172         // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
 173         // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
 174         //
 175         // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
 176         // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
 177         // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
 178         if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
 179                 let mut err_data = Vec::with_capacity(12);
 180                 err_data.extend_from_slice(&amt_msat.to_be_bytes());
 181                 err_data.extend_from_slice(&current_height.to_be_bytes());
 182                 return Err(InboundOnionErr {
 183                         err_code: 0x4000 | 15, err_data,
 184                         msg: "The final CLTV expiry is too soon to handle",
 185                 });
 186         }
 187         if (!allow_underpay && onion_amt_msat > amt_msat) ||
 188                 (allow_underpay && onion_amt_msat >
 189                  amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
 190         {
 191                 return Err(InboundOnionErr {
 192                         err_code: 19,
 193                         err_data: amt_msat.to_be_bytes().to_vec(),
 194                         msg: "Upstream node sent less than we were supposed to receive in payment",
 195                 });
 196         }
 197
 198         let routing = if let Some(payment_preimage) = keysend_preimage {
 199                 // We need to check that the sender knows the keysend preimage before processing this
 200                 // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
 201                 // could discover the final destination of X, by probing the adjacent nodes on the route
 202                 // with a keysend payment of identical payment hash to X and observing the processing
 203                 // time discrepancies due to a hash collision with X.
 204                 let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).to_byte_array());
 205                 if hashed_preimage != payment_hash {
 206                         return Err(InboundOnionErr {
 207                                 err_code: 0x4000|22,
 208                                 err_data: Vec::new(),
 209                                 msg: "Payment preimage didn't match payment hash",
 210                         });
 211                 }
 212                 if !accept_mpp_keysend && payment_data.is_some() {
 213                         return Err(InboundOnionErr {
 214                                 err_code: 0x4000|22,
 215                                 err_data: Vec::new(),
 216                                 msg: "We don't support MPP keysend payments",
 217                         });
 218                 }
 219                 PendingHTLCRouting::ReceiveKeysend {
 220                         payment_data,
 221                         payment_preimage,
 222                         payment_metadata,
 223                         incoming_cltv_expiry: outgoing_cltv_value,
 224                         custom_tlvs,
 225                 }
 226         } else if let Some(data) = payment_data {
 227                 PendingHTLCRouting::Receive {
 228                         payment_data: data,
 229                         payment_metadata,
 230                         incoming_cltv_expiry: outgoing_cltv_value,
 231                         phantom_shared_secret,
 232                         custom_tlvs,
 233                         requires_blinded_error,
 234                 }
 235         } else {
 236                 return Err(InboundOnionErr {
 237                         err_code: 0x4000|0x2000|3,
 238                         err_data: Vec::new(),
 239                         msg: "We require payment_secrets",
 240                 });
 241         };
 242         Ok(PendingHTLCInfo {
 243                 routing,
 244                 payment_hash,
 245                 incoming_shared_secret: shared_secret,
 246                 incoming_amt_msat: Some(amt_msat),
 247                 outgoing_amt_msat: onion_amt_msat,
 248                 outgoing_cltv_value,
 249                 skimmed_fee_msat: counterparty_skimmed_fee_msat,
 250         })
 251 }
 252
 253 /// Peel one layer off an incoming onion, returning a [`PendingHTLCInfo`] that contains information
 254 /// about the intended next-hop for the HTLC.
 255 ///
 256 /// This does all the relevant context-free checks that LDK requires for payment relay or
 257 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
 258 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
 259 /// channel, will generate an [`Event::PaymentClaimable`].
 260 ///
 261 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
 262 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 263         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 264         cur_height: u32, accept_mpp_keysend: bool, allow_skimmed_fees: bool,
 265 ) -> Result<PendingHTLCInfo, InboundOnionErr>
 266 where
 267         NS::Target: NodeSigner,
 268         L::Target: Logger,
 269 {
 270         let (hop, shared_secret, next_packet_details_opt) =
 271                 decode_incoming_update_add_htlc_onion(msg, node_signer, logger, secp_ctx
 272         ).map_err(|e| {
 273                 let (err_code, err_data) = match e {
 274                         HTLCFailureMsg::Malformed(m) => (m.failure_code, Vec::new()),
 275                         HTLCFailureMsg::Relay(r) => (0x4000 | 22, r.reason.data),
 276                 };
 277                 let msg = "Failed to decode update add htlc onion";
 278                 InboundOnionErr { msg, err_code, err_data }
 279         })?;
 280         Ok(match hop {
 281                 onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
 282                         let NextPacketDetails {
 283                                 next_packet_pubkey, outgoing_amt_msat: _, outgoing_scid: _, outgoing_cltv_value
 284                         } = match next_packet_details_opt {
 285                                 Some(next_packet_details) => next_packet_details,
 286                                 // Forward should always include the next hop details
 287                                 None => return Err(InboundOnionErr {
 288                                         msg: "Failed to decode update add htlc onion",
 289                                         err_code: 0x4000 | 22,
 290                                         err_data: Vec::new(),
 291                                 }),
 292                         };
 293
 294                         if let Err((err_msg, code)) = check_incoming_htlc_cltv(
 295                                 cur_height, outgoing_cltv_value, msg.cltv_expiry
 296                         ) {
 297                                 return Err(InboundOnionErr {
 298                                         msg: err_msg,
 299                                         err_code: code,
 300                                         err_data: Vec::new(),
 301                                 });
 302                         }
 303
 304                         // TODO: If this is potentially a phantom payment we should decode the phantom payment
 305                         // onion here and check it.
 306
 307                         create_fwd_pending_htlc_info(
 308                                 msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
 309                                 Some(next_packet_pubkey)
 310                         )?
 311                 },
 312                 onion_utils::Hop::Receive(received_data) => {
 313                         create_recv_pending_htlc_info(
 314                                 received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
 315                                 None, allow_skimmed_fees, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
 316                         )?
 317                 }
 318         })
 319 }
 320
 321 pub(super) struct NextPacketDetails {
 322         pub(super) next_packet_pubkey: Result<PublicKey, secp256k1::Error>,
 323         pub(super) outgoing_scid: u64,
 324         pub(super) outgoing_amt_msat: u64,
 325         pub(super) outgoing_cltv_value: u32,
 326 }
 327
 328 pub(super) fn decode_incoming_update_add_htlc_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 329         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 330 ) -> Result<(onion_utils::Hop, [u8; 32], Option<NextPacketDetails>), HTLCFailureMsg>
 331 where
 332         NS::Target: NodeSigner,
 333         L::Target: Logger,
 334 {
 335         macro_rules! return_malformed_err {
 336                 ($msg: expr, $err_code: expr) => {
 337                         {
 338                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 339                                 let (sha256_of_onion, failure_code) = if msg.blinding_point.is_some() {
 340                                         ([0; 32], INVALID_ONION_BLINDING)
 341                                 } else {
 342                                         (Sha256::hash(&msg.onion_routing_packet.hop_data).to_byte_array(), $err_code)
 343                                 };
 344                                 return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
 345                                         channel_id: msg.channel_id,
 346                                         htlc_id: msg.htlc_id,
 347                                         sha256_of_onion,
 348                                         failure_code,
 349                                 }));
 350                         }
 351                 }
 352         }
 353
 354         if let Err(_) = msg.onion_routing_packet.public_key {
 355                 return_malformed_err!("invalid ephemeral pubkey", 0x8000 | 0x4000 | 6);
 356         }
 357
 358         let blinded_node_id_tweak = msg.blinding_point.map(|bp| {
 359                 let blinded_tlvs_ss = node_signer.ecdh(Recipient::Node, &bp, None).unwrap().secret_bytes();
 360                 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 361                 hmac.input(blinded_tlvs_ss.as_ref());
 362                 Scalar::from_be_bytes(Hmac::from_engine(hmac).to_byte_array()).unwrap()
 363         });
 364         let shared_secret = node_signer.ecdh(
 365                 Recipient::Node, &msg.onion_routing_packet.public_key.unwrap(), blinded_node_id_tweak.as_ref()
 366         ).unwrap().secret_bytes();
 367
 368         if msg.onion_routing_packet.version != 0 {
 369                 //TODO: Spec doesn't indicate if we should only hash hop_data here (and in other
 370                 //sha256_of_onion error data packets), or the entire onion_routing_packet. Either way,
 371                 //the hash doesn't really serve any purpose - in the case of hashing all data, the
 372                 //receiving node would have to brute force to figure out which version was put in the
 373                 //packet by the node that send us the message, in the case of hashing the hop_data, the
 374                 //node knows the HMAC matched, so they already know what is there...
 375                 return_malformed_err!("Unknown onion packet version", 0x8000 | 0x4000 | 4);
 376         }
 377         macro_rules! return_err {
 378                 ($msg: expr, $err_code: expr, $data: expr) => {
 379                         {
 380                                 if msg.blinding_point.is_some() {
 381                                         return_malformed_err!($msg, INVALID_ONION_BLINDING)
 382                                 }
 383
 384                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 385                                 return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
 386                                         channel_id: msg.channel_id,
 387                                         htlc_id: msg.htlc_id,
 388                                         reason: HTLCFailReason::reason($err_code, $data.to_vec())
 389                                                 .get_encrypted_failure_packet(&shared_secret, &None),
 390                                 }));
 391                         }
 392                 }
 393         }
 394
 395         let next_hop = match onion_utils::decode_next_payment_hop(
 396                 shared_secret, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 397                 msg.payment_hash, msg.blinding_point, node_signer
 398         ) {
 399                 Ok(res) => res,
 400                 Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
 401                         return_malformed_err!(err_msg, err_code);
 402                 },
 403                 Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
 404                         return_err!(err_msg, err_code, &[0; 0]);
 405                 },
 406         };
 407
 408         let next_packet_details = match next_hop {
 409                 onion_utils::Hop::Forward {
 410                         next_hop_data: msgs::InboundOnionPayload::Forward {
 411                                 short_channel_id, amt_to_forward, outgoing_cltv_value
 412                         }, ..
 413                 } => {
 414                         let next_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
 415                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 416                         NextPacketDetails {
 417                                 next_packet_pubkey, outgoing_scid: short_channel_id,
 418                                 outgoing_amt_msat: amt_to_forward, outgoing_cltv_value
 419                         }
 420                 },
 421                 onion_utils::Hop::Forward {
 422                         next_hop_data: msgs::InboundOnionPayload::BlindedForward {
 423                                 short_channel_id, ref payment_relay, ref payment_constraints, ref features, ..
 424                         }, ..
 425                 } => {
 426                         let (amt_to_forward, outgoing_cltv_value) = match check_blinded_forward(
 427                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
 428                         ) {
 429                                 Ok((amt, cltv)) => (amt, cltv),
 430                                 Err(()) => {
 431                                         return_err!("Underflow calculating outbound amount or cltv value for blinded forward",
 432                                                 INVALID_ONION_BLINDING, &[0; 32]);
 433                                 }
 434                         };
 435                         let next_packet_pubkey = onion_utils::next_hop_pubkey(&secp_ctx,
 436                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 437                         NextPacketDetails {
 438                                 next_packet_pubkey, outgoing_scid: short_channel_id, outgoing_amt_msat: amt_to_forward,
 439                                 outgoing_cltv_value
 440                         }
 441                 },
 442                 onion_utils::Hop::Receive { .. } => return Ok((next_hop, shared_secret, None)),
 443                 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::Receive { .. }, .. } |
 444                         onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::BlindedReceive { .. }, .. } =>
 445                 {
 446                         return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0; 0]);
 447                 }
 448         };
 449
 450         Ok((next_hop, shared_secret, Some(next_packet_details)))
 451 }
 452
 453 pub(super) fn check_incoming_htlc_cltv(
 454         cur_height: u32, outgoing_cltv_value: u32, cltv_expiry: u32
 455 ) -> Result<(), (&'static str, u16)> {
 456         if (cltv_expiry as u64) < (outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
 457                 return Err((
 458                         "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
 459                         0x1000 | 13, // incorrect_cltv_expiry
 460                 ));
 461         }
 462         // Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
 463         // but we want to be robust wrt to counterparty packet sanitization (see
 464         // HTLC_FAIL_BACK_BUFFER rationale).
 465         if cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
 466                 return Err(("CLTV expiry is too close", 0x1000 | 14));
 467         }
 468         if cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
 469                 return Err(("CLTV expiry is too far in the future", 21));
 470         }
 471         // If the HTLC expires ~now, don't bother trying to forward it to our
 472         // counterparty. They should fail it anyway, but we don't want to bother with
 473         // the round-trips or risk them deciding they definitely want the HTLC and
 474         // force-closing to ensure they get it if we're offline.
 475         // We previously had a much more aggressive check here which tried to ensure
 476         // our counterparty receives an HTLC which has *our* risk threshold met on it,
 477         // but there is no need to do that, and since we're a bit conservative with our
 478         // risk threshold it just results in failing to forward payments.
 479         if (outgoing_cltv_value) as u64 <= (cur_height + LATENCY_GRACE_PERIOD_BLOCKS) as u64 {
 480                 return Err(("Outgoing CLTV value is too soon", 0x1000 | 14));
 481         }
 482
 483         Ok(())
 484 }
 485
 486 #[cfg(test)]
 487 mod tests {
 488         use bitcoin::hashes::Hash;
 489         use bitcoin::hashes::sha256::Hash as Sha256;
 490         use bitcoin::secp256k1::{PublicKey, SecretKey};
 491         use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 492         use crate::ln::ChannelId;
 493         use crate::ln::channelmanager::RecipientOnionFields;
 494         use crate::ln::features::{ChannelFeatures, NodeFeatures};
 495         use crate::ln::msgs;
 496         use crate::ln::onion_utils::create_payment_onion;
 497         use crate::routing::router::{Path, RouteHop};
 498         use crate::util::test_utils;
 499
 500         #[test]
 501         fn test_peel_payment_onion() {
 502                 use super::*;
 503                 let secp_ctx = Secp256k1::new();
 504
 505                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 506                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 507                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 508                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 509
 510                 let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 511                         prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
 512
 513                 let path = Path {
 514                         hops: hops,
 515                         blinded_tail: None,
 516                 };
 517
 518                 let (onion, amount_msat, cltv_expiry) = create_payment_onion(
 519                         &secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
 520                         &payment_hash, &Some(preimage), prng_seed
 521                 ).unwrap();
 522
 523                 let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
 524                 let logger = test_utils::TestLogger::with_id("bob".to_string());
 525
 526                 let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true, false)
 527                         .map_err(|e| e.msg).unwrap();
 528
 529                 let next_onion = match peeled.routing {
 530                         PendingHTLCRouting::Forward { onion_packet, .. } => {
 531                                 onion_packet
 532                         },
 533                         _ => panic!("expected a forwarded onion"),
 534                 };
 535
 536                 let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
 537                 let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true, false)
 538                         .map_err(|e| e.msg).unwrap();
 539
 540                 match peeled2.routing {
 541                         PendingHTLCRouting::ReceiveKeysend { payment_preimage, payment_data, incoming_cltv_expiry, .. } => {
 542                                 assert_eq!(payment_preimage, preimage);
 543                                 assert_eq!(peeled2.outgoing_amt_msat, recipient_amount);
 544                                 assert_eq!(incoming_cltv_expiry, peeled2.outgoing_cltv_value);
 545                                 let msgs::FinalOnionHopData{total_msat, payment_secret} = payment_data.unwrap();
 546                                 assert_eq!(total_msat, total_amt_msat);
 547                                 assert_eq!(payment_secret, pay_secret);
 548                         },
 549                         _ => panic!("expected a received keysend"),
 550                 };
 551         }
 552
 553         fn make_update_add_msg(
 554                 amount_msat: u64, cltv_expiry: u32, payment_hash: PaymentHash,
 555                 onion_routing_packet: msgs::OnionPacket
 556         ) -> msgs::UpdateAddHTLC {
 557                 msgs::UpdateAddHTLC {
 558                         channel_id: ChannelId::from_bytes([0; 32]),
 559                         htlc_id: 0,
 560                         amount_msat,
 561                         cltv_expiry,
 562                         payment_hash,
 563                         onion_routing_packet,
 564                         skimmed_fee_msat: None,
 565                         blinding_point: None,
 566                 }
 567         }
 568
 569         fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
 570                 SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
 571                 Vec<RouteHop>, u64, PaymentSecret,
 572         ) {
 573                 let session_priv_bytes = [42; 32];
 574                 let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
 575                 let total_amt_msat = 1000;
 576                 let cur_height = 1000;
 577                 let pay_secret = PaymentSecret([99; 32]);
 578                 let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
 579                 let preimage_bytes = [43; 32];
 580                 let preimage = PaymentPreimage(preimage_bytes);
 581                 let rhash_bytes = Sha256::hash(&preimage_bytes).to_byte_array();
 582                 let payment_hash = PaymentHash(rhash_bytes);
 583                 let prng_seed = [44; 32];
 584
 585                 // make a route alice -> bob -> charlie
 586                 let hop_fee = 1;
 587                 let recipient_amount = total_amt_msat - hop_fee;
 588                 let hops = vec![
 589                         RouteHop {
 590                                 pubkey: hop_pk,
 591                                 fee_msat: hop_fee,
 592                                 cltv_expiry_delta: 42,
 593                                 short_channel_id: 1,
 594                                 node_features: NodeFeatures::empty(),
 595                                 channel_features: ChannelFeatures::empty(),
 596                                 maybe_announced_channel: false,
 597                         },
 598                         RouteHop {
 599                                 pubkey: recipient_pk,
 600                                 fee_msat: recipient_amount,
 601                                 cltv_expiry_delta: 42,
 602                                 short_channel_id: 2,
 603                                 node_features: NodeFeatures::empty(),
 604                                 channel_features: ChannelFeatures::empty(),
 605                                 maybe_announced_channel: false,
 606                         }
 607                 ];
 608
 609                 (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 610                         prng_seed, hops, recipient_amount, pay_secret)
 611         }
 612
 613 }