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 #[derive(Debug)]
  28 pub struct InboundHTLCErr {
  29         /// BOLT 4 error code.
  30         pub err_code: u16,
  31         /// Data attached to this error.
  32         pub err_data: Vec<u8>,
  33         /// Error message text.
  34         pub msg: &'static str,
  35 }
  36
  37 fn check_blinded_payment_constraints(
  38         amt_msat: u64, cltv_expiry: u32, constraints: &PaymentConstraints
  39 ) -> Result<(), ()> {
  40         if amt_msat < constraints.htlc_minimum_msat ||
  41                 cltv_expiry > constraints.max_cltv_expiry
  42         { return Err(()) }
  43         Ok(())
  44 }
  45
  46 fn check_blinded_forward(
  47         inbound_amt_msat: u64, inbound_cltv_expiry: u32, payment_relay: &PaymentRelay,
  48         payment_constraints: &PaymentConstraints, features: &BlindedHopFeatures
  49 ) -> Result<(u64, u32), ()> {
  50         let amt_to_forward = blinded_path::payment::amt_to_forward_msat(
  51                 inbound_amt_msat, payment_relay
  52         ).ok_or(())?;
  53         let outgoing_cltv_value = inbound_cltv_expiry.checked_sub(
  54                 payment_relay.cltv_expiry_delta as u32
  55         ).ok_or(())?;
  56         check_blinded_payment_constraints(inbound_amt_msat, outgoing_cltv_value, payment_constraints)?;
  57
  58         if features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
  59         Ok((amt_to_forward, outgoing_cltv_value))
  60 }
  61
  62 pub(super) fn create_fwd_pending_htlc_info(
  63         msg: &msgs::UpdateAddHTLC, hop_data: msgs::InboundOnionPayload, hop_hmac: [u8; 32],
  64         new_packet_bytes: [u8; onion_utils::ONION_DATA_LEN], shared_secret: [u8; 32],
  65         next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
  66 ) -> Result<PendingHTLCInfo, InboundHTLCErr> {
  67         debug_assert!(next_packet_pubkey_opt.is_some());
  68         let outgoing_packet = msgs::OnionPacket {
  69                 version: 0,
  70                 public_key: next_packet_pubkey_opt.unwrap_or(Err(secp256k1::Error::InvalidPublicKey)),
  71                 hop_data: new_packet_bytes,
  72                 hmac: hop_hmac,
  73         };
  74
  75         let (
  76                 short_channel_id, amt_to_forward, outgoing_cltv_value, inbound_blinding_point
  77         ) = match hop_data {
  78                 msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
  79                         (short_channel_id, amt_to_forward, outgoing_cltv_value, None),
  80                 msgs::InboundOnionPayload::BlindedForward {
  81                         short_channel_id, payment_relay, payment_constraints, intro_node_blinding_point, features,
  82                 } => {
  83                         let (amt_to_forward, outgoing_cltv_value) = check_blinded_forward(
  84                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
  85                         ).map_err(|()| {
  86                                 // We should be returning malformed here if `msg.blinding_point` is set, but this is
  87                                 // unreachable right now since we checked it in `decode_update_add_htlc_onion`.
  88                                 InboundHTLCErr {
  89                                         msg: "Underflow calculating outbound amount or cltv value for blinded forward",
  90                                         err_code: INVALID_ONION_BLINDING,
  91                                         err_data: vec![0; 32],
  92                                 }
  93                         })?;
  94                         (short_channel_id, amt_to_forward, outgoing_cltv_value, Some(intro_node_blinding_point))
  95                 },
  96                 msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
  97                         return Err(InboundHTLCErr {
  98                                 msg: "Final Node OnionHopData provided for us as an intermediary node",
  99                                 err_code: 0x4000 | 22,
 100                                 err_data: Vec::new(),
 101                         }),
 102         };
 103
 104         Ok(PendingHTLCInfo {
 105                 routing: PendingHTLCRouting::Forward {
 106                         onion_packet: outgoing_packet,
 107                         short_channel_id,
 108                         blinded: inbound_blinding_point.map(|bp| BlindedForward { inbound_blinding_point: bp }),
 109                 },
 110                 payment_hash: msg.payment_hash,
 111                 incoming_shared_secret: shared_secret,
 112                 incoming_amt_msat: Some(msg.amount_msat),
 113                 outgoing_amt_msat: amt_to_forward,
 114                 outgoing_cltv_value,
 115                 skimmed_fee_msat: None,
 116         })
 117 }
 118
 119 pub(super) fn create_recv_pending_htlc_info(
 120         hop_data: msgs::InboundOnionPayload, shared_secret: [u8; 32], payment_hash: PaymentHash,
 121         amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
 122         counterparty_skimmed_fee_msat: Option<u64>, current_height: u32, accept_mpp_keysend: bool,
 123 ) -> Result<PendingHTLCInfo, InboundHTLCErr> {
 124         let (
 125                 payment_data, keysend_preimage, custom_tlvs, onion_amt_msat, onion_cltv_expiry,
 126                 payment_metadata, requires_blinded_error
 127         ) = match hop_data {
 128                 msgs::InboundOnionPayload::Receive {
 129                         payment_data, keysend_preimage, custom_tlvs, sender_intended_htlc_amt_msat,
 130                         cltv_expiry_height, payment_metadata, ..
 131                 } =>
 132                         (payment_data, keysend_preimage, custom_tlvs, sender_intended_htlc_amt_msat,
 133                          cltv_expiry_height, payment_metadata, false),
 134                 msgs::InboundOnionPayload::BlindedReceive {
 135                         amt_msat, total_msat, cltv_expiry_height, payment_secret, intro_node_blinding_point,
 136                         payment_constraints, ..
 137                 } => {
 138                         check_blinded_payment_constraints(amt_msat, cltv_expiry, &payment_constraints)
 139                                 .map_err(|()| {
 140                                         InboundHTLCErr {
 141                                                 err_code: INVALID_ONION_BLINDING,
 142                                                 err_data: vec![0; 32],
 143                                                 msg: "Amount or cltv_expiry violated blinded payment constraints",
 144                                         }
 145                                 })?;
 146                         let payment_data = msgs::FinalOnionHopData { payment_secret, total_msat };
 147                         (Some(payment_data), None, Vec::new(), amt_msat, cltv_expiry_height, None,
 148                          intro_node_blinding_point.is_none())
 149                 }
 150                 msgs::InboundOnionPayload::Forward { .. } => {
 151                         return Err(InboundHTLCErr {
 152                                 err_code: 0x4000|22,
 153                                 err_data: Vec::new(),
 154                                 msg: "Got non final data with an HMAC of 0",
 155                         })
 156                 },
 157                 msgs::InboundOnionPayload::BlindedForward { .. } => {
 158                         return Err(InboundHTLCErr {
 159                                 err_code: INVALID_ONION_BLINDING,
 160                                 err_data: vec![0; 32],
 161                                 msg: "Got blinded non final data with an HMAC of 0",
 162                         })
 163                 }
 164         };
 165         // final_incorrect_cltv_expiry
 166         if onion_cltv_expiry > cltv_expiry {
 167                 return Err(InboundHTLCErr {
 168                         msg: "Upstream node set CLTV to less than the CLTV set by the sender",
 169                         err_code: 18,
 170                         err_data: cltv_expiry.to_be_bytes().to_vec()
 171                 })
 172         }
 173         // final_expiry_too_soon
 174         // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
 175         // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
 176         //
 177         // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
 178         // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
 179         // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
 180         if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
 181                 let mut err_data = Vec::with_capacity(12);
 182                 err_data.extend_from_slice(&amt_msat.to_be_bytes());
 183                 err_data.extend_from_slice(&current_height.to_be_bytes());
 184                 return Err(InboundHTLCErr {
 185                         err_code: 0x4000 | 15, err_data,
 186                         msg: "The final CLTV expiry is too soon to handle",
 187                 });
 188         }
 189         if (!allow_underpay && onion_amt_msat > amt_msat) ||
 190                 (allow_underpay && onion_amt_msat >
 191                  amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
 192         {
 193                 return Err(InboundHTLCErr {
 194                         err_code: 19,
 195                         err_data: amt_msat.to_be_bytes().to_vec(),
 196                         msg: "Upstream node sent less than we were supposed to receive in payment",
 197                 });
 198         }
 199
 200         let routing = if let Some(payment_preimage) = keysend_preimage {
 201                 // We need to check that the sender knows the keysend preimage before processing this
 202                 // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
 203                 // could discover the final destination of X, by probing the adjacent nodes on the route
 204                 // with a keysend payment of identical payment hash to X and observing the processing
 205                 // time discrepancies due to a hash collision with X.
 206                 let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).to_byte_array());
 207                 if hashed_preimage != payment_hash {
 208                         return Err(InboundHTLCErr {
 209                                 err_code: 0x4000|22,
 210                                 err_data: Vec::new(),
 211                                 msg: "Payment preimage didn't match payment hash",
 212                         });
 213                 }
 214                 if !accept_mpp_keysend && payment_data.is_some() {
 215                         return Err(InboundHTLCErr {
 216                                 err_code: 0x4000|22,
 217                                 err_data: Vec::new(),
 218                                 msg: "We don't support MPP keysend payments",
 219                         });
 220                 }
 221                 PendingHTLCRouting::ReceiveKeysend {
 222                         payment_data,
 223                         payment_preimage,
 224                         payment_metadata,
 225                         incoming_cltv_expiry: onion_cltv_expiry,
 226                         custom_tlvs,
 227                 }
 228         } else if let Some(data) = payment_data {
 229                 PendingHTLCRouting::Receive {
 230                         payment_data: data,
 231                         payment_metadata,
 232                         incoming_cltv_expiry: onion_cltv_expiry,
 233                         phantom_shared_secret,
 234                         custom_tlvs,
 235                         requires_blinded_error,
 236                 }
 237         } else {
 238                 return Err(InboundHTLCErr {
 239                         err_code: 0x4000|0x2000|3,
 240                         err_data: Vec::new(),
 241                         msg: "We require payment_secrets",
 242                 });
 243         };
 244         Ok(PendingHTLCInfo {
 245                 routing,
 246                 payment_hash,
 247                 incoming_shared_secret: shared_secret,
 248                 incoming_amt_msat: Some(amt_msat),
 249                 outgoing_amt_msat: onion_amt_msat,
 250                 outgoing_cltv_value: onion_cltv_expiry,
 251                 skimmed_fee_msat: counterparty_skimmed_fee_msat,
 252         })
 253 }
 254
 255 /// Peel one layer off an incoming onion, returning a [`PendingHTLCInfo`] that contains information
 256 /// about the intended next-hop for the HTLC.
 257 ///
 258 /// This does all the relevant context-free checks that LDK requires for payment relay or
 259 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
 260 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
 261 /// channel, will generate an [`Event::PaymentClaimable`].
 262 ///
 263 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
 264 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 265         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 266         cur_height: u32, accept_mpp_keysend: bool, allow_skimmed_fees: bool,
 267 ) -> Result<PendingHTLCInfo, InboundHTLCErr>
 268 where
 269         NS::Target: NodeSigner,
 270         L::Target: Logger,
 271 {
 272         let (hop, shared_secret, next_packet_details_opt) =
 273                 decode_incoming_update_add_htlc_onion(msg, node_signer, logger, secp_ctx
 274         ).map_err(|e| {
 275                 let (err_code, err_data) = match e {
 276                         HTLCFailureMsg::Malformed(m) => (m.failure_code, Vec::new()),
 277                         HTLCFailureMsg::Relay(r) => (0x4000 | 22, r.reason.data),
 278                 };
 279                 let msg = "Failed to decode update add htlc onion";
 280                 InboundHTLCErr { msg, err_code, err_data }
 281         })?;
 282         Ok(match hop {
 283                 onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
 284                         let NextPacketDetails {
 285                                 next_packet_pubkey, outgoing_amt_msat: _, outgoing_scid: _, outgoing_cltv_value
 286                         } = match next_packet_details_opt {
 287                                 Some(next_packet_details) => next_packet_details,
 288                                 // Forward should always include the next hop details
 289                                 None => return Err(InboundHTLCErr {
 290                                         msg: "Failed to decode update add htlc onion",
 291                                         err_code: 0x4000 | 22,
 292                                         err_data: Vec::new(),
 293                                 }),
 294                         };
 295
 296                         if let Err((err_msg, code)) = check_incoming_htlc_cltv(
 297                                 cur_height, outgoing_cltv_value, msg.cltv_expiry
 298                         ) {
 299                                 return Err(InboundHTLCErr {
 300                                         msg: err_msg,
 301                                         err_code: code,
 302                                         err_data: Vec::new(),
 303                                 });
 304                         }
 305
 306                         // TODO: If this is potentially a phantom payment we should decode the phantom payment
 307                         // onion here and check it.
 308
 309                         create_fwd_pending_htlc_info(
 310                                 msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
 311                                 Some(next_packet_pubkey)
 312                         )?
 313                 },
 314                 onion_utils::Hop::Receive(received_data) => {
 315                         create_recv_pending_htlc_info(
 316                                 received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
 317                                 None, allow_skimmed_fees, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
 318                         )?
 319                 }
 320         })
 321 }
 322
 323 pub(super) struct NextPacketDetails {
 324         pub(super) next_packet_pubkey: Result<PublicKey, secp256k1::Error>,
 325         pub(super) outgoing_scid: u64,
 326         pub(super) outgoing_amt_msat: u64,
 327         pub(super) outgoing_cltv_value: u32,
 328 }
 329
 330 pub(super) fn decode_incoming_update_add_htlc_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 331         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 332 ) -> Result<(onion_utils::Hop, [u8; 32], Option<NextPacketDetails>), HTLCFailureMsg>
 333 where
 334         NS::Target: NodeSigner,
 335         L::Target: Logger,
 336 {
 337         macro_rules! return_malformed_err {
 338                 ($msg: expr, $err_code: expr) => {
 339                         {
 340                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 341                                 let (sha256_of_onion, failure_code) = if msg.blinding_point.is_some() {
 342                                         ([0; 32], INVALID_ONION_BLINDING)
 343                                 } else {
 344                                         (Sha256::hash(&msg.onion_routing_packet.hop_data).to_byte_array(), $err_code)
 345                                 };
 346                                 return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
 347                                         channel_id: msg.channel_id,
 348                                         htlc_id: msg.htlc_id,
 349                                         sha256_of_onion,
 350                                         failure_code,
 351                                 }));
 352                         }
 353                 }
 354         }
 355
 356         if let Err(_) = msg.onion_routing_packet.public_key {
 357                 return_malformed_err!("invalid ephemeral pubkey", 0x8000 | 0x4000 | 6);
 358         }
 359
 360         let blinded_node_id_tweak = msg.blinding_point.map(|bp| {
 361                 let blinded_tlvs_ss = node_signer.ecdh(Recipient::Node, &bp, None).unwrap().secret_bytes();
 362                 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 363                 hmac.input(blinded_tlvs_ss.as_ref());
 364                 Scalar::from_be_bytes(Hmac::from_engine(hmac).to_byte_array()).unwrap()
 365         });
 366         let shared_secret = node_signer.ecdh(
 367                 Recipient::Node, &msg.onion_routing_packet.public_key.unwrap(), blinded_node_id_tweak.as_ref()
 368         ).unwrap().secret_bytes();
 369
 370         if msg.onion_routing_packet.version != 0 {
 371                 //TODO: Spec doesn't indicate if we should only hash hop_data here (and in other
 372                 //sha256_of_onion error data packets), or the entire onion_routing_packet. Either way,
 373                 //the hash doesn't really serve any purpose - in the case of hashing all data, the
 374                 //receiving node would have to brute force to figure out which version was put in the
 375                 //packet by the node that send us the message, in the case of hashing the hop_data, the
 376                 //node knows the HMAC matched, so they already know what is there...
 377                 return_malformed_err!("Unknown onion packet version", 0x8000 | 0x4000 | 4);
 378         }
 379         macro_rules! return_err {
 380                 ($msg: expr, $err_code: expr, $data: expr) => {
 381                         {
 382                                 if msg.blinding_point.is_some() {
 383                                         return_malformed_err!($msg, INVALID_ONION_BLINDING)
 384                                 }
 385
 386                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 387                                 return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
 388                                         channel_id: msg.channel_id,
 389                                         htlc_id: msg.htlc_id,
 390                                         reason: HTLCFailReason::reason($err_code, $data.to_vec())
 391                                                 .get_encrypted_failure_packet(&shared_secret, &None),
 392                                 }));
 393                         }
 394                 }
 395         }
 396
 397         let next_hop = match onion_utils::decode_next_payment_hop(
 398                 shared_secret, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 399                 msg.payment_hash, msg.blinding_point, node_signer
 400         ) {
 401                 Ok(res) => res,
 402                 Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
 403                         return_malformed_err!(err_msg, err_code);
 404                 },
 405                 Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
 406                         return_err!(err_msg, err_code, &[0; 0]);
 407                 },
 408         };
 409
 410         let next_packet_details = match next_hop {
 411                 onion_utils::Hop::Forward {
 412                         next_hop_data: msgs::InboundOnionPayload::Forward {
 413                                 short_channel_id, amt_to_forward, outgoing_cltv_value
 414                         }, ..
 415                 } => {
 416                         let next_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
 417                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 418                         NextPacketDetails {
 419                                 next_packet_pubkey, outgoing_scid: short_channel_id,
 420                                 outgoing_amt_msat: amt_to_forward, outgoing_cltv_value
 421                         }
 422                 },
 423                 onion_utils::Hop::Forward {
 424                         next_hop_data: msgs::InboundOnionPayload::BlindedForward {
 425                                 short_channel_id, ref payment_relay, ref payment_constraints, ref features, ..
 426                         }, ..
 427                 } => {
 428                         let (amt_to_forward, outgoing_cltv_value) = match check_blinded_forward(
 429                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
 430                         ) {
 431                                 Ok((amt, cltv)) => (amt, cltv),
 432                                 Err(()) => {
 433                                         return_err!("Underflow calculating outbound amount or cltv value for blinded forward",
 434                                                 INVALID_ONION_BLINDING, &[0; 32]);
 435                                 }
 436                         };
 437                         let next_packet_pubkey = onion_utils::next_hop_pubkey(&secp_ctx,
 438                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 439                         NextPacketDetails {
 440                                 next_packet_pubkey, outgoing_scid: short_channel_id, outgoing_amt_msat: amt_to_forward,
 441                                 outgoing_cltv_value
 442                         }
 443                 },
 444                 onion_utils::Hop::Receive { .. } => return Ok((next_hop, shared_secret, None)),
 445                 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::Receive { .. }, .. } |
 446                         onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::BlindedReceive { .. }, .. } =>
 447                 {
 448                         return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0; 0]);
 449                 }
 450         };
 451
 452         Ok((next_hop, shared_secret, Some(next_packet_details)))
 453 }
 454
 455 pub(super) fn check_incoming_htlc_cltv(
 456         cur_height: u32, outgoing_cltv_value: u32, cltv_expiry: u32
 457 ) -> Result<(), (&'static str, u16)> {
 458         if (cltv_expiry as u64) < (outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
 459                 return Err((
 460                         "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
 461                         0x1000 | 13, // incorrect_cltv_expiry
 462                 ));
 463         }
 464         // Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
 465         // but we want to be robust wrt to counterparty packet sanitization (see
 466         // HTLC_FAIL_BACK_BUFFER rationale).
 467         if cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
 468                 return Err(("CLTV expiry is too close", 0x1000 | 14));
 469         }
 470         if cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
 471                 return Err(("CLTV expiry is too far in the future", 21));
 472         }
 473         // If the HTLC expires ~now, don't bother trying to forward it to our
 474         // counterparty. They should fail it anyway, but we don't want to bother with
 475         // the round-trips or risk them deciding they definitely want the HTLC and
 476         // force-closing to ensure they get it if we're offline.
 477         // We previously had a much more aggressive check here which tried to ensure
 478         // our counterparty receives an HTLC which has *our* risk threshold met on it,
 479         // but there is no need to do that, and since we're a bit conservative with our
 480         // risk threshold it just results in failing to forward payments.
 481         if (outgoing_cltv_value) as u64 <= (cur_height + LATENCY_GRACE_PERIOD_BLOCKS) as u64 {
 482                 return Err(("Outgoing CLTV value is too soon", 0x1000 | 14));
 483         }
 484
 485         Ok(())
 486 }
 487
 488 #[cfg(test)]
 489 mod tests {
 490         use bitcoin::hashes::Hash;
 491         use bitcoin::hashes::sha256::Hash as Sha256;
 492         use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
 493         use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 494         use crate::ln::ChannelId;
 495         use crate::ln::channelmanager::RecipientOnionFields;
 496         use crate::ln::features::{ChannelFeatures, NodeFeatures};
 497         use crate::ln::msgs;
 498         use crate::ln::onion_utils::create_payment_onion;
 499         use crate::routing::router::{Path, RouteHop};
 500         use crate::util::test_utils;
 501
 502         #[test]
 503         fn fail_construct_onion_on_too_big_payloads() {
 504                 // Ensure that if we call `construct_onion_packet` and friends where payloads are too large for
 505                 // the allotted packet length, we'll fail to construct. Previously, senders would happily
 506                 // construct invalid packets by array-shifting the final node's HMAC out of the packet when
 507                 // adding an intermediate onion layer, causing the receiver to error with "final payload
 508                 // provided for us as an intermediate node."
 509                 let secp_ctx = Secp256k1::new();
 510                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 511                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 512                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 513                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 514
 515                 let (
 516                         session_priv, total_amt_msat, cur_height, mut recipient_onion, keysend_preimage, payment_hash,
 517                         prng_seed, hops, ..
 518                 ) = payment_onion_args(bob_pk, charlie_pk);
 519
 520                 // Ensure the onion will not fit all the payloads by adding a large custom TLV.
 521                 recipient_onion.custom_tlvs.push((13377331, vec![0; 1156]));
 522
 523                 let path = Path { hops, blinded_tail: None, };
 524                 let onion_keys = super::onion_utils::construct_onion_keys(&secp_ctx, &path, &session_priv).unwrap();
 525                 let (onion_payloads, ..) = super::onion_utils::build_onion_payloads(
 526                         &path, total_amt_msat, recipient_onion, cur_height + 1, &Some(keysend_preimage)
 527                 ).unwrap();
 528
 529                 assert!(super::onion_utils::construct_onion_packet(
 530                                 onion_payloads, onion_keys, prng_seed, &payment_hash
 531                 ).is_err());
 532         }
 533
 534         #[test]
 535         fn test_peel_payment_onion() {
 536                 use super::*;
 537                 let secp_ctx = Secp256k1::new();
 538
 539                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 540                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 541                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 542                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 543
 544                 let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 545                         prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
 546
 547                 let path = Path {
 548                         hops: hops,
 549                         blinded_tail: None,
 550                 };
 551
 552                 let (onion, amount_msat, cltv_expiry) = create_payment_onion(
 553                         &secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
 554                         &payment_hash, &Some(preimage), prng_seed
 555                 ).unwrap();
 556
 557                 let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
 558                 let logger = test_utils::TestLogger::with_id("bob".to_string());
 559
 560                 let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true, false)
 561                         .map_err(|e| e.msg).unwrap();
 562
 563                 let next_onion = match peeled.routing {
 564                         PendingHTLCRouting::Forward { onion_packet, .. } => {
 565                                 onion_packet
 566                         },
 567                         _ => panic!("expected a forwarded onion"),
 568                 };
 569
 570                 let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
 571                 let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true, false)
 572                         .map_err(|e| e.msg).unwrap();
 573
 574                 match peeled2.routing {
 575                         PendingHTLCRouting::ReceiveKeysend { payment_preimage, payment_data, incoming_cltv_expiry, .. } => {
 576                                 assert_eq!(payment_preimage, preimage);
 577                                 assert_eq!(peeled2.outgoing_amt_msat, recipient_amount);
 578                                 assert_eq!(incoming_cltv_expiry, peeled2.outgoing_cltv_value);
 579                                 let msgs::FinalOnionHopData{total_msat, payment_secret} = payment_data.unwrap();
 580                                 assert_eq!(total_msat, total_amt_msat);
 581                                 assert_eq!(payment_secret, pay_secret);
 582                         },
 583                         _ => panic!("expected a received keysend"),
 584                 };
 585         }
 586
 587         fn make_update_add_msg(
 588                 amount_msat: u64, cltv_expiry: u32, payment_hash: PaymentHash,
 589                 onion_routing_packet: msgs::OnionPacket
 590         ) -> msgs::UpdateAddHTLC {
 591                 msgs::UpdateAddHTLC {
 592                         channel_id: ChannelId::from_bytes([0; 32]),
 593                         htlc_id: 0,
 594                         amount_msat,
 595                         cltv_expiry,
 596                         payment_hash,
 597                         onion_routing_packet,
 598                         skimmed_fee_msat: None,
 599                         blinding_point: None,
 600                 }
 601         }
 602
 603         fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
 604                 SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
 605                 Vec<RouteHop>, u64, PaymentSecret,
 606         ) {
 607                 let session_priv_bytes = [42; 32];
 608                 let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
 609                 let total_amt_msat = 1000;
 610                 let cur_height = 1000;
 611                 let pay_secret = PaymentSecret([99; 32]);
 612                 let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
 613                 let preimage_bytes = [43; 32];
 614                 let preimage = PaymentPreimage(preimage_bytes);
 615                 let rhash_bytes = Sha256::hash(&preimage_bytes).to_byte_array();
 616                 let payment_hash = PaymentHash(rhash_bytes);
 617                 let prng_seed = [44; 32];
 618
 619                 // make a route alice -> bob -> charlie
 620                 let hop_fee = 1;
 621                 let recipient_amount = total_amt_msat - hop_fee;
 622                 let hops = vec![
 623                         RouteHop {
 624                                 pubkey: hop_pk,
 625                                 fee_msat: hop_fee,
 626                                 cltv_expiry_delta: 42,
 627                                 short_channel_id: 1,
 628                                 node_features: NodeFeatures::empty(),
 629                                 channel_features: ChannelFeatures::empty(),
 630                                 maybe_announced_channel: false,
 631                         },
 632                         RouteHop {
 633                                 pubkey: recipient_pk,
 634                                 fee_msat: recipient_amount,
 635                                 cltv_expiry_delta: 42,
 636                                 short_channel_id: 2,
 637                                 node_features: NodeFeatures::empty(),
 638                                 channel_features: ChannelFeatures::empty(),
 639                                 maybe_announced_channel: false,
 640                         }
 641                 ];
 642
 643                 (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 644                         prng_seed, hops, recipient_amount, pay_secret)
 645         }
 646
 647 }