_ 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::{BlindedFailure, 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 #[allow(unused_imports)]
  24 use crate::prelude::*;
  25
  26 use core::ops::Deref;
  27
  28 /// Invalid inbound onion payment.
  29 #[derive(Debug)]
  30 pub struct InboundHTLCErr {
  31         /// BOLT 4 error code.
  32         pub err_code: u16,
  33         /// Data attached to this error.
  34         pub err_data: Vec<u8>,
  35         /// Error message text.
  36         pub msg: &'static str,
  37 }
  38
  39 fn check_blinded_payment_constraints(
  40         amt_msat: u64, cltv_expiry: u32, constraints: &PaymentConstraints
  41 ) -> Result<(), ()> {
  42         if amt_msat < constraints.htlc_minimum_msat ||
  43                 cltv_expiry > constraints.max_cltv_expiry
  44         { return Err(()) }
  45         Ok(())
  46 }
  47
  48 fn check_blinded_forward(
  49         inbound_amt_msat: u64, inbound_cltv_expiry: u32, payment_relay: &PaymentRelay,
  50         payment_constraints: &PaymentConstraints, features: &BlindedHopFeatures
  51 ) -> Result<(u64, u32), ()> {
  52         let amt_to_forward = blinded_path::payment::amt_to_forward_msat(
  53                 inbound_amt_msat, payment_relay
  54         ).ok_or(())?;
  55         let outgoing_cltv_value = inbound_cltv_expiry.checked_sub(
  56                 payment_relay.cltv_expiry_delta as u32
  57         ).ok_or(())?;
  58         check_blinded_payment_constraints(inbound_amt_msat, outgoing_cltv_value, payment_constraints)?;
  59
  60         if features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
  61         Ok((amt_to_forward, outgoing_cltv_value))
  62 }
  63
  64 pub(super) fn create_fwd_pending_htlc_info(
  65         msg: &msgs::UpdateAddHTLC, hop_data: msgs::InboundOnionPayload, hop_hmac: [u8; 32],
  66         new_packet_bytes: [u8; onion_utils::ONION_DATA_LEN], shared_secret: [u8; 32],
  67         next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
  68 ) -> Result<PendingHTLCInfo, InboundHTLCErr> {
  69         debug_assert!(next_packet_pubkey_opt.is_some());
  70         let outgoing_packet = msgs::OnionPacket {
  71                 version: 0,
  72                 public_key: next_packet_pubkey_opt.unwrap_or(Err(secp256k1::Error::InvalidPublicKey)),
  73                 hop_data: new_packet_bytes,
  74                 hmac: hop_hmac,
  75         };
  76
  77         let (
  78                 short_channel_id, amt_to_forward, outgoing_cltv_value, intro_node_blinding_point
  79         ) = match hop_data {
  80                 msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
  81                         (short_channel_id, amt_to_forward, outgoing_cltv_value, None),
  82                 msgs::InboundOnionPayload::BlindedForward {
  83                         short_channel_id, payment_relay, payment_constraints, intro_node_blinding_point, features,
  84                 } => {
  85                         let (amt_to_forward, outgoing_cltv_value) = check_blinded_forward(
  86                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
  87                         ).map_err(|()| {
  88                                 // We should be returning malformed here if `msg.blinding_point` is set, but this is
  89                                 // unreachable right now since we checked it in `decode_update_add_htlc_onion`.
  90                                 InboundHTLCErr {
  91                                         msg: "Underflow calculating outbound amount or cltv value for blinded forward",
  92                                         err_code: INVALID_ONION_BLINDING,
  93                                         err_data: vec![0; 32],
  94                                 }
  95                         })?;
  96                         (short_channel_id, amt_to_forward, outgoing_cltv_value, intro_node_blinding_point)
  97                 },
  98                 msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
  99                         return Err(InboundHTLCErr {
 100                                 msg: "Final Node OnionHopData provided for us as an intermediary node",
 101                                 err_code: 0x4000 | 22,
 102                                 err_data: Vec::new(),
 103                         }),
 104         };
 105
 106         Ok(PendingHTLCInfo {
 107                 routing: PendingHTLCRouting::Forward {
 108                         onion_packet: outgoing_packet,
 109                         short_channel_id,
 110                         blinded: intro_node_blinding_point.or(msg.blinding_point)
 111                                 .map(|bp| BlindedForward {
 112                                         inbound_blinding_point: bp,
 113                                         failure: intro_node_blinding_point
 114                                                 .map(|_| BlindedFailure::FromIntroductionNode)
 115                                                 .unwrap_or(BlindedFailure::FromBlindedNode),
 116                                 }),
 117                 },
 118                 payment_hash: msg.payment_hash,
 119                 incoming_shared_secret: shared_secret,
 120                 incoming_amt_msat: Some(msg.amount_msat),
 121                 outgoing_amt_msat: amt_to_forward,
 122                 outgoing_cltv_value,
 123                 skimmed_fee_msat: None,
 124         })
 125 }
 126
 127 pub(super) fn create_recv_pending_htlc_info(
 128         hop_data: msgs::InboundOnionPayload, shared_secret: [u8; 32], payment_hash: PaymentHash,
 129         amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
 130         counterparty_skimmed_fee_msat: Option<u64>, current_height: u32, accept_mpp_keysend: bool,
 131 ) -> Result<PendingHTLCInfo, InboundHTLCErr> {
 132         let (
 133                 payment_data, keysend_preimage, custom_tlvs, onion_amt_msat, onion_cltv_expiry,
 134                 payment_metadata, requires_blinded_error
 135         ) = match hop_data {
 136                 msgs::InboundOnionPayload::Receive {
 137                         payment_data, keysend_preimage, custom_tlvs, sender_intended_htlc_amt_msat,
 138                         cltv_expiry_height, payment_metadata, ..
 139                 } =>
 140                         (payment_data, keysend_preimage, custom_tlvs, sender_intended_htlc_amt_msat,
 141                          cltv_expiry_height, payment_metadata, false),
 142                 msgs::InboundOnionPayload::BlindedReceive {
 143                         sender_intended_htlc_amt_msat, total_msat, cltv_expiry_height, payment_secret,
 144                         intro_node_blinding_point, payment_constraints, keysend_preimage, custom_tlvs
 145                 } => {
 146                         check_blinded_payment_constraints(
 147                                 sender_intended_htlc_amt_msat, cltv_expiry, &payment_constraints
 148                         )
 149                                 .map_err(|()| {
 150                                         InboundHTLCErr {
 151                                                 err_code: INVALID_ONION_BLINDING,
 152                                                 err_data: vec![0; 32],
 153                                                 msg: "Amount or cltv_expiry violated blinded payment constraints",
 154                                         }
 155                                 })?;
 156                         let payment_data = msgs::FinalOnionHopData { payment_secret, total_msat };
 157                         (Some(payment_data), keysend_preimage, custom_tlvs,
 158                          sender_intended_htlc_amt_msat, cltv_expiry_height, None,
 159                          intro_node_blinding_point.is_none())
 160                 }
 161                 msgs::InboundOnionPayload::Forward { .. } => {
 162                         return Err(InboundHTLCErr {
 163                                 err_code: 0x4000|22,
 164                                 err_data: Vec::new(),
 165                                 msg: "Got non final data with an HMAC of 0",
 166                         })
 167                 },
 168                 msgs::InboundOnionPayload::BlindedForward { .. } => {
 169                         return Err(InboundHTLCErr {
 170                                 err_code: INVALID_ONION_BLINDING,
 171                                 err_data: vec![0; 32],
 172                                 msg: "Got blinded non final data with an HMAC of 0",
 173                         })
 174                 }
 175         };
 176         // final_incorrect_cltv_expiry
 177         if onion_cltv_expiry > cltv_expiry {
 178                 return Err(InboundHTLCErr {
 179                         msg: "Upstream node set CLTV to less than the CLTV set by the sender",
 180                         err_code: 18,
 181                         err_data: cltv_expiry.to_be_bytes().to_vec()
 182                 })
 183         }
 184         // final_expiry_too_soon
 185         // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
 186         // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
 187         //
 188         // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
 189         // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
 190         // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
 191         if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
 192                 let mut err_data = Vec::with_capacity(12);
 193                 err_data.extend_from_slice(&amt_msat.to_be_bytes());
 194                 err_data.extend_from_slice(&current_height.to_be_bytes());
 195                 return Err(InboundHTLCErr {
 196                         err_code: 0x4000 | 15, err_data,
 197                         msg: "The final CLTV expiry is too soon to handle",
 198                 });
 199         }
 200         if (!allow_underpay && onion_amt_msat > amt_msat) ||
 201                 (allow_underpay && onion_amt_msat >
 202                  amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
 203         {
 204                 return Err(InboundHTLCErr {
 205                         err_code: 19,
 206                         err_data: amt_msat.to_be_bytes().to_vec(),
 207                         msg: "Upstream node sent less than we were supposed to receive in payment",
 208                 });
 209         }
 210
 211         let routing = if let Some(payment_preimage) = keysend_preimage {
 212                 // We need to check that the sender knows the keysend preimage before processing this
 213                 // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
 214                 // could discover the final destination of X, by probing the adjacent nodes on the route
 215                 // with a keysend payment of identical payment hash to X and observing the processing
 216                 // time discrepancies due to a hash collision with X.
 217                 let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).to_byte_array());
 218                 if hashed_preimage != payment_hash {
 219                         return Err(InboundHTLCErr {
 220                                 err_code: 0x4000|22,
 221                                 err_data: Vec::new(),
 222                                 msg: "Payment preimage didn't match payment hash",
 223                         });
 224                 }
 225                 if !accept_mpp_keysend && payment_data.is_some() {
 226                         return Err(InboundHTLCErr {
 227                                 err_code: 0x4000|22,
 228                                 err_data: Vec::new(),
 229                                 msg: "We don't support MPP keysend payments",
 230                         });
 231                 }
 232                 PendingHTLCRouting::ReceiveKeysend {
 233                         payment_data,
 234                         payment_preimage,
 235                         payment_metadata,
 236                         incoming_cltv_expiry: onion_cltv_expiry,
 237                         custom_tlvs,
 238                         requires_blinded_error,
 239                 }
 240         } else if let Some(data) = payment_data {
 241                 PendingHTLCRouting::Receive {
 242                         payment_data: data,
 243                         payment_metadata,
 244                         incoming_cltv_expiry: onion_cltv_expiry,
 245                         phantom_shared_secret,
 246                         custom_tlvs,
 247                         requires_blinded_error,
 248                 }
 249         } else {
 250                 return Err(InboundHTLCErr {
 251                         err_code: 0x4000|0x2000|3,
 252                         err_data: Vec::new(),
 253                         msg: "We require payment_secrets",
 254                 });
 255         };
 256         Ok(PendingHTLCInfo {
 257                 routing,
 258                 payment_hash,
 259                 incoming_shared_secret: shared_secret,
 260                 incoming_amt_msat: Some(amt_msat),
 261                 outgoing_amt_msat: onion_amt_msat,
 262                 outgoing_cltv_value: onion_cltv_expiry,
 263                 skimmed_fee_msat: counterparty_skimmed_fee_msat,
 264         })
 265 }
 266
 267 /// Peel one layer off an incoming onion, returning a [`PendingHTLCInfo`] that contains information
 268 /// about the intended next-hop for the HTLC.
 269 ///
 270 /// This does all the relevant context-free checks that LDK requires for payment relay or
 271 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
 272 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
 273 /// channel, will generate an [`Event::PaymentClaimable`].
 274 ///
 275 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
 276 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 277         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 278         cur_height: u32, accept_mpp_keysend: bool, allow_skimmed_fees: bool,
 279 ) -> Result<PendingHTLCInfo, InboundHTLCErr>
 280 where
 281         NS::Target: NodeSigner,
 282         L::Target: Logger,
 283 {
 284         let (hop, shared_secret, next_packet_details_opt) =
 285                 decode_incoming_update_add_htlc_onion(msg, node_signer, logger, secp_ctx
 286         ).map_err(|e| {
 287                 let (err_code, err_data) = match e {
 288                         HTLCFailureMsg::Malformed(m) => (m.failure_code, Vec::new()),
 289                         HTLCFailureMsg::Relay(r) => (0x4000 | 22, r.reason.data),
 290                 };
 291                 let msg = "Failed to decode update add htlc onion";
 292                 InboundHTLCErr { msg, err_code, err_data }
 293         })?;
 294         Ok(match hop {
 295                 onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
 296                         let NextPacketDetails {
 297                                 next_packet_pubkey, outgoing_amt_msat: _, outgoing_scid: _, outgoing_cltv_value
 298                         } = match next_packet_details_opt {
 299                                 Some(next_packet_details) => next_packet_details,
 300                                 // Forward should always include the next hop details
 301                                 None => return Err(InboundHTLCErr {
 302                                         msg: "Failed to decode update add htlc onion",
 303                                         err_code: 0x4000 | 22,
 304                                         err_data: Vec::new(),
 305                                 }),
 306                         };
 307
 308                         if let Err((err_msg, code)) = check_incoming_htlc_cltv(
 309                                 cur_height, outgoing_cltv_value, msg.cltv_expiry
 310                         ) {
 311                                 return Err(InboundHTLCErr {
 312                                         msg: err_msg,
 313                                         err_code: code,
 314                                         err_data: Vec::new(),
 315                                 });
 316                         }
 317
 318                         // TODO: If this is potentially a phantom payment we should decode the phantom payment
 319                         // onion here and check it.
 320
 321                         create_fwd_pending_htlc_info(
 322                                 msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
 323                                 Some(next_packet_pubkey)
 324                         )?
 325                 },
 326                 onion_utils::Hop::Receive(received_data) => {
 327                         create_recv_pending_htlc_info(
 328                                 received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
 329                                 None, allow_skimmed_fees, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
 330                         )?
 331                 }
 332         })
 333 }
 334
 335 pub(super) struct NextPacketDetails {
 336         pub(super) next_packet_pubkey: Result<PublicKey, secp256k1::Error>,
 337         pub(super) outgoing_scid: u64,
 338         pub(super) outgoing_amt_msat: u64,
 339         pub(super) outgoing_cltv_value: u32,
 340 }
 341
 342 pub(super) fn decode_incoming_update_add_htlc_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
 343         msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
 344 ) -> Result<(onion_utils::Hop, [u8; 32], Option<NextPacketDetails>), HTLCFailureMsg>
 345 where
 346         NS::Target: NodeSigner,
 347         L::Target: Logger,
 348 {
 349         macro_rules! return_malformed_err {
 350                 ($msg: expr, $err_code: expr) => {
 351                         {
 352                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 353                                 let (sha256_of_onion, failure_code) = if msg.blinding_point.is_some() {
 354                                         ([0; 32], INVALID_ONION_BLINDING)
 355                                 } else {
 356                                         (Sha256::hash(&msg.onion_routing_packet.hop_data).to_byte_array(), $err_code)
 357                                 };
 358                                 return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
 359                                         channel_id: msg.channel_id,
 360                                         htlc_id: msg.htlc_id,
 361                                         sha256_of_onion,
 362                                         failure_code,
 363                                 }));
 364                         }
 365                 }
 366         }
 367
 368         if let Err(_) = msg.onion_routing_packet.public_key {
 369                 return_malformed_err!("invalid ephemeral pubkey", 0x8000 | 0x4000 | 6);
 370         }
 371
 372         let blinded_node_id_tweak = msg.blinding_point.map(|bp| {
 373                 let blinded_tlvs_ss = node_signer.ecdh(Recipient::Node, &bp, None).unwrap().secret_bytes();
 374                 let mut hmac = HmacEngine::<Sha256>::new(b"blinded_node_id");
 375                 hmac.input(blinded_tlvs_ss.as_ref());
 376                 Scalar::from_be_bytes(Hmac::from_engine(hmac).to_byte_array()).unwrap()
 377         });
 378         let shared_secret = node_signer.ecdh(
 379                 Recipient::Node, &msg.onion_routing_packet.public_key.unwrap(), blinded_node_id_tweak.as_ref()
 380         ).unwrap().secret_bytes();
 381
 382         if msg.onion_routing_packet.version != 0 {
 383                 //TODO: Spec doesn't indicate if we should only hash hop_data here (and in other
 384                 //sha256_of_onion error data packets), or the entire onion_routing_packet. Either way,
 385                 //the hash doesn't really serve any purpose - in the case of hashing all data, the
 386                 //receiving node would have to brute force to figure out which version was put in the
 387                 //packet by the node that send us the message, in the case of hashing the hop_data, the
 388                 //node knows the HMAC matched, so they already know what is there...
 389                 return_malformed_err!("Unknown onion packet version", 0x8000 | 0x4000 | 4);
 390         }
 391         macro_rules! return_err {
 392                 ($msg: expr, $err_code: expr, $data: expr) => {
 393                         {
 394                                 if msg.blinding_point.is_some() {
 395                                         return_malformed_err!($msg, INVALID_ONION_BLINDING)
 396                                 }
 397
 398                                 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
 399                                 return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
 400                                         channel_id: msg.channel_id,
 401                                         htlc_id: msg.htlc_id,
 402                                         reason: HTLCFailReason::reason($err_code, $data.to_vec())
 403                                                 .get_encrypted_failure_packet(&shared_secret, &None),
 404                                 }));
 405                         }
 406                 }
 407         }
 408
 409         let next_hop = match onion_utils::decode_next_payment_hop(
 410                 shared_secret, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
 411                 msg.payment_hash, msg.blinding_point, node_signer
 412         ) {
 413                 Ok(res) => res,
 414                 Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
 415                         return_malformed_err!(err_msg, err_code);
 416                 },
 417                 Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
 418                         return_err!(err_msg, err_code, &[0; 0]);
 419                 },
 420         };
 421
 422         let next_packet_details = match next_hop {
 423                 onion_utils::Hop::Forward {
 424                         next_hop_data: msgs::InboundOnionPayload::Forward {
 425                                 short_channel_id, amt_to_forward, outgoing_cltv_value
 426                         }, ..
 427                 } => {
 428                         let next_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
 429                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 430                         NextPacketDetails {
 431                                 next_packet_pubkey, outgoing_scid: short_channel_id,
 432                                 outgoing_amt_msat: amt_to_forward, outgoing_cltv_value
 433                         }
 434                 },
 435                 onion_utils::Hop::Forward {
 436                         next_hop_data: msgs::InboundOnionPayload::BlindedForward {
 437                                 short_channel_id, ref payment_relay, ref payment_constraints, ref features, ..
 438                         }, ..
 439                 } => {
 440                         let (amt_to_forward, outgoing_cltv_value) = match check_blinded_forward(
 441                                 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
 442                         ) {
 443                                 Ok((amt, cltv)) => (amt, cltv),
 444                                 Err(()) => {
 445                                         return_err!("Underflow calculating outbound amount or cltv value for blinded forward",
 446                                                 INVALID_ONION_BLINDING, &[0; 32]);
 447                                 }
 448                         };
 449                         let next_packet_pubkey = onion_utils::next_hop_pubkey(&secp_ctx,
 450                                 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
 451                         NextPacketDetails {
 452                                 next_packet_pubkey, outgoing_scid: short_channel_id, outgoing_amt_msat: amt_to_forward,
 453                                 outgoing_cltv_value
 454                         }
 455                 },
 456                 onion_utils::Hop::Receive { .. } => return Ok((next_hop, shared_secret, None)),
 457                 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::Receive { .. }, .. } |
 458                         onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::BlindedReceive { .. }, .. } =>
 459                 {
 460                         return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0; 0]);
 461                 }
 462         };
 463
 464         Ok((next_hop, shared_secret, Some(next_packet_details)))
 465 }
 466
 467 pub(super) fn check_incoming_htlc_cltv(
 468         cur_height: u32, outgoing_cltv_value: u32, cltv_expiry: u32
 469 ) -> Result<(), (&'static str, u16)> {
 470         if (cltv_expiry as u64) < (outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
 471                 return Err((
 472                         "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
 473                         0x1000 | 13, // incorrect_cltv_expiry
 474                 ));
 475         }
 476         // Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
 477         // but we want to be robust wrt to counterparty packet sanitization (see
 478         // HTLC_FAIL_BACK_BUFFER rationale).
 479         if cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
 480                 return Err(("CLTV expiry is too close", 0x1000 | 14));
 481         }
 482         if cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
 483                 return Err(("CLTV expiry is too far in the future", 21));
 484         }
 485         // If the HTLC expires ~now, don't bother trying to forward it to our
 486         // counterparty. They should fail it anyway, but we don't want to bother with
 487         // the round-trips or risk them deciding they definitely want the HTLC and
 488         // force-closing to ensure they get it if we're offline.
 489         // We previously had a much more aggressive check here which tried to ensure
 490         // our counterparty receives an HTLC which has *our* risk threshold met on it,
 491         // but there is no need to do that, and since we're a bit conservative with our
 492         // risk threshold it just results in failing to forward payments.
 493         if (outgoing_cltv_value) as u64 <= (cur_height + LATENCY_GRACE_PERIOD_BLOCKS) as u64 {
 494                 return Err(("Outgoing CLTV value is too soon", 0x1000 | 14));
 495         }
 496
 497         Ok(())
 498 }
 499
 500 #[cfg(test)]
 501 mod tests {
 502         use bitcoin::hashes::Hash;
 503         use bitcoin::hashes::sha256::Hash as Sha256;
 504         use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
 505         use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
 506         use crate::ln::ChannelId;
 507         use crate::ln::channelmanager::RecipientOnionFields;
 508         use crate::ln::features::{ChannelFeatures, NodeFeatures};
 509         use crate::ln::msgs;
 510         use crate::ln::onion_utils::create_payment_onion;
 511         use crate::routing::router::{Path, RouteHop};
 512         use crate::util::test_utils;
 513
 514         #[test]
 515         fn fail_construct_onion_on_too_big_payloads() {
 516                 // Ensure that if we call `construct_onion_packet` and friends where payloads are too large for
 517                 // the allotted packet length, we'll fail to construct. Previously, senders would happily
 518                 // construct invalid packets by array-shifting the final node's HMAC out of the packet when
 519                 // adding an intermediate onion layer, causing the receiver to error with "final payload
 520                 // provided for us as an intermediate node."
 521                 let secp_ctx = Secp256k1::new();
 522                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 523                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 524                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 525                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 526
 527                 let (
 528                         session_priv, total_amt_msat, cur_height, mut recipient_onion, keysend_preimage, payment_hash,
 529                         prng_seed, hops, ..
 530                 ) = payment_onion_args(bob_pk, charlie_pk);
 531
 532                 // Ensure the onion will not fit all the payloads by adding a large custom TLV.
 533                 recipient_onion.custom_tlvs.push((13377331, vec![0; 1156]));
 534
 535                 let path = Path { hops, blinded_tail: None, };
 536                 let onion_keys = super::onion_utils::construct_onion_keys(&secp_ctx, &path, &session_priv).unwrap();
 537                 let (onion_payloads, ..) = super::onion_utils::build_onion_payloads(
 538                         &path, total_amt_msat, recipient_onion, cur_height + 1, &Some(keysend_preimage)
 539                 ).unwrap();
 540
 541                 assert!(super::onion_utils::construct_onion_packet(
 542                                 onion_payloads, onion_keys, prng_seed, &payment_hash
 543                 ).is_err());
 544         }
 545
 546         #[test]
 547         fn test_peel_payment_onion() {
 548                 use super::*;
 549                 let secp_ctx = Secp256k1::new();
 550
 551                 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
 552                 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
 553                 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
 554                 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
 555
 556                 let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 557                         prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
 558
 559                 let path = Path {
 560                         hops: hops,
 561                         blinded_tail: None,
 562                 };
 563
 564                 let (onion, amount_msat, cltv_expiry) = create_payment_onion(
 565                         &secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
 566                         &payment_hash, &Some(preimage), prng_seed
 567                 ).unwrap();
 568
 569                 let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
 570                 let logger = test_utils::TestLogger::with_id("bob".to_string());
 571
 572                 let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true, false)
 573                         .map_err(|e| e.msg).unwrap();
 574
 575                 let next_onion = match peeled.routing {
 576                         PendingHTLCRouting::Forward { onion_packet, .. } => {
 577                                 onion_packet
 578                         },
 579                         _ => panic!("expected a forwarded onion"),
 580                 };
 581
 582                 let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
 583                 let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true, false)
 584                         .map_err(|e| e.msg).unwrap();
 585
 586                 match peeled2.routing {
 587                         PendingHTLCRouting::ReceiveKeysend { payment_preimage, payment_data, incoming_cltv_expiry, .. } => {
 588                                 assert_eq!(payment_preimage, preimage);
 589                                 assert_eq!(peeled2.outgoing_amt_msat, recipient_amount);
 590                                 assert_eq!(incoming_cltv_expiry, peeled2.outgoing_cltv_value);
 591                                 let msgs::FinalOnionHopData{total_msat, payment_secret} = payment_data.unwrap();
 592                                 assert_eq!(total_msat, total_amt_msat);
 593                                 assert_eq!(payment_secret, pay_secret);
 594                         },
 595                         _ => panic!("expected a received keysend"),
 596                 };
 597         }
 598
 599         fn make_update_add_msg(
 600                 amount_msat: u64, cltv_expiry: u32, payment_hash: PaymentHash,
 601                 onion_routing_packet: msgs::OnionPacket
 602         ) -> msgs::UpdateAddHTLC {
 603                 msgs::UpdateAddHTLC {
 604                         channel_id: ChannelId::from_bytes([0; 32]),
 605                         htlc_id: 0,
 606                         amount_msat,
 607                         cltv_expiry,
 608                         payment_hash,
 609                         onion_routing_packet,
 610                         skimmed_fee_msat: None,
 611                         blinding_point: None,
 612                 }
 613         }
 614
 615         fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
 616                 SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
 617                 Vec<RouteHop>, u64, PaymentSecret,
 618         ) {
 619                 let session_priv_bytes = [42; 32];
 620                 let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
 621                 let total_amt_msat = 1000;
 622                 let cur_height = 1000;
 623                 let pay_secret = PaymentSecret([99; 32]);
 624                 let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
 625                 let preimage_bytes = [43; 32];
 626                 let preimage = PaymentPreimage(preimage_bytes);
 627                 let rhash_bytes = Sha256::hash(&preimage_bytes).to_byte_array();
 628                 let payment_hash = PaymentHash(rhash_bytes);
 629                 let prng_seed = [44; 32];
 630
 631                 // make a route alice -> bob -> charlie
 632                 let hop_fee = 1;
 633                 let recipient_amount = total_amt_msat - hop_fee;
 634                 let hops = vec![
 635                         RouteHop {
 636                                 pubkey: hop_pk,
 637                                 fee_msat: hop_fee,
 638                                 cltv_expiry_delta: 42,
 639                                 short_channel_id: 1,
 640                                 node_features: NodeFeatures::empty(),
 641                                 channel_features: ChannelFeatures::empty(),
 642                                 maybe_announced_channel: false,
 643                         },
 644                         RouteHop {
 645                                 pubkey: recipient_pk,
 646                                 fee_msat: recipient_amount,
 647                                 cltv_expiry_delta: 42,
 648                                 short_channel_id: 2,
 649                                 node_features: NodeFeatures::empty(),
 650                                 channel_features: ChannelFeatures::empty(),
 651                                 maybe_announced_channel: false,
 652                         }
 653                 ];
 654
 655                 (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
 656                         prng_seed, hops, recipient_amount, pay_secret)
 657         }
 658
 659 }