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