1 //! Utilities to decode payment onions and do contextless validation of incoming payments.
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.
6 use bitcoin::hashes::Hash;
7 use bitcoin::hashes::sha256::Hash as Sha256;
8 use bitcoin::secp256k1::{self, Secp256k1, PublicKey};
10 use crate::blinded_path;
11 use crate::blinded_path::payment::{PaymentConstraints, PaymentRelay};
12 use crate::chain::channelmonitor::{HTLC_FAIL_BACK_BUFFER, LATENCY_GRACE_PERIOD_BLOCKS};
13 use crate::ln::PaymentHash;
14 use crate::ln::channelmanager::{BlindedForward, CLTV_FAR_FAR_AWAY, HTLCFailureMsg, MIN_CLTV_EXPIRY_DELTA, PendingHTLCInfo, PendingHTLCRouting};
15 use crate::ln::features::BlindedHopFeatures;
17 use crate::ln::onion_utils;
18 use crate::ln::onion_utils::{HTLCFailReason, INVALID_ONION_BLINDING};
19 use crate::sign::{NodeSigner, Recipient};
20 use crate::util::logger::Logger;
22 use crate::prelude::*;
25 /// Invalid inbound onion payment.
26 pub struct InboundOnionErr {
27 /// BOLT 4 error code.
29 /// Data attached to this error.
30 pub err_data: Vec<u8>,
31 /// Error message text.
32 pub msg: &'static str,
35 fn check_blinded_forward(
36 inbound_amt_msat: u64, inbound_cltv_expiry: u32, payment_relay: &PaymentRelay,
37 payment_constraints: &PaymentConstraints, features: &BlindedHopFeatures
38 ) -> Result<(u64, u32), ()> {
39 let amt_to_forward = blinded_path::payment::amt_to_forward_msat(
40 inbound_amt_msat, payment_relay
42 let outgoing_cltv_value = inbound_cltv_expiry.checked_sub(
43 payment_relay.cltv_expiry_delta as u32
45 if inbound_amt_msat < payment_constraints.htlc_minimum_msat ||
46 outgoing_cltv_value > payment_constraints.max_cltv_expiry
48 if features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
49 Ok((amt_to_forward, outgoing_cltv_value))
52 pub(super) fn create_fwd_pending_htlc_info(
53 msg: &msgs::UpdateAddHTLC, hop_data: msgs::InboundOnionPayload, hop_hmac: [u8; 32],
54 new_packet_bytes: [u8; onion_utils::ONION_DATA_LEN], shared_secret: [u8; 32],
55 next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>
56 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
57 debug_assert!(next_packet_pubkey_opt.is_some());
58 let outgoing_packet = msgs::OnionPacket {
60 public_key: next_packet_pubkey_opt.unwrap_or(Err(secp256k1::Error::InvalidPublicKey)),
61 hop_data: new_packet_bytes,
66 short_channel_id, amt_to_forward, outgoing_cltv_value, inbound_blinding_point
68 msgs::InboundOnionPayload::Forward { short_channel_id, amt_to_forward, outgoing_cltv_value } =>
69 (short_channel_id, amt_to_forward, outgoing_cltv_value, None),
70 msgs::InboundOnionPayload::BlindedForward {
71 short_channel_id, payment_relay, payment_constraints, intro_node_blinding_point, features,
73 let (amt_to_forward, outgoing_cltv_value) = check_blinded_forward(
74 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
76 // We should be returning malformed here if `msg.blinding_point` is set, but this is
77 // unreachable right now since we checked it in `decode_update_add_htlc_onion`.
79 msg: "Underflow calculating outbound amount or cltv value for blinded forward",
80 err_code: INVALID_ONION_BLINDING,
81 err_data: vec![0; 32],
84 (short_channel_id, amt_to_forward, outgoing_cltv_value, Some(intro_node_blinding_point))
86 msgs::InboundOnionPayload::Receive { .. } | msgs::InboundOnionPayload::BlindedReceive { .. } =>
87 return Err(InboundOnionErr {
88 msg: "Final Node OnionHopData provided for us as an intermediary node",
89 err_code: 0x4000 | 22,
95 routing: PendingHTLCRouting::Forward {
96 onion_packet: outgoing_packet,
98 blinded: inbound_blinding_point.map(|bp| BlindedForward { inbound_blinding_point: bp }),
100 payment_hash: msg.payment_hash,
101 incoming_shared_secret: shared_secret,
102 incoming_amt_msat: Some(msg.amount_msat),
103 outgoing_amt_msat: amt_to_forward,
105 skimmed_fee_msat: None,
109 pub(super) fn create_recv_pending_htlc_info(
110 hop_data: msgs::InboundOnionPayload, shared_secret: [u8; 32], payment_hash: PaymentHash,
111 amt_msat: u64, cltv_expiry: u32, phantom_shared_secret: Option<[u8; 32]>, allow_underpay: bool,
112 counterparty_skimmed_fee_msat: Option<u64>, current_height: u32, accept_mpp_keysend: bool,
113 ) -> Result<PendingHTLCInfo, InboundOnionErr> {
114 let (payment_data, keysend_preimage, custom_tlvs, onion_amt_msat, outgoing_cltv_value, payment_metadata) = match hop_data {
115 msgs::InboundOnionPayload::Receive {
116 payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata, ..
118 (payment_data, keysend_preimage, custom_tlvs, amt_msat, outgoing_cltv_value, payment_metadata),
119 msgs::InboundOnionPayload::BlindedReceive {
120 amt_msat, total_msat, outgoing_cltv_value, payment_secret, ..
122 let payment_data = msgs::FinalOnionHopData { payment_secret, total_msat };
123 (Some(payment_data), None, Vec::new(), amt_msat, outgoing_cltv_value, None)
125 msgs::InboundOnionPayload::Forward { .. } => {
126 return Err(InboundOnionErr {
128 err_data: Vec::new(),
129 msg: "Got non final data with an HMAC of 0",
132 msgs::InboundOnionPayload::BlindedForward { .. } => {
133 return Err(InboundOnionErr {
134 err_code: INVALID_ONION_BLINDING,
135 err_data: vec![0; 32],
136 msg: "Got blinded non final data with an HMAC of 0",
140 // final_incorrect_cltv_expiry
141 if outgoing_cltv_value > cltv_expiry {
142 return Err(InboundOnionErr {
143 msg: "Upstream node set CLTV to less than the CLTV set by the sender",
145 err_data: cltv_expiry.to_be_bytes().to_vec()
148 // final_expiry_too_soon
149 // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
150 // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
152 // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
153 // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
154 // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
155 if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
156 let mut err_data = Vec::with_capacity(12);
157 err_data.extend_from_slice(&amt_msat.to_be_bytes());
158 err_data.extend_from_slice(¤t_height.to_be_bytes());
159 return Err(InboundOnionErr {
160 err_code: 0x4000 | 15, err_data,
161 msg: "The final CLTV expiry is too soon to handle",
164 if (!allow_underpay && onion_amt_msat > amt_msat) ||
165 (allow_underpay && onion_amt_msat >
166 amt_msat.saturating_add(counterparty_skimmed_fee_msat.unwrap_or(0)))
168 return Err(InboundOnionErr {
170 err_data: amt_msat.to_be_bytes().to_vec(),
171 msg: "Upstream node sent less than we were supposed to receive in payment",
175 let routing = if let Some(payment_preimage) = keysend_preimage {
176 // We need to check that the sender knows the keysend preimage before processing this
177 // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
178 // could discover the final destination of X, by probing the adjacent nodes on the route
179 // with a keysend payment of identical payment hash to X and observing the processing
180 // time discrepancies due to a hash collision with X.
181 let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).to_byte_array());
182 if hashed_preimage != payment_hash {
183 return Err(InboundOnionErr {
185 err_data: Vec::new(),
186 msg: "Payment preimage didn't match payment hash",
189 if !accept_mpp_keysend && payment_data.is_some() {
190 return Err(InboundOnionErr {
192 err_data: Vec::new(),
193 msg: "We don't support MPP keysend payments",
196 PendingHTLCRouting::ReceiveKeysend {
200 incoming_cltv_expiry: outgoing_cltv_value,
203 } else if let Some(data) = payment_data {
204 PendingHTLCRouting::Receive {
207 incoming_cltv_expiry: outgoing_cltv_value,
208 phantom_shared_secret,
212 return Err(InboundOnionErr {
213 err_code: 0x4000|0x2000|3,
214 err_data: Vec::new(),
215 msg: "We require payment_secrets",
221 incoming_shared_secret: shared_secret,
222 incoming_amt_msat: Some(amt_msat),
223 outgoing_amt_msat: onion_amt_msat,
225 skimmed_fee_msat: counterparty_skimmed_fee_msat,
229 /// Peel one layer off an incoming onion, returning a [`PendingHTLCInfo`] that contains information
230 /// about the intended next-hop for the HTLC.
232 /// This does all the relevant context-free checks that LDK requires for payment relay or
233 /// acceptance. If the payment is to be received, and the amount matches the expected amount for
234 /// a given invoice, this indicates the [`msgs::UpdateAddHTLC`], once fully committed in the
235 /// channel, will generate an [`Event::PaymentClaimable`].
237 /// [`Event::PaymentClaimable`]: crate::events::Event::PaymentClaimable
238 pub fn peel_payment_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
239 msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
240 cur_height: u32, accept_mpp_keysend: bool, allow_skimmed_fees: bool,
241 ) -> Result<PendingHTLCInfo, InboundOnionErr>
243 NS::Target: NodeSigner,
246 let (hop, shared_secret, next_packet_details_opt) =
247 decode_incoming_update_add_htlc_onion(msg, node_signer, logger, secp_ctx
249 let (err_code, err_data) = match e {
250 HTLCFailureMsg::Malformed(m) => (m.failure_code, Vec::new()),
251 HTLCFailureMsg::Relay(r) => (0x4000 | 22, r.reason.data),
253 let msg = "Failed to decode update add htlc onion";
254 InboundOnionErr { msg, err_code, err_data }
257 onion_utils::Hop::Forward { next_hop_data, next_hop_hmac, new_packet_bytes } => {
258 let NextPacketDetails {
259 next_packet_pubkey, outgoing_amt_msat: _, outgoing_scid: _, outgoing_cltv_value
260 } = match next_packet_details_opt {
261 Some(next_packet_details) => next_packet_details,
262 // Forward should always include the next hop details
263 None => return Err(InboundOnionErr {
264 msg: "Failed to decode update add htlc onion",
265 err_code: 0x4000 | 22,
266 err_data: Vec::new(),
270 if let Err((err_msg, code)) = check_incoming_htlc_cltv(
271 cur_height, outgoing_cltv_value, msg.cltv_expiry
273 return Err(InboundOnionErr {
276 err_data: Vec::new(),
280 // TODO: If this is potentially a phantom payment we should decode the phantom payment
281 // onion here and check it.
283 create_fwd_pending_htlc_info(
284 msg, next_hop_data, next_hop_hmac, new_packet_bytes, shared_secret,
285 Some(next_packet_pubkey)
288 onion_utils::Hop::Receive(received_data) => {
289 create_recv_pending_htlc_info(
290 received_data, shared_secret, msg.payment_hash, msg.amount_msat, msg.cltv_expiry,
291 None, allow_skimmed_fees, msg.skimmed_fee_msat, cur_height, accept_mpp_keysend,
297 pub(super) struct NextPacketDetails {
298 pub(super) next_packet_pubkey: Result<PublicKey, secp256k1::Error>,
299 pub(super) outgoing_scid: u64,
300 pub(super) outgoing_amt_msat: u64,
301 pub(super) outgoing_cltv_value: u32,
304 pub(super) fn decode_incoming_update_add_htlc_onion<NS: Deref, L: Deref, T: secp256k1::Verification>(
305 msg: &msgs::UpdateAddHTLC, node_signer: &NS, logger: &L, secp_ctx: &Secp256k1<T>,
306 ) -> Result<(onion_utils::Hop, [u8; 32], Option<NextPacketDetails>), HTLCFailureMsg>
308 NS::Target: NodeSigner,
311 macro_rules! return_malformed_err {
312 ($msg: expr, $err_code: expr) => {
314 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
315 return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
316 channel_id: msg.channel_id,
317 htlc_id: msg.htlc_id,
318 sha256_of_onion: Sha256::hash(&msg.onion_routing_packet.hop_data).to_byte_array(),
319 failure_code: $err_code,
325 if let Err(_) = msg.onion_routing_packet.public_key {
326 return_malformed_err!("invalid ephemeral pubkey", 0x8000 | 0x4000 | 6);
329 let shared_secret = node_signer.ecdh(
330 Recipient::Node, &msg.onion_routing_packet.public_key.unwrap(), None
331 ).unwrap().secret_bytes();
333 if msg.onion_routing_packet.version != 0 {
334 //TODO: Spec doesn't indicate if we should only hash hop_data here (and in other
335 //sha256_of_onion error data packets), or the entire onion_routing_packet. Either way,
336 //the hash doesn't really serve any purpose - in the case of hashing all data, the
337 //receiving node would have to brute force to figure out which version was put in the
338 //packet by the node that send us the message, in the case of hashing the hop_data, the
339 //node knows the HMAC matched, so they already know what is there...
340 return_malformed_err!("Unknown onion packet version", 0x8000 | 0x4000 | 4);
342 macro_rules! return_err {
343 ($msg: expr, $err_code: expr, $data: expr) => {
345 log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
346 return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
347 channel_id: msg.channel_id,
348 htlc_id: msg.htlc_id,
349 reason: HTLCFailReason::reason($err_code, $data.to_vec())
350 .get_encrypted_failure_packet(&shared_secret, &None),
356 let next_hop = match onion_utils::decode_next_payment_hop(
357 shared_secret, &msg.onion_routing_packet.hop_data[..], msg.onion_routing_packet.hmac,
358 msg.payment_hash, node_signer
361 Err(onion_utils::OnionDecodeErr::Malformed { err_msg, err_code }) => {
362 return_malformed_err!(err_msg, err_code);
364 Err(onion_utils::OnionDecodeErr::Relay { err_msg, err_code }) => {
365 return_err!(err_msg, err_code, &[0; 0]);
369 let next_packet_details = match next_hop {
370 onion_utils::Hop::Forward {
371 next_hop_data: msgs::InboundOnionPayload::Forward {
372 short_channel_id, amt_to_forward, outgoing_cltv_value
375 let next_packet_pubkey = onion_utils::next_hop_pubkey(secp_ctx,
376 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
378 next_packet_pubkey, outgoing_scid: short_channel_id,
379 outgoing_amt_msat: amt_to_forward, outgoing_cltv_value
382 onion_utils::Hop::Forward {
383 next_hop_data: msgs::InboundOnionPayload::BlindedForward {
384 short_channel_id, ref payment_relay, ref payment_constraints, ref features, ..
387 let (amt_to_forward, outgoing_cltv_value) = match check_blinded_forward(
388 msg.amount_msat, msg.cltv_expiry, &payment_relay, &payment_constraints, &features
390 Ok((amt, cltv)) => (amt, cltv),
392 return_err!("Underflow calculating outbound amount or cltv value for blinded forward",
393 INVALID_ONION_BLINDING, &[0; 32]);
396 let next_packet_pubkey = onion_utils::next_hop_pubkey(&secp_ctx,
397 msg.onion_routing_packet.public_key.unwrap(), &shared_secret);
399 next_packet_pubkey, outgoing_scid: short_channel_id, outgoing_amt_msat: amt_to_forward,
403 onion_utils::Hop::Receive { .. } => return Ok((next_hop, shared_secret, None)),
404 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::Receive { .. }, .. } |
405 onion_utils::Hop::Forward { next_hop_data: msgs::InboundOnionPayload::BlindedReceive { .. }, .. } =>
407 return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0; 0]);
411 Ok((next_hop, shared_secret, Some(next_packet_details)))
414 pub(super) fn check_incoming_htlc_cltv(
415 cur_height: u32, outgoing_cltv_value: u32, cltv_expiry: u32
416 ) -> Result<(), (&'static str, u16)> {
417 if (cltv_expiry as u64) < (outgoing_cltv_value) as u64 + MIN_CLTV_EXPIRY_DELTA as u64 {
419 "Forwarding node has tampered with the intended HTLC values or origin node has an obsolete cltv_expiry_delta",
420 0x1000 | 13, // incorrect_cltv_expiry
423 // Theoretically, channel counterparty shouldn't send us a HTLC expiring now,
424 // but we want to be robust wrt to counterparty packet sanitization (see
425 // HTLC_FAIL_BACK_BUFFER rationale).
426 if cltv_expiry <= cur_height + HTLC_FAIL_BACK_BUFFER as u32 { // expiry_too_soon
427 return Err(("CLTV expiry is too close", 0x1000 | 14));
429 if cltv_expiry > cur_height + CLTV_FAR_FAR_AWAY as u32 { // expiry_too_far
430 return Err(("CLTV expiry is too far in the future", 21));
432 // If the HTLC expires ~now, don't bother trying to forward it to our
433 // counterparty. They should fail it anyway, but we don't want to bother with
434 // the round-trips or risk them deciding they definitely want the HTLC and
435 // force-closing to ensure they get it if we're offline.
436 // We previously had a much more aggressive check here which tried to ensure
437 // our counterparty receives an HTLC which has *our* risk threshold met on it,
438 // but there is no need to do that, and since we're a bit conservative with our
439 // risk threshold it just results in failing to forward payments.
440 if (outgoing_cltv_value) as u64 <= (cur_height + LATENCY_GRACE_PERIOD_BLOCKS) as u64 {
441 return Err(("Outgoing CLTV value is too soon", 0x1000 | 14));
449 use bitcoin::hashes::Hash;
450 use bitcoin::hashes::sha256::Hash as Sha256;
451 use bitcoin::secp256k1::{PublicKey, SecretKey};
452 use crate::ln::{PaymentPreimage, PaymentHash, PaymentSecret};
453 use crate::ln::ChannelId;
454 use crate::ln::channelmanager::RecipientOnionFields;
455 use crate::ln::features::{ChannelFeatures, NodeFeatures};
457 use crate::ln::onion_utils::create_payment_onion;
458 use crate::routing::router::{Path, RouteHop};
459 use crate::util::test_utils;
462 fn test_peel_payment_onion() {
464 let secp_ctx = Secp256k1::new();
466 let bob = crate::sign::KeysManager::new(&[2; 32], 42, 42);
467 let bob_pk = PublicKey::from_secret_key(&secp_ctx, &bob.get_node_secret_key());
468 let charlie = crate::sign::KeysManager::new(&[3; 32], 42, 42);
469 let charlie_pk = PublicKey::from_secret_key(&secp_ctx, &charlie.get_node_secret_key());
471 let (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
472 prng_seed, hops, recipient_amount, pay_secret) = payment_onion_args(bob_pk, charlie_pk);
479 let (onion, amount_msat, cltv_expiry) = create_payment_onion(
480 &secp_ctx, &path, &session_priv, total_amt_msat, recipient_onion, cur_height,
481 &payment_hash, &Some(preimage), prng_seed
484 let msg = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, onion);
485 let logger = test_utils::TestLogger::with_id("bob".to_string());
487 let peeled = peel_payment_onion(&msg, &&bob, &&logger, &secp_ctx, cur_height, true, false)
488 .map_err(|e| e.msg).unwrap();
490 let next_onion = match peeled.routing {
491 PendingHTLCRouting::Forward { onion_packet, .. } => {
494 _ => panic!("expected a forwarded onion"),
497 let msg2 = make_update_add_msg(amount_msat, cltv_expiry, payment_hash, next_onion);
498 let peeled2 = peel_payment_onion(&msg2, &&charlie, &&logger, &secp_ctx, cur_height, true, false)
499 .map_err(|e| e.msg).unwrap();
501 match peeled2.routing {
502 PendingHTLCRouting::ReceiveKeysend { payment_preimage, payment_data, incoming_cltv_expiry, .. } => {
503 assert_eq!(payment_preimage, preimage);
504 assert_eq!(peeled2.outgoing_amt_msat, recipient_amount);
505 assert_eq!(incoming_cltv_expiry, peeled2.outgoing_cltv_value);
506 let msgs::FinalOnionHopData{total_msat, payment_secret} = payment_data.unwrap();
507 assert_eq!(total_msat, total_amt_msat);
508 assert_eq!(payment_secret, pay_secret);
510 _ => panic!("expected a received keysend"),
514 fn make_update_add_msg(
515 amount_msat: u64, cltv_expiry: u32, payment_hash: PaymentHash,
516 onion_routing_packet: msgs::OnionPacket
517 ) -> msgs::UpdateAddHTLC {
518 msgs::UpdateAddHTLC {
519 channel_id: ChannelId::from_bytes([0; 32]),
524 onion_routing_packet,
525 skimmed_fee_msat: None,
526 blinding_point: None,
530 fn payment_onion_args(hop_pk: PublicKey, recipient_pk: PublicKey) -> (
531 SecretKey, u64, u32, RecipientOnionFields, PaymentPreimage, PaymentHash, [u8; 32],
532 Vec<RouteHop>, u64, PaymentSecret,
534 let session_priv_bytes = [42; 32];
535 let session_priv = SecretKey::from_slice(&session_priv_bytes).unwrap();
536 let total_amt_msat = 1000;
537 let cur_height = 1000;
538 let pay_secret = PaymentSecret([99; 32]);
539 let recipient_onion = RecipientOnionFields::secret_only(pay_secret);
540 let preimage_bytes = [43; 32];
541 let preimage = PaymentPreimage(preimage_bytes);
542 let rhash_bytes = Sha256::hash(&preimage_bytes).to_byte_array();
543 let payment_hash = PaymentHash(rhash_bytes);
544 let prng_seed = [44; 32];
546 // make a route alice -> bob -> charlie
548 let recipient_amount = total_amt_msat - hop_fee;
553 cltv_expiry_delta: 42,
555 node_features: NodeFeatures::empty(),
556 channel_features: ChannelFeatures::empty(),
557 maybe_announced_channel: false,
560 pubkey: recipient_pk,
561 fee_msat: recipient_amount,
562 cltv_expiry_delta: 42,
564 node_features: NodeFeatures::empty(),
565 channel_features: ChannelFeatures::empty(),
566 maybe_announced_channel: false,
570 (session_priv, total_amt_msat, cur_height, recipient_onion, preimage, payment_hash,
571 prng_seed, hops, recipient_amount, pay_secret)