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Compute aggregated BlindedPayInfo in path construction
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2 changed files with 121 additions and 5 deletions
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@ -15,8 +15,9 @@ pub(crate) mod utils;
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use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
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use crate::sign::EntropySource;
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use crate::ln::msgs::DecodeError;
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use crate::offers::invoice::BlindedPayInfo;
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use crate::sign::EntropySource;
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use crate::util::ser::{Readable, Writeable, Writer};
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use crate::io;
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@ -77,22 +78,28 @@ impl BlindedPath {
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/// Create a blinded path for a payment, to be forwarded along `intermediate_nodes`.
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///
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/// Errors if a provided node id is invalid.
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/// Errors if:
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/// * a provided node id is invalid
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/// * [`BlindedPayInfo`] calculation results in an integer overflow
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/// * any unknown features are required in the provided [`ForwardTlvs`]
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///
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/// [`ForwardTlvs`]: crate::blinded_path::payment::ForwardTlvs
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// TODO: make all payloads the same size with padding + add dummy hops
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pub fn new_for_payment<ES: EntropySource, T: secp256k1::Signing + secp256k1::Verification>(
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intermediate_nodes: &[(PublicKey, payment::ForwardTlvs)], payee_node_id: PublicKey,
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payee_tlvs: payment::ReceiveTlvs, entropy_source: &ES, secp_ctx: &Secp256k1<T>
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) -> Result<Self, ()> {
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) -> Result<(BlindedPayInfo, Self), ()> {
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let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
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let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
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Ok(BlindedPath {
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let blinded_payinfo = payment::compute_payinfo(intermediate_nodes, &payee_tlvs)?;
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Ok((blinded_payinfo, BlindedPath {
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introduction_node_id: intermediate_nodes.first().map_or(payee_node_id, |n| n.0),
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blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
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blinded_hops: payment::blinded_hops(
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secp_ctx, intermediate_nodes, payee_node_id, payee_tlvs, &blinding_secret
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).map_err(|_| ())?,
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})
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}))
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}
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}
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@ -10,9 +10,12 @@ use crate::io;
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use crate::ln::PaymentSecret;
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use crate::ln::features::BlindedHopFeatures;
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use crate::ln::msgs::DecodeError;
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use crate::offers::invoice::BlindedPayInfo;
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use crate::prelude::*;
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use crate::util::ser::{Readable, Writeable, Writer};
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use core::convert::TryFrom;
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/// Data to construct a [`BlindedHop`] for forwarding a payment.
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pub struct ForwardTlvs {
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/// The short channel id this payment should be forwarded out over.
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@ -150,6 +153,46 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
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utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
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}
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pub(super) fn compute_payinfo(
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intermediate_nodes: &[(PublicKey, ForwardTlvs)], payee_tlvs: &ReceiveTlvs
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) -> Result<BlindedPayInfo, ()> {
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let mut curr_base_fee: u64 = 0;
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let mut curr_prop_mil: u64 = 0;
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let mut cltv_expiry_delta: u16 = 0;
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for (_, tlvs) in intermediate_nodes.iter().rev() {
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// In the future, we'll want to take the intersection of all supported features for the
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// `BlindedPayInfo`, but there are no features in that context right now.
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if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
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let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
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let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
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// Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
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// ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
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curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
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.and_then(|f| f.checked_add(1_000_000 - 1))
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.map(|f| f / 1_000_000)
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.and_then(|f| f.checked_add(next_base_fee))
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.ok_or(())?;
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// ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
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curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
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.and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
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.and_then(|f| f.checked_add(1_000_000 - 1))
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.map(|f| f / 1_000_000)
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.and_then(|f| f.checked_sub(1_000_000))
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.ok_or(())?;
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cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
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}
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Ok(BlindedPayInfo {
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fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
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fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
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cltv_expiry_delta,
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htlc_minimum_msat: 1, // TODO
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htlc_maximum_msat: 21_000_000 * 100_000_000 * 1_000, // TODO
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features: BlindedHopFeatures::empty(),
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})
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}
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impl_writeable_msg!(PaymentRelay, {
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cltv_expiry_delta,
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fee_proportional_millionths,
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@ -160,3 +203,69 @@ impl_writeable_msg!(PaymentConstraints, {
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max_cltv_expiry,
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htlc_minimum_msat
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}, {});
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#[cfg(test)]
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mod tests {
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use bitcoin::secp256k1::PublicKey;
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use crate::blinded_path::payment::{ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentRelay};
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use crate::ln::PaymentSecret;
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use crate::ln::features::BlindedHopFeatures;
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#[test]
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fn compute_payinfo() {
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// Taken from the spec example for aggregating blinded payment info. See
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// https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
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let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
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let intermediate_nodes = vec![(dummy_pk, ForwardTlvs {
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short_channel_id: 0,
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payment_relay: PaymentRelay {
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cltv_expiry_delta: 144,
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fee_proportional_millionths: 500,
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fee_base_msat: 100,
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},
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payment_constraints: PaymentConstraints {
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max_cltv_expiry: 0,
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htlc_minimum_msat: 100,
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},
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features: BlindedHopFeatures::empty(),
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}), (dummy_pk, ForwardTlvs {
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short_channel_id: 0,
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payment_relay: PaymentRelay {
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cltv_expiry_delta: 144,
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fee_proportional_millionths: 500,
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fee_base_msat: 100,
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},
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payment_constraints: PaymentConstraints {
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max_cltv_expiry: 0,
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htlc_minimum_msat: 1_000,
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},
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features: BlindedHopFeatures::empty(),
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})];
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let recv_tlvs = ReceiveTlvs {
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payment_secret: PaymentSecret([0; 32]),
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payment_constraints: PaymentConstraints {
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max_cltv_expiry: 0,
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htlc_minimum_msat: 1,
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},
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};
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let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs).unwrap();
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assert_eq!(blinded_payinfo.fee_base_msat, 201);
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assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
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assert_eq!(blinded_payinfo.cltv_expiry_delta, 288);
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}
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#[test]
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fn compute_payinfo_1_hop() {
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let recv_tlvs = ReceiveTlvs {
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payment_secret: PaymentSecret([0; 32]),
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payment_constraints: PaymentConstraints {
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max_cltv_expiry: 0,
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htlc_minimum_msat: 1,
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},
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};
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let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs).unwrap();
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assert_eq!(blinded_payinfo.fee_base_msat, 0);
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assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
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assert_eq!(blinded_payinfo.cltv_expiry_delta, 0);
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}
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}
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