Compute aggregated BlindedPayInfo in path construction

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Valentine Wallace 2023-06-20 20:27:57 -04:00
parent 911113814f
commit ec01d7e061
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GPG key ID: FD3E106A2CE099B4
2 changed files with 121 additions and 5 deletions

View file

@ -15,8 +15,9 @@ pub(crate) mod utils;
use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
use crate::sign::EntropySource;
use crate::ln::msgs::DecodeError;
use crate::offers::invoice::BlindedPayInfo;
use crate::sign::EntropySource;
use crate::util::ser::{Readable, Writeable, Writer};
use crate::io;
@ -77,22 +78,28 @@ impl BlindedPath {
/// Create a blinded path for a payment, to be forwarded along `intermediate_nodes`.
///
/// Errors if a provided node id is invalid.
/// Errors if:
/// * a provided node id is invalid
/// * [`BlindedPayInfo`] calculation results in an integer overflow
/// * any unknown features are required in the provided [`ForwardTlvs`]
///
/// [`ForwardTlvs`]: crate::blinded_path::payment::ForwardTlvs
// TODO: make all payloads the same size with padding + add dummy hops
pub fn new_for_payment<ES: EntropySource, T: secp256k1::Signing + secp256k1::Verification>(
intermediate_nodes: &[(PublicKey, payment::ForwardTlvs)], payee_node_id: PublicKey,
payee_tlvs: payment::ReceiveTlvs, entropy_source: &ES, secp_ctx: &Secp256k1<T>
) -> Result<Self, ()> {
) -> Result<(BlindedPayInfo, Self), ()> {
let blinding_secret_bytes = entropy_source.get_secure_random_bytes();
let blinding_secret = SecretKey::from_slice(&blinding_secret_bytes[..]).expect("RNG is busted");
Ok(BlindedPath {
let blinded_payinfo = payment::compute_payinfo(intermediate_nodes, &payee_tlvs)?;
Ok((blinded_payinfo, BlindedPath {
introduction_node_id: intermediate_nodes.first().map_or(payee_node_id, |n| n.0),
blinding_point: PublicKey::from_secret_key(secp_ctx, &blinding_secret),
blinded_hops: payment::blinded_hops(
secp_ctx, intermediate_nodes, payee_node_id, payee_tlvs, &blinding_secret
).map_err(|_| ())?,
})
}))
}
}

View file

@ -10,9 +10,12 @@ use crate::io;
use crate::ln::PaymentSecret;
use crate::ln::features::BlindedHopFeatures;
use crate::ln::msgs::DecodeError;
use crate::offers::invoice::BlindedPayInfo;
use crate::prelude::*;
use crate::util::ser::{Readable, Writeable, Writer};
use core::convert::TryFrom;
/// Data to construct a [`BlindedHop`] for forwarding a payment.
pub struct ForwardTlvs {
/// The short channel id this payment should be forwarded out over.
@ -150,6 +153,46 @@ pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
}
pub(super) fn compute_payinfo(
intermediate_nodes: &[(PublicKey, ForwardTlvs)], payee_tlvs: &ReceiveTlvs
) -> Result<BlindedPayInfo, ()> {
let mut curr_base_fee: u64 = 0;
let mut curr_prop_mil: u64 = 0;
let mut cltv_expiry_delta: u16 = 0;
for (_, tlvs) in intermediate_nodes.iter().rev() {
// In the future, we'll want to take the intersection of all supported features for the
// `BlindedPayInfo`, but there are no features in that context right now.
if tlvs.features.requires_unknown_bits_from(&BlindedHopFeatures::empty()) { return Err(()) }
let next_base_fee = tlvs.payment_relay.fee_base_msat as u64;
let next_prop_mil = tlvs.payment_relay.fee_proportional_millionths as u64;
// Use integer arithmetic to compute `ceil(a/b)` as `(a+b-1)/b`
// ((curr_base_fee * (1_000_000 + next_prop_mil)) / 1_000_000) + next_base_fee
curr_base_fee = curr_base_fee.checked_mul(1_000_000 + next_prop_mil)
.and_then(|f| f.checked_add(1_000_000 - 1))
.map(|f| f / 1_000_000)
.and_then(|f| f.checked_add(next_base_fee))
.ok_or(())?;
// ceil(((curr_prop_mil + 1_000_000) * (next_prop_mil + 1_000_000)) / 1_000_000) - 1_000_000
curr_prop_mil = curr_prop_mil.checked_add(1_000_000)
.and_then(|f1| next_prop_mil.checked_add(1_000_000).and_then(|f2| f2.checked_mul(f1)))
.and_then(|f| f.checked_add(1_000_000 - 1))
.map(|f| f / 1_000_000)
.and_then(|f| f.checked_sub(1_000_000))
.ok_or(())?;
cltv_expiry_delta = cltv_expiry_delta.checked_add(tlvs.payment_relay.cltv_expiry_delta).ok_or(())?;
}
Ok(BlindedPayInfo {
fee_base_msat: u32::try_from(curr_base_fee).map_err(|_| ())?,
fee_proportional_millionths: u32::try_from(curr_prop_mil).map_err(|_| ())?,
cltv_expiry_delta,
htlc_minimum_msat: 1, // TODO
htlc_maximum_msat: 21_000_000 * 100_000_000 * 1_000, // TODO
features: BlindedHopFeatures::empty(),
})
}
impl_writeable_msg!(PaymentRelay, {
cltv_expiry_delta,
fee_proportional_millionths,
@ -160,3 +203,69 @@ impl_writeable_msg!(PaymentConstraints, {
max_cltv_expiry,
htlc_minimum_msat
}, {});
#[cfg(test)]
mod tests {
use bitcoin::secp256k1::PublicKey;
use crate::blinded_path::payment::{ForwardTlvs, ReceiveTlvs, PaymentConstraints, PaymentRelay};
use crate::ln::PaymentSecret;
use crate::ln::features::BlindedHopFeatures;
#[test]
fn compute_payinfo() {
// Taken from the spec example for aggregating blinded payment info. See
// https://github.com/lightning/bolts/blob/master/proposals/route-blinding.md#blinded-payments
let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
let intermediate_nodes = vec![(dummy_pk, ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 144,
fee_proportional_millionths: 500,
fee_base_msat: 100,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 100,
},
features: BlindedHopFeatures::empty(),
}), (dummy_pk, ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 144,
fee_proportional_millionths: 500,
fee_base_msat: 100,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1_000,
},
features: BlindedHopFeatures::empty(),
})];
let recv_tlvs = ReceiveTlvs {
payment_secret: PaymentSecret([0; 32]),
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
};
let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs).unwrap();
assert_eq!(blinded_payinfo.fee_base_msat, 201);
assert_eq!(blinded_payinfo.fee_proportional_millionths, 1001);
assert_eq!(blinded_payinfo.cltv_expiry_delta, 288);
}
#[test]
fn compute_payinfo_1_hop() {
let recv_tlvs = ReceiveTlvs {
payment_secret: PaymentSecret([0; 32]),
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
};
let blinded_payinfo = super::compute_payinfo(&[], &recv_tlvs).unwrap();
assert_eq!(blinded_payinfo.fee_base_msat, 0);
assert_eq!(blinded_payinfo.fee_proportional_millionths, 0);
assert_eq!(blinded_payinfo.cltv_expiry_delta, 0);
}
}