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Merge pull request #2514 from valentinewallace/2023-08-compute-blindedpayinfo

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Aggregate `BlindedPayInfo` for blinded routes
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Matt Corallo 2023-09-10 03:02:22 +00:00 • committed by GitHub
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2 changed files with 382 additions and 38 deletions
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27
lightning/src/blinded_path/mod.rs
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;
@ -75,25 +76,31 @@ impl BlindedPath {
})
}
/// Create a blinded path for a payment, to be forwarded along `path`. The last node
/// in `path` will be the destination node.
/// Create a blinded path for a payment, to be forwarded along `intermediate_nodes`.
///
/// Errors if `path` is empty or a node id in `path` 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, ()> {
intermediate_nodes: &[payment::ForwardNode], payee_node_id: PublicKey,
payee_tlvs: payment::ReceiveTlvs, htlc_maximum_msat: u64, entropy_source: &ES,
secp_ctx: &Secp256k1<T>
) -> 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 {
introduction_node_id: intermediate_nodes.first().map_or(payee_node_id, |n| n.0),
let blinded_payinfo = payment::compute_payinfo(intermediate_nodes, &payee_tlvs, htlc_maximum_msat)?;
Ok((blinded_payinfo, BlindedPath {
introduction_node_id: intermediate_nodes.first().map_or(payee_node_id, |n| n.node_id),
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(|_| ())?,
})
}))
}
}

393
lightning/src/blinded_path/payment.rs
View file

@ -10,31 +10,48 @@ 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;
/// An intermediate node, its outbound channel, and relay parameters.
#[derive(Clone, Debug)]
pub struct ForwardNode {
/// The TLVs for this node's [`BlindedHop`], where the fee parameters contained within are also
/// used for [`BlindedPayInfo`] construction.
pub tlvs: ForwardTlvs,
/// This node's pubkey.
pub node_id: PublicKey,
/// The maximum value, in msat, that may be accepted by this node.
pub htlc_maximum_msat: u64,
}
/// Data to construct a [`BlindedHop`] for forwarding a payment.
#[derive(Clone, Debug)]
pub struct ForwardTlvs {
/// The short channel id this payment should be forwarded out over.
short_channel_id: u64,
pub short_channel_id: u64,
/// Payment parameters for relaying over [`Self::short_channel_id`].
payment_relay: PaymentRelay,
pub payment_relay: PaymentRelay,
/// Payment constraints for relaying over [`Self::short_channel_id`].
payment_constraints: PaymentConstraints,
pub payment_constraints: PaymentConstraints,
/// Supported and required features when relaying a payment onion containing this object's
/// corresponding [`BlindedHop::encrypted_payload`].
///
/// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
features: BlindedHopFeatures,
pub features: BlindedHopFeatures,
}
/// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
/// may not be valid if received by another lightning implementation.
#[derive(Clone, Debug)]
pub struct ReceiveTlvs {
/// Used to authenticate the sender of a payment to the receiver and tie MPP HTLCs together.
payment_secret: PaymentSecret,
pub payment_secret: PaymentSecret,
/// Constraints for the receiver of this payment.
payment_constraints: PaymentConstraints,
pub payment_constraints: PaymentConstraints,
}
/// Data to construct a [`BlindedHop`] for sending a payment over.
@ -56,46 +73,51 @@ enum BlindedPaymentTlvsRef<'a> {
/// Parameters for relaying over a given [`BlindedHop`].
///
/// [`BlindedHop`]: crate::blinded_path::BlindedHop
#[derive(Clone, Debug)]
pub struct PaymentRelay {
/// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
///
///[`BlindedHop`]: crate::blinded_path::BlindedHop
pub cltv_expiry_delta: u16,
/// Liquidity fee charged (in millionths of the amount transferred) for relaying a payment over
/// this [`BlindedHop`], (i.e., 10,000 is 1%).
///
///[`BlindedHop`]: crate::blinded_path::BlindedHop
pub fee_proportional_millionths: u32,
/// Base fee charged (in millisatoshi) for relaying a payment over this [`BlindedHop`].
///
///[`BlindedHop`]: crate::blinded_path::BlindedHop
pub fee_base_msat: u32,
}
/// Constraints for relaying over a given [`BlindedHop`].
///
/// [`BlindedHop`]: crate::blinded_path::BlindedHop
#[derive(Clone, Debug)]
pub struct PaymentConstraints {
/// The maximum total CLTV delta that is acceptable when relaying a payment over this
/// [`BlindedHop`].
///
///[`BlindedHop`]: crate::blinded_path::BlindedHop
pub max_cltv_expiry: u32,
/// The minimum value, in msat, that may be relayed over this [`BlindedHop`].
/// The minimum value, in msat, that may be accepted by the node corresponding to this
/// [`BlindedHop`].
pub htlc_minimum_msat: u64,
}
impl_writeable_tlv_based!(ForwardTlvs, {
(2, short_channel_id, required),
(10, payment_relay, required),
(12, payment_constraints, required),
(14, features, required),
});
impl Writeable for ForwardTlvs {
fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
encode_tlv_stream!(w, {
(2, self.short_channel_id, required),
(10, self.payment_relay, required),
(12, self.payment_constraints, required),
(14, self.features, required)
});
Ok(())
}
}
impl_writeable_tlv_based!(ReceiveTlvs, {
(12, payment_constraints, required),
(65536, payment_secret, required),
});
impl Writeable for ReceiveTlvs {
fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
encode_tlv_stream!(w, {
(12, self.payment_constraints, required),
(65536, self.payment_secret, required)
});
Ok(())
}
}
impl<'a> Writeable for BlindedPaymentTlvsRef<'a> {
fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
@ -140,16 +162,98 @@ impl Readable for BlindedPaymentTlvs {
/// Construct blinded payment hops for the given `intermediate_nodes` and payee info.
pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
secp_ctx: &Secp256k1<T>, intermediate_nodes: &[(PublicKey, ForwardTlvs)],
secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode],
payee_node_id: PublicKey, payee_tlvs: ReceiveTlvs, session_priv: &SecretKey
) -> Result<Vec<BlindedHop>, secp256k1::Error> {
let pks = intermediate_nodes.iter().map(|(pk, _)| pk)
let pks = intermediate_nodes.iter().map(|node| &node.node_id)
.chain(core::iter::once(&payee_node_id));
let tlvs = intermediate_nodes.iter().map(|(_, tlvs)| BlindedPaymentTlvsRef::Forward(tlvs))
let tlvs = intermediate_nodes.iter().map(|node| BlindedPaymentTlvsRef::Forward(&node.tlvs))
.chain(core::iter::once(BlindedPaymentTlvsRef::Receive(&payee_tlvs)));
utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
}
/// `None` if underflow occurs.
fn amt_to_forward_msat(inbound_amt_msat: u64, payment_relay: &PaymentRelay) -> Option<u64> {
let inbound_amt = inbound_amt_msat as u128;
let base = payment_relay.fee_base_msat as u128;
let prop = payment_relay.fee_proportional_millionths as u128;
let post_base_fee_inbound_amt =
if let Some(amt) = inbound_amt.checked_sub(base) { amt } else { return None };
let mut amt_to_forward =
(post_base_fee_inbound_amt * 1_000_000 + 1_000_000 + prop - 1) / (prop + 1_000_000);
let fee = ((amt_to_forward * prop) / 1_000_000) + base;
if inbound_amt - fee < amt_to_forward {
// Rounding up the forwarded amount resulted in underpaying this node, so take an extra 1 msat
// in fee to compensate.
amt_to_forward -= 1;
}
debug_assert_eq!(amt_to_forward + fee, inbound_amt);
u64::try_from(amt_to_forward).ok()
}
pub(super) fn compute_payinfo(
intermediate_nodes: &[ForwardNode], payee_tlvs: &ReceiveTlvs, payee_htlc_maximum_msat: u64
) -> 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().map(|n| &n.tlvs) {
// 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(())?;
}
let mut htlc_minimum_msat: u64 = 1;
let mut htlc_maximum_msat: u64 = 21_000_000 * 100_000_000 * 1_000; // Total bitcoin supply
for node in intermediate_nodes.iter() {
// The min htlc for an intermediate node is that node's min minus the fees charged by all of the
// following hops for forwarding that min, since that fee amount will automatically be included
// in the amount that this node receives and contribute towards reaching its min.
htlc_minimum_msat = amt_to_forward_msat(
core::cmp::max(node.tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat),
&node.tlvs.payment_relay
).unwrap_or(1); // If underflow occurs, we definitely reached this node's min
htlc_maximum_msat = amt_to_forward_msat(
core::cmp::min(node.htlc_maximum_msat, htlc_maximum_msat), &node.tlvs.payment_relay
).ok_or(())?; // If underflow occurs, we cannot send to this hop without exceeding their max
}
htlc_minimum_msat = core::cmp::max(
payee_tlvs.payment_constraints.htlc_minimum_msat, htlc_minimum_msat
);
htlc_maximum_msat = core::cmp::min(payee_htlc_maximum_msat, htlc_maximum_msat);
if htlc_maximum_msat < htlc_minimum_msat { return Err(()) }
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,
htlc_maximum_msat,
features: BlindedHopFeatures::empty(),
})
}
impl_writeable_msg!(PaymentRelay, {
cltv_expiry_delta,
fee_proportional_millionths,
@ -160,3 +264,236 @@ impl_writeable_msg!(PaymentConstraints, {
max_cltv_expiry,
htlc_minimum_msat
}, {});
#[cfg(test)]
mod tests {
use bitcoin::secp256k1::PublicKey;
use crate::blinded_path::payment::{ForwardNode, 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![ForwardNode {
node_id: dummy_pk,
tlvs: 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(),
},
htlc_maximum_msat: u64::max_value(),
}, ForwardNode {
node_id: dummy_pk,
tlvs: 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(),
},
htlc_maximum_msat: u64::max_value(),
}];
let recv_tlvs = ReceiveTlvs {
payment_secret: PaymentSecret([0; 32]),
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
};
let htlc_maximum_msat = 100_000;
let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).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);
assert_eq!(blinded_payinfo.htlc_minimum_msat, 900);
assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
}
#[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, 4242).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);
assert_eq!(blinded_payinfo.htlc_minimum_msat, 1);
assert_eq!(blinded_payinfo.htlc_maximum_msat, 4242);
}
#[test]
fn simple_aggregated_htlc_min() {
// If no hops charge fees, the htlc_minimum_msat should just be the maximum htlc_minimum_msat
// along the path.
let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
let intermediate_nodes = vec![ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 0,
fee_base_msat: 0,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
}, ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 0,
fee_base_msat: 0,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 2_000,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
}];
let recv_tlvs = ReceiveTlvs {
payment_secret: PaymentSecret([0; 32]),
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 3,
},
};
let htlc_maximum_msat = 100_000;
let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).unwrap();
assert_eq!(blinded_payinfo.htlc_minimum_msat, 2_000);
}
#[test]
fn aggregated_htlc_min() {
// Create a path with varying fees and htlc_mins, and make sure htlc_minimum_msat ends up as the
// max (htlc_min - following_fees) along the path.
let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
let intermediate_nodes = vec![ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 500,
fee_base_msat: 1_000,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 5_000,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
}, ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 500,
fee_base_msat: 200,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 2_000,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
}];
let recv_tlvs = ReceiveTlvs {
payment_secret: PaymentSecret([0; 32]),
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
};
let htlc_minimum_msat = 3798;
assert!(super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_minimum_msat - 1).is_err());
let htlc_maximum_msat = htlc_minimum_msat + 1;
let blinded_payinfo = super::compute_payinfo(&intermediate_nodes[..], &recv_tlvs, htlc_maximum_msat).unwrap();
assert_eq!(blinded_payinfo.htlc_minimum_msat, htlc_minimum_msat);
assert_eq!(blinded_payinfo.htlc_maximum_msat, htlc_maximum_msat);
}
#[test]
fn aggregated_htlc_max() {
// Create a path with varying fees and `htlc_maximum_msat`s, and make sure the aggregated max
// htlc ends up as the min (htlc_max - following_fees) along the path.
let dummy_pk = PublicKey::from_slice(&[2; 33]).unwrap();
let intermediate_nodes = vec![ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 500,
fee_base_msat: 1_000,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: 5_000,
}, ForwardNode {
node_id: dummy_pk,
tlvs: ForwardTlvs {
short_channel_id: 0,
payment_relay: PaymentRelay {
cltv_expiry_delta: 0,
fee_proportional_millionths: 500,
fee_base_msat: 1,
},
payment_constraints: PaymentConstraints {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: 10_000
}];
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, 10_000).unwrap();
assert_eq!(blinded_payinfo.htlc_maximum_msat, 3997);
}
}