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Implement route blinding test vectors #3204

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Merged
merged 4 commits into from
Aug 19, 2024
Merged

Implement route blinding test vectors #3204

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f68b124
Support next_blinding_override in blinded payment paths.
valentinewallace Jul 22, 2024
9dba36a
Fix blinded hop feature serialization.
valentinewallace Jul 24, 2024
8739b06
Implement route blinding spec test vectors.
valentinewallace Jul 24, 2024
6f6115f
Avoid && in public API for onion peeling/decoding.
valentinewallace Jul 24, 2024
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1 change: 1 addition & 0 deletions fuzz/src/invoice_request_deser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,7 @@ fn build_response<T: secp256k1::Signing + secp256k1::Verification>(
htlc_minimum_msat: 100,
},
features: BlindedHopFeatures::empty(),
next_blinding_override: None,
},
node_id: pubkey(43),
htlc_maximum_msat: 1_000_000_000_000,
Expand Down
4 changes: 2 additions & 2 deletions fuzz/src/onion_hop_data.rs
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Expand Up @@ -21,7 +21,7 @@ pub fn onion_hop_data_test<Out: test_logger::Output>(data: &[u8], _out: Out) {
let node_signer = test_utils::TestNodeSigner::new(test_utils::privkey(42));
let _ = <lightning::ln::msgs::InboundOnionPayload as ReadableArgs<(
Option<PublicKey>,
&&test_utils::TestNodeSigner,
&test_utils::TestNodeSigner,
)>>::read(&mut r, (None, &&node_signer));
}

Expand All @@ -34,6 +34,6 @@ pub extern "C" fn onion_hop_data_run(data: *const u8, datalen: usize) {
let node_signer = test_utils::TestNodeSigner::new(test_utils::privkey(42));
let _ = <lightning::ln::msgs::InboundOnionPayload as ReadableArgs<(
Option<PublicKey>,
&&test_utils::TestNodeSigner,
&test_utils::TestNodeSigner,
)>>::read(&mut r, (None, &&node_signer));
}
1 change: 1 addition & 0 deletions fuzz/src/refund_deser.rs
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Expand Up @@ -91,6 +91,7 @@ fn build_response<T: secp256k1::Signing + secp256k1::Verification>(
htlc_minimum_msat: 100,
},
features: BlindedHopFeatures::empty(),
next_blinding_override: None,
},
node_id: pubkey(43),
htlc_maximum_msat: 1_000_000_000_000,
Expand Down
23 changes: 18 additions & 5 deletions lightning/src/blinded_path/payment.rs
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Expand Up @@ -26,7 +26,7 @@ use crate::offers::invoice_request::InvoiceRequestFields;
use crate::offers::offer::OfferId;
use crate::routing::gossip::{NodeId, ReadOnlyNetworkGraph};
use crate::sign::{EntropySource, NodeSigner, Recipient};
use crate::util::ser::{FixedLengthReader, LengthReadableArgs, HighZeroBytesDroppedBigSize, Readable, Writeable, Writer};
use crate::util::ser::{FixedLengthReader, LengthReadableArgs, HighZeroBytesDroppedBigSize, Readable, WithoutLength, Writeable, Writer};

use core::mem;
use core::ops::Deref;
Expand Down Expand Up @@ -201,6 +201,9 @@ pub struct ForwardTlvs {
///
/// [`BlindedHop::encrypted_payload`]: crate::blinded_path::BlindedHop::encrypted_payload
pub features: BlindedHopFeatures,
/// Set if this [`BlindedPaymentPath`] is concatenated to another, to indicate the
/// [`BlindedPaymentPath::blinding_point`] of the appended blinded path.
pub next_blinding_override: Option<PublicKey>,
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Why didn't we support this to begin with?

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IIRC I was under the impression that this field only applies to onion messages (it's required for OMs), not payments. And no one actually sets it for payments, so it never popped up in interop testing. :/

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I imagine no one set it ever, because its only useful for some kind of weird frankenstein trampoline afaict? What's the intended usecase for concatenating blinded paths? I mean I suppose we should just do it, but I'm curious why its there.

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@valentinewallace valentinewallace Aug 7, 2024 •
edited
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I think Rusty pointed out here that it can help prevent the intro node from being aware that it's the intro node: lightning/bolts#1182 (comment)? I think this is clarified in lightning/bolts#1182 but still need to review that.

Edit: it is clarified quite a bit in that PR:
Screenshot 2024-08-07 at 3 18 29 PM

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Ah, so basically its saying we should send onion messages as a blinded path from us to the intro node, prepended to the real blinded path? Do we do that?

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Yes, using next_blinding_override in OMs has always been required to prepend the unblinded path to the intro node.

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Oops, I think I misread your message. I'm not sure I follow Rusty's logic, actually. It seems like creating a blinded path from us to the intro node trades off the intro node knowing that they're the intro node for the node prior to the intro node knowing that the next hop is the intro node(?). Unless we set next_blinding_override for every hop in our prepended blinded path, which I suppose is possible.

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Ah, I guess I'm still not really understanding why this is here, but its not much complexity to support, sooooo

}

/// Data to construct a [`BlindedHop`] for receiving a payment. This payload is custom to LDK and
Expand Down Expand Up @@ -234,7 +237,7 @@ enum BlindedPaymentTlvsRef<'a> {
/// Parameters for relaying over a given [`BlindedHop`].
///
/// [`BlindedHop`]: crate::blinded_path::BlindedHop
#[derive(Clone, Debug)]
#[derive(Clone, Debug, PartialEq)]
pub struct PaymentRelay {
/// Number of blocks subtracted from an incoming HTLC's `cltv_expiry` for this [`BlindedHop`].
pub cltv_expiry_delta: u16,
Expand All @@ -248,7 +251,7 @@ pub struct PaymentRelay {
/// Constraints for relaying over a given [`BlindedHop`].
///
/// [`BlindedHop`]: crate::blinded_path::BlindedHop
#[derive(Clone, Debug)]
#[derive(Clone, Debug, PartialEq)]
pub struct PaymentConstraints {
/// The maximum total CLTV that is acceptable when relaying a payment over this [`BlindedHop`].
pub max_cltv_expiry: u32,
Expand Down Expand Up @@ -341,7 +344,7 @@ impl Writeable for ForwardTlvs {
fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
let features_opt =
if self.features == BlindedHopFeatures::empty() { None }
else { Some(&self.features) };
else { Some(WithoutLength(&self.features)) };
encode_tlv_stream!(w, {
(2, self.short_channel_id, required),
(10, self.payment_relay, required),
Expand Down Expand Up @@ -379,9 +382,10 @@ impl Readable for BlindedPaymentTlvs {
_init_and_read_tlv_stream!(r, {
(1, _padding, option),
(2, scid, option),
(8, next_blinding_override, option),
(10, payment_relay, option),
(12, payment_constraints, required),
(14, features, option),
(14, features, (option, encoding: (BlindedHopFeatures, WithoutLength))),
(65536, payment_secret, option),
(65537, payment_context, (default_value, PaymentContext::unknown())),
});
Expand All @@ -395,6 +399,7 @@ impl Readable for BlindedPaymentTlvs {
short_channel_id,
payment_relay: payment_relay.ok_or(DecodeError::InvalidValue)?,
payment_constraints: payment_constraints.0.unwrap(),
next_blinding_override,
features: features.unwrap_or_else(BlindedHopFeatures::empty),
}))
} else {
Expand Down Expand Up @@ -602,6 +607,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 100,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value(),
Expand All @@ -618,6 +624,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 1_000,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value(),
Expand Down Expand Up @@ -675,6 +682,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
Expand All @@ -691,6 +699,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 2_000,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
Expand Down Expand Up @@ -726,6 +735,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 5_000,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
Expand All @@ -742,6 +752,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 2_000,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: u64::max_value()
Expand Down Expand Up @@ -781,6 +792,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: 5_000,
Expand All @@ -797,6 +809,7 @@ mod tests {
max_cltv_expiry: 0,
htlc_minimum_msat: 1,
},
next_blinding_override: None,
features: BlindedHopFeatures::empty(),
},
htlc_maximum_msat: 10_000
Expand Down
2 changes: 1 addition & 1 deletion lightning/src/blinded_path/utils.rs
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Expand Up @@ -109,7 +109,7 @@ where
}

// Panics if `unblinded_tlvs` length is less than `unblinded_pks` length
pub(super) fn construct_blinded_hops<'a, T, I1, I2>(
pub(crate) fn construct_blinded_hops<'a, T, I1, I2>(
secp_ctx: &Secp256k1<T>, unblinded_pks: I1, mut unblinded_tlvs: I2, session_priv: &SecretKey
) -> Result<Vec<BlindedHop>, secp256k1::Error>
where
Expand Down
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