Use consistent cltv_expiry_delta in ForwardTlvs

When converting from CounterpartyForwardingInfo to PaymentRelay, the
cltv_expiry_delta is copied. Then, when forming a blinded payment path,
the value is mutated so that esoteric values don't reveal information
about the path. However, the value was only used in computing
PaymentConstraints and wasn't actually updated in PaymentRelay. Move the
logic for modifying the cltv_expiry_delta to the conversion code to
avoid this inconsistency.

diff --git a/lightning/src/blinded_path/payment.rs b/lightning/src/blinded_path/payment.rs
index f4df1e379d931b3ac65cbcdae65441c629554c6c..5d332a76faf57fed3b2fe844b91d5c5d04ed8a81 100644 (file)
--- a/lightning/src/blinded_path/payment.rs
+++ b/lightning/src/blinded_path/payment.rs
@@ -97,12 +97,24 @@ pub struct PaymentConstraints {
        pub htlc_minimum_msat: u64,
 }
 
-impl From<CounterpartyForwardingInfo> for PaymentRelay {
-       fn from(info: CounterpartyForwardingInfo) -> Self {
+impl TryFrom<CounterpartyForwardingInfo> for PaymentRelay {
+       type Error = ();
+
+       fn try_from(info: CounterpartyForwardingInfo) -> Result<Self, ()> {
                let CounterpartyForwardingInfo {
                        fee_base_msat, fee_proportional_millionths, cltv_expiry_delta
                } = info;
-               Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat }
+
+               // Avoid exposing esoteric CLTV expiry deltas
+               let cltv_expiry_delta = match cltv_expiry_delta {
+                       0..=40 => 40,
+                       41..=80 => 80,
+                       81..=144 => 144,
+                       145..=216 => 216,
+                       _ => return Err(()),
+               };
+
+               Ok(Self { cltv_expiry_delta, fee_proportional_millionths, fee_base_msat })
        }
 }
 

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 485fd239128df8ab39b0806723a7d3d6b6e24e3a..524bb1bc4c708baa983b65064a76d17ade17ae80 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -114,19 +114,14 @@ impl<G: Deref<Target = NetworkGraph<L>> + Clone, L: Deref, S: Deref, SP: Sized,
                                        None => return None,
                                };
                                let payment_relay: PaymentRelay = match details.counterparty.forwarding_info {
-                                       Some(forwarding_info) => forwarding_info.into(),
+                                       Some(forwarding_info) => match forwarding_info.try_into() {
+                                               Ok(payment_relay) => payment_relay,
+                                               Err(()) => return None,
+                                       },
                                        None => return None,
                                };
 
-                               // Avoid exposing esoteric CLTV expiry deltas
-                               let cltv_expiry_delta = match payment_relay.cltv_expiry_delta {
-                                       0..=40 => 40u32,
-                                       41..=80 => 80u32,
-                                       81..=144 => 144u32,
-                                       145..=216 => 216u32,
-                                       _ => return None,
-                               };
-
+                               let cltv_expiry_delta = payment_relay.cltv_expiry_delta as u32;
                                let payment_constraints = PaymentConstraints {
                                        max_cltv_expiry: tlvs.payment_constraints.max_cltv_expiry + cltv_expiry_delta,
                                        htlc_minimum_msat: details.inbound_htlc_minimum_msat.unwrap_or(0),