Use explicit WithoutLength for BOLT 12 features

Most BOLT 12 features are used as the value of a TLV record and thus
don't use an explicit length. One exception is the features inside the
blinded payinfo subtype since the TLV record contains a list of them.
However, these features are also used in the BOLT 4 encrypted_data_tlv
TLV stream as a single record, where the length is implicit.

Implement Readable and Writeable for Features wrapped in WithoutLength
such that either serialization can be used where required.

diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 1f455471a9f4fa2bf3b30b9a1ade5ac54638bb72..9d34433161a55e064afcddca798fa6fe7aaacdeb 100644 (file)
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -65,7 +65,7 @@ use core::marker::PhantomData;
 use bitcoin::bech32;
 use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5, WriteBase32};
 use crate::ln::msgs::DecodeError;
-use crate::util::ser::{Readable, Writeable, Writer};
+use crate::util::ser::{Readable, WithoutLength, Writeable, Writer};
 
 mod sealed {
        use crate::prelude::*;
@@ -725,26 +725,40 @@ macro_rules! impl_feature_tlv_write {
        ($features: ident) => {
                impl Writeable for $features {
                        fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
-                               self.write_be(w)
+                               WithoutLength(self).write(w)
                        }
                }
                impl Readable for $features {
                        fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
-                               let v = io_extras::read_to_end(r)?;
-                               Ok(Self::from_be_bytes(v))
+                               Ok(WithoutLength::<Self>::read(r)?.0)
                        }
                }
        }
 }
 
 impl_feature_tlv_write!(ChannelTypeFeatures);
-impl_feature_tlv_write!(OfferFeatures);
-impl_feature_tlv_write!(InvoiceRequestFeatures);
+
+// Some features may appear both in a TLV record and as part of a TLV subtype sequence. The latter
+// requires a length but the former does not.
+
+impl<T: sealed::Context> Writeable for WithoutLength<&Features<T>> {
+       fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
+               self.0.write_be(w)
+       }
+}
+
+impl<T: sealed::Context> Readable for WithoutLength<Features<T>> {
+       fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
+               let v = io_extras::read_to_end(r)?;
+               Ok(WithoutLength(Features::<T>::from_be_bytes(v)))
+       }
+}
 
 #[cfg(test)]
 mod tests {
-       use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, sealed};
+       use super::{ChannelFeatures, ChannelTypeFeatures, InitFeatures, InvoiceFeatures, NodeFeatures, OfferFeatures, sealed};
        use bitcoin::bech32::{Base32Len, FromBase32, ToBase32, u5};
+       use crate::util::ser::{Readable, WithoutLength, Writeable};
 
        #[test]
        fn sanity_test_unknown_bits() {
@@ -838,6 +852,20 @@ mod tests {
                assert!(features.supports_payment_secret());
        }
 
+       #[test]
+       fn encodes_features_without_length() {
+               let features = OfferFeatures::from_le_bytes(vec![1, 2, 3, 4, 5, 42, 100, 101]);
+               assert_eq!(features.flags.len(), 8);
+
+               let mut serialized_features = Vec::new();
+               WithoutLength(&features).write(&mut serialized_features).unwrap();
+               assert_eq!(serialized_features.len(), 8);
+
+               let deserialized_features =
+                       WithoutLength::<OfferFeatures>::read(&mut &serialized_features[..]).unwrap().0;
+               assert_eq!(features, deserialized_features);
+       }
+
        #[test]
        fn invoice_features_encoding() {
                let features_as_u5s = vec![

diff --git a/lightning/src/offers/invoice_request.rs b/lightning/src/offers/invoice_request.rs
index 690bc8d0bdb72d03fc0914b628ed1842a0ef9701..fd5ecda558af523f1664452f98968edef311da9c 100644 (file)
--- a/lightning/src/offers/invoice_request.rs
+++ b/lightning/src/offers/invoice_request.rs
@@ -371,7 +371,7 @@ impl Writeable for InvoiceRequestContents {
 tlv_stream!(InvoiceRequestTlvStream, InvoiceRequestTlvStreamRef, 80..160, {
        (80, chain: ChainHash),
        (82, amount: (u64, HighZeroBytesDroppedBigSize)),
-       (84, features: InvoiceRequestFeatures),
+       (84, features: (InvoiceRequestFeatures, WithoutLength)),
        (86, quantity: (u64, HighZeroBytesDroppedBigSize)),
        (88, payer_id: PublicKey),
        (89, payer_note: (String, WithoutLength)),

diff --git a/lightning/src/offers/offer.rs b/lightning/src/offers/offer.rs
index 6451d9431a188f3b15440c1d687435e7068f7240..e655004460024acd7afe2971bc9556392c405a0b 100644 (file)
--- a/lightning/src/offers/offer.rs
+++ b/lightning/src/offers/offer.rs
@@ -567,7 +567,7 @@ tlv_stream!(OfferTlvStream, OfferTlvStreamRef, 1..80, {
        (6, currency: CurrencyCode),
        (8, amount: (u64, HighZeroBytesDroppedBigSize)),
        (10, description: (String, WithoutLength)),
-       (12, features: OfferFeatures),
+       (12, features: (OfferFeatures, WithoutLength)),
        (14, absolute_expiry: (u64, HighZeroBytesDroppedBigSize)),
        (16, paths: (Vec<BlindedPath>, WithoutLength)),
        (18, issuer: (String, WithoutLength)),