From: Arik Sosman <git@arik.io>
Date: Wed, 21 Jun 2023 23:12:45 +0000 (-0700)
Subject: Method for `ChannelTypeFeatures` serialization compatibility.
X-Git-Tag: v0.0.116-alpha1~4^2~3
X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=970b174e9003594a455da6b492390cd739ab4434;p=rust-lightning

Method for `ChannelTypeFeatures` serialization compatibility.
---

diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs
index 6ca5c929f..adae41381 100644
--- a/lightning/src/ln/chan_utils.rs
+++ b/lightning/src/ln/chan_utils.rs
@@ -40,6 +40,7 @@ use crate::util::transaction_utils::sort_outputs;
 use crate::ln::channel::{INITIAL_COMMITMENT_NUMBER, ANCHOR_OUTPUT_VALUE_SATOSHI};
 use core::ops::Deref;
 use crate::chain;
+use crate::ln::features::ChannelTypeFeatures;
 use crate::util::crypto::{sign, sign_with_aux_rand};
 
 /// Maximum number of one-way in-flight HTLC (protocol-level value).
@@ -769,6 +770,37 @@ pub fn build_htlc_input_witness(
 	witness
 }
 
+/// Pre-anchors channel type features did not use to get serialized in the following six structs:
+/// — [`ChannelTransactionParameters`]
+/// — [`CommitmentTransaction`]
+/// — [`CounterpartyOfferedHTLCOutput`]
+/// — [`CounterpartyReceivedHTLCOutput`]
+/// — [`HolderHTLCOutput`]
+/// — [`HolderFundingOutput`]
+///
+/// To ensure a forwards-compatible serialization, we use odd TLV fields. However, if new features
+/// are used that could break security, where old signers should be prevented from handling the
+/// serialized data, an optional even-field TLV will be used as a stand-in to break compatibility.
+///
+/// This method determines whether or not that option needs to be set based on the chanenl type
+/// features, and returns it.
+///
+/// [`CounterpartyOfferedHTLCOutput`]: crate::chain::package::CounterpartyOfferedHTLCOutput
+/// [`CounterpartyReceivedHTLCOutput`]: crate::chain::package::CounterpartyReceivedHTLCOutput
+/// [`HolderHTLCOutput`]: crate::chain::package::HolderHTLCOutput
+/// [`HolderFundingOutput`]: crate::chain::package::HolderFundingOutput
+pub(crate) fn legacy_deserialization_prevention_marker_for_channel_type_features(features: &ChannelTypeFeatures) -> Option<()> {
+	let mut legacy_version_bit_set = ChannelTypeFeatures::only_static_remote_key();
+	legacy_version_bit_set.set_scid_privacy_required();
+	legacy_version_bit_set.set_zero_conf_required();
+
+	if features.is_subset(&legacy_version_bit_set) {
+		None
+	} else {
+		Some(())
+	}
+}
+
 /// Gets the witnessScript for the to_remote output when anchors are enabled.
 #[inline]
 pub fn get_to_countersignatory_with_anchors_redeemscript(payment_point: &PublicKey) -> Script {