From ed5f9f6a9b9f9fc84810cdc1c04ff0a1caa888ff Mon Sep 17 00:00:00 2001
From: Arik Sosman <git@arik.io>
Date: Tue, 20 Jun 2023 13:17:28 -0700
Subject: [PATCH] Verify channel type features for decoding.

---
 lightning/src/chain/package.rs | 32 ++++++++++++++++++++++++++++++++
 lightning/src/ln/chan_utils.rs |  8 ++++++++
 lightning/src/ln/features.rs   |  1 -
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/lightning/src/chain/package.rs b/lightning/src/chain/package.rs
index 0b7dbd462..891d7d1da 100644
--- a/lightning/src/chain/package.rs
+++ b/lightning/src/chain/package.rs
@@ -75,6 +75,30 @@ pub(crate) fn weight_received_htlc(channel_type_features: &ChannelTypeFeatures)
 	if channel_type_features.supports_anchors_zero_fee_htlc_tx() { WEIGHT_RECEIVED_HTLC_ANCHORS } else { WEIGHT_RECEIVED_HTLC }
 }
 
+/// Verifies deserializable channel type features
+pub(crate) fn verify_channel_type_features(channel_type_features: &Option<ChannelTypeFeatures>, additional_permitted_features: Option<&ChannelTypeFeatures>) -> Result<(), DecodeError> {
+	if let Some(features) = channel_type_features.as_ref() {
+		if features.requires_unknown_bits() {
+			return Err(DecodeError::UnknownRequiredFeature);
+		}
+
+		let mut supported_feature_set = ChannelTypeFeatures::anchors_zero_htlc_fee_and_dependencies();
+		supported_feature_set.set_scid_privacy_required();
+		supported_feature_set.set_zero_conf_required();
+
+		// allow the passing of an additional necessary permitted flag
+		if let Some(additional_permitted_features) = additional_permitted_features {
+			supported_feature_set |= additional_permitted_features;
+		}
+
+		if !features.is_subset(&supported_feature_set) {
+			return Err(DecodeError::UnknownRequiredFeature);
+		}
+	}
+
+	Ok(())
+}
+
 // number_of_witness_elements + sig_length + revocation_sig + true_length + op_true + witness_script_length + witness_script
 pub(crate) const WEIGHT_REVOKED_OUTPUT: u64 = 1 + 1 + 73 + 1 + 1 + 1 + 77;
 
@@ -239,6 +263,8 @@ impl Readable for CounterpartyOfferedHTLCOutput {
 			(11, channel_type_features, option),
 		});
 
+		verify_channel_type_features(&channel_type_features, None)?;
+
 		Ok(Self {
 			per_commitment_point: per_commitment_point.0.unwrap(),
 			counterparty_delayed_payment_base_key: counterparty_delayed_payment_base_key.0.unwrap(),
@@ -310,6 +336,8 @@ impl Readable for CounterpartyReceivedHTLCOutput {
 			(9, channel_type_features, option),
 		});
 
+		verify_channel_type_features(&channel_type_features, None)?;
+
 		Ok(Self {
 			per_commitment_point: per_commitment_point.0.unwrap(),
 			counterparty_delayed_payment_base_key: counterparty_delayed_payment_base_key.0.unwrap(),
@@ -385,6 +413,8 @@ impl Readable for HolderHTLCOutput {
 			(7, channel_type_features, option),
 		});
 
+		verify_channel_type_features(&channel_type_features, None)?;
+
 		Ok(Self {
 			amount_msat: amount_msat.0.unwrap(),
 			cltv_expiry: cltv_expiry.0.unwrap(),
@@ -444,6 +474,8 @@ impl Readable for HolderFundingOutput {
 			(3, funding_amount, option)
 		});
 
+		verify_channel_type_features(&channel_type_features, None)?;
+
 		Ok(Self {
 			funding_redeemscript: funding_redeemscript.0.unwrap(),
 			channel_type_features: channel_type_features.unwrap_or(ChannelTypeFeatures::only_static_remote_key()),
diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs
index d570347fe..7fa2308d0 100644
--- a/lightning/src/ln/chan_utils.rs
+++ b/lightning/src/ln/chan_utils.rs
@@ -952,6 +952,10 @@ impl Readable for ChannelTransactionParameters {
 			(11, channel_type_features, option),
 		});
 
+		let mut additional_features = ChannelTypeFeatures::empty();
+		additional_features.set_anchors_nonzero_fee_htlc_tx_required();
+		chain::package::verify_channel_type_features(&channel_type_features, Some(&additional_features))?;
+
 		Ok(Self {
 			holder_pubkeys: holder_pubkeys.0.unwrap(),
 			holder_selected_contest_delay: holder_selected_contest_delay.0.unwrap(),
@@ -1375,6 +1379,10 @@ impl Readable for CommitmentTransaction {
 			(15, channel_type_features, option),
 		});
 
+		let mut additional_features = ChannelTypeFeatures::empty();
+		additional_features.set_anchors_nonzero_fee_htlc_tx_required();
+		chain::package::verify_channel_type_features(&channel_type_features, Some(&additional_features))?;
+
 		Ok(Self {
 			commitment_number: commitment_number.0.unwrap(),
 			to_broadcaster_value_sat: to_broadcaster_value_sat.0.unwrap(),
diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 714bfaa55..ca6ea70b6 100644
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -595,7 +595,6 @@ impl ChannelTypeFeatures {
 		ret
 	}
 
-	#[cfg(any(anchors, test))]
 	/// Constructs a ChannelTypeFeatures with anchors support
 	pub(crate) fn anchors_zero_htlc_fee_and_dependencies() -> Self {
 		let mut ret = Self::empty();
-- 
2.39.5