Document and test 0-len channel update onion error case

[rust-lightning] / lightning / src / ln / onion_utils.rs

diff --git a/lightning/src/ln/onion_utils.rs b/lightning/src/ln/onion_utils.rs
index 03ba8877176b37ee30588f427680631b99f0b49a..64a1e3fa3487da78dc4918d17f56b57f8c99b085 100644 (file)
--- a/lightning/src/ln/onion_utils.rs
+++ b/lightning/src/ln/onion_utils.rs
@@ -91,15 +91,18 @@ pub(super) fn gen_pad_from_shared_secret(shared_secret: &[u8]) -> [u8; 32] {
        Hmac::from_engine(hmac).into_inner()
 }
 
-pub(crate) fn next_hop_packet_pubkey<T: secp256k1::Signing + secp256k1::Verification>(secp_ctx: &Secp256k1<T>, packet_pubkey: PublicKey, packet_shared_secret: &[u8; 32]) -> Result<PublicKey, secp256k1::Error> {
+/// Calculates a pubkey for the next hop, such as the next hop's packet pubkey or blinding point.
+pub(crate) fn next_hop_pubkey<T: secp256k1::Signing + secp256k1::Verification>(
+       secp_ctx: &Secp256k1<T>, curr_pubkey: PublicKey, shared_secret: &[u8]
+) -> Result<PublicKey, secp256k1::Error> {
        let blinding_factor = {
                let mut sha = Sha256::engine();
-               sha.input(&packet_pubkey.serialize()[..]);
-               sha.input(packet_shared_secret);
+               sha.input(&curr_pubkey.serialize()[..]);
+               sha.input(shared_secret);
                Sha256::from_engine(sha).into_inner()
        };
 
-       packet_pubkey.mul_tweak(secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap())
+       curr_pubkey.mul_tweak(secp_ctx, &Scalar::from_be_bytes(blinding_factor).unwrap())
 }
 
 // can only fail if an intermediary hop has an invalid public key or session_priv is invalid
@@ -576,6 +579,8 @@ where L::Target: Logger {
                                                                        msg: chan_update,
                                                                })
                                                        } else {
+                                                               // The node in question intentionally encoded a 0-length channel update. This is
+                                                               // likely due to https://github.com/ElementsProject/lightning/issues/6200.
                                                                network_update = Some(NetworkUpdate::ChannelFailure {
                                                                        short_channel_id: route_hop.short_channel_id,
                                                                        is_permanent: false,