Add redundant blinded HTLC failure check for posterity.

Although this new check is unreachable right now, it helps prevent potential
future errors where we incorrectly fail blinded HTLCs with an unblinded error.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index e8b8f43dae92d2b8a559fca1bbd9e698f72e1b4d..5bee15c97247308fb5aa47f0da4e2e724338b400 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -3025,11 +3025,12 @@ where
                        msg, &self.node_signer, &self.logger, &self.secp_ctx
                )?;
 
-               let is_blinded = match next_hop {
+               let is_intro_node_forward = match next_hop {
                        onion_utils::Hop::Forward {
+                               // TODO: update this when we support blinded forwarding as non-intro node
                                next_hop_data: msgs::InboundOnionPayload::BlindedForward { .. }, ..
                        } => true,
-                       _ => false, // TODO: update this when we support receiving to multi-hop blinded paths
+                       _ => false,
                };
 
                macro_rules! return_err {
@@ -3039,7 +3040,17 @@ where
                                                WithContext::from(&self.logger, Some(*counterparty_node_id), Some(msg.channel_id)),
                                                "Failed to accept/forward incoming HTLC: {}", $msg
                                        );
-                                       let (err_code, err_data) = if is_blinded {
+                                       // If `msg.blinding_point` is set, we must always fail with malformed.
+                                       if msg.blinding_point.is_some() {
+                                               return Err(HTLCFailureMsg::Malformed(msgs::UpdateFailMalformedHTLC {
+                                                       channel_id: msg.channel_id,
+                                                       htlc_id: msg.htlc_id,
+                                                       sha256_of_onion: [0; 32],
+                                                       failure_code: INVALID_ONION_BLINDING,
+                                               }));
+                                       }
+
+                                       let (err_code, err_data) = if is_intro_node_forward {
                                                (INVALID_ONION_BLINDING, &[0; 32][..])
                                        } else { ($err_code, $data) };
                                        return Err(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {