Merge pull request #7392 from adiabat/hltcinterceptfix

HTLC Interceptor: Fix nil pointer dereference

docs/release-notes/release-notes-0.16.0.md

@@ -125,6 +125,9 @@ current gossip sync query status.
   update in order to use the new versioned RPC and upgrade any on-chain outputs
   to the new version.
 
+* [A bug has been fixed which could cause `lnd` to crash when parsing a
+  malformed HTLC intercept message](https://github.com/lightningnetwork/lnd/pull/7392).
+
 ## Wallet
 
 * [Allows Taproot public keys and tap scripts to be imported as watch-only

lnrpc/routerrpc/forward_interceptor.go

@@ -100,6 +100,11 @@ func (r *forwardInterceptor) onIntercept(
 func (r *forwardInterceptor) resolveFromClient(
 	in *ForwardHtlcInterceptResponse) error {
 
+	if in.IncomingCircuitKey == nil {
+		return status.Errorf(codes.InvalidArgument,
+			"CircuitKey missing from ForwardHtlcInterceptResponse")
+	}
+
 	log.Tracef("Resolving intercepted packet %v", in)
 
 	circuitKey := models.CircuitKey{