From cee577790b4c6c9533c46492282d520eef420f7e Mon Sep 17 00:00:00 2001
From: "fox.cpp" <fox.cpp@disroot.org>
Date: Thu, 8 Feb 2024 12:31:20 +0300
Subject: [PATCH] address: Special-case null return-path in normalization
 functions

See #629.
---
 framework/address/norm.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/framework/address/norm.go b/framework/address/norm.go
index 510fb63b..6998e662 100644
--- a/framework/address/norm.go
+++ b/framework/address/norm.go
@@ -36,6 +36,10 @@ import (
 //
 // On error, case-folded addr is also returned.
 func ForLookup(addr string) (string, error) {
+	if addr == "" { // Null return-path case.
+		return "", nil
+	}
+
 	mbox, domain, err := Split(addr)
 	if err != nil {
 		return strings.ToLower(addr), err
@@ -64,6 +68,10 @@ func ForLookup(addr string) (string, error) {
 //
 // Original value is also returned on the error.
 func CleanDomain(addr string) (string, error) {
+	if addr == "" { // Null return-path
+		return "", nil
+	}
+
 	mbox, domain, err := Split(addr)
 	if err != nil {
 		return addr, err