From 385a22085d5ddb119dad293c617716ab64fd7bad Mon Sep 17 00:00:00 2001
From: Kees Monshouwer <mind04@monshouwer.org>
Date: Thu, 13 Apr 2023 09:32:16 +0200
Subject: [PATCH] make getCommonLabels() root aware

---
 pdns/dnsname.cc         |  6 +++++-
 pdns/dnssecsigner.cc    |  3 ---
 pdns/test-dnsname_cc.cc | 12 ++++++++----
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/pdns/dnsname.cc b/pdns/dnsname.cc
index 3bfbf3007f..25a90078a8 100644
--- a/pdns/dnsname.cc
+++ b/pdns/dnsname.cc
@@ -296,7 +296,11 @@ void DNSName::makeUsRelative(const DNSName& zone)
 
 DNSName DNSName::getCommonLabels(const DNSName& other) const
 {
-  DNSName result;
+  if (empty() || other.empty()) {
+    return DNSName();
+  }
+
+  DNSName result(g_rootdnsname);
 
   const std::vector<std::string> ours = getRawLabels();
   const std::vector<std::string> others = other.getRawLabels();
diff --git a/pdns/dnssecsigner.cc b/pdns/dnssecsigner.cc
index 7fd7d53253..74dc882ab0 100644
--- a/pdns/dnssecsigner.cc
+++ b/pdns/dnssecsigner.cc
@@ -226,9 +226,6 @@ void addRRSigs(DNSSECKeeper& dk, UeberBackend& db, const set<DNSName>& authSet,
     signQName = pos->dr.d_name.makeLowerCase();
     if (pos->dr.d_type == QType::NSEC) {
       authQName = signQName.getCommonLabels(getRR<NSECRecordContent>(pos->dr)->d_next);
-      if (authQName.empty()) {
-        authQName = g_rootdnsname;
-      }
     }
     else {
       authQName = signQName;
diff --git a/pdns/test-dnsname_cc.cc b/pdns/test-dnsname_cc.cc
index 0001d1ee04..43c1b900dd 100644
--- a/pdns/test-dnsname_cc.cc
+++ b/pdns/test-dnsname_cc.cc
@@ -1019,14 +1019,18 @@ BOOST_AUTO_TEST_CASE(test_getcommonlabels) {
   BOOST_CHECK_EQUAL(name2.getCommonLabels(name1), DNSName("powerdns.com"));
 
   const DNSName name3("www.powerdns.org");
-  BOOST_CHECK_EQUAL(name1.getCommonLabels(name3), DNSName());
-  BOOST_CHECK_EQUAL(name2.getCommonLabels(name3), DNSName());
-  BOOST_CHECK_EQUAL(name3.getCommonLabels(name1), DNSName());
-  BOOST_CHECK_EQUAL(name3.getCommonLabels(name2), DNSName());
+  BOOST_CHECK_EQUAL(name1.getCommonLabels(name3), g_rootdnsname);
+  BOOST_CHECK_EQUAL(name2.getCommonLabels(name3), g_rootdnsname);
+  BOOST_CHECK_EQUAL(name3.getCommonLabels(name1), g_rootdnsname);
+  BOOST_CHECK_EQUAL(name3.getCommonLabels(name2), g_rootdnsname);
 
   const DNSName name4("WWw.PowErDnS.org");
   BOOST_CHECK_EQUAL(name3.getCommonLabels(name4), name3);
   BOOST_CHECK_EQUAL(name4.getCommonLabels(name3), name4);
+
+  const DNSName(name5);
+  BOOST_CHECK_EQUAL(name1.getCommonLabels(name5), DNSName());
+  BOOST_CHECK_EQUAL(name5.getCommonLabels(name1), DNSName());
 }
 
 BOOST_AUTO_TEST_SUITE_END()
-- 
2.47.2