From 0fe5d738538f07eeaab0f450b162eb29d765b8e1 Mon Sep 17 00:00:00 2001
From: Niklas <niklas@kapelle.org>
Date: Tue, 2 Feb 2021 01:15:57 +0100
Subject: [PATCH] handle wildcard CNAME

---
 internal/authoritative.go | 22 +++++++++++++++++++++-
 internal/cooldns.go       |  2 --
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/internal/authoritative.go b/internal/authoritative.go
index 1e0a313..cb6fcc8 100644
--- a/internal/authoritative.go
+++ b/internal/authoritative.go
@@ -6,6 +6,8 @@ import (
 	"github.com/miekg/dns"
 )
 
+type rrMap map[uint16]map[string][]dns.RR
+
 // All record types to send when a ANY request is send
 var anyRecordTypes = []uint16{
 	dns.TypeSOA,
@@ -43,8 +45,9 @@ func handleRequest(w dns.ResponseWriter, r *dns.Msg, zone zoneView) {
 		// Handle any other type
 		m.Answer = append(m.Answer, rrs[q.Name]...)
 
-		// Check for wildcard
+		// if no rr found yet
 		if len(m.Answer) == 0 {
+			// Check for wildcard
 			parts := dns.SplitDomainName(q.Name)[1:]
 			searchDomain := "*." + dns.Fqdn(strings.Join(parts, "."))
 			foundDomain := rrs[searchDomain]
@@ -80,6 +83,23 @@ func handleRequest(w dns.ResponseWriter, r *dns.Msg, zone zoneView) {
 						m.Answer = append(m.Answer, zone.rr[q.Qtype][t.Target]...)
 					}
 				}
+			} else {
+				// No direct A/AAAA or CNAME found. Check for CNAME wildcard
+				parts := dns.SplitDomainName(q.Name)[1:]
+				searchDomain := "*." + dns.Fqdn(strings.Join(parts, "."))
+				foundDomain := zone.rr[dns.TypeCNAME][searchDomain]
+				for _, rr := range foundDomain {
+					// Add CNAME to answer section
+					newRR := rr
+					newRR.Header().Name = q.Name
+					m.Answer = append(m.Answer, newRR)
+
+					// Add resolved CNAME to *also* to the answer section (bind does the same soo)
+					if t, ok := rr.(*dns.CNAME); ok {
+						m.Answer = append(m.Answer, zone.rr[dns.TypeA][t.Target]...)
+						m.Answer = append(m.Answer, zone.rr[dns.TypeAAAA][t.Target]...)
+					}
+				}
 			}
 		}
 	case dns.TypeNS:
diff --git a/internal/cooldns.go b/internal/cooldns.go
index 46ec9f3..cebf855 100644
--- a/internal/cooldns.go
+++ b/internal/cooldns.go
@@ -16,8 +16,6 @@ type zoneView struct {
 
 type zoneMap map[string][]zoneView
 
-type rrMap map[uint16]map[string][]dns.RR
-
 // Start starts cooldns
 func Start(configPath string) {
 	config, err := loadConfig(configPath)