Fixing SOA record to use alt domain when alt domain in use (#10431)

CHANGELOG.md

@@ -1,5 +1,9 @@
 ## UNRELEASED
 
+BUG FIXES:
+
+* Fixing SOA record to return proper domain when alt domain in use. [[GH-10431]](https://github.com/hashicorp/consul/pull/10431)
+
 ## 1.11.0-alpha (September 16, 2021)
 
 SECURITY:

agent/dns.go

@@ -373,7 +373,7 @@ func (d *DNSServer) handlePtr(resp dns.ResponseWriter, req *dns.Msg) {
 
 	// Only add the SOA if requested
 	if req.Question[0].Qtype == dns.TypeSOA {
-		d.addSOA(cfg, m)
+		d.addSOA(cfg, m, q.Name)
 	}
 
 	datacenter := d.agent.config.Datacenter
@@ -486,7 +486,7 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
 	switch req.Question[0].Qtype {
 	case dns.TypeSOA:
 		ns, glue := d.nameservers(cfg, maxRecursionLevelDefault)
-		m.Answer = append(m.Answer, d.soa(cfg))
+		m.Answer = append(m.Answer, d.soa(cfg, q.Name))
 		m.Ns = append(m.Ns, ns...)
 		m.Extra = append(m.Extra, glue...)
 		m.SetRcode(req, dns.RcodeSuccess)
@@ -504,7 +504,7 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
 		err = d.dispatch(resp.RemoteAddr(), req, m, maxRecursionLevelDefault)
 		rCode := rCodeFromError(err)
 		if rCode == dns.RcodeNameError || errors.Is(err, errNoData) {
-			d.addSOA(cfg, m)
+			d.addSOA(cfg, m, q.Name)
 		}
 		m.SetRcode(req, rCode)
 	}
@@ -518,18 +518,23 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
 	}
 }
 
-func (d *DNSServer) soa(cfg *dnsConfig) *dns.SOA {
+func (d *DNSServer) soa(cfg *dnsConfig, questionName string) *dns.SOA {
+	domain := d.domain
+	if d.altDomain != "" && strings.HasSuffix(questionName, "."+d.altDomain) {
+		domain = d.altDomain
+	}
+
 	return &dns.SOA{
 		Hdr: dns.RR_Header{
-			Name:   d.domain,
+			Name:   domain,
 			Rrtype: dns.TypeSOA,
 			Class:  dns.ClassINET,
 			// Has to be consistent with MinTTL to avoid invalidation
 			Ttl: cfg.SOAConfig.Minttl,
 		},
-		Ns:      "ns." + d.domain,
+		Ns:      "ns." + domain,
 		Serial:  uint32(time.Now().Unix()),
-		Mbox:    "hostmaster." + d.domain,
+		Mbox:    "hostmaster." + domain,
 		Refresh: cfg.SOAConfig.Refresh,
 		Retry:   cfg.SOAConfig.Retry,
 		Expire:  cfg.SOAConfig.Expire,
@@ -538,8 +543,8 @@ func (d *DNSServer) soa(cfg *dnsConfig) *dns.SOA {
 }
 
 // addSOA is used to add an SOA record to a message for the given domain
-func (d *DNSServer) addSOA(cfg *dnsConfig, msg *dns.Msg) {
-	msg.Ns = append(msg.Ns, d.soa(cfg))
+func (d *DNSServer) addSOA(cfg *dnsConfig, msg *dns.Msg, questionName string) {
+	msg.Ns = append(msg.Ns, d.soa(cfg, questionName))
 }
 
 // nameservers returns the names and ip addresses of up to three random servers
@@ -600,6 +605,12 @@ func (d *DNSServer) nameservers(cfg *dnsConfig, maxRecursionLevel int) (ns []dns
 	return
 }
 
+func (d *DNSServer) invalidQuery(req, resp *dns.Msg, cfg *dnsConfig, qName string) {
+	d.logger.Warn("QName invalid", "qname", qName)
+	d.addSOA(cfg, resp, qName)
+	resp.SetRcode(req, dns.RcodeNameError)
+}
+
 func (d *DNSServer) parseDatacenter(labels []string, datacenter *string) bool {
 	switch len(labels) {
 	case 1:

agent/dns_test.go

@@ -6528,14 +6528,17 @@ func TestDNS_AltDomains_SOA(t *testing.T) {
 	defer a.Shutdown()
 	testrpc.WaitForLeader(t, a.RPC, "dc1")
 
-	questions := []string{
-		"test-node.node.consul.",
-		"test-node.node.test-domain.",
+	questions := []struct {
+		ask         string
+		want_domain string
+	}{
+		{"test-node.node.consul.", "consul."},
+		{"test-node.node.test-domain.", "test-domain."},
 	}
 
 	for _, question := range questions {
 		m := new(dns.Msg)
-		m.SetQuestion(question, dns.TypeSOA)
+		m.SetQuestion(question.ask, dns.TypeSOA)
 
 		c := new(dns.Client)
 		in, _, err := c.Exchange(m, a.DNSAddr())
@@ -6552,10 +6555,10 @@ func TestDNS_AltDomains_SOA(t *testing.T) {
 			t.Fatalf("Bad: %#v", in.Answer[0])
 		}
 
-		if got, want := soaRec.Hdr.Name, "consul."; got != want {
+		if got, want := soaRec.Hdr.Name, question.want_domain; got != want {
 			t.Fatalf("SOA name invalid, got %q want %q", got, want)
 		}
-		if got, want := soaRec.Ns, "ns.consul."; got != want {
+		if got, want := soaRec.Ns, ("ns." + question.want_domain); got != want {
 			t.Fatalf("SOA ns invalid, got %q want %q", got, want)
 		}
 	}