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fix(dns): return NODATA instead of NXDOMAIN when a name exists with a… #374

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fix(dns): return NODATA instead of NXDOMAIN when a name exists with a… #374

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d692267
fix(dns): return NODATA instead of NXDOMAIN when a name exists with a…
Feb 19, 2025
27a8770
test: dns rcodes for authoritative names with and without answer
Feb 26, 2025
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30 changes: 22 additions & 8 deletions dns.go
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Original file line number Diff line number Diff line change
Expand Up @@ -130,25 +130,28 @@ func (d *DNSServer) readQuery(m *dns.Msg) {
}
}

func (d *DNSServer) getRecord(q dns.Question) ([]dns.RR, error) {
func (d *DNSServer) getRecord(q dns.Question) ([]dns.RR, bool, error) {
var rr []dns.RR
var cnames []dns.RR
var hasOther bool = false
domain, ok := d.Domains[strings.ToLower(q.Name)]
if !ok {
return rr, fmt.Errorf("No records for domain %s", q.Name)
return rr, hasOther, fmt.Errorf("No records for domain %s", q.Name)
}
for _, ri := range domain.Records {
if ri.Header().Rrtype == q.Qtype {
rr = append(rr, ri)
}
if ri.Header().Rrtype == dns.TypeCNAME {
cnames = append(cnames, ri)
} else {
hasOther = true
if ri.Header().Rrtype == dns.TypeCNAME {
cnames = append(cnames, ri)
}
}
}
if len(rr) == 0 {
return cnames, nil
return cnames, hasOther, nil
}
return rr, nil
return rr, hasOther, nil
}

// answeringForDomain checks if we have any records for a domain
Expand Down Expand Up @@ -198,7 +201,8 @@ func (d *DNSServer) answer(q dns.Question) ([]dns.RR, int, bool, error) {
if !d.isOwnChallenge(q.Name) && !d.answeringForDomain(q.Name) {
rcode = dns.RcodeNameError
}
r, _ := d.getRecord(q)
r, hasOther, _ := d.getRecord(q)

if q.Qtype == dns.TypeTXT {
if d.isOwnChallenge(q.Name) {
txtRRs, err = d.answerOwnChallenge(q)
Expand All @@ -208,6 +212,16 @@ func (d *DNSServer) answer(q dns.Question) ([]dns.RR, int, bool, error) {
if err == nil {
r = append(r, txtRRs...)
}
} else {
// must not return NXDOMAIN if another type found for the name
// see https://datatracker.ietf.org/doc/html/rfc2308#section-5
if len(r) == 0 && !hasOther {
// TXT not returned before, must check in DB
txtRRs, err = d.answerTXT(q)
if err == nil && len(txtRRs) > 0 {
rcode = dns.RcodeSuccess
}
}
}
if len(r) > 0 {
// Make sure that we return NOERROR if there were dynamic records for the domain
Expand Down
42 changes: 39 additions & 3 deletions dns_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ func TestEDNS(t *testing.T) {
resolv := resolver{server: "127.0.0.1:15353"}
answer, _ := resolv.lookup("auth.example.org", dns.TypeOPT)
if answer.Rcode != dns.RcodeSuccess {
t.Errorf("Was expecing NOERROR rcode for OPT query, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
t.Errorf("Was expecting NOERROR rcode for OPT query, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
}
}

Expand Down Expand Up @@ -175,7 +175,7 @@ func TestAuthoritative(t *testing.T) {
resolv := resolver{server: "127.0.0.1:15353"}
answer, _ := resolv.lookup("nonexistent.auth.example.org", dns.TypeA)
if answer.Rcode != dns.RcodeNameError {
t.Errorf("Was expecing NXDOMAIN rcode, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
t.Errorf("Was expecting NXDOMAIN rcode, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
}
if len(answer.Ns) != 1 {
t.Errorf("Was expecting exactly one answer (SOA) for invalid subdomain, but got %d", len(answer.Ns))
Expand Down Expand Up @@ -256,6 +256,42 @@ func TestResolveTXT(t *testing.T) {
}
}

func TestResolveRcode(t *testing.T) {
resolv := resolver{server: "127.0.0.1:15353"}
validTXT := "______________valid_response_______________"

atxt, err := DB.Register(cidrslice{})
if err != nil {
t.Errorf("Could not initiate db record: [%v]", err)
return
}
atxt.Value = validTXT
err = DB.Update(atxt.ACMETxtPost)
if err != nil {
t.Errorf("Could not update db record: [%v]", err)
return
}

for i, test := range []struct {
subDomain string
qType uint16
expRcode int
expAnswers int
}{
{atxt.Subdomain, dns.TypeA, dns.RcodeSuccess, 0},
{atxt.Subdomain, dns.TypeNS, dns.RcodeSuccess, 0},
{atxt.Subdomain, dns.TypeTXT, dns.RcodeSuccess, 1},
{"nonexistent", dns.TypeA, dns.RcodeNameError, 0},
} {
answer, _ := resolv.lookup(test.subDomain+".auth.example.org", test.qType)
if answer.Rcode != test.expRcode {
t.Errorf("Test %d: was expecting [%s] rcode, but got [%s] instead.", i, dns.RcodeToString[test.expRcode], dns.RcodeToString[answer.Rcode])
}
if len(answer.Answer) != test.expAnswers {
t.Errorf("Test %d: was expecting %d answer, but got %d instead.", i, test.expAnswers, len(answer.Answer))
}
}
}
func TestCaseInsensitiveResolveA(t *testing.T) {
resolv := resolver{server: "127.0.0.1:15353"}
answer, err := resolv.lookup("aUtH.eXAmpLe.org", dns.TypeA)
Expand All @@ -272,7 +308,7 @@ func TestCaseInsensitiveResolveSOA(t *testing.T) {
resolv := resolver{server: "127.0.0.1:15353"}
answer, _ := resolv.lookup("doesnotexist.aUtH.eXAmpLe.org", dns.TypeSOA)
if answer.Rcode != dns.RcodeNameError {
t.Errorf("Was expecing NXDOMAIN rcode, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
t.Errorf("Was expecting NXDOMAIN rcode, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
}

if len(answer.Ns) == 0 {
Expand Down