// LookupCAA uses a DNSSEC-enabled query to find all CAA records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupCAA(domain string, alias bool) ([]*dns.CAA, error) {
if alias {
// Check if there is a CNAME record for domain
canonName, err := dnsResolver.LookupCNAME(domain)
if err != nil {
return nil, err
}
if canonName == "" || canonName == domain {
return []*dns.CAA{}, nil
}
domain = canonName
}
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(domain), dns.TypeCAA)
r, _, err := dnsResolver.LookupDNSSEC(m)
if err != nil {
return nil, err
}
var CAAs []*dns.CAA
for _, answer := range r.Answer {
if answer.Header().Rrtype == dns.TypeCAA {
caaR, ok := answer.(*dns.CAA)
if !ok {
err = errors.New("Badly formatted record")
return nil, err
}
CAAs = append(CAAs, caaR)
}
}
return CAAs, nil
}
// LookupDNSSEC sends the provided DNS message to a randomly chosen server (see
// ExchangeOne) with DNSSEC enabled. If the lookup fails, this method sends a
// clarification query to determine if it's because DNSSEC was invalid or just
// a run-of-the-mill error. If it's because of DNSSEC, it returns ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupDNSSEC(m *dns.Msg) (*dns.Msg, time.Duration, error) {
// Set DNSSEC OK bit
m.SetEdns0(4096, true)
r, rtt, err := dnsResolver.ExchangeOne(m)
if err != nil {
return r, rtt, err
}
if r.Rcode != dns.RcodeSuccess && r.Rcode != dns.RcodeNameError && r.Rcode != dns.RcodeNXRrset {
if r.Rcode == dns.RcodeServerFailure {
// Re-send query with +cd to see if SERVFAIL was caused by DNSSEC
// validation failure at the resolver
m.CheckingDisabled = true
checkR, _, err := dnsResolver.ExchangeOne(m)
if err != nil {
return r, rtt, err
}
if checkR.Rcode != dns.RcodeServerFailure {
// DNSSEC error, so we return the testable object.
err = DNSSECError{}
return r, rtt, err
}
}
err = fmt.Errorf("Invalid response code: %d-%s", r.Rcode, dns.RcodeToString[r.Rcode])
return r, rtt, err
}
return r, rtt, err
}
// LookupHost uses a DNSSEC-enabled query to find all A/AAAA records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupHost(hostname string) ([]net.IP, time.Duration, error) {
var addrs []net.IP
var answers []dns.RR
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(hostname), dns.TypeA)
r, aRtt, err := dnsResolver.LookupDNSSEC(m)
if err != nil {
return addrs, aRtt, err
}
answers = append(answers, r.Answer...)
m.SetQuestion(dns.Fqdn(hostname), dns.TypeAAAA)
r, aaaaRtt, err := dnsResolver.LookupDNSSEC(m)
if err != nil {
return addrs, aRtt + aaaaRtt, err
}
answers = append(answers, r.Answer...)
for _, answer := range answers {
if answer.Header().Rrtype == dns.TypeA {
a := answer.(*dns.A)
addrs = append(addrs, a.A)
} else if answer.Header().Rrtype == dns.TypeAAAA {
aaaa := answer.(*dns.AAAA)
addrs = append(addrs, aaaa.AAAA)
}
}
return addrs, aRtt + aaaaRtt, nil
}
// exchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) exchangeOne(hostname string, qtype uint16, msgStats metrics.Scope) (rsp *dns.Msg, err error) {
m := new(dns.Msg)
// Set question type
m.SetQuestion(dns.Fqdn(hostname), qtype)
// Set DNSSEC OK bit for resolver
m.SetEdns0(4096, true)
if len(dnsResolver.Servers) < 1 {
err = fmt.Errorf("Not configured with at least one DNS Server")
return
}
dnsResolver.stats.Inc("Rate", 1)
// Randomly pick a server
chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]
msg, rtt, err := dnsResolver.DNSClient.Exchange(m, chosenServer)
msgStats.TimingDuration("RTT", rtt)
if err == nil {
msgStats.Inc("Successes", 1)
} else {
msgStats.Inc("Errors", 1)
}
return msg, err
}
func TestDNSDuplicateServers(t *testing.T) {
obj := NewDNSResolver(time.Second*10, []string{"8.8.8.8:53", "8.8.8.8:53"})
m := new(dns.Msg)
m.SetQuestion("letsencrypt.org.", dns.TypeSOA)
_, _, err := obj.ExchangeOne(m)
test.AssertNotError(t, err, "No message")
}
// exchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) exchangeOne(ctx context.Context, hostname string, qtype uint16, msgStats metrics.Scope) (*dns.Msg, error) {
m := new(dns.Msg)
// Set question type
m.SetQuestion(dns.Fqdn(hostname), qtype)
// Set DNSSEC OK bit for resolver
m.SetEdns0(4096, true)
if len(dnsResolver.Servers) < 1 {
return nil, fmt.Errorf("Not configured with at least one DNS Server")
}
dnsResolver.stats.Inc("Rate", 1)
// Randomly pick a server
chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]
client := dnsResolver.DNSClient
tries := 1
start := dnsResolver.clk.Now()
msgStats.Inc("Calls", 1)
defer msgStats.TimingDuration("Latency", dnsResolver.clk.Now().Sub(start))
for {
msgStats.Inc("Tries", 1)
ch := make(chan dnsResp, 1)
go func() {
rsp, rtt, err := client.Exchange(m, chosenServer)
msgStats.TimingDuration("SingleTryLatency", rtt)
ch <- dnsResp{m: rsp, err: err}
}()
select {
case <-ctx.Done():
msgStats.Inc("Cancels", 1)
msgStats.Inc("Errors", 1)
return nil, ctx.Err()
case r := <-ch:
if r.err != nil {
msgStats.Inc("Errors", 1)
operr, ok := r.err.(*net.OpError)
isRetryable := ok && operr.Temporary()
hasRetriesLeft := tries < dnsResolver.maxTries
if isRetryable && hasRetriesLeft {
tries++
continue
} else if isRetryable && !hasRetriesLeft {
msgStats.Inc("RanOutOfTries", 1)
}
} else {
msgStats.Inc("Successes", 1)
}
return r.m, r.err
}
}
}
// ExchangeOne performs a single DNS exchange with a randomly chosen server
// out of the server list, returning the response, time, and error (if any).
// This method sets the DNSSEC OK bit on the message to true before sending
// it to the resolver in case validation isn't the resolvers default behaviour.
func (dnsResolver *DNSResolverImpl) ExchangeOne(hostname string, qtype uint16) (rsp *dns.Msg, rtt time.Duration, err error) {
m := new(dns.Msg)
// Set question type
m.SetQuestion(dns.Fqdn(hostname), qtype)
// Set DNSSEC OK bit for resolver
m.SetEdns0(4096, true)
if len(dnsResolver.Servers) < 1 {
err = fmt.Errorf("Not configured with at least one DNS Server")
return
}
// Randomly pick a server
chosenServer := dnsResolver.Servers[rand.Intn(len(dnsResolver.Servers))]
return dnsResolver.DNSClient.Exchange(m, chosenServer)
}
// LookupCNAME uses a DNSSEC-enabled query to records for domain and returns either
// the target, "", or a if the query fails due to DNSSEC, error will be set to
// ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupCNAME(domain string) (string, error) {
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(domain), dns.TypeCNAME)
r, _, err := dnsResolver.LookupDNSSEC(m)
if err != nil {
return "", err
}
for _, answer := range r.Answer {
if cname, ok := answer.(*dns.CNAME); ok {
return cname.Target, nil
}
}
return "", nil
}
func mockDNSQuery(w dns.ResponseWriter, r *dns.Msg) {
defer w.Close()
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
for _, q := range r.Question {
if q.Name == "servfail.com." {
m.Rcode = dns.RcodeServerFailure
w.WriteMsg(m)
return
}
switch q.Qtype {
case dns.TypeSOA:
record := new(dns.SOA)
record.Hdr = dns.RR_Header{Name: "letsencrypt.org.", Rrtype: dns.TypeSOA, Class: dns.ClassINET, Ttl: 0}
record.Ns = "ns.letsencrypt.org."
record.Mbox = "master.letsencrypt.org."
record.Serial = 1
record.Refresh = 1
record.Retry = 1
record.Expire = 1
record.Minttl = 1
m.Answer = append(m.Answer, record)
w.WriteMsg(m)
return
case dns.TypeA:
if q.Name == "cps.letsencrypt.org." {
record := new(dns.A)
record.Hdr = dns.RR_Header{Name: "cps.letsencrypt.org.", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
record.A = net.ParseIP("127.0.0.1")
m.Answer = append(m.Answer, record)
w.WriteMsg(m)
return
}
case dns.TypeCAA:
if q.Name == "bracewel.net." {
record := new(dns.CAA)
record.Hdr = dns.RR_Header{Name: "bracewel.net.", Rrtype: dns.TypeCAA, Class: dns.ClassINET, Ttl: 0}
record.Tag = "issue"
record.Value = "letsencrypt.org"
record.Flag = 1
m.Answer = append(m.Answer, record)
w.WriteMsg(m)
return
}
}
}
w.WriteMsg(m)
return
}
// LookupTXT uses a DNSSEC-enabled query to find all TXT records associated with
// the provided hostname. If the query fails due to DNSSEC, error will be
// set to ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupTXT(hostname string) ([]string, time.Duration, error) {
var txt []string
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn(hostname), dns.TypeTXT)
r, rtt, err := dnsResolver.LookupDNSSEC(m)
if err != nil {
return nil, 0, err
}
for _, answer := range r.Answer {
if answer.Header().Rrtype == dns.TypeTXT {
txtRec := answer.(*dns.TXT)
for _, field := range txtRec.Txt {
txt = append(txt, field)
}
}
}
return txt, rtt, err
}
func TestDNSSEC(t *testing.T) {
goodServer := NewDNSResolver(time.Second*10, []string{"8.8.8.8:53"})
m := new(dns.Msg)
m.SetQuestion(dns.Fqdn("sigfail.verteiltesysteme.net"), dns.TypeA)
_, _, err := goodServer.LookupDNSSEC(m)
test.AssertError(t, err, "DNSSEC failure")
_, ok := err.(DNSSECError)
test.Assert(t, ok, "Should have been a DNSSECError")
m.SetQuestion(dns.Fqdn("sigok.verteiltesysteme.net"), dns.TypeA)
_, _, err = goodServer.LookupDNSSEC(m)
test.AssertNotError(t, err, "DNSSEC should have worked")
badServer := NewDNSResolver(time.Second*10, []string{"127.0.0.1:99"})
_, _, err = badServer.LookupDNSSEC(m)
test.AssertError(t, err, "Should have failed")
_, ok = err.(DNSSECError)
test.Assert(t, !ok, "Shouldn't have been a DNSSECError")
}
func dnsHandler(w dns.ResponseWriter, r *dns.Msg) {
defer w.Close()
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
// Normally this test DNS server will return 127.0.0.1 for everything.
// However, in some situations (for instance Docker), it's useful to return a
// different hardcoded host. You can do so by setting the FAKE_DNS environment
// variable.
fakeDNS := os.Getenv("FAKE_DNS")
if fakeDNS == "" {
fakeDNS = "127.0.0.1"
}
for _, q := range r.Question {
fmt.Printf("dns-srv: Query -- [%s] %s\n", q.Name, dns.TypeToString[q.Qtype])
switch q.Qtype {
case dns.TypeA:
record := new(dns.A)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 0,
}
record.A = net.ParseIP(fakeDNS)
m.Answer = append(m.Answer, record)
case dns.TypeMX:
record := new(dns.MX)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeMX,
Class: dns.ClassINET,
Ttl: 0,
}
record.Mx = "mail." + q.Name
record.Preference = 10
m.Answer = append(m.Answer, record)
}
}
w.WriteMsg(m)
return
}
func dnsHandler(w dns.ResponseWriter, r *dns.Msg) {
defer w.Close()
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
for _, q := range r.Question {
fmt.Printf("dns-srv: Query -- [%s] %s\n", q.Name, dns.TypeToString[q.Qtype])
switch q.Qtype {
case dns.TypeA:
record := new(dns.A)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 0,
}
record.A = net.ParseIP("127.0.0.1")
m.Answer = append(m.Answer, record)
case dns.TypeMX:
record := new(dns.MX)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeMX,
Class: dns.ClassINET,
Ttl: 0,
}
record.Mx = "mail." + q.Name
record.Preference = 10
m.Answer = append(m.Answer, record)
}
}
w.WriteMsg(m)
return
}
func mockDNSQuery(w dns.ResponseWriter, r *dns.Msg) {
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
appendAnswer := func(rr dns.RR) {
m.Answer = append(m.Answer, rr)
}
for _, q := range r.Question {
q.Name = strings.ToLower(q.Name)
if q.Name == "servfail.com." {
m.Rcode = dns.RcodeServerFailure
break
}
switch q.Qtype {
case dns.TypeSOA:
record := new(dns.SOA)
record.Hdr = dns.RR_Header{Name: "letsencrypt.org.", Rrtype: dns.TypeSOA, Class: dns.ClassINET, Ttl: 0}
record.Ns = "ns.letsencrypt.org."
record.Mbox = "master.letsencrypt.org."
record.Serial = 1
record.Refresh = 1
record.Retry = 1
record.Expire = 1
record.Minttl = 1
appendAnswer(record)
case dns.TypeAAAA:
if q.Name == "v6.letsencrypt.org." {
record := new(dns.AAAA)
record.Hdr = dns.RR_Header{Name: "v6.letsencrypt.org.", Rrtype: dns.TypeAAAA, Class: dns.ClassINET, Ttl: 0}
record.AAAA = net.ParseIP("::1")
appendAnswer(record)
}
case dns.TypeA:
if q.Name == "cps.letsencrypt.org." {
record := new(dns.A)
record.Hdr = dns.RR_Header{Name: "cps.letsencrypt.org.", Rrtype: dns.TypeA, Class: dns.ClassINET, Ttl: 0}
record.A = net.ParseIP("127.0.0.1")
appendAnswer(record)
}
if q.Name == "nxdomain.letsencrypt.org." {
m.SetRcode(r, dns.RcodeNameError)
}
case dns.TypeCNAME:
if q.Name == "cname.letsencrypt.org." {
record := new(dns.CNAME)
record.Hdr = dns.RR_Header{Name: "cname.letsencrypt.org.", Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: 30}
record.Target = "cps.letsencrypt.org."
appendAnswer(record)
}
if q.Name == "cname.example.com." {
record := new(dns.CNAME)
record.Hdr = dns.RR_Header{Name: "cname.example.com.", Rrtype: dns.TypeCNAME, Class: dns.ClassINET, Ttl: 30}
record.Target = "CAA.example.com."
appendAnswer(record)
}
case dns.TypeDNAME:
if q.Name == "dname.letsencrypt.org." {
record := new(dns.DNAME)
record.Hdr = dns.RR_Header{Name: "dname.letsencrypt.org.", Rrtype: dns.TypeDNAME, Class: dns.ClassINET, Ttl: 30}
record.Target = "cps.letsencrypt.org."
appendAnswer(record)
}
case dns.TypeCAA:
if q.Name == "bracewel.net." || q.Name == "caa.example.com." {
record := new(dns.CAA)
record.Hdr = dns.RR_Header{Name: q.Name, Rrtype: dns.TypeCAA, Class: dns.ClassINET, Ttl: 0}
record.Tag = "issue"
record.Value = "letsencrypt.org"
record.Flag = 1
appendAnswer(record)
}
if q.Name == "cname.example.com." {
record := new(dns.CAA)
record.Hdr = dns.RR_Header{Name: "caa.example.com.", Rrtype: dns.TypeCAA, Class: dns.ClassINET, Ttl: 0}
record.Tag = "issue"
record.Value = "letsencrypt.org"
record.Flag = 1
appendAnswer(record)
}
case dns.TypeTXT:
if q.Name == "split-txt.letsencrypt.org." {
record := new(dns.TXT)
record.Hdr = dns.RR_Header{Name: "split-txt.letsencrypt.org.", Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}
record.Txt = []string{"a", "b", "c"}
appendAnswer(record)
} else {
auth := new(dns.SOA)
auth.Hdr = dns.RR_Header{Name: "letsencrypt.org.", Rrtype: dns.TypeSOA, Class: dns.ClassINET, Ttl: 0}
auth.Ns = "ns.letsencrypt.org."
auth.Mbox = "master.letsencrypt.org."
auth.Serial = 1
auth.Refresh = 1
auth.Retry = 1
auth.Expire = 1
auth.Minttl = 1
m.Ns = append(m.Ns, auth)
}
if q.Name == "nxdomain.letsencrypt.org." {
m.SetRcode(r, dns.RcodeNameError)
}
}
}
w.WriteMsg(m)
return
}
func (ts *testSrv) dnsHandler(w dns.ResponseWriter, r *dns.Msg) {
m := new(dns.Msg)
m.SetReply(r)
m.Compress = false
// Normally this test DNS server will return 127.0.0.1 for everything.
// However, in some situations (for instance Docker), it's useful to return a
// different hardcoded host. You can do so by setting the FAKE_DNS environment
// variable.
fakeDNS := os.Getenv("FAKE_DNS")
if fakeDNS == "" {
fakeDNS = "127.0.0.1"
}
for _, q := range r.Question {
fmt.Printf("dns-srv: Query -- [%s] %s\n", q.Name, dns.TypeToString[q.Qtype])
switch q.Qtype {
case dns.TypeA:
record := new(dns.A)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeA,
Class: dns.ClassINET,
Ttl: 0,
}
record.A = net.ParseIP(fakeDNS)
m.Answer = append(m.Answer, record)
case dns.TypeMX:
record := new(dns.MX)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeMX,
Class: dns.ClassINET,
Ttl: 0,
}
record.Mx = "mail." + q.Name
record.Preference = 10
m.Answer = append(m.Answer, record)
case dns.TypeTXT:
ts.mu.RLock()
value, present := ts.txtRecords[q.Name]
ts.mu.RUnlock()
if !present {
continue
}
record := new(dns.TXT)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeTXT,
Class: dns.ClassINET,
Ttl: 0,
}
record.Txt = []string{value}
m.Answer = append(m.Answer, record)
case dns.TypeCAA:
if q.Name == "bad-caa-reserved.com." || q.Name == "good-caa-reserved.com." {
record := new(dns.CAA)
record.Hdr = dns.RR_Header{
Name: q.Name,
Rrtype: dns.TypeCAA,
Class: dns.ClassINET,
Ttl: 0,
}
record.Tag = "issue"
if q.Name == "bad-caa-reserved.com." {
record.Value = "sad-hacker-ca.invalid"
} else if q.Name == "good-caa-reserved.com." {
record.Value = "happy-hacker-ca.invalid"
}
m.Answer = append(m.Answer, record)
}
}
}
auth := new(dns.SOA)
auth.Hdr = dns.RR_Header{Name: "boulder.invalid.", Rrtype: dns.TypeSOA, Class: dns.ClassINET, Ttl: 0}
auth.Ns = "ns.boulder.invalid."
auth.Mbox = "master.boulder.invalid."
auth.Serial = 1
auth.Refresh = 1
auth.Retry = 1
auth.Expire = 1
auth.Minttl = 1
m.Ns = append(m.Ns, auth)
w.WriteMsg(m)
return
}