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Fix responses to be more standards compliant (#145)

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* Handle OPT questions (EDNS)

* Handle authoritative bit, and append SOA for authoritative NXDOMAIN responses

* Changelog entry

* Fix linter errors
This commit is contained in:
Joona Hoikkala 2019-02-03 20:19:15 +02:00 committed by GitHub
parent 7a2f9f06b1
commit de7fe3cb1d
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 96 additions and 29 deletions
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6
README.md
View File

@ -326,10 +326,12 @@ logformat = "text"
## Changelog
- master
- Unreleased
- Added new endpoint to perform health checks
- Added
- New endpoint to perform health checks
- Changed
- A new protocol selection for DNS server "both", that binds both - UDP and TCP ports.
- Refactored DNS server internals.
- Handle some aspects of DNS spec better.
- v0.6
- New
- Command line flag `-c` to specify location of config file.

43
dns.go
View File

@ -17,6 +17,7 @@ type Records struct {
type DNSServer struct {
DB database
Server *dns.Server
SOA dns.RR
Domains map[string]Records
}
@ -60,6 +61,7 @@ func (d *DNSServer) ParseRecords(config DNSConfig) {
log.WithFields(log.Fields{"error": err.Error(), "soa": SOAstring}).Error("Error while adding SOA record")
} else {
d.appendRR(soarr)
d.SOA = soarr
}
}
@ -91,14 +93,25 @@ func (d *DNSServer) handleRequest(w dns.ResponseWriter, r *dns.Msg) {
}
func (d *DNSServer) readQuery(m *dns.Msg) {
var authoritative = false
for _, que := range m.Question {
if rr, rc, err := d.answer(que); err == nil {
if rr, rc, auth, err := d.answer(que); err == nil {
if auth {
authoritative = auth
}
m.MsgHdr.Rcode = rc
for _, r := range rr {
m.Answer = append(m.Answer, r)
}
}
}
m.MsgHdr.Authoritative = authoritative
if authoritative {
if m.MsgHdr.Rcode == dns.RcodeNameError {
m.Answer = append(m.Answer, d.SOA)
}
}
}
func (d *DNSServer) getRecord(q dns.Question) ([]dns.RR, error) {
@ -123,14 +136,28 @@ func (d *DNSServer) getRecord(q dns.Question) ([]dns.RR, error) {
}
// answeringForDomain checks if we have any records for a domain
func (d *DNSServer) answeringForDomain(q dns.Question) bool {
_, ok := d.Domains[q.Name]
func (d *DNSServer) answeringForDomain(name string) bool {
_, ok := d.Domains[name]
return ok
}
func (d *DNSServer) answer(q dns.Question) ([]dns.RR, int, error) {
func (d *DNSServer) isAuthoritative(q dns.Question) bool {
if d.answeringForDomain(q.Name) {
return true
}
domainParts := strings.Split(q.Name, ".")
for i := range domainParts {
if d.answeringForDomain(strings.Join(domainParts[i:], ".")) {
return true
}
}
return false
}
func (d *DNSServer) answer(q dns.Question) ([]dns.RR, int, bool, error) {
var rcode int
if !d.answeringForDomain(q) {
var authoritative = d.isAuthoritative(q)
if !d.answeringForDomain(q.Name) {
rcode = dns.RcodeNameError
}
r, _ := d.getRecord(q)
@ -146,8 +173,12 @@ func (d *DNSServer) answer(q dns.Question) ([]dns.RR, int, error) {
// Make sure that we return NOERROR if there were dynamic records for the domain
rcode = dns.RcodeSuccess
}
// Handle EDNS (no support at the moment)
if q.Qtype == dns.TypeOPT {
return []dns.RR{}, dns.RcodeFormatError, authoritative, nil
}
log.WithFields(log.Fields{"qtype": dns.TypeToString[q.Qtype], "domain": q.Name, "rcode": dns.RcodeToString[rcode]}).Debug("Answering question for domain")
return r, rcode, nil
return r, rcode, authoritative, nil
}
func (d *DNSServer) answerTXT(q dns.Question) ([]dns.RR, error) {

76
dns_test.go
View File

@ -18,20 +18,20 @@ type resolver struct {
server string
}
func (r *resolver) lookup(host string, qtype uint16) ([]dns.RR, error) {
func (r *resolver) lookup(host string, qtype uint16) (*dns.Msg, error) {
msg := new(dns.Msg)
msg.Id = dns.Id()
msg.Question = make([]dns.Question, 1)
msg.Question[0] = dns.Question{Name: dns.Fqdn(host), Qtype: qtype, Qclass: dns.ClassINET}
in, err := dns.Exchange(msg, r.server)
if err != nil {
return []dns.RR{}, fmt.Errorf("Error querying the server [%v]", err)
return in, fmt.Errorf("Error querying the server [%v]", err)
}
if in != nil && in.Rcode != dns.RcodeSuccess {
return []dns.RR{}, fmt.Errorf("Received error from the server [%s]", dns.RcodeToString[in.Rcode])
return in, fmt.Errorf("Received error from the server [%s]", dns.RcodeToString[in.Rcode])
}
return in.Answer, nil
return in, nil
}
func hasExpectedTXTAnswer(answer []dns.RR, cmpTXT string) error {
@ -98,7 +98,7 @@ func TestResolveA(t *testing.T) {
t.Errorf("%v", err)
}
if len(answer) == 0 {
if len(answer.Answer) == 0 {
t.Error("No answer for DNS query")
}
@ -108,6 +108,14 @@ func TestResolveA(t *testing.T) {
}
}
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.RcodeFormatError {
t.Errorf("Was expecing FORMERR rcode for OPT query, but got [%s] instead.", dns.RcodeToString[answer.Rcode])
}
}
func TestOpcodeUpdate(t *testing.T) {
msg := new(dns.Msg)
msg.Id = dns.Id()
@ -131,14 +139,38 @@ func TestResolveCNAME(t *testing.T) {
if err != nil {
t.Errorf("Got unexpected error: %s", err)
}
if len(answer) != 1 {
t.Errorf("Expected exactly 1 RR in answer, but got %d instead.", len(answer))
if len(answer.Answer) != 1 {
t.Errorf("Expected exactly 1 RR in answer, but got %d instead.", len(answer.Answer))
}
if answer[0].Header().Rrtype != dns.TypeCNAME {
t.Errorf("Expected a CNAME answer, but got [%s] instead.", dns.TypeToString[answer[0].Header().Rrtype])
if answer.Answer[0].Header().Rrtype != dns.TypeCNAME {
t.Errorf("Expected a CNAME answer, but got [%s] instead.", dns.TypeToString[answer.Answer[0].Header().Rrtype])
}
if answer[0].String() != expected {
t.Errorf("Expected CNAME answer [%s] but got [%s] instead.", expected, answer[0].String())
if answer.Answer[0].String() != expected {
t.Errorf("Expected CNAME answer [%s] but got [%s] instead.", expected, answer.Answer[0].String())
}
}
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])
}
if len(answer.Answer) != 1 {
t.Errorf("Was expecting exactly one answer (SOA) for invalid subdomain, but got %d", len(answer.Answer))
}
if answer.Answer[0].Header().Rrtype != dns.TypeSOA {
t.Errorf("Was expecting SOA record as answer for NXDOMAIN but got [%s]", dns.TypeToString[answer.Answer[0].Header().Rrtype])
}
if !answer.MsgHdr.Authoritative {
t.Errorf("Was expecting authoritative bit to be set")
}
nanswer, _ := resolv.lookup("nonexsitent.nonauth.tld", dns.TypeA)
if len(nanswer.Answer) > 0 {
t.Errorf("Didn't expect answers for non authotitative domain query")
}
if nanswer.MsgHdr.Authoritative {
t.Errorf("Authoritative bit should not be set for non-authoritative domain.")
}
}
@ -179,18 +211,20 @@ func TestResolveTXT(t *testing.T) {
}
}
if len(answer) > 0 {
if !test.getAnswer {
if len(answer.Answer) > 0 {
if !test.getAnswer && answer.Answer[0].Header().Rrtype != dns.TypeSOA {
t.Errorf("Test %d: Expected no answer, but got: [%q]", i, answer)
}
err = hasExpectedTXTAnswer(answer, test.expTXT)
if err != nil {
if test.validAnswer {
t.Errorf("Test %d: %v", i, err)
}
} else {
if !test.validAnswer {
t.Errorf("Test %d: Answer was not expected to be valid, answer [%q], compared to [%s]", i, answer, test.expTXT)
if test.getAnswer {
err = hasExpectedTXTAnswer(answer.Answer, test.expTXT)
if err != nil {
if test.validAnswer {
t.Errorf("Test %d: %v", i, err)
}
} else {
if !test.validAnswer {
t.Errorf("Test %d: Answer was not expected to be valid, answer [%q], compared to [%s]", i, answer, test.expTXT)
}
}
}
} else {