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@miekg @StalkR @tmthrgd @flebarbe @TimSimmons @r4um @NullOranje @kahnert @matje @gavaletz
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package dns
import (
"fmt"
"time"
)
// Envelope is used when doing a zone transfer with a remote server.
type Envelope struct {
RR []RR // The set of RRs in the answer section of the xfr reply message.
Error error // If something went wrong, this contains the error.
}
// A Transfer defines parameters that are used during a zone transfer.
type Transfer struct {
*Conn
DialTimeout time.Duration // net.DialTimeout, defaults to 2 seconds
ReadTimeout time.Duration // net.Conn.SetReadTimeout value for connections, defaults to 2 seconds
WriteTimeout time.Duration // net.Conn.SetWriteTimeout value for connections, defaults to 2 seconds
TsigSecret map[string]string // Secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
tsigTimersOnly bool
}
// Think we need to away to stop the transfer
// In performs an incoming transfer with the server in a.
// If you would like to set the source IP, or some other attribute
// of a Dialer for a Transfer, you can do so by specifying the attributes
// in the Transfer.Conn:
//
// d := net.Dialer{LocalAddr: transfer_source}
// con, err := d.Dial("tcp", master)
// dnscon := &dns.Conn{Conn:con}
// transfer = &dns.Transfer{Conn: dnscon}
// channel, err := transfer.In(message, master)
//
func (t *Transfer) In(q *Msg, a string) (env chan *Envelope, err error) {
switch q.Question[0].Qtype {
case TypeAXFR, TypeIXFR:
default:
return nil, &Error{"unsupported question type"}
}
timeout := dnsTimeout
if t.DialTimeout != 0 {
timeout = t.DialTimeout
}
if t.Conn == nil {
t.Conn, err = DialTimeout("tcp", a, timeout)
if err != nil {
return nil, err
}
}
if err := t.WriteMsg(q); err != nil {
return nil, err
}
env = make(chan *Envelope)
switch q.Question[0].Qtype {
case TypeAXFR:
go t.inAxfr(q, env)
case TypeIXFR:
go t.inIxfr(q, env)
}
return env, nil
}
func (t *Transfer) inAxfr(q *Msg, c chan *Envelope) {
first := true
defer t.Close()
defer close(c)
timeout := dnsTimeout
if t.ReadTimeout != 0 {
timeout = t.ReadTimeout
}
for {
t.Conn.SetReadDeadline(time.Now().Add(timeout))
in, err := t.ReadMsg()
if err != nil {
c <- &Envelope{nil, err}
return
}
if q.Id != in.Id {
c <- &Envelope{in.Answer, ErrId}
return
}
if first {
if in.Rcode != RcodeSuccess {
c <- &Envelope{in.Answer, &Error{err: fmt.Sprintf(errXFR, in.Rcode)}}
return
}
if !isSOAFirst(in) {
c <- &Envelope{in.Answer, ErrSoa}
return
}
first = !first
// only one answer that is SOA, receive more
if len(in.Answer) == 1 {
t.tsigTimersOnly = true
c <- &Envelope{in.Answer, nil}
continue
}
}
if !first {
t.tsigTimersOnly = true // Subsequent envelopes use this.
if isSOALast(in) {
c <- &Envelope{in.Answer, nil}
return
}
c <- &Envelope{in.Answer, nil}
}
}
}
func (t *Transfer) inIxfr(q *Msg, c chan *Envelope) {
var serial uint32 // The first serial seen is the current server serial
axfr := true
n := 0
qser := q.Ns[0].(*SOA).Serial
defer t.Close()
defer close(c)
timeout := dnsTimeout
if t.ReadTimeout != 0 {
timeout = t.ReadTimeout
}
for {
t.SetReadDeadline(time.Now().Add(timeout))
in, err := t.ReadMsg()
if err != nil {
c <- &Envelope{nil, err}
return
}
if q.Id != in.Id {
c <- &Envelope{in.Answer, ErrId}
return
}
if in.Rcode != RcodeSuccess {
c <- &Envelope{in.Answer, &Error{err: fmt.Sprintf(errXFR, in.Rcode)}}
return
}
if n == 0 {
// Check if the returned answer is ok
if !isSOAFirst(in) {
c <- &Envelope{in.Answer, ErrSoa}
return
}
// This serial is important
serial = in.Answer[0].(*SOA).Serial
// Check if there are no changes in zone
if qser >= serial {
c <- &Envelope{in.Answer, nil}
return
}
}
// Now we need to check each message for SOA records, to see what we need to do
t.tsigTimersOnly = true
for _, rr := range in.Answer {
if v, ok := rr.(*SOA); ok {
if v.Serial == serial {
n++
// quit if it's a full axfr or the the servers' SOA is repeated the third time
if axfr && n == 2 || n == 3 {
c <- &Envelope{in.Answer, nil}
return
}
} else if axfr {
// it's an ixfr
axfr = false
}
}
}
c <- &Envelope{in.Answer, nil}
}
}
// Out performs an outgoing transfer with the client connecting in w.
// Basic use pattern:
//
// ch := make(chan *dns.Envelope)
// tr := new(dns.Transfer)
// go tr.Out(w, r, ch)
// ch <- &dns.Envelope{RR: []dns.RR{soa, rr1, rr2, rr3, soa}}
// close(ch)
// w.Hijack()
// // w.Close() // Client closes connection
//
// The server is responsible for sending the correct sequence of RRs through the
// channel ch.
func (t *Transfer) Out(w ResponseWriter, q *Msg, ch chan *Envelope) error {
for x := range ch {
r := new(Msg)
// Compress?
r.SetReply(q)
r.Authoritative = true
// assume it fits TODO(miek): fix
r.Answer = append(r.Answer, x.RR...)
if tsig := q.IsTsig(); tsig != nil && w.TsigStatus() == nil {
r.SetTsig(tsig.Hdr.Name, tsig.Algorithm, tsig.Fudge, time.Now().Unix())
}
if err := w.WriteMsg(r); err != nil {
return err
}
w.TsigTimersOnly(true)
}
return nil
}
// ReadMsg reads a message from the transfer connection t.
func (t *Transfer) ReadMsg() (*Msg, error) {
m := new(Msg)
p := make([]byte, MaxMsgSize)
n, err := t.Read(p)
if err != nil && n == 0 {
return nil, err
}
p = p[:n]
if err := m.Unpack(p); err != nil {
return nil, err
}
if ts := m.IsTsig(); ts != nil && t.TsigSecret != nil {
if _, ok := t.TsigSecret[ts.Hdr.Name]; !ok {
return m, ErrSecret
}
// Need to work on the original message p, as that was used to calculate the tsig.
err = TsigVerify(p, t.TsigSecret[ts.Hdr.Name], t.tsigRequestMAC, t.tsigTimersOnly)
t.tsigRequestMAC = ts.MAC
}
return m, err
}
// WriteMsg writes a message through the transfer connection t.
func (t *Transfer) WriteMsg(m *Msg) (err error) {
var out []byte
if ts := m.IsTsig(); ts != nil && t.TsigSecret != nil {
if _, ok := t.TsigSecret[ts.Hdr.Name]; !ok {
return ErrSecret
}
out, t.tsigRequestMAC, err = TsigGenerate(m, t.TsigSecret[ts.Hdr.Name], t.tsigRequestMAC, t.tsigTimersOnly)
} else {
out, err = m.Pack()
}
if err != nil {
return err
}
_, err = t.Write(out)
return err
}
func isSOAFirst(in *Msg) bool {
return len(in.Answer) > 0 &&
in.Answer[0].Header().Rrtype == TypeSOA
}
func isSOALast(in *Msg) bool {
return len(in.Answer) > 0 &&
in.Answer[len(in.Answer)-1].Header().Rrtype == TypeSOA
}
const errXFR = "bad xfr rcode: %d"
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