1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
|
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) {
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)
go func() {
if q.Question[0].Qtype == TypeAXFR {
go t.inAxfr(q, env)
return
}
if q.Question[0].Qtype == TypeIXFR {
go t.inIxfr(q, env)
return
}
}()
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) {
serial := uint32(0) // 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 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
}
if _, err = t.Write(out); err != nil {
return err
}
return nil
}
func isSOAFirst(in *Msg) bool {
if len(in.Answer) > 0 {
return in.Answer[0].Header().Rrtype == TypeSOA
}
return false
}
func isSOALast(in *Msg) bool {
if len(in.Answer) > 0 {
return in.Answer[len(in.Answer)-1].Header().Rrtype == TypeSOA
}
return false
}
const errXFR = "bad xfr rcode: %d"
|
