1
2
3 """Domain Name System."""
4
5 import struct
6 import dpkt
7
8 DNS_Q = 0
9 DNS_R = 1
10
11
12 DNS_QUERY = 0
13 DNS_IQUERY = 1
14 DNS_STATUS = 2
15 DNS_NOTIFY = 4
16 DNS_UPDATE = 5
17
18
19 DNS_CD = 0x0010
20 DNS_AD = 0x0020
21 DNS_Z = 0x0040
22 DNS_RA = 0x0080
23 DNS_RD = 0x0100
24 DNS_TC = 0x0200
25 DNS_AA = 0x0400
26 DNS_QR = 0x8000
27
28
29 DNS_RCODE_NOERR = 0
30 DNS_RCODE_FORMERR = 1
31 DNS_RCODE_SERVFAIL = 2
32 DNS_RCODE_NXDOMAIN = 3
33 DNS_RCODE_NOTIMP = 4
34 DNS_RCODE_REFUSED = 5
35 DNS_RCODE_YXDOMAIN = 6
36 DNS_RCODE_YXRRSET = 7
37 DNS_RCODE_NXRRSET = 8
38 DNS_RCODE_NOTAUTH = 9
39 DNS_RCODE_NOTZONE = 10
40
41
42 DNS_A = 1
43 DNS_NS = 2
44 DNS_CNAME = 5
45 DNS_SOA = 6
46 DNS_PTR = 12
47 DNS_HINFO = 13
48 DNS_MX = 15
49 DNS_TXT = 16
50 DNS_AAAA = 28
51 DNS_SRV = 33
52
53
54 DNS_IN = 1
55 DNS_CHAOS = 3
56 DNS_HESIOD = 4
57 DNS_ANY = 255
58
60 if name:
61 labels = name.split('.')
62 else:
63 labels = []
64 labels.append('')
65 buf = ''
66 for i, label in enumerate(labels):
67 key = '.'.join(labels[i:]).upper()
68 ptr = label_ptrs.get(key)
69 if not ptr:
70 if len(key) > 1:
71 ptr = off + len(buf)
72 if ptr < 0xc000:
73 label_ptrs[key] = ptr
74 i = len(label)
75 buf += chr(i) + label
76 else:
77 buf += struct.pack('>H', (0xc000 | ptr))
78 break
79 return buf
80
104
105 -class DNS(dpkt.Packet):
106 __hdr__ = (
107 ('id', 'H', 0),
108 ('op', 'H', DNS_RD),
109
110 ('qd', 'H', []),
111 ('an', 'H', []),
112 ('ns', 'H', []),
113 ('ar', 'H', [])
114 )
120 qr = property(get_qr, set_qr)
121
123 return (self.op >> 11) & 0xf
125 self.op = (self.op & ~0x7800) | ((v & 0xf) << 11)
126 opcode = property(get_opcode, set_opcode)
127
133 aa = property(get_aa, set_aa)
134
140 rd = property(get_rd, set_rd)
141
147 ra = property(get_ra, set_ra)
148
154 zero = property(get_zero, set_zero)
155
159 self.op = (self.op & ~0xf) | (v & 0xf)
160 rcode = property(get_rcode, set_rcode)
161
162 - class Q(dpkt.Packet):
163 """DNS question."""
164 __hdr__ = (
165 ('name', '1025s', ''),
166 ('type', 'H', DNS_A),
167 ('cls', 'H', DNS_IN)
168 )
169
171 raise NotImplementedError
172 __str__ = __len__
174 raise NotImplementedError
175
177 """DNS resource record."""
178 __hdr__ = (
179 ('name', '1025s', ''),
180 ('type', 'H', DNS_A),
181 ('cls', 'H', DNS_IN),
182 ('ttl', 'I', 0),
183 ('rlen', 'H', 4),
184 ('rdata', 's', '')
185 )
187
188 if self.rdata:
189 return self.rdata
190 if self.type == DNS_A:
191 return self.ip
192 elif self.type == DNS_NS:
193 return pack_name(self.nsname, off, label_ptrs)
194 elif self.type == DNS_CNAME:
195 return pack_name(self.cname, off, label_ptrs)
196 elif self.type == DNS_PTR:
197 return pack_name(self.ptrname, off, label_ptrs)
198 elif self.type == DNS_SOA:
199 l = []
200 l.append(pack_name(self.mname, off, label_ptrs))
201 l.append(pack_name(self.rname, off + len(l[0]), label_ptrs))
202 l.append(struct.pack('>IIIII', self.serial, self.refresh,
203 self.retry, self.expire, self.minimum))
204 return ''.join(l)
205 elif self.type == DNS_MX:
206 return struct.pack('>H', self.preference) + \
207 pack_name(self.mxname, off + 2, label_ptrs)
208 elif self.type == DNS_TXT or self.type == DNS_HINFO:
209 return ''.join([ '%s%s' % (chr(len(x)), x)
210 for x in self.text ])
211 elif self.type == DNS_AAAA:
212 return self.ip6
213 elif self.type == DNS_SRV:
214 return struct.pack('>HHH', self.priority, self.weight, self.port) + \
215 pack_name(self.srvname, off + 6, label_ptrs)
216
218 if self.type == DNS_A:
219 self.ip = self.rdata
220 elif self.type == DNS_NS:
221 self.nsname, off = unpack_name(buf, off)
222 elif self.type == DNS_CNAME:
223 self.cname, off = unpack_name(buf, off)
224 elif self.type == DNS_PTR:
225 self.ptrname, off = unpack_name(buf, off)
226 elif self.type == DNS_SOA:
227 self.mname, off = unpack_name(buf, off)
228 self.rname, off = unpack_name(buf, off)
229 self.serial, self.refresh, self.retry, self.expire, \
230 self.minimum = struct.unpack('>IIIII', buf[off:off+20])
231 elif self.type == DNS_MX:
232 self.preference = struct.unpack('>H', self.rdata[:2])
233 self.mxname, off = unpack_name(buf, off+2)
234 elif self.type == DNS_TXT or self.type == DNS_HINFO:
235 self.text = []
236 buf = self.rdata
237 while buf:
238 n = ord(buf[0])
239 self.text.append(buf[1:1+n])
240 buf = buf[1+n:]
241 elif self.type == DNS_AAAA:
242 self.ip6 = self.rdata
243 elif self.type == DNS_SRV:
244 self.priority, self.weight, self.port = \
245 struct.unpack('>HHH', self.rdata[:6])
246 self.srvname, off = unpack_name(buf, off+6)
247
249 """Append packed DNS question and return buf."""
250 return buf + pack_name(q.name, len(buf), self.label_ptrs) + \
251 struct.pack('>HH', q.type, q.cls)
252
260
267
278
280 dpkt.Packet.unpack(self, buf)
281 off = self.__hdr_len__
282 cnt = self.qd
283 self.qd = []
284 for i in range(cnt):
285 q, off = self.unpack_q(buf, off)
286 self.qd.append(q)
287 for x in ('an', 'ns', 'ar'):
288 cnt = getattr(self, x, 0)
289 setattr(self, x, [])
290 for i in range(cnt):
291 rr, off = self.unpack_rr(buf, off)
292 getattr(self, x).append(rr)
293 self.data = ''
294
296
297 return len(str(self))
298
300
301 self.label_ptrs = {}
302 buf = struct.pack(self.__hdr_fmt__, self.id, self.op, len(self.qd),
303 len(self.an), len(self.ns), len(self.ar))
304 for q in self.qd:
305 buf = self.pack_q(buf, q)
306 for x in ('an', 'ns', 'ar'):
307 for rr in getattr(self, x):
308 buf = self.pack_rr(buf, rr)
309 del self.label_ptrs
310 return buf
311
312 if __name__ == '__main__':
313 import unittest
314 from ip import IP
315
318 s = 'E\x00\x02\x08\xc15\x00\x00\x80\x11\x92aBk0\x01Bk0w\x005\xc07\x01\xf4\xda\xc2d\xd2\x81\x80\x00\x01\x00\x03\x00\x0b\x00\x0b\x03www\x06google\x03com\x00\x00\x01\x00\x01\xc0\x0c\x00\x05\x00\x01\x00\x00\x03V\x00\x17\x03www\x06google\x06akadns\x03net\x00\xc0,\x00\x01\x00\x01\x00\x00\x01\xa3\x00\x04@\xe9\xabh\xc0,\x00\x01\x00\x01\x00\x00\x01\xa3\x00\x04@\xe9\xabc\xc07\x00\x02\x00\x01\x00\x00KG\x00\x0c\x04usw5\x04akam\xc0>\xc07\x00\x02\x00\x01\x00\x00KG\x00\x07\x04usw6\xc0t\xc07\x00\x02\x00\x01\x00\x00KG\x00\x07\x04usw7\xc0t\xc07\x00\x02\x00\x01\x00\x00KG\x00\x08\x05asia3\xc0t\xc07\x00\x02\x00\x01\x00\x00KG\x00\x05\x02za\xc07\xc07\x00\x02\x00\x01\x00\x00KG\x00\x0f\x02zc\x06akadns\x03org\x00\xc07\x00\x02\x00\x01\x00\x00KG\x00\x05\x02zf\xc07\xc07\x00\x02\x00\x01\x00\x00KG\x00\x05\x02zh\xc0\xd5\xc07\x00\x02\x00\x01\x00\x00KG\x00\x07\x04eur3\xc0t\xc07\x00\x02\x00\x01\x00\x00KG\x00\x07\x04use2\xc0t\xc07\x00\x02\x00\x01\x00\x00KG\x00\x07\x04use4\xc0t\xc0\xc1\x00\x01\x00\x01\x00\x00\xfb4\x00\x04\xd0\xb9\x84\xb0\xc0\xd2\x00\x01\x00\x01\x00\x001\x0c\x00\x04?\xf1\xc76\xc0\xed\x00\x01\x00\x01\x00\x00\xfb4\x00\x04?\xd7\xc6S\xc0\xfe\x00\x01\x00\x01\x00\x001\x0c\x00\x04?\xd00.\xc1\x0f\x00\x01\x00\x01\x00\x00\n\xdf\x00\x04\xc1-\x01g\xc1"\x00\x01\x00\x01\x00\x00\x101\x00\x04?\xd1\xaa\x88\xc15\x00\x01\x00\x01\x00\x00\r\x1a\x00\x04PCC\xb6\xc0o\x00\x01\x00\x01\x00\x00\x10\x7f\x00\x04?\xf1I\xd6\xc0\x87\x00\x01\x00\x01\x00\x00\n\xdf\x00\x04\xce\x84dl\xc0\x9a\x00\x01\x00\x01\x00\x00\n\xdf\x00\x04A\xcb\xea\x1b\xc0\xad\x00\x01\x00\x01\x00\x00\x0b)\x00\x04\xc1l\x9a\t'
319 ip = IP(s)
320 dns = DNS(ip.udp.data)
321 self.failUnless(dns.qd[0].name == 'www.google.com' and
322 dns.an[1].name == 'www.google.akadns.net')
323 s = '\x05\xf5\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x03cnn\x03com\x00\x00\x01\x00\x01'
324 dns = DNS(s)
325 self.failUnless(s == str(dns))
326
328 s = 'g\x02\x81\x80\x00\x01\x00\x01\x00\x03\x00\x00\x011\x011\x03211\x03141\x07in-addr\x04arpa\x00\x00\x0c\x00\x01\xc0\x0c\x00\x0c\x00\x01\x00\x00\r6\x00$\x07default\nv-umce-ifs\x05umnet\x05umich\x03edu\x00\xc0\x0e\x00\x02\x00\x01\x00\x00\r6\x00\r\x06shabby\x03ifs\xc0O\xc0\x0e\x00\x02\x00\x01\x00\x00\r6\x00\x0f\x0cfish-license\xc0m\xc0\x0e\x00\x02\x00\x01\x00\x00\r6\x00\x0b\x04dns2\x03itd\xc0O'
329 dns = DNS(s)
330 self.failUnless(dns.qd[0].name == '1.1.211.141.in-addr.arpa' and
331 dns.an[0].ptrname == 'default.v-umce-ifs.umnet.umich.edu' and
332 dns.ns[0].nsname == 'shabby.ifs.umich.edu' and
333 dns.ns[1].ttl == 3382L and
334 dns.ns[2].nsname == 'dns2.itd.umich.edu')
335 self.failUnless(s == str(dns))
336
338
339 x = pack_name('', 0, {})
340 self.assertEqual(x, '\0')
341
342 unittest.main()
343