Package dpkt :: Module dns
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Source Code for Module dpkt.dns

  1  # $Id: dns.py 27 2006-11-21 01:22:52Z dahelder $ 
  2   
  3  """Domain Name System.""" 
  4   
  5  import struct 
  6  import dpkt 
  7   
  8  DNS_Q = 0 
  9  DNS_R = 1 
 10   
 11  # Opcodes 
 12  DNS_QUERY = 0 
 13  DNS_IQUERY = 1 
 14  DNS_STATUS = 2 
 15  DNS_NOTIFY = 4 
 16  DNS_UPDATE = 5 
 17   
 18  # Flags 
 19  DNS_CD = 0x0010 # checking disabled 
 20  DNS_AD = 0x0020 # authenticated data 
 21  DNS_Z =  0x0040 # unused 
 22  DNS_RA = 0x0080 # recursion available 
 23  DNS_RD = 0x0100 # recursion desired 
 24  DNS_TC = 0x0200 # truncated 
 25  DNS_AA = 0x0400 # authoritative answer 
 26   
 27  # Response codes 
 28  DNS_RCODE_NOERR = 0 
 29  DNS_RCODE_FORMERR = 1 
 30  DNS_RCODE_SERVFAIL = 2 
 31  DNS_RCODE_NXDOMAIN = 3 
 32  DNS_RCODE_NOTIMP = 4 
 33  DNS_RCODE_REFUSED = 5 
 34  DNS_RCODE_YXDOMAIN = 6 
 35  DNS_RCODE_YXRRSET = 7 
 36  DNS_RCODE_NXRRSET = 8 
 37  DNS_RCODE_NOTAUTH = 9 
 38  DNS_RCODE_NOTZONE = 10 
 39   
 40  # RR types 
 41  DNS_A = 1 
 42  DNS_NS = 2 
 43  DNS_CNAME = 5 
 44  DNS_SOA = 6 
 45  DNS_PTR = 12 
 46  DNS_HINFO = 13 
 47  DNS_MX = 15 
 48  DNS_TXT = 16 
 49  DNS_AAAA = 28 
 50  DNS_SRV = 33 
 51   
 52  # RR classes 
 53  DNS_IN = 1 
 54  DNS_CHAOS = 3 
 55  DNS_HESIOD = 4 
 56  DNS_ANY = 255 
 57   
58 -def pack_name(name, off, label_ptrs):
59 if name: 60 labels = name.split('.') 61 else: 62 labels = [] 63 labels.append('') 64 buf = '' 65 for i, label in enumerate(labels): 66 key = '.'.join(labels[i:]).upper() 67 ptr = label_ptrs.get(key) 68 if not ptr: 69 if len(key) > 1: 70 ptr = off + len(buf) 71 if ptr < 0xc000: 72 label_ptrs[key] = ptr 73 i = len(label) 74 buf += chr(i) + label 75 else: 76 buf += struct.pack('>H', (0xc000 | ptr)) 77 break 78 return buf
79
80 -def unpack_name(buf, off):
81 name = '' 82 saved_off = 0 83 for i in range(100): # XXX 84 n = ord(buf[off]) 85 if n == 0: 86 off += 1 87 break 88 elif (n & 0xc0) == 0xc0: 89 ptr = struct.unpack('>H', buf[off:off+2])[0] & 0x3fff 90 off += 2 91 if not saved_off: 92 saved_off = off 93 # XXX - don't use recursion!@#$ 94 name = name + unpack_name(buf, ptr)[0] + '.' 95 break 96 else: 97 off += 1 98 name = name + buf[off:off+n] + '.' 99 if len(name) > 255: 100 raise dpkt.UnpackError('name longer than 255 bytes') 101 off += n 102 return name.strip('.'), off
103
104 -class DNS(dpkt.Packet):
105 __hdr__ = ( 106 ('id', 'H', 0), 107 ('op', 'H', DNS_RD), # recursive query 108 # XXX - lists of query, RR objects 109 ('qd', 'H', []), 110 ('an', 'H', []), 111 ('ns', 'H', []), 112 ('ar', 'H', []) 113 )
114 - def get_qr(self):
115 return int((self.op & 0x8000) == 0x8000)
116 - def set_qr(self, v):
117 if v: self.op |= 0x8000 118 else: self.op &= ~0x8000
119 qr = property(get_qr, set_qr) 120
121 - def get_opcode(self):
122 return (self.op >> 11) & 0xf
123 - def set_opcode(self, v):
124 self.op = (self.op & ~0x7800) | ((v & 0xf) << 11)
125 opcode = property(get_opcode, set_opcode) 126
127 - def get_rcode(self):
128 return self.op & 0xf
129 - def set_rcode(self, v):
130 self.op = (self.op & ~0xf) | (v & 0xf)
131 rcode = property(get_rcode, set_rcode) 132
133 - class Q(dpkt.Packet):
134 """DNS question.""" 135 __hdr__ = ( 136 ('name', '1025s', ''), 137 ('type', 'H', DNS_A), 138 ('cls', 'H', DNS_IN) 139 ) 140 # XXX - suk
141 - def __len__(self):
142 raise NotImplementedError
143 __str__ = __len__
144 - def unpack(self, buf):
145 raise NotImplementedError
146
147 - class RR(Q):
148 """DNS resource record.""" 149 __hdr__ = ( 150 ('name', '1025s', ''), 151 ('type', 'H', DNS_A), 152 ('cls', 'H', DNS_IN), 153 ('ttl', 'I', 0), 154 ('rlen', 'H', 4), 155 ('rdata', 's', '') 156 )
157 - def pack_rdata(self, off, label_ptrs):
158 # XXX - yeah, this sux 159 if self.rdata: 160 return self.rdata 161 if self.type == DNS_A: 162 return self.ip 163 elif self.type == DNS_NS: 164 return pack_name(self.nsname, off, label_ptrs) 165 elif self.type == DNS_CNAME: 166 return pack_name(self.cname, off, label_ptrs) 167 elif self.type == DNS_PTR: 168 return pack_name(self.ptrname, off, label_ptrs) 169 elif self.type == DNS_SOA: 170 l = [] 171 l.append(pack_name(self.mname, off, label_ptrs)) 172 l.append(pack_name(self.rname, off + len(l[0]), label_ptrs)) 173 l.append(struct.pack('>IIIII', self.serial, self.refresh, 174 self.retry, self.expire, self.minimum)) 175 return ''.join(l) 176 elif self.type == DNS_MX: 177 return struct.pack('>H', self.preference) + \ 178 pack_name(self.mxname, off + 2, label_ptrs) 179 elif self.type == DNS_TXT or self.type == DNS_HINFO: 180 return ''.join([ '%s%s' % (chr(len(x)), x) 181 for x in self.text ]) 182 elif self.type == DNS_AAAA: 183 return self.ip6 184 elif self.type == DNS_SRV: 185 return struct.pack('>HHH', self.priority, self.weight, self.port) + \ 186 pack_name(self.srvname, off + 6, label_ptrs)
187
188 - def unpack_rdata(self, buf, off):
189 if self.type == DNS_A: 190 self.ip = self.rdata 191 elif self.type == DNS_NS: 192 self.nsname, off = unpack_name(buf, off) 193 elif self.type == DNS_CNAME: 194 self.cname, off = unpack_name(buf, off) 195 elif self.type == DNS_PTR: 196 self.ptrname, off = unpack_name(buf, off) 197 elif self.type == DNS_SOA: 198 self.mname, off = unpack_name(buf, off) 199 self.rname, off = unpack_name(buf, off) 200 self.serial, self.refresh, self.retry, self.expire, \ 201 self.minimum = struct.unpack('>IIIII', buf[off:off+20]) 202 elif self.type == DNS_MX: 203 self.preference = struct.unpack('>H', self.rdata[:2]) 204 self.mxname, off = unpack_name(buf, off+2) 205 elif self.type == DNS_TXT or self.type == DNS_HINFO: 206 self.text = [] 207 buf = self.rdata 208 while buf: 209 n = ord(buf[0]) 210 self.text.append(buf[1:1+n]) 211 buf = buf[1+n:] 212 elif self.type == DNS_AAAA: 213 self.ip6 = self.rdata 214 elif self.type == DNS_SRV: 215 self.priority, self.weight, self.port = \ 216 struct.unpack('>HHH', self.rdata[:6]) 217 self.srvname, off = unpack_name(buf, off+6)
218
219 - def pack_q(self, buf, q):
220 """Append packed DNS question and return buf.""" 221 return buf + pack_name(q.name, len(buf), self.label_ptrs) + \ 222 struct.pack('>HH', q.type, q.cls)
223
224 - def unpack_q(self, buf, off):
225 """Return DNS question and new offset.""" 226 q = self.Q() 227 q.name, off = unpack_name(buf, off) 228 q.type, q.cls = struct.unpack('>HH', buf[off:off+4]) 229 off += 4 230 return q, off
231
232 - def pack_rr(self, buf, rr):
233 """Append packed DNS RR and return buf.""" 234 name = pack_name(rr.name, len(buf), self.label_ptrs) 235 rdata = rr.pack_rdata(len(buf) + len(name) + 10, self.label_ptrs) 236 return buf + name + struct.pack('>HHIH', rr.type, rr.cls, rr.ttl, 237 len(rdata)) + rdata
238
239 - def unpack_rr(self, buf, off):
240 """Return DNS RR and new offset.""" 241 rr = self.RR() 242 rr.name, off = unpack_name(buf, off) 243 rr.type, rr.cls, rr.ttl, rdlen = struct.unpack('>HHIH', buf[off:off+10]) 244 off += 10 245 rr.rdata = buf[off:off+rdlen] 246 rr.unpack_rdata(buf, off) 247 off += rdlen 248 return rr, off
249
250 - def unpack(self, buf):
251 dpkt.Packet.unpack(self, buf) 252 off = self.__hdr_len__ 253 cnt = self.qd 254 self.qd = [] 255 for i in range(cnt): 256 q, off = self.unpack_q(buf, off) 257 self.qd.append(q) 258 for x in ('an', 'ns', 'ar'): 259 cnt = getattr(self, x, 0) 260 setattr(self, x, []) 261 for i in range(cnt): 262 rr, off = self.unpack_rr(buf, off) 263 getattr(self, x).append(rr) 264 self.data = ''
265
266 - def __len__(self):
267 # XXX - cop out 268 return len(str(self))
269
270 - def __str__(self):
271 # XXX - compress names on the fly 272 self.label_ptrs = {} 273 buf = struct.pack(self.__hdr_fmt__, self.id, self.op, len(self.qd), 274 len(self.an), len(self.ns), len(self.ar)) 275 for q in self.qd: 276 buf = self.pack_q(buf, q) 277 for x in ('an', 'ns', 'ar'): 278 for rr in getattr(self, x): 279 buf = self.pack_rr(buf, rr) 280 del self.label_ptrs 281 return buf
282 283 if __name__ == '__main__': 284 import unittest 285 from ip import IP 286
287 - class DNSTestCase(unittest.TestCase):
288 - def test_basic(self):
289 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' 290 ip = IP(s) 291 dns = DNS(ip.udp.data) 292 self.failUnless(dns.qd[0].name == 'www.google.com' and 293 dns.an[1].name == 'www.google.akadns.net') 294 s = '\x05\xf5\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x03cnn\x03com\x00\x00\x01\x00\x01' 295 dns = DNS(s) 296 self.failUnless(s == str(dns))
297
298 - def test_PTR(self):
299 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' 300 dns = DNS(s) 301 self.failUnless(dns.qd[0].name == '1.1.211.141.in-addr.arpa' and 302 dns.an[0].ptrname == 'default.v-umce-ifs.umnet.umich.edu' and 303 dns.ns[0].nsname == 'shabby.ifs.umich.edu' and 304 dns.ns[1].ttl == 3382L and 305 dns.ns[2].nsname == 'dns2.itd.umich.edu') 306 self.failUnless(s == str(dns))
307
308 - def test_pack_name(self):
309 # Empty name is \0 310 x = pack_name('', 0, {}) 311 self.assertEqual(x, '\0')
312 313 unittest.main() 314