Package dpkt :: Module dns
[hide private]
[frames] | no frames]

Source Code for Module dpkt.dns

  1  # $Id: dns.py 290 2006-01-22 02:43:28Z dugsong $ 
  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 labels = name.split('.') 60 labels.append('') 61 buf = '' 62 for i, label in enumerate(labels): 63 key = '.'.join(labels[i:]).upper() 64 ptr = label_ptrs.get(key) 65 if not ptr: 66 if len(key) > 1: 67 ptr = off + len(buf) 68 if ptr < 0xc000: 69 label_ptrs[key] = ptr 70 i = len(label) 71 buf += chr(i) + label 72 else: 73 buf += struct.pack('>H', (0xc000 | ptr)) 74 break 75 return buf
76
77 -def unpack_name(buf, off):
78 name = '' 79 saved_off = 0 80 for i in range(100): # XXX 81 n = ord(buf[off]) 82 if n == 0: 83 off += 1 84 break 85 elif (n & 0xc0) == 0xc0: 86 ptr = struct.unpack('>H', buf[off:off+2])[0] & 0x3fff 87 off += 2 88 if not saved_off: 89 saved_off = off 90 # XXX - don't use recursion!@#$ 91 name = name + unpack_name(buf, ptr)[0] + '.' 92 break 93 else: 94 off += 1 95 name = name + buf[off:off+n] + '.' 96 if len(name) > 255: 97 raise dpkt.UnpackError('name longer than 255 bytes') 98 off += n 99 return name.strip('.'), off
100
101 -class DNS(dpkt.Packet):
102 __hdr__ = ( 103 ('id', 'H', 0), 104 ('op', 'H', DNS_RD), # recursive query 105 # XXX - lists of query, RR objects 106 ('qd', 'H', []), 107 ('an', 'H', []), 108 ('ns', 'H', []), 109 ('ar', 'H', []) 110 )
111 - def get_qr(self):
112 return int((self.op & 0x8000) == 0x8000)
113 - def set_qr(self, v):
114 if v: self.op |= 0x8000 115 else: self.op &= ~0x8000
116 qr = property(get_qr, set_qr) 117
118 - def get_opcode(self):
119 return (self.op >> 11) & 0xf
120 - def set_opcode(self, v):
121 self.op = (self.op & ~0x7800) | ((v & 0xf) << 11)
122 opcode = property(get_opcode, set_opcode) 123
124 - def get_rcode(self):
125 return self.op & 0xf
126 - def set_rcode(self, v):
127 self.op = (self.op & ~0xf) | (v & 0xf)
128 rcode = property(get_rcode, set_rcode) 129
130 - class Q(dpkt.Packet):
131 """DNS question.""" 132 __hdr__ = ( 133 ('name', '1025s', ''), 134 ('type', 'H', DNS_A), 135 ('cls', 'H', DNS_IN) 136 ) 137 # XXX - suk
138 - def __len__(self):
139 raise NotImplementedError
140 __str__ = __len__
141 - def unpack(self, buf):
142 raise NotImplementedError
143
144 - class RR(Q):
145 """DNS resource record.""" 146 __hdr__ = ( 147 ('name', '1025s', ''), 148 ('type', 'H', DNS_A), 149 ('cls', 'H', DNS_IN), 150 ('ttl', 'I', 0), 151 ('rlen', 'H', 4), 152 ('rdata', 's', '') 153 )
154 - def pack_rdata(self, off, label_ptrs):
155 # XXX - yeah, this sux 156 if self.rdata: 157 return self.rdata 158 if self.type == DNS_A: 159 return self.ip 160 elif self.type == DNS_NS: 161 return pack_name(self.nsname, off, label_ptrs) 162 elif self.type == DNS_CNAME: 163 return pack_name(self.cname, off, label_ptrs) 164 elif self.type == DNS_PTR: 165 return pack_name(self.ptrname, off, label_ptrs) 166 elif self.type == DNS_SOA: 167 l = [] 168 l.append(pack_name(self.mname, off, label_ptrs)) 169 l.append(pack_name(self.rname, off + len(l[0]), label_ptrs)) 170 l.append(struct.pack('>IIIII', self.serial, self.refresh, 171 self.retry, self.expire, self.minimum)) 172 return ''.join(l) 173 elif self.type == DNS_MX: 174 return struct.pack('>H', self.preference) + \ 175 pack_name(self.mxname, off + 2, label_ptrs) 176 elif self.type == DNS_TXT or self.type == DNS_HINFO: 177 return ''.join([ '%s%s' % (chr(len(x)), x) 178 for x in self.text ]) 179 elif self.type == DNS_AAAA: 180 return self.ip6 181 elif self.type == DNS_SRV: 182 return struct.pack('>HHH', self.priority, self.weight, self.port) + \ 183 pack_name(self.srvname, off + 6, label_ptrs)
184
185 - def unpack_rdata(self, buf, off):
186 if self.type == DNS_A: 187 self.ip = self.rdata 188 elif self.type == DNS_NS: 189 self.nsname, off = unpack_name(buf, off) 190 elif self.type == DNS_CNAME: 191 self.cname, off = unpack_name(buf, off) 192 elif self.type == DNS_PTR: 193 self.ptrname, off = unpack_name(buf, off) 194 elif self.type == DNS_SOA: 195 self.mname, off = unpack_name(buf, off) 196 self.rname, off = unpack_name(buf, off) 197 self.serial, self.refresh, self.retry, self.expire, \ 198 self.minimum = struct.unpack('>IIIII', buf[off:off+20]) 199 elif self.type == DNS_MX: 200 self.preference = struct.unpack('>H', self.rdata[:2]) 201 self.mxname, off = unpack_name(buf, off+2) 202 elif self.type == DNS_TXT or self.type == DNS_HINFO: 203 self.text = [] 204 buf = self.rdata 205 while buf: 206 n = ord(buf[0]) 207 self.text.append(buf[1:1+n]) 208 buf = buf[1+n:] 209 elif self.type == DNS_AAAA: 210 self.ip6 = self.rdata 211 elif self.type == DNS_SRV: 212 self.priority, self.weight, self.port = \ 213 struct.unpack('>HHH', self.rdata[:6]) 214 self.srvname, off = unpack_name(buf, off+6)
215
216 - def pack_q(self, buf, q):
217 """Append packed DNS question and return buf.""" 218 return buf + pack_name(q.name, len(buf), self.label_ptrs) + \ 219 struct.pack('>HH', q.type, q.cls)
220
221 - def unpack_q(self, buf, off):
222 """Return DNS question and new offset.""" 223 q = self.Q() 224 q.name, off = unpack_name(buf, off) 225 q.type, q.cls = struct.unpack('>HH', buf[off:off+4]) 226 off += 4 227 return q, off
228
229 - def pack_rr(self, buf, rr):
230 """Append packed DNS RR and return buf.""" 231 name = pack_name(rr.name, len(buf), self.label_ptrs) 232 rdata = rr.pack_rdata(len(buf) + len(name) + 10, self.label_ptrs) 233 return buf + name + struct.pack('>HHIH', rr.type, rr.cls, rr.ttl, 234 len(rdata)) + rdata
235
236 - def unpack_rr(self, buf, off):
237 """Return DNS RR and new offset.""" 238 rr = self.RR() 239 rr.name, off = unpack_name(buf, off) 240 rr.type, rr.cls, rr.ttl, rdlen = struct.unpack('>HHIH', buf[off:off+10]) 241 off += 10 242 rr.rdata = buf[off:off+rdlen] 243 rr.unpack_rdata(buf, off) 244 off += rdlen 245 return rr, off
246
247 - def unpack(self, buf):
248 dpkt.Packet.unpack(self, buf) 249 off = self.__hdr_len__ 250 cnt = self.qd 251 self.qd = [] 252 for i in range(cnt): 253 q, off = self.unpack_q(buf, off) 254 self.qd.append(q) 255 for x in ('an', 'ns', 'ar'): 256 cnt = getattr(self, x, 0) 257 setattr(self, x, []) 258 for i in range(cnt): 259 rr, off = self.unpack_rr(buf, off) 260 getattr(self, x).append(rr) 261 self.data = ''
262
263 - def __len__(self):
264 # XXX - cop out 265 return len(str(self))
266
267 - def __str__(self):
268 # XXX - compress names on the fly 269 self.label_ptrs = {} 270 buf = struct.pack(self.__hdr_fmt__, self.id, self.op, len(self.qd), 271 len(self.an), len(self.ns), len(self.ar)) 272 for q in self.qd: 273 buf = self.pack_q(buf, q) 274 for x in ('an', 'ns', 'ar'): 275 for rr in getattr(self, x): 276 buf = self.pack_rr(buf, rr) 277 del self.label_ptrs 278 return buf
279 280 if __name__ == '__main__': 281 import unittest 282 from ip import IP 283
284 - class DNSTestCase(unittest.TestCase):
285 - def test_basic(self):
286 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' 287 ip = IP(s) 288 dns = DNS(ip.udp.data) 289 self.failUnless(dns.qd[0].name == 'www.google.com' and 290 dns.an[1].name == 'www.google.akadns.net') 291 s = '\x05\xf5\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x03www\x03cnn\x03com\x00\x00\x01\x00\x01' 292 dns = DNS(s) 293 self.failUnless(s == str(dns))
294
295 - def test_PTR(self):
296 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' 297 dns = DNS(s) 298 self.failUnless(dns.qd[0].name == '1.1.211.141.in-addr.arpa' and 299 dns.an[0].ptrname == 'default.v-umce-ifs.umnet.umich.edu' and 300 dns.ns[0].nsname == 'shabby.ifs.umich.edu' and 301 dns.ns[1].ttl == 3382L and 302 dns.ns[2].nsname == 'dns2.itd.umich.edu') 303 self.failUnless(s == str(dns))
304 305 unittest.main() 306