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

   1  # Copyright (C) 2001-2007, 2009 Nominum, Inc. 
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   5  # provided that the above copyright notice and this permission notice 
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  15   
  16  """DNS Messages""" 
  17   
  18  import cStringIO 
  19  import random 
  20  import struct 
  21  import sys 
  22  import time 
  23   
  24  import dns.exception 
  25  import dns.flags 
  26  import dns.name 
  27  import dns.opcode 
  28  import dns.entropy 
  29  import dns.rcode 
  30  import dns.rdata 
  31  import dns.rdataclass 
  32  import dns.rdatatype 
  33  import dns.rrset 
  34  import dns.renderer 
  35  import dns.tsig 
  36   
37 -class ShortHeader(dns.exception.FormError):
38 """Raised if the DNS packet passed to from_wire() is too short.""" 39 pass
40
41 -class TrailingJunk(dns.exception.FormError):
42 """Raised if the DNS packet passed to from_wire() has extra junk 43 at the end of it.""" 44 pass
45
46 -class UnknownHeaderField(dns.exception.DNSException):
47 """Raised if a header field name is not recognized when converting from 48 text into a message.""" 49 pass
50
51 -class BadEDNS(dns.exception.FormError):
52 """Raised if an OPT record occurs somewhere other than the start of 53 the additional data section.""" 54 pass
55
56 -class BadTSIG(dns.exception.FormError):
57 """Raised if a TSIG record occurs somewhere other than the end of 58 the additional data section.""" 59 pass
60
61 -class UnknownTSIGKey(dns.exception.DNSException):
62 """Raised if we got a TSIG but don't know the key.""" 63 pass
64
65 -class Message(object):
66 """A DNS message. 67 68 @ivar id: The query id; the default is a randomly chosen id. 69 @type id: int 70 @ivar flags: The DNS flags of the message. @see: RFC 1035 for an 71 explanation of these flags. 72 @type flags: int 73 @ivar question: The question section. 74 @type question: list of dns.rrset.RRset objects 75 @ivar answer: The answer section. 76 @type answer: list of dns.rrset.RRset objects 77 @ivar authority: The authority section. 78 @type authority: list of dns.rrset.RRset objects 79 @ivar additional: The additional data section. 80 @type additional: list of dns.rrset.RRset objects 81 @ivar edns: The EDNS level to use. The default is -1, no Edns. 82 @type edns: int 83 @ivar ednsflags: The EDNS flags 84 @type ednsflags: long 85 @ivar payload: The EDNS payload size. The default is 0. 86 @type payload: int 87 @ivar options: The EDNS options 88 @type options: list of dns.edns.Option objects 89 @ivar request_payload: The associated request's EDNS payload size. 90 @type request_payload: int 91 @ivar keyring: The TSIG keyring to use. The default is None. 92 @type keyring: dict 93 @ivar keyname: The TSIG keyname to use. The default is None. 94 @type keyname: dns.name.Name object 95 @ivar request_mac: The TSIG MAC of the request message associated with 96 this message; used when validating TSIG signatures. @see: RFC 2845 for 97 more information on TSIG fields. 98 @type request_mac: string 99 @ivar fudge: TSIG time fudge; default is 300 seconds. 100 @type fudge: int 101 @ivar original_id: TSIG original id; defaults to the message's id 102 @type original_id: int 103 @ivar tsig_error: TSIG error code; default is 0. 104 @type tsig_error: int 105 @ivar other_data: TSIG other data. 106 @type other_data: string 107 @ivar mac: The TSIG MAC for this message. 108 @type mac: string 109 @ivar xfr: Is the message being used to contain the results of a DNS 110 zone transfer? The default is False. 111 @type xfr: bool 112 @ivar origin: The origin of the zone in messages which are used for 113 zone transfers or for DNS dynamic updates. The default is None. 114 @type origin: dns.name.Name object 115 @ivar tsig_ctx: The TSIG signature context associated with this 116 message. The default is None. 117 @type tsig_ctx: hmac.HMAC object 118 @ivar had_tsig: Did the message decoded from wire format have a TSIG 119 signature? 120 @type had_tsig: bool 121 @ivar multi: Is this message part of a multi-message sequence? The 122 default is false. This variable is used when validating TSIG signatures 123 on messages which are part of a zone transfer. 124 @type multi: bool 125 @ivar first: Is this message standalone, or the first of a multi 126 message sequence? This variable is used when validating TSIG signatures 127 on messages which are part of a zone transfer. 128 @type first: bool 129 @ivar index: An index of rrsets in the message. The index key is 130 (section, name, rdclass, rdtype, covers, deleting). Indexing can be 131 disabled by setting the index to None. 132 @type index: dict 133 """ 134
135 - def __init__(self, id=None):
136 if id is None: 137 self.id = dns.entropy.random_16() 138 else: 139 self.id = id 140 self.flags = 0 141 self.question = [] 142 self.answer = [] 143 self.authority = [] 144 self.additional = [] 145 self.edns = -1 146 self.ednsflags = 0 147 self.payload = 0 148 self.options = [] 149 self.request_payload = 0 150 self.keyring = None 151 self.keyname = None 152 self.request_mac = '' 153 self.other_data = '' 154 self.tsig_error = 0 155 self.fudge = 300 156 self.original_id = self.id 157 self.mac = '' 158 self.xfr = False 159 self.origin = None 160 self.tsig_ctx = None 161 self.had_tsig = False 162 self.multi = False 163 self.first = True 164 self.index = {}
165
166 - def __repr__(self):
167 return '<DNS message, ID ' + `self.id` + '>'
168
169 - def __str__(self):
170 return self.to_text()
171
172 - def to_text(self, origin=None, relativize=True, **kw):
173 """Convert the message to text. 174 175 The I{origin}, I{relativize}, and any other keyword 176 arguments are passed to the rrset to_wire() method. 177 178 @rtype: string 179 """ 180 181 s = cStringIO.StringIO() 182 print >> s, 'id %d' % self.id 183 print >> s, 'opcode %s' % \ 184 dns.opcode.to_text(dns.opcode.from_flags(self.flags)) 185 rc = dns.rcode.from_flags(self.flags, self.ednsflags) 186 print >> s, 'rcode %s' % dns.rcode.to_text(rc) 187 print >> s, 'flags %s' % dns.flags.to_text(self.flags) 188 if self.edns >= 0: 189 print >> s, 'edns %s' % self.edns 190 if self.ednsflags != 0: 191 print >> s, 'eflags %s' % \ 192 dns.flags.edns_to_text(self.ednsflags) 193 print >> s, 'payload', self.payload 194 is_update = dns.opcode.is_update(self.flags) 195 if is_update: 196 print >> s, ';ZONE' 197 else: 198 print >> s, ';QUESTION' 199 for rrset in self.question: 200 print >> s, rrset.to_text(origin, relativize, **kw) 201 if is_update: 202 print >> s, ';PREREQ' 203 else: 204 print >> s, ';ANSWER' 205 for rrset in self.answer: 206 print >> s, rrset.to_text(origin, relativize, **kw) 207 if is_update: 208 print >> s, ';UPDATE' 209 else: 210 print >> s, ';AUTHORITY' 211 for rrset in self.authority: 212 print >> s, rrset.to_text(origin, relativize, **kw) 213 print >> s, ';ADDITIONAL' 214 for rrset in self.additional: 215 print >> s, rrset.to_text(origin, relativize, **kw) 216 # 217 # We strip off the final \n so the caller can print the result without 218 # doing weird things to get around eccentricities in Python print 219 # formatting 220 # 221 return s.getvalue()[:-1]
222
223 - def __eq__(self, other):
224 """Two messages are equal if they have the same content in the 225 header, question, answer, and authority sections. 226 @rtype: bool""" 227 if not isinstance(other, Message): 228 return False 229 if self.id != other.id: 230 return False 231 if self.flags != other.flags: 232 return False 233 for n in self.question: 234 if n not in other.question: 235 return False 236 for n in other.question: 237 if n not in self.question: 238 return False 239 for n in self.answer: 240 if n not in other.answer: 241 return False 242 for n in other.answer: 243 if n not in self.answer: 244 return False 245 for n in self.authority: 246 if n not in other.authority: 247 return False 248 for n in other.authority: 249 if n not in self.authority: 250 return False 251 return True
252
253 - def __ne__(self, other):
254 """Are two messages not equal? 255 @rtype: bool""" 256 return not self.__eq__(other)
257
258 - def is_response(self, other):
259 """Is other a response to self? 260 @rtype: bool""" 261 if other.flags & dns.flags.QR == 0 or \ 262 self.id != other.id or \ 263 dns.opcode.from_flags(self.flags) != \ 264 dns.opcode.from_flags(other.flags): 265 return False 266 if dns.rcode.from_flags(other.flags, other.ednsflags) != \ 267 dns.rcode.NOERROR: 268 return True 269 if dns.opcode.is_update(self.flags): 270 return True 271 for n in self.question: 272 if n not in other.question: 273 return False 274 for n in other.question: 275 if n not in self.question: 276 return False 277 return True
278
279 - def section_number(self, section):
280 if section is self.question: 281 return 0 282 elif section is self.answer: 283 return 1 284 elif section is self.authority: 285 return 2 286 elif section is self.additional: 287 return 3 288 else: 289 raise ValueError, 'unknown section'
290
291 - def find_rrset(self, section, name, rdclass, rdtype, 292 covers=dns.rdatatype.NONE, deleting=None, create=False, 293 force_unique=False):
294 """Find the RRset with the given attributes in the specified section. 295 296 @param section: the section of the message to look in, e.g. 297 self.answer. 298 @type section: list of dns.rrset.RRset objects 299 @param name: the name of the RRset 300 @type name: dns.name.Name object 301 @param rdclass: the class of the RRset 302 @type rdclass: int 303 @param rdtype: the type of the RRset 304 @type rdtype: int 305 @param covers: the covers value of the RRset 306 @type covers: int 307 @param deleting: the deleting value of the RRset 308 @type deleting: int 309 @param create: If True, create the RRset if it is not found. 310 The created RRset is appended to I{section}. 311 @type create: bool 312 @param force_unique: If True and create is also True, create a 313 new RRset regardless of whether a matching RRset exists already. 314 @type force_unique: bool 315 @raises KeyError: the RRset was not found and create was False 316 @rtype: dns.rrset.RRset object""" 317 318 key = (self.section_number(section), 319 name, rdclass, rdtype, covers, deleting) 320 if not force_unique: 321 if not self.index is None: 322 rrset = self.index.get(key) 323 if not rrset is None: 324 return rrset 325 else: 326 for rrset in section: 327 if rrset.match(name, rdclass, rdtype, covers, deleting): 328 return rrset 329 if not create: 330 raise KeyError 331 rrset = dns.rrset.RRset(name, rdclass, rdtype, covers, deleting) 332 section.append(rrset) 333 if not self.index is None: 334 self.index[key] = rrset 335 return rrset
336
337 - def get_rrset(self, section, name, rdclass, rdtype, 338 covers=dns.rdatatype.NONE, deleting=None, create=False, 339 force_unique=False):
340 """Get the RRset with the given attributes in the specified section. 341 342 If the RRset is not found, None is returned. 343 344 @param section: the section of the message to look in, e.g. 345 self.answer. 346 @type section: list of dns.rrset.RRset objects 347 @param name: the name of the RRset 348 @type name: dns.name.Name object 349 @param rdclass: the class of the RRset 350 @type rdclass: int 351 @param rdtype: the type of the RRset 352 @type rdtype: int 353 @param covers: the covers value of the RRset 354 @type covers: int 355 @param deleting: the deleting value of the RRset 356 @type deleting: int 357 @param create: If True, create the RRset if it is not found. 358 The created RRset is appended to I{section}. 359 @type create: bool 360 @param force_unique: If True and create is also True, create a 361 new RRset regardless of whether a matching RRset exists already. 362 @type force_unique: bool 363 @rtype: dns.rrset.RRset object or None""" 364 365 try: 366 rrset = self.find_rrset(section, name, rdclass, rdtype, covers, 367 deleting, create, force_unique) 368 except KeyError: 369 rrset = None 370 return rrset
371
372 - def to_wire(self, origin=None, max_size=0, **kw):
373 """Return a string containing the message in DNS compressed wire 374 format. 375 376 Additional keyword arguments are passed to the rrset to_wire() 377 method. 378 379 @param origin: The origin to be appended to any relative names. 380 @type origin: dns.name.Name object 381 @param max_size: The maximum size of the wire format output; default 382 is 0, which means 'the message's request payload, if nonzero, or 383 65536'. 384 @type max_size: int 385 @raises dns.exception.TooBig: max_size was exceeded 386 @rtype: string 387 """ 388 389 if max_size == 0: 390 if self.request_payload != 0: 391 max_size = self.request_payload 392 else: 393 max_size = 65535 394 if max_size < 512: 395 max_size = 512 396 elif max_size > 65535: 397 max_size = 65535 398 r = dns.renderer.Renderer(self.id, self.flags, max_size, origin) 399 for rrset in self.question: 400 r.add_question(rrset.name, rrset.rdtype, rrset.rdclass) 401 for rrset in self.answer: 402 r.add_rrset(dns.renderer.ANSWER, rrset, **kw) 403 for rrset in self.authority: 404 r.add_rrset(dns.renderer.AUTHORITY, rrset, **kw) 405 if self.edns >= 0: 406 r.add_edns(self.edns, self.ednsflags, self.payload, self.options) 407 for rrset in self.additional: 408 r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw) 409 r.write_header() 410 if not self.keyname is None: 411 r.add_tsig(self.keyname, self.keyring[self.keyname], 412 self.fudge, self.original_id, self.tsig_error, 413 self.other_data, self.request_mac) 414 self.mac = r.mac 415 return r.get_wire()
416
417 - def use_tsig(self, keyring, keyname=None, fudge=300, original_id=None, 418 tsig_error=0, other_data=''):
419 """When sending, a TSIG signature using the specified keyring 420 and keyname should be added. 421 422 @param keyring: The TSIG keyring to use; defaults to None. 423 @type keyring: dict 424 @param keyname: The name of the TSIG key to use; defaults to None. 425 The key must be defined in the keyring. If a keyring is specified 426 but a keyname is not, then the key used will be the first key in the 427 keyring. Note that the order of keys in a dictionary is not defined, 428 so applications should supply a keyname when a keyring is used, unless 429 they know the keyring contains only one key. 430 @type keyname: dns.name.Name or string 431 @param fudge: TSIG time fudge; default is 300 seconds. 432 @type fudge: int 433 @param original_id: TSIG original id; defaults to the message's id 434 @type original_id: int 435 @param tsig_error: TSIG error code; default is 0. 436 @type tsig_error: int 437 @param other_data: TSIG other data. 438 @type other_data: string 439 """ 440 441 self.keyring = keyring 442 if keyname is None: 443 self.keyname = self.keyring.keys()[0] 444 else: 445 if isinstance(keyname, (str, unicode)): 446 keyname = dns.name.from_text(keyname) 447 self.keyname = keyname 448 self.fudge = fudge 449 if original_id is None: 450 self.original_id = self.id 451 else: 452 self.original_id = original_id 453 self.tsig_error = tsig_error 454 self.other_data = other_data
455
456 - def use_edns(self, edns=0, ednsflags=0, payload=1280, request_payload=None, options=None):
457 """Configure EDNS behavior. 458 @param edns: The EDNS level to use. Specifying None, False, or -1 459 means 'do not use EDNS', and in this case the other parameters are 460 ignored. Specifying True is equivalent to specifying 0, i.e. 'use 461 EDNS0'. 462 @type edns: int or bool or None 463 @param ednsflags: EDNS flag values. 464 @type ednsflags: int 465 @param payload: The EDNS sender's payload field, which is the maximum 466 size of UDP datagram the sender can handle. 467 @type payload: int 468 @param request_payload: The EDNS payload size to use when sending 469 this message. If not specified, defaults to the value of payload. 470 @type request_payload: int or None 471 @param options: The EDNS options 472 @type options: None or list of dns.edns.Option objects 473 @see: RFC 2671 474 """ 475 if edns is None or edns is False: 476 edns = -1 477 if edns is True: 478 edns = 0 479 if request_payload is None: 480 request_payload = payload 481 if edns < 0: 482 ednsflags = 0 483 payload = 0 484 request_payload = 0 485 options = [] 486 else: 487 # make sure the EDNS version in ednsflags agrees with edns 488 ednsflags &= 0xFF00FFFFL 489 ednsflags |= (edns << 16) 490 if options is None: 491 options = [] 492 self.edns = edns 493 self.ednsflags = ednsflags 494 self.payload = payload 495 self.options = options 496 self.request_payload = request_payload
497
498 - def want_dnssec(self, wanted=True):
499 """Enable or disable 'DNSSEC desired' flag in requests. 500 @param wanted: Is DNSSEC desired? If True, EDNS is enabled if 501 required, and then the DO bit is set. If False, the DO bit is 502 cleared if EDNS is enabled. 503 @type wanted: bool 504 """ 505 if wanted: 506 if self.edns < 0: 507 self.use_edns() 508 self.ednsflags |= dns.flags.DO 509 elif self.edns >= 0: 510 self.ednsflags &= ~dns.flags.DO
511
512 - def rcode(self):
513 """Return the rcode. 514 @rtype: int 515 """ 516 return dns.rcode.from_flags(self.flags, self.ednsflags)
517
518 - def set_rcode(self, rcode):
519 """Set the rcode. 520 @param rcode: the rcode 521 @type rcode: int 522 """ 523 (value, evalue) = dns.rcode.to_flags(rcode) 524 self.flags &= 0xFFF0 525 self.flags |= value 526 self.ednsflags &= 0x00FFFFFFL 527 self.ednsflags |= evalue 528 if self.ednsflags != 0 and self.edns < 0: 529 self.edns = 0
530
531 - def opcode(self):
532 """Return the opcode. 533 @rtype: int 534 """ 535 return dns.opcode.from_flags(self.flags)
536
537 - def set_opcode(self, opcode):
538 """Set the opcode. 539 @param opcode: the opcode 540 @type opcode: int 541 """ 542 self.flags &= 0x87FF 543 self.flags |= dns.opcode.to_flags(opcode)
544
545 -class _WireReader(object):
546 """Wire format reader. 547 548 @ivar wire: the wire-format message. 549 @type wire: string 550 @ivar message: The message object being built 551 @type message: dns.message.Message object 552 @ivar current: When building a message object from wire format, this 553 variable contains the offset from the beginning of wire of the next octet 554 to be read. 555 @type current: int 556 @ivar updating: Is the message a dynamic update? 557 @type updating: bool 558 @ivar one_rr_per_rrset: Put each RR into its own RRset? 559 @type one_rr_per_rrset: bool 560 @ivar zone_rdclass: The class of the zone in messages which are 561 DNS dynamic updates. 562 @type zone_rdclass: int 563 """ 564
565 - def __init__(self, wire, message, question_only=False, 566 one_rr_per_rrset=False):
567 self.wire = wire 568 self.message = message 569 self.current = 0 570 self.updating = False 571 self.zone_rdclass = dns.rdataclass.IN 572 self.question_only = question_only 573 self.one_rr_per_rrset = one_rr_per_rrset
574
575 - def _get_question(self, qcount):
576 """Read the next I{qcount} records from the wire data and add them to 577 the question section. 578 @param qcount: the number of questions in the message 579 @type qcount: int""" 580 581 if self.updating and qcount > 1: 582 raise dns.exception.FormError 583 584 for i in xrange(0, qcount): 585 (qname, used) = dns.name.from_wire(self.wire, self.current) 586 if not self.message.origin is None: 587 qname = qname.relativize(self.message.origin) 588 self.current = self.current + used 589 (rdtype, rdclass) = \ 590 struct.unpack('!HH', 591 self.wire[self.current:self.current + 4]) 592 self.current = self.current + 4 593 self.message.find_rrset(self.message.question, qname, 594 rdclass, rdtype, create=True, 595 force_unique=True) 596 if self.updating: 597 self.zone_rdclass = rdclass
598
599 - def _get_section(self, section, count):
600 """Read the next I{count} records from the wire data and add them to 601 the specified section. 602 @param section: the section of the message to which to add records 603 @type section: list of dns.rrset.RRset objects 604 @param count: the number of records to read 605 @type count: int""" 606 607 if self.updating or self.one_rr_per_rrset: 608 force_unique = True 609 else: 610 force_unique = False 611 seen_opt = False 612 for i in xrange(0, count): 613 rr_start = self.current 614 (name, used) = dns.name.from_wire(self.wire, self.current) 615 absolute_name = name 616 if not self.message.origin is None: 617 name = name.relativize(self.message.origin) 618 self.current = self.current + used 619 (rdtype, rdclass, ttl, rdlen) = \ 620 struct.unpack('!HHIH', 621 self.wire[self.current:self.current + 10]) 622 self.current = self.current + 10 623 if rdtype == dns.rdatatype.OPT: 624 if not section is self.message.additional or seen_opt: 625 raise BadEDNS 626 self.message.payload = rdclass 627 self.message.ednsflags = ttl 628 self.message.edns = (ttl & 0xff0000) >> 16 629 self.message.options = [] 630 current = self.current 631 optslen = rdlen 632 while optslen > 0: 633 (otype, olen) = \ 634 struct.unpack('!HH', 635 self.wire[current:current + 4]) 636 current = current + 4 637 opt = dns.edns.option_from_wire(otype, self.wire, current, olen) 638 self.message.options.append(opt) 639 current = current + olen 640 optslen = optslen - 4 - olen 641 seen_opt = True 642 elif rdtype == dns.rdatatype.TSIG: 643 if not (section is self.message.additional and 644 i == (count - 1)): 645 raise BadTSIG 646 if self.message.keyring is None: 647 raise UnknownTSIGKey, 'got signed message without keyring' 648 secret = self.message.keyring.get(absolute_name) 649 if secret is None: 650 raise UnknownTSIGKey, "key '%s' unknown" % name 651 self.message.tsig_ctx = \ 652 dns.tsig.validate(self.wire, 653 absolute_name, 654 secret, 655 int(time.time()), 656 self.message.request_mac, 657 rr_start, 658 self.current, 659 rdlen, 660 self.message.tsig_ctx, 661 self.message.multi, 662 self.message.first) 663 self.message.had_tsig = True 664 else: 665 if ttl < 0: 666 ttl = 0 667 if self.updating and \ 668 (rdclass == dns.rdataclass.ANY or 669 rdclass == dns.rdataclass.NONE): 670 deleting = rdclass 671 rdclass = self.zone_rdclass 672 else: 673 deleting = None 674 if deleting == dns.rdataclass.ANY: 675 covers = dns.rdatatype.NONE 676 rd = None 677 else: 678 rd = dns.rdata.from_wire(rdclass, rdtype, self.wire, 679 self.current, rdlen, 680 self.message.origin) 681 covers = rd.covers() 682 if self.message.xfr and rdtype == dns.rdatatype.SOA: 683 force_unique = True 684 rrset = self.message.find_rrset(section, name, 685 rdclass, rdtype, covers, 686 deleting, True, force_unique) 687 if not rd is None: 688 rrset.add(rd, ttl) 689 self.current = self.current + rdlen
690
691 - def read(self):
692 """Read a wire format DNS message and build a dns.message.Message 693 object.""" 694 695 l = len(self.wire) 696 if l < 12: 697 raise ShortHeader 698 (self.message.id, self.message.flags, qcount, ancount, 699 aucount, adcount) = struct.unpack('!HHHHHH', self.wire[:12]) 700 self.current = 12 701 if dns.opcode.is_update(self.message.flags): 702 self.updating = True 703 self._get_question(qcount) 704 if self.question_only: 705 return 706 self._get_section(self.message.answer, ancount) 707 self._get_section(self.message.authority, aucount) 708 self._get_section(self.message.additional, adcount) 709 if self.current != l: 710 raise TrailingJunk 711 if self.message.multi and self.message.tsig_ctx and \ 712 not self.message.had_tsig: 713 self.message.tsig_ctx.update(self.wire)
714 715
716 -def from_wire(wire, keyring=None, request_mac='', xfr=False, origin=None, 717 tsig_ctx = None, multi = False, first = True, 718 question_only = False, one_rr_per_rrset = False):
719 """Convert a DNS wire format message into a message 720 object. 721 722 @param keyring: The keyring to use if the message is signed. 723 @type keyring: dict 724 @param request_mac: If the message is a response to a TSIG-signed request, 725 I{request_mac} should be set to the MAC of that request. 726 @type request_mac: string 727 @param xfr: Is this message part of a zone transfer? 728 @type xfr: bool 729 @param origin: If the message is part of a zone transfer, I{origin} 730 should be the origin name of the zone. 731 @type origin: dns.name.Name object 732 @param tsig_ctx: The ongoing TSIG context, used when validating zone 733 transfers. 734 @type tsig_ctx: hmac.HMAC object 735 @param multi: Is this message part of a multiple message sequence? 736 @type multi: bool 737 @param first: Is this message standalone, or the first of a multi 738 message sequence? 739 @type first: bool 740 @param question_only: Read only up to the end of the question section? 741 @type question_only: bool 742 @param one_rr_per_rrset: Put each RR into its own RRset 743 @type one_rr_per_rrset: bool 744 @raises ShortHeader: The message is less than 12 octets long. 745 @raises TrailingJunk: There were octets in the message past the end 746 of the proper DNS message. 747 @raises BadEDNS: An OPT record was in the wrong section, or occurred more 748 than once. 749 @raises BadTSIG: A TSIG record was not the last record of the additional 750 data section. 751 @rtype: dns.message.Message object""" 752 753 m = Message(id=0) 754 m.keyring = keyring 755 m.request_mac = request_mac 756 m.xfr = xfr 757 m.origin = origin 758 m.tsig_ctx = tsig_ctx 759 m.multi = multi 760 m.first = first 761 762 reader = _WireReader(wire, m, question_only, one_rr_per_rrset) 763 reader.read() 764 765 return m
766 767
768 -class _TextReader(object):
769 """Text format reader. 770 771 @ivar tok: the tokenizer 772 @type tok: dns.tokenizer.Tokenizer object 773 @ivar message: The message object being built 774 @type message: dns.message.Message object 775 @ivar updating: Is the message a dynamic update? 776 @type updating: bool 777 @ivar zone_rdclass: The class of the zone in messages which are 778 DNS dynamic updates. 779 @type zone_rdclass: int 780 @ivar last_name: The most recently read name when building a message object 781 from text format. 782 @type last_name: dns.name.Name object 783 """ 784
785 - def __init__(self, text, message):
786 self.message = message 787 self.tok = dns.tokenizer.Tokenizer(text) 788 self.last_name = None 789 self.zone_rdclass = dns.rdataclass.IN 790 self.updating = False
791
792 - def _header_line(self, section):
793 """Process one line from the text format header section.""" 794 795 (ttype, what) = self.tok.get() 796 if what == 'id': 797 self.message.id = self.tok.get_int() 798 elif what == 'flags': 799 while True: 800 token = self.tok.get() 801 if token[0] != dns.tokenizer.IDENTIFIER: 802 self.tok.unget(token) 803 break 804 self.message.flags = self.message.flags | \ 805 dns.flags.from_text(token[1]) 806 if dns.opcode.is_update(self.message.flags): 807 self.updating = True 808 elif what == 'edns': 809 self.message.edns = self.tok.get_int() 810 self.message.ednsflags = self.message.ednsflags | \ 811 (self.message.edns << 16) 812 elif what == 'eflags': 813 if self.message.edns < 0: 814 self.message.edns = 0 815 while True: 816 token = self.tok.get() 817 if token[0] != dns.tokenizer.IDENTIFIER: 818 self.tok.unget(token) 819 break 820 self.message.ednsflags = self.message.ednsflags | \ 821 dns.flags.edns_from_text(token[1]) 822 elif what == 'payload': 823 self.message.payload = self.tok.get_int() 824 if self.message.edns < 0: 825 self.message.edns = 0 826 elif what == 'opcode': 827 text = self.tok.get_string() 828 self.message.flags = self.message.flags | \ 829 dns.opcode.to_flags(dns.opcode.from_text(text)) 830 elif what == 'rcode': 831 text = self.tok.get_string() 832 self.message.set_rcode(dns.rcode.from_text(text)) 833 else: 834 raise UnknownHeaderField 835 self.tok.get_eol()
836
837 - def _question_line(self, section):
838 """Process one line from the text format question section.""" 839 840 token = self.tok.get(want_leading = True) 841 if token[0] != dns.tokenizer.WHITESPACE: 842 self.last_name = dns.name.from_text(token[1], None) 843 name = self.last_name 844 token = self.tok.get() 845 if token[0] != dns.tokenizer.IDENTIFIER: 846 raise dns.exception.SyntaxError 847 # Class 848 try: 849 rdclass = dns.rdataclass.from_text(token[1]) 850 token = self.tok.get() 851 if token[0] != dns.tokenizer.IDENTIFIER: 852 raise dns.exception.SyntaxError 853 except dns.exception.SyntaxError: 854 raise dns.exception.SyntaxError 855 except: 856 rdclass = dns.rdataclass.IN 857 # Type 858 rdtype = dns.rdatatype.from_text(token[1]) 859 self.message.find_rrset(self.message.question, name, 860 rdclass, rdtype, create=True, 861 force_unique=True) 862 if self.updating: 863 self.zone_rdclass = rdclass 864 self.tok.get_eol()
865
866 - def _rr_line(self, section):
867 """Process one line from the text format answer, authority, or 868 additional data sections. 869 """ 870 871 deleting = None 872 # Name 873 token = self.tok.get(want_leading = True) 874 if token[0] != dns.tokenizer.WHITESPACE: 875 self.last_name = dns.name.from_text(token[1], None) 876 name = self.last_name 877 token = self.tok.get() 878 if token[0] != dns.tokenizer.IDENTIFIER: 879 raise dns.exception.SyntaxError 880 # TTL 881 try: 882 ttl = int(token[1], 0) 883 token = self.tok.get() 884 if token[0] != dns.tokenizer.IDENTIFIER: 885 raise dns.exception.SyntaxError 886 except dns.exception.SyntaxError: 887 raise dns.exception.SyntaxError 888 except: 889 ttl = 0 890 # Class 891 try: 892 rdclass = dns.rdataclass.from_text(token[1]) 893 token = self.tok.get() 894 if token[0] != dns.tokenizer.IDENTIFIER: 895 raise dns.exception.SyntaxError 896 if rdclass == dns.rdataclass.ANY or rdclass == dns.rdataclass.NONE: 897 deleting = rdclass 898 rdclass = self.zone_rdclass 899 except dns.exception.SyntaxError: 900 raise dns.exception.SyntaxError 901 except: 902 rdclass = dns.rdataclass.IN 903 # Type 904 rdtype = dns.rdatatype.from_text(token[1]) 905 token = self.tok.get() 906 if token[0] != dns.tokenizer.EOL and token[0] != dns.tokenizer.EOF: 907 self.tok.unget(token) 908 rd = dns.rdata.from_text(rdclass, rdtype, self.tok, None) 909 covers = rd.covers() 910 else: 911 rd = None 912 covers = dns.rdatatype.NONE 913 rrset = self.message.find_rrset(section, name, 914 rdclass, rdtype, covers, 915 deleting, True, self.updating) 916 if not rd is None: 917 rrset.add(rd, ttl)
918
919 - def read(self):
920 """Read a text format DNS message and build a dns.message.Message 921 object.""" 922 923 line_method = self._header_line 924 section = None 925 while 1: 926 token = self.tok.get(True, True) 927 if token[0] == dns.tokenizer.EOL or token[0] == dns.tokenizer.EOF: 928 break 929 if token[0] == dns.tokenizer.COMMENT: 930 u = token[1].upper() 931 if u == 'HEADER': 932 line_method = self._header_line 933 elif u == 'QUESTION' or u == 'ZONE': 934 line_method = self._question_line 935 section = self.message.question 936 elif u == 'ANSWER' or u == 'PREREQ': 937 line_method = self._rr_line 938 section = self.message.answer 939 elif u == 'AUTHORITY' or u == 'UPDATE': 940 line_method = self._rr_line 941 section = self.message.authority 942 elif u == 'ADDITIONAL': 943 line_method = self._rr_line 944 section = self.message.additional 945 self.tok.get_eol() 946 continue 947 self.tok.unget(token) 948 line_method(section)
949 950
951 -def from_text(text):
952 """Convert the text format message into a message object. 953 954 @param text: The text format message. 955 @type text: string 956 @raises UnknownHeaderField: 957 @raises dns.exception.SyntaxError: 958 @rtype: dns.message.Message object""" 959 960 # 'text' can also be a file, but we don't publish that fact 961 # since it's an implementation detail. The official file 962 # interface is from_file(). 963 964 m = Message() 965 966 reader = _TextReader(text, m) 967 reader.read() 968 969 return m
970
971 -def from_file(f):
972 """Read the next text format message from the specified file. 973 974 @param f: file or string. If I{f} is a string, it is treated 975 as the name of a file to open. 976 @raises UnknownHeaderField: 977 @raises dns.exception.SyntaxError: 978 @rtype: dns.message.Message object""" 979 980 if sys.hexversion >= 0x02030000: 981 # allow Unicode filenames; turn on universal newline support 982 str_type = basestring 983 opts = 'rU' 984 else: 985 str_type = str 986 opts = 'r' 987 if isinstance(f, str_type): 988 f = file(f, opts) 989 want_close = True 990 else: 991 want_close = False 992 993 try: 994 m = from_text(f) 995 finally: 996 if want_close: 997 f.close() 998 return m
999
1000 -def make_query(qname, rdtype, rdclass = dns.rdataclass.IN, use_edns=None, 1001 want_dnssec=False):
1002 """Make a query message. 1003 1004 The query name, type, and class may all be specified either 1005 as objects of the appropriate type, or as strings. 1006 1007 The query will have a randomly choosen query id, and its DNS flags 1008 will be set to dns.flags.RD. 1009 1010 @param qname: The query name. 1011 @type qname: dns.name.Name object or string 1012 @param rdtype: The desired rdata type. 1013 @type rdtype: int 1014 @param rdclass: The desired rdata class; the default is class IN. 1015 @type rdclass: int 1016 @param use_edns: The EDNS level to use; the default is None (no EDNS). 1017 See the description of dns.message.Message.use_edns() for the possible 1018 values for use_edns and their meanings. 1019 @type use_edns: int or bool or None 1020 @param want_dnssec: Should the query indicate that DNSSEC is desired? 1021 @type want_dnssec: bool 1022 @rtype: dns.message.Message object""" 1023 1024 if isinstance(qname, (str, unicode)): 1025 qname = dns.name.from_text(qname) 1026 if isinstance(rdtype, str): 1027 rdtype = dns.rdatatype.from_text(rdtype) 1028 if isinstance(rdclass, str): 1029 rdclass = dns.rdataclass.from_text(rdclass) 1030 m = Message() 1031 m.flags |= dns.flags.RD 1032 m.find_rrset(m.question, qname, rdclass, rdtype, create=True, 1033 force_unique=True) 1034 m.use_edns(use_edns) 1035 m.want_dnssec(want_dnssec) 1036 return m
1037
1038 -def make_response(query, recursion_available=False, our_payload=8192):
1039 """Make a message which is a response for the specified query. 1040 The message returned is really a response skeleton; it has all 1041 of the infrastructure required of a response, but none of the 1042 content. 1043 1044 The response's question section is a shallow copy of the query's 1045 question section, so the query's question RRsets should not be 1046 changed. 1047 1048 @param query: the query to respond to 1049 @type query: dns.message.Message object 1050 @param recursion_available: should RA be set in the response? 1051 @type recursion_available: bool 1052 @param our_payload: payload size to advertise in EDNS responses; default 1053 is 8192. 1054 @type our_payload: int 1055 @rtype: dns.message.Message object""" 1056 1057 if query.flags & dns.flags.QR: 1058 raise dns.exception.FormError, 'specified query message is not a query' 1059 response = dns.message.Message(query.id) 1060 response.flags = dns.flags.QR | (query.flags & dns.flags.RD) 1061 if recursion_available: 1062 response.flags |= dns.flags.RA 1063 response.set_opcode(query.opcode()) 1064 response.question = list(query.question) 1065 if query.edns >= 0: 1066 response.use_edns(0, 0, our_payload, query.payload) 1067 if not query.keyname is None: 1068 response.keyname = query.keyname 1069 response.keyring = query.keyring 1070 response.request_mac = query.mac 1071 return response
1072