/usr/lib/python3/dist-packages/dns/message.py is in python3-dnspython 1.11.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 | # Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
"""DNS Messages"""
import io
import random
import struct
import sys
import time
import dns.edns
import dns.exception
import dns.flags
import dns.name
import dns.opcode
import dns.entropy
import dns.rcode
import dns.rdata
import dns.rdataclass
import dns.rdatatype
import dns.rrset
import dns.renderer
import dns.tsig
import dns.wiredata
class ShortHeader(dns.exception.FormError):
"""Raised if the DNS packet passed to from_wire() is too short."""
pass
class TrailingJunk(dns.exception.FormError):
"""Raised if the DNS packet passed to from_wire() has extra junk
at the end of it."""
pass
class UnknownHeaderField(dns.exception.DNSException):
"""Raised if a header field name is not recognized when converting from
text into a message."""
pass
class BadEDNS(dns.exception.FormError):
"""Raised if an OPT record occurs somewhere other than the start of
the additional data section."""
pass
class BadTSIG(dns.exception.FormError):
"""Raised if a TSIG record occurs somewhere other than the end of
the additional data section."""
pass
class UnknownTSIGKey(dns.exception.DNSException):
"""Raised if we got a TSIG but don't know the key."""
pass
class Message(object):
"""A DNS message.
@ivar id: The query id; the default is a randomly chosen id.
@type id: int
@ivar flags: The DNS flags of the message. @see: RFC 1035 for an
explanation of these flags.
@type flags: int
@ivar question: The question section.
@type question: list of dns.rrset.RRset objects
@ivar answer: The answer section.
@type answer: list of dns.rrset.RRset objects
@ivar authority: The authority section.
@type authority: list of dns.rrset.RRset objects
@ivar additional: The additional data section.
@type additional: list of dns.rrset.RRset objects
@ivar edns: The EDNS level to use. The default is -1, no Edns.
@type edns: int
@ivar ednsflags: The EDNS flags
@type ednsflags: long
@ivar payload: The EDNS payload size. The default is 0.
@type payload: int
@ivar options: The EDNS options
@type options: list of dns.edns.Option objects
@ivar request_payload: The associated request's EDNS payload size.
@type request_payload: int
@ivar keyring: The TSIG keyring to use. The default is None.
@type keyring: dict
@ivar keyname: The TSIG keyname to use. The default is None.
@type keyname: dns.name.Name object
@ivar keyalgorithm: The TSIG algorithm to use; defaults to
dns.tsig.default_algorithm. Constants for TSIG algorithms are defined
in dns.tsig, and the currently implemented algorithms are
HMAC_MD5, HMAC_SHA1, HMAC_SHA224, HMAC_SHA256, HMAC_SHA384, and
HMAC_SHA512.
@type keyalgorithm: string
@ivar request_mac: The TSIG MAC of the request message associated with
this message; used when validating TSIG signatures. @see: RFC 2845 for
more information on TSIG fields.
@type request_mac: string
@ivar fudge: TSIG time fudge; default is 300 seconds.
@type fudge: int
@ivar original_id: TSIG original id; defaults to the message's id
@type original_id: int
@ivar tsig_error: TSIG error code; default is 0.
@type tsig_error: int
@ivar other_data: TSIG other data.
@type other_data: bytes
@ivar mac: The TSIG MAC for this message.
@type mac: bytes
@ivar xfr: Is the message being used to contain the results of a DNS
zone transfer? The default is False.
@type xfr: bool
@ivar origin: The origin of the zone in messages which are used for
zone transfers or for DNS dynamic updates. The default is None.
@type origin: dns.name.Name object
@ivar tsig_ctx: The TSIG signature context associated with this
message. The default is None.
@type tsig_ctx: hmac.HMAC object
@ivar had_tsig: Did the message decoded from wire format have a TSIG
signature?
@type had_tsig: bool
@ivar multi: Is this message part of a multi-message sequence? The
default is false. This variable is used when validating TSIG signatures
on messages which are part of a zone transfer.
@type multi: bool
@ivar first: Is this message standalone, or the first of a multi
message sequence? This variable is used when validating TSIG signatures
on messages which are part of a zone transfer.
@type first: bool
@ivar index: An index of rrsets in the message. The index key is
(section, name, rdclass, rdtype, covers, deleting). Indexing can be
disabled by setting the index to None.
@type index: dict
"""
def __init__(self, id=None):
if id is None:
self.id = dns.entropy.random_16()
else:
self.id = id
self.flags = 0
self.question = []
self.answer = []
self.authority = []
self.additional = []
self.edns = -1
self.ednsflags = 0
self.payload = 0
self.options = []
self.request_payload = 0
self.keyring = None
self.keyname = None
self.keyalgorithm = dns.tsig.default_algorithm
self.request_mac = b''
self.other_data = b''
self.tsig_error = 0
self.fudge = 300
self.original_id = self.id
self.mac = b''
self.xfr = False
self.origin = None
self.tsig_ctx = None
self.had_tsig = False
self.multi = False
self.first = True
self.index = {}
def __repr__(self):
return '<DNS message, ID ' + str(self.id) + '>'
def __str__(self):
return self.to_text()
def to_text(self, origin=None, relativize=True, **kw):
"""Convert the message to text.
The I{origin}, I{relativize}, and any other keyword
arguments are passed to the rrset to_wire() method.
@rtype: string
"""
s = io.StringIO()
print('id %d' % self.id, file=s)
print('opcode %s' % \
dns.opcode.to_text(dns.opcode.from_flags(self.flags)),
file=s)
rc = dns.rcode.from_flags(self.flags, self.ednsflags)
print('rcode %s' % dns.rcode.to_text(rc), file=s)
print('flags %s' % dns.flags.to_text(self.flags), file=s)
if self.edns >= 0:
print('edns %s' % self.edns, file=s)
if self.ednsflags != 0:
print('eflags %s' % \
dns.flags.edns_to_text(self.ednsflags), file=s)
print('payload', self.payload, file=s)
is_update = dns.opcode.is_update(self.flags)
if is_update:
print(';ZONE', file=s)
else:
print(';QUESTION', file=s)
for rrset in self.question:
print(rrset.to_text(origin, relativize, **kw), file=s)
if is_update:
print(';PREREQ', file=s)
else:
print(';ANSWER', file=s)
for rrset in self.answer:
print(rrset.to_text(origin, relativize, **kw), file=s)
if is_update:
print(';UPDATE', file=s)
else:
print(';AUTHORITY', file=s)
for rrset in self.authority:
print(rrset.to_text(origin, relativize, **kw), file=s)
print(';ADDITIONAL', file=s)
for rrset in self.additional:
print(rrset.to_text(origin, relativize, **kw), file=s)
#
# We strip off the final \n so the caller can print the result without
# doing weird things to get around eccentricities in Python print
# formatting
#
return s.getvalue()[:-1]
def __eq__(self, other):
"""Two messages are equal if they have the same content in the
header, question, answer, and authority sections.
@rtype: bool"""
if not isinstance(other, Message):
return False
if self.id != other.id:
return False
if self.flags != other.flags:
return False
for n in self.question:
if n not in other.question:
return False
for n in other.question:
if n not in self.question:
return False
for n in self.answer:
if n not in other.answer:
return False
for n in other.answer:
if n not in self.answer:
return False
for n in self.authority:
if n not in other.authority:
return False
for n in other.authority:
if n not in self.authority:
return False
return True
def __ne__(self, other):
"""Are two messages not equal?
@rtype: bool"""
return not self.__eq__(other)
def is_response(self, other):
"""Is other a response to self?
@rtype: bool"""
if other.flags & dns.flags.QR == 0 or \
self.id != other.id or \
dns.opcode.from_flags(self.flags) != \
dns.opcode.from_flags(other.flags):
return False
if dns.rcode.from_flags(other.flags, other.ednsflags) != \
dns.rcode.NOERROR:
return True
if dns.opcode.is_update(self.flags):
return True
for n in self.question:
if n not in other.question:
return False
for n in other.question:
if n not in self.question:
return False
return True
def section_number(self, section):
if section is self.question:
return 0
elif section is self.answer:
return 1
elif section is self.authority:
return 2
elif section is self.additional:
return 3
else:
raise ValueError('unknown section')
def find_rrset(self, section, name, rdclass, rdtype,
covers=dns.rdatatype.NONE, deleting=None, create=False,
force_unique=False):
"""Find the RRset with the given attributes in the specified section.
@param section: the section of the message to look in, e.g.
self.answer.
@type section: list of dns.rrset.RRset objects
@param name: the name of the RRset
@type name: dns.name.Name object
@param rdclass: the class of the RRset
@type rdclass: int
@param rdtype: the type of the RRset
@type rdtype: int
@param covers: the covers value of the RRset
@type covers: int
@param deleting: the deleting value of the RRset
@type deleting: int
@param create: If True, create the RRset if it is not found.
The created RRset is appended to I{section}.
@type create: bool
@param force_unique: If True and create is also True, create a
new RRset regardless of whether a matching RRset exists already.
@type force_unique: bool
@raises KeyError: the RRset was not found and create was False
@rtype: dns.rrset.RRset object"""
key = (self.section_number(section),
name, rdclass, rdtype, covers, deleting)
if not force_unique:
if not self.index is None:
rrset = self.index.get(key)
if not rrset is None:
return rrset
else:
for rrset in section:
if rrset.match(name, rdclass, rdtype, covers, deleting):
return rrset
if not create:
raise KeyError
rrset = dns.rrset.RRset(name, rdclass, rdtype, covers, deleting)
section.append(rrset)
if not self.index is None:
self.index[key] = rrset
return rrset
def get_rrset(self, section, name, rdclass, rdtype,
covers=dns.rdatatype.NONE, deleting=None, create=False,
force_unique=False):
"""Get the RRset with the given attributes in the specified section.
If the RRset is not found, None is returned.
@param section: the section of the message to look in, e.g.
self.answer.
@type section: list of dns.rrset.RRset objects
@param name: the name of the RRset
@type name: dns.name.Name object
@param rdclass: the class of the RRset
@type rdclass: int
@param rdtype: the type of the RRset
@type rdtype: int
@param covers: the covers value of the RRset
@type covers: int
@param deleting: the deleting value of the RRset
@type deleting: int
@param create: If True, create the RRset if it is not found.
The created RRset is appended to I{section}.
@type create: bool
@param force_unique: If True and create is also True, create a
new RRset regardless of whether a matching RRset exists already.
@type force_unique: bool
@rtype: dns.rrset.RRset object or None"""
try:
rrset = self.find_rrset(section, name, rdclass, rdtype, covers,
deleting, create, force_unique)
except KeyError:
rrset = None
return rrset
def to_wire(self, origin=None, max_size=0, **kw):
"""Return a string containing the message in DNS compressed wire
format.
Additional keyword arguments are passed to the rrset to_wire()
method.
@param origin: The origin to be appended to any relative names.
@type origin: dns.name.Name object
@param max_size: The maximum size of the wire format output; default
is 0, which means 'the message's request payload, if nonzero, or
65536'.
@type max_size: int
@raises dns.exception.TooBig: max_size was exceeded
@rtype: string
"""
if max_size == 0:
if self.request_payload != 0:
max_size = self.request_payload
else:
max_size = 65535
if max_size < 512:
max_size = 512
elif max_size > 65535:
max_size = 65535
r = dns.renderer.Renderer(self.id, self.flags, max_size, origin)
for rrset in self.question:
r.add_question(rrset.name, rrset.rdtype, rrset.rdclass)
for rrset in self.answer:
r.add_rrset(dns.renderer.ANSWER, rrset, **kw)
for rrset in self.authority:
r.add_rrset(dns.renderer.AUTHORITY, rrset, **kw)
if self.edns >= 0:
r.add_edns(self.edns, self.ednsflags, self.payload, self.options)
for rrset in self.additional:
r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw)
r.write_header()
if not self.keyname is None:
r.add_tsig(self.keyname, self.keyring[self.keyname],
self.fudge, self.original_id, self.tsig_error,
self.other_data, self.request_mac,
self.keyalgorithm)
self.mac = r.mac
return r.get_wire()
def use_tsig(self, keyring, keyname=None, fudge=300,
original_id=None, tsig_error=0, other_data=b'',
algorithm=dns.tsig.default_algorithm):
"""When sending, a TSIG signature using the specified keyring
and keyname should be added.
@param keyring: The TSIG keyring to use; defaults to None.
@type keyring: dict
@param keyname: The name of the TSIG key to use; defaults to None.
The key must be defined in the keyring. If a keyring is specified
but a keyname is not, then the key used will be the first key in the
keyring. Note that the order of keys in a dictionary is not defined,
so applications should supply a keyname when a keyring is used, unless
they know the keyring contains only one key.
@type keyname: dns.name.Name or string
@param fudge: TSIG time fudge; default is 300 seconds.
@type fudge: int
@param original_id: TSIG original id; defaults to the message's id
@type original_id: int
@param tsig_error: TSIG error code; default is 0.
@type tsig_error: int
@param other_data: TSIG other data.
@type other_data: bytes
@param algorithm: The TSIG algorithm to use; defaults to
dns.tsig.default_algorithm
"""
self.keyring = keyring
if keyname is None:
self.keyname = next(iter(self.keyring.keys()))
else:
if isinstance(keyname, str):
keyname = dns.name.from_text(keyname)
self.keyname = keyname
self.keyalgorithm = algorithm
self.fudge = fudge
if original_id is None:
self.original_id = self.id
else:
self.original_id = original_id
self.tsig_error = tsig_error
self.other_data = other_data
def use_edns(self, edns=0, ednsflags=0, payload=1280, request_payload=None, options=None):
"""Configure EDNS behavior.
@param edns: The EDNS level to use. Specifying None, False, or -1
means 'do not use EDNS', and in this case the other parameters are
ignored. Specifying True is equivalent to specifying 0, i.e. 'use
EDNS0'.
@type edns: int or bool or None
@param ednsflags: EDNS flag values.
@type ednsflags: int
@param payload: The EDNS sender's payload field, which is the maximum
size of UDP datagram the sender can handle.
@type payload: int
@param request_payload: The EDNS payload size to use when sending
this message. If not specified, defaults to the value of payload.
@type request_payload: int or None
@param options: The EDNS options
@type options: None or list of dns.edns.Option objects
@see: RFC 2671
"""
if edns is None or edns is False:
edns = -1
if edns is True:
edns = 0
if request_payload is None:
request_payload = payload
if edns < 0:
ednsflags = 0
payload = 0
request_payload = 0
options = []
else:
# make sure the EDNS version in ednsflags agrees with edns
ednsflags &= 0xFF00FFFF
ednsflags |= (edns << 16)
if options is None:
options = []
self.edns = edns
self.ednsflags = ednsflags
self.payload = payload
self.options = options
self.request_payload = request_payload
def want_dnssec(self, wanted=True):
"""Enable or disable 'DNSSEC desired' flag in requests.
@param wanted: Is DNSSEC desired? If True, EDNS is enabled if
required, and then the DO bit is set. If False, the DO bit is
cleared if EDNS is enabled.
@type wanted: bool
"""
if wanted:
if self.edns < 0:
self.use_edns()
self.ednsflags |= dns.flags.DO
elif self.edns >= 0:
self.ednsflags &= ~dns.flags.DO
def rcode(self):
"""Return the rcode.
@rtype: int
"""
return dns.rcode.from_flags(self.flags, self.ednsflags)
def set_rcode(self, rcode):
"""Set the rcode.
@param rcode: the rcode
@type rcode: int
"""
(value, evalue) = dns.rcode.to_flags(rcode)
self.flags &= 0xFFF0
self.flags |= value
self.ednsflags &= 0x00FFFFFF
self.ednsflags |= evalue
if self.ednsflags != 0 and self.edns < 0:
self.edns = 0
def opcode(self):
"""Return the opcode.
@rtype: int
"""
return dns.opcode.from_flags(self.flags)
def set_opcode(self, opcode):
"""Set the opcode.
@param opcode: the opcode
@type opcode: int
"""
self.flags &= 0x87FF
self.flags |= dns.opcode.to_flags(opcode)
class _WireReader(object):
"""Wire format reader.
@ivar wire: the wire-format message.
@type wire: string
@ivar message: The message object being built
@type message: dns.message.Message object
@ivar current: When building a message object from wire format, this
variable contains the offset from the beginning of wire of the next octet
to be read.
@type current: int
@ivar updating: Is the message a dynamic update?
@type updating: bool
@ivar one_rr_per_rrset: Put each RR into its own RRset?
@type one_rr_per_rrset: bool
@ivar ignore_trailing: Ignore trailing junk at end of request?
@type ignore_trailing: bool
@ivar zone_rdclass: The class of the zone in messages which are
DNS dynamic updates.
@type zone_rdclass: int
"""
def __init__(self, wire, message, question_only=False,
one_rr_per_rrset=False, ignore_trailing=False):
self.wire = dns.wiredata.maybe_wrap(wire)
self.message = message
self.current = 0
self.updating = False
self.zone_rdclass = dns.rdataclass.IN
self.question_only = question_only
self.one_rr_per_rrset = one_rr_per_rrset
self.ignore_trailing = ignore_trailing
def _get_question(self, qcount):
"""Read the next I{qcount} records from the wire data and add them to
the question section.
@param qcount: the number of questions in the message
@type qcount: int"""
if self.updating and qcount > 1:
raise dns.exception.FormError
for i in range(0, qcount):
(qname, used) = dns.name.from_wire(self.wire, self.current)
if not self.message.origin is None:
qname = qname.relativize(self.message.origin)
self.current = self.current + used
(rdtype, rdclass) = \
struct.unpack('!HH',
self.wire[self.current:self.current + 4])
self.current = self.current + 4
self.message.find_rrset(self.message.question, qname,
rdclass, rdtype, create=True,
force_unique=True)
if self.updating:
self.zone_rdclass = rdclass
def _get_section(self, section, count):
"""Read the next I{count} records from the wire data and add them to
the specified section.
@param section: the section of the message to which to add records
@type section: list of dns.rrset.RRset objects
@param count: the number of records to read
@type count: int"""
if self.updating or self.one_rr_per_rrset:
force_unique = True
else:
force_unique = False
seen_opt = False
for i in range(0, count):
rr_start = self.current
(name, used) = dns.name.from_wire(self.wire, self.current)
absolute_name = name
if not self.message.origin is None:
name = name.relativize(self.message.origin)
self.current = self.current + used
(rdtype, rdclass, ttl, rdlen) = \
struct.unpack('!HHIH',
self.wire[self.current:self.current + 10])
self.current = self.current + 10
if rdtype == dns.rdatatype.OPT:
if not section is self.message.additional or seen_opt:
raise BadEDNS
self.message.payload = rdclass
self.message.ednsflags = ttl
self.message.edns = (ttl & 0xff0000) >> 16
self.message.options = []
current = self.current
optslen = rdlen
while optslen > 0:
(otype, olen) = \
struct.unpack('!HH',
self.wire[current:current + 4])
current = current + 4
opt = dns.edns.option_from_wire(otype, self.wire, current, olen)
self.message.options.append(opt)
current = current + olen
optslen = optslen - 4 - olen
seen_opt = True
elif rdtype == dns.rdatatype.TSIG:
if not (section is self.message.additional and
i == (count - 1)):
raise BadTSIG
if self.message.keyring is None:
raise UnknownTSIGKey('got signed message without keyring')
secret = self.message.keyring.get(absolute_name)
if secret is None:
raise UnknownTSIGKey("key '%s' unknown" % name)
self.message.tsig_ctx = \
dns.tsig.validate(self.wire,
absolute_name,
secret,
int(time.time()),
self.message.request_mac,
rr_start,
self.current,
rdlen,
self.message.tsig_ctx,
self.message.multi,
self.message.first)
self.message.had_tsig = True
else:
if ttl < 0:
ttl = 0
if self.updating and \
(rdclass == dns.rdataclass.ANY or
rdclass == dns.rdataclass.NONE):
deleting = rdclass
rdclass = self.zone_rdclass
else:
deleting = None
if deleting == dns.rdataclass.ANY or \
(deleting == dns.rdataclass.NONE and \
section is self.message.answer):
covers = dns.rdatatype.NONE
rd = None
else:
rd = dns.rdata.from_wire(rdclass, rdtype, self.wire,
self.current, rdlen,
self.message.origin)
covers = rd.covers()
if self.message.xfr and rdtype == dns.rdatatype.SOA:
force_unique = True
rrset = self.message.find_rrset(section, name,
rdclass, rdtype, covers,
deleting, True, force_unique)
if not rd is None:
rrset.add(rd, ttl)
self.current = self.current + rdlen
def read(self):
"""Read a wire format DNS message and build a dns.message.Message
object."""
l = len(self.wire)
if l < 12:
raise ShortHeader
(self.message.id, self.message.flags, qcount, ancount,
aucount, adcount) = struct.unpack('!HHHHHH', self.wire[:12])
self.current = 12
if dns.opcode.is_update(self.message.flags):
self.updating = True
self._get_question(qcount)
if self.question_only:
return
self._get_section(self.message.answer, ancount)
self._get_section(self.message.authority, aucount)
self._get_section(self.message.additional, adcount)
if not self.ignore_trailing and self.current != l:
raise TrailingJunk
if self.message.multi and self.message.tsig_ctx and \
not self.message.had_tsig:
self.message.tsig_ctx.update(self.wire)
def from_wire(wire, keyring=None, request_mac=b'', xfr=False, origin=None,
tsig_ctx = None, multi = False, first = True,
question_only = False, one_rr_per_rrset = False,
ignore_trailing = False):
"""Convert a DNS wire format message into a message
object.
@param keyring: The keyring to use if the message is signed.
@type keyring: dict
@param request_mac: If the message is a response to a TSIG-signed request,
I{request_mac} should be set to the MAC of that request.
@type request_mac: bytes
@param xfr: Is this message part of a zone transfer?
@type xfr: bool
@param origin: If the message is part of a zone transfer, I{origin}
should be the origin name of the zone.
@type origin: dns.name.Name object
@param tsig_ctx: The ongoing TSIG context, used when validating zone
transfers.
@type tsig_ctx: hmac.HMAC object
@param multi: Is this message part of a multiple message sequence?
@type multi: bool
@param first: Is this message standalone, or the first of a multi
message sequence?
@type first: bool
@param question_only: Read only up to the end of the question section?
@type question_only: bool
@param one_rr_per_rrset: Put each RR into its own RRset
@type one_rr_per_rrset: bool
@param ignore_trailing: Ignore trailing junk at end of request?
@type ignore_trailing: bool
@raises ShortHeader: The message is less than 12 octets long.
@raises TrailingJunk: There were octets in the message past the end
of the proper DNS message.
@raises BadEDNS: An OPT record was in the wrong section, or occurred more
than once.
@raises BadTSIG: A TSIG record was not the last record of the additional
data section.
@rtype: dns.message.Message object"""
m = Message(id=0)
m.keyring = keyring
m.request_mac = request_mac
m.xfr = xfr
m.origin = origin
m.tsig_ctx = tsig_ctx
m.multi = multi
m.first = first
reader = _WireReader(wire, m, question_only, one_rr_per_rrset,
ignore_trailing)
reader.read()
return m
class _TextReader(object):
"""Text format reader.
@ivar tok: the tokenizer
@type tok: dns.tokenizer.Tokenizer object
@ivar message: The message object being built
@type message: dns.message.Message object
@ivar updating: Is the message a dynamic update?
@type updating: bool
@ivar zone_rdclass: The class of the zone in messages which are
DNS dynamic updates.
@type zone_rdclass: int
@ivar last_name: The most recently read name when building a message object
from text format.
@type last_name: dns.name.Name object
"""
def __init__(self, text, message):
self.message = message
self.tok = dns.tokenizer.Tokenizer(text)
self.last_name = None
self.zone_rdclass = dns.rdataclass.IN
self.updating = False
def _header_line(self, section):
"""Process one line from the text format header section."""
token = self.tok.get()
what = token.value
if what == 'id':
self.message.id = self.tok.get_int()
elif what == 'flags':
while True:
token = self.tok.get()
if not token.is_identifier():
self.tok.unget(token)
break
self.message.flags = self.message.flags | \
dns.flags.from_text(token.value)
if dns.opcode.is_update(self.message.flags):
self.updating = True
elif what == 'edns':
self.message.edns = self.tok.get_int()
self.message.ednsflags = self.message.ednsflags | \
(self.message.edns << 16)
elif what == 'eflags':
if self.message.edns < 0:
self.message.edns = 0
while True:
token = self.tok.get()
if not token.is_identifier():
self.tok.unget(token)
break
self.message.ednsflags = self.message.ednsflags | \
dns.flags.edns_from_text(token.value)
elif what == 'payload':
self.message.payload = self.tok.get_int()
if self.message.edns < 0:
self.message.edns = 0
elif what == 'opcode':
text = self.tok.get_string()
self.message.flags = self.message.flags | \
dns.opcode.to_flags(dns.opcode.from_text(text))
elif what == 'rcode':
text = self.tok.get_string()
self.message.set_rcode(dns.rcode.from_text(text))
else:
raise UnknownHeaderField
self.tok.get_eol()
def _question_line(self, section):
"""Process one line from the text format question section."""
token = self.tok.get(want_leading = True)
if not token.is_whitespace():
self.last_name = dns.name.from_text(token.value, None)
name = self.last_name
token = self.tok.get()
if not token.is_identifier():
raise dns.exception.SyntaxError
# Class
try:
rdclass = dns.rdataclass.from_text(token.value)
token = self.tok.get()
if not token.is_identifier():
raise dns.exception.SyntaxError
except dns.exception.SyntaxError:
raise dns.exception.SyntaxError
except:
rdclass = dns.rdataclass.IN
# Type
rdtype = dns.rdatatype.from_text(token.value)
self.message.find_rrset(self.message.question, name,
rdclass, rdtype, create=True,
force_unique=True)
if self.updating:
self.zone_rdclass = rdclass
self.tok.get_eol()
def _rr_line(self, section):
"""Process one line from the text format answer, authority, or
additional data sections.
"""
deleting = None
# Name
token = self.tok.get(want_leading = True)
if not token.is_whitespace():
self.last_name = dns.name.from_text(token.value, None)
name = self.last_name
token = self.tok.get()
if not token.is_identifier():
raise dns.exception.SyntaxError
# TTL
try:
ttl = int(token.value, 0)
token = self.tok.get()
if not token.is_identifier():
raise dns.exception.SyntaxError
except dns.exception.SyntaxError:
raise dns.exception.SyntaxError
except:
ttl = 0
# Class
try:
rdclass = dns.rdataclass.from_text(token.value)
token = self.tok.get()
if not token.is_identifier():
raise dns.exception.SyntaxError
if rdclass == dns.rdataclass.ANY or rdclass == dns.rdataclass.NONE:
deleting = rdclass
rdclass = self.zone_rdclass
except dns.exception.SyntaxError:
raise dns.exception.SyntaxError
except:
rdclass = dns.rdataclass.IN
# Type
rdtype = dns.rdatatype.from_text(token.value)
token = self.tok.get()
if not token.is_eol_or_eof():
self.tok.unget(token)
rd = dns.rdata.from_text(rdclass, rdtype, self.tok, None)
covers = rd.covers()
else:
rd = None
covers = dns.rdatatype.NONE
rrset = self.message.find_rrset(section, name,
rdclass, rdtype, covers,
deleting, True, self.updating)
if not rd is None:
rrset.add(rd, ttl)
def read(self):
"""Read a text format DNS message and build a dns.message.Message
object."""
line_method = self._header_line
section = None
while 1:
token = self.tok.get(True, True)
if token.is_eol_or_eof():
break
if token.is_comment():
u = token.value.upper()
if u == 'HEADER':
line_method = self._header_line
elif u == 'QUESTION' or u == 'ZONE':
line_method = self._question_line
section = self.message.question
elif u == 'ANSWER' or u == 'PREREQ':
line_method = self._rr_line
section = self.message.answer
elif u == 'AUTHORITY' or u == 'UPDATE':
line_method = self._rr_line
section = self.message.authority
elif u == 'ADDITIONAL':
line_method = self._rr_line
section = self.message.additional
self.tok.get_eol()
continue
self.tok.unget(token)
line_method(section)
def from_text(text):
"""Convert the text format message into a message object.
@param text: The text format message.
@type text: string
@raises UnknownHeaderField:
@raises dns.exception.SyntaxError:
@rtype: dns.message.Message object"""
# 'text' can also be a file, but we don't publish that fact
# since it's an implementation detail. The official file
# interface is from_file().
m = Message()
reader = _TextReader(text, m)
reader.read()
return m
def from_file(f):
"""Read the next text format message from the specified file.
@param f: file or string. If I{f} is a string, it is treated
as the name of a file to open.
@raises UnknownHeaderField:
@raises dns.exception.SyntaxError:
@rtype: dns.message.Message object"""
if isinstance(f, str):
f = open(f, 'rU')
want_close = True
else:
want_close = False
try:
m = from_text(f)
finally:
if want_close:
f.close()
return m
def make_query(qname, rdtype, rdclass = dns.rdataclass.IN, use_edns=None,
want_dnssec=False, ednsflags=0, payload=1280,
request_payload=None, options=None):
"""Make a query message.
The query name, type, and class may all be specified either
as objects of the appropriate type, or as strings.
The query will have a randomly choosen query id, and its DNS flags
will be set to dns.flags.RD.
@param qname: The query name.
@type qname: dns.name.Name object or string
@param rdtype: The desired rdata type.
@type rdtype: int
@param rdclass: The desired rdata class; the default is class IN.
@type rdclass: int
@param use_edns: The EDNS level to use; the default is None (no EDNS).
See the description of dns.message.Message.use_edns() for the possible
values for use_edns and their meanings.
@type use_edns: int or bool or None
@param want_dnssec: Should the query indicate that DNSSEC is desired?
@type want_dnssec: bool
@param ednsflags: EDNS flag values.
@type ednsflags: int
@param payload: The EDNS sender's payload field, which is the maximum
size of UDP datagram the sender can handle.
@type payload: int
@param request_payload: The EDNS payload size to use when sending
this message. If not specified, defaults to the value of payload.
@type request_payload: int or None
@param options: The EDNS options
@type options: None or list of dns.edns.Option objects
@see: RFC 2671
@rtype: dns.message.Message object"""
if isinstance(qname, str):
qname = dns.name.from_text(qname)
if isinstance(rdtype, str):
rdtype = dns.rdatatype.from_text(rdtype)
if isinstance(rdclass, str):
rdclass = dns.rdataclass.from_text(rdclass)
m = Message()
m.flags |= dns.flags.RD
m.find_rrset(m.question, qname, rdclass, rdtype, create=True,
force_unique=True)
m.use_edns(use_edns, ednsflags, payload, request_payload, options)
m.want_dnssec(want_dnssec)
return m
def make_response(query, recursion_available=False, our_payload=8192):
"""Make a message which is a response for the specified query.
The message returned is really a response skeleton; it has all
of the infrastructure required of a response, but none of the
content.
The response's question section is a shallow copy of the query's
question section, so the query's question RRsets should not be
changed.
@param query: the query to respond to
@type query: dns.message.Message object
@param recursion_available: should RA be set in the response?
@type recursion_available: bool
@param our_payload: payload size to advertise in EDNS responses; default
is 8192.
@type our_payload: int
@rtype: dns.message.Message object"""
if query.flags & dns.flags.QR:
raise dns.exception.FormError('specified query message is not a query')
response = dns.message.Message(query.id)
response.flags = dns.flags.QR | (query.flags & dns.flags.RD)
if recursion_available:
response.flags |= dns.flags.RA
response.set_opcode(query.opcode())
response.question = list(query.question)
if query.edns >= 0:
response.use_edns(0, 0, our_payload, query.payload)
if not query.keyname is None:
response.keyname = query.keyname
response.keyring = query.keyring
response.request_mac = query.mac
return response
|