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- # Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
- # Copyright (C) 2001-2017 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"""
- from __future__ import absolute_import
- from io import StringIO
- import struct
- 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
- from ._compat import long, xrange, string_types
- class ShortHeader(dns.exception.FormError):
- """The DNS packet passed to from_wire() is too short."""
- class TrailingJunk(dns.exception.FormError):
- """The DNS packet passed to from_wire() has extra junk at the end of it."""
- class UnknownHeaderField(dns.exception.DNSException):
- """The header field name was not recognized when converting from text
- into a message."""
- class BadEDNS(dns.exception.FormError):
- """An OPT record occurred somewhere other than the start of
- the additional data section."""
- class BadTSIG(dns.exception.FormError):
- """A TSIG record occurred somewhere other than the end of
- the additional data section."""
- class UnknownTSIGKey(dns.exception.DNSException):
- """A TSIG with an unknown key was received."""
- #: The question section number
- QUESTION = 0
- #: The answer section number
- ANSWER = 1
- #: The authority section number
- AUTHORITY = 2
- #: The additional section number
- ADDITIONAL = 3
- class Message(object):
- """A DNS message."""
- 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 ' + repr(self.id) + '>'
- def __str__(self):
- return self.to_text()
- def to_text(self, origin=None, relativize=True, **kw):
- """Convert the message to text.
- The *origin*, *relativize*, and any other keyword
- arguments are passed to the RRset ``to_wire()`` method.
- Returns a ``text``.
- """
- s = StringIO()
- s.write(u'id %d\n' % self.id)
- s.write(u'opcode %s\n' %
- dns.opcode.to_text(dns.opcode.from_flags(self.flags)))
- rc = dns.rcode.from_flags(self.flags, self.ednsflags)
- s.write(u'rcode %s\n' % dns.rcode.to_text(rc))
- s.write(u'flags %s\n' % dns.flags.to_text(self.flags))
- if self.edns >= 0:
- s.write(u'edns %s\n' % self.edns)
- if self.ednsflags != 0:
- s.write(u'eflags %s\n' %
- dns.flags.edns_to_text(self.ednsflags))
- s.write(u'payload %d\n' % self.payload)
- for opt in self.options:
- s.write(u'option %s\n' % opt.to_text())
- is_update = dns.opcode.is_update(self.flags)
- if is_update:
- s.write(u';ZONE\n')
- else:
- s.write(u';QUESTION\n')
- for rrset in self.question:
- s.write(rrset.to_text(origin, relativize, **kw))
- s.write(u'\n')
- if is_update:
- s.write(u';PREREQ\n')
- else:
- s.write(u';ANSWER\n')
- for rrset in self.answer:
- s.write(rrset.to_text(origin, relativize, **kw))
- s.write(u'\n')
- if is_update:
- s.write(u';UPDATE\n')
- else:
- s.write(u';AUTHORITY\n')
- for rrset in self.authority:
- s.write(rrset.to_text(origin, relativize, **kw))
- s.write(u'\n')
- s.write(u';ADDITIONAL\n')
- for rrset in self.additional:
- s.write(rrset.to_text(origin, relativize, **kw))
- s.write(u'\n')
- #
- # 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.
- Returns a ``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):
- return not self.__eq__(other)
- def is_response(self, other):
- """Is this message a response to *other*?
- Returns a ``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):
- """Return the "section number" of the specified section for use
- in indexing. The question section is 0, the answer section is 1,
- the authority section is 2, and the additional section is 3.
- *section* is one of the section attributes of this message.
- Raises ``ValueError`` if the section isn't known.
- Returns an ``int``.
- """
- if section is self.question:
- return QUESTION
- elif section is self.answer:
- return ANSWER
- elif section is self.authority:
- return AUTHORITY
- elif section is self.additional:
- return ADDITIONAL
- else:
- raise ValueError('unknown section')
- def section_from_number(self, number):
- """Return the "section number" of the specified section for use
- in indexing. The question section is 0, the answer section is 1,
- the authority section is 2, and the additional section is 3.
- *section* is one of the section attributes of this message.
- Raises ``ValueError`` if the section isn't known.
- Returns an ``int``.
- """
- if number == QUESTION:
- return self.question
- elif number == ANSWER:
- return self.answer
- elif number == AUTHORITY:
- return self.authority
- elif number == ADDITIONAL:
- return self.additional
- 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.
- *section*, an ``int`` section number, or one of the section
- attributes of this message. This specifies the
- the section of the message to search. For example::
- my_message.find_rrset(my_message.answer, name, rdclass, rdtype)
- my_message.find_rrset(dns.message.ANSWER, name, rdclass, rdtype)
- *name*, a ``dns.name.Name``, the name of the RRset.
- *rdclass*, an ``int``, the class of the RRset.
- *rdtype*, an ``int``, the type of the RRset.
- *covers*, an ``int`` or ``None``, the covers value of the RRset.
- The default is ``None``.
- *deleting*, an ``int`` or ``None``, the deleting value of the RRset.
- The default is ``None``.
- *create*, a ``bool``. If ``True``, create the RRset if it is not found.
- The created RRset is appended to *section*.
- *force_unique*, a ``bool``. If ``True`` and *create* is also ``True``,
- create a new RRset regardless of whether a matching RRset exists
- already. The default is ``False``. This is useful when creating
- DDNS Update messages, as order matters for them.
- Raises ``KeyError`` if the RRset was not found and create was
- ``False``.
- Returns a ``dns.rrset.RRset object``.
- """
- if isinstance(section, int):
- section_number = section
- section = self.section_from_number(section_number)
- else:
- section_number = self.section_number(section)
- key = (section_number, name, rdclass, rdtype, covers, deleting)
- if not force_unique:
- if self.index is not None:
- rrset = self.index.get(key)
- if rrset is not 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 self.index is not 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.
- *section*, an ``int`` section number, or one of the section
- attributes of this message. This specifies the
- the section of the message to search. For example::
- my_message.get_rrset(my_message.answer, name, rdclass, rdtype)
- my_message.get_rrset(dns.message.ANSWER, name, rdclass, rdtype)
- *name*, a ``dns.name.Name``, the name of the RRset.
- *rdclass*, an ``int``, the class of the RRset.
- *rdtype*, an ``int``, the type of the RRset.
- *covers*, an ``int`` or ``None``, the covers value of the RRset.
- The default is ``None``.
- *deleting*, an ``int`` or ``None``, the deleting value of the RRset.
- The default is ``None``.
- *create*, a ``bool``. If ``True``, create the RRset if it is not found.
- The created RRset is appended to *section*.
- *force_unique*, a ``bool``. If ``True`` and *create* is also ``True``,
- create a new RRset regardless of whether a matching RRset exists
- already. The default is ``False``. This is useful when creating
- DDNS Update messages, as order matters for them.
- Returns a ``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.
- *origin*, a ``dns.name.Name`` or ``None``, the origin to be appended
- to any relative names.
- *max_size*, an ``int``, the maximum size of the wire format
- output; default is 0, which means "the message's request
- payload, if nonzero, or 65535".
- Raises ``dns.exception.TooBig`` if *max_size* was exceeded.
- Returns a ``binary``.
- """
- 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 self.keyname is not 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.
- See the documentation of the Message class for a complete
- description of the keyring dictionary.
- *keyring*, a ``dict``, the TSIG keyring to use. 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.
- *keyname*, a ``dns.name.Name`` or ``None``, the name of the TSIG key
- to use; defaults to ``None``. The key must be defined in the keyring.
- *fudge*, an ``int``, the TSIG time fudge.
- *original_id*, an ``int``, the TSIG original id. If ``None``,
- the message's id is used.
- *tsig_error*, an ``int``, the TSIG error code.
- *other_data*, a ``binary``, the TSIG other data.
- *algorithm*, a ``dns.name.Name``, the TSIG algorithm to use.
- """
- self.keyring = keyring
- if keyname is None:
- self.keyname = list(self.keyring.keys())[0]
- else:
- if isinstance(keyname, string_types):
- 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.
- *edns*, an ``int``, is 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".
- *ednsflags*, an ``int``, the EDNS flag values.
- *payload*, an ``int``, is the EDNS sender's payload field, which is the
- maximum size of UDP datagram the sender can handle. I.e. how big
- a response to this message can be.
- *request_payload*, an ``int``, is the EDNS payload size to use when
- sending this message. If not specified, defaults to the value of
- *payload*.
- *options*, a list of ``dns.edns.Option`` objects or ``None``, the EDNS
- options.
- """
- 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 &= long(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.
- *wanted*, a ``bool``. If ``True``, then DNSSEC data is
- desired in the response, EDNS is enabled if required, and then
- the DO bit is set. If ``False``, the DO bit is cleared if
- EDNS is enabled.
- """
- 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.
- Returns an ``int``.
- """
- return dns.rcode.from_flags(self.flags, self.ednsflags)
- def set_rcode(self, rcode):
- """Set the rcode.
- *rcode*, an ``int``, is the rcode to set.
- """
- (value, evalue) = dns.rcode.to_flags(rcode)
- self.flags &= 0xFFF0
- self.flags |= value
- self.ednsflags &= long(0x00FFFFFF)
- self.ednsflags |= evalue
- if self.ednsflags != 0 and self.edns < 0:
- self.edns = 0
- def opcode(self):
- """Return the opcode.
- Returns an ``int``.
- """
- return dns.opcode.from_flags(self.flags)
- def set_opcode(self, opcode):
- """Set the opcode.
- *opcode*, an ``int``, is the opcode to set.
- """
- self.flags &= 0x87FF
- self.flags |= dns.opcode.to_flags(opcode)
- class _WireReader(object):
- """Wire format reader.
- wire: a binary, is the wire-format message.
- message: The message object being built
- 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.
- updating: Is the message a dynamic update?
- one_rr_per_rrset: Put each RR into its own RRset?
- ignore_trailing: Ignore trailing junk at end of request?
- zone_rdclass: The class of the zone in messages which are
- DNS dynamic updates.
- """
- 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 *qcount* records from the wire data and add them to
- the question section.
- """
- if self.updating and qcount > 1:
- raise dns.exception.FormError
- for i in xrange(0, qcount):
- (qname, used) = dns.name.from_wire(self.wire, self.current)
- if self.message.origin is not 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.
- section: the section of the message to which to add records
- count: the number of records to read
- """
- if self.updating or self.one_rr_per_rrset:
- force_unique = True
- else:
- force_unique = False
- seen_opt = False
- for i in xrange(0, count):
- rr_start = self.current
- (name, used) = dns.name.from_wire(self.wire, self.current)
- absolute_name = name
- if self.message.origin is not 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 section is not 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.keyname = absolute_name
- (self.message.keyalgorithm, self.message.mac) = \
- dns.tsig.get_algorithm_and_mac(self.wire, self.current,
- rdlen)
- 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 rd is not 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.
- *keyring*, a ``dict``, the keyring to use if the message is signed.
- *request_mac*, a ``binary``. If the message is a response to a
- TSIG-signed request, *request_mac* should be set to the MAC of
- that request.
- *xfr*, a ``bool``, should be set to ``True`` if this message is part of
- a zone transfer.
- *origin*, a ``dns.name.Name`` or ``None``. If the message is part
- of a zone transfer, *origin* should be the origin name of the
- zone.
- *tsig_ctx*, a ``hmac.HMAC`` objext, the ongoing TSIG context, used
- when validating zone transfers.
- *multi*, a ``bool``, should be set to ``True`` if this message
- part of a multiple message sequence.
- *first*, a ``bool``, should be set to ``True`` if this message is
- stand-alone, or the first message in a multi-message sequence.
- *question_only*, a ``bool``. If ``True``, read only up to
- the end of the question section.
- *one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its
- own RRset.
- *ignore_trailing*, a ``bool``. If ``True``, ignore trailing
- junk at end of the message.
- Raises ``dns.message.ShortHeader`` if the message is less than 12 octets
- long.
- Raises ``dns.messaage.TrailingJunk`` if there were octets in the message
- past the end of the proper DNS message, and *ignore_trailing* is ``False``.
- Raises ``dns.message.BadEDNS`` if an OPT record was in the
- wrong section, or occurred more than once.
- Raises ``dns.message.BadTSIG`` if a TSIG record was not the last
- record of the additional data section.
- Returns a ``dns.message.Message``.
- """
- 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.
- tok: the tokenizer.
- message: The message object being built.
- updating: Is the message a dynamic update?
- zone_rdclass: The class of the zone in messages which are
- DNS dynamic updates.
- last_name: The most recently read name when building a message 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 Exception:
- 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 Exception:
- 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 Exception:
- 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 rd is not 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.
- *text*, a ``text``, the text format message.
- Raises ``dns.message.UnknownHeaderField`` if a header is unknown.
- Raises ``dns.exception.SyntaxError`` if the text is badly formed.
- Returns a ``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.
- *f*, a ``file`` or ``text``. If *f* is text, it is treated as the
- pathname of a file to open.
- Raises ``dns.message.UnknownHeaderField`` if a header is unknown.
- Raises ``dns.exception.SyntaxError`` if the text is badly formed.
- Returns a ``dns.message.Message object``
- """
- str_type = string_types
- opts = 'rU'
- if isinstance(f, str_type):
- f = open(f, opts)
- 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=None, payload=None,
- 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 chosen query id, and its DNS flags
- will be set to dns.flags.RD.
- qname, a ``dns.name.Name`` or ``text``, the query name.
- *rdtype*, an ``int`` or ``text``, the desired rdata type.
- *rdclass*, an ``int`` or ``text``, the desired rdata class; the default
- is class IN.
- *use_edns*, an ``int``, ``bool`` or ``None``. 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.
- *want_dnssec*, a ``bool``. If ``True``, DNSSEC data is desired.
- *ednsflags*, an ``int``, the EDNS flag values.
- *payload*, an ``int``, is the EDNS sender's payload field, which is the
- maximum size of UDP datagram the sender can handle. I.e. how big
- a response to this message can be.
- *request_payload*, an ``int``, is the EDNS payload size to use when
- sending this message. If not specified, defaults to the value of
- *payload*.
- *options*, a list of ``dns.edns.Option`` objects or ``None``, the EDNS
- options.
- Returns a ``dns.message.Message``
- """
- if isinstance(qname, string_types):
- qname = dns.name.from_text(qname)
- if isinstance(rdtype, string_types):
- rdtype = dns.rdatatype.from_text(rdtype)
- if isinstance(rdclass, string_types):
- 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)
- # only pass keywords on to use_edns if they have been set to a
- # non-None value. Setting a field will turn EDNS on if it hasn't
- # been configured.
- kwargs = {}
- if ednsflags is not None:
- kwargs['ednsflags'] = ednsflags
- if use_edns is None:
- use_edns = 0
- if payload is not None:
- kwargs['payload'] = payload
- if use_edns is None:
- use_edns = 0
- if request_payload is not None:
- kwargs['request_payload'] = request_payload
- if use_edns is None:
- use_edns = 0
- if options is not None:
- kwargs['options'] = options
- if use_edns is None:
- use_edns = 0
- kwargs['edns'] = use_edns
- m.use_edns(**kwargs)
- m.want_dnssec(want_dnssec)
- return m
- def make_response(query, recursion_available=False, our_payload=8192,
- fudge=300):
- """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.
- *query*, a ``dns.message.Message``, the query to respond to.
- *recursion_available*, a ``bool``, should RA be set in the response?
- *our_payload*, an ``int``, the payload size to advertise in EDNS
- responses.
- *fudge*, an ``int``, the TSIG time fudge.
- Returns a ``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 query.had_tsig:
- response.use_tsig(query.keyring, query.keyname, fudge, None, 0, b'',
- query.keyalgorithm)
- response.request_mac = query.mac
- return response
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