Source code for dns.message

# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license

# Copyright (C) 2001-2017 Nominum, Inc.
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"""DNS Messages"""

import contextlib
import io
import time

import dns.wire
import dns.edns
import dns.enum
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.ttl
import dns.tsig
import dns.rdtypes.ANY.OPT
import dns.rdtypes.ANY.TSIG


[docs]class ShortHeader(dns.exception.FormError): """The DNS packet passed to from_wire() is too short."""
[docs]class TrailingJunk(dns.exception.FormError): """The DNS packet passed to from_wire() has extra junk at the end of it."""
[docs]class UnknownHeaderField(dns.exception.DNSException): """The header field name was not recognized when converting from text into a message."""
[docs]class BadEDNS(dns.exception.FormError): """An OPT record occurred somewhere other than the additional data section."""
[docs]class BadTSIG(dns.exception.FormError): """A TSIG record occurred somewhere other than the end of the additional data section."""
[docs]class UnknownTSIGKey(dns.exception.DNSException): """A TSIG with an unknown key was received."""
class Truncated(dns.exception.DNSException): """The truncated flag is set.""" supp_kwargs = {'message'} def message(self): """As much of the message as could be processed. Returns a ``dns.message.Message``. """ return self.kwargs['message'] class NotQueryResponse(dns.exception.DNSException): """Message is not a response to a query.""" class ChainTooLong(dns.exception.DNSException): """The CNAME chain is too long.""" class AnswerForNXDOMAIN(dns.exception.DNSException): """The rcode is NXDOMAIN but an answer was found.""" class NoPreviousName(dns.exception.SyntaxError): """No previous name was known.""" class MessageSection(dns.enum.IntEnum): """Message sections""" QUESTION = 0 ANSWER = 1 AUTHORITY = 2 ADDITIONAL = 3 @classmethod def _maximum(cls): return 3 class MessageError: def __init__(self, exception, offset): self.exception = exception self.offset = offset DEFAULT_EDNS_PAYLOAD = 1232 MAX_CHAIN = 16
[docs]class Message: """A DNS message.""" _section_enum = MessageSection def __init__(self, id=None): if id is None: self.id = dns.entropy.random_16() else: self.id = id self.flags = 0 self.sections = [[], [], [], []] self.opt = None self.request_payload = 0 self.keyring = None self.tsig = None self.request_mac = b'' self.xfr = False self.origin = None self.tsig_ctx = None self.index = {} self.errors = [] @property def question(self): """ The question section.""" return self.sections[0] @question.setter def question(self, v): self.sections[0] = v @property def answer(self): """ The answer section.""" return self.sections[1] @answer.setter def answer(self, v): self.sections[1] = v @property def authority(self): """ The authority section.""" return self.sections[2] @authority.setter def authority(self, v): self.sections[2] = v @property def additional(self): """ The additional data section.""" return self.sections[3] @additional.setter def additional(self, v): self.sections[3] = v def __repr__(self): return '<DNS message, ID ' + repr(self.id) + '>' def __str__(self): return self.to_text()
[docs] 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 ``str``. """ s = io.StringIO() s.write('id %d\n' % self.id) s.write('opcode %s\n' % dns.opcode.to_text(self.opcode())) s.write('rcode %s\n' % dns.rcode.to_text(self.rcode())) s.write('flags %s\n' % dns.flags.to_text(self.flags)) if self.edns >= 0: s.write('edns %s\n' % self.edns) if self.ednsflags != 0: s.write('eflags %s\n' % dns.flags.edns_to_text(self.ednsflags)) s.write('payload %d\n' % self.payload) for opt in self.options: s.write('option %s\n' % opt.to_text()) for (name, which) in self._section_enum.__members__.items(): s.write(f';{name}\n') for rrset in self.section_from_number(which): s.write(rrset.to_text(origin, relativize, **kw)) s.write('\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 i, section in enumerate(self.sections): other_section = other.sections[i] for n in section: if n not in other_section: return False for n in other_section: if n not in section: return False return True def __ne__(self, other): return not self.__eq__(other)
[docs] def is_response(self, other): """Is *other*, also a ``dns.message.Message``, a response to this message? 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 other.rcode() in {dns.rcode.FORMERR, dns.rcode.SERVFAIL, dns.rcode.NOTIMP, dns.rcode.REFUSED}: # We don't check the question section in these cases if # the other question section is empty, even though they # still really ought to have a question section. if len(other.question) == 0: return True if dns.opcode.is_update(self.flags): # This is assuming the "sender doesn't include anything # from the update", but we don't care to check the other # case, which is that all the sections are returned and # identical. 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
[docs] def section_number(self, section): """Return the "section number" of the specified section for use in indexing. *section* is one of the section attributes of this message. Raises ``ValueError`` if the section isn't known. Returns an ``int``. """ for i, our_section in enumerate(self.sections): if section is our_section: return self._section_enum(i) raise ValueError('unknown section')
[docs] def section_from_number(self, number): """Return the section list associated with the specified section number. *number* is a section number `int` or the text form of a section name. Raises ``ValueError`` if the section isn't known. Returns a ``list``. """ section = self._section_enum.make(number) return self.sections[section]
[docs] 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.full_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
[docs] 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
[docs] def to_wire(self, origin=None, max_size=0, multi=False, tsig_ctx=None, **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. If ``None``, and the message has an origin attribute that is not ``None``, then it will be used. *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". *multi*, a ``bool``, should be set to ``True`` if this message is part of a multiple message sequence. *tsig_ctx*, a ``dns.tsig.HMACTSig`` or ``dns.tsig.GSSTSig`` object, the ongoing TSIG context, used when signing zone transfers. Raises ``dns.exception.TooBig`` if *max_size* was exceeded. Returns a ``bytes``. """ if origin is None and self.origin is not None: origin = self.origin 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.opt is not None: r.add_rrset(dns.renderer.ADDITIONAL, self.opt) for rrset in self.additional: r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw) r.write_header() if self.tsig is not None: (new_tsig, ctx) = dns.tsig.sign(r.get_wire(), self.keyring, self.tsig[0], int(time.time()), self.request_mac, tsig_ctx, multi) self.tsig.clear() self.tsig.add(new_tsig) r.add_rrset(dns.renderer.ADDITIONAL, self.tsig) r.write_header() if multi: self.tsig_ctx = ctx return r.get_wire()
@staticmethod def _make_tsig(keyname, algorithm, time_signed, fudge, mac, original_id, error, other): tsig = dns.rdtypes.ANY.TSIG.TSIG(dns.rdataclass.ANY, dns.rdatatype.TSIG, algorithm, time_signed, fudge, mac, original_id, error, other) return dns.rrset.from_rdata(keyname, 0, tsig)
[docs] 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 key should be added. *key*, a ``dns.tsig.Key`` is the key to use. If a key is specified, the *keyring* and *algorithm* fields are not used. *keyring*, a ``dict``, ``callable`` or ``dns.tsig.Key``, is either the TSIG keyring or key to use. The format of a keyring dict is a mapping from TSIG key name, as ``dns.name.Name`` to ``dns.tsig.Key`` or a TSIG secret, a ``bytes``. If a ``dict`` *keyring* is specified but a *keyname* is not, 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 ``dict`` keyring is used, unless they know the keyring contains only one key. If a ``callable`` keyring is specified, the callable will be called with the message and the keyname, and is expected to return a key. *keyname*, a ``dns.name.Name``, ``str`` or ``None``, the name of this TSIG key to use; defaults to ``None``. If *keyring* is a ``dict``, the key must be defined in it. If *keyring* is a ``dns.tsig.Key``, this is ignored. *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 ``bytes``, the TSIG other data. *algorithm*, a ``dns.name.Name``, the TSIG algorithm to use. This is only used if *keyring* is a ``dict``, and the key entry is a ``bytes``. """ if isinstance(keyring, dns.tsig.Key): key = keyring keyname = key.name elif callable(keyring): key = keyring(self, keyname) else: if isinstance(keyname, str): keyname = dns.name.from_text(keyname) if keyname is None: keyname = next(iter(keyring)) key = keyring[keyname] if isinstance(key, bytes): key = dns.tsig.Key(keyname, key, algorithm) self.keyring = key if original_id is None: original_id = self.id self.tsig = self._make_tsig(keyname, self.keyring.algorithm, 0, fudge, b'', original_id, tsig_error, other_data)
@property def keyname(self): if self.tsig: return self.tsig.name else: return None @property def keyalgorithm(self): if self.tsig: return self.tsig[0].algorithm else: return None @property def mac(self): if self.tsig: return self.tsig[0].mac else: return None @property def tsig_error(self): if self.tsig: return self.tsig[0].error else: return None @property def had_tsig(self): return bool(self.tsig) @staticmethod def _make_opt(flags=0, payload=DEFAULT_EDNS_PAYLOAD, options=None): opt = dns.rdtypes.ANY.OPT.OPT(payload, dns.rdatatype.OPT, options or ()) return dns.rrset.from_rdata(dns.name.root, int(flags), opt)
[docs] def use_edns(self, edns=0, ednsflags=0, payload=DEFAULT_EDNS_PAYLOAD, 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 elif edns is True: edns = 0 if edns < 0: self.opt = None self.request_payload = 0 else: # make sure the EDNS version in ednsflags agrees with edns ednsflags &= 0xFF00FFFF ednsflags |= (edns << 16) if options is None: options = [] self.opt = self._make_opt(ednsflags, payload, options) if request_payload is None: request_payload = payload self.request_payload = request_payload
@property def edns(self): if self.opt: return (self.ednsflags & 0xff0000) >> 16 else: return -1 @property def ednsflags(self): if self.opt: return self.opt.ttl else: return 0 @ednsflags.setter def ednsflags(self, v): if self.opt: self.opt.ttl = v elif v: self.opt = self._make_opt(v) @property def payload(self): if self.opt: return self.opt[0].payload else: return 0 @property def options(self): if self.opt: return self.opt[0].options else: return ()
[docs] 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: self.ednsflags |= dns.flags.DO elif self.opt: self.ednsflags &= ~dns.flags.DO
[docs] def rcode(self): """Return the rcode. Returns an ``int``. """ return dns.rcode.from_flags(int(self.flags), int(self.ednsflags))
[docs] 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 &= 0x00FFFFFF self.ednsflags |= evalue
[docs] def opcode(self): """Return the opcode. Returns an ``int``. """ return dns.opcode.from_flags(int(self.flags))
[docs] 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)
def _get_one_rr_per_rrset(self, value): # What the caller picked is fine. return value # pylint: disable=unused-argument def _parse_rr_header(self, section, name, rdclass, rdtype): return (rdclass, rdtype, None, False) # pylint: enable=unused-argument def _parse_special_rr_header(self, section, count, position, name, rdclass, rdtype): if rdtype == dns.rdatatype.OPT: if section != MessageSection.ADDITIONAL or self.opt or \ name != dns.name.root: raise BadEDNS elif rdtype == dns.rdatatype.TSIG: if section != MessageSection.ADDITIONAL or \ rdclass != dns.rdatatype.ANY or \ position != count - 1: raise BadTSIG return (rdclass, rdtype, None, False)
[docs]class ChainingResult: """The result of a call to dns.message.QueryMessage.resolve_chaining(). The ``answer`` attribute is the answer RRSet, or ``None`` if it doesn't exist. The ``canonical_name`` attribute is the canonical name after all chaining has been applied (this is the name as ``rrset.name`` in cases where rrset is not ``None``). The ``minimum_ttl`` attribute is the minimum TTL, i.e. the TTL to use if caching the data. It is the smallest of all the CNAME TTLs and either the answer TTL if it exists or the SOA TTL and SOA minimum values for negative answers. The ``cnames`` attribute is a list of all the CNAME RRSets followed to get to the canonical name. """ def __init__(self, canonical_name, answer, minimum_ttl, cnames): self.canonical_name = canonical_name self.answer = answer self.minimum_ttl = minimum_ttl self.cnames = cnames
[docs]class QueryMessage(Message):
[docs] def resolve_chaining(self): """Follow the CNAME chain in the response to determine the answer RRset. Raises ``dns.message.NotQueryResponse`` if the message is not a response. Raises ``dns.message.ChainTooLong`` if the CNAME chain is too long. Raises ``dns.message.AnswerForNXDOMAIN`` if the rcode is NXDOMAIN but an answer was found. Raises ``dns.exception.FormError`` if the question count is not 1. Returns a ChainingResult object. """ if self.flags & dns.flags.QR == 0: raise NotQueryResponse if len(self.question) != 1: raise dns.exception.FormError question = self.question[0] qname = question.name min_ttl = dns.ttl.MAX_TTL answer = None count = 0 cnames = [] while count < MAX_CHAIN: try: answer = self.find_rrset(self.answer, qname, question.rdclass, question.rdtype) min_ttl = min(min_ttl, answer.ttl) break except KeyError: if question.rdtype != dns.rdatatype.CNAME: try: crrset = self.find_rrset(self.answer, qname, question.rdclass, dns.rdatatype.CNAME) cnames.append(crrset) min_ttl = min(min_ttl, crrset.ttl) for rd in crrset: qname = rd.target break count += 1 continue except KeyError: # Exit the chaining loop break else: # Exit the chaining loop break if count >= MAX_CHAIN: raise ChainTooLong if self.rcode() == dns.rcode.NXDOMAIN and answer is not None: raise AnswerForNXDOMAIN if answer is None: # Further minimize the TTL with NCACHE. auname = qname while True: # Look for an SOA RR whose owner name is a superdomain # of qname. try: srrset = self.find_rrset(self.authority, auname, question.rdclass, dns.rdatatype.SOA) min_ttl = min(min_ttl, srrset.ttl, srrset[0].minimum) break except KeyError: try: auname = auname.parent() except dns.name.NoParent: break return ChainingResult(qname, answer, min_ttl, cnames)
[docs] def canonical_name(self): """Return the canonical name of the first name in the question section. Raises ``dns.message.NotQueryResponse`` if the message is not a response. Raises ``dns.message.ChainTooLong`` if the CNAME chain is too long. Raises ``dns.message.AnswerForNXDOMAIN`` if the rcode is NXDOMAIN but an answer was found. Raises ``dns.exception.FormError`` if the question count is not 1. """ return self.resolve_chaining().canonical_name
def _maybe_import_update(): # We avoid circular imports by doing this here. We do it in another # function as doing it in _message_factory_from_opcode() makes "dns" # a local symbol, and the first line fails :) # pylint: disable=redefined-outer-name,import-outside-toplevel,unused-import import dns.update # noqa: F401 def _message_factory_from_opcode(opcode): if opcode == dns.opcode.QUERY: return QueryMessage elif opcode == dns.opcode.UPDATE: _maybe_import_update() return dns.update.UpdateMessage else: return Message class _WireReader: """Wire format reader. parser: the binary parser message: The message object being built initialize_message: Callback to set message parsing options question_only: Are we only reading the question? one_rr_per_rrset: Put each RR into its own RRset? keyring: TSIG keyring ignore_trailing: Ignore trailing junk at end of request? multi: Is this message part of a multi-message sequence? DNS dynamic updates. continue_on_error: try to extract as much information as possible from the message, accumulating MessageErrors in the *errors* attribute instead of raising them. """ def __init__(self, wire, initialize_message, question_only=False, one_rr_per_rrset=False, ignore_trailing=False, keyring=None, multi=False, continue_on_error=False): self.parser = dns.wire.Parser(wire) self.message = None self.initialize_message = initialize_message self.question_only = question_only self.one_rr_per_rrset = one_rr_per_rrset self.ignore_trailing = ignore_trailing self.keyring = keyring self.multi = multi self.continue_on_error = continue_on_error self.errors = [] def _get_question(self, section_number, qcount): """Read the next *qcount* records from the wire data and add them to the question section. """ section = self.message.sections[section_number] for _ in range(qcount): qname = self.parser.get_name(self.message.origin) (rdtype, rdclass) = self.parser.get_struct('!HH') (rdclass, rdtype, _, _) = \ self.message._parse_rr_header(section_number, qname, rdclass, rdtype) self.message.find_rrset(section, qname, rdclass, rdtype, create=True, force_unique=True) def _add_error(self, e): self.errors.append(MessageError(e, self.parser.current)) def _get_section(self, section_number, count): """Read the next I{count} records from the wire data and add them to the specified section. section_number: the section of the message to which to add records count: the number of records to read """ section = self.message.sections[section_number] force_unique = self.one_rr_per_rrset for i in range(count): rr_start = self.parser.current absolute_name = self.parser.get_name() if self.message.origin is not None: name = absolute_name.relativize(self.message.origin) else: name = absolute_name (rdtype, rdclass, ttl, rdlen) = self.parser.get_struct('!HHIH') if rdtype in (dns.rdatatype.OPT, dns.rdatatype.TSIG): (rdclass, rdtype, deleting, empty) = \ self.message._parse_special_rr_header(section_number, count, i, name, rdclass, rdtype) else: (rdclass, rdtype, deleting, empty) = \ self.message._parse_rr_header(section_number, name, rdclass, rdtype) try: rdata_start = self.parser.current if empty: if rdlen > 0: raise dns.exception.FormError rd = None covers = dns.rdatatype.NONE else: with self.parser.restrict_to(rdlen): rd = dns.rdata.from_wire_parser(rdclass, rdtype, self.parser, self.message.origin) covers = rd.covers() if self.message.xfr and rdtype == dns.rdatatype.SOA: force_unique = True if rdtype == dns.rdatatype.OPT: self.message.opt = dns.rrset.from_rdata(name, ttl, rd) elif rdtype == dns.rdatatype.TSIG: if self.keyring is None: raise UnknownTSIGKey('got signed message without ' 'keyring') if isinstance(self.keyring, dict): key = self.keyring.get(absolute_name) if isinstance(key, bytes): key = dns.tsig.Key(absolute_name, key, rd.algorithm) elif callable(self.keyring): key = self.keyring(self.message, absolute_name) else: key = self.keyring if key is None: raise UnknownTSIGKey("key '%s' unknown" % name) self.message.keyring = key self.message.tsig_ctx = \ dns.tsig.validate(self.parser.wire, key, absolute_name, rd, int(time.time()), self.message.request_mac, rr_start, self.message.tsig_ctx, self.multi) self.message.tsig = dns.rrset.from_rdata(absolute_name, 0, rd) else: rrset = self.message.find_rrset(section, name, rdclass, rdtype, covers, deleting, True, force_unique) if rd is not None: if ttl > 0x7fffffff: ttl = 0 rrset.add(rd, ttl) except Exception as e: if self.continue_on_error: self._add_error(e) self.parser.seek(rdata_start + rdlen) else: raise def read(self): """Read a wire format DNS message and build a dns.message.Message object.""" if self.parser.remaining() < 12: raise ShortHeader (id, flags, qcount, ancount, aucount, adcount) = \ self.parser.get_struct('!HHHHHH') factory = _message_factory_from_opcode(dns.opcode.from_flags(flags)) self.message = factory(id=id) self.message.flags = dns.flags.Flag(flags) self.initialize_message(self.message) self.one_rr_per_rrset = \ self.message._get_one_rr_per_rrset(self.one_rr_per_rrset) try: self._get_question(MessageSection.QUESTION, qcount) if self.question_only: return self.message self._get_section(MessageSection.ANSWER, ancount) self._get_section(MessageSection.AUTHORITY, aucount) self._get_section(MessageSection.ADDITIONAL, adcount) if not self.ignore_trailing and self.parser.remaining() != 0: raise TrailingJunk if self.multi and self.message.tsig_ctx and \ not self.message.had_tsig: self.message.tsig_ctx.update(self.parser.wire) except Exception as e: if self.continue_on_error: self._add_error(e) else: raise return self.message
[docs]def from_wire(wire, keyring=None, request_mac=b'', xfr=False, origin=None, tsig_ctx=None, multi=False, question_only=False, one_rr_per_rrset=False, ignore_trailing=False, raise_on_truncation=False, continue_on_error=False): """Convert a DNS wire format message into a message object. *keyring*, a ``dns.tsig.Key`` or ``dict``, the key or keyring to use if the message is signed. *request_mac*, a ``bytes``. 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. If not ``None``, names will be relativized to the origin. *tsig_ctx*, a ``dns.tsig.HMACTSig`` or ``dns.tsig.GSSTSig`` object, the ongoing TSIG context, used when validating zone transfers. *multi*, a ``bool``, should be set to ``True`` if this message is part of a multiple 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. *raise_on_truncation*, a ``bool``. If ``True``, raise an exception if the TC bit is set. *continue_on_error*, a ``bool``. If ``True``, try to continue parsing even if errors occur. Erroneous rdata will be ignored. Errors will be accumulated as a list of MessageError objects in the message's ``errors`` attribute. This option is recommended only for DNS analysis tools, or for use in a server as part of an error handling path. The default is ``False``. Raises ``dns.message.ShortHeader`` if the message is less than 12 octets long. Raises ``dns.message.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. Raises ``dns.message.Truncated`` if the TC flag is set and *raise_on_truncation* is ``True``. Returns a ``dns.message.Message``. """ def initialize_message(message): message.request_mac = request_mac message.xfr = xfr message.origin = origin message.tsig_ctx = tsig_ctx reader = _WireReader(wire, initialize_message, question_only, one_rr_per_rrset, ignore_trailing, keyring, multi, continue_on_error) try: m = reader.read() except dns.exception.FormError: if reader.message and (reader.message.flags & dns.flags.TC) and \ raise_on_truncation: raise Truncated(message=reader.message) else: raise # Reading a truncated message might not have any errors, so we # have to do this check here too. if m.flags & dns.flags.TC and raise_on_truncation: raise Truncated(message=m) if continue_on_error: m.errors = reader.errors return m
class _TextReader: """Text format reader. tok: the tokenizer. message: The message object being built. DNS dynamic updates. last_name: The most recently read name when building a message object. one_rr_per_rrset: Put each RR into its own RRset? origin: The origin for relative names relativize: relativize names? relativize_to: the origin to relativize to. """ def __init__(self, text, idna_codec, one_rr_per_rrset=False, origin=None, relativize=True, relativize_to=None): self.message = None self.tok = dns.tokenizer.Tokenizer(text, idna_codec=idna_codec) self.last_name = None self.one_rr_per_rrset = one_rr_per_rrset self.origin = origin self.relativize = relativize self.relativize_to = relativize_to self.id = None self.edns = -1 self.ednsflags = 0 self.payload = DEFAULT_EDNS_PAYLOAD self.rcode = None self.opcode = dns.opcode.QUERY self.flags = 0 def _header_line(self, _): """Process one line from the text format header section.""" token = self.tok.get() what = token.value if what == 'id': self.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.flags = self.flags | dns.flags.from_text(token.value) elif what == 'edns': self.edns = self.tok.get_int() self.ednsflags = self.ednsflags | (self.edns << 16) elif what == 'eflags': if self.edns < 0: self.edns = 0 while True: token = self.tok.get() if not token.is_identifier(): self.tok.unget(token) break self.ednsflags = self.ednsflags | \ dns.flags.edns_from_text(token.value) elif what == 'payload': self.payload = self.tok.get_int() if self.edns < 0: self.edns = 0 elif what == 'opcode': text = self.tok.get_string() self.opcode = dns.opcode.from_text(text) self.flags = self.flags | dns.opcode.to_flags(self.opcode) elif what == 'rcode': text = self.tok.get_string() self.rcode = dns.rcode.from_text(text) else: raise UnknownHeaderField self.tok.get_eol() def _question_line(self, section_number): """Process one line from the text format question section.""" section = self.message.sections[section_number] token = self.tok.get(want_leading=True) if not token.is_whitespace(): self.last_name = self.tok.as_name(token, self.message.origin, self.relativize, self.relativize_to) name = self.last_name if name is None: raise NoPreviousName 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) (rdclass, rdtype, _, _) = \ self.message._parse_rr_header(section_number, name, rdclass, rdtype) self.message.find_rrset(section, name, rdclass, rdtype, create=True, force_unique=True) self.tok.get_eol() def _rr_line(self, section_number): """Process one line from the text format answer, authority, or additional data sections. """ section = self.message.sections[section_number] # Name token = self.tok.get(want_leading=True) if not token.is_whitespace(): self.last_name = self.tok.as_name(token, self.message.origin, self.relativize, self.relativize_to) name = self.last_name if name is None: raise NoPreviousName 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 except dns.exception.SyntaxError: raise dns.exception.SyntaxError except Exception: rdclass = dns.rdataclass.IN # Type rdtype = dns.rdatatype.from_text(token.value) (rdclass, rdtype, deleting, empty) = \ self.message._parse_rr_header(section_number, name, rdclass, rdtype) token = self.tok.get() if empty and not token.is_eol_or_eof(): raise dns.exception.SyntaxError if not empty and token.is_eol_or_eof(): raise dns.exception.UnexpectedEnd if not token.is_eol_or_eof(): self.tok.unget(token) rd = dns.rdata.from_text(rdclass, rdtype, self.tok, self.message.origin, self.relativize, self.relativize_to) covers = rd.covers() else: rd = None covers = dns.rdatatype.NONE rrset = self.message.find_rrset(section, name, rdclass, rdtype, covers, deleting, True, self.one_rr_per_rrset) if rd is not None: rrset.add(rd, ttl) def _make_message(self): factory = _message_factory_from_opcode(self.opcode) message = factory(id=self.id) message.flags = self.flags if self.edns >= 0: message.use_edns(self.edns, self.ednsflags, self.payload) if self.rcode: message.set_rcode(self.rcode) if self.origin: message.origin = self.origin return message def read(self): """Read a text format DNS message and build a dns.message.Message object.""" line_method = self._header_line section_number = 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 if self.message: message = self.message else: # If we don't have a message, create one with the current # opcode, so that we know which section names to parse. message = self._make_message() try: section_number = message._section_enum.from_text(u) # We found a section name. If we don't have a message, # use the one we just created. if not self.message: self.message = message self.one_rr_per_rrset = \ message._get_one_rr_per_rrset(self.one_rr_per_rrset) if section_number == MessageSection.QUESTION: line_method = self._question_line else: line_method = self._rr_line except Exception: # It's just a comment. pass self.tok.get_eol() continue self.tok.unget(token) line_method(section_number) if not self.message: self.message = self._make_message() return self.message
[docs]def from_text(text, idna_codec=None, one_rr_per_rrset=False, origin=None, relativize=True, relativize_to=None): """Convert the text format message into a message object. The reader stops after reading the first blank line in the input to facilitate reading multiple messages from a single file with ``dns.message.from_file()``. *text*, a ``str``, the text format message. *idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder is used. *one_rr_per_rrset*, a ``bool``. If ``True``, then each RR is put into its own rrset. The default is ``False``. *origin*, a ``dns.name.Name`` (or ``None``), the origin to use for relative names. *relativize*, a ``bool``. If true, name will be relativized. *relativize_to*, a ``dns.name.Name`` (or ``None``), the origin to use when relativizing names. If not set, the *origin* value will be used. 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(). reader = _TextReader(text, idna_codec, one_rr_per_rrset, origin, relativize, relativize_to) return reader.read()
[docs]def from_file(f, idna_codec=None, one_rr_per_rrset=False): """Read the next text format message from the specified file. Message blocks are separated by a single blank line. *f*, a ``file`` or ``str``. If *f* is text, it is treated as the pathname of a file to open. *idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder is used. *one_rr_per_rrset*, a ``bool``. If ``True``, then each RR is put into its own rrset. The default is ``False``. 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`` """ with contextlib.ExitStack() as stack: if isinstance(f, str): f = stack.enter_context(open(f)) return from_text(f, idna_codec, one_rr_per_rrset)
[docs]def make_query(qname, rdtype, rdclass=dns.rdataclass.IN, use_edns=None, want_dnssec=False, ednsflags=None, payload=None, request_payload=None, options=None, idna_codec=None, id=None, flags=dns.flags.RD): """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 ``str``, the query name. *rdtype*, an ``int`` or ``str``, the desired rdata type. *rdclass*, an ``int`` or ``str``, 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``. If ``None``, EDNS will be enabled only if other parameters (*ednsflags*, *payload*, *request_payload*, or *options*) are set. 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. *idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder is used. *id*, an ``int`` or ``None``, the desired query id. The default is ``None``, which generates a random query id. *flags*, an ``int``, the desired query flags. The default is ``dns.flags.RD``. Returns a ``dns.message.QueryMessage`` """ if isinstance(qname, str): qname = dns.name.from_text(qname, idna_codec=idna_codec) rdtype = dns.rdatatype.RdataType.make(rdtype) rdclass = dns.rdataclass.RdataClass.make(rdclass) m = QueryMessage(id=id) m.flags = dns.flags.Flag(flags) 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 payload is not None: kwargs['payload'] = payload if request_payload is not None: kwargs['request_payload'] = request_payload if options is not None: kwargs['options'] = options if kwargs and use_edns is None: use_edns = 0 kwargs['edns'] = use_edns m.use_edns(**kwargs) m.want_dnssec(want_dnssec) return m
[docs]def make_response(query, recursion_available=False, our_payload=8192, fudge=300, tsig_error=0): """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. *tsig_error*, an ``int``, the TSIG error. Returns a ``dns.message.Message`` object whose specific class is appropriate for the query. For example, if query is a ``dns.update.UpdateMessage``, response will be too. """ if query.flags & dns.flags.QR: raise dns.exception.FormError('specified query message is not a query') factory = _message_factory_from_opcode(query.opcode()) response = factory(id=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, tsig_error, b'', query.keyalgorithm) response.request_mac = query.mac return response
### BEGIN generated MessageSection constants QUESTION = MessageSection.QUESTION ANSWER = MessageSection.ANSWER AUTHORITY = MessageSection.AUTHORITY ADDITIONAL = MessageSection.ADDITIONAL ### END generated MessageSection constants