# 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"""
import contextlib
import io
import time
from typing import Any, Dict, List, Optional, Tuple, Union
import dns.edns
import dns.entropy
import dns.enum
import dns.exception
import dns.flags
import dns.name
import dns.opcode
import dns.rcode
import dns.rdata
import dns.rdataclass
import dns.rdatatype
import dns.rdtypes.ANY.OPT
import dns.rdtypes.ANY.TSIG
import dns.renderer
import dns.rrset
import dns.tsig
import dns.ttl
import dns.wire
[docs]
class TrailingJunk(dns.exception.FormError):
"""The DNS packet passed to from_wire() has extra junk at the end of it."""
[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"}
# We do this as otherwise mypy complains about unexpected keyword argument
# idna_exception
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
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: Exception, offset: int):
self.exception = exception
self.offset = offset
DEFAULT_EDNS_PAYLOAD = 1232
MAX_CHAIN = 16
IndexKeyType = Tuple[
int,
dns.name.Name,
dns.rdataclass.RdataClass,
dns.rdatatype.RdataType,
Optional[dns.rdatatype.RdataType],
Optional[dns.rdataclass.RdataClass],
]
IndexType = Dict[IndexKeyType, dns.rrset.RRset]
SectionType = Union[int, str, List[dns.rrset.RRset]]
[docs]
class Message:
"""A DNS message."""
_section_enum = MessageSection
def __init__(self, id: Optional[int] = None):
if id is None:
self.id = dns.entropy.random_16()
else:
self.id = id
self.flags = 0
self.sections: List[List[dns.rrset.RRset]] = [[], [], [], []]
self.opt: Optional[dns.rrset.RRset] = None
self.request_payload = 0
self.pad = 0
self.keyring: Any = None
self.tsig: Optional[dns.rrset.RRset] = None
self.request_mac = b""
self.xfr = False
self.origin: Optional[dns.name.Name] = None
self.tsig_ctx: Optional[Any] = None
self.index: IndexType = {}
self.errors: List[MessageError] = []
self.time = 0.0
@property
def question(self) -> List[dns.rrset.RRset]:
"""The question section."""
return self.sections[0]
@question.setter
def question(self, v):
self.sections[0] = v
@property
def answer(self) -> List[dns.rrset.RRset]:
"""The answer section."""
return self.sections[1]
@answer.setter
def answer(self, v):
self.sections[1] = v
@property
def authority(self) -> List[dns.rrset.RRset]:
"""The authority section."""
return self.sections[2]
@authority.setter
def authority(self, v):
self.sections[2] = v
@property
def additional(self) -> List[dns.rrset.RRset]:
"""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: Optional[dns.name.Name] = None,
relativize: bool = True,
**kw: Dict[str, Any],
) -> str:
"""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: "Message") -> bool:
"""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: List[dns.rrset.RRset]) -> int:
"""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: int) -> List[dns.rrset.RRset]:
"""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: SectionType,
name: dns.name.Name,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
deleting: Optional[dns.rdataclass.RdataClass] = None,
create: bool = False,
force_unique: bool = False,
idna_codec: Optional[dns.name.IDNACodec] = None,
) -> dns.rrset.RRset:
"""Find the RRset with the given attributes in the specified section.
*section*, an ``int`` section number, a ``str`` section name, 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)
my_message.find_rrset("ANSWER", name, rdclass, rdtype)
*name*, a ``dns.name.Name`` or ``str``, the name of the RRset.
*rdclass*, an ``int`` or ``str``, the class of the RRset.
*rdtype*, an ``int`` or ``str``, the type of the RRset.
*covers*, an ``int`` or ``str``, the covers value of the RRset.
The default is ``dns.rdatatype.NONE``.
*deleting*, an ``int``, ``str``, 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.
*idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA
encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder
is used.
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)
elif isinstance(section, str):
section_number = self._section_enum.from_text(section)
section = self.section_from_number(section_number)
else:
section_number = self.section_number(section)
if isinstance(name, str):
name = dns.name.from_text(name, idna_codec=idna_codec)
rdtype = dns.rdatatype.RdataType.make(rdtype)
rdclass = dns.rdataclass.RdataClass.make(rdclass)
covers = dns.rdatatype.RdataType.make(covers)
if deleting is not None:
deleting = dns.rdataclass.RdataClass.make(deleting)
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: SectionType,
name: dns.name.Name,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
deleting: Optional[dns.rdataclass.RdataClass] = None,
create: bool = False,
force_unique: bool = False,
idna_codec: Optional[dns.name.IDNACodec] = None,
) -> Optional[dns.rrset.RRset]:
"""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, a ``str`` section name, 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)
my_message.get_rrset("ANSWER", name, rdclass, rdtype)
*name*, a ``dns.name.Name`` or ``str``, the name of the RRset.
*rdclass*, an ``int`` or ``str``, the class of the RRset.
*rdtype*, an ``int`` or ``str``, the type of the RRset.
*covers*, an ``int`` or ``str``, the covers value of the RRset.
The default is ``dns.rdatatype.NONE``.
*deleting*, an ``int``, ``str``, 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.
*idna_codec*, a ``dns.name.IDNACodec``, specifies the IDNA
encoder/decoder. If ``None``, the default IDNA 2003 encoder/decoder
is used.
Returns a ``dns.rrset.RRset object`` or ``None``.
"""
try:
rrset = self.find_rrset(
section,
name,
rdclass,
rdtype,
covers,
deleting,
create,
force_unique,
idna_codec,
)
except KeyError:
rrset = None
return rrset
[docs]
def section_count(self, section: SectionType) -> int:
"""Returns the number of records in the specified section.
*section*, an ``int`` section number, a ``str`` section name, or one of
the section attributes of this message. This specifies the
the section of the message to count. For example::
my_message.section_count(my_message.answer)
my_message.section_count(dns.message.ANSWER)
my_message.section_count("ANSWER")
"""
if isinstance(section, int):
section_number = section
section = self.section_from_number(section_number)
elif isinstance(section, str):
section_number = self._section_enum.from_text(section)
section = self.section_from_number(section_number)
else:
section_number = self.section_number(section)
count = sum(max(1, len(rrs)) for rrs in section)
if section_number == MessageSection.ADDITIONAL:
if self.opt is not None:
count += 1
if self.tsig is not None:
count += 1
return count
def _compute_opt_reserve(self) -> int:
"""Compute the size required for the OPT RR, padding excluded"""
if not self.opt:
return 0
# 1 byte for the root name, 10 for the standard RR fields
size = 11
# This would be more efficient if options had a size() method, but we won't
# worry about that for now. We also don't worry if there is an existing padding
# option, as it is unlikely and probably harmless, as the worst case is that we
# may add another, and this seems to be legal.
for option in self.opt[0].options:
wire = option.to_wire()
# We add 4 here to account for the option type and length
size += len(wire) + 4
if self.pad:
# Padding will be added, so again add the option type and length.
size += 4
return size
def _compute_tsig_reserve(self) -> int:
"""Compute the size required for the TSIG RR"""
# This would be more efficient if TSIGs had a size method, but we won't
# worry about for now. Also, we can't really cope with the potential
# compressibility of the TSIG owner name, so we estimate with the uncompressed
# size. We will disable compression when TSIG and padding are both is active
# so that the padding comes out right.
if not self.tsig:
return 0
f = io.BytesIO()
self.tsig.to_wire(f)
return len(f.getvalue())
[docs]
def to_wire(
self,
origin: Optional[dns.name.Name] = None,
max_size: int = 0,
multi: bool = False,
tsig_ctx: Optional[Any] = None,
prepend_length: bool = False,
prefer_truncation: bool = False,
**kw: Dict[str, Any],
) -> bytes:
"""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.
*prepend_length*, a ``bool``, should be set to ``True`` if the caller
wants the message length prepended to the message itself. This is
useful for messages sent over TCP, TLS (DoT), or QUIC (DoQ).
*prefer_truncation*, a ``bool``, should be set to ``True`` if the caller
wants the message to be truncated if it would otherwise exceed the
maximum length. If the truncation occurs before the additional section,
the TC bit will be set.
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)
opt_reserve = self._compute_opt_reserve()
r.reserve(opt_reserve)
tsig_reserve = self._compute_tsig_reserve()
r.reserve(tsig_reserve)
try:
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)
for rrset in self.additional:
r.add_rrset(dns.renderer.ADDITIONAL, rrset, **kw)
except dns.exception.TooBig:
if prefer_truncation:
if r.section < dns.renderer.ADDITIONAL:
r.flags |= dns.flags.TC
else:
raise
r.release_reserved()
if self.opt is not None:
r.add_opt(self.opt, self.pad, opt_reserve, tsig_reserve)
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
wire = r.get_wire()
if prepend_length:
wire = len(wire).to_bytes(2, "big") + wire
return 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: Any,
keyname: Optional[Union[dns.name.Name, str]] = None,
fudge: int = 300,
original_id: Optional[int] = None,
tsig_error: int = 0,
other_data: bytes = b"",
algorithm: Union[dns.name.Name, str] = dns.tsig.default_algorithm,
) -> None:
"""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`` or ``str``, 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"\x00" * dns.tsig.mac_sizes[self.keyring.algorithm],
original_id,
tsig_error,
other_data,
)
@property
def keyname(self) -> Optional[dns.name.Name]:
if self.tsig:
return self.tsig.name
else:
return None
@property
def keyalgorithm(self) -> Optional[dns.name.Name]:
if self.tsig:
return self.tsig[0].algorithm
else:
return None
@property
def mac(self) -> Optional[bytes]:
if self.tsig:
return self.tsig[0].mac
else:
return None
@property
def tsig_error(self) -> Optional[int]:
if self.tsig:
return self.tsig[0].error
else:
return None
@property
def had_tsig(self) -> bool:
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: Optional[Union[int, bool]] = 0,
ednsflags: int = 0,
payload: int = DEFAULT_EDNS_PAYLOAD,
request_payload: Optional[int] = None,
options: Optional[List[dns.edns.Option]] = None,
pad: int = 0,
) -> 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.
*pad*, a non-negative ``int``. If 0, the default, do not pad; otherwise add
padding bytes to make the message size a multiple of *pad*. Note that if
padding is non-zero, an EDNS PADDING option will always be added to the
message.
"""
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
if pad < 0:
raise ValueError("pad must be non-negative")
self.pad = pad
@property
def edns(self) -> int:
if self.opt:
return (self.ednsflags & 0xFF0000) >> 16
else:
return -1
@property
def ednsflags(self) -> int:
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) -> int:
if self.opt:
return self.opt[0].payload
else:
return 0
@property
def options(self) -> Tuple:
if self.opt:
return self.opt[0].options
else:
return ()
[docs]
def want_dnssec(self, wanted: bool = True) -> None:
"""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 &= ~int(dns.flags.DO)
[docs]
def rcode(self) -> dns.rcode.Rcode:
"""Return the rcode.
Returns a ``dns.rcode.Rcode``.
"""
return dns.rcode.from_flags(int(self.flags), int(self.ednsflags))
[docs]
def set_rcode(self, rcode: dns.rcode.Rcode) -> None:
"""Set the rcode.
*rcode*, a ``dns.rcode.Rcode``, 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) -> dns.opcode.Opcode:
"""Return the opcode.
Returns a ``dns.opcode.Opcode``.
"""
return dns.opcode.from_flags(int(self.flags))
[docs]
def set_opcode(self, opcode: dns.opcode.Opcode) -> None:
"""Set the opcode.
*opcode*, a ``dns.opcode.Opcode``, 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 same 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: dns.name.Name,
answer: Optional[dns.rrset.RRset],
minimum_ttl: int,
cnames: List[dns.rrset.RRset],
):
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) -> ChainingResult:
"""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) -> dns.name.Name:
"""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.
"""
assert self.message is not None
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
"""
assert self.message is not None
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
)
rdata_start = self.parser.current
try:
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: bytes,
keyring: Optional[Any] = None,
request_mac: Optional[bytes] = b"",
xfr: bool = False,
origin: Optional[dns.name.Name] = None,
tsig_ctx: Optional[Union[dns.tsig.HMACTSig, dns.tsig.GSSTSig]] = None,
multi: bool = False,
question_only: bool = False,
one_rr_per_rrset: bool = False,
ignore_trailing: bool = False,
raise_on_truncation: bool = False,
continue_on_error: bool = False,
) -> Message:
"""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`` or ``None``. 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``.
"""
# We permit None for request_mac solely for backwards compatibility
if request_mac is None:
request_mac = b""
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: str,
idna_codec: Optional[dns.name.IDNACodec] = None,
one_rr_per_rrset: bool = False,
origin: Optional[dns.name.Name] = None,
relativize: bool = True,
relativize_to: Optional[dns.name.Name] = None,
) -> Message:
"""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: Any,
idna_codec: Optional[dns.name.IDNACodec] = None,
one_rr_per_rrset: bool = False,
) -> Message:
"""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``
"""
if isinstance(f, str):
cm: contextlib.AbstractContextManager = open(f)
else:
cm = contextlib.nullcontext(f)
with cm as f:
return from_text(f, idna_codec, one_rr_per_rrset)
assert False # for mypy lgtm[py/unreachable-statement]
[docs]
def make_query(
qname: Union[dns.name.Name, str],
rdtype: Union[dns.rdatatype.RdataType, str],
rdclass: Union[dns.rdataclass.RdataClass, str] = dns.rdataclass.IN,
use_edns: Optional[Union[int, bool]] = None,
want_dnssec: bool = False,
ednsflags: Optional[int] = None,
payload: Optional[int] = None,
request_payload: Optional[int] = None,
options: Optional[List[dns.edns.Option]] = None,
idna_codec: Optional[dns.name.IDNACodec] = None,
id: Optional[int] = None,
flags: int = dns.flags.RD,
pad: int = 0,
) -> QueryMessage:
"""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``.
*pad*, a non-negative ``int``. If 0, the default, do not pad; otherwise add
padding bytes to make the message size a multiple of *pad*. Note that if
padding is non-zero, an EDNS PADDING option will always be added to the
message.
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: Dict[str, Any] = {}
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
kwargs["pad"] = pad
m.use_edns(**kwargs)
m.want_dnssec(want_dnssec)
return m
[docs]
def make_response(
query: Message,
recursion_available: bool = False,
our_payload: int = 8192,
fudge: int = 300,
tsig_error: int = 0,
pad: Optional[int] = None,
) -> Message:
"""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.
*pad*, a non-negative ``int`` or ``None``. If 0, the default, do not pad; otherwise
if not ``None`` add padding bytes to make the message size a multiple of *pad*.
Note that if padding is non-zero, an EDNS PADDING option will always be added to the
message. If ``None``, add padding following RFC 8467, namely if the request is
padded, pad the response to 468 otherwise do not pad.
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:
if pad is None:
# Set response padding per RFC 8467
pad = 0
for option in query.options:
if option.otype == dns.edns.OptionType.PADDING:
pad = 468
response.use_edns(0, 0, our_payload, query.payload, pad=pad)
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