344 lines
13 KiB
Python
344 lines
13 KiB
Python
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# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
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# Copyright (C) 2003-2017 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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from typing import Any, List, Optional, Tuple, Union
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import dns.exception
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import dns.message
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import dns.name
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import dns.rcode
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import dns.rdataset
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import dns.rdatatype
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import dns.serial
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import dns.transaction
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import dns.tsig
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import dns.zone
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class TransferError(dns.exception.DNSException):
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"""A zone transfer response got a non-zero rcode."""
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def __init__(self, rcode):
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message = "Zone transfer error: %s" % dns.rcode.to_text(rcode)
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super().__init__(message)
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self.rcode = rcode
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class SerialWentBackwards(dns.exception.FormError):
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"""The current serial number is less than the serial we know."""
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class UseTCP(dns.exception.DNSException):
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"""This IXFR cannot be completed with UDP."""
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class Inbound:
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"""
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State machine for zone transfers.
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"""
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def __init__(
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self,
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txn_manager: dns.transaction.TransactionManager,
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rdtype: dns.rdatatype.RdataType = dns.rdatatype.AXFR,
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serial: Optional[int] = None,
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is_udp: bool = False,
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):
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"""Initialize an inbound zone transfer.
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*txn_manager* is a :py:class:`dns.transaction.TransactionManager`.
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*rdtype* can be `dns.rdatatype.AXFR` or `dns.rdatatype.IXFR`
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*serial* is the base serial number for IXFRs, and is required in
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that case.
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*is_udp*, a ``bool`` indidicates if UDP is being used for this
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XFR.
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"""
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self.txn_manager = txn_manager
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self.txn: Optional[dns.transaction.Transaction] = None
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self.rdtype = rdtype
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if rdtype == dns.rdatatype.IXFR:
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if serial is None:
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raise ValueError("a starting serial must be supplied for IXFRs")
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elif is_udp:
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raise ValueError("is_udp specified for AXFR")
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self.serial = serial
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self.is_udp = is_udp
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(_, _, self.origin) = txn_manager.origin_information()
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self.soa_rdataset: Optional[dns.rdataset.Rdataset] = None
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self.done = False
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self.expecting_SOA = False
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self.delete_mode = False
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def process_message(self, message: dns.message.Message) -> bool:
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"""Process one message in the transfer.
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The message should have the same relativization as was specified when
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the `dns.xfr.Inbound` was created. The message should also have been
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created with `one_rr_per_rrset=True` because order matters.
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Returns `True` if the transfer is complete, and `False` otherwise.
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"""
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if self.txn is None:
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replacement = self.rdtype == dns.rdatatype.AXFR
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self.txn = self.txn_manager.writer(replacement)
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rcode = message.rcode()
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if rcode != dns.rcode.NOERROR:
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raise TransferError(rcode)
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#
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# We don't require a question section, but if it is present is
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# should be correct.
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#
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if len(message.question) > 0:
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if message.question[0].name != self.origin:
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raise dns.exception.FormError("wrong question name")
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if message.question[0].rdtype != self.rdtype:
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raise dns.exception.FormError("wrong question rdatatype")
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answer_index = 0
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if self.soa_rdataset is None:
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#
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# This is the first message. We're expecting an SOA at
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# the origin.
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#
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if not message.answer or message.answer[0].name != self.origin:
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raise dns.exception.FormError("No answer or RRset not for zone origin")
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rrset = message.answer[0]
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rdataset = rrset
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if rdataset.rdtype != dns.rdatatype.SOA:
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raise dns.exception.FormError("first RRset is not an SOA")
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answer_index = 1
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self.soa_rdataset = rdataset.copy()
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if self.rdtype == dns.rdatatype.IXFR:
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if self.soa_rdataset[0].serial == self.serial:
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#
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# We're already up-to-date.
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#
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self.done = True
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elif dns.serial.Serial(self.soa_rdataset[0].serial) < self.serial:
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# It went backwards!
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raise SerialWentBackwards
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else:
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if self.is_udp and len(message.answer[answer_index:]) == 0:
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#
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# There are no more records, so this is the
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# "truncated" response. Say to use TCP
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#
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raise UseTCP
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#
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# Note we're expecting another SOA so we can detect
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# if this IXFR response is an AXFR-style response.
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#
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self.expecting_SOA = True
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#
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# Process the answer section (other than the initial SOA in
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# the first message).
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#
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for rrset in message.answer[answer_index:]:
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name = rrset.name
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rdataset = rrset
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if self.done:
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raise dns.exception.FormError("answers after final SOA")
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assert self.txn is not None # for mypy
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if rdataset.rdtype == dns.rdatatype.SOA and name == self.origin:
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#
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# Every time we see an origin SOA delete_mode inverts
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#
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if self.rdtype == dns.rdatatype.IXFR:
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self.delete_mode = not self.delete_mode
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#
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# If this SOA Rdataset is equal to the first we saw
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# then we're finished. If this is an IXFR we also
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# check that we're seeing the record in the expected
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# part of the response.
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#
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if rdataset == self.soa_rdataset and (
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self.rdtype == dns.rdatatype.AXFR
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or (self.rdtype == dns.rdatatype.IXFR and self.delete_mode)
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):
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#
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# This is the final SOA
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#
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if self.expecting_SOA:
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# We got an empty IXFR sequence!
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raise dns.exception.FormError("empty IXFR sequence")
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if (
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self.rdtype == dns.rdatatype.IXFR
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and self.serial != rdataset[0].serial
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):
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raise dns.exception.FormError("unexpected end of IXFR sequence")
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self.txn.replace(name, rdataset)
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self.txn.commit()
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self.txn = None
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self.done = True
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else:
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#
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# This is not the final SOA
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#
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self.expecting_SOA = False
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if self.rdtype == dns.rdatatype.IXFR:
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if self.delete_mode:
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# This is the start of an IXFR deletion set
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if rdataset[0].serial != self.serial:
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raise dns.exception.FormError(
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"IXFR base serial mismatch"
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)
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else:
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# This is the start of an IXFR addition set
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self.serial = rdataset[0].serial
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self.txn.replace(name, rdataset)
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else:
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# We saw a non-final SOA for the origin in an AXFR.
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raise dns.exception.FormError("unexpected origin SOA in AXFR")
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continue
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if self.expecting_SOA:
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#
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# We made an IXFR request and are expecting another
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# SOA RR, but saw something else, so this must be an
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# AXFR response.
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#
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self.rdtype = dns.rdatatype.AXFR
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self.expecting_SOA = False
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self.delete_mode = False
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self.txn.rollback()
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self.txn = self.txn_manager.writer(True)
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#
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# Note we are falling through into the code below
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# so whatever rdataset this was gets written.
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#
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# Add or remove the data
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if self.delete_mode:
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self.txn.delete_exact(name, rdataset)
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else:
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self.txn.add(name, rdataset)
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if self.is_udp and not self.done:
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#
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# This is a UDP IXFR and we didn't get to done, and we didn't
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# get the proper "truncated" response
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#
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raise dns.exception.FormError("unexpected end of UDP IXFR")
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return self.done
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#
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# Inbounds are context managers.
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#
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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if self.txn:
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self.txn.rollback()
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return False
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def make_query(
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txn_manager: dns.transaction.TransactionManager,
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serial: Optional[int] = 0,
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use_edns: Optional[Union[int, bool]] = None,
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ednsflags: Optional[int] = None,
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payload: Optional[int] = None,
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request_payload: Optional[int] = None,
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options: Optional[List[dns.edns.Option]] = None,
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keyring: Any = None,
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keyname: Optional[dns.name.Name] = None,
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keyalgorithm: Union[dns.name.Name, str] = dns.tsig.default_algorithm,
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) -> Tuple[dns.message.QueryMessage, Optional[int]]:
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"""Make an AXFR or IXFR query.
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*txn_manager* is a ``dns.transaction.TransactionManager``, typically a
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``dns.zone.Zone``.
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*serial* is an ``int`` or ``None``. If 0, then IXFR will be
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attempted using the most recent serial number from the
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*txn_manager*; it is the caller's responsibility to ensure there
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are no write transactions active that could invalidate the
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retrieved serial. If a serial cannot be determined, AXFR will be
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forced. Other integer values are the starting serial to use.
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``None`` forces an AXFR.
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Please see the documentation for :py:func:`dns.message.make_query` and
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:py:func:`dns.message.Message.use_tsig` for details on the other parameters
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to this function.
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Returns a `(query, serial)` tuple.
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"""
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(zone_origin, _, origin) = txn_manager.origin_information()
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if zone_origin is None:
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raise ValueError("no zone origin")
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if serial is None:
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rdtype = dns.rdatatype.AXFR
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elif not isinstance(serial, int):
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raise ValueError("serial is not an integer")
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elif serial == 0:
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with txn_manager.reader() as txn:
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rdataset = txn.get(origin, "SOA")
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if rdataset:
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serial = rdataset[0].serial
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rdtype = dns.rdatatype.IXFR
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else:
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serial = None
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rdtype = dns.rdatatype.AXFR
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elif serial > 0 and serial < 4294967296:
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rdtype = dns.rdatatype.IXFR
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else:
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raise ValueError("serial out-of-range")
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rdclass = txn_manager.get_class()
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q = dns.message.make_query(
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zone_origin,
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rdtype,
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rdclass,
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use_edns,
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False,
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ednsflags,
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payload,
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request_payload,
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options,
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)
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if serial is not None:
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rdata = dns.rdata.from_text(rdclass, "SOA", f". . {serial} 0 0 0 0")
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rrset = q.find_rrset(
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q.authority, zone_origin, rdclass, dns.rdatatype.SOA, create=True
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)
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rrset.add(rdata, 0)
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if keyring is not None:
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q.use_tsig(keyring, keyname, algorithm=keyalgorithm)
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return (q, serial)
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def extract_serial_from_query(query: dns.message.Message) -> Optional[int]:
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"""Extract the SOA serial number from query if it is an IXFR and return
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it, otherwise return None.
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*query* is a dns.message.QueryMessage that is an IXFR or AXFR request.
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Raises if the query is not an IXFR or AXFR, or if an IXFR doesn't have
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an appropriate SOA RRset in the authority section.
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"""
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if not isinstance(query, dns.message.QueryMessage):
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raise ValueError("query not a QueryMessage")
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question = query.question[0]
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if question.rdtype == dns.rdatatype.AXFR:
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return None
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elif question.rdtype != dns.rdatatype.IXFR:
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raise ValueError("query is not an AXFR or IXFR")
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soa = query.find_rrset(
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query.authority, question.name, question.rdclass, dns.rdatatype.SOA
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)
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return soa[0].serial
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