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# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2009-2017 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.
"""EDNS Options"""
import math
import socket
import struct
import dns.enum
import dns.inet
class OptionType(dns.enum.IntEnum):
#: NSID
NSID = 3
#: DAU
DAU = 5
#: DHU
DHU = 6
#: N3U
N3U = 7
#: ECS (client-subnet)
ECS = 8
#: EXPIRE
EXPIRE = 9
#: COOKIE
COOKIE = 10
#: KEEPALIVE
KEEPALIVE = 11
#: PADDING
PADDING = 12
#: CHAIN
CHAIN = 13
@classmethod
def _maximum(cls):
return 65535
globals().update(OptionType.__members__)
class Option:
"""Base class for all EDNS option types."""
def __init__(self, otype):
"""Initialize an option.
*otype*, an ``int``, is the option type.
"""
self.otype = otype
def to_wire(self, file=None):
"""Convert an option to wire format.
Returns a ``bytes`` or ``None``.
"""
raise NotImplementedError # pragma: no cover
@classmethod
def from_wire_parser(cls, otype, parser):
"""Build an EDNS option object from wire format.
*otype*, an ``int``, is the option type.
*parser*, a ``dns.wire.Parser``, the parser, which should be
restructed to the option length.
Returns a ``dns.edns.Option``.
"""
raise NotImplementedError # pragma: no cover
def _cmp(self, other):
"""Compare an EDNS option with another option of the same type.
Returns < 0 if < *other*, 0 if == *other*, and > 0 if > *other*.
"""
wire = self.to_wire()
owire = other.to_wire()
if wire == owire:
return 0
if wire > owire:
return 1
return -1
def __eq__(self, other):
if not isinstance(other, Option):
return False
if self.otype != other.otype:
return False
return self._cmp(other) == 0
def __ne__(self, other):
if not isinstance(other, Option):
return True
if self.otype != other.otype:
return True
return self._cmp(other) != 0
def __lt__(self, other):
if not isinstance(other, Option) or \
self.otype != other.otype:
return NotImplemented
return self._cmp(other) < 0
def __le__(self, other):
if not isinstance(other, Option) or \
self.otype != other.otype:
return NotImplemented
return self._cmp(other) <= 0
def __ge__(self, other):
if not isinstance(other, Option) or \
self.otype != other.otype:
return NotImplemented
return self._cmp(other) >= 0
def __gt__(self, other):
if not isinstance(other, Option) or \
self.otype != other.otype:
return NotImplemented
return self._cmp(other) > 0
def __str__(self):
return self.to_text()
class GenericOption(Option):
"""Generic Option Class
This class is used for EDNS option types for which we have no better
implementation.
"""
def __init__(self, otype, data):
super().__init__(otype)
self.data = data
def to_wire(self, file=None):
if file:
file.write(self.data)
else:
return self.data
def to_text(self):
return "Generic %d" % self.otype
@classmethod
def from_wire_parser(cls, otype, parser):
return cls(otype, parser.get_remaining())
class ECSOption(Option):
"""EDNS Client Subnet (ECS, RFC7871)"""
def __init__(self, address, srclen=None, scopelen=0):
"""*address*, a ``str``, is the client address information.
*srclen*, an ``int``, the source prefix length, which is the
leftmost number of bits of the address to be used for the
lookup. The default is 24 for IPv4 and 56 for IPv6.
*scopelen*, an ``int``, the scope prefix length. This value
must be 0 in queries, and should be set in responses.
"""
super().__init__(OptionType.ECS)
af = dns.inet.af_for_address(address)
if af == socket.AF_INET6:
self.family = 2
if srclen is None:
srclen = 56
elif af == socket.AF_INET:
self.family = 1
if srclen is None:
srclen = 24
else:
raise ValueError('Bad ip family')
self.address = address
self.srclen = srclen
self.scopelen = scopelen
addrdata = dns.inet.inet_pton(af, address)
nbytes = int(math.ceil(srclen / 8.0))
# Truncate to srclen and pad to the end of the last octet needed
# See RFC section 6
self.addrdata = addrdata[:nbytes]
nbits = srclen % 8
if nbits != 0:
last = struct.pack('B',
ord(self.addrdata[-1:]) & (0xff << (8 - nbits)))
self.addrdata = self.addrdata[:-1] + last
def to_text(self):
return "ECS {}/{} scope/{}".format(self.address, self.srclen,
self.scopelen)
@staticmethod
def from_text(text):
"""Convert a string into a `dns.edns.ECSOption`
*text*, a `str`, the text form of the option.
Returns a `dns.edns.ECSOption`.
Examples:
>>> import dns.edns
>>>
>>> # basic example
>>> dns.edns.ECSOption.from_text('1.2.3.4/24')
>>>
>>> # also understands scope
>>> dns.edns.ECSOption.from_text('1.2.3.4/24/32')
>>>
>>> # IPv6
>>> dns.edns.ECSOption.from_text('2001:4b98::1/64/64')
>>>
>>> # it understands results from `dns.edns.ECSOption.to_text()`
>>> dns.edns.ECSOption.from_text('ECS 1.2.3.4/24/32')
"""
optional_prefix = 'ECS'
tokens = text.split()
ecs_text = None
if len(tokens) == 1:
ecs_text = tokens[0]
elif len(tokens) == 2:
if tokens[0] != optional_prefix:
raise ValueError('could not parse ECS from "{}"'.format(text))
ecs_text = tokens[1]
else:
raise ValueError('could not parse ECS from "{}"'.format(text))
n_slashes = ecs_text.count('/')
if n_slashes == 1:
address, srclen = ecs_text.split('/')
scope = 0
elif n_slashes == 2:
address, srclen, scope = ecs_text.split('/')
else:
raise ValueError('could not parse ECS from "{}"'.format(text))
try:
scope = int(scope)
except ValueError:
raise ValueError('invalid scope ' +
'"{}": scope must be an integer'.format(scope))
try:
srclen = int(srclen)
except ValueError:
raise ValueError('invalid srclen ' +
'"{}": srclen must be an integer'.format(srclen))
return ECSOption(address, srclen, scope)
def to_wire(self, file=None):
value = (struct.pack('!HBB', self.family, self.srclen, self.scopelen) +
self.addrdata)
if file:
file.write(value)
else:
return value
@classmethod
def from_wire_parser(cls, otype, parser):
family, src, scope = parser.get_struct('!HBB')
addrlen = int(math.ceil(src / 8.0))
prefix = parser.get_bytes(addrlen)
if family == 1:
pad = 4 - addrlen
addr = dns.ipv4.inet_ntoa(prefix + b'\x00' * pad)
elif family == 2:
pad = 16 - addrlen
addr = dns.ipv6.inet_ntoa(prefix + b'\x00' * pad)
else:
raise ValueError('unsupported family')
return cls(addr, src, scope)
_type_to_class = {
OptionType.ECS: ECSOption
}
def get_option_class(otype):
"""Return the class for the specified option type.
The GenericOption class is used if a more specific class is not
known.
"""
cls = _type_to_class.get(otype)
if cls is None:
cls = GenericOption
return cls
def option_from_wire_parser(otype, parser):
"""Build an EDNS option object from wire format.
*otype*, an ``int``, is the option type.
*parser*, a ``dns.wire.Parser``, the parser, which should be
restricted to the option length.
Returns an instance of a subclass of ``dns.edns.Option``.
"""
cls = get_option_class(otype)
otype = OptionType.make(otype)
return cls.from_wire_parser(otype, parser)
def option_from_wire(otype, wire, current, olen):
"""Build an EDNS option object from wire format.
*otype*, an ``int``, is the option type.
*wire*, a ``bytes``, is the wire-format message.
*current*, an ``int``, is the offset in *wire* of the beginning
of the rdata.
*olen*, an ``int``, is the length of the wire-format option data
Returns an instance of a subclass of ``dns.edns.Option``.
"""
parser = dns.wire.Parser(wire, current)
with parser.restrict_to(olen):
return option_from_wire_parser(otype, parser)
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