# 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""" from __future__ import absolute_import import math import struct import dns.inet #: 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 class Option(object): """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): """Convert an option to wire format. """ raise NotImplementedError @classmethod def from_wire(cls, otype, wire, current, olen): """Build an EDNS option object from wire format. *otype*, an ``int``, is the option type. *wire*, a ``binary``, 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 a ``dns.edns.Option``. """ raise NotImplementedError 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*. """ raise NotImplementedError 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 False if self.otype != other.otype: return False 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 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(GenericOption, self).__init__(otype) self.data = data def to_wire(self, file): file.write(self.data) def to_text(self): return "Generic %d" % self.otype @classmethod def from_wire(cls, otype, wire, current, olen): return cls(otype, wire[current: current + olen]) def _cmp(self, other): if self.data == other.data: return 0 if self.data > other.data: return 1 return -1 class ECSOption(Option): """EDNS Client Subnet (ECS, RFC7871)""" def __init__(self, address, srclen=None, scopelen=0): """*address*, a ``text``, 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(ECSOption, self).__init__(ECS) af = dns.inet.af_for_address(address) if af == dns.inet.AF_INET6: self.family = 2 if srclen is None: srclen = 56 elif af == dns.inet.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 << nbits)) self.addrdata = self.addrdata[:-1] + last def to_text(self): return "ECS {}/{} scope/{}".format(self.address, self.srclen, self.scopelen) def to_wire(self, file): file.write(struct.pack('!H', self.family)) file.write(struct.pack('!BB', self.srclen, self.scopelen)) file.write(self.addrdata) @classmethod def from_wire(cls, otype, wire, cur, olen): family, src, scope = struct.unpack('!HBB', wire[cur:cur+4]) cur += 4 addrlen = int(math.ceil(src/8.0)) if family == 1: af = dns.inet.AF_INET pad = 4 - addrlen elif family == 2: af = dns.inet.AF_INET6 pad = 16 - addrlen else: raise ValueError('unsupported family') addr = dns.inet.inet_ntop(af, wire[cur:cur+addrlen] + b'\x00' * pad) return cls(addr, src, scope) def _cmp(self, other): if self.addrdata == other.addrdata: return 0 if self.addrdata > other.addrdata: return 1 return -1 _type_to_class = { 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(otype, wire, current, olen): """Build an EDNS option object from wire format. *otype*, an ``int``, is the option type. *wire*, a ``binary``, 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``. """ cls = get_option_class(otype) return cls.from_wire(otype, wire, current, olen)