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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""" from typing import Any, Dict, Optional, Union import math import socket import struct import dns.enum import dns.inet import dns.rdata import dns.wire 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 #: EDE (extended-dns-error) EDE = 15 @classmethod def _maximum(cls): return 65535 class Option: """Base class for all EDNS option types.""" def __init__(self, otype: Union[OptionType, str]): """Initialize an option. *otype*, a ``dns.edns.OptionType``, is the option type. """ self.otype = OptionType.make(otype) def to_wire(self, file: Optional[Any] = None) -> Optional[bytes]: """Convert an option to wire format. Returns a ``bytes`` or ``None``. """ raise NotImplementedError # pragma: no cover @classmethod def from_wire_parser(cls, otype: OptionType, parser: "dns.wire.Parser") -> "Option": """Build an EDNS option object from wire format. *otype*, a ``dns.edns.OptionType``, 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): # lgtm[py/missing-equals] """Generic Option Class This class is used for EDNS option types for which we have no better implementation. """ def __init__(self, otype: Union[OptionType, str], data: Union[bytes, str]): super().__init__(otype) self.data = dns.rdata.Rdata._as_bytes(data, True) def to_wire(self, file: Optional[Any] = None) -> Optional[bytes]: if file: file.write(self.data) return None else: return self.data def to_text(self) -> str: return "Generic %d" % self.otype @classmethod def from_wire_parser( cls, otype: Union[OptionType, str], parser: "dns.wire.Parser" ) -> Option: return cls(otype, parser.get_remaining()) class ECSOption(Option): # lgtm[py/missing-equals] """EDNS Client Subnet (ECS, RFC7871)""" def __init__(self, address: str, srclen: Optional[int] = None, scopelen: int = 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 address = dns.rdata.Rdata._as_ipv6_address(address) srclen = dns.rdata.Rdata._as_int(srclen, 0, 128) scopelen = dns.rdata.Rdata._as_int(scopelen, 0, 128) elif af == socket.AF_INET: self.family = 1 if srclen is None: srclen = 24 address = dns.rdata.Rdata._as_ipv4_address(address) srclen = dns.rdata.Rdata._as_int(srclen, 0, 32) scopelen = dns.rdata.Rdata._as_int(scopelen, 0, 32) else: # pragma: no cover (this will never happen) raise ValueError("Bad address family") assert srclen is not None 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) -> str: return "ECS {}/{} scope/{}".format(self.address, self.srclen, self.scopelen) @staticmethod def from_text(text: str) -> Option: """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, tsrclen = ecs_text.split("/") tscope = "0" elif n_slashes == 2: address, tsrclen, tscope = ecs_text.split("/") else: raise ValueError('could not parse ECS from "{}"'.format(text)) try: scope = int(tscope) except ValueError: raise ValueError( "invalid scope " + '"{}": scope must be an integer'.format(tscope) ) try: srclen = int(tsrclen) except ValueError: raise ValueError( "invalid srclen " + '"{}": srclen must be an integer'.format(tsrclen) ) return ECSOption(address, srclen, scope) def to_wire(self, file: Optional[Any] = None) -> Optional[bytes]: value = ( struct.pack("!HBB", self.family, self.srclen, self.scopelen) + self.addrdata ) if file: file.write(value) return None else: return value @classmethod def from_wire_parser( cls, otype: Union[OptionType, str], parser: "dns.wire.Parser" ) -> Option: 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) class EDECode(dns.enum.IntEnum): OTHER = 0 UNSUPPORTED_DNSKEY_ALGORITHM = 1 UNSUPPORTED_DS_DIGEST_TYPE = 2 STALE_ANSWER = 3 FORGED_ANSWER = 4 DNSSEC_INDETERMINATE = 5 DNSSEC_BOGUS = 6 SIGNATURE_EXPIRED = 7 SIGNATURE_NOT_YET_VALID = 8 DNSKEY_MISSING = 9 RRSIGS_MISSING = 10 NO_ZONE_KEY_BIT_SET = 11 NSEC_MISSING = 12 CACHED_ERROR = 13 NOT_READY = 14 BLOCKED = 15 CENSORED = 16 FILTERED = 17 PROHIBITED = 18 STALE_NXDOMAIN_ANSWER = 19 NOT_AUTHORITATIVE = 20 NOT_SUPPORTED = 21 NO_REACHABLE_AUTHORITY = 22 NETWORK_ERROR = 23 INVALID_DATA = 24 @classmethod def _maximum(cls): return 65535 class EDEOption(Option): # lgtm[py/missing-equals] """Extended DNS Error (EDE, RFC8914)""" def __init__(self, code: Union[EDECode, str], text: Optional[str] = None): """*code*, a ``dns.edns.EDECode`` or ``str``, the info code of the extended error. *text*, a ``str`` or ``None``, specifying additional information about the error. """ super().__init__(OptionType.EDE) self.code = EDECode.make(code) if text is not None and not isinstance(text, str): raise ValueError("text must be string or None") self.text = text def to_text(self) -> str: output = f"EDE {self.code}" if self.text is not None: output += f": {self.text}" return output def to_wire(self, file: Optional[Any] = None) -> Optional[bytes]: value = struct.pack("!H", self.code) if self.text is not None: value += self.text.encode("utf8") if file: file.write(value) return None else: return value @classmethod def from_wire_parser( cls, otype: Union[OptionType, str], parser: "dns.wire.Parser" ) -> Option: the_code = EDECode.make(parser.get_uint16()) text = parser.get_remaining() if text: if text[-1] == 0: # text MAY be null-terminated text = text[:-1] btext = text.decode("utf8") else: btext = None return cls(the_code, btext) _type_to_class: Dict[OptionType, Any] = { OptionType.ECS: ECSOption, OptionType.EDE: EDEOption, } def get_option_class(otype: OptionType) -> Any: """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: Union[OptionType, str], parser: "dns.wire.Parser" ) -> Option: """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``. """ the_otype = OptionType.make(otype) cls = get_option_class(the_otype) return cls.from_wire_parser(otype, parser) def option_from_wire( otype: Union[OptionType, str], wire: bytes, current: int, olen: int ) -> Option: """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) def register_type(implementation: Any, otype: OptionType) -> None: """Register the implementation of an option type. *implementation*, a ``class``, is a subclass of ``dns.edns.Option``. *otype*, an ``int``, is the option type. """ _type_to_class[otype] = implementation ### BEGIN generated OptionType constants NSID = OptionType.NSID DAU = OptionType.DAU DHU = OptionType.DHU N3U = OptionType.N3U ECS = OptionType.ECS EXPIRE = OptionType.EXPIRE COOKIE = OptionType.COOKIE KEEPALIVE = OptionType.KEEPALIVE PADDING = OptionType.PADDING CHAIN = OptionType.CHAIN EDE = OptionType.EDE ### END generated OptionType constants