# 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 binascii
import math
import socket
import struct
from typing import Any, Dict, Optional, Union
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
[docs]
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)
[docs]
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
def to_text(self) -> str:
raise NotImplementedError # pragma: no cover
[docs]
@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()
[docs]
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)
[docs]
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
[docs]
@classmethod
def from_wire_parser(
cls, otype: Union[OptionType, str], parser: "dns.wire.Parser"
) -> Option:
return cls(otype, parser.get_remaining())
[docs]
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)
[docs]
@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)
[docs]
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
[docs]
@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)"""
_preserve_case = {"DNSKEY", "DS", "DNSSEC", "RRSIGs", "NSEC", "NXDOMAIN"}
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.code in EDECode:
desc = EDECode.to_text(self.code)
desc = " ".join(
word if word in self._preserve_case else word.title()
for word in desc.split("_")
)
output += f" ({desc})"
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:
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(code, btext)
class NSIDOption(Option):
def __init__(self, nsid: bytes):
super().__init__(OptionType.NSID)
self.nsid = nsid
def to_wire(self, file: Any = None) -> Optional[bytes]:
if file:
file.write(self.nsid)
return None
else:
return self.nsid
def to_text(self) -> str:
if all(c >= 0x20 and c <= 0x7E for c in self.nsid):
# All ASCII printable, so it's probably a string.
value = self.nsid.decode()
else:
value = binascii.hexlify(self.nsid).decode()
return f"NSID {value}"
@classmethod
def from_wire_parser(
cls, otype: Union[OptionType, str], parser: dns.wire.Parser
) -> Option:
return cls(parser.get_remaining())
_type_to_class: Dict[OptionType, Any] = {
OptionType.ECS: ECSOption,
OptionType.EDE: EDEOption,
OptionType.NSID: NSIDOption,
}
[docs]
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
[docs]
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``.
"""
otype = OptionType.make(otype)
cls = get_option_class(otype)
return cls.from_wire_parser(otype, parser)
[docs]
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)
[docs]
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