✏️ Editing: edns.py Read Only

# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license

# Copyright (C) 2009-2017 Nominum, Inc.
#
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# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# 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

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

def to_text(self) -> str:
        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)"""

_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,
}

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``.
    """
    otype = OptionType.make(otype)
    cls = get_option_class(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

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