Source code for pcapkit.protocols.internet.ah
# -*- coding: utf-8 -*-
"""AH - Authentication Header
================================
:mod:`pcapkit.protocols.internet.ah` contains
:class:`~pcapkit.protocols.internet.AH` only,
which implements extractor for Authentication
Header (AH) [*]_, whose structure is described
as below:
======= ========= ======================= ===================================
Octets Bits Name Description
======= ========= ======================= ===================================
0 0 ``ah.next`` Next Header
1 8 ``ah.length`` Payload Length
2 16 Reserved (must be zero)
4 32 ``sah.spi`` Security Parameters Index (SPI)
8 64 ``sah.seq`` Sequence Number Field
12 96 ``sah.icv`` Integrity Check Value (ICV)
======= ========= ======================= ===================================
.. [*] https://en.wikipedia.org/wiki/IPsec
"""
from typing import TYPE_CHECKING, overload
from pcapkit.const.reg.transtype import TransType as RegType_TransType
from pcapkit.protocols.data.internet.ah import AH as DataType_AH
from pcapkit.protocols.internet.ipsec import IPsec
from pcapkit.utilities.exceptions import ProtocolError, UnsupportedCall, VersionError
if TYPE_CHECKING:
from typing import Any, BinaryIO, NoReturn, Optional
from typing_extensions import Literal
from pcapkit.corekit.protochain import ProtoChain
from pcapkit.protocols.protocol import Protocol
__all__ = ['AH']
[docs]class AH(IPsec[DataType_AH]):
"""This class implements Authentication Header."""
##########################################################################
# Properties.
##########################################################################
@property
def name(self) -> 'Literal["Authentication Header"]':
"""Name of corresponding protocol."""
return 'Authentication Header'
@property
def length(self) -> 'int':
"""Header length of current protocol."""
return self._info.length
@property
def payload(self) -> 'Protocol | NoReturn':
"""Payload of current instance.
Raises:
UnsupportedCall: if the protocol is used as an IPv6 extension header
"""
if self._extf:
raise UnsupportedCall(f"'{self.__class__.__name__}' object has no attribute 'payload'")
return super().payload
@property
def protocol(self) -> 'Optional[str] | NoReturn':
"""Name of next layer protocol (if any).
Raises:
UnsupportedCall: if the protocol is used as an IPv6 extension header
"""
if self._extf:
raise UnsupportedCall(f"'{self.__class__.__name__}' object has no attribute 'protocol'")
return super().protocol
@property
def protochain(self) -> 'ProtoChain | NoReturn':
"""Protocol chain of current instance.
Raises:
UnsupportedCall: if the protocol is used as an IPv6 extension header
"""
if self._extf:
raise UnsupportedCall(f"'{self.__class__.__name__}' object has no attribute 'protochain'")
return super().protochain
##########################################################################
# Methods.
##########################################################################
[docs] def read(self, length: 'Optional[int]' = None, *, version: 'Literal[4, 6]' = 4, # pylint: disable=arguments-differ
extension: bool = False, **kwargs: 'Any') -> 'DataType_AH': # pylint: disable=unused-argument
"""Read Authentication Header.
Structure of AH header [:rfc:`4302`]:
.. code-block:: text
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Payload Len | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Parameters Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number Field |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Integrity Check Value-ICV (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Args:
length: Length of packet data.
version: IP protocol version.
extension: If the protocol is used as an IPv6 extension header.
**kwargs: Arbitrary keyword arguments.
Returns:
Parsed packet data.
"""
if length is None:
length = len(self)
_next = self._read_protos(1)
_plen = self._read_unpack(1)
_resv = self._read_fileng(2)
_scpi = self._read_unpack(4)
_dsnf = self._read_unpack(4)
# ICV length & value
_tlen = _plen * 4 - 2
_vlen = _tlen - 12
_chkv = self._read_fileng(_vlen)
ah = DataType_AH(
next=_next,
length=_tlen,
spi=_scpi,
seq=_dsnf,
icv=_chkv,
)
if version == 6:
_plen = 8 - (_tlen % 8)
elif version == 4:
_plen = 4 - (_tlen % 4)
else:
raise VersionError(f'Unknown IP version {version}')
if _plen: # explicit padding in need
padding = self._read_binary(_plen)
if int(padding, base=2) != 0: # check padding (all zero)
raise ProtocolError(f'{self.alias}: invalid format')
if extension:
return ah
return self._decode_next_layer(ah, _next, length - ah.length)
[docs] def make(self, **kwargs: 'Any') -> 'NoReturn':
"""Make (construct) packet data.
Args:
**kwargs: Arbitrary keyword arguments.
Returns:
Constructed packet data.
"""
raise NotImplementedError
[docs] @classmethod
def id(cls) -> 'tuple[Literal["AH"]]': # type: ignore[override]
"""Index ID of the protocol.
Returns:
Index ID of the protocol.
"""
return ('AH',)
##########################################################################
# Data models.
##########################################################################
@overload
def __post_init__(self, file: 'BinaryIO', length: 'Optional[int]' = ..., *, # pylint: disable=arguments-differ
version: 'Literal[4, 6]' = ..., extension: 'bool' = ...,
**kwargs: 'Any') -> 'None': ...
@overload
def __post_init__(self, **kwargs: 'Any') -> 'None': ... # pylint: disable=arguments-differ
[docs] def __post_init__(self, file: 'Optional[BinaryIO]' = None, length: 'Optional[int]' = None, *, # pylint: disable=arguments-differ
version: 'Literal[4, 6]' = 4, extension: 'bool' = False,
**kwargs: 'Any') -> 'None':
"""Post initialisation hook.
Args:
file: Source packet stream.
length: Length of packet data.
version: IP protocol version.
extension: If the protocol is used as an IPv6 extension header.
**kwargs: Arbitrary keyword arguments.
See Also:
For construction argument, please refer to :meth:`make`.
"""
#: bool: If the protocol is used as an IPv6 extension header.
self._extf = extension
# call super __post_init__
super().__post_init__(file, length, version=version, extension=extension, **kwargs) # type: ignore[arg-type]
def __length_hint__(self) -> 'Literal[20]':
"""Return an estimated length for the object."""
return 20
[docs] @classmethod
def __index__(cls) -> 'RegType_TransType': # pylint: disable=invalid-index-returned
"""Numeral registry index of the protocol.
Returns:
Numeral registry index of the protocol in `IANA`_.
.. _IANA: https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml
"""
return RegType_TransType.AH # type: ignore[return-value]
