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# SPDX-FileCopyrightText: 2024 Greenbone AG
#
# SPDX-License-Identifier: GPL-3.0-or-later
from typing import AnyStr, Optional, Protocol
from lxml import etree
from gvm.errors import GvmError
from ._request import Request
from ._response import Response
class XmlReader:
"""
Read a XML command until its closing element
"""
def start_xml(self) -> None:
self._first_element: Optional[etree._Element] = None
# act on start and end element events and
# allow huge text data (for report content)
self._parser = etree.XMLPullParser(
events=("start", "end"), huge_tree=True
)
def is_end_xml(self) -> bool:
for action, obj in self._parser.read_events():
if not self._first_element and action in "start":
self._first_element = obj.tag # type: ignore
if (
self._first_element
and action in "end"
and str(self._first_element) == str(obj.tag) # type: ignore
):
return True
return False
def feed_xml(self, data: AnyStr) -> None:
try:
self._parser.feed(data)
except etree.ParseError as e:
raise GvmError(
f"Cannot parse XML response. Response data read {data!r}",
e,
) from None
class InvalidStateError(GvmError):
"""
Error raised if the Connection would be moved into an invalid state
"""
def __init__(self, message: str = "Invalid State", *args):
super().__init__(message, *args)
class State(Protocol):
def __set_context__(self, context: "Context") -> None: ...
def send(self, request: Request) -> bytes: ...
def receive_data(self, data: bytes) -> Optional[Response]: ...
def close(self) -> None: ...
class Context(Protocol):
def __set_state__(self, state: State) -> None: ...
class AbstractState:
_context: Context
def __set_context__(self, context: Context) -> None:
self._context = context
def set_next_state(self, next_state: State) -> None:
self._context.__set_state__(next_state)
class InitialState(AbstractState):
def send(self, request: Request) -> bytes:
self.set_next_state(AwaitingResponseState(request))
return bytes(request)
def receive_data(self, data: bytes) -> Optional[Response]:
raise InvalidStateError()
def close(self) -> None:
# nothing to do
return
class AwaitingResponseState(AbstractState):
def __init__(self, request: Request) -> None:
self._request = request
def send(self, request: Request) -> bytes:
raise InvalidStateError()
def close(self) -> None:
self.set_next_state(InitialState())
def receive_data(self, data: bytes) -> Optional[Response]:
next_state = ReceivingDataState(self._request)
self.set_next_state(next_state)
return next_state.receive_data(data)
class ErrorState(AbstractState):
message = (
"The connection is in an error state. Please close the connection."
)
def send(self, request: Request) -> bytes:
raise InvalidStateError(self.message)
def close(self) -> None:
self.set_next_state(InitialState())
def receive_data(self, data: bytes) -> Optional[Response]:
raise InvalidStateError(self.message)
class ReceivingDataState(AbstractState):
def __init__(self, request: Request) -> None:
self._request = request
self._data = bytearray()
self._reader = XmlReader()
self._reader.start_xml()
def send(self, request: Request) -> bytes:
raise InvalidStateError()
def close(self) -> None:
self.set_next_state(InitialState())
def receive_data(self, data: bytes) -> Optional[Response]:
self._data += data
try:
self._reader.feed_xml(data)
except GvmError as e:
self.set_next_state(ErrorState())
raise e
if not self._reader.is_end_xml():
return None
self.set_next_state(InitialState())
return Response(data=bytes(self._data), request=self._request)
class Connection:
"""
This is a [SansIO](https://sans-io.readthedocs.io) connection for GMP
It is responsible for creating bytes from GMP XML requests and transforming
XML response data into GMP responses.
"""
def __init__(self) -> None:
self.__set_state__(InitialState())
def send(self, request: Request) -> bytes:
"""
Create data from a request to be send
Returns:
The data for a request that can be send for example over a socket
Raises:
An InvalidStateError if no request can be send currently. For
example when waiting for a response to a previous request.
"""
return self._state.send(request)
def receive_data(self, data: bytes) -> Optional[Response]:
"""
Feed received data a response is complete
Returns:
A Response if the response data is complete and None if data is
still to be received.
Raises:
An InvalidStateError if no data can be received currently. For
example if no request is send yet.
"""
return self._state.receive_data(data)
def close(self) -> None:
"""
Close the connection and reset the state of the protocol
Afterwards the connection can be reused for sending a new request.
"""
return self._state.close()
def __set_state__(self, state: State) -> None:
self._state = state
self._state.__set_context__(self)
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