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# SPDX-License-Identifier: GPL-3.0-or-later
# Base defintions for policies for altering HTTP requests.
#
# This file is part of Hydrilla&Haketilo.
#
# Copyright (C) 2022 Wojtek Kosior
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
#
#
# I, Wojtek Kosior, thereby promise not to sue for violation of this
# file's license. Although I request that you do not make use of this
# code in a proprietary program, I am not going to enforce this in
# court.
"""
.....
"""
import dataclasses as dc
import typing as t
import enum
from abc import ABC, abstractmethod
from immutables import Map
from ... url_patterns import ParsedUrl
from .. import state
from .. import http_messages
from .. import csp
class PolicyPriority(int, enum.Enum):
"""...."""
_ONE = 1
_TWO = 2
_THREE = 3
MessageInfo = t.Union[
http_messages.RequestInfo,
http_messages.ResponseInfo
]
UTF8_BOM = b'\xEF\xBB\xBF'
BOMs = (
(UTF8_BOM, 'utf-8'),
(b'\xFE\xFF', 'utf-16be'),
(b'\xFF\xFE', 'utf-16le')
)
class Policy(ABC):
"""...."""
_process_request: t.ClassVar[bool] = False
_process_response: t.ClassVar[bool] = False
anticache: t.ClassVar[bool] = True
priority: t.ClassVar[PolicyPriority]
def should_process_request(
self,
request_info: http_messages.BodylessRequestInfo
) -> bool:
return self._process_request
def should_process_response(
self,
request_info: http_messages.RequestInfo,
response_info: http_messages.AnyResponseInfo
) -> bool:
return self._process_response
def _csp_to_clear(self, http_info: http_messages.FullHTTPInfo) \
-> t.Union[t.Sequence[str], t.Literal['all']]:
return ()
def _csp_to_add(self, http_info: http_messages.FullHTTPInfo) \
-> t.Mapping[str, t.Sequence[str]]:
return Map()
def _csp_to_extend(self, http_info: http_messages.FullHTTPInfo) \
-> t.Mapping[str, t.Sequence[str]]:
return Map()
def _modify_response_headers(self, http_info: http_messages.FullHTTPInfo) \
-> http_messages.IHeaders:
csp_to_clear = self._csp_to_clear(http_info)
csp_to_add = self._csp_to_add(http_info)
csp_to_extend = self._csp_to_extend(http_info)
if len(csp_to_clear) + len(csp_to_extend) + len(csp_to_add) == 0:
return http_info.response_info.headers
return csp.modify(
headers = http_info.response_info.headers,
clear = csp_to_clear,
add = csp_to_add,
extend = csp_to_extend
)
def _modify_response_document(
self,
http_info: http_messages.FullHTTPInfo,
encoding: t.Optional[str]
) -> t.Union[str, bytes]:
return http_info.response_info.body
def _modify_response_body(self, http_info: http_messages.FullHTTPInfo) \
-> bytes:
if not http_messages.is_likely_a_page(
request_info = http_info.request_info,
response_info = http_info.response_info
):
return http_info.response_info.body
data = http_info.response_info.body
_, encoding = http_info.response_info.deduce_content_type()
# A UTF BOM overrides encoding specified by the header.
for bom, encoding_name in BOMs:
if data.startswith(bom):
encoding = encoding_name
new_data = self._modify_response_document(http_info, encoding)
if isinstance(new_data, str):
# Appending a three-byte Byte Order Mark (BOM) will force the
# browser to decode this as UTF-8 regardless of the 'Content-Type'
# header. See
# https://www.w3.org/International/tests/repository/html5/the-input-byte-stream/results-basics#precedence
new_data = UTF8_BOM + new_data.encode()
return new_data
def consume_request(self, request_info: http_messages.RequestInfo) \
-> t.Optional[MessageInfo]:
# We're not using @abstractmethod because not every Policy needs it and
# we don't want to force child classes into implementing dummy methods.
raise NotImplementedError(
'This kind of policy does not consume requests.'
)
def consume_response(self, http_info: http_messages.FullHTTPInfo) \
-> t.Optional[http_messages.ResponseInfo]:
try:
new_headers = self._modify_response_headers(http_info)
new_body = self._modify_response_body(http_info)
except Exception as e:
# In the future we might want to actually describe eventual errors.
# For now, we're just printing the stack trace.
import traceback
error_info_list = traceback.format_exception(
type(e),
e,
e.__traceback__
)
return http_messages.ResponseInfo.make(
status_code = 500,
headers = (('Content-Type', 'text/plain; charset=utf-8'),),
body = '\n'.join(error_info_list).encode()
)
if (new_headers is http_info.response_info.headers and
new_body is http_info.response_info.body):
return None
return dc.replace(
http_info.response_info,
headers = new_headers,
body = new_body
)
# mypy needs to be corrected:
# https://stackoverflow.com/questions/70999513/conflict-between-mix-ins-for-abstract-dataclasses/70999704#70999704
@dc.dataclass(frozen=True, unsafe_hash=True) # type: ignore[misc]
class PolicyFactory(ABC):
"""...."""
builtin: bool
@abstractmethod
def make_policy(self, haketilo_state: state.HaketiloState) \
-> t.Optional[Policy]:
"""...."""
...
def __lt__(self, other: 'PolicyFactory'):
"""...."""
return sorting_keys.get(self.__class__.__name__, 999) < \
sorting_keys.get(other.__class__.__name__, 999)
sorting_order = (
'WebUIMainPolicyFactory',
'WebUILandingPolicyFactory',
'MitmItPagePolicyFactory',
'PayloadResourcePolicyFactory',
'PayloadPolicyFactory',
'RuleBlockPolicyFactory',
'RuleAllowPolicyFactory',
'FallbackPolicyFactory'
)
sorting_keys = Map((cls, name) for name, cls in enumerate(sorting_order))
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