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# SPDX-License-Identifier: GPL-3.0-or-later
# Tools for working with Content Security Policy headers.
#
# 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.
"""
.....
"""
# Enable using with Python 3.7.
from __future__ import annotations
import re
import typing as t
import dataclasses as dc
from immutables import Map, MapMutation
from . import http_messages
header_names_and_dispositions = (
('content-security-policy', 'enforce'),
('content-security-policy-report-only', 'report'),
('x-content-security-policy', 'enforce'),
('x-content-security-policy', 'report'),
('x-webkit-csp', 'enforce'),
('x-webkit-csp', 'report')
)
enforce_header_names_set = {
name for name, disposition in header_names_and_dispositions
if disposition == 'enforce'
}
@dc.dataclass
class ContentSecurityPolicy:
directives: Map[str, t.Sequence[str]]
header_name: str
disposition: str
def serialize(self) -> str:
"""...."""
serialized_directives = []
for name, value_list in self.directives.items():
serialized_directives.append(f'{name} {" ".join(value_list)}')
return ';'.join(serialized_directives)
@staticmethod
def deserialize(
serialized: str,
header_name: str,
disposition: str = 'enforce'
) -> 'ContentSecurityPolicy':
"""...."""
# For more info, see:
# https://www.w3.org/TR/CSP3/#parse-serialized-policy
empty_directives: Map[str, t.Sequence[str]] = Map()
directives = empty_directives.mutate()
for serialized_directive in serialized.split(';'):
if not serialized_directive.isascii():
continue
serialized_directive = serialized_directive.strip()
if len(serialized_directive) == 0:
continue
tokens = serialized_directive.split()
directive_name = tokens.pop(0).lower()
directive_value = tokens
# Specs mention giving warnings for duplicate directive names but
# from our proxy's perspective this is not important right now.
if directive_name in directives:
continue
directives[directive_name] = directive_value
return ContentSecurityPolicy(
directives = directives.finish(),
header_name = header_name,
disposition = disposition
)
def extract(headers: http_messages.IHeaders) \
-> tuple[ContentSecurityPolicy, ...]:
"""...."""
csp_policies = []
for header_name, disposition in header_names_and_dispositions:
for serialized_list in headers.get_all(header_name):
for serialized in serialized_list.split(','):
policy = ContentSecurityPolicy.deserialize(
serialized,
header_name,
disposition
)
if policy.directives != Map():
csp_policies.append(policy)
return tuple(csp_policies)
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