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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 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 .policies.base import IHeaders
+
+
+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: 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)