unfinished partial work

1 files changed, 125 insertions, 0 deletions

diff --git a/src/hydrilla/proxy/csp.py b/src/hydrilla/proxy/csp.py
new file mode 100644
index 0000000..59d93f2
--- /dev/null
+++ b/src/hydrilla/proxy/csp.py
@@ -0,0 +1,125 @@
+# 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)