aboutsummaryrefslogtreecommitdiff
path: root/src/hydrilla/proxy/policies/base.py
blob: 1626b5c3d0c518f76509c924ec7af05ef0c13cc1 (about) (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
# 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 enum
import re
import threading
import dataclasses as dc
import typing as t

from abc import ABC, abstractmethod
from hashlib import sha256
from base64 import b64encode

import jinja2

from immutables import Map

from ...translations import translation as make_translation
from ... import url_patterns
from ... import common_jinja_templates
from .. import state
from .. import http_messages
from .. import csp


_info_loader = jinja2.PackageLoader(
    __package__,
    package_path = 'info_pages_templates'
)
_combined_loader = common_jinja_templates.combine_with_loaders([_info_loader])
_jinja_info_env = jinja2.Environment(
    loader        = _combined_loader,
    autoescape    = jinja2.select_autoescape(['html.jinja']),
    lstrip_blocks = True,
    extensions    = ['jinja2.ext.i18n', 'jinja2.ext.do']
)
_jinja_info_env.install_gettext_translations(make_translation()) # type: ignore
_jinja_info_env.globals['url_patterns'] = url_patterns
_jinja_info_lock = threading.Lock()

def get_info_template(template_file_name: str) -> jinja2.Template:
    with _jinja_info_lock:
        return _jinja_info_env.get_template(template_file_name)


_jinja_script_loader = jinja2.PackageLoader(
    __package__,
    package_path = 'injectable_scripts'
)
_jinja_script_env = jinja2.Environment(
    loader        = _jinja_script_loader,
    autoescape    = False,
    lstrip_blocks = True,
    extensions    = ['jinja2.ext.do']
)
_jinja_script_lock = threading.Lock()

def get_script_template(template_file_name: str) -> jinja2.Template:
    with _jinja_script_lock:
        return _jinja_script_env.get_template(template_file_name)


response_work_data = threading.local()

def response_nonce() -> str:
    """
    When called multiple times during consume_response(), each time returns the
    same unpredictable string unique to this response. The string is used as a
    nonce for script elements.
    """
    return response_work_data.nonce


class PolicyPriority(int, enum.Enum):
    """...."""
    _ONE   = 1
    _TWO   = 2
    _THREE = 3


class MsgProcessOpt(enum.Enum):
    """...."""
    MUST     = True
    MUST_NOT = False


MessageInfo = t.Union[
    http_messages.RequestInfo,
    http_messages.ResponseInfo
]


# We're doing *very* simple doctype matching for now. If a site wanted, it could
# trick us into getting this wrong.
doctype_re = re.compile(r'^\s*<!doctype[^>]*>', re.IGNORECASE)


UTF8_BOM = b'\xEF\xBB\xBF'
BOMs = (
    (UTF8_BOM,    'utf-8'),
    (b'\xFE\xFF', 'utf-16be'),
    (b'\xFF\xFE', 'utf-16le')
)


# mypy needs to be corrected:
# https://stackoverflow.com/questions/70999513/conflict-between-mix-ins-for-abstract-dataclasses/70999704#70999704
@dc.dataclass(frozen=True) # type: ignore[misc]
class Policy(ABC):
    _process_request:  t.ClassVar[t.Optional[MsgProcessOpt]] = None
    _process_response: t.ClassVar[t.Optional[MsgProcessOpt]] = None
    anticache:         t.ClassVar[bool] = True

    priority: t.ClassVar[PolicyPriority]

    haketilo_settings: state.HaketiloGlobalSettings

    @property
    def current_popup_settings(self) -> state.PopupSettings:
        return self.haketilo_settings.default_popup_jsallowed

    def should_process_request(
            self,
            request_info: http_messages.BodylessRequestInfo
    ) -> bool:
        return self._process_request == MsgProcessOpt.MUST

    def should_process_response(
            self,
            request_info:  http_messages.RequestInfo,
            response_info: http_messages.AnyResponseInfo
    ) -> bool:
        if self._process_response is not None:
            return self._process_response.value

        return (self.current_popup_settings.popup_enabled and
                http_messages.is_likely_a_page(request_info, response_info))

    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]]:
        if (self.current_popup_settings.popup_enabled and
            http_info.is_likely_a_page):
            nonce_source = f"'nonce-{response_nonce()}'"
            directives = ('script-src', 'style-src', 'frame-src')
            return dict((directive, [nonce_source]) for directive in directives)
        else:
            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]:
        popup_settings = self.current_popup_settings

        if popup_settings.popup_enabled:
            nonce = response_nonce()

            popup_page = self.make_info_page(http_info)
            if popup_page is None:
                template = get_info_template('special_page_info.html.jinja')
                popup_page = template.render(
                    url = http_info.request_info.url.orig_url
                )

            template = get_script_template('popup.js.jinja')
            popup_script = template.render(
                popup_page_b64 = b64encode(popup_page.encode()).decode(),
                nonce_b64      = b64encode(nonce.encode()).decode(),
                # TODO: add an option to configure popup style in the web UI.
                # Then start passing the real style value.
                #popup_style    = popup_settings.style.value
                popup_style    = 'D'
            )

            if encoding is None:
                encoding = 'utf-8'

            body_bytes = http_info.response_info.body
            body = body_bytes.decode(encoding, errors='replace')

            match = doctype_re.match(body)
            doctype_decl_len = 0 if match is None else match.end()

            dotype_decl = body[0:doctype_decl_len]
            doc_rest = body[doctype_decl_len:]
            script_tag = f'<script nonce="{nonce}">{popup_script}</script>'

            return dotype_decl + script_tag + doc_rest
        else:
            return http_info.response_info.body

    def _modify_response_body(self, http_info: http_messages.FullHTTPInfo) \
        -> bytes:
        if not http_info.is_likely_a_page:
            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
        )

    def make_info_page(self, http_info: http_messages.FullHTTPInfo) \
        -> t.Optional[str]:
        return None


@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))