205 lines
7.5 KiB
Python
205 lines
7.5 KiB
Python
# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import hmac
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import logging
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from hashlib import sha256
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from http import HTTPStatus
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from os import path
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from typing import TYPE_CHECKING, Any, Dict, List
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import jinja2
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from jinja2 import TemplateNotFound
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from twisted.web.server import Request
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from synapse.api.errors import NotFoundError, StoreError, SynapseError
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from synapse.config import ConfigError
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from synapse.http.server import DirectServeHtmlResource, respond_with_html
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from synapse.http.servlet import parse_bytes_from_args, parse_string
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from synapse.types import UserID
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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# language to use for the templates. TODO: figure this out from Accept-Language
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TEMPLATE_LANGUAGE = "en"
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logger = logging.getLogger(__name__)
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class ConsentResource(DirectServeHtmlResource):
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"""A twisted Resource to display a privacy policy and gather consent to it
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When accessed via GET, returns the privacy policy via a template.
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When accessed via POST, records the user's consent in the database and
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displays a success page.
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The config should include a template_dir setting which contains templates
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for the HTML. The directory should contain one subdirectory per language
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(eg, 'en', 'fr'), and each language directory should contain the policy
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document (named as '<version>.html') and a success page (success.html).
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Both forms take a set of parameters from the browser. For the POST form,
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these are normally sent as form parameters (but may be query-params); for
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GET requests they must be query params. These are:
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u: the complete mxid, or the localpart of the user giving their
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consent. Required for both GET (where it is used as an input to the
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template) and for POST (where it is used to find the row in the db
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to update).
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h: hmac_sha256(secret, u), where 'secret' is the privacy_secret in the
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config file. If it doesn't match, the request is 403ed.
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v: the version of the privacy policy being agreed to.
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For GET: optional, and defaults to whatever was set in the config
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file. Used to choose the version of the policy to pick from the
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templates directory.
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For POST: required; gives the value to be recorded in the database
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against the user.
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"""
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def __init__(self, hs: "HomeServer"):
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super().__init__()
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self.hs = hs
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self.store = hs.get_datastores().main
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self.registration_handler = hs.get_registration_handler()
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# this is required by the request_handler wrapper
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self.clock = hs.get_clock()
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# Consent must be configured to create this resource.
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default_consent_version = hs.config.consent.user_consent_version
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consent_template_directory = hs.config.consent.user_consent_template_dir
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if default_consent_version is None or consent_template_directory is None:
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raise ConfigError(
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"Consent resource is enabled but user_consent section is "
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"missing in config file."
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)
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self._default_consent_version = default_consent_version
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# TODO: switch to synapse.util.templates.build_jinja_env
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loader = jinja2.FileSystemLoader(consent_template_directory)
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self._jinja_env = jinja2.Environment(
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loader=loader, autoescape=jinja2.select_autoescape(["html", "htm", "xml"])
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)
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if hs.config.key.form_secret is None:
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raise ConfigError(
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"Consent resource is enabled but form_secret is not set in "
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"config file. It should be set to an arbitrary secret string."
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)
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self._hmac_secret = hs.config.key.form_secret.encode("utf-8")
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async def _async_render_GET(self, request: Request) -> None:
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version = parse_string(request, "v", default=self._default_consent_version)
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username = parse_string(request, "u", default="")
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userhmac = None
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has_consented = False
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public_version = username == ""
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if not public_version:
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args: Dict[bytes, List[bytes]] = request.args # type: ignore
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userhmac_bytes = parse_bytes_from_args(args, "h", required=True)
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self._check_hash(username, userhmac_bytes)
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if username.startswith("@"):
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qualified_user_id = username
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else:
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qualified_user_id = UserID(username, self.hs.hostname).to_string()
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u = await self.store.get_user_by_id(qualified_user_id)
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if u is None:
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raise NotFoundError("Unknown user")
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has_consented = u.consent_version == version
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userhmac = userhmac_bytes.decode("ascii")
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try:
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self._render_template(
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request,
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"%s.html" % (version,),
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user=username,
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userhmac=userhmac,
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version=version,
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has_consented=has_consented,
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public_version=public_version,
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)
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except TemplateNotFound:
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raise NotFoundError("Unknown policy version")
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async def _async_render_POST(self, request: Request) -> None:
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version = parse_string(request, "v", required=True)
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username = parse_string(request, "u", required=True)
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args: Dict[bytes, List[bytes]] = request.args # type: ignore
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userhmac = parse_bytes_from_args(args, "h", required=True)
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self._check_hash(username, userhmac)
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if username.startswith("@"):
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qualified_user_id = username
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else:
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qualified_user_id = UserID(username, self.hs.hostname).to_string()
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try:
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await self.store.user_set_consent_version(qualified_user_id, version)
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except StoreError as e:
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if e.code != 404:
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raise
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raise NotFoundError("Unknown user")
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await self.registration_handler.post_consent_actions(qualified_user_id)
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try:
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self._render_template(request, "success.html")
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except TemplateNotFound:
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raise NotFoundError("success.html not found")
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def _render_template(
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self, request: Request, template_name: str, **template_args: Any
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) -> None:
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# get_template checks for ".." so we don't need to worry too much
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# about path traversal here.
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template_html = self._jinja_env.get_template(
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path.join(TEMPLATE_LANGUAGE, template_name)
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)
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html = template_html.render(**template_args)
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respond_with_html(request, 200, html)
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def _check_hash(self, userid: str, userhmac: bytes) -> None:
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"""
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Args:
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userid:
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userhmac:
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Raises:
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SynapseError if the hash doesn't match
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"""
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want_mac = (
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hmac.new(
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key=self._hmac_secret, msg=userid.encode("utf-8"), digestmod=sha256
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)
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.hexdigest()
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.encode("ascii")
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)
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if not hmac.compare_digest(want_mac, userhmac):
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raise SynapseError(HTTPStatus.FORBIDDEN, "HMAC incorrect")
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