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