# -*- coding: utf-8 -*- # 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 import jinja2 from jinja2 import TemplateNotFound 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_string from synapse.types import UserID # language to use for the templates. TODO: figure this out from Accept-Language TEMPLATE_LANGUAGE = "en" logger = logging.getLogger(__name__) # use hmac.compare_digest if we have it (python 2.7.7), else just use equality if hasattr(hmac, "compare_digest"): compare_digest = hmac.compare_digest else: def compare_digest(a, b): return a == b 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 '.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): """ Args: hs (synapse.server.HomeServer): homeserver """ super().__init__() self.hs = hs self.store = hs.get_datastore() self.registration_handler = hs.get_registration_handler() # this is required by the request_handler wrapper self.clock = hs.get_clock() self._default_consent_version = hs.config.user_consent_version if self._default_consent_version is None: raise ConfigError( "Consent resource is enabled but user_consent section is " "missing in config file." ) consent_template_directory = hs.config.user_consent_template_dir # 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.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.form_secret.encode("utf-8") async def _async_render_GET(self, request): """ Args: request (twisted.web.http.Request): """ version = parse_string(request, "v", default=self._default_consent_version) username = parse_string(request, "u", required=False, default="") userhmac = None has_consented = False public_version = username == "" if not public_version: userhmac_bytes = parse_string(request, "h", required=True, encoding=None) 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): """ Args: request (twisted.web.http.Request): """ version = parse_string(request, "v", required=True) username = parse_string(request, "u", required=True) userhmac = parse_string(request, "h", required=True, encoding=None) 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, template_name, **template_args): # 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, userhmac): """ Args: userid (unicode): userhmac (bytes): 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 compare_digest(want_mac, userhmac): raise SynapseError(HTTPStatus.FORBIDDEN, "HMAC incorrect")