223 lines
7.7 KiB
Python
223 lines
7.7 KiB
Python
# -*- coding: utf-8 -*-
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# 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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from hashlib import sha256
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import hmac
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import logging
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from os import path
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from six.moves import http_client
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import jinja2
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from jinja2 import TemplateNotFound
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from twisted.internet import defer
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from twisted.web.resource import Resource
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from twisted.web.server import NOT_DONE_YET
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from synapse.api.errors import NotFoundError, SynapseError, StoreError
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from synapse.config import ConfigError
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from synapse.http.server import (
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finish_request,
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wrap_html_request_handler,
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)
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from synapse.http.servlet import parse_string
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from synapse.types import UserID
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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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# use hmac.compare_digest if we have it (python 2.7.7), else just use equality
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if hasattr(hmac, "compare_digest"):
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compare_digest = hmac.compare_digest
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else:
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def compare_digest(a, b):
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return a == b
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class ConsentResource(Resource):
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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):
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"""
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Args:
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hs (synapse.server.HomeServer): homeserver
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"""
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Resource.__init__(self)
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self.hs = hs
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self.store = hs.get_datastore()
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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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self._default_consent_version = hs.config.user_consent_version
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if self._default_consent_version 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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# daemonize changes the cwd to /, so make the path absolute now.
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consent_template_directory = path.abspath(
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hs.config.user_consent_template_dir,
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)
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if not path.isdir(consent_template_directory):
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raise ConfigError(
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"Could not find template directory '%s'" % (
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consent_template_directory,
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),
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)
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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,
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autoescape=jinja2.select_autoescape(['html', 'htm', 'xml']),
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)
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if hs.config.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.form_secret.encode("utf-8")
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def render_GET(self, request):
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self._async_render_GET(request)
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return NOT_DONE_YET
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@wrap_html_request_handler
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@defer.inlineCallbacks
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def _async_render_GET(self, request):
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"""
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Args:
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request (twisted.web.http.Request):
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"""
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version = parse_string(request, "v",
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default=self._default_consent_version)
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username = parse_string(request, "u", required=True)
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userhmac = parse_string(request, "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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u = yield 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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try:
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self._render_template(
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request, "%s.html" % (version,),
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user=username, userhmac=userhmac, version=version,
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has_consented=(u["consent_version"] == version),
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)
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except TemplateNotFound:
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raise NotFoundError("Unknown policy version")
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def render_POST(self, request):
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self._async_render_POST(request)
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return NOT_DONE_YET
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@wrap_html_request_handler
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@defer.inlineCallbacks
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def _async_render_POST(self, request):
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"""
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Args:
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request (twisted.web.http.Request):
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"""
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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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userhmac = parse_string(request, "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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yield 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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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(self, request, template_name, **template_args):
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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_bytes = template_html.render(**template_args).encode("utf8")
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request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
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request.setHeader(b"Content-Length", b"%i" % len(html_bytes))
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request.write(html_bytes)
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finish_request(request)
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def _check_hash(self, userid, userhmac):
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want_mac = hmac.new(
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key=self._hmac_secret,
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msg=userid,
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digestmod=sha256,
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).hexdigest()
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if not compare_digest(want_mac, userhmac):
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raise SynapseError(http_client.FORBIDDEN, "HMAC incorrect")
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