diff --git a/synapse/rest/consent/__init__.py b/synapse/rest/consent/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/synapse/rest/consent/__init__.py
diff --git a/synapse/rest/consent/consent_resource.py b/synapse/rest/consent/consent_resource.py
new file mode 100644
index 0000000000..d791302278
--- /dev/null
+++ b/synapse/rest/consent/consent_resource.py
@@ -0,0 +1,210 @@
+# -*- 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.
+
+from hashlib import sha256
+import hmac
+import logging
+from os import path
+from six.moves import http_client
+
+import jinja2
+from jinja2 import TemplateNotFound
+from twisted.internet import defer
+from twisted.web.resource import Resource
+from twisted.web.server import NOT_DONE_YET
+
+from synapse.api.errors import NotFoundError, SynapseError, StoreError
+from synapse.config import ConfigError
+from synapse.http.server import (
+ finish_request,
+ wrap_html_request_handler,
+)
+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(Resource):
+ """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):
+ """
+ Args:
+ hs (synapse.server.HomeServer): homeserver
+ """
+ Resource.__init__(self)
+
+ self.hs = hs
+ self.store = hs.get_datastore()
+
+ # this is required by the request_handler wrapper
+ self.clock = hs.get_clock()
+
+ consent_config = hs.config.consent_config
+ if consent_config is None:
+ raise ConfigError(
+ "Consent resource is enabled but user_consent section is "
+ "missing in config file.",
+ )
+
+ # daemonize changes the cwd to /, so make the path absolute now.
+ consent_template_directory = path.abspath(
+ consent_config["template_dir"],
+ )
+ if not path.isdir(consent_template_directory):
+ raise ConfigError(
+ "Could not find template directory '%s'" % (
+ consent_template_directory,
+ ),
+ )
+
+ loader = jinja2.FileSystemLoader(consent_template_directory)
+ self._jinja_env = jinja2.Environment(loader=loader)
+
+ self._default_consent_verison = consent_config["default_version"]
+
+ 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")
+
+ def render_GET(self, request):
+ self._async_render_GET(request)
+ return NOT_DONE_YET
+
+ @wrap_html_request_handler
+ def _async_render_GET(self, request):
+ """
+ Args:
+ request (twisted.web.http.Request):
+ """
+
+ version = parse_string(request, "v",
+ default=self._default_consent_verison)
+ username = parse_string(request, "u", required=True)
+ userhmac = parse_string(request, "h", required=True)
+
+ self._check_hash(username, userhmac)
+
+ try:
+ self._render_template(
+ request, "%s.html" % (version,),
+ user=username, userhmac=userhmac, version=version,
+ )
+ except TemplateNotFound:
+ raise NotFoundError("Unknown policy version")
+
+ def render_POST(self, request):
+ self._async_render_POST(request)
+ return NOT_DONE_YET
+
+ @wrap_html_request_handler
+ @defer.inlineCallbacks
+ 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)
+
+ self._check_hash(username, userhmac)
+
+ if username.startswith('@'):
+ qualified_user_id = username
+ else:
+ qualified_user_id = UserID(username, self.hs.hostname).to_string()
+
+ try:
+ yield self.store.user_set_consent_version(qualified_user_id, version)
+ except StoreError as e:
+ if e.code != 404:
+ raise
+ raise NotFoundError("Unknown user")
+
+ 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_bytes = template_html.render(**template_args).encode("utf8")
+
+ request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+ request.setHeader(b"Content-Length", b"%i" % len(html_bytes))
+ request.write(html_bytes)
+ finish_request(request)
+
+ def _check_hash(self, userid, userhmac):
+ want_mac = hmac.new(
+ key=self._hmac_secret,
+ msg=userid,
+ digestmod=sha256,
+ ).hexdigest()
+
+ if not compare_digest(want_mac, userhmac):
+ raise SynapseError(http_client.FORBIDDEN, "HMAC incorrect")
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