413 lines
15 KiB
Python
413 lines
15 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2019 The Matrix.org Foundation C.I.C.
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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 logging
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import re
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from typing import Tuple
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import attr
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import saml2
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import saml2.response
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from saml2.client import Saml2Client
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from synapse.api.errors import SynapseError
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from synapse.config import ConfigError
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from synapse.http.server import finish_request
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from synapse.http.servlet import parse_string
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from synapse.module_api import ModuleApi
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from synapse.module_api.errors import RedirectException
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from synapse.types import (
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UserID,
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map_username_to_mxid_localpart,
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mxid_localpart_allowed_characters,
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)
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from synapse.util.async_helpers import Linearizer
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from synapse.util.iterutils import chunk_seq
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logger = logging.getLogger(__name__)
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@attr.s
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class Saml2SessionData:
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"""Data we track about SAML2 sessions"""
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# time the session was created, in milliseconds
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creation_time = attr.ib()
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class SamlHandler:
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def __init__(self, hs):
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self._saml_client = Saml2Client(hs.config.saml2_sp_config)
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self._auth_handler = hs.get_auth_handler()
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self._registration_handler = hs.get_registration_handler()
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self._clock = hs.get_clock()
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self._datastore = hs.get_datastore()
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self._hostname = hs.hostname
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self._saml2_session_lifetime = hs.config.saml2_session_lifetime
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self._grandfathered_mxid_source_attribute = (
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hs.config.saml2_grandfathered_mxid_source_attribute
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)
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# plugin to do custom mapping from saml response to mxid
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self._user_mapping_provider = hs.config.saml2_user_mapping_provider_class(
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hs.config.saml2_user_mapping_provider_config,
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ModuleApi(hs, hs.get_auth_handler()),
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)
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# identifier for the external_ids table
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self._auth_provider_id = "saml"
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# a map from saml session id to Saml2SessionData object
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self._outstanding_requests_dict = {}
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# a lock on the mappings
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self._mapping_lock = Linearizer(name="saml_mapping", clock=self._clock)
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self._error_html_content = hs.config.saml2_error_html_content
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def handle_redirect_request(self, client_redirect_url):
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"""Handle an incoming request to /login/sso/redirect
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Args:
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client_redirect_url (bytes): the URL that we should redirect the
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client to when everything is done
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Returns:
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bytes: URL to redirect to
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"""
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reqid, info = self._saml_client.prepare_for_authenticate(
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relay_state=client_redirect_url
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)
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now = self._clock.time_msec()
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self._outstanding_requests_dict[reqid] = Saml2SessionData(creation_time=now)
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for key, value in info["headers"]:
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if key == "Location":
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return value
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# this shouldn't happen!
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raise Exception("prepare_for_authenticate didn't return a Location header")
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async def handle_saml_response(self, request):
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"""Handle an incoming request to /_matrix/saml2/authn_response
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Args:
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request (SynapseRequest): the incoming request from the browser. We'll
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respond to it with a redirect.
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Returns:
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Deferred[none]: Completes once we have handled the request.
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"""
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resp_bytes = parse_string(request, "SAMLResponse", required=True)
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relay_state = parse_string(request, "RelayState", required=True)
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# expire outstanding sessions before parse_authn_request_response checks
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# the dict.
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self.expire_sessions()
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try:
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user_id = await self._map_saml_response_to_user(resp_bytes, relay_state)
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except RedirectException:
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# Raise the exception as per the wishes of the SAML module response
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raise
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except Exception as e:
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# If decoding the response or mapping it to a user failed, then log the
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# error and tell the user that something went wrong.
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logger.error(e)
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request.setResponseCode(400)
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request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
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request.setHeader(
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b"Content-Length", b"%d" % (len(self._error_html_content),)
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)
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request.write(self._error_html_content.encode("utf8"))
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finish_request(request)
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return
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self._auth_handler.complete_sso_login(user_id, request, relay_state)
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async def _map_saml_response_to_user(self, resp_bytes, client_redirect_url):
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try:
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saml2_auth = self._saml_client.parse_authn_request_response(
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resp_bytes,
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saml2.BINDING_HTTP_POST,
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outstanding=self._outstanding_requests_dict,
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)
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except Exception as e:
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logger.warning("Exception parsing SAML2 response: %s", e)
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raise SynapseError(400, "Unable to parse SAML2 response: %s" % (e,))
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if saml2_auth.not_signed:
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logger.warning("SAML2 response was not signed")
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raise SynapseError(400, "SAML2 response was not signed")
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logger.debug("SAML2 response: %s", saml2_auth.origxml)
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for assertion in saml2_auth.assertions:
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# kibana limits the length of a log field, whereas this is all rather
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# useful, so split it up.
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count = 0
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for part in chunk_seq(str(assertion), 10000):
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logger.info(
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"SAML2 assertion: %s%s", "(%i)..." % (count,) if count else "", part
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)
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count += 1
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logger.info("SAML2 mapped attributes: %s", saml2_auth.ava)
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self._outstanding_requests_dict.pop(saml2_auth.in_response_to, None)
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remote_user_id = self._user_mapping_provider.get_remote_user_id(
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saml2_auth, client_redirect_url
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)
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if not remote_user_id:
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raise Exception("Failed to extract remote user id from SAML response")
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with (await self._mapping_lock.queue(self._auth_provider_id)):
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# first of all, check if we already have a mapping for this user
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logger.info(
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"Looking for existing mapping for user %s:%s",
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self._auth_provider_id,
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remote_user_id,
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)
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registered_user_id = await self._datastore.get_user_by_external_id(
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self._auth_provider_id, remote_user_id
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)
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if registered_user_id is not None:
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logger.info("Found existing mapping %s", registered_user_id)
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return registered_user_id
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# backwards-compatibility hack: see if there is an existing user with a
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# suitable mapping from the uid
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if (
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self._grandfathered_mxid_source_attribute
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and self._grandfathered_mxid_source_attribute in saml2_auth.ava
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):
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attrval = saml2_auth.ava[self._grandfathered_mxid_source_attribute][0]
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user_id = UserID(
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map_username_to_mxid_localpart(attrval), self._hostname
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).to_string()
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logger.info(
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"Looking for existing account based on mapped %s %s",
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self._grandfathered_mxid_source_attribute,
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user_id,
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)
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users = await self._datastore.get_users_by_id_case_insensitive(user_id)
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if users:
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registered_user_id = list(users.keys())[0]
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logger.info("Grandfathering mapping to %s", registered_user_id)
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await self._datastore.record_user_external_id(
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self._auth_provider_id, remote_user_id, registered_user_id
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)
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return registered_user_id
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# Map saml response to user attributes using the configured mapping provider
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for i in range(1000):
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attribute_dict = self._user_mapping_provider.saml_response_to_user_attributes(
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saml2_auth, i, client_redirect_url=client_redirect_url,
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)
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logger.debug(
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"Retrieved SAML attributes from user mapping provider: %s "
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"(attempt %d)",
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attribute_dict,
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i,
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)
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localpart = attribute_dict.get("mxid_localpart")
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if not localpart:
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logger.error(
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"SAML mapping provider plugin did not return a "
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"mxid_localpart object"
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)
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raise SynapseError(500, "Error parsing SAML2 response")
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displayname = attribute_dict.get("displayname")
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# Check if this mxid already exists
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if not await self._datastore.get_users_by_id_case_insensitive(
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UserID(localpart, self._hostname).to_string()
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):
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# This mxid is free
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break
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else:
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# Unable to generate a username in 1000 iterations
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# Break and return error to the user
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raise SynapseError(
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500, "Unable to generate a Matrix ID from the SAML response"
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)
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logger.info("Mapped SAML user to local part %s", localpart)
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registered_user_id = await self._registration_handler.register_user(
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localpart=localpart, default_display_name=displayname
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)
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await self._datastore.record_user_external_id(
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self._auth_provider_id, remote_user_id, registered_user_id
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)
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return registered_user_id
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def expire_sessions(self):
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expire_before = self._clock.time_msec() - self._saml2_session_lifetime
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to_expire = set()
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for reqid, data in self._outstanding_requests_dict.items():
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if data.creation_time < expire_before:
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to_expire.add(reqid)
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for reqid in to_expire:
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logger.debug("Expiring session id %s", reqid)
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del self._outstanding_requests_dict[reqid]
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DOT_REPLACE_PATTERN = re.compile(
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("[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),))
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)
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def dot_replace_for_mxid(username: str) -> str:
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username = username.lower()
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username = DOT_REPLACE_PATTERN.sub(".", username)
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# regular mxids aren't allowed to start with an underscore either
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username = re.sub("^_", "", username)
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return username
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MXID_MAPPER_MAP = {
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"hexencode": map_username_to_mxid_localpart,
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"dotreplace": dot_replace_for_mxid,
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}
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@attr.s
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class SamlConfig(object):
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mxid_source_attribute = attr.ib()
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mxid_mapper = attr.ib()
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class DefaultSamlMappingProvider(object):
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__version__ = "0.0.1"
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def __init__(self, parsed_config: SamlConfig, module_api: ModuleApi):
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"""The default SAML user mapping provider
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Args:
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parsed_config: Module configuration
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module_api: module api proxy
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"""
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self._mxid_source_attribute = parsed_config.mxid_source_attribute
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self._mxid_mapper = parsed_config.mxid_mapper
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self._grandfathered_mxid_source_attribute = (
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module_api._hs.config.saml2_grandfathered_mxid_source_attribute
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)
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def get_remote_user_id(
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self, saml_response: saml2.response.AuthnResponse, client_redirect_url: str
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):
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"""Extracts the remote user id from the SAML response"""
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try:
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return saml_response.ava["uid"][0]
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except KeyError:
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logger.warning("SAML2 response lacks a 'uid' attestation")
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raise SynapseError(400, "'uid' not in SAML2 response")
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def saml_response_to_user_attributes(
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self,
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saml_response: saml2.response.AuthnResponse,
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failures: int,
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client_redirect_url: str,
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) -> dict:
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"""Maps some text from a SAML response to attributes of a new user
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Args:
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saml_response: A SAML auth response object
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failures: How many times a call to this function with this
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saml_response has resulted in a failure
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client_redirect_url: where the client wants to redirect to
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Returns:
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dict: A dict containing new user attributes. Possible keys:
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* mxid_localpart (str): Required. The localpart of the user's mxid
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* displayname (str): The displayname of the user
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"""
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try:
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mxid_source = saml_response.ava[self._mxid_source_attribute][0]
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except KeyError:
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logger.warning(
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"SAML2 response lacks a '%s' attestation", self._mxid_source_attribute,
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)
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raise SynapseError(
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400, "%s not in SAML2 response" % (self._mxid_source_attribute,)
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)
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# Use the configured mapper for this mxid_source
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base_mxid_localpart = self._mxid_mapper(mxid_source)
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# Append suffix integer if last call to this function failed to produce
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# a usable mxid
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localpart = base_mxid_localpart + (str(failures) if failures else "")
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# Retrieve the display name from the saml response
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# If displayname is None, the mxid_localpart will be used instead
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displayname = saml_response.ava.get("displayName", [None])[0]
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return {
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"mxid_localpart": localpart,
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"displayname": displayname,
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}
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@staticmethod
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def parse_config(config: dict) -> SamlConfig:
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"""Parse the dict provided by the homeserver's config
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Args:
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config: A dictionary containing configuration options for this provider
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Returns:
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SamlConfig: A custom config object for this module
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"""
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# Parse config options and use defaults where necessary
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mxid_source_attribute = config.get("mxid_source_attribute", "uid")
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mapping_type = config.get("mxid_mapping", "hexencode")
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# Retrieve the associating mapping function
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try:
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mxid_mapper = MXID_MAPPER_MAP[mapping_type]
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except KeyError:
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raise ConfigError(
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"saml2_config.user_mapping_provider.config: '%s' is not a valid "
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"mxid_mapping value" % (mapping_type,)
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)
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return SamlConfig(mxid_source_attribute, mxid_mapper)
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@staticmethod
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def get_saml_attributes(config: SamlConfig) -> Tuple[set, set]:
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"""Returns the required attributes of a SAML
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Args:
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config: A SamlConfig object containing configuration params for this provider
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Returns:
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tuple[set,set]: The first set equates to the saml auth response
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attributes that are required for the module to function, whereas the
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second set consists of those attributes which can be used if
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available, but are not necessary
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"""
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return {"uid", config.mxid_source_attribute}, {"displayName"}
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