517 lines
19 KiB
Python
517 lines
19 KiB
Python
# 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 TYPE_CHECKING, Callable, Dict, Optional, Set, 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.handlers.sso import MappingException, UserAttributes
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from synapse.http.servlet import parse_string
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from synapse.http.site import SynapseRequest
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from synapse.module_api import ModuleApi
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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.iterutils import chunk_seq
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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@attr.s(slots=True, auto_attribs=True)
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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: int
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# The user interactive authentication session ID associated with this SAML
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# session (or None if this SAML session is for an initial login).
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ui_auth_session_id: Optional[str] = None
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class SamlHandler:
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def __init__(self, hs: "HomeServer"):
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self.store = hs.get_datastores().main
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self.clock = hs.get_clock()
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self.server_name = hs.hostname
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self._saml_client = Saml2Client(hs.config.saml2.saml2_sp_config)
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self._saml_idp_entityid = hs.config.saml2.saml2_idp_entityid
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self._saml2_session_lifetime = hs.config.saml2.saml2_session_lifetime
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self._grandfathered_mxid_source_attribute = (
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hs.config.saml2.saml2_grandfathered_mxid_source_attribute
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)
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self._saml2_attribute_requirements = hs.config.saml2.attribute_requirements
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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.saml2_user_mapping_provider_class(
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hs.config.saml2.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.idp_id = "saml"
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# user-facing name of this auth provider
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self.idp_name = "SAML"
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# we do not currently support icons/brands for SAML auth, but this is required by
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# the SsoIdentityProvider protocol type.
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self.idp_icon = None
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self.idp_brand = None
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# a map from saml session id to Saml2SessionData object
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self._outstanding_requests_dict: Dict[str, Saml2SessionData] = {}
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self._sso_handler = hs.get_sso_handler()
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self._sso_handler.register_identity_provider(self)
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async def handle_redirect_request(
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self,
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request: SynapseRequest,
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client_redirect_url: Optional[bytes],
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ui_auth_session_id: Optional[str] = None,
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) -> str:
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"""Handle an incoming request to /login/sso/redirect
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Args:
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request: the incoming HTTP request
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client_redirect_url: the URL that we should redirect the
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client to after login (or None for UI Auth).
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ui_auth_session_id: The session ID of the ongoing UI Auth (or
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None if this is a login).
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Returns:
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URL to redirect to
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"""
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if not client_redirect_url:
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# Some SAML identity providers (e.g. Google) require a
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# RelayState parameter on requests, so pass in a dummy redirect URL
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# (which will never get used).
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client_redirect_url = b"unused"
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reqid, info = self._saml_client.prepare_for_authenticate(
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entityid=self._saml_idp_entityid, relay_state=client_redirect_url
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)
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# Since SAML sessions timeout it is useful to log when they were created.
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logger.info("Initiating a new SAML session: %s" % (reqid,))
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now = self.clock.time_msec()
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self._outstanding_requests_dict[reqid] = Saml2SessionData(
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creation_time=now,
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ui_auth_session_id=ui_auth_session_id,
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)
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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: SynapseRequest) -> None:
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"""Handle an incoming request to /_synapse/client/saml2/authn_response
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Args:
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request: 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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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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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 saml2.response.UnsolicitedResponse as e:
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# the pysaml2 library helpfully logs an ERROR here, but neglects to log
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# the session ID. I don't really want to put the full text of the exception
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# in the (user-visible) exception message, so let's log the exception here
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# so we can track down the session IDs later.
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logger.warning(str(e))
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self._sso_handler.render_error(
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request, "unsolicited_response", "Unexpected SAML2 login."
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)
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return
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except Exception as e:
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self._sso_handler.render_error(
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request,
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"invalid_response",
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"Unable to parse SAML2 response: %s." % (e,),
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)
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return
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if saml2_auth.not_signed:
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self._sso_handler.render_error(
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request, "unsigned_respond", "SAML2 response was not signed."
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)
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return
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logger.debug("SAML2 response: %s", saml2_auth.origxml)
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await self._handle_authn_response(request, saml2_auth, relay_state)
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async def _handle_authn_response(
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self,
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request: SynapseRequest,
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saml2_auth: saml2.response.AuthnResponse,
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relay_state: str,
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) -> None:
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"""Handle an AuthnResponse, having parsed it from the request params
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Assumes that the signature on the response object has been checked. Maps
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the user onto an MXID, registering them if necessary, and returns a response
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to the browser.
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Args:
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request: the incoming request from the browser. We'll respond to it with an
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HTML page or a redirect
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saml2_auth: the parsed AuthnResponse object
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relay_state: the RelayState query param, which encodes the URI to rediret
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back to
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"""
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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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current_session = self._outstanding_requests_dict.pop(
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saml2_auth.in_response_to, None
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)
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# first check if we're doing a UIA
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if current_session and current_session.ui_auth_session_id:
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try:
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remote_user_id = self._remote_id_from_saml_response(saml2_auth, None)
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except MappingException as e:
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logger.exception("Failed to extract remote user id from SAML response")
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self._sso_handler.render_error(request, "mapping_error", str(e))
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return
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return await self._sso_handler.complete_sso_ui_auth_request(
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self.idp_id,
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remote_user_id,
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current_session.ui_auth_session_id,
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request,
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)
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# otherwise, we're handling a login request.
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# Ensure that the attributes of the logged in user meet the required
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# attributes.
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if not self._sso_handler.check_required_attributes(
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request, saml2_auth.ava, self._saml2_attribute_requirements
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):
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return
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# Call the mapper to register/login the user
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try:
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await self._complete_saml_login(saml2_auth, request, relay_state)
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except MappingException as e:
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logger.exception("Could not map user")
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self._sso_handler.render_error(request, "mapping_error", str(e))
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async def _complete_saml_login(
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self,
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saml2_auth: saml2.response.AuthnResponse,
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request: SynapseRequest,
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client_redirect_url: str,
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) -> None:
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"""
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Given a SAML response, complete the login flow
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Retrieves the remote user ID, registers the user if necessary, and serves
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a redirect back to the client with a login-token.
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Args:
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saml2_auth: The parsed SAML2 response.
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request: The request to respond to
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client_redirect_url: The redirect URL passed in by the client.
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Raises:
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MappingException if there was a problem mapping the response to a user.
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RedirectException: some mapping providers may raise this if they need
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to redirect to an interstitial page.
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"""
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remote_user_id = self._remote_id_from_saml_response(
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saml2_auth, client_redirect_url
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)
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async def saml_response_to_remapped_user_attributes(
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failures: int,
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) -> UserAttributes:
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"""
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Call the mapping provider to map a SAML response to user attributes and coerce the result into the standard form.
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This is backwards compatibility for abstraction for the SSO handler.
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"""
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# Call the mapping provider.
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result = self._user_mapping_provider.saml_response_to_user_attributes(
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saml2_auth, failures, client_redirect_url
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)
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# Remap some of the results.
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return UserAttributes(
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localpart=result.get("mxid_localpart"),
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display_name=result.get("displayname"),
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emails=result.get("emails", []),
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)
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async def grandfather_existing_users() -> Optional[str]:
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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.server_name
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).to_string()
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logger.debug(
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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.store.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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return registered_user_id
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return None
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await self._sso_handler.complete_sso_login_request(
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self.idp_id,
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remote_user_id,
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request,
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client_redirect_url,
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saml_response_to_remapped_user_attributes,
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grandfather_existing_users,
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)
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def _remote_id_from_saml_response(
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self,
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saml2_auth: saml2.response.AuthnResponse,
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client_redirect_url: Optional[str],
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) -> str:
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"""Extract the unique remote id from a SAML2 AuthnResponse
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Args:
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saml2_auth: The parsed SAML2 response.
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client_redirect_url: The redirect URL passed in by the client.
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Returns:
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remote user id
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Raises:
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MappingException if there was an error extracting the user id
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"""
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# It's not obvious why we need to pass in the redirect URI to the mapping
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# provider, but we do :/
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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 MappingException(
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"Failed to extract remote user id from SAML response"
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)
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return remote_user_id
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def expire_sessions(self) -> None:
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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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"""Replace any characters which are not allowed in Matrix IDs with a dot."""
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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: Dict[str, Callable[[str], str]] = {
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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(auto_attribs=True)
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class SamlConfig:
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mxid_source_attribute: str
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mxid_mapper: Callable[[str], str]
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class DefaultSamlMappingProvider:
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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.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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) -> str:
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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 MappingException("'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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* emails (list[str]): Any emails for 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",
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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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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 += 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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# Retrieve any emails present in the saml response
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emails = saml_response.ava.get("email", [])
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return {
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"mxid_localpart": localpart,
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"displayname": displayname,
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"emails": emails,
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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[str], Set[str]]:
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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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|
The first set equates to the saml auth response
|
|
attributes that are required for the module to function, whereas the
|
|
second set consists of those attributes which can be used if
|
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available, but are not necessary
|
|
"""
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return {"uid", config.mxid_source_attribute}, {"displayName", "email"}
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