220 lines
8.3 KiB
Python
220 lines
8.3 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2020 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 urllib
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from typing import Dict, Optional, Tuple
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from xml.etree import ElementTree as ET
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from twisted.web.client import PartialDownloadError
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from synapse.api.errors import Codes, LoginError
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from synapse.http.site import SynapseRequest
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from synapse.types import UserID, map_username_to_mxid_localpart
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logger = logging.getLogger(__name__)
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class CasHandler:
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"""
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Utility class for to handle the response from a CAS SSO service.
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Args:
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hs (synapse.server.HomeServer)
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"""
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def __init__(self, hs):
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self._hostname = hs.hostname
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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._cas_server_url = hs.config.cas_server_url
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self._cas_service_url = hs.config.cas_service_url
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self._cas_displayname_attribute = hs.config.cas_displayname_attribute
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self._cas_required_attributes = hs.config.cas_required_attributes
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self._http_client = hs.get_proxied_http_client()
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def _build_service_param(self, args: Dict[str, str]) -> str:
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"""
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Generates a value to use as the "service" parameter when redirecting or
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querying the CAS service.
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Args:
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args: Additional arguments to include in the final redirect URL.
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Returns:
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The URL to use as a "service" parameter.
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"""
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return "%s%s?%s" % (
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self._cas_service_url,
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"/_matrix/client/r0/login/cas/ticket",
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urllib.parse.urlencode(args),
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)
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async def _validate_ticket(
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self, ticket: str, service_args: Dict[str, str]
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) -> Tuple[str, Optional[str]]:
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"""
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Validate a CAS ticket with the server, parse the response, and return the user and display name.
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Args:
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ticket: The CAS ticket from the client.
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service_args: Additional arguments to include in the service URL.
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Should be the same as those passed to `get_redirect_url`.
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"""
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uri = self._cas_server_url + "/proxyValidate"
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args = {
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"ticket": ticket,
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"service": self._build_service_param(service_args),
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}
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try:
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body = await self._http_client.get_raw(uri, args)
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except PartialDownloadError as pde:
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# Twisted raises this error if the connection is closed,
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# even if that's being used old-http style to signal end-of-data
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body = pde.response
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user, attributes = self._parse_cas_response(body)
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displayname = attributes.pop(self._cas_displayname_attribute, None)
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for required_attribute, required_value in self._cas_required_attributes.items():
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# If required attribute was not in CAS Response - Forbidden
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if required_attribute not in attributes:
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raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
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# Also need to check value
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if required_value is not None:
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actual_value = attributes[required_attribute]
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# If required attribute value does not match expected - Forbidden
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if required_value != actual_value:
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raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
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return user, displayname
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def _parse_cas_response(
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self, cas_response_body: str
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) -> Tuple[str, Dict[str, Optional[str]]]:
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"""
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Retrieve the user and other parameters from the CAS response.
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Args:
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cas_response_body: The response from the CAS query.
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Returns:
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A tuple of the user and a mapping of other attributes.
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"""
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user = None
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attributes = {}
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try:
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root = ET.fromstring(cas_response_body)
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if not root.tag.endswith("serviceResponse"):
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raise Exception("root of CAS response is not serviceResponse")
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success = root[0].tag.endswith("authenticationSuccess")
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for child in root[0]:
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if child.tag.endswith("user"):
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user = child.text
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if child.tag.endswith("attributes"):
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for attribute in child:
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# ElementTree library expands the namespace in
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# attribute tags to the full URL of the namespace.
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# We don't care about namespace here and it will always
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# be encased in curly braces, so we remove them.
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tag = attribute.tag
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if "}" in tag:
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tag = tag.split("}")[1]
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attributes[tag] = attribute.text
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if user is None:
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raise Exception("CAS response does not contain user")
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except Exception:
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logger.exception("Error parsing CAS response")
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raise LoginError(401, "Invalid CAS response", errcode=Codes.UNAUTHORIZED)
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if not success:
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raise LoginError(
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401, "Unsuccessful CAS response", errcode=Codes.UNAUTHORIZED
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)
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return user, attributes
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def get_redirect_url(self, service_args: Dict[str, str]) -> str:
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"""
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Generates a URL for the CAS server where the client should be redirected.
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Args:
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service_args: Additional arguments to include in the final redirect URL.
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Returns:
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The URL to redirect the client to.
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"""
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args = urllib.parse.urlencode(
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{"service": self._build_service_param(service_args)}
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)
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return "%s/login?%s" % (self._cas_server_url, args)
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async def handle_ticket(
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self,
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request: SynapseRequest,
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ticket: str,
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client_redirect_url: Optional[str],
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session: Optional[str],
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) -> None:
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"""
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Called once the user has successfully authenticated with the SSO.
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Validates a CAS ticket sent by the client and completes the auth process.
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If the user interactive authentication session is provided, marks the
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UI Auth session as complete, then returns an HTML page notifying the
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user they are done.
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Otherwise, this registers the user if necessary, and then returns a
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redirect (with a login token) to the client.
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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 or an HTML page.
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ticket: The CAS ticket provided by the client.
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client_redirect_url: the redirectUrl parameter from the `/cas/ticket` HTTP request, if given.
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This should be the same as the redirectUrl from the original `/login/sso/redirect` request.
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session: The session parameter from the `/cas/ticket` HTTP request, if given.
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This should be the UI Auth session id.
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"""
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args = {}
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if client_redirect_url:
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args["redirectUrl"] = client_redirect_url
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if session:
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args["session"] = session
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username, user_display_name = await self._validate_ticket(ticket, args)
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localpart = map_username_to_mxid_localpart(username)
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user_id = UserID(localpart, self._hostname).to_string()
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registered_user_id = await self._auth_handler.check_user_exists(user_id)
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if session:
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await self._auth_handler.complete_sso_ui_auth(
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registered_user_id, session, request,
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)
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else:
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if not registered_user_id:
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registered_user_id = await self._registration_handler.register_user(
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localpart=localpart, default_display_name=user_display_name
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)
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await self._auth_handler.complete_sso_login(
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registered_user_id, request, client_redirect_url
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)
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