# # This file is licensed under the Affero General Public License (AGPL) version 3. # # Copyright 2020 The Matrix.org Foundation C.I.C. # Copyright (C) 2023 New Vector, Ltd # # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU Affero General Public License as # published by the Free Software Foundation, either version 3 of the # License, or (at your option) any later version. # # See the GNU Affero General Public License for more details: # . # # Originally licensed under the Apache License, Version 2.0: # . # # [This file includes modifications made by New Vector Limited] # # import logging import urllib.parse from typing import TYPE_CHECKING, Dict, List, Optional from xml.etree import ElementTree as ET import attr from twisted.web.client import PartialDownloadError from synapse.api.errors import HttpResponseException from synapse.handlers.sso import MappingException, UserAttributes from synapse.http.site import SynapseRequest from synapse.types import UserID, map_username_to_mxid_localpart if TYPE_CHECKING: from synapse.server import HomeServer logger = logging.getLogger(__name__) class CasError(Exception): """Used to catch errors when validating the CAS ticket.""" def __init__(self, error: str, error_description: Optional[str] = None): self.error = error self.error_description = error_description def __str__(self) -> str: if self.error_description: return f"{self.error}: {self.error_description}" return self.error @attr.s(slots=True, frozen=True, auto_attribs=True) class CasResponse: username: str attributes: Dict[str, List[Optional[str]]] class CasHandler: """ Utility class for to handle the response from a CAS SSO service. Args: hs """ def __init__(self, hs: "HomeServer"): self.hs = hs self._hostname = hs.hostname self._store = hs.get_datastores().main self._auth_handler = hs.get_auth_handler() self._registration_handler = hs.get_registration_handler() self._cas_server_url = hs.config.cas.cas_server_url self._cas_service_url = hs.config.cas.cas_service_url self._cas_protocol_version = hs.config.cas.cas_protocol_version self._cas_displayname_attribute = hs.config.cas.cas_displayname_attribute self._cas_required_attributes = hs.config.cas.cas_required_attributes self._cas_enable_registration = hs.config.cas.cas_enable_registration self._cas_allow_numeric_ids = hs.config.cas.cas_allow_numeric_ids self._cas_numeric_ids_prefix = hs.config.cas.cas_numeric_ids_prefix self._http_client = hs.get_proxied_http_client() # identifier for the external_ids table self.idp_id = "cas" # user-facing name of this auth provider self.idp_name = hs.config.cas.idp_name # MXC URI for icon for this auth provider self.idp_icon = hs.config.cas.idp_icon # optional brand identifier for this auth provider self.idp_brand = hs.config.cas.idp_brand self._sso_handler = hs.get_sso_handler() self._sso_handler.register_identity_provider(self) def _build_service_param(self, args: Dict[str, str]) -> str: """ Generates a value to use as the "service" parameter when redirecting or querying the CAS service. Args: args: Additional arguments to include in the final redirect URL. Returns: The URL to use as a "service" parameter. """ return "%s?%s" % ( self._cas_service_url, urllib.parse.urlencode(args), ) async def _validate_ticket( self, ticket: str, service_args: Dict[str, str] ) -> CasResponse: """ Validate a CAS ticket with the server, and return the parsed the response. Args: ticket: The CAS ticket from the client. service_args: Additional arguments to include in the service URL. Should be the same as those passed to `handle_redirect_request`. Raises: CasError: If there's an error parsing the CAS response. Returns: The parsed CAS response. """ if self._cas_protocol_version == 3: uri = self._cas_server_url + "/p3/proxyValidate" else: uri = self._cas_server_url + "/proxyValidate" args = { "ticket": ticket, "service": self._build_service_param(service_args), } try: body = await self._http_client.get_raw(uri, args) except PartialDownloadError as pde: # Twisted raises this error if the connection is closed, # even if that's being used old-http style to signal end-of-data # Assertion is for mypy's benefit. Error.response is Optional[bytes], # but a PartialDownloadError should always have a non-None response. assert pde.response is not None body = pde.response except HttpResponseException as e: description = ( 'Authorization server responded with a "{status}" error ' "while exchanging the authorization code." ).format(status=e.code) raise CasError("server_error", description) from e return self._parse_cas_response(body) def _parse_cas_response(self, cas_response_body: bytes) -> CasResponse: """ Retrieve the user and other parameters from the CAS response. Args: cas_response_body: The response from the CAS query. Raises: CasError: If there's an error parsing the CAS response. Returns: The parsed CAS response. """ # Ensure the response is valid. root = ET.fromstring(cas_response_body) if not root.tag.endswith("serviceResponse"): raise CasError( "missing_service_response", "root of CAS response is not serviceResponse", ) success = root[0].tag.endswith("authenticationSuccess") if not success: raise CasError("unsucessful_response", "Unsuccessful CAS response") # Iterate through the nodes and pull out the user and any extra attributes. user = None attributes: Dict[str, List[Optional[str]]] = {} for child in root[0]: if child.tag.endswith("user"): user = child.text # if numeric user IDs are allowed and username is numeric then we add the prefix so Synapse can handle it if self._cas_allow_numeric_ids and user is not None and user.isdigit(): user = f"{self._cas_numeric_ids_prefix}{user}" if child.tag.endswith("attributes"): for attribute in child: # ElementTree library expands the namespace in # attribute tags to the full URL of the namespace. # We don't care about namespace here and it will always # be encased in curly braces, so we remove them. tag = attribute.tag if "}" in tag: tag = tag.split("}")[1] attributes.setdefault(tag, []).append(attribute.text) # Ensure a user was found. if user is None: raise CasError("no_user", "CAS response does not contain user") return CasResponse(user, attributes) async def handle_redirect_request( self, request: SynapseRequest, client_redirect_url: Optional[bytes], ui_auth_session_id: Optional[str] = None, ) -> str: """Generates a URL for the CAS server where the client should be redirected. Args: request: the incoming HTTP request client_redirect_url: the URL that we should redirect the client to after login (or None for UI Auth). ui_auth_session_id: The session ID of the ongoing UI Auth (or None if this is a login). Returns: URL to redirect to """ if ui_auth_session_id: service_args = {"session": ui_auth_session_id} else: assert client_redirect_url service_args = {"redirectUrl": client_redirect_url.decode("utf8")} args = urllib.parse.urlencode( {"service": self._build_service_param(service_args)} ) return "%s/login?%s" % (self._cas_server_url, args) async def handle_ticket( self, request: SynapseRequest, ticket: str, client_redirect_url: Optional[str], session: Optional[str], ) -> None: """ Called once the user has successfully authenticated with the SSO. Validates a CAS ticket sent by the client and completes the auth process. If the user interactive authentication session is provided, marks the UI Auth session as complete, then returns an HTML page notifying the user they are done. Otherwise, this registers the user if necessary, and then returns a redirect (with a login token) to the client. Args: request: the incoming request from the browser. We'll respond to it with a redirect or an HTML page. ticket: The CAS ticket provided by the client. client_redirect_url: the redirectUrl parameter from the `/cas/ticket` HTTP request, if given. This should be the same as the redirectUrl from the original `/login/sso/redirect` request. session: The session parameter from the `/cas/ticket` HTTP request, if given. This should be the UI Auth session id. """ args = {} if client_redirect_url: args["redirectUrl"] = client_redirect_url if session: args["session"] = session try: cas_response = await self._validate_ticket(ticket, args) except CasError as e: logger.exception("Could not validate ticket") self._sso_handler.render_error(request, e.error, e.error_description, 401) return await self._handle_cas_response( request, cas_response, client_redirect_url, session ) async def _handle_cas_response( self, request: SynapseRequest, cas_response: CasResponse, client_redirect_url: Optional[str], session: Optional[str], ) -> None: """Handle a CAS response to a ticket request. Assumes that the response has been validated. Maps the user onto an MXID, registering them if necessary, and returns a response to the browser. Args: request: the incoming request from the browser. We'll respond to it with an HTML page or a redirect cas_response: The parsed CAS response. client_redirect_url: the redirectUrl parameter from the `/cas/ticket` HTTP request, if given. This should be the same as the redirectUrl from the original `/login/sso/redirect` request. session: The session parameter from the `/cas/ticket` HTTP request, if given. This should be the UI Auth session id. """ # first check if we're doing a UIA if session: return await self._sso_handler.complete_sso_ui_auth_request( self.idp_id, cas_response.username, session, request, ) # otherwise, we're handling a login request. # Ensure that the attributes of the logged in user meet the required # attributes. if not self._sso_handler.check_required_attributes( request, cas_response.attributes, self._cas_required_attributes ): return # Call the mapper to register/login the user # If this not a UI auth request than there must be a redirect URL. assert client_redirect_url is not None try: await self._complete_cas_login(cas_response, request, client_redirect_url) except MappingException as e: logger.exception("Could not map user") self._sso_handler.render_error(request, "mapping_error", str(e)) async def _complete_cas_login( self, cas_response: CasResponse, request: SynapseRequest, client_redirect_url: str, ) -> None: """ Given a CAS response, complete the login flow Retrieves the remote user ID, registers the user if necessary, and serves a redirect back to the client with a login-token. Args: cas_response: The parsed CAS response. request: The request to respond to client_redirect_url: The redirect URL passed in by the client. Raises: MappingException if there was a problem mapping the response to a user. RedirectException: some mapping providers may raise this if they need to redirect to an interstitial page. """ # Note that CAS does not support a mapping provider, so the logic is hard-coded. localpart = map_username_to_mxid_localpart(cas_response.username) async def cas_response_to_user_attributes(failures: int) -> UserAttributes: """ Map from CAS attributes to user attributes. """ # Due to the grandfathering logic matching any previously registered # mxids it isn't expected for there to be any failures. if failures: raise RuntimeError("CAS is not expected to de-duplicate Matrix IDs") # Arbitrarily use the first attribute found. display_name = cas_response.attributes.get( self._cas_displayname_attribute, [None] )[0] return UserAttributes(localpart=localpart, display_name=display_name) async def grandfather_existing_users() -> Optional[str]: # Since CAS did not always use the user_external_ids table, always # to attempt to map to existing users. user_id = UserID(localpart, self._hostname).to_string() logger.debug( "Looking for existing account based on mapped %s", user_id, ) users = await self._store.get_users_by_id_case_insensitive(user_id) if users: registered_user_id = list(users.keys())[0] logger.info("Grandfathering mapping to %s", registered_user_id) return registered_user_id return None await self._sso_handler.complete_sso_login_request( self.idp_id, cas_response.username, request, client_redirect_url, cas_response_to_user_attributes, grandfather_existing_users, registration_enabled=self._cas_enable_registration, )