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Diffstat (limited to 'synapse/handlers/cas_handler.py')
| -rw-r--r-- | synapse/handlers/cas_handler.py | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/synapse/handlers/cas_handler.py b/synapse/handlers/cas_handler.py new file mode 100644 index 0000000000..64aaa1335c --- /dev/null +++ b/synapse/handlers/cas_handler.py @@ -0,0 +1,221 @@ +# -*- coding: utf-8 -*- +# Copyright 2020 The Matrix.org Foundation C.I.C. +# +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +import logging +import xml.etree.ElementTree as ET +from typing import Dict, Optional, Tuple + +from six.moves import urllib + +from twisted.web.client import PartialDownloadError + +from synapse.api.errors import Codes, LoginError +from synapse.http.site import SynapseRequest +from synapse.types import UserID, map_username_to_mxid_localpart + +logger = logging.getLogger(__name__) + + +class CasHandler: + """ + Utility class for to handle the response from a CAS SSO service. + + Args: + hs (synapse.server.HomeServer) + """ + + def __init__(self, hs): + self._hostname = hs.hostname + self._auth_handler = hs.get_auth_handler() + self._registration_handler = hs.get_registration_handler() + + self._cas_server_url = hs.config.cas_server_url + self._cas_service_url = hs.config.cas_service_url + self._cas_displayname_attribute = hs.config.cas_displayname_attribute + self._cas_required_attributes = hs.config.cas_required_attributes + + self._http_client = hs.get_proxied_http_client() + + 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?%s" % ( + self._cas_service_url, + "/_matrix/client/r0/login/cas/ticket", + urllib.parse.urlencode(args), + ) + + async def _validate_ticket( + self, ticket: str, service_args: Dict[str, str] + ) -> Tuple[str, Optional[str]]: + """ + Validate a CAS ticket with the server, parse the response, and return the user and display name. + + 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 `get_redirect_url`. + """ + 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 + body = pde.response + + user, attributes = self._parse_cas_response(body) + displayname = attributes.pop(self._cas_displayname_attribute, None) + + for required_attribute, required_value in self._cas_required_attributes.items(): + # If required attribute was not in CAS Response - Forbidden + if required_attribute not in attributes: + raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED) + + # Also need to check value + if required_value is not None: + actual_value = attributes[required_attribute] + # If required attribute value does not match expected - Forbidden + if required_value != actual_value: + raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED) + + return user, displayname + + def _parse_cas_response( + self, cas_response_body: str + ) -> Tuple[str, Dict[str, Optional[str]]]: + """ + Retrieve the user and other parameters from the CAS response. + + Args: + cas_response_body: The response from the CAS query. + + Returns: + A tuple of the user and a mapping of other attributes. + """ + user = None + attributes = {} + try: + root = ET.fromstring(cas_response_body) + if not root.tag.endswith("serviceResponse"): + raise Exception("root of CAS response is not serviceResponse") + success = root[0].tag.endswith("authenticationSuccess") + for child in root[0]: + if child.tag.endswith("user"): + user = child.text + 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[tag] = attribute.text + if user is None: + raise Exception("CAS response does not contain user") + except Exception: + logger.exception("Error parsing CAS response") + raise LoginError(401, "Invalid CAS response", errcode=Codes.UNAUTHORIZED) + if not success: + raise LoginError( + 401, "Unsuccessful CAS response", errcode=Codes.UNAUTHORIZED + ) + return user, attributes + + def get_redirect_url(self, service_args: Dict[str, str]) -> str: + """ + Generates a URL for the CAS server where the client should be redirected. + + Args: + service_args: Additional arguments to include in the final redirect URL. + + Returns: + The URL to redirect the client to. + """ + 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 + username, user_display_name = await self._validate_ticket(ticket, args) + + localpart = map_username_to_mxid_localpart(username) + user_id = UserID(localpart, self._hostname).to_string() + registered_user_id = await self._auth_handler.check_user_exists(user_id) + + if session: + await self._auth_handler.complete_sso_ui_auth( + registered_user_id, session, request, + ) + + else: + if not registered_user_id: + registered_user_id = await self._registration_handler.register_user( + localpart=localpart, default_display_name=user_display_name + ) + + await self._auth_handler.complete_sso_login( + registered_user_id, request, client_redirect_url + ) |