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Diffstat (limited to 'synapse/handlers/saml.py')
| -rw-r--r-- | synapse/handlers/saml.py | 517 |
1 files changed, 517 insertions, 0 deletions
diff --git a/synapse/handlers/saml.py b/synapse/handlers/saml.py new file mode 100644 index 0000000000..80ba65b9e0 --- /dev/null +++ b/synapse/handlers/saml.py @@ -0,0 +1,517 @@ +# Copyright 2019 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 re +from typing import TYPE_CHECKING, Callable, Dict, Optional, Set, Tuple + +import attr +import saml2 +import saml2.response +from saml2.client import Saml2Client + +from synapse.api.errors import SynapseError +from synapse.config import ConfigError +from synapse.handlers._base import BaseHandler +from synapse.handlers.sso import MappingException, UserAttributes +from synapse.http.servlet import parse_string +from synapse.http.site import SynapseRequest +from synapse.module_api import ModuleApi +from synapse.types import ( + UserID, + map_username_to_mxid_localpart, + mxid_localpart_allowed_characters, +) +from synapse.util.iterutils import chunk_seq + +if TYPE_CHECKING: + from synapse.server import HomeServer + +logger = logging.getLogger(__name__) + + +@attr.s(slots=True) +class Saml2SessionData: + """Data we track about SAML2 sessions""" + + # time the session was created, in milliseconds + creation_time = attr.ib() + # The user interactive authentication session ID associated with this SAML + # session (or None if this SAML session is for an initial login). + ui_auth_session_id = attr.ib(type=Optional[str], default=None) + + +class SamlHandler(BaseHandler): + def __init__(self, hs: "HomeServer"): + super().__init__(hs) + self._saml_client = Saml2Client(hs.config.saml2_sp_config) + self._saml_idp_entityid = hs.config.saml2_idp_entityid + + self._saml2_session_lifetime = hs.config.saml2_session_lifetime + self._grandfathered_mxid_source_attribute = ( + hs.config.saml2_grandfathered_mxid_source_attribute + ) + self._saml2_attribute_requirements = hs.config.saml2.attribute_requirements + self._error_template = hs.config.sso_error_template + + # plugin to do custom mapping from saml response to mxid + self._user_mapping_provider = hs.config.saml2_user_mapping_provider_class( + hs.config.saml2_user_mapping_provider_config, + ModuleApi(hs, hs.get_auth_handler()), + ) + + # identifier for the external_ids table + self.idp_id = "saml" + + # user-facing name of this auth provider + self.idp_name = "SAML" + + # we do not currently support icons/brands for SAML auth, but this is required by + # the SsoIdentityProvider protocol type. + self.idp_icon = None + self.idp_brand = None + self.unstable_idp_brand = None + + # a map from saml session id to Saml2SessionData object + self._outstanding_requests_dict = {} # type: Dict[str, Saml2SessionData] + + self._sso_handler = hs.get_sso_handler() + self._sso_handler.register_identity_provider(self) + + async def handle_redirect_request( + self, + request: SynapseRequest, + client_redirect_url: Optional[bytes], + ui_auth_session_id: Optional[str] = None, + ) -> str: + """Handle an incoming request to /login/sso/redirect + + 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 not client_redirect_url: + # Some SAML identity providers (e.g. Google) require a + # RelayState parameter on requests, so pass in a dummy redirect URL + # (which will never get used). + client_redirect_url = b"unused" + + reqid, info = self._saml_client.prepare_for_authenticate( + entityid=self._saml_idp_entityid, relay_state=client_redirect_url + ) + + # Since SAML sessions timeout it is useful to log when they were created. + logger.info("Initiating a new SAML session: %s" % (reqid,)) + + now = self.clock.time_msec() + self._outstanding_requests_dict[reqid] = Saml2SessionData( + creation_time=now, + ui_auth_session_id=ui_auth_session_id, + ) + + for key, value in info["headers"]: + if key == "Location": + return value + + # this shouldn't happen! + raise Exception("prepare_for_authenticate didn't return a Location header") + + async def handle_saml_response(self, request: SynapseRequest) -> None: + """Handle an incoming request to /_synapse/client/saml2/authn_response + + Args: + request: the incoming request from the browser. We'll + respond to it with a redirect. + + Returns: + Completes once we have handled the request. + """ + resp_bytes = parse_string(request, "SAMLResponse", required=True) + relay_state = parse_string(request, "RelayState", required=True) + + # expire outstanding sessions before parse_authn_request_response checks + # the dict. + self.expire_sessions() + + try: + saml2_auth = self._saml_client.parse_authn_request_response( + resp_bytes, + saml2.BINDING_HTTP_POST, + outstanding=self._outstanding_requests_dict, + ) + except saml2.response.UnsolicitedResponse as e: + # the pysaml2 library helpfully logs an ERROR here, but neglects to log + # the session ID. I don't really want to put the full text of the exception + # in the (user-visible) exception message, so let's log the exception here + # so we can track down the session IDs later. + logger.warning(str(e)) + self._sso_handler.render_error( + request, "unsolicited_response", "Unexpected SAML2 login." + ) + return + except Exception as e: + self._sso_handler.render_error( + request, + "invalid_response", + "Unable to parse SAML2 response: %s." % (e,), + ) + return + + if saml2_auth.not_signed: + self._sso_handler.render_error( + request, "unsigned_respond", "SAML2 response was not signed." + ) + return + + logger.debug("SAML2 response: %s", saml2_auth.origxml) + + await self._handle_authn_response(request, saml2_auth, relay_state) + + async def _handle_authn_response( + self, + request: SynapseRequest, + saml2_auth: saml2.response.AuthnResponse, + relay_state: str, + ) -> None: + """Handle an AuthnResponse, having parsed it from the request params + + Assumes that the signature on the response object has been checked. 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 + saml2_auth: the parsed AuthnResponse object + relay_state: the RelayState query param, which encodes the URI to rediret + back to + """ + + for assertion in saml2_auth.assertions: + # kibana limits the length of a log field, whereas this is all rather + # useful, so split it up. + count = 0 + for part in chunk_seq(str(assertion), 10000): + logger.info( + "SAML2 assertion: %s%s", "(%i)..." % (count,) if count else "", part + ) + count += 1 + + logger.info("SAML2 mapped attributes: %s", saml2_auth.ava) + + current_session = self._outstanding_requests_dict.pop( + saml2_auth.in_response_to, None + ) + + # first check if we're doing a UIA + if current_session and current_session.ui_auth_session_id: + try: + remote_user_id = self._remote_id_from_saml_response(saml2_auth, None) + except MappingException as e: + logger.exception("Failed to extract remote user id from SAML response") + self._sso_handler.render_error(request, "mapping_error", str(e)) + return + + return await self._sso_handler.complete_sso_ui_auth_request( + self.idp_id, + remote_user_id, + current_session.ui_auth_session_id, + 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, saml2_auth.ava, self._saml2_attribute_requirements + ): + return + + # Call the mapper to register/login the user + try: + await self._complete_saml_login(saml2_auth, request, relay_state) + except MappingException as e: + logger.exception("Could not map user") + self._sso_handler.render_error(request, "mapping_error", str(e)) + + async def _complete_saml_login( + self, + saml2_auth: saml2.response.AuthnResponse, + request: SynapseRequest, + client_redirect_url: str, + ) -> None: + """ + Given a SAML 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: + saml2_auth: The parsed SAML2 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. + """ + remote_user_id = self._remote_id_from_saml_response( + saml2_auth, client_redirect_url + ) + + async def saml_response_to_remapped_user_attributes( + failures: int, + ) -> UserAttributes: + """ + Call the mapping provider to map a SAML response to user attributes and coerce the result into the standard form. + + This is backwards compatibility for abstraction for the SSO handler. + """ + # Call the mapping provider. + result = self._user_mapping_provider.saml_response_to_user_attributes( + saml2_auth, failures, client_redirect_url + ) + # Remap some of the results. + return UserAttributes( + localpart=result.get("mxid_localpart"), + display_name=result.get("displayname"), + emails=result.get("emails", []), + ) + + async def grandfather_existing_users() -> Optional[str]: + # backwards-compatibility hack: see if there is an existing user with a + # suitable mapping from the uid + if ( + self._grandfathered_mxid_source_attribute + and self._grandfathered_mxid_source_attribute in saml2_auth.ava + ): + attrval = saml2_auth.ava[self._grandfathered_mxid_source_attribute][0] + user_id = UserID( + map_username_to_mxid_localpart(attrval), self.server_name + ).to_string() + + logger.debug( + "Looking for existing account based on mapped %s %s", + self._grandfathered_mxid_source_attribute, + 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, + remote_user_id, + request, + client_redirect_url, + saml_response_to_remapped_user_attributes, + grandfather_existing_users, + ) + + def _remote_id_from_saml_response( + self, + saml2_auth: saml2.response.AuthnResponse, + client_redirect_url: Optional[str], + ) -> str: + """Extract the unique remote id from a SAML2 AuthnResponse + + Args: + saml2_auth: The parsed SAML2 response. + client_redirect_url: The redirect URL passed in by the client. + Returns: + remote user id + + Raises: + MappingException if there was an error extracting the user id + """ + # It's not obvious why we need to pass in the redirect URI to the mapping + # provider, but we do :/ + remote_user_id = self._user_mapping_provider.get_remote_user_id( + saml2_auth, client_redirect_url + ) + + if not remote_user_id: + raise MappingException( + "Failed to extract remote user id from SAML response" + ) + + return remote_user_id + + def expire_sessions(self): + expire_before = self.clock.time_msec() - self._saml2_session_lifetime + to_expire = set() + for reqid, data in self._outstanding_requests_dict.items(): + if data.creation_time < expire_before: + to_expire.add(reqid) + for reqid in to_expire: + logger.debug("Expiring session id %s", reqid) + del self._outstanding_requests_dict[reqid] + + +DOT_REPLACE_PATTERN = re.compile( + ("[^%s]" % (re.escape("".join(mxid_localpart_allowed_characters)),)) +) + + +def dot_replace_for_mxid(username: str) -> str: + """Replace any characters which are not allowed in Matrix IDs with a dot.""" + username = username.lower() + username = DOT_REPLACE_PATTERN.sub(".", username) + + # regular mxids aren't allowed to start with an underscore either + username = re.sub("^_", "", username) + return username + + +MXID_MAPPER_MAP = { + "hexencode": map_username_to_mxid_localpart, + "dotreplace": dot_replace_for_mxid, +} # type: Dict[str, Callable[[str], str]] + + +@attr.s +class SamlConfig: + mxid_source_attribute = attr.ib() + mxid_mapper = attr.ib() + + +class DefaultSamlMappingProvider: + __version__ = "0.0.1" + + def __init__(self, parsed_config: SamlConfig, module_api: ModuleApi): + """The default SAML user mapping provider + + Args: + parsed_config: Module configuration + module_api: module api proxy + """ + self._mxid_source_attribute = parsed_config.mxid_source_attribute + self._mxid_mapper = parsed_config.mxid_mapper + + self._grandfathered_mxid_source_attribute = ( + module_api._hs.config.saml2_grandfathered_mxid_source_attribute + ) + + def get_remote_user_id( + self, saml_response: saml2.response.AuthnResponse, client_redirect_url: str + ) -> str: + """Extracts the remote user id from the SAML response""" + try: + return saml_response.ava["uid"][0] + except KeyError: + logger.warning("SAML2 response lacks a 'uid' attestation") + raise MappingException("'uid' not in SAML2 response") + + def saml_response_to_user_attributes( + self, + saml_response: saml2.response.AuthnResponse, + failures: int, + client_redirect_url: str, + ) -> dict: + """Maps some text from a SAML response to attributes of a new user + + Args: + saml_response: A SAML auth response object + + failures: How many times a call to this function with this + saml_response has resulted in a failure + + client_redirect_url: where the client wants to redirect to + + Returns: + dict: A dict containing new user attributes. Possible keys: + * mxid_localpart (str): Required. The localpart of the user's mxid + * displayname (str): The displayname of the user + * emails (list[str]): Any emails for the user + """ + try: + mxid_source = saml_response.ava[self._mxid_source_attribute][0] + except KeyError: + logger.warning( + "SAML2 response lacks a '%s' attestation", + self._mxid_source_attribute, + ) + raise SynapseError( + 400, "%s not in SAML2 response" % (self._mxid_source_attribute,) + ) + + # Use the configured mapper for this mxid_source + localpart = self._mxid_mapper(mxid_source) + + # Append suffix integer if last call to this function failed to produce + # a usable mxid. + localpart += str(failures) if failures else "" + + # Retrieve the display name from the saml response + # If displayname is None, the mxid_localpart will be used instead + displayname = saml_response.ava.get("displayName", [None])[0] + + # Retrieve any emails present in the saml response + emails = saml_response.ava.get("email", []) + + return { + "mxid_localpart": localpart, + "displayname": displayname, + "emails": emails, + } + + @staticmethod + def parse_config(config: dict) -> SamlConfig: + """Parse the dict provided by the homeserver's config + Args: + config: A dictionary containing configuration options for this provider + Returns: + SamlConfig: A custom config object for this module + """ + # Parse config options and use defaults where necessary + mxid_source_attribute = config.get("mxid_source_attribute", "uid") + mapping_type = config.get("mxid_mapping", "hexencode") + + # Retrieve the associating mapping function + try: + mxid_mapper = MXID_MAPPER_MAP[mapping_type] + except KeyError: + raise ConfigError( + "saml2_config.user_mapping_provider.config: '%s' is not a valid " + "mxid_mapping value" % (mapping_type,) + ) + + return SamlConfig(mxid_source_attribute, mxid_mapper) + + @staticmethod + def get_saml_attributes(config: SamlConfig) -> Tuple[Set[str], Set[str]]: + """Returns the required attributes of a SAML + + Args: + config: A SamlConfig object containing configuration params for this provider + + Returns: + 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 + available, but are not necessary + """ + return {"uid", config.mxid_source_attribute}, {"displayName", "email"} |