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36ba73f53d
* SsoHandler: remove inheritance from BaseHandler * Simplify the flow for SSO UIA We don't need to do all the magic for mapping users when we are doing UIA, so let's factor that out.
288 lines
11 KiB
Python
288 lines
11 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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from typing import TYPE_CHECKING, Awaitable, Callable, List, Optional
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import attr
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from twisted.web.http import Request
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from synapse.api.errors import RedirectException
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from synapse.http.server import respond_with_html
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from synapse.types import UserID, contains_invalid_mxid_characters
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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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class MappingException(Exception):
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"""Used to catch errors when mapping an SSO response to user attributes.
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Note that the msg that is raised is shown to end-users.
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"""
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@attr.s
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class UserAttributes:
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localpart = attr.ib(type=str)
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display_name = attr.ib(type=Optional[str], default=None)
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emails = attr.ib(type=List[str], default=attr.Factory(list))
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class SsoHandler:
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# The number of attempts to ask the mapping provider for when generating an MXID.
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_MAP_USERNAME_RETRIES = 1000
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def __init__(self, hs: "HomeServer"):
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self._store = hs.get_datastore()
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self._server_name = hs.hostname
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self._registration_handler = hs.get_registration_handler()
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self._error_template = hs.config.sso_error_template
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self._auth_handler = hs.get_auth_handler()
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def render_error(
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self, request, error: str, error_description: Optional[str] = None
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) -> None:
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"""Renders the error template and responds with it.
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This is used to show errors to the user. The template of this page can
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be found under `synapse/res/templates/sso_error.html`.
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Args:
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request: The incoming request from the browser.
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We'll respond with an HTML page describing the error.
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error: A technical identifier for this error.
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error_description: A human-readable description of the error.
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"""
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html = self._error_template.render(
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error=error, error_description=error_description
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)
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respond_with_html(request, 400, html)
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async def get_sso_user_by_remote_user_id(
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self, auth_provider_id: str, remote_user_id: str
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) -> Optional[str]:
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"""
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Maps the user ID of a remote IdP to a mxid for a previously seen user.
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If the user has not been seen yet, this will return None.
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Args:
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auth_provider_id: A unique identifier for this SSO provider, e.g.
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"oidc" or "saml".
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remote_user_id: The user ID according to the remote IdP. This might
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be an e-mail address, a GUID, or some other form. It must be
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unique and immutable.
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Returns:
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The mxid of a previously seen user.
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"""
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logger.debug(
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"Looking for existing mapping for user %s:%s",
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auth_provider_id,
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remote_user_id,
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)
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# Check if we already have a mapping for this user.
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previously_registered_user_id = await self._store.get_user_by_external_id(
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auth_provider_id, remote_user_id,
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)
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# A match was found, return the user ID.
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if previously_registered_user_id is not None:
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logger.info(
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"Found existing mapping for IdP '%s' and remote_user_id '%s': %s",
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auth_provider_id,
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remote_user_id,
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previously_registered_user_id,
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)
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return previously_registered_user_id
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# No match.
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return None
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async def get_mxid_from_sso(
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self,
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auth_provider_id: str,
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remote_user_id: str,
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user_agent: str,
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ip_address: str,
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sso_to_matrix_id_mapper: Callable[[int], Awaitable[UserAttributes]],
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grandfather_existing_users: Optional[Callable[[], Awaitable[Optional[str]]]],
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) -> str:
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"""
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Given an SSO ID, retrieve the user ID for it and possibly register the user.
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This first checks if the SSO ID has previously been linked to a matrix ID,
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if it has that matrix ID is returned regardless of the current mapping
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logic.
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If a callable is provided for grandfathering users, it is called and can
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potentially return a matrix ID to use. If it does, the SSO ID is linked to
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this matrix ID for subsequent calls.
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The mapping function is called (potentially multiple times) to generate
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a localpart for the user.
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If an unused localpart is generated, the user is registered from the
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given user-agent and IP address and the SSO ID is linked to this matrix
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ID for subsequent calls.
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Args:
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auth_provider_id: A unique identifier for this SSO provider, e.g.
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"oidc" or "saml".
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remote_user_id: The unique identifier from the SSO provider.
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user_agent: The user agent of the client making the request.
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ip_address: The IP address of the client making the request.
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sso_to_matrix_id_mapper: A callable to generate the user attributes.
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The only parameter is an integer which represents the amount of
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times the returned mxid localpart mapping has failed.
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It is expected that the mapper can raise two exceptions, which
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will get passed through to the caller:
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MappingException if there was a problem mapping the response
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to the user.
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RedirectException to redirect to an additional page (e.g.
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to prompt the user for more information).
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grandfather_existing_users: A callable which can return an previously
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existing matrix ID. The SSO ID is then linked to the returned
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matrix ID.
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Returns:
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The user ID associated with the SSO response.
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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: if the mapping provider needs to redirect the user
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to an additional page. (e.g. to prompt for more information)
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"""
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# first of all, check if we already have a mapping for this user
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previously_registered_user_id = await self.get_sso_user_by_remote_user_id(
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auth_provider_id, remote_user_id,
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)
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if previously_registered_user_id:
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return previously_registered_user_id
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# Check for grandfathering of users.
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if grandfather_existing_users:
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previously_registered_user_id = await grandfather_existing_users()
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if previously_registered_user_id:
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# Future logins should also match this user ID.
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await self._store.record_user_external_id(
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auth_provider_id, remote_user_id, previously_registered_user_id
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)
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return previously_registered_user_id
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# Otherwise, generate a new user.
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for i in range(self._MAP_USERNAME_RETRIES):
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try:
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attributes = await sso_to_matrix_id_mapper(i)
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except (RedirectException, MappingException):
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# Mapping providers are allowed to issue a redirect (e.g. to ask
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# the user for more information) and can issue a mapping exception
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# if a name cannot be generated.
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raise
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except Exception as e:
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# Any other exception is unexpected.
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raise MappingException(
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"Could not extract user attributes from SSO response."
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) from e
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logger.debug(
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"Retrieved user attributes from user mapping provider: %r (attempt %d)",
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attributes,
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i,
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)
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if not attributes.localpart:
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raise MappingException(
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"Error parsing SSO response: SSO mapping provider plugin "
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"did not return a localpart value"
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)
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# Check if this mxid already exists
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user_id = UserID(attributes.localpart, self._server_name).to_string()
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if not await self._store.get_users_by_id_case_insensitive(user_id):
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# This mxid is free
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break
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else:
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# Unable to generate a username in 1000 iterations
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# Break and return error to the user
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raise MappingException(
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"Unable to generate a Matrix ID from the SSO response"
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)
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# Since the localpart is provided via a potentially untrusted module,
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# ensure the MXID is valid before registering.
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if contains_invalid_mxid_characters(attributes.localpart):
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raise MappingException("localpart is invalid: %s" % (attributes.localpart,))
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logger.debug("Mapped SSO user to local part %s", attributes.localpart)
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registered_user_id = await self._registration_handler.register_user(
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localpart=attributes.localpart,
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default_display_name=attributes.display_name,
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bind_emails=attributes.emails,
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user_agent_ips=[(user_agent, ip_address)],
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)
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await self._store.record_user_external_id(
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auth_provider_id, remote_user_id, registered_user_id
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)
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return registered_user_id
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async def complete_sso_ui_auth_request(
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self,
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auth_provider_id: str,
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remote_user_id: str,
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ui_auth_session_id: str,
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request: Request,
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) -> None:
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"""
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Given an SSO ID, retrieve the user ID for it and complete UIA.
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Note that this requires that the user is mapped in the "user_external_ids"
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table. This will be the case if they have ever logged in via SAML or OIDC in
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recentish synapse versions, but may not be for older users.
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Args:
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auth_provider_id: A unique identifier for this SSO provider, e.g.
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"oidc" or "saml".
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remote_user_id: The unique identifier from the SSO provider.
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ui_auth_session_id: The ID of the user-interactive auth session.
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request: The request to complete.
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"""
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user_id = await self.get_sso_user_by_remote_user_id(
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auth_provider_id, remote_user_id,
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)
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if not user_id:
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logger.warning(
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"Remote user %s/%s has not previously logged in here: UIA will fail",
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auth_provider_id,
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remote_user_id,
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)
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# Let the UIA flow handle this the same as if they presented creds for a
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# different user.
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user_id = ""
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await self._auth_handler.complete_sso_ui_auth(
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user_id, ui_auth_session_id, request
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)
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