mirror of
https://mau.dev/maunium/synapse.git
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e1b8e37f93
This is another part of my work towards fixing #8876. It moves some of the logic currently in the SAML and OIDC handlers - in particular the call to `AuthHandler.complete_sso_login` down into the `SsoHandler`.
329 lines
13 KiB
Python
329 lines
13 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.http.site import SynapseRequest
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from synapse.types import JsonDict, UserID, contains_invalid_mxid_characters
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from synapse.util.async_helpers import Linearizer
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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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# a lock on the mappings
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self._mapping_lock = Linearizer(name="sso_user_mapping", clock=hs.get_clock())
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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 complete_sso_login_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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request: SynapseRequest,
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client_redirect_url: 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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extra_login_attributes: Optional[JsonDict] = None,
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) -> None:
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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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Finally, we generate a redirect to the supplied redirect uri, with a login token
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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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request: The request to respond to
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client_redirect_url: The redirect URL passed in by the client.
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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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extra_login_attributes: An optional dictionary of extra
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attributes to be provided to the client in the login 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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# grab a lock while we try to find a mapping for this user. This seems...
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# optimistic, especially for implementations that end up redirecting to
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# interstitial pages.
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with await self._mapping_lock.queue(auth_provider_id):
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# first of all, check if we already have a mapping for this user
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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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# Check for grandfathering of users.
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if not user_id and grandfather_existing_users:
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user_id = await grandfather_existing_users()
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if 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, user_id
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)
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# Otherwise, generate a new user.
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if not user_id:
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attributes = await self._call_attribute_mapper(sso_to_matrix_id_mapper)
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user_id = await self._register_mapped_user(
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attributes,
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auth_provider_id,
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remote_user_id,
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request.get_user_agent(""),
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request.getClientIP(),
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)
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await self._auth_handler.complete_sso_login(
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user_id, request, client_redirect_url, extra_login_attributes
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)
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async def _call_attribute_mapper(
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self, sso_to_matrix_id_mapper: Callable[[int], Awaitable[UserAttributes]],
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) -> UserAttributes:
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"""Call the attribute mapper function in a loop, until we get a unique userid"""
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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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return attributes
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async def _register_mapped_user(
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self,
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attributes: UserAttributes,
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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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) -> str:
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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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